WO2012103309A2 - Polymeric systems containing chromophoric units for photo-driven catalysis and water splitting - Google Patents

Abstract

A polymer (e.g., a photocatalytic polymer) that contains chromophoric units therein (e.g., covalently coupled therein, in the polymer backbones and/or side chains), is described. In some embodiments, the polymer comprises: (a) a first ligand as a first repeating monomeric unit therein (e.g., as part of the polymer backbones and/or side chains); (b) a transition metal (e.g., Ru, Ir, Fe, Co, etc.) complexed with said first ligand to form a chromophoric unit or transition metal photocatalyst therewith; and (c) optionally but preferably at least one additional ligand (e.g., one or two) complexed with said transition metal to form said chromophoric unit or transition metal photocatalyst; and (d) optionally but preferably a second monomeric unit copolymerized with said first monomeric unit. Compositions containing the same and methods of using the same are also described.

Description

POLYMERIC SYSTEMS CONTAINING CHROMOPHORIC UNITS FOR PHOTO- DRIVEN CATALYSIS AND WATER SPLITTING

Wenbin Lin, Zhigang Xie, and Cheng Wang

This invention was made with government support under grant number DE- SC0001011 from the Department of Energy. The US Government has certain rights to this invention.

Background of the Invention

Organic transformations driven by visible light are gaining increasing interest from synthetic chemists, because of generally mild conditions for substrate activation, the ability to afford desired products without generating unwanted byproducts, and the potential to mediate thermodynamically uphill reactions by harvesting energy from the sunlight in these reactions.¹ Photocatalysts are often required in visible light driven organic reactions since the majority of organic substrates in these reactions do not readily absorb photons in the visible region. [ u(bpy) ]²⁺ (bpy = 2,2'-bipyridine) is undoubtedly one of the most extensively studied photocatalysts since the pioneering work of Meyer and Whitten in the 1970s. By taking advantage of the long lifetime of the MLCT state of this Ru-based phosphor and its propensity to undergo redox quenching, a variety of new photocatalytic organic reactions, ranging from [2+2] cycloaddition to radical chemistry, have been developed recently.³ Stephenson et al and MacMillan et al also reported the use of an Ir complex, Ir(ppy)₂(dtbbpy)PF₆ (ppy = 2-phenylpyridine; dtbbpy =4,4'-di-ter/-butyl-2,2'-bipyridine), as a photoredox catalyst in tin-free dehalogenation, Aza-Henry reactions, and a- trifluoromethylation of aldehydes.⁴ Like other precious metal catalyzed reactions, it is highly desirable to develop recyclable and reusable heterogeneous photocatalytic systems based on the Ir and Ru phosphors as well as other transition metal photosensitizers. The ability to recover and reuse such heterogeneous photocatalysts can not only eliminate the contamination of organic products by trace amounts of heavy metals but also reduce processing and waste disposal costs in large scale reactions. Summary of the Invention

A first aspect of the invention is a polymer (e.g., a photocatalytic polymer) that contains chromophoric units therein (e.g., covalently coupled therein, in the polymer backbones and/or side chains). In some embodiments, the polymer comprises: (a) a first ligand as a first repeating monomelic unit therein (e.g., as part of the polymer backbones and/or side chains); (b) a transition metal (e.g., Ru, Ir, Fe, Co, etc.) complexed with said first ligand to form a chromophoric unit or transition metal photocatalyst therewith; and (c) optionally but preferably at least one additional ligand (e.g., one or two) complexed with said transition metal to form said chromophoric unit or transition metal photocatalyst; and (d) optionally but preferably a second monomelic unit copolymerized with said first monomelic unit.

In some embodiments, the first monomelic unit comprises a compound of the formula A'BCD', wherein A' and D' are (depending upon the particular polymerization reaction employed) covalent bonds or independently selected linking groups (e.g., a ethenyl, ethynyl, halo, carboxyl, amide, etc.), and B and C are independently selected coordinating groups (e.g., heteroalkyl, heteroaryl) conjugated to said transition metal.

A further aspect of the invention is a polymer as described herein for use as a photocatalyst.

A further aspect of the invention is a method of making a polymer, particularly a photocatalytic polymer, comprising: reacting a first monomer with a second monomer; wherein: said first monomer comprises a compound of the formula ABCD, wherein A and D are independently selected reactive groups (e.g., ethenyl, ethynyl, halo, amino, carboxy), and B and C are independently selected coordinating groups (e.g., heteroalkyl, heteroaryl); and said second monomer comprises a compound the formula X(YZ)_n, wherein X is an organic or silyl group (e.g., carbon, Si, phenyl, te/ -butyl), Y is an organic group (preferably aryl, particularly phenyl), Z is a reactive group (e.g., ethenyl, ethynyl, halo, amino, carboxy), and n is 3 or 4.

A further aspect of the present invention is a polymer produced by a process as described herein.

A further aspect of the invention is a method of carrying out a photocatalytic reaction by contacting one or more substrates to a photocatalyst and exposing said photocatalyst to light to produce one or more products. The method is characterized by the improvement comprising employing a polymer or catalyst system of any preceding claim as said photocatalyst.

The present invention is explained in greater detail in the drawings herein and the specification set forth below. The disclosures of all United States patents cited herein are to be incorporated by reference herein in their entirety.

Brief Description of the Drawings

Figure 1. Characterization of Ir-PCP and Ru-PCP: a) SEM and b) TEM images of the Ir-PCP. The scale bars represent 200 nm. c) TGA, d) FT-IR, e) Nitrogen adsorption isotherms at 77K, and f) uncorrected emission spectra. The Ir-PCP emission spectrum (red line) was taken when excited at 380 nm. The broad emission at around 458.5 nm comes from fluorescence of the framework. The Ru-PCP emission spectrum (blue line) was taken when excited at 450 nm. The broad emission at around 522.5 nm comes from fluorescence of the framework.

Figure 2. Powder X-ray diffraction (PXRD) of Ir-PCP and Ru-PCP. The low intensity broad peaks indicate the amorphous nature of the PCPs.

Figure 3. Pore size distribution of Ir-PCP and Ru-PCP calculated by density functional theory (DFT).

Figure 4. Cumulative pore volume of Ir-PCP and Ru-PCP calculated by DFT.

Figure 5. Idealized structure of the Ir-PCP.

Figure 6. Stern- Volmer plot of Ru-PCP quenching by la, compared to that of the homogeneous monomer [(bpy)2Ru(debpy)]C12. Stern-volmer constant for Ru-PCP is 23 M^"1, and 20 M^"1 for [(bpy)₂Ru(debpy)]Cl₂.

Figure 7. For entry 1 and 2, the peak at 5.48 ppm of the product and the peak at 4.39 ppm of the substrate in the 1H NMR were used to calculate the conversions.

Figure 8. For entry 3, 4, the peak at 5.53 ppm of the product and peak at 4.42 ppm of the substrate in the 1H NMR were used to calculate the conversions.

Figure 9. For entry 5 and 6, the peaks at 5.24 and 4.43 ppm of the product and peak at 3.50 ppm of the substrate in the ^!Η NMR were used to calculate the conversions.

Figure 10. For entry 7 and 8, the peaks at 5.24 and 4.42 ppm of the product and peak at 3.50 ppm of the substrate in the 1H NMR were used to calculate the conversions.

Figure 11 provides a thermogravimetric analysis (TGA) of Ru-COF.

Figure 12 provides an emission spectra (excitation wavelength is 450nm. Figure 13 provides SEM (scanning electron micrograph) photographs.

Figure 14 provides an FT-IR spectra.

Figure 15 provides a BET plot.

Figure 16. FT-IR spectra of Ru-1, Ru-2, 1, and 2.

Figure 17. Nitrogen sorption isotherms of 1 and 2 in at 77 K.

Figure 18. TEM images of 1 (a) and 2 (b) on a carbon-coated Cu/Ni grid.

Figure 19. Steady-state absorption spectra of stirred suspensions of 1 and 2 in CH₃CN (0.74 mg/50 mL) and dilute solutions of Ru-1 and Ru-2 in CH₃CN (2x l0^"5 M). Absorption spectra of Ru-1 and Ru-2 are on a reduced scale (x 0.2).

Figure 20. Steady-state phosphorescence spectra of stirred suspensions of 1 and 2 in C¾CN (0.74 mg/50 mL) and dilute solutions of Ru-1 and Ru-2 in CH₃CN (2^χ 10^-5 M).

Figure 21. Time-resolved phosphorescence decays of 1 and 2 and monomers Ru-1 a nd Ru-2 (excitation: 440 nm; emission: 660 nm).

Detailed Description of Embodiments of the Invention

"Light" as used herein refers to ambient or directed light as well as light from natural or artificial sources. Light of any suitable wavelength may be used, with light in the visible spectra in some embodiments preferred.

"Reactive group" as used herein may be any suitable reactive group, depending upon the particular coupling or polymerization reaction used. Examples include, but are not limited to, carboxy, carboxylic acid including activated carboxylic acid, hydroxy, epoxy, halo, amino, substituted amino, epoxy, isocyanate, sulfonyl, and sulfonate groups; triflate, boronic acid, B(OH)₂, tin or organotin, zinc or zinc halide, and aldehyde, MgBr, - (trialkoxysilyl)propylamine, omega-(trialkoxysilyl)alkyl bromomethylacetamide, thiol, etc. See, e.g., US Patent Nos. 4,293,476; 4,555,546; and 7,173,102.

"Solvent" herein may be any suitable aqueous or organic solvent (including mixtures thereof), including but not limited to (a) non-polar solvents such as pentane, cyclopentane, hexane, cyclohexane, benzene, toluene, 1,4-dioxane, chloroform, diethyl ether, etc., (b) polar aprotic solvents such as dichloromethane, tetrahydrofuran, ethyl acetate, acetone, dimethylformaniide, acetonitrile, dimethyl sulfoxide, etc., and (c) polar protic solvents such as formic acid, n-butanol, isopropanol, n-propanol, ethanol, methanol, acetic acid, water, etc., and combinations of all of the foregoing. Aqueous solvents can be neutral, basic, or acidic aqueous solvents. "Transition metal" as used herein includes, but is not limited to, Ru, Ir, Fe, Co, Cu, Ti, Pt, Ir, Rh, Ag, Ni, etc.

1. Monomers.

A variety of different monomers can be used to carry out the present invention. In general, the first monomer comprises a compound of the formula ABCD, wherein A and D are independently selected reactive groups (e.g., ethenyl, ethynyl, halo, amino, carboxy), and B and C are independently selected coordinating groups (e.g., heteroalkyl, heteroaryl).

In some embodiments of the reaction, said first monomer is a ligand complexed with a transition metal (e.g., Ru, Ir, Fe, or Co) to form a transition metal photocatalyst therewith, and with at least one (e.g., one or two) additional ligand optionally complexed with said transition metal to form said transition metal photocatalyst.

In some embodiments, the second monomer comprises a compound the formula X(YZ)„, . wherein X is an organic or silyl group (e.g., carbon, Si, phenyl, ferf-butyl), Y is an organic group (preferably aryl, particularly phenyl), Z is a reactive group (e.g., ethenyl, ethynyl, halo, amino, carboxy), and n is 3 or 4.

Any suitable ligand system can be used in the monomers. Particular examples are bipyridine or phenylpyridine, but other ligand systems such as porphyrin systems can also be used.

Non-limiting examples of suitable monomers for carrying out the present invention include:

Additional non-limiting examples of suitable monomers for carrying out the present invention include any of the foregoing illustrated structures, where (a) the specific reactive groups shown (NH₂, C0₂H, ethynyl, bromo, and B(OH)₂) are replaced by any of the other reactive groups noted hereinabove; (b) the specific aryl groups shown are replaced by different aryl groups (e.g., one or two additional hetero atoms such as oxygen, nitrogen or sulfur are substituted in the ring, and/or a carbon or hetero atom is deleted to form a corresponding five member ring, etc.), (c) a "spacer" group such a C1-C2 alkylene is inserted between rings systems (e.g., between two phenyls, two pyridines, or a phenyl oand a pyridine), or between a ring system and a reactive group, (d) any of the aforesaid rings shown are optionally substituted (e.g. one, two or three times with independently selected C1-C4 loweralkyl, C1 -C4 loweralkoxy, etc), (f) one or two additional ring systems are covalently coupled to any of the foregoing to provide a ligand with 3 or 4 coordinating atoms, and/or (g) additional rings are fused to any of the aforesaid rings shown, etc. All of the aforesaid variations are for purposes of illustration, and not for limitation.

2. Polymers.

In general, polymerization of monomers can be carried out by any suitable polymerization or coupling reaction. Examples include, but are not limited to: Negishi coupling reaction, a Heck coupling reaction, a Suzuki coupling reaction, a Hiyama coupling reaction, a Sonogashira coupling reaction, a Stille coupling reaction, a Kumada coupling reaction, a Buchwald-Hartwig amination reaction, an allyl substitution reaction, an enolate arylation reaction, a hydroformylation reaction, a carbonylation reaction, a hydrosilylation reaction or a boronylation reaction. See, e.g., US Patent No. 7250510. Additional more particular examples include, but are not limited to, Suzuki-Miyaura, Murahashi, Kumada- Corriu, Kumada-Tamao, Nozaki, Nozaki-Oshima, Negishi, Tamao-Kumada, Hiyama- Hatanaka, Migita-Kosugi, Buchwald-Hartwig, Murahashi, Cyanation, dehydrohalogenation, . alpha. -"Carbonyl" Arylation, Cadiot-Chodkiewicz, catalytic ether formation, catalytic . alpha. -arylations of ketones, dehalogenation, and catalytic thioether formation reactions, etc. See, e.g., US Patent No. 7,442,800.

Thus, as noted above, the present invention provides a polymer (e.g., a photocatalytic polymer) that contains clu'omophoric units therein (e.g., covalently coupled therein, in the polymer backbones and/or side chains). In some embodiments, the polymer comprises: (a) a first ligand as a first repeating monomelic unit therein (e.g., as part of the polymer backbones and/or side chains); (b) a transition metal (e.g., Ru, Ir, Fe, Co, etc.) complexed with said first ligand to form a chromophoric unit or transition metal photocatalyst therewith; and (c) optionally but preferably at least one additional ligand (e.g., one or two) complexed with said transition metal to form said chromophoric unit or transition metal photocatalyst; and (d) optionally but preferably a second monomeric unit copolymerized with said first monomelic unit.

In some embodiments, the first monomeric unit comprises a compound of the formula A'BCD', wherein A' and D' are (depending upon the particular polymerization reaction employed) covalent bonds or independently selected linking groups (e.g., a ethenyl, ethynyl, halo, carboxyl, amide, etc.), and B and C are independently selected coordinating groups (e.g., heteroalkyl, heteroaryl) conjugated to said transition metal.

In some embodiments, the second monomeric unit comprises a compound of the formula X(Y-)_n, wherein X is an organic or silyl group (e.g., carbon, Si, phenyl, fer/-butyl), Y is an organic group (preferably aryl, particularly phenyl), and n is 3 or 4.

In some embodiments, the polymer is a porous crosslinked polymer. Porous crosslinked polymers (PCPs), including crystalline covalent-organic frameworks, can be built from well-designed organic precursors and represent a new class of robust, nanoporous materials.⁵ Like their porous metal-organic framework (MOF) counterparts,⁶ PCPs have shown great promise in gas storage and separation and light harvesting.⁷ Just like recently developed catalytic MOFs,⁸ PCPs can serve as an ideal platform for incorporating molecular catalytic modules into highly stable, recyclable, and reusable heterogeneous catalyst systems by taking advantage of their permanent porosity and the ability to tune their compositions and properties at the molecular level.⁹ PCPs are advantageous over MOFs as photocatalysts since many MOFs are constructed from metal connecting points with unfilled d orbitals which can readily quench the photoexcited states of the photocatalytic building units.¹⁰ Other polymeric systems containing chromophoric units in the polymer backbones and/or side chains can also be used for the photocatalytic reactions.

In some embodiments, the polymer is thermally stable at 300 or 350 °C in air at atmospheric pressure for one or two hours.

In some embodiments, the polymer has (a) an average poor diameter between 1 or 2 and 45 or 50 Angstroms; and/or (b) an average cumulative pore volume (cmVg) of from 0.01 or 0.1 to 0.9 or 1.

In some embodiments, the polymer has a weight average molecular weight of at least 100, 500, 1 ,000, or 5,000 daltons.

In some embodiments, the polymer has a weight average molecular weight of not more than 10,000, 50,000, 100,000, or 500,000 daltons. Particular non-limiting examples of polymers of the invention include, but are not limited to:

octacarbonyldicobalt (Co₂(CO)₈)-catalyzed alkyne trimerization reaction products, such as:

u-COF: M(Xpy)₂ = Ru(bpy)₂

Ir-COF: M(Xpy)₂ = lr(ppy)₂

Sonagashira coupling reaction products, such as:

1 1 R= Ru(bpy)₂ or lr(ppy)₂ I

3. Catalyst systems and methods of use.

In some embodiments, the polymers of the present invention are combined with a solvent in which the polymer is insoluble to provide a heterogeneous catalyst system. In general, such a catalyst system can comprise (a) 0.1 or 1 percent to 80 or 90 percent by weight of a polymer as described herein (generally, in solid insoluble form, such as a particulate form), in combination with (b) from 10 or 20 to 99 or 99.9 percent by weight of a solvent {e.g., in the form of a liquid, gas, or supercritical fluid) (note in some embodiments, the solvent itself may also be a reactant).

A further aspect of the invention is a method of carrying out a photocatalytic reaction by contacting one or more substrates to a photocatalyst and exposing said photocatalyst to light to produce one or more products. The method is characterized by the improvement comprising employing a polymer or catalyst system of any preceding claim as said photocatalyst. Such methods may be carried out in accordance with known techniques, utilizing the catalysts and systems described herein, or variations thereof that will be apparent to those skilled in the art. Examples of reactions that can be carried out include, but are not limited to: water splitting, reduction of carbon dioxide to form methanol, methane, or carbon monoxide; enone cycloaddition reaction, an enentioselective alpha-trifluoromethylation of an aldehyde reaction, an enantioselective alpha-benzylation of an aldehyde reaction, a dehalogenation reaction, an aza-henry reaction, a radical addition to an indole reaction, a C-H functionalization of a heterocycle with a malonate, an alpha oxymination, an oxyamination of an enamine and andehyde, an oxidative coupling of an amine, an oxidation of an alcohol, and hydrogen evolution.

In some embodiments, the catalyst is advantageously recycled. In some embodiments, the method thus further comprises the steps of: separating said polymer from the product of said reaction (e.g., by first separating the polymer from the solvent), and then recycling said polymer in a subsequent reaction (e.g., by recombining said polymer with either fresh solvent, or the same solvent from which said product has been removed).

Specific examples of reactions that can be catalyzed by the catalysts and catalyst systems of the present invention include, but are not limited to, the following:

[2+2]Enone cycloaditions

[3+2]Enone cycloaditions

JACS 2008, 130, 12886- 12887

JACS 2009, 131 , 14604- 14605

JACS 2010, 132, 8572-8574

JACS 201 1 , 133, ASAP DOI: 10.1021 /ja107849y

Enantioselecitive a-trifluoromethylation of aldeheydes

Enantioselecitive a-Benzylation of aldeheydes

JACS 2009, 13 1 , 10875- 10877

JACS 2010, 132, 13600-13603

Science 2008, 322, 77-80

Dehalogenation reaction

Corey R. J. Stephenson

JACS 2009, 131 , 8756-8757

Oxyamination of enamines and aldehyde with TEMPO

Chemistry Letters 38, 2009, 166-167

Oxidative coupling of amine

visible light

Angew chem.. Int. Ed. 201 1, 50, 657-660

Oxidation of alcohol

visible light

JACS 2010, 46, 16300-16301

Hydrogen evolution

photocatalyst

SR + H⁺ (aq) SR⁺ + H₂

cocatalyst

visible light

JACS 2005, 127, 7502-7510

Angew. Chem.. Int. Ed. 2009, 48, 1-5

The present invention is explained in greater detail in the following non-limiting Examples.

EXAMPLE 1

Porous Crosslinked Polymers Prepared by Alkyne Trimerization

In this example, we describe the incorporation of the u and Ir phosphors into PCPs by cobalt carbonyl-mediated trimerization of the end alkyne groups on the monomers.¹¹ The resulting PCPs are active in catalyzing visible light-driven Aza-Henry reactions between nitromethane or nitroethane and tertiary aromatic amines, a-arylation of bromomalonate via intermolecular C-H functionalization, and oxyamination of an aldehyde with 2,2,6,6- tetramethylpiperidinyl- 1 -oxy (TEMPO). The PCP photocatalysts can be recycled and reused for the Aza-Henry reactions without a decrease in catalytic efficiency.

Phosphorescent Ir monomer [(ppy)₂Ir(debpy)]Cl (debpy =5,5'-diethynyl-2,2'- bipyridine) and Ru monomer [(bpy)₂Ru(debpy)]Cl₂ were synthesized by allowing debpy to react with [Ir(ppy)₂Cl₂]₂ and Ru(bpy)₂Cl₂ at 90 °C overnight, respectively. Co-polymerization of the monomer [(ppy)₂Ir(debpy)]Cl or [(bpy)₂Ru(debpy)]Cl₂ with tetra(4- ethynylphenyl)methane was achieved through Co₂(CO)8-mediated trimerization of the end alkyne groups of the monomers in dioxane or dichloroethane at 1 15 °C for 10 min (Scheme 1). The resulting brown solids were stirred in concentrated hydrochloric acid at r.t. for 2 h to remove all the Co species, and then washed with various solvents to afford Ir-PCP and Ru- PCP in 97 % yields. The Ir- and Ru-PCPs were characterized by thermogravimetric analysis (TGA), inductively coupled plasma-mass spectrometry (ICP-MS), infrared spectroscopy (IR), nitrogen adsorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and powder X-ray diffraction PXRD).

Ir-PCP: M(Xpy)₂ = lr(ppy)₂

ppy ₂ r e py

Scheme 1. Synthesis of Ir-PCP and Ru-PCP.

Morphology of the PCPs was examined by SEM and TEM (Figure la, lb). Particles order of several micrometers in size displayed rather rough surfaces, and appear to be aggregates of much smaller particles with dimensions of around 10 nm. The PXRD patterns indicated that the Ir-PCP and Ru-PCP are amorphous in nature (Figure 2).

The Ir-PCP and Ru-PCP are insoluble in water, concentrated acids, and all of the organic solvents tested. The PCPs are stable in air up to 350 °C as revealed by TGA (Figure lc). The Ir and Ru catalyst loadings for Ir-PCP and Ru-PCP were determined by ICP-MS to be 4.5 wt % and 2.2 wt %, respectively. The absence of the carbon-hydrogen stretching peak of the C≡C-H group around 3300 cm^"1 in the IR spectra of the Ir-PCP and Ru-PCP suggested that most of the alkyne groups in the starting materials have been consumed to form benzene rings in the PCPs, consistent with a high degree of polymerization (Figure Id).

Porosity of the PCPs was revealed by nitrogen sorption measurements at 77 K. The PCPs exhibit large reversible adsorptions at low pressure (P/P₀<0.1) and hysteresis loops at higher pressure, suggesting the coexistence of micro- and meso-pores in the framework

13 2 2

(Figure le). The BET surface areas were determined to be 1547 m /g and 1348 m /g for Ir- PCP and Ru-PCP in the P/Po=0.03-0.2 range, respectively. Both of the PCPs have wide pore size distributions with the pore widths centering around 7.5, 11.0, 13.5 and 16,5 A as calculated by the nonlocal density functional theory method (NLDFT) (Figure 3).

With the Ir/Ru based phosphors covalently integrated into the skeletons, we hypothesized that the synthesized PCPs can act as solid state photosensitizers by utilizing the ³MLCT states of the Ir/Ru complexes. Phosphorescence measurements were performed on a stirred suspension of the PCPs in CH3NO2, showing peaks originating from ³MLCT - GS transitions, around 550 nm for the Ir-PCP, and 602 nm for the Ru-PCP (Figure If). We intended to explore the utility of the Ir-PCP and Ru-PCP in catalyzing visible light driven organic reactions such as the Aza-Henry reaction between nitromethane or nitroethane and aromatic tertiary amines. Before the catalysis test of the materials, a preliminary quenching experiment was carried out to confirm that the ³MLCT state of the phosphors in the PCPs can be reductively quenched by the amine substrate, which is the very first step of the photocatalytic cycle of homogeneous Aza-Henry reactions as proposed by Stephenson and co-wor kers.^4b A Stern-Volmer plot for the Ru-PCP was obtained by plotting the intensity ratio Io/I at 602 nm vs the amine concentration, leading to a Stern-Volmer constant of 23 M^"1 which is comparable to that of the monomelic [(bpy)₂Ru(debpy)]Cl₂ complex (20 M^"1). This result indicates effective quenching of the ³MLCT phosphorescence of the Ru-PCP by the amine. In the case of Ir-PCP, the quenching effect was also observed but could not be quantified spectroscopically owing to the interference of the framework fluorescence (Figure If). The quenching result suggested that good photocatalytic performance of the PCPs should be expected.

Catalytic activities of the Ir-PCP and Ru-PCP toward photocatalytic Aza-Henry reaction were evaluated with tetrahydroisoquinoline (la) as the amine substrate and CH N0₂ as solvent. The reaction was carried out in the presence of air with a common fluorescent lamp (26 W) as the light source. The reaction was stopped after 8 hours by filtering off the PCP catalysts. Conversions of the reactions were determined by integrating the peaks of Ή NMR spectra of the crude reaction mixtures (supporting information). As shown in Table 1 (entry 1), both the Ir- and Ru-PCPs are highly effective photocatalysts for the Aza-Henry reaction between la and nitromethane with >90% conversions. These conversions are comparable to those of the homogeneous counterparts. We have also explored the scope of substrates for this photocatalytic reaction (Table 1). The Ir- and Ru-PCPs catalyzed Aza- Henry reactions between nitromethane and a variety of tertiary aromatic amines with different functional groups (Table 1, Entry 1-4).

Table 1. Photocatalytic Aza-Henry reactions³

6b: R-, H, R₂=Br, R₃= CH₃

7b: Ri H, R₂~ OCH3, R3~ CH3

8b: R< OCH3, R₂~ H₍ R₃ ⁼ CH3 amine product conv. (%) with different catalysts

substrate Ir-M Ir- Ru-M Ru-PCP

PCP

1 la lb 99 94 85 90

2 2a 2b 99 97 84 87

3 3a 3b 81 91 90 >99

4 4a 4b 79 98 65 85

5 la 5b 94 94 81 84

6 2a 6b 73 75 57 78

7 3a 7b 86 97 62 95

8 4a 8b 66 86 76 91 "All the reactions were run at room temperature for 8 h with 1 mol% Ir-based catalyst or 0.2 mol% Ru-based catalyst; ^bConversions were determined by integrating the Ή NMR spectra. Ir-M and Ru-M are Ir monomer [(ppy)₂Ir(debpy)]Cl and Ru monomer [(bpy)₂Ru(debpy)]C¾, respectively; ^cwith nitromethane as solvent; ^dwith nitroethane as solvent.

The PCPs also catalyzed Aza-Henry reactions between nitroethane and tertiary aromatic amines (Table 1 , Entry 5-8). Interestingly, most of the PCP-catalyzed Aza-Henry reactions have higher conversions than those catalyzed by their homogeneous counterparts.

We have examined recyclability and reusability of the PCP catalysts. Ir-PCP and Ru- PCP were readily recovered from the reaction mixtures via simple filtration. The recovered catalyst showed no deterioration of conversion% for Aza-Henry reactions after recycling 4 times (Table 3). Furthermore, UV-Vis analysis of the supernatant showed no sign of Ir/Ru- complex leaching into the solution. This is further supported by the absence of Ir or Ru in the supernatants of the PCP-catalyzed reaction mixtures by ICP-MS.

Scheme 2. Ru-PCP catalyzed a-arylation of bromomalonate and oxyamination of 3- phenylpropanal. The Ru-PCP catalyst was readily recovered and re-used for these reactions.

We have also demonstrated the applicability of the PCP photocatalysts in other visible light-driven reactions. As shown in Scheme 2, Ru-PCP efficiently catalyzed the a-arylation of bromomalonate via direct intermolecular C-H functionalization^3e as well as oxyamination of 3-phenylpropanal,¹⁴ with comparable isolated product yields to those of the homogeneous control catalyst. We also showed that the Ru-PCP catalyst could be readily recovered and reused for all of these reactions with no or little drop in the product isolated yields (Scheme 2). These results illustrate the generality of the phosphorescent PCP materials in catalyzing photo-driven organic transformations.

Conclusion. Ir and Ru phosphors have been successfully integrated into porous crosslinked polymers via cobalt catalyzed alkyne trimerization. The resultant framework materials are stable in various solvents, including concentrated hydrochloric acid, and are thermally and oxidatively stable in air up to 350 °C. These phosphorescent Ir- and Ru-based PCPs were shown to be highly active, recyclable and reusable heterogeneous photocatalysts in Aza-Henry reactions of a variety of amine substrates. This work highlights the potential of using PCPs as a stable and molecularly tunable platform for developing highly efficient heterogeneous photocatalysts for a number of important organic transformations.

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(12) For other examples of microporous polymer networks built from tetrahedral monomers, see: (a) Ben, T.; Ren, H.; Ma, S. Q.; Cao, D. P.; Lan, J. H.; Jing, X. F.; Wang, W. C; Xu, J.; Deng, F.; Simmons, J. M.; Qiu, S. L.; Zhu, G. S. Angew. Chem, Int. Ed. 2009, 48, 9457. (b) Rose, M.; Bohlmann, W,; Sabo, M.; Kaskel, S. Chem. Commim, 2008, 2462. (c) Stockel, E.; Wu, X.F.; Trewin, A.; Wood, CD.; Clowes, R.; Campbell, N.L.; Jones, J.T.A.; Khimyak, Y.Z.; Adams, D.J.; Cooper, A.I. Chem. Commim. 2009, 212. (d) Hoist, J.R.; Stockel, E.; Adams, D.J.; Cooper, A.I. Macromolecides 2010, 43, 8531.

(13) The hysteresis loops at high pressures can also be ascribed to the swelling effect of the PCPs as observed in other microporous polymer networks. See: Weber, J.; Antonietti, M.; Thomas, A. Macromolecides 2008, 41, 2880.

(14) Koike, T.; Akita, M. Chem. Lett. 2009, 38, 166.

1. General Experimental

All starting materials were purchased from Aldrich and Fisher, unless otherwise noted, and used without further purification. Ή-NMR spectra were recorded on a Bruker NMR 400 DRX Spectrometer at 400 MHz and referenced to the proton resonance resulting from incomplete deuteration of deuterated chloroform (δ 7.26). C{ H} NMR spectra were recorded at 100 MHz, and all of the chemical shifts are reported downfield in ppm relative to the carbon resonance of chloroform-i i (δ 77.0). Mass spectrometric analyses were conducted using positive-ion electrospray ionization on a Bruker BioTOF Mass Spectrometer. Powder X-ray diffraction (PXRD) analyses were carried out on a Bruker SMART APEX II Diffractometer using Cu radiation, processed with the APEX II package using PILOT plug- in. A Varian 820-MS Inductively Coupled Plasma-Mass Spectrometer (ICP-MS) was used to determine Ir content. Scanning electron microscopy (SEM) and transmission electron microscope (TEM, JEM lOOCX- II ) were used to image the particles, using a Hitachi 4700 Field Emission Scanning Electron Microscope. A Cressington 108 Auto Sputter Coater equipped with a Au/Pd (80/20) target and an MTM-10 thickness monitor was used to coat the samples with a conductive layer before taking SEM images. Each SEM sample was prepared by first suspending the material in ethanol, then a drop of the suspension was placed on a glass slide and the solvent was allowed to evaporate. Thermogravimetric analysis (TGA) was performed using a Shimadzu TGA-50 equipped with a platinum pan, and all samples were heated at a rate of 5 °C per minute under air. Nitrogen adsorption experiments were performed with a Quantachrome Autosorb-lC. Quenching experiments were performed using a Shimadzu RF-5301 PC Spectrofluorophotometer.

2. Procedures for monomer synthesis.

2.1 Synthesis of [Ir(ppy)2(dbpy)]Cl. [Ir(ppy)₂Cl₂]₂ and 5,5'-diethyneyl-2,2'-

1 2

bipyridine were synthesized by following the published procedures. ' [Ir(ppy)₂Cl ]₂ (200 mg, 0.19 mmol) and 5,5'-diethyneyl-2,2'-bipyridine (76 mg, 0.37 mmol) were suspended in 15 mL 1 : 1 MeCN/CHCl₃ under argon. After refluxing overnight, evaporation of the solvent under reduced pressure yielded a red solid, which was dissolved in a small amount of CHC1₃ and then filtered through a short silica column. A reddish-orange band was eluted by 1 : 1 MeCN/0,4N KN0₃. Afterward, the organic solvent was removed under vacuum, and the precipitate was collected by filtration and redissolved in CHC1₃. The solution was dried over MgS0₄, and the solvent was removed under vacuum to afford [Ir(ppy)₂(dbpy)]Cl. Yield: 150 mg (55 %) Ή NMR (CDC1₃): 9.17 (d, 2H), 8.19 (d, 2H), 7.88-7.93 (m, 4H), 7.76 (t, 2H), 7.65 (d, 2H), 7.45 (d, 2H), 7.02 (m, 4H), 6.88 (t, 2H), 6.21 (d, 2H), 3.35 (s, 2H). ¹³C{1H} NMR (CDC1₃): 167.64, 154.63, 152.45, 148.98, 148.50, 143.18, 142.89, 138.27, 131.51 , 130.95, 126.34, 124.90, 123.74, 123.39, 122.92, 1 19.80, 85.60, 78.10. MS (ESI): 705.06 m/Z, expected 705.16 m/Z for [C₃6H₂4N₄Ir]⁺ [(M-C1)]⁺].

2.2 Synthesis of [Ru(bpy)₂(dbpy)]Cl₂. Ru(bpy)₂Cl₂ (155 mg, 0.32 mmol) and 5,5'- diethyneyl-2,2'-bipyridine (76 mg, 0.37 mmol) were dissolved in 50 mL of ethanol. The solution was refluxed overnight with stirring and then cooled to room temperature. The solvent was removed under vacuum. The residue was purified by silica gel column chromatography (first CH₂Cl₂/methanol, 10:1, then CH3CN/KN03 (1/1, v/) ) to afford pure [Ru(bpy)₂(dbpy)]Cl₂. 'H NMR (CD₃CN): 9.54 (d, 1H), 9.35 (d, 2H), 8.47-8.54 (m, 5H), 8.38 (d, 1H), 8.34 (t, 1H), 8.22 (t, 1H), 8.03-8.14 (m, 4H), 7.85 (t, 1H), 7.74 (m, 3H), 7.50 (s, 1H), 7.43 (m, 2H), 7.30 (t, 1H), 3.52 (s, 2H). MS (ESI): 618.02 m/Z, expected 618.11 m/Z for [C₃₄H₂₄N₆Ru]¹⁺.

3. Synthesis and characterization of Ir- and Ru-PCPs.

3.1 Synthesis of Ir-PCP and Ru-PCP. Tetra(4-ethynylphenyl)methane was synthesized by following the published procedure.³ [Ir(ppy)₂(dbpy)]Cl (10 mg, 0.014) and tetra(4- ethynylphenyl)methane (100 mg, 0.24 mmol) were charged into a flame-dried round-bottom flask. Anhydrous dioxane (5 mL) was added via a syringe and the mixture was stirred for 5 min. Co₂(CO)8 (30 mg, 0.088 mmol) was added under the protection of nitrogen, and the mixture was stirred for 5 mi. The reaction flask was then put in an oil bath that was preheated at 115 °C. The brown solution started to solidify after about 5 min, The reaction mixture was continued with heating for another 5 min, and then the flask was lifted above. the oil bath to cool to room temperature. The brown solid was collected by filtration and washed with methanol and water. The solid was redispersed in concentrated HCl for 2 h. The product was obtained by filtration, and washed with water and methanol and dried under vacuum. Yield: 113 mg (97%). The Ru-PCP was prepared similarly in quantitative yields.

3.2 Characterization of Ir-PCP and Ru-PCP.

Figure 2 shows the p Powder X-ray diffraction (PXRD) of Ir-PCP and Ru-PCP. The low intensity broad peaks indicate the amorphous nature of the PCPs. Figure S2 shows the pore size distribution of Ir-PCP and Ru-PCP calculated by density functional theory (DFT). Figure S3 shows the cumulative pore volume of Ir-PCP and Ru-PCP calculated by DFT. Figure S4 shows an idealized structure of the Ir-PCP.

3.4 Quenching experiments of Ru-PCP

1 mg of Ru-PCP was suspended in 3 mL of CH₃N0₂ and ground by vigorously stirring overnight to yield small and uniform particles. The substrate la was added stepwise to the degassed suspension, and phosphorescence spectra were collected under steady stirring after the addition of la every time.

Figure 6 shows a Stern-Volmer plot of Ru-PCP quenching by la, compared to that of the homogeneous monomer [(bpy)2Ru(debpy)]C12. Stern-volmer constant for Ru-PCP is 23 NT¹ , and 20 M^"1 for [(bpy)₂Ru(debpy)]Cl₂.

4 Photocatalysis results:

General procedure for Aza-Henry reactions: All of the substrates were synthesized by following the literature.⁴ To a flame-dried 10 mL vial equipped with a magnetic stir bar were added catalyst (1.25 μηιοΐ, 0.01 equiv), tetrahydroisoquinoline derivative (1.25 mmol, 1.0 eq), and the nitromethane or nitroethane solvent (0.5 mL). The reaction mixture was stirred at room temperature with the cap removed and at a distance of ~10 cm from a 26 W fluorescent lamp. After the reaction was completed, the catalyst was removed by centrifuge or filtration. The filtrate was dried in vacuo and the Ή NMR spectrum of the crude product was taken. The conversion was calculated by integrating the ^lH NMR sepctrum. Figure 7. For entry 1 and 2, the peak at 5.48 ppm of the product and the peak at 4.39 ppm of the substrate in the 1H NMR were used to calculate the conversions.

Figure 8. For entry 3, 4, the peak at 5.53 ppm of the product and peak at 4.42 ppm of the substrate in the Ή NMR were used to calculate the conversions.

Figure 9. For entry 5 and 6, the peaks at 5.24 and 4.43 ppm of the product and peak at 3.50 ppm of the substrate in the Ή NMR were used to calculate the conversions.

Figure 10. For entry 7 and 8, the peaks at 5.24 and 4.42 ppm of the product and peak at 3.50 ppm of the substrate in the Ή NMR were used to calculate the conversions.

Table 2. Control Aza-Henry reactions ^a

oc-arylation of bromomalonate: The reaction condition used is similar to the literature.⁵ To a flame-dried 10 mL vial equipped with a magnetic stir bar were added the methyl indole- 2-carboxylate or 2,4-dimethylpyrrole (0.15 mmol, 1 equiv), 4- methoxytriphenylamine (0.30 mmol, 2.0 equiv), diethyl bromomalonate (0.30 mmol, 2.0 equiv), the catalyst (1.5 μιηοΐ, 0.01 equiv) and DMF (1.5 mL). The mixture was degassed via the freeze-pump-thaw method and placed at a distance of 2-5 cm from the fluorescent lamp (26 W). After the reaction mixture was stirred at room temperature for 24 h, the mixture was washed with EtOAc and water. The organic layers were washed with water and brine, dried over MgS0₄ and concentrated. The residue was purified by chromatography on silica gel, using hexanes/EtOAc (9/1, v/v) to afford the desired product.

Oxyamination of 3-phenylpropanal: The experimental procedure is the same with the literature procedure.⁶ A 75 W fluorescent lamp was used for this reaction.

determined by IT NMR.

References:

1. Sprouse, S.; King, K. A.; Spellane, P. J.; Watts, R. J. J. Am. Chem. Soc. 1984, 106, 6647.

2. Grosshenny, V.; Romero, F. M.; Ziessel, R. J. Org. Chem., 1997, 62, 1491.

3. Yuan, S.; Kirklin, S.; Dorney, B,; Liu, J. -J.; Yu, L. Macromolecules 2009, 42, 1554.

4. Condie, A. G.; Gonzalez-Gomez, J.; Stephenson, C. R. J. J. Am. Chem. Soc. 2010, 132, 1464.

5. Furst, L.; Matsuura, B. S.; Narayanam, J, M. R.; Tucker, J. W.; Stephenson, C. R. J. Org.

Lett., 2010, 12, 3104.

6. Koike, T.; Akita, M. Chem. Lett. 2009, 38, 166.

EXAMPLE 2

Polymeric Materials prepared by Pd-coupling reactions 1. Synthesis of Ru-CP. [Rutheiiiiim(Il)(2,2'-bipyridine)₂(5,5'-dibromo-2,2'- bipyridine)](PF₆)₂ and tetra(4-ethynylphenyl) methane were synthesized by following the literature.¹'² [Ruthenium(II)(2,2'-bipyridine)₂(5,5 '-dibiOmo-2,2'-bipyridine)](PF6)2 (50mg,

0.050mmol), tetra(4-ethynylphenyl) methane (15mg, 0.037 mmol), tetrakis(triphenylphosphine)palladium (15mg), and copper ( I ) iodide (10 nig) were dissolved in the mixture of DMF (2.5 mL) and triethylamine (2.5 mL). The reaction mixture was heated to 90 °C and stirred for 72 li under a nitrogen atmosphere. The mixture was cooled to room temperature, and the insoluble precipitated product was filtered and washed with acetonitrile, water, methanol, and acetone to remove any unreacted monomers or catalyst residues. Further purification of the product was carried out by stirring in methanol for 2 days and filtered it. The product was dried under vacuum for 24 H at 50 °C to give brown powder.

Scheme 2

2. Characterization of Ru-COF

Additional characterization of Ru-COF is given in Table 4 below and Figures 1 1 through 15. Figure 11 provides a thermogravimetric analysis (TGA) of Ru-COF; Figure 12 provides an emission spectra (excitation wavelength is 450nm); Figure 13 provides SEM (scanning electron micrograph) photographs; Figure 14 provides an FT-IR spectra; and Figure 15 provides a BET plot. Table 4. Weight content of metal in the COF

3. Photocatalysis

3.1 Aza-Henry reaction. All of the substrates were synthesized by following the literature.⁴ To a flame-dried 10 mL vial equipped with a magnetic stir bar were added catalyst (1.25 umol, 0.01 equiv), tetrahydroisoquinoline derivative (1.25 mmol, 1.0 eq), and the nitromethane or nitroethane solvent (0.5 mL). The reaction mixture was stirred at room temperature with the cap removed and at a distance of ~10 cm from a 26 W fluorescent lamp. After the reaction was completed, the catalyst was removed by centrifuge or filtration. The filtrate was dried in vacuo and the 'Η NMR spectrum of the crude product was taken. The conversion was calculated by integrating the NMR sepctrum.

1 a, 1 = H 1 b, R= H R2=H

2a, R1 = Br 2b, R= Br R2=H

3a, R1 = 0CH₃ 3b, R= OCH₃ R2=H

4b, R= H R2=CH₃

5b, R= Br R2=CH₃

6b, R= OCH3 R2=CH₃

entry amine product conv. (%) with Ru- substrate COFs l^c la lb 97

reuse la lb 95

2^C 2a 2b 100

3^C 3a 3b 100

4^d la 4b 94

5^d 2a 5b 88

6^d 3a 6b 100

"All the reactions were run at room temperature for 8 h 0,2 mol% Ru-based catalyst; Conversions were . determined by integrating the Ή NMR spectra; ^c with nitromethane as solvent; ^d with nitroethane as solvent.

a Reaction was run in nitromethane with substrate l a. Conversion yields were determined by H NMR.

3.2 dehalogenation of activated benzylic halides. To a flame-dried 5 Ml vial equipped with a magnetic stir bar were added catalyst (2 pmol, 0.01 equiv), bromoacetophenone (40mg, 0.2 mmol, 1.0 eq), DIPEA (70 Ml), diethyl-2,6-dimethyl-l ,4- dihydropyridine-3,5-dicarboxylate ("Hantzsch ester", 56 mg ) and the DMF (0.75 Ml). The mixture was degassed by "freeze-pump-thaw" cycle (3 times), then was stirred at room temperature at a distance of ~5 cm from a 26 W fluorescent lamp. After the reaction was completed, the catalyst was removed by centrifuge or filtration. The filtrate was washed in vacuo and the Ή NMR spectrum of the crude product was taken. The conversion was calculated by integrating the Ή NMR spectrum.

After 18 h, no starting materials were found. NMR shows the yield is almost 100% with Ru- CP.

3.3 Aerobic oxidative coupling of amines. To a flame-dried 10 Ml vial equipped with a magnetic stir bar were added Ru(bpy)₂Cl₂ (0.01 equiv), benzylamine (38 Ml, 1.0 eq), and the acetonitrile solvent (3 Ml). The reaction mixture was stirred at 60 °C at a distance of ~10 cm from a 300 W Xe lamp.

were eterm ne y ntegrat ng t e spectra. Reference:

1. D. V. Kozlov.; D. S. Tyson.; C. Goze.; R. Ziessel.; F. N. Castellano. Inorganic Chemistry 2004, 43, 6083-6092.

2, Yuan, S.; Kirklin, S.; Dorney, B.; Liu, J. -J.; Yu, L. Macromolecules 2009, 42, 1554.

3 Kodama, S.; Yoshida, J.; Nomoto, A.; Ueta, Y.; Yano, S.; Ueshima, M.; Ogawa, A. Tetrahedron Letters 2010, 51, 2450-252.

Hydrogen generation

1. Synthesis of Ir-CP. [Iridium(2-phenylpyridine)₂(5,5 '-dibt mo-2,2 '-bipyridine)]Cl (42 mg, 0.050mmol), tetra(4-ethynylphenyl)methane (15mg, 0.037 mmol), tetrakis(triphenylphosphine)palladiiim (15mg), and copper ( I ) iodide (10 mg) were dissolved in the mixture of DMF (2.5 mL) and triethylamine (2.5 mL). The reaction mixture was heated to 90 °C and stirred for 72 h under a nitrogen atmosphere. The mixture was cooled to room temperature, and the insoluble precipitated product was filtered and washed with acetonitrile, water, methanol, and acetone to remove any unreacted monomers or catalyst residues. Further purification of the product was carried out by stirring in methanol for 2 days and filtered it. The product was dried under vacuum for 24 H at 50 °C to give brown powder.

Hydrogen evolution. To a flame-dried 4 n L vial equipped with a magnetic stir bar were added the catalyst (2.26 μιηοΐ Ir), sacrificial reagent triethyl amine (0.4 mL), THF/H₂0 solvent (1.5 mL), and cocatalyst Fe₂ (CO)₉ ⁴(18.5 μι οΐ) or K₂PtCl₄.⁵(0.066 μηιοΐ) The reaction mixture was degassed for lOmins, and then sealed. The vial was put at a distance of ~10 cm from a 450 W Xe lamp with a 300 nm cut-off filter with stirring. After 6 hours, the gas in the headspace of the vial was analysis by GC, and the amount of H₂ generated was determined.

co-catalyst

Fe₂(CO)₉ or K₂PtCI₄ entry cocatalyst H₂ generated (μηιοΐ)

1° Fe₂ (CO)₉ 5.4

2 K₂PtCl₄ 1.0 References

[4] Gartner F., Sundararaju B., Surkus A. E., Boddien A., Loges B., Junge H., Dixneuf P. H., Beller M. Angew. Chem. Int. Ed. 2009, 48, 1 -5

[5] Goldsmith J. I., Hdson W. R., Lowry M. S., Anderson T. H„ Bernhard S. J. AM. CHEM. SOC. 2005, 127, 7502-7510.

EXAMPLE 3

Crosslinked Polymers with Exceptionally High Ru(bipy)₃ ²⁺

Loadings for Efficient Heterogeneous Photocatalysis

In this example, we report the synthesis of new butadiyne-type CPs 1 and 2 with very high Ru(bpy)₃ ²⁺ loadings via Eglinton homocoupling of tetra(ethynyl) derivatives of Ru(bpy)₃ (Scheme 2). The resultant CPs with diamondoid network as the ideal structure prototype are highly active and recyclable photocatalysts for a range of organic transformations including aza-Henry reactions, aerobic oxidative coupling of amine, and reductive dehalogenation reactions.

Results and Discussion

4,4'-bis[tri(isopropyl)silylethynyl]-2,2'-bipyridine was prepared by a Pd-catalyzed Sonogashira reaction between 4,4'-dibromo-2,2'-bipy⁴⁶ and [tri(isopropyl)silyl] acetylene in 93% yield. 4,4'-bis[tri(isopropyl)silylethynyl]-2,2'-bipy was treated with [Ru(DMSO)₄Cl₂] in DMF at 140 °C for 8 h to give bis{[4,4'-bis(triisopropyl)silylethynyl]-2,2'-bipy}ruthenium dichloride in 83% isolated yield,⁴⁷ which was converted to Ru{[4,4'- bis(triisopiOpyl)silylethynyl]-2,2'-bipy}₂(2,2'-bipy)Cl₂ (TIPS-Ru-1) in 73% yield by treating with 2,2'-bipy. Removal of the tri(isopropyl)silyl (TIPS) groups with tetrabutylammonium fluoride (TBAF) gave Ru[4,4'-bis(ethynyl)-2,2'-bipy]₂(2,2'-bipy)Cl₂ (Ru-1) in 60% isolated yield. The regioisomers with ethynyl groups in the 5,5'-positions of the bipy ligands, Ru{[5,5^l-bis(triisopiOpyl)silylethynyl]-2,2'-bipy}₂(2,2'-bipy)Cl₂ (TIPS-Ru-2) and Ru[5,5'- bis(ethynyl)-2,2'-bipy]₂(2,2'-bipy)Cl₂ (Ru-2) were similarly synthesized starting from 5,5'- dibromo-2,2'-bipy⁴⁸ in 58%> and 23%> overall yield, respectively (Scheme 1). All of the

1 13 compounds were purified by silica gel chromatography and characterized by H and C NMR spectroscopy and electrospray ionization-mass spectrometry. The Ή NMR spectra of Ru-1 and Ru-2 both showed a pair of closely spaced singlets at approximately δ 4.35 ppm and 4.07 ppm for the terminal alkynyl protons, respectively. These chemical shifts have moved downfield as a result of coordination to the Ru centers when compared with ~δ 3.2 ppm for the alkynyl protons of free bipy derivatives (data not shown).⁴⁹ The monomers Ru-1 and Ru-2 are readily soluble in polar solvents such as MeOH, CH₃CN, and H₂0.

Oxidative Eglinton coupling reactions of the two regioisomeric tetra(ethynyl) derivatives of Ru(bpy)₃ ²⁺ were carried out with the CVLCI/Ν,Ν,Ν',Ν'- tetramethylethylenediamine catalyst under an oxygen atmosphere in acetonitrile at 35 °C for 0.5 h.⁵⁰ The resulting solids were washed with pyridine, methanol, water, and dried in vacuo to afford CPs 1 and 2 in 95% and 91% yield, respectively. Both 1 and 2 are black-red amorphous powders that are insoluble in common organic solvents such as DMF, H₂0, CH₃CN, and resistant toward acids and bases. 1 and 2 were characterized by inductively coupled plasma mass spectroscopy (ICP-MS), Fourier transform-infrared spectroscopy (FT- IR), thermo gravimetric analysis (TGA), nitrogen adsorption, and transmission electron microscopy (TEM).

Scheme 3. Synthesis of Ru(bipy)₃ -based crosslinked polymers 1 and 2.

Figure 17 shows the n Nitrogen sorption isotherms of 1 and 2 in at 77 .

2__|_

Based on the ICP-MS results, 1 and 2 possess exceptionally high [Ru(bpy)₃] loadings of 91.0±5.0 wt% and 89.6±5.0 wt%, respectively, close to that of the stoichiometric polymer formulae (87.0 wt%). Compared to previously reported [Ru(bpy)3]²⁺-containing porous CPs (2.2-4.5 wt%),⁴⁵ the phosphor loadings in 1 and 2 have drastically increased as a result of support-less single component homocoupling reactions. The high concentrations of [Ru(bpy)₃]²⁺ dyes in the structures can not only enhance visible light absorption but also facilitate excited state migration in the CP networks through Dexter triplet to triplet energy transfer. The degree of polymerization is indicated by the IR spectra. IR spectra of monomers Ru-1 and Ru-2 showed a diagnostic absorption of carbon-hydrogen stretching peak of the C≡C-H group at about 3180 cm^"1 and 3200 cm^"1, respectively (Figure 16). These peaks are mostly absent in the IR spectra of the CPs, indicating that most of the terminal alkyne groups in the monomers have been consumed in the oxidative Eglinton coupling reactions. The particles are stable up to 200 °C in air, as revealed by TGA, which is consistent with previously reported CPs polymers based on butadiyne linkages.⁵¹

Figure 18 shows the TEM images of 1 (a) and 2 (b) on a carbon-coated Cu/Ni grid.

The porosity of the CPs was investigated by nitrogen sorption measurements at 77 K. 1 exhibits a BET surface area of 198 m²/g whereas 2 shows a negligible BET surface area of 15 rn /g. These surface areas are significantly lower than the CPs based on tetrakis(4- ethynyl-phenyl)methane.^51"52 We attributed the low porosity of 1 and 2 to the bulky groups of the [Ru(bpy)₃]²⁺ complexes in the polymer networks, which is known to reduce the porosity of CPs. The TEM sample was prepared by first dispersing the CPs in methanol, and then placing them on carbon-coated Cu/Ni grids. TEM images of both 1 and 2 showed that they are aggregates of spherical nanoparticles of ~100 nm in diameter.

Figure 19 shows the steady-state absorption spectra of stirred suspensions of 1 and 2 in CH₃CN (0.74 mg/50 mL) and dilute solutions of Ru-1 and Ru-2 in CH₃CN (2x l0^"5 M). Absorption spectra of Ru-1 and Ru-2 are on a reduced scale (x 0.2).

Figure 20 shows the steady-state phosphorescence spectra of stirred suspensions of 1 and 2 in CH₃CN (0.74 mg/50 mL) and dilute solutions of Ru-1 and Ru-2 in CH₃CN (2x l0^"5 M).

CPs built from [Ru(bpy)₃]²⁺ complexes act as insoluble but dispersible photosensitizers by taking advantage of redox-active MLCT excited states of the chromophores. Steady-state UV-vis absorption and emission spectra and time-resolved phosphorescence spectra were recorded with a stirred suspension of 1 or 2 in CH₃CN and dilute solutions of Ru-1 and Ru-2 monomers in CH₃CN (2x l 0^"5 M). They all showed a broad absorption between 300-800 nm with two or three additional discernible absorption bands. For 1, the absorption peak at -294 nm is assigned to the π→π* bipy ligands in the [Ru(bpy)₃]²⁺ whereas the peak at -493 nm is attributed to the metal-to-ligand charge transfer ('MLCT) transition. Compared with Ru-1 amd Ru-2, the 'MLCT peaks in CPs 1 and 2 became broadened and showed a slight red-shift, which is beneficial to absorbing the solar radiation. In the steady-state phosphorescence spectra, the emission maximum X_max centered at 705 nm for 1 and at 696 nm for 2. Interestingly, the phosphorescence maximum λ_ηΐ3χ of 1 exhibited obviously red shift in comparison with monomer Ru-1 owing to the increased effective conjugation length of ligands in CP-1 and aggregation of 1 in the particle. The phosphorescence lifetimes of the CPs were measured using an Edingburgh FLS 920 in the time-correlated photon counting mode. When excited at ~ 440 nm, the decays of monomers Ru-1 and Ru-2 and CP-1 were well fitted with a mono-exponential model, leading to emission lifetimes of 962 ns, 574 ns, and 423 ns, respectively. The emission decay of 2 was fitted with a double-exponential model to give an averaged lifetime of 112 ns, indicating a much shorter-lived ³MLCT phosphorescence. The broad absorption bands together with relatively long excited state lifetimes of the CPs make them good candidates as heterogeneous photocatalysts.

Figure 21 shows the time-resolved phosphorescence decays of 1 and 2 and monomers Ru-1 a nd Ru-2 (excitation: 440 nm; emission: 660 nm).

We examined the photocatalytic activities of the CP particles, using the aza-Henry reaction,¹⁸'⁵³ aerobic oxidative coupling of amine,⁵⁴ and dehalogenation of benzyl bromoacetate¹⁷ as representative reactions. CPs 1 and 2 exhibited high photocatalytic activities in these reactions. Aza-Henry reactions between tetrahydroisoquinoline derivatives 3-5 and nitromethane were carried out in air for 8 h with 0.2 mol% of CPs as the catalysts and a common fluorescent lamp (26 W) as the light source. As shown in Table 1, the conversions of the reactions were calculated based on the Ή-NMR peak integrations of the crude products, After filtering off the CP catalysts, the solvents were removed and the crude products were analyzed by ^-NMR. The integrations of peaks of the featured protons in the products (about δ 5.5 ppm) and those of the corresponding starting materials (about δ 4.4 ppm) were used in the calculation (not shown). CP-1 gave a slightly higher conversion (94% for 3 with the phenyl substituent, 96% for 5 with the ra-methoxylphenyl substituent, and 99% for 4 with the ^ra-bromophenyl substituent) than CP-2 (92% for 3, 96% for 5, and 94% for 4). Notably, these conversions are slightly higher than those catalyzed by other Ru- or Ir- based crosslinked polymers we reported previously.⁴⁵ Moreover, aza-Henry products were isolated in very high yields after purification by chromatography (Table 4). We have also carried out several control experiments to further investigate the details of these heterogeneous photocatalytic reactions. For example, the conversions and isolated yields afforded by 1 and 2 are higher than those of the monomer homogeneous catalysts (TIPS-Ru- 1 and TIPS-Ru-2). Ru-1 and Ru-2 are unstable and will polymerize under the photocatalytic reaction conditions and could not be used as control homogeneous catalysts. Moreover, low conversions (< 20%) were detected in the absence of either light or the catalyst, indicating the photocatalytic nature of these reactions. We have also recycled and reused the CP catalysts. 1 was easily recovered from the reaction mixture by filtration, and could be re-used for at least three times. The recovered solid CP catalysts showed only slight decrease in conversions and isolated yields of aza-Hemy products. CPs 1 and 2 as catalysts. a

3 R = H P3 R = H

4 R = Br P4 R = Br

5 R = CH-,0 P5 R = CH₃0

Compds Catalyst Conversion%" Isolated yield%^u

3 1 94 85

3 TIPS- 91 76

Ru-1

4 1 99 89

4 l(2^nu- 91 85

use)

4 l(3^^u- 90 80

use)

4 1(4^A- 87 76

use)

5 1 96 90

3 2 92 81

3 TIPS- 90 77

Ru-2

4 2 94 83

5 2 96 82

"All of the reactions were carried out at room temperature with 0.2 mol% ratio catalyst for 8 h with a 26 W fluorescent lamp; ^bconverisions were determined by integrating the Ή NMR peaks; isolated yields were calculated based on pure products after column chromatography.

We further examined the scope of reactions catalyzed by the CPs. As shown in Table 5, aerobic oxidative coupling of a series of primary amines were also efficiently catalyzed at 1 mol% CP catalyst loadings with a 450 W Xe lamp. The conversions of various substrates catalyzed by the CPs were calculated based on the integration of the ¹H-NMR peaks of the featured protons in the products and those of the corresponding starting materials (data not shown). Nearly complete conversions (99%) of all the three substrates were observed with 1 as photocatalyst, which compare favorably with the monomer control catalyst. In contrast, the conversions for 2 were highly dependent on the substrates (99% for benzylamine, 76% for p- methylbenzylamine, 67% for /j-methoxylbenzyl amine). Moreover, low conversions (< 5%) were obtained in the absence of either light or the catalysts, confirming the photocatalytic role of the CPs. We have also determined the yields of oxidative coupling products by gas chromatography (GC) with «-undecane as the internal standard. The GC yields were slightly lower than the Ή-NMR conversions, but they both showed the same trends. We believe that some of the starting materials were consumed to form other byproducts that were not detected by GC. We also demonstrated that the photocatalyst 1 could be readily recovered and reused twice for all these three substrates with only slight decrease of the conversions and yields.

The photocatalyzed reductive dehalogenation reaction was also examined using the CP photocatalysts (Scheme 4).

Scheme 4.

Photocatalytic dehalogenation of benzyl bromoacetate using land 2 as catalysts.

Benzyl bromoacetate was chosen as the substrate and a 26 W fluorescent lamp was used as the light source. Benzyl bromoacetate was completely converted to benzyl acetate with 1 mol% loadings of photocatalyst 1 or 2 based on ^JH NMR spectra (data not shown). These results have been corroborated with high isolated yields of the benzyl acetate (92% for 1 and 86% for 2). A control reaction in the absence of the CPs gave <10% conversion. The CP photocatalyst could also be recovered and reused without significant decrease in conversions and yields.

Table 5. Photocatalytic aerobic oxidative coupling reactions using CPs 1 and 2 as catalysts.

visible light, 60 °C, 1 h

6 R = H P6 R = H

7 R = CH₃ P7 R = CH₃

8 R = OCH₃ P8 R = OCH₃

Compds Catalyst Conversion GC yield%

%⁶

6 1 99 93

7 1 99 88

7 l(2"^u- 99 85

use)

7 l(3 ^u- 97 84

use)

8 1 99 87

6 2 99 88

7 2 76 52

8 2 67 51

6 TIPS- 99 89

Ru-2

7 TIPS- 97 87

Ru-2

8 TIPS- 90 79

Ru-2

All of the reactions were done at 60 C for 1 h with lmol% catalyst under a 450 W Xe lamp; Converisions were determined by integrating the 1H NMR peaks.

The almost nonporous nature of Ru-based CPs indicates that only a small fraction of [Ru(bpy)₃]²⁺ chromophores is at or near the surface and is accessible to the organic substrates. The reason why such nonporous heterogeneous crosslinked polymers still exhibit extremely high photocatalytic activity can be explained by efficient excited state migration among the chromophore framework. The interior [Ru(bpy)₃]²⁺chromophores of the crosslinked polymers can be excited by light, and the generated excited states can migrate among the chromophore networks through Dexter triplet to triplet energy transfer, finally reaching the reactive sites of the polymer surface to drive redox reactions.⁵⁵ We suggested that Ru chromophores in the interior of the polymers can effectively serve as light harvesting antemia to collect photon energy and transfer them to the reactive sites. The Ru chromophores on the surface can either be directly excited by light or accept excited state energy from the interior of the polymer particle,⁵⁶ and then go through redox reactions to initiate the catalytic cycle. Such a light- harvesting phenomenon was recently umambiguously demonstrated by Lin et al. in [Ru(bpy)₃]²⁺-derived MOFs.⁵⁷

Conclusion. Two different crosslinked polymers based on Ru(bpy)₃ ²⁺ chromophores with tetra-alkynyl substituents at 4,4',- or 5,5',- position of two bipyridine moieties were synthesized through Eglinton alkyne homocoupling with high yields and extremely high chromophore loadings (~90%). The CPs are almost nonporous with small surface areas based on the nitrogen adsorption experiments at 77 K, but efficiently catalyze a range of organic transformations (aza-Hemy reaction, aerobic oxidative coupling of amine, and reductive dehalogenation reaction) in the presence of visible light. The excellent photocatalytic activities are attributed to high content of light-absorbing Ru(bpy)₃ ²⁺ chromophores as well as excited state energy migration from the chromophores in the interior of the polymer particle to the reactive sites on the surface of the polymer particle.

Experimental

General Procedures. Chemicals were purchased and used without further purification. Ή and ¹³C NMR spectra were recorded on a Bruker NMR 400 DRX Spectrometer at 400 MHz and referenced to the proton resonance resulting from incomplete deuteration of deuterated chloroform (δ 7.27) except where noted. A Varian 820-MS Inductively Coupled Plasma-Mass Spectrometer (ICP-MS) was used to determine Ru content. Transmission electron microscopy (TEM) was used to image the particles, using a JEM l OOCX-II Transmission Electron Microscope. Thermo gravimetric analysis (TGA) was performed using a Shimadzu TGA-50 equipped with a platinum pan, and all samples were heated at a rate of 5 °C per minute under air. Nitrogen adsorption experiments were performed with a Quantachrome Autosorb-lC 77K after activating under vacuum at 60 °C for 10 h. UV-vis spectra were recorded on a Perkin Elmer Lambda 35 UV-vis spectrometer. Steady-state and time-resolved emission spectra were recorded on an Edinburgh FLS 920.

Ru{4,4'-bis[tri(isopropyl)silylethynyl]-2,2'-bipy}₂(2,2^,-bipy)Cl2 (TIPS-Ru-1). 2,2'- bipyridine (17.2 mg, 0.1 1 mmol) and bis{4,4'-bis[(triisopropyl)silylethynyl]-2,2'- bipy}ruthenium dichloride⁴⁷ (120 mg, 0.1 mmol) were dissolved in a mixture of chloroform (20 mL) and EtOH (20 mL) and refluxed for 3 days. The solvent was evaporated and the residue was purified by silica gel chiOmatography using dichloromethane/methanol (20: 1) as an eluent to afford a red solid (100 mg, 73 %). 1H NMR (CD₂C1₂, 400 MHz, ppm): δ 8.95 (d, J = 8.0 Hz, 2H, Py-T ), 8.28 (m, 4H, Py-H^), 8.13-8.17 (m, 2H, Py-H'), 7.99 (d, J = 5.6 Hz, 2H, Py-/ ), 7.94 (d, J = 5.6 Hz, 2H, Py-H"), 7.86 (d, J = 5.6 Hz, 2H, Py-H⁸), 7.53-7.57 (m, 2H, Py-H*), 7.48 (dd, J = 5.6, 1.6 Hz, 2H, Py-/ '^e), 1.13-1.17 (m, 84H, CH₃, CH); ¹³C NMR (CD₂C1₂, 100 MHz, ppm): δ 156.8, 156.5, 156.2, 152.7, 152.5, 151.9, 139.2, 133.30, 133.25, 130.7, 130.5, 128.7, 126.0, 125.6, 104.1 , 104.0, 102.4, 102.3, 18.7, 1 1.5; ESI MS (m/z): Calcd. for [C₇₄Hio4Cl₂N₆RuSi₄]⁺: 1360.6. Found: 1325.5 [M-C1^"]⁺, 645.3 [M-2C1^"]²⁺.

Ru[4,4^,-bis(ethynyl)-2,2^,-bipy]₂(2,2'-bipy)Cl₂ (Ru-1). To a solution of Ru{4,4'- bis[tri(isopropyl)silylethynyl]-2,2'-bipy}₂(2,2'-bipy)Cl₂ (160 mg, 0.12 mmol) in THF (20 mL) was added dropwisely a solution of TBAF (0.5 mmol, 0.5 mL) in THF. The reaction was stirred at RT for 10 h. The reaction was quenched with water and all of solvents was evaporated in vacuo. The crude product was purified by flash chromatography (silica gel, CH₃CN/KN03(a_q.₎, 5/1) to afford a red solid (45 mg, 60%). Ή NMR (400 MHz, ppm): δ 8.82 (m, 4H, Py-H^), 8.69-8.71 (d, J = 8,0 Hz, 2H, Py-H^/ , 8.12-8.16 (m, 2H, Py-H*), 7.78-7.85 (d, d, d, J = 5.6 Hz, J = 5.6 Hz, J = 5.6 Hz, 6H, Py-H° ^g), 7.49-7.53 (m, 6H, ?y-H^b'^e'¹), 4.329 (s, 2H, CCH). 4.322 (s, 2H, CCH). ¹³C NMR (100 MHz, ppm): δ 156.34, 156.31 , 151.0, 150.9, 150.8, 137.8, 131,89, 131.86, 129.24, 129.18, 127.2, 126.42, 126.40, 123.9, 86.8, 78.69, 78.65; ESI MS (m/z): Calcd. for [C₃₈H24Cl₂N₆Ru]⁺: 736.1. Found: 333.1 [M-2C1^"]²⁺.

5,5'-bis[tri(isopropyl)silylethynyl]-2,2'-bipyridine. To a solution of 5,5'-dibromo- 2,2'-bipyridine (0.76 g, 2.4 mmol), Pd(PPh₃)₂Cl₂ (45 mg) and Cul (24 mg) in 40 mL triethylamine were added under argon. Tri(isopropyl)silylacetylene (1.78 g, 9.6 mmol) was then added to the solution. The mixture was refluxed for 12 h under argon. After removal of the solvent, the crude product was purified by silica gel chromatography eluting with CH₂C1₂ to afford a white solid (0.9 g, 90 %). 1H NMR (400 MHz, ppm): δ 8.74 (d, J = 0.8 Hz, 2H, Py-H⁶'⁶'), 8.37 (d, J = 8.4 Hz, 2H, Py-H³'³'), 7.85-7.88 (dd, J = 8.4, 0.8 Hz, 2H, Py-H⁴'⁴'), 1.16 (m, 42H, TIPS-H). ¹³C NMR (100 MHz): δ 154.3, 152.4, 139.9, 120.9, 120.6, 104.0, 96.3, 18.9, 1 1.5; MALDI-ToF MS (m/z): Calcd. for [C₃₂H₄₈N₂Si₂+H]⁺: 517.3. Found: 517.4.

Bis {5,5'-bis[(tri(isopropyl)silylethynyl]-2,2'-bipy} ruthenium dichloride:

Ru(DMSO)₄Cl₂ (460 mg, 0.96 mmol) and 5,5'-bis[tri(isopiOpyl)silylethynyl]-2,2'-bipy (1.0 g,

I .92 mmol) were dissolved in dry DMF (30 mL) and the mixture was heated to 140 °C for 8 h. DMF was removed in vacuo and the crude dark solid was purified by silica gel chromatography using dichloromethane/methanol= 20/1 to afford a dark green solid (1.1 g, 87%). 'H NMR (CD₂C1₂, 400 MHz, ppm): δ 10.15 (d, J= 1.2 Hz, 2H, Py-H^f), 8.10 (d, J = 8.4 Hz, 2H, Py-/ ¹), 8.91-8.97 (m, 4H, Py-H⁰'⁶), 7.55-7.58 (m, 4H, Py-H^), 1.16-1.20 (m, 21H, CH₃, CH), 1.02- 1.04 (m, 21H, CH₃, CH); ¹³C NMR (CD₂C1₂, 100 MHz, ppm): δ 159.3, 156.9, 156.3, 155.7, 137.7, 135.3, 123.1 , 122.4, 122.3, 121.9, 102.5, 102.1 , 99.7, 99.6, 18.8, 18.7,

I I .7, 1 1.5; ESI MS m/z): Calcd. for [C₇₄H,o₄Cl₂N₆RuSi₄]⁺: 1360.6. Found: 1325.6 [M-Cf .

Ru {5,5^,-bis[(tri(isopropyl)silylethynyl]-2,2'-bipy}₂(2,2^,«bipy)Cl₂ (TIPS-Ru-2): 2,2'-bipyridine (55.0 mg, 0.3 mmol) and bis{5,5'-bis[tri(isopiOpyl)silylethynyl]-2,2'- bipy} ruthenium dichloride (360 mg, 0.1 mmol) were dissolved in a mixture of chloroform (20 mL) and EtOH (20 niL) and refluxed for 3 days. The solvent was evaporated and the residue was chromotographed on silica gel using dichloromethane/methanol (10: 1) as an eluent to afford a red solid (300 mg, 73 %). Ή NMR (CD₂C1₂, 400 MHz, ppm): δ 9.58 (d, J= 8.8 Hz, 2H, Py-Z ), 9.49 (d, J = 8.8 Hz, 2H, Py-H^), 8.96 (d, J = 8.0 Hz, 2H, Py-H0, 8.1 1 - 8.20 (m, 6H, Py-H*'⁶''), 7.72 (d, J = 4.2 Hz, 2H, Py-/ ), 7.50-7.54 (m, 6H, Py-H^'), 1.03- 1.1 1 (m, 84H, CH₃, CH). ¹³C NMR (CD₂C1₂, 100 MHz, ppm): δ 157.2, 155.9, 155.7, 152.9, 152.6, 151.5, 141.0, 138.9, 128.5, 126.8, 126.4, 125.6, 124.8, 124.8, 102.4, 101.0, 100.7, 18.5, 1 1.29, 1 1.28; ESI MS (m/z): Calcd. for [C₇₄Hio4Cl₂N₆RuSi4]⁺: 1360.6. Found: 1325.5 [M-Cf]⁺, 645.3 [M-2C1^"]²⁺.

Ru[5,S'-bis(ethynyl)-2,2^,-bipy]₂(2,2^,-bipy)Cl₂ (Ru-2). To a solution of Ru{5,5'- bis[tri(isopi pyl)silylethynyl]-2,2'-bipy}₂(2,2'-bipy)Cl₂ (160 mg, 0.12 mmol) in THF (20 mL) was added dropwise a solution of TBAF (0.5 mmol, 0.5 mL) in THF. The reaction was stirred at r.t. for 10 h and then quenched with water. The solvent was evaporated in vacuo and the residue was purified by flash chi matography (silica gel, CH₃CN/KN0_3(aq,), 5/1) to afford a red solid (35 mg, 40%). 1H NMR (CD₃OD, 400 MHz, ppm): δ 8.73-8.75 (d, J = 8.0 Hz, 2H, Py-H , 8.69-8.71 (d, J = 8.0 Hz, 4H, Py-H^c'^rf), 8.15-8.21 (m, 6H, Py-//^Ae), 7.893-7.896 (d, J = 1.2 Hz, 2H, Py-/ ), 7.85-7.86 (d, J = 5.6 Hz, 2H, Py-H⁸), 7.765-7.769 (d, J = 1.2 Hz, 2H, Py-/f ), 7.52-7.55 (m, 2H, Py-H*), 4.079 (s, 2H, CCH). 4.072 (s, 2H, CCH). ¹³C NMR (CD₃OD, 100 MHz, ppm): δ 156.3, 155.5, 155.2, 153.2, 152.8, 151.3, 140.3, 140.2, 137.9, 127.4, 124.0, 123.94, 123.91 , 123.1 , 122.9, 85.7, 77.1, 76.9. ESI MS (m/z): Calcd. for [C₃₈H₂₄Cl₂N₆Ru]⁺: 736.1. Found: 333.1 [M-2C1^"]²⁺.

1 or 2: Ru-1 or Ru-2 (70 mg, 0.095 mmol) was added to a stirred mixture of CuCl (1 mg, 0.01 mmol) and N,iV;N',iV'-tetramethylethylenediamine (1 mL) in CH₃CN (40 mL). 0₂ was bubbled through the mixture which was kept at 35 °C for 0.5 h. The solid was collected by filtration and washed with pyridine, methanol, water, and dried in vacuum. Further purification of the product was carried out by Soxhlet extraction with methanol for 24 h to afford the CP-1 (63 mg, 95%) or -2 (60 mg, 91%) as red-black powder, respectively.

Detailed procedures for photocatalytic reactions with CPs

Aza-Henry reactions: To a flame-dried 10 mL vial was added catalyst (0.50 μι^ηοΐ, 0.002 eq), tetrahydroisoquinoline derivative (0.25 mmol, 1.0 eq), and the nitromethane (2.5 mL). The reaction mixture was stirred at room temperature in air and at a distance of ~5 cm from a 26 W fluorescent lamp. After the reaction was complete, the catalyst was removed by filtration. After removal of the solvents, the residue was directly used in the Ή NMR spectrum. The conversion yields were calculated by integrating the peaks in the ^]H NMR spectrum. Isolated yields were obtained by silica gel column chromatography (CH₂Cl₂/hexane, 3/1 to 1/1).

Aerobic oxidative coupling of amines: To a flame-dried 25 mL flask were added catalyst (O.Olequiv), benzylamine (38 μΕ, 1.0 eq) (or other benzylamine derivatives), and the acetonitrile (10 mL). The reaction mixture was stirred at 60 °C at a distance of -10 cm from a 450 W Xe lamp. The conversion was obtained by integration of the NMR peaks.

Dehalogenation of benzyl bromoacetate: To a flame-dried 25 mL flask was added catalyst (4 μηιοΐ, 0.01 equiv), benzyl bromoacetate (92 mg, 0.4 mmol, 1.0 eq), DIPEA (140 μΕ), diethyl-2,6-dimethyl-l,4-dihydropyridine-3,5-dicarboxylate ("Hantzsch ester", 1 12 mg) and MeOH/THF(10 mL,l/l). The mixture was degassed by three freeze-pump-thaw cycles and Was stirred at room temperature at a distance of ~5 cm from a 26 W fluorescent lamp. After the reaction was complete, the catalyst was removed by filtration. After removal of the solvents, the residue was directly used in the Ή NMR determination. The conversion was calculated by integrating the ^!H NMR spectrum. The benzyl acetate product was isolated by purification with silica gel chromatography with DCM as the eluent.

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The foregoing is illustrative of the present invention, and is not to be construed as limiting thereof. The invention is defined by the following claims, with equivalents of the claims to be included therein.

Claims

THAT WHICH IS CLAIMED IS:

1. A photocatalytic polymer comprising:

(a) a first ligand as a first repeating monomelic unit;

(b) a transition metal complexed with said first ligand to form a transition metal photocatalyst therewith; and

(c) optionally at least one additional ligand complexed with said transition metal to form said transition metal photocatalyst;

wherein said polymer is crosslinked.

2. The polymer of claim 1, further comprising:

(d) a second monomelic unit copolymerized with said first monomelic unit.

3. The polymer of claim 1 to 2, wherein said first monomelic unit comprises a compound of the formula A'BCD', wherein A¹ and D' are covalent bonds or independently selected linking groups and B and C are independently selected coordinating groups, conjugated to said transition metal.

4. The polymer of claim 1 to 3, wherein said second monomelic unit comprises a compound of the formula X(Y-)_n, wherein X is an organic or silyl group, Y is an organic group, and n is 3 or 4.

5. The polymer of claim 4, wherein n is 3.

6. The polymer of claim 4, wherein n is 4.

7. The polymer of claim 1 to 6, wherein said polymer is a porous crosslinked polymer.

8. The polymer of claim 1 to 7, wherein said polymer is thermally stable at 300 °C in air at atmospheric pressure for one hour.

9. The polymer of claim 1 to 8 selected from the group consisting of:

Ru-COF: M(Xpy)₂ = Ru(bpy)₂ Ir-COF: M(Xpy)₂ = lr(ppy)₂

R= Ru(bpy)₂ or lr(ppy)₂

10. The polymer of any preceding claim having:

(a) an average pore diameter between 1 and 50 Angstroms; and

(b) an average cumulative pore volume (cm /g) of from 0.01 to 1.

11. The polymer of any preceding claim for use as a photocatalyst.

12. A method of making a photocatalytic polymer, comprising:

reacting a first monomer with a second monomer; wherein:

said first monomer comprises a compound of the formula ABCD, wherein A and D are independently selected reactive groups, and B and C are independently selected coordinating groups; and

said second monomer comprises a compound the formula X(YZ)„, wherein X is an organic or silyl group, Y is an organic group, Z is a reactive group, and n is 3 or 4.

13. The method of claim 12, wherein said coupling step is carried out by alkyne trimerization, Sonogashira coupling, Heck coupling, Suzuki coupling, polyamide coupling, or Stille coupling.

14. The method of claim 12 or 13, wherein said first monomer is a ligand complexed with a transition metal to form a transition metal photocatalyst therewith, and with at least one additional ligand optionally complexed with said transition metal to form said transition metal photocatalyst.

15. The method of claim 12 to 14, wherein said first monomer is selected from the oup consisting of:

16. The method of claim 12 to 15, wherein said second monomer is selected from the group consisting of:

17. A polymer of claim 1 to 1 1 produced by the process of claim 12 to 16.

18. A heterogeneous catalyst system comprising:

(a) from 0.1 percent to 90 percent by weight of a polymer of any preceding claim, in combination with

(b) from 10 to 99.9 percent by weight of an organic or aqueous solvent.

19. The catalyst system of claim 18, wherein said solvent is hydrochloric acid, benzene, acetone, acetonitrile, toluene, trichloroethylene, tetrahydrofuran, methanol or ethanol.

20. In a method of carrying out a photocatalytic reaction by contacting one or more substrates to a photocatalyst and exposing said photocatalyst to light to produce one or more products, the improvement comprising employing a polymer of any preceding claim as said photocatalyst.

21. The method of claim 20, wherein said reaction is selected form the group consisting of an enone cycloaddition reaction, an enentioselective alpha-trifluoromethylation of an aldehyde reaction, an enantioselective alpha-benzylation of an aldehyde reaction, a dehalogenation reaction, an aza-henry reaction, a radical addition to an indole reaction, a C-H functionalization of a heterocycle with a malonate, an alpha oxymination, an oxyamination of an enamine and andehyde, an oxidative coupling of an amine, an oxidation of an alcohol, and hydrogen evolution.

22. The method of claim 20, wherein said reaction is water splitting.

23, The method of claim 20, wherein said reaction is a reduction of carbon dioxide to form methanol or methane.

24. The method of claim 20 to 23, further comprising the steps of: separating said polymer from the product of said reaction, and then recycling said polymer in a subsequent reaction.