WO2019029789A1

WO2019029789A1 - Novel fluorinated metal complexes

Info

Publication number: WO2019029789A1
Application number: PCT/EP2017/069967
Authority: WO
Inventors: Valerio Borzatta; Isabella Zama; Paolo Righi; Giacomo Gorni
Original assignee: Tozzi Green S.P.A.
Priority date: 2017-08-07
Filing date: 2017-08-07
Publication date: 2019-02-14

Abstract

New improved fluorinated metal complexes based on bi pyridine ligands are disclosed. The complexes are characterized by a balance of fluorination among specific substituents attached to the pyridine rings, i.e. the overall number of fluorine atoms throughout said substituents ranges from 7 to 26 and, at the same time, the difference in number of fluorine atoms between said substituents is equal or less than 13. The new complexes advantageously combine a good solubility in polar solvents, in particular alcoholic ones, to an efficient photovoltaic performance.

Description

TITLE

Novel fluorinated metal complexes FIELD OF THE INVENTION

The present invention relates to novel fluorinated metal complexes effective as charge transfer photosensitizers, with utility as components of dye-sensitized solar cells (DSSC) and similar devices. BACKGROUND AND PRIOR ART

Transition metal complexes, commonly designated as dyestuffs, are useful as charge transfer photosensitizers for semiconductive titanium dioxide photo- anode layers in a photovoltaic cell. Such complexes generally consist of a light absorber and an anchoring group allowing the immobilization of the complex at the titanium dioxide surface and providing an electronic coupling between the light absorber and the titanium dioxide. The light absorber adsorbs an incoming photon via a metal ligand charge transfer and injects an electron into the conduction band of the titanium dioxide through the anchoring group. The oxidized complex is then regenerated by a redox mediator. In this process it's crucial to guide the charge transfer toward the conduction band of the semiconductor titanium dioxide surface and to assure a tight electronic overlap between the LUMO of the photosensitizer and the vacant orbital of titanium. Such complexes are disclosed in some patents, patent applications and literature.

In particular European patent EP613466 relates to a metal-complex compounds which comprises bidentate chelate ligands, being a first ligand selected from bipyridine moiety substituted with carboxyl groups and a second ligand selected from bi-pyridine substituted by alkyl group. The known dye Z907, having formula:

is described in this patent.

JACS 1 15, 6382-6390 (1993) describe metal-complex compounds comprising bidentate chelate ligand where the bipyridine moieties are substituted by four carboxyl groups (dye N3) or by four carboxyl groups partially salified by tetraalkyl ammonium (dye N719)

US patent 5,789,592 relates to a metal-complex compounds which comprises bidentate chelate ligands, consisting in bipyridine moieties substituted with phosphonic groups as anchoring groups .

JACS 123, 1613-1624 (2001 ) and International patent application WO98/50393, relate to a metal-complex compound which comprises tridentate chelate ligands, being the ligands formed by unsubstituted or substituted pyridine and pyrazole moieties containing an anchoring group selected from carboxyl or phosphonic group.

European patent EP2036955 relates to a metal-complex where the metal complex comprises two bidentate ligands containing anchoring group such as the carboxyl group and a bidentate ligand formed by a pyridine moiety substituted by an aromatic ring, being the aromatic ring unsubstituted or substituted by a halogen atom.

European patent application EP2801991 relates to a metal-complex and a cobalt mediator where the metal complex comprises at least one bidentate ligand containing an anchoring group such as the carboxyl group and a bidentate ligand comprising a first aromatic ring comprising at least one nitrogen atom as ring atom and a second aromatic ring connected to the first aromatic ring, being this bidentate ligand substituted by an alkyl group optionally substituted with fluorine . The importance of hydrophobic metal-complex for the thermal and long term stability of Dye Sensitizing Solar Cells(DSSC) is reported in Nat. Mater., 2003, 2, 402 and in Chem Commun., 2006, 2460-2462 where metal-complex are described with a long alkyl chain to increase the hydrophobicity of the metal- complex.

The hydrophobic nonyl chains of dyes, such as present in Z907, can effectively hinder water molecule penetration into the interface of the dye molecules and T1O2, leading to the long-term stability of DSSC devices; at the same time however, the enhanced hydrophobic character limits the choice of carrier- solvents into which the dye can be effectively dissolved and manipulated when manufacturing the DSSC devices; the usable solvents are typically restricted to the more hydrophobic ones, such as halogenated solvents, which present a very high toxicological profile compared to standard polar solvents such as ethanol; less hydrophobic dyes might in principle be synthesized, however it is difficult to reconcile their decreased hydrophobic character with the mutually opposite goal of achieving a long-term stability of the dye in use.

Bidentate Iigands containing bipyridine moieties variously substituted at position 4,4' and an amphiphilic heteroleptic rutenium dye for DSSC are reported by Lagref et al. in Inorganica Chimica Acta 361 (2008), 735-745 and Synthetic Metals 138 (2003) 333-339;in a limited experimental work with fluorinated Iigands, the authors introduced a partial fiuorination on only one alkyl chain of the bi pyridine moiety, with the declared aim of increasing the hydrophobic character without strongly increasing the fluorophilic affinity; unfortunately, the photovoltaic testing of the synthesized compound (a bi pyridine moiety substituted by one 4-methyl, 4'-perfluoro 1 H,1 H,2H,2H,3H,3H-undecyl group) showed a limited efficiency, possibly due to a wrong compromise between the hydrophobic character and fluorophilic activity; according to the authors, the polarized C-F bonds work as an electron trap, opposing to an efficient charge transfer; based on these grounds, the authors justify their choice not to introduce a second fluorinated chain. No suggestion is present in these works towards complexes that are stable, photovoltaic-efficient and with good solubility in polar solvents.

Therefore the need for charge transfer photosensitizers with high efficiency is still unmet. In particular, there is a strong unmet need for efficient charge transfer photosensitizers which have a high long-term stability, a good/high solubility in polar solvents, e.g. alcohols, which maintain a high photovoltaic performance. SUMMARY OF THE INVENTION

The present inventors have now made available a new group of improved fluorinated metal complexes based on bi pyridine ligands. The inventors have unexpectedly discovered that the pattern of fluorination on the two bi-pyridine substituents is of special importance in achieving the above stated goals. In particular, it was unexpectedly found that the solubility of the complex can be influenced and suitably controlled by balancing of the extent of fluorination among the two substituents attached to the respective pyridine rings; specifically, it was found important that the overall number of fluorine atoms throughout said two substituents ranges from 7 to 26 and, at the same time, the difference in number of fluorine atoms between said two substituents is equal or less than 13. Based upon this finding, new highly-fluorinated complexes were obtained which, compared to known ligands show a good solubility in polar solvents, in particular alcoholic ones, and do not incur a reduction of photovoltaic performance.

DESCRIPTION OF THE FIGURES

Figure 1 : manufacturing step in the preparation of DSSC: sealing of anode and cathode substrates.

Figure 2: Relative variation over time of the NMR peak ratio between impurity peak and peak related to the pure product.

DETAILED DESCRIPTION OF THE INVENTION

Object of the present invention are novel fluorinated metal complexes, in all their diastereoisomer configurations, as well as mixtures thereof, having formula (I):

wherein:

M is Ru, Pd, Fe, Co, Rh or Re the two X groups are, independently of each other: -SCN, -NCS, -CN, or -NCO L is a ligand of formula (II),

in which the Y groups are, independently of each other: -COOH, -PO(OH)2 SO₃H:

L' is a ligand of formula (III)

where the groups R and R', independently of each other are: H, C₁-C₉ alkyl, -O- C₁-C₉ alkyl, or a group of formula (IV)

where m is 2 or 3, p is an integer from 2 to 5, with the proviso that:

(a) at least one of the groups R and R' is always a group of formula (IV); (b) the total number of fluorine atoms present in said groups R and R' ranges from 7 to 26; and

(c) the difference in number of fluorine atoms between said groups R and R' ranges from 0 to 13. Among the metals M, ruthenium (Ru) is generally preferred.

Among the groups X, -NCS or -NCO are generally preferred.

Among the groups Y, -COOH is generally preferred.

In formula (IV), a generally preferred value of m is 3. A first preferred group of complexes is characterized by comprising the following combination of moieties: M=Ru, X = -NCS or -NCO, with the remaining substituents being as presented in the above definition of formula (I). A second preferred group of complexes is characterized by comprising the following combination of moieties: M=Ru, Y = -COOH, with the remaining substituents being as presented in the above definition of formula (I). Within the present formula (I) the moiety Y has the function of anchoring group.

A third preferred group of complexes of the invention is characterized by comprising the following combination of moieties: M=Ru, m in formula (IV) = 3, with the remaining substituents being as presented in the above definition of formula (I).

In the above formula (IV), the index m defines the length of a non-fluorinated a Iky I spacer separating the pyridine portion of the ligand L' from the fluorinated tail of R and/or R'.

In accordance with the definition of formula (I), the ligand L' always contains at least one group of formula (IV) as substituent R and/or R'; therefore the complexes of the invention are always fluorinated on the a Iky I chain(s) being part of the ligand moiety L'. An important aspect of the invention lies in the extent of overall fluorination throughout the positions R and R' , as well as in the balance of fluorination between the same two positions. In accordance with the definition of formula (I), the total number of fluorine atoms present in said groups R and R' ranges from 7 to 26, preferably from 14 to 26, or from 7 to 13; at the same time, the difference in number of fluorine atoms between said groups R and R' ranges from 0 to 13, preferably being 0; a difference of 0 means that the extent of fluorination (i.e. number of fluorine atoms) present in R and R' is the same (in that case the total number of fluorine atoms can only be an even number comprised between 14 and 26). In this situation it is even more preferred that the two substituents R and R' have identical chemical structure, i.e. they are both represented by the same formula (IV) with identical values of m, and with identical values of p. Under a further aspect, the invention relates to the following specific compounds as fluorinated metal complexes:

With molecular formula and molecular weight (MW)

1037.81 Dalton (compound of Example 1 ).

With molecular formula and molecular weight (MW)

1137.74 Dalton (compound of Example 2)

with molecular formula

and molecular weight (MW)

1337.85 Dalton (compound of Example 3).

Further preferred compounds in accordance with the invention are:

Ruthenate(2-), [[2_I2'-bipyridine]-4_l4^,-dicarboxylato(2-)-

bis(perfluoro-

]bis(thiocyanato-KN)-, dihydrogen;

A further object of the present invention is a process to prepare the complexes of formula (I). In its general definition, the process comprises the following main steps:

(a) deprotonation of 4,4'-dimethyl-2,2'-bipyridine with a strong base;

(b) reaction of the product of (a) with a iodide of formula l-(CH2)_m- (CF2)_p-CF₃ , where m and p are as defined in formula (I);

(c) complexation of the product of (b) with a metal M as defined in formula (I);

(d) reaction of the product of (c) with a [2,2'-bipyridine]-4,4'- dicarboxylic acid, 4,4'-bis alkyl ester;

(e) hydrolysis of the ester product of (d), obtaining the compound of formula (I).

In step (a), the strong base is preferably chosen from lithium diisopropylamide (LDA), lithium bis(trimethylsilyl)amide (LiHDMS), butyl lithium, fert-butyl lithium , or sodium hydride. The reaction takes place in a solvent, such as methyl tert- butyl ether, isopropyl ether, diethyl ether, tetrahydrofurane, 2- methyltetrahydrofurane, and mixtures thereof. LDA and tetrahydrofurane are preferred, respectively as strong base and solvent. This reaction is typically carried out at a temperature between -80 and 0 °C; more preferably between -78 and -10°C. In step (b), the reaction with the iodide is performed in a solvent chosen among methyl tert-butyl ether, isopropyl ether, diethyl ether, tetrahydrofurane, 2- methyltetrahydrofurane, and mixtures thereof; at temperature between -80 and +25°C; tetrahydrofurane is the preferred solvent; after the addition, the reaction is maintained under stirring for 5-8 hours. The obtained product can thus be purified by column chromatography. The purification can be performed by standard means: for example, the product of step (b) is added with water and extracted with a suitable ether such as diethyl ether, diisopropyl ether. The chromatography can be carried out in standard mode on silica gel (40-63 μ or 63-200 μ) by eluting with a binary or ternary mixture of suitable solvents chosen among methylene chloride, ethylene chloride, chloroform, methanol, ethanol, propyl alcohol and its isomer, butyl alcohol and its isomers, diethyl ether, diisopropyl ether, tetrahydrofurane, 2-methyltetrahydrofurane, in the suitable ratios. The binary mixture methylene chloride/methanol is one preferred option,. The ratio of the a.m. solvents is from 99.9/0.1 (v/v) to 98/2 (v/v) , the ratio 99.5/0.5 (v/v) is also preferred. The purified product is used for the further complexation.

In step (c) the product resulting from (b) is reacted with a suitable metal salt or complex ,such as RuCIs, [RuCI₂(p-cymene)]2, RuCI₂(DMSO) . PdCI₂, FeCI₂, FeCI₃, CoCI₂, CoCIs, ReCIs, ReCIs, RhCI₂, RhCI₃; RuCIs, [RuCI₂(p-cymene)]₂, RuCI₂(DMSO)₄, PdCI₂. [RuCI₂(p-cymene)]₂, is preferred. The reaction is carried out in a suitable dipolar aprotic solvent such as Ν,Ν-dimethylformamide, N,N- dimethylacetamide, N-dimethyplyrrolidone, sulfolane dimethyl propylene urea (DMPU); N,N-dimethylformamide in preferred. The reaction is carried out at temperature between 40 °C and the boiling point of the suitable solvent. The temperature between 50 °C and 70 °C is preferred.

In step (d), the product resulting from (c) is added with a [2,2'-bipyridine]-4,4'- dicarboxylic acid, 4,4'-bis (2-methylpropyl) ester, heated to reflux, further added with ammonium thiocyanate and maintained at reflux. The residue obtained after evaporation of the solvent can then be purified by column chromatography. The chromatography is carried out on silica gel (40-63 μ or 63-200 μ) by eluting with a binary mixture of suitable solvents chosen among methylene chloride, ethylene chloride, chloroform, methanol, ethanol , acetone, methyl ethyl ketone, diisopropyl ether, methyl tert-butyl ether, in the suitable ratios. The binary mixture methylene chloride/ methyl tert-butyl ether is preferred; a preferred ratio of the above mentioned solvents ranges from 99.5/0.5 (v/v) to 90/10 (v/v), the ratio 99/1 (v/v) being particularly preferred. In step (e) the hydrolysis of the ester product takes place in basic conditions e.g. via addition of sodium or potassium hydroxide in a solvent represented by C1 -C4 alkyl alcohol, methylene chloride, ethylene chloride, chloroform and their mixtures; methanol is preferred. The hydrolysis can be carried out between 20 °C and 40°C. The organic solvent is then evaporated to dryness and the resulting residue is taken up in water and then acidified with the suitable amount of an inorganic acid such as HNO3, HCIO₄, H2SO₄, H₃PO₄; HCIO₄ is preferred. The product of formula (I) is thus obtained.

A further object of the present invention is the use of the complexes of formula (I) as above defined as components of dye-sensitized solar cells (DSSC) and related devices. The present complexes have the function of charge transfer photosensitizers: they are typically applied, dissolved in a suitable carrier- solvent, on the surface of titanium dioxide photoanode layers in the manufacturing of photovoltaic cells. The high solubility of the present complexes in alcoholic solvents allows to dissolve and handle them in non-toxic solvents like ethanol, as a better alternative to hydrophobic solvents like CH2CI2 usable with the current photosensitizers. A further object of the invention is thus represented by a photovoltaic cell or similar device, preferably a dye-sensitized solar cell (DSSC), characterized by containing, as component thereof, a complex of formula (I) as above defined; said complexes have the function of charge transfer photosensitizers and are typically present on the surface of titanium dioxide photoanode layers of the photovoltaic cells.

The present invention is further illustrated by way of examples, which, however, should not be construed to limit the scope of the invention.

a) Synthesis of [2,2'-Bipyridine]-4,4'dicarboxyl!C acid, 4,4'-bis(2-methylpropyl) ester

2,2-Bipyridine-4,4-dicarboxylic acid (2.50 g, 10.24 mmol) was suspended in a mixture of isobutyl alcohol (25 ml_) and cone, sulfuric acid (1 .66 ml_). The mixture was heated to reflux for 24 h. The solution was then cooled to room temperature and the solvent was evaporated u.v. (40 °C/0.6 kPa)

The residue was taken up in water and a saturated aqueous solution of Na2CO3 was added until pH 8-9. A white precipitate was collected by filtration, washed with water and dried u.v (30 °C, 3.5 kPa )

2.01 of the roduct with m. .128 °C-130 °C was obtained.

5 ml_ of freshly distilled and dry THF were cooled under nitrogen to -78 °C. 2 ml_ of LDA solution in THF (2.0 M) [4 mmol] were added. Then 0.25 g [1 .35 mmol] of 4,4'-dimethyl-2,2'-bipyridine, dissolved in 5 ml of dry THF, were added under stirring. Then 0.884 g [2.73 mmol] of 1 ,1 ,1 , 2,2,3, 3-heptafluoro-5- iodopentane were added. After the addition, the reaction mixture was allowed to warm slowly to room temperature. The reaction was then added with 10 ml of water and the residue extracted with diethyl ether and purified by column chromatography (eluent dichloromethane/methanol/diethyl ether : 6/0.5/0.5 v/v). 0.14 0.248 mmol were obtained as a white solid .

c) Synthesis of Ruthenium, [4,4'-bis(2-methylpropyl) [2,2'-bipyridine]-4,4'- dicarbox late-κΝΙ κΝ1 '][4,4'-bis(perfluoro

bis(thiocyanato-KN)

c1 .) Formation of the ruthenium complex [RuCl2(p-cymene)]2 (0.1 g, 0.16 mmol) was dissolved in N,N- dimethylformamide (30 ml) and 4,4'-bis(perfluoro-

2,2'-bipyridine (0.188 g, 0.32 mmol) was then added.

The reaction mixture was heated to 60 °C for 4 h under stirring.

dicarboxylic acid, 4,4'-bis(2-methylpropyl) ester (0.1 16 g,

0.32 mmol) was added and heated to reflux for 4 h. Then ammonium thiocyanate (0.250 g; 3.27 mmol) was added to the reaction mixture and the heating continued for further 4 h. The reaction mixture was then cooled down to room temperature and the solvent removed u.v. (30 °C/0.26 kPa).

The complex was purified by silica gel column chromatography eluting with methyl tert-butyl ether/dichloromethane 2/98 (v/v). The solvent was evaporated u.v. (30 °C/2 kPa).

0.210 g of the ruthenium complex was obtained as a dark red solid.

¹H-NMR (600 MHz, CDCI₃): 9.78 (d, 1 H, J=5.4 Hz), 9.41 (d, 1 H, J=6 Hz), 8.80 (s, 1 H), 8.65 (s, 1 H), 8.20 (dd, 1 H, J=1 .8 Hz, J=4.2 Hz), 8.07 (s, 1 H), 7.93 (s, 1 H), 7.72 (d, 1 H, J=6Hz), 7.56-7.54 (m, 1 H), 7.26 (d, 2H, J=4.2 Hz), 6.85 (dd, 1 H, J=1 .8 Hz, J=4.2 Hz), 4.33-4.29 (m, 2H), 4.28-4.15 (m, 2H), 3.04 (t, 2H, J=7.2 Hz), 2.76 (t, 2H, J=8.4 Hz), 2.37-2.04 (m, 8H), 1 .1 1 (d, 6H, J=6.6 Hz), 0.99 (d, 6H, J= 6.6 Hz) ppm.

1⁹F-NMR (376.3 MHz, CDCI₃): -127.7, -127.6, -1 15.1 , -1 14.9, -80.6, -80.5 ppm. c2) Hydrolysis reaction

To a solution of the previous ruthenium complex (0.150 g, 0.128 mmol) in 9 mL of a mixture of dichloromethane/methanol 2/3 (v/v) 0.20 mL (0.512 mmol) of potassium hydroxide solution (2.5 M in MeOH) were added. The mixture was then stirred at room temperature and the solvent removed u.v. (30 °C/3 kPa)) The residue was dissolved in water and the pH of the solution was adjusted to 3.0 with 0.1 M perchloric acid. The product was precipitated and the suspension was kept at -3 °C for some hours. The solid was collected by filtration to yield 0.1 13 g of the desired compound.

¹H-NMR (600 MHz, CD₃OD): 9.61 (d, 1 H, J=5.4 Hz), 9.28 (d, 1 H, J=5.4 Hz), 9.08 (s, 1 H), 8.86 (s, 1 H), 8.54 (s, 1 H), 8.39 (s, 1 H), 8.20 (dd, 1 H, J=1 .8 Hz, J=4.2 Hz), 7.85 (d, 1 H, J=6Hz), 7.74 (d, 1 H, J=6Hz), 7.61 (dd, 1 H, J=1 .8 Hz, J=4.2 Hz), 7.42 (d, 1 H, J=6 Hz), 6.06 (dd, 1 H, J=1 .8 Hz, J=4.2 Hz), 3.07 (t, 2H, J=7.8 Hz), 2.80 (t, 2H, J=7.8 Hz), 2.43-2.36 (m, 2H), 2.21 -2.14 (m, 4H), 1 .95- 1 .89 (m, 2H) ppm.

¹⁹F-NMR (376.3 MHz, CD₃OD): -129.1 , -128.9, -1 16.3, -1 16.1 , -82.2, -82.1 ppm.

5 ml_ of freshly distilled and dry THF under nitrogen was cooled to -78 °C. 2 ml_ of LDA in THF (2.0 M) [4 mmol] was added quickly. 0.250 g [1 .35 mmol] of 4,4'- dimethyl-2,2'-bipyridine, dissolved in 5 ml of dry THF, were added and kept under stirring for 3 h. Then 1 .009 g [2.73 mmol] of 1 ,1 ,1 ,2,2,3,3,4,4-nonafluoro- 6-iodohexane were added. After the addition, the reaction mixture was allowed to warm slowly to room temperature. The reaction was added with 10 ml of water and extracted with diethyl ether and dried over Na2SO₄. Evaporation u.v. (30 °C/2.4 kPa) gave a crude product, that was recrystallized by MeOH.

0.225 g (0.33 mmol) were isolated as a white solid

¹H-NMR (300 MHz, CDCI₃): 8.61 (d, 2H, J=5.2 Hz), 8.28 (s, 2H), 7.16 (dd, 2H, J=1 .8 Hz, J=3.2 Hz), 82.81 (t, 4H, J=8 Hz), 2.07 (m, 8H) ppm.

1⁹F-NMR (282 MHz, CDCI₃): -126.0, -124.3, -1 14.3, -81 .06 ppm.

b) Synthesis of Ruthenium [4,4'-bis(2-methylpropyl) [2,2'-bipyridine]-4,4'- dicarboxylate-κΝΙ ,κΝ1 '][4,4'-bis(perfluoro-1 H,1 H,2H,2H,3H,3H-heptyl)-2,2'- bis(thiocyanato- N)

b1 .) Formation of the ruthenium complex

[RuCl2(p-cymene)]2 (0.09 g, 0.14 mmol) was dissolved in N,N- dimethylformamide (30 ml) and 4₎4^,-bis(perfluoro-

2,2'-bipyridine (0.2 g, 0.29 mmol) was then added. The reaction mixture was heated to 60 °C undernitrogen under stirring.

[2,2'-Bipyridine]-4,4'-dicarboxylic acid, 4,4'-bis(2-methylpropyl) ester (0.105 g, 0.29 mmol) was added and heated to reflux for 4 h. Then NH₄NCS (0.220 g; 2.9 mmol) was added to the reaction mixture and the heating continued for further 4 h. The reaction mixture was then cooled down to room temperature and the solvent removed u.v (30 "C/0.26 kPa ).

The complex was purified by silica gel column chromatography eluting with methyl tert-butyl ether/dichloromethane (2:98). After removal of the solvent u.v. (30 °C/ 2.4 kPa) 0.170 g of the desired compound was obtained as a dark red solid.

¹H-NMR (600 MHz, CDCI₃): 9.77 (d, 1 H, J=6 Hz), 9.38 (d, 1 H, J=6 Hz), 8.80 (s, 1 H), 8.65 (s, 1 H), 8.19 (dd, 1 H, J=1 .8 Hz, J=4.2 Hz), 8.10 (s, 1 H), 7.97 (s, 1 H), 7.71 (d, 1 H, J=5.4 Hz), 7.56-7.53 (m, 2H), 7.26 (d, 1 H, J=5.4 Hz), 6.85 (dd, 1 H, J=1 .2 Hz, J=4.8 Hz), 4.33 (sep, 2H, J=6.6 Hz), 4.15 (dd, 2H, J=1 .2 Hz, J=5.4 Hz) 3.05-3.02 (m, 2H), 2.76 (t, 2H, J=7.8 Hz), 2.24-2.05 (m, 6H), 1 .91 (q, 2H, J=8.4 Hz), 1 .1 1 (d, 6H, J=6.6 Hz), 0.99 (d, 6H, J= 6.6 Hz) ppm. b2) Hydrolysis reaction

To a solution of previous compound (0.170 g, 0.136 mmol) in 10 mL of a mixture dichloromethane/methanol 2/3 (v/v) 0.22 mL (0.544 mmol) of potassium hydroxide solution (2.5 M in MeOH) were added.

The solution was then stirred at room temperature and the solvent was removed u.v (30°C/2.6 kPa ). The residue was then dissolved in water (8 mL) and the pH of the solution was adjusted to 3.0 with 0.1 M perchloric acid.

The suspension was left at -3 °C and the solid was then collected by filtration to yield 0.148 g of the desired compound.

¹H-NMR (400 MHz, CD₃OD): 9.62 (d, 1 H, J=5.6 Hz), 9.29 (d, 1 H, J=6 Hz), 9.02 (s, 1 H), 8.87 (s, 1 H), 8.54 (s, 1 H), 8.40 (s, 1 H), 8.25 (d, 1 H, J=6 Hz), 7.86 (d, 1 H, J=5.4 Hz), 7.75 (dd, 1 H, J=1 .6 Hz, J=4.4 Hz), 7.63 (dd, 1 H, J=1 .6 Hz, J=5.6 Hz), 7.42 (d, 1 H, J=6 Hz), 7.07 (dd, 1 H, J=1 .6 Hz, J=4.4 Hz), 3.13-3.07(m, 2H), 2.82 (t, 2H, J=7.6 Hz), 2.48-2.37 (m, 2H), 2.23-2.16 (m, 4H), 1 .98-1 .90 (m, 2H) ppm.

¹⁹F-NMR (376.3 MHz, CD₃OD): -127.0, -125.3, -1 15.3, -81 .06 ppm.

a) Synthesis of 4,4'-bis(perfiuoro

15 mL of freshly distilled and dry THF under nitrogen was cooled to -78 °C. 4.0 mL of LDA in THF (1 .0 M) (4 mmol) was added quickly. 0.332 mg [1 .8 mmol] of 4,4'-dimethyl-2,2'-bipyridine, dissolved in 3 ml of dry THF, were added and kept under stirring for 30 minutes at - 78 °C, then for 15 minutes at -10 °C and finally the temperature was cooled again at -78 °C for further 15 minutes. Then 1 .896 g [4 mmol] of 1 H,1 H,2H,2H-perfluorooctyl iodide were added. After the addition, the reaction mixture was allowed to warm slowly to room temperature. The reaction was added with 20 ml of brine and extracted with diethyl ether and dried over Na2SO₄. Evaporation u.v. (30 °C/2.4 kPa) gave a crude product, that was purified by silica gel column chromatography eluting with methanol/dichloromethane solvent mixture, using an appropriate gradient (2:98 final eluting solvent mixture ratio). After removal of the solvent u.v. (30 °C/ 2.4 kPa) 0.512 g of the desired compound was obtained as a white solid.

¹H-NMR (400 MHz, CDCI₃): 8.60 (d, 2H, J=5.1 Hz), 8.28 (s, 2H), 7.16 (dd, 2H, J=1 .6 Hz, J=3.3 Hz), 2.82 (t, 4H, J=7.5 Hz), 2.21 -1 .99 (m, 8H) ppm.

1⁹F-NMR (376.3 MHz, CDCI₃): -126.1 , -123.4, -122.8, -121 .9, -1 14.1 , -80.81 ppm.

b1 .) Formation of the ruthenium complex

[RuCl2(p-cymene)]2 (0.123 g, 0.20 mmol) was dissolved in N,N- dimethylacetammide (25 ml) acid, 4,4'-

bis(2-methylpropyl) ester (0.142 g, 0.40 mmol) was then added. The reaction mixture was heated to 65 °C undernitrogen and kept under stirring for 30 min. 4,4'-bis(perfIuoro-1 H,1 H,2H,2H,3H,3H-nonyI)-2,2'-bipyndine (0.351 g, 0.40 mmol) was added and heated to reflux for 2.5 h. Then NH₄NCS (0.304 g; 4.0 mmol) was added to the reaction mixture and the heating continued for further 4 h. The reaction mixture was then cooled down to room temperature and the solvent removed u.v (100 "C/0.26 kPa ).

The complex was purified by silica gel column chromatography eluting with methyl tert-butyl ether/dichloromethane (1 :99). After removal of the solvent u.v. (30 °C/ 2.4 kPa) 0.387 g of the desired compound was obtained as a dark red solid.

1H-NMR (600 MHz, CDCI₃): 9.76 (d, 1 H, J=5.8 Hz), 9.27 (d, 1 H, J=5.6 Hz), 8.80 (s, 1 H), 8.64 (s, 1 H), 8.25 (s, 1 H), 8.17 (d, 1 H, 5.8 Hz), 8.1 1 (s, 1 H), 7.70 (d, 1 H, J=5.8 Hz), 7.52 (t, 2H, 6.2 Hz), 7.25 (d, 1 H, J=5.8 Hz), 6.85 (d, 1 H, J=6.2 Hz), 4.30 (sep, 2H, J=7.0 Hz), 4.15 (d, 2H, J=6.7 Hz), 3.03-2.99 (m, 2H), 2.74 (t, 2H, J=7.9 Hz), 2.41 -2.32 (m, 2H), 2.25-2.04 (m, 6H), 1 .87 (q, 2H, J=7.9 Hz), 1 .12 (d, 6H, J=6.7 Hz), 0.98 (d, 6H, J=6.7 Hz) ppm.

¹⁹F-NMR (376.3 MHz, CDCI₃): -126.1 , -123.3, -122.8, -121 .8, -1 14.0, -80.59 ppm. b2) Hydrolysis reaction

To a solution of previous compound (0.387 g, 0.267 mmol) in 25 mL of methanol, 0.47 mL (1 .07 mmol) of potassium hydroxide solution (2.5 M in MeOH) were added.

The solution was then stirred at room temperature for 24 hours and the solvent was removed u.v (30°C/2.6 kPa ). The residue was then dissolved in water (20 mL) and the pH of the solution was adjusted to 3.0 with 0.1 M perchloric acid. The suspension was left overnight at -3 °C and the solid was then collected by filtration to yield 0.298 g of the desired compound.

¹H-NMR (600 MHz, CD₃OD): 9.57 (d, 1 H, J=5.9 Hz), 9.22 (d, 1 H, J=5.9 Hz), 8.96 (s, 1 H), 8.82 (s, 1 H), 8.48 (s, 1 H), 8.34 (s, 1 H), 8.20 (d, 1 H, J=5.9 Hz), 7.82 (d, 1 H, J=5.9 Hz), 7.69 (d, 1 H, J=5.9), 7.58 (dd, 1 H, J=1 .5 Hz, J=4.4 Hz), 7.35 (d, 1 H, J=5.9 Hz), 7.01 (dd, 1 H, J=1 .5 Hz, J=4.4 Hz), 2.99 (t, 2H, J=7.9 Hz), 2.73 (t, 2H, J=7.9 Hz), 2.38-2.29 (m, 2H), 2.13-2.09 (m, 4H), 1 .85 (q, 2H, J=7.9 Hz) ppm. ¹⁹F-NMR (376.3 MHz, CD₃OD): -127.3, -124.3, -123.8, -122.9, -1 15.6, -82.46 ppm.

a) Synthesis of 4,4'-bis(perfluoro-1 H,1 H,2H,2H,3H,3H-octyi)-2,2'-bipyridine 18 mL of freshly distilled and dry THF under nitrogen was cooled to -78 °C. 5.0 mL of LDA in THF (1 .0 M) (5.0 mmol) was added quickly. 0.369 mg (2.0 mmol) of 4,4'-dimethyl-2,2'-bipyridine, dissolved in 2 ml of dry THF, were added and kept under stirring for 30 minutes at - 78 °C, then for 15 minutes at -10 °C and finally the temperature was cooled again at -78 °C for further 15 minutes. Then 2.120 g (5 mmol) of 1 H,1 H,2H,2H-perfluoroheptyl iodide were added. After the addition, the reaction mixture was allowed to warm slowly to room temperature. The reaction was added with 20 ml of brine and extracted with diethyl ether and dried over Na2SO₄. Evaporation u.v. (30 °C/2.4 kPa) gave a crude product, that was purified by silica gel column chromatography eluting with methanol/dichloromethane solvent mixture, using an appropriate gradient (2:98 final eluting solvent mixture ratio). After removal of the solvent u.v. (30 °C/ 2.4 kPa) 0.732 g of the desired compound was obtained as a white solid.

¹H-NMR (400 MHz, CDCI₃): 8.61 (dd, 2H, J=5.0 Hz), 8.28 (s, 2H), 7.16 (dd, 2H, J=1 .7 Hz, J=5.0 Hz), 2.81 (t, 4H, J=7.8 Hz), 2.21 -1 .99 (m, 8H) ppm.

1⁹F-NMR (376.3 MHz, CDCI₃): -126.3, -123.3, -122.7, -1 14.2, -80.80 ppm.

bis(2-methylpropyl) ester (0.164 g, 0.46 mmol) was then added. The reaction mixture was heated to 65 °C undernitrogen and kept under stirring for 30 min.

(0.357 g, 0.46 mmol) was added and heated to reflux for 2.5 h. Then NH₄NCS (0.350 g; 4.6 mmol) was added to the reaction mixture and the heating continued for further 4 h. The reaction mixture was then cooled down to room temperature and the solvent removed u.v (100 °C/0.26 kPa ).

The complex was purified by silica gel column chromatography eluting with methyl tert-butyl ether/dichloromethane (1 :99). After removal of the solvent u.v. (30 °C/ 2.4 kPa) 0.432 g of the desired compound was obtained as a mixture of both possible isomers.

¹H-NMR (600 MHz, CDCI₃): 9.78 (d, 1 H, J=5.9 Hz), 9.36 (s, 1 H), 8.80 (s, 1 H), 8.65 (s, 1 H), 8.19 (d, 1 H, J=5.9 Hz), 8.15 (s, 1 H), 8.00 (s, 1 H), 7.71 (d, 1 H, J=5.9 Hz), 7.55 (d, 1 H, 5.9 Hz), 7.53 (d, 1 H, J=5.9 Hz), 7.25 (d, 1 H, J=5.9 Hz), 6.85 (d, 1 H, J=5.9 Hz), 4.35-4.27 (m, 2H), 4.15 (d, 2H, J=6.2 Hz), 3.07-3.00 (m, 2H), 2.75 (t, 2H, J=7.9 Hz), 2.42-2.29 (m, 2H), 2.26-2.03 (m, 6H), 1 .90 (q, 2H, J=7.9 Hz), 1 .12 (d, 6H, J=6.6 Hz), 0.99 (d, 6H, J=6.6 Hz) ppm.

1⁹F-NMR (376.3 MHz, CDCI₃): -126.3, -123.5, -122.6, -1 14.0, -80.8 ppm. b2) Hydrolysis reaction

To a solution of previous compound (0.432 g, 0.320 mmol) in 25 mL of methanol, 1 .22 mL (2.56 mmol) of potassium hydroxide solution (2.5 M in MeOH) were added.

The solution was then stirred at room temperature for 48 hours and the solvent was removed u.v (30°C/2.6 kPa ). The residue was then dissolved in water (25 mL) and the pH of the solution was adjusted to 3.0 with 0.1 M perchloric acid. The suspension was left overnight at -3 °C and the solid was then collected by filtration to yield 0.348 g of the desired compound.

¹H-NMR (600 MHz, CD₃OD): 9.55 (d, 1 H, J=5.6 Hz), 9.20 (d, 1 H, J=5.6 Hz), 8.92 (s, 1 H), 8.77 (s, 1 H), 8.45 (s, 1 H), 8.32 (s, 1 H), 8.1 1 (d, 1 H, J=5.6 Hz), 7.79 (d, 1 H, J=5.9 Hz), 7.65 (d, 1 H, J=5.6), 7.52 (dd, 1 H, J=1 .5 Hz, J=5.9 Hz), 7.33 (d, 1 H, J=5.9 Hz), 6.98 (dd, 1 H, J=1 .5 Hz, J=5.9 Hz), 2.99 (t, 2H, J=7.5 Hz), 2.72 (t, 2H, J=7.9 Hz), 2.40-2.29 (m, 2H), 2.18-2.05 (m, 4H), 1 .84 (q, 2H, J=7.0 Hz) ppm. ¹⁹F-NMR (376.3 MHz, CD₃OD): -127.5, -124.6, -123.7, -1 15.2, -82.5 ppm.

Example 5 (reference product )

Synthesis of Ruthenate(2-),

methyl-4'-(perfluoro-

bis(thiocyanato-K/V)-hydrogen (1 :2)

The product was synthesized following the procedure reported by J.J. Lagref et al. in Inorganica Chimica Acta 361 (2008) 735-745) and J.J. Lagref et al. / Synthetic Metals 138 (2003) 333-339.

12 mL of freshly distilled and dry THF under nitrogen was cooled to -78 °C. 3.86 mL of LDA in THF (1 .0 M) (3.86 mmol) was added quickly. 0.542 mg (2.97 mmol) of 4,4'-dimethyl-2,2'-bipyridine, dissolved in 3 ml of dry THF, were added and kept under stirring for 30 minutes at - 78 °C, then for 15 minutes at -10 °C and finally the temperature was cooled again at -78 °C for further 15 minutes. Then 0.962 g (2.97 mmol) of 1 ,1 ,1 ,2,2,3,3-heptafluoro-5-iodopentane were added. After the addition, the reaction mixture was allowed to warm slowly to room temperature. The reaction was added with 20 ml of brine and extracted with diethyl ether and dried over Na2SO₄. Evaporation u.v. (30 °C/2.4 kPa) gave a crude product, that was purified by silica gel column chromatography eluting with methanol/dichloromethane solvent mixture, using an appropriate gradient (2:98 final eluting solvent mixture ratio). After removal of the solvent u.v. (30 °C/ 2.4 kPa) 0.478 g of the desired compound was obtained as a white solid. ¹H-NMR (300 MHz, CDCI₃): 8.60 (d, 1 H, J=5.0 Hz), 8.54 (d, 1 H, J=5.0 Hz), 8.25 (s, 2H), 7.15 (dd, 2H, J=1 .6 Hz, J=5.0 Hz), 2.80 (t, 2H, J=7.2 Hz), 2.44 (s, 3H), 2.24-1 .98 (m, 4H) ppm.

¹⁹F-NMR (376.3 MHz, CDCI3): -127.7, -1 15.1 , -80.58 ppm.

[RuCl2(p-cymene)]2 (0.193 g, 0.315 mmol) was dissolved in N,N- dimethylacetammide (30 ml) and [2,2'-Bipyridine]-4,4'-dicarboxylic acid, 4,4'- bis(2-methylpropyl) ester (0.225 g, 0.63 mmol) was then added. The reaction mixture was heated to 65 °C undernitrogen and kept under stirring for 30 min.

mmol) was added and heated to reflux for 2.5 h. Then NH₄NCS (0.480 g; 6.3 mmol) was added to the reaction mixture and the heating continued for further 4 h. The reaction mixture was then cooled down to room temperature and the solvent removed u.v (100 °C/0.26 kPa ).

The complex was purified by silica gel column chromatography eluting with methyl tert-butyl ether/dichloromethane (1 :99). After removal of the solvent u.v. (30 °C/ 2.4 kPa) 0.417 g of the desired compound was obtained as a mixture of both possible isomers (dark red solid).

¹H-NMR (400 MHz, CDCI₃): 9.79 (d, 2H, J=6.5 Hz), 9.35 (d, 1 H, J=5.6 Hz), 9.30 (d, 1 H, J=5.6 Hz), 8.79 (s, 2H), 8.64 (s, 2H), 8.20 (d, 2H, J=6.1 Hz), 8.10 (s, 2H), 7.96 (d, 2H, J=5.0 Hz), 7.70 (t, 2H, J=6.7 Hz), 7.55 (td, 2H, J=1 .6 Hz, J=5.6 Hz,), 7.49 (t, 2H, J=6.2 Hz), 7.24 (d, 1 H, J=6.2 Hz), 7.16 (d, 1 H, J=5.8 Hz), 6.82 (d, 2H, J=5.6 Hz), 4.35-4.26 (m, 4H), 4.19-4.13 (m, 4H), 3.04-2.96 (m, 2H), 2.72 (t, 2H, J=7.8 Hz), 2.66 (s, 3H), 2.40 (s, 3H), 2.30-2.01 (m, 8H), 1 .89 (q, 4H, J=7.8 Hz), 1 .12 (d, 12H, J=6.7 Hz), 0.99 (d, 12H, J=6.7 Hz) ppm. 1⁹F-NMR (376.3 MHz, CDCI3): -127.5, -1 14.8, -80. 43 ppm. b2) Hydrolysis reaction To a solution of previous compound (0.417 g, 0.44 mmol) in 25 ml_ of ethanol, 0.83 ml_ (1 .75 mmol) of potassium hydroxide solution (2.5 M in EtOH) were added.

The solution was then stirred at room temperature for 24 hours and the solvent was removed u.v (30°C/2.6 kPa ). The residue was then dissolved in water (25 ml_) and the pH of the solution was adjusted to 3.0 with 0.1 M perchloric acid. The suspension was left overnight at -3 °C and the solid was then collected by filtration to yield 0.369 g (mixture of both isomers) of the desired compound. 1H-NMR (600 MHz, CD₃OD): 9.58 (d, 2H, J=5.9 Hz), 9.22 (d, 1 H, J=5.6 Hz), 9.16 (d, 1 H, J=5.6 Hz), 8.96 (s, 2H), 8.81 (s, 2H), 8.43 (s, 2H), 8.29 (s, 2H), 8.21 (d, 2H, J=5.6 Hz), 7.83-7.80 (m, 2H), 7.68 (d, 1 H, J=6.1 ), 7.63 (d, 1 H, J=5.7 Hz), 7.58 (t, 2H, J=5.7 Hz), 7.35 (d, 1 H, J=5.7 Hz), 7.27 (d, 1 H, J=6.5 Hz), 7.00 (d, 1 H, J=6.1 Hz), 6.95 (d, 1 H, J=6.1 Hz), 3.01 (t, 2H, J=7.5 Hz), 2.75 (t, 2H, J=7.5 Hz), 2.65 (s, 3H), 2.38 (s, 3H), 2.37-2.27 (m, 2H), 2.18-2.06 (m, 4H), 1 .91 -1 .83 (m, 2H) ppm.

¹⁹F-NMR (376.3 MHz, CD₃OD): -129.0, -1 16.1 , -82.18 ppm.

12 mL of freshly distilled and dry THF under nitrogen was cooled to -78 °C. 2.5 mL of LDA in THF (1 .0 M) (2.5 mmol) was added quickly. 0.387 mg (2.1 mmol) of 4,4'-dimethyl-2,2'-bipyridine, dissolved in 3 ml of dry THF, were added and kept under stirring for 30 minutes at - 78 °C, then for 15 minutes at -10 °C and finally the temperature was cooled again at -78 °C for further 15 minutes. Then 1 .026 g (2.1 mmol) of 1 H,1 H,2H,2H-perfluorooctyl iodide were added. After the addition, the reaction mixture was allowed to warm slowly to room temperature. The reaction was added with 20 ml of brine and extracted with diethyl ether and dried over Na2SO₄. Evaporation u.v. (30 °C/2.4 kPa) gave a crude product, that was purified by silica gel column chromatography eluting with methanol/dichloromethane solvent mixture, using an appropriate gradient (2:98 final eluting solvent mixture ratio). After removal of the solvent u.v. (30 °C/ 2.4 kPa) 0.798 g of the desired compound was obtained as a white solid.

1H-NMR (300 MHz, CDCI₃): 8.60 (dd, 1 H, J=5.0 Hz), 8.54 (d, 1 H, J=5.0 Hz), 8.25 (s, 2H), 7.15 (dd, 2H, J=1 .7 Hz, J=5.0 Hz), 2.81 (t, 2H, J=7.6 Hz), 2.45 (s, 3H), 2.22-1 .99 (m, 4H) ppm.

¹⁹F-NMR (376.3 MHz, CDCI₃): -126.1 , -123.4, -122.8, -121 .9, -1 14.1 , -80.80 ppm. b) Synthesis of Ruthenium [4,4'-bis(2-methylpropyl) [2,2'-bipyridine]-4,4'- dicarboxylate-κΝΙ ,κΝ1 '][4-methyl-4'-(perfluoro-1 H,1 H,2H,2H,3H,3H-nonyl)-2,2'- bipyridine-KN¹ ,KN^{1 '}]bis(thiocyanato-KN)

b1 .) Formation of the ruthenium complex

[RuCl2(p-cymene)]2 (0.214 g, 0.35 mmol) was dissolved in N,N- dimethylacetamide (35 ml) and [2,2'-Bipyridine]-4,4'-dicarboxylic acid, 4,4'- bis(2-methylpropyl) ester (0.250 g, 0.70 mmol) was then added. The reaction mixture was heated to 65 °C undernitrogen and kept under stirring for 30 min.

mmol) was added and heated to reflux for 2.5 h. Then NH₄NCS (0.532 g; 7.0 mmol) was added to the reaction mixture and the heating continued for further

4 h. The reaction mixture was then cooled down to room temperature and the solvent removed u.v (100 °C/0.26 kPa ).

The complex was purified by silica gel column chromatography eluting with methyl tert-butyl ether/dichloromethane (1 :99). After removal of the solvent u.v. (30 °C/ 2.4 kPa) 0.480 g of the desired compound was obtained as a mixture of both possible isomers

¹H-NMR (400 MHz, CDCI₃): 9.79 (d, 2H, J=6.3 Hz), 9.35 (d, 1 H, J=5.7 Hz), 9.29 (d, 1 H, J=5.7 Hz), 8.79 (s, 2H), 8.64 (s, 2H), 8.20 (dd, 2H, J=1 .7 Hz, J=5.7 Hz), 8.1 1 (s, 2H), 7.97 (d, 2H, J=6.1 Hz), 7.70 (t, 2H, J=5.0 Hz), 7.55 (dd, 2H, J=1 .7 Hz, J=5.7 Hz), 7.49 (t, 2H, 6.3 Hz), 7.24 (d, 1 H, J=5.7 Hz), 7.16 (d, 1 H, J=6.1 Hz), 6.83 (d, 2H, J=6.3 Hz), 4.35-4.26 (m, 4H), 4.19-4.12 (m, 4H), 3.00 (t, 2H, J=7.7 Hz), 2.73 (t, 2H, J=7.7 Hz), 2.65 (s, 3H), 2.40 (s, 3H), 2.34-2.01 (m, 8H), 1 .89 (q, 4H, J=7.7 Hz), 1 .12 (d, 12H, J=6.7 Hz), 0.99 (d, 12H, J=6.7 Hz) ppm. ¹⁹F-NMR (376.3 MHz, CDCI₃): -126.1 , -123.3, -122.8, -121 .8, -1 13.9, -80.79 ppm. b2) Hydrolysis reaction

To a solution of previous compound (0.360 g, 0.326 mmol) in 25 ml_ of ethanol, 1 .22 ml_ (2.61 mmol) of potassium hydroxide solution (2.5 M in EtOH) were added.

The solution was then stirred at room temperature for 48 hours and the solvent was removed u.v (30°C/2.6 kPa ). The residue was then dissolved in water (25 ml_) and the pH of the solution was adjusted to 3.0 with 0.1 M perchloric acid. The suspension was left overnight at -3 °C and the solid was then collected by filtration to yield 0.299 g (mixture of both isomers) of the desired compound. 1H-NMR (600 MHz, CD₃OD): 9.57 (d, 2H, J=5.9 Hz), 9.21 (d, 1 H, J=5.9 Hz), 9.16 (d, 1 H, J=5.9 Hz), 8.95 (s, 2H), 8.79 (s, 2H), 8.42 (s, 2H), 8.28 (s, 2H), 8.18 (d, 2H, J=5.6 Hz), 7.79 (d, 1 H, J=6.5 Hz), 7.75 (d, 1 H, J=6.5 Hz), 7.61 (d, 2H, J=5.6), 7.56 (d, 2H, J=6.5 Hz), 7.34 (d, 1 H, J=6.1 Hz), 7.27 (d, 1 H, J=6.1 Hz), 6.99 (d, 1 H, J=6.1 Hz), 6.94 (d, 1 H, J=6.1 Hz), 3.00 (t, 2H, J=7.2 Hz), 2.74 (t, 2H, J=7.6 Hz), 2.64 (s, 3H), 2.37 (s, 3H), 2.37-2.27 (m, 2H), 2.22-2.08 (m, 4H), 1 .90-1 .82 (m, 2H) ppm.

1⁹F-NMR (376.3 MHz, CD₃OD): -127.3, -124.3, -123.9, -122.9, -1 15.1 , -82.44 ppm.

a) Synthesis of 4-methyl-4'-(perfluoro-1 H,1 H,2H,2H,3H,3H-octyl)-2,2'-bipyridine 15 mL of freshly distilled and dry THF under nitrogen was cooled to -78 °C. 3.0 mL of LDA in THF (1 .0 M) (3.0 mmol) was added quickly. 0.460 mg (2.5 mmol) of 4,4'-dimethyl-2,2'-bipyridine, dissolved in 3 ml of dry THF, were added and kept under stirring for 30 minutes at - 78 °C, then for 15 minutes at -10 °C and finally the temperature was cooled again at -78 °C for further 15 minutes. Then 1 .060 g (2.5 mmol) of 1 H,1 H,2H,2H-perfluoroheptyl iodide were added. After the addition, the reaction mixture was allowed to warm slowly to room temperature. The reaction was added with 20 ml of brine and extracted with diethyl ether and dried over Na2SO₄. Evaporation u.v. (30 "C/2.4 kPa) gave a crude product, that was purified by silica gel column chromatography eluting with methanol/dichloromethane solvent mixture, using an appropriate gradient (2:98 final eluting solvent mixture ratio). After removal of the solvent u.v. (30 °C/ 2.4 kPa) 0.782 g of the desired compound was obtained.

1H-NMR (400 MHz, CDCI₃): 8.60 (d, 1 H, J=5.0 Hz), 8.54 (d, 1 H, J=5.0 Hz), 8.25 (s, 2H), 7.15 (d, 2H, J=5.0 Hz), 2.80 (t, 2H, J=7.5 Hz), 2.45 (s, 3H), 2.21 - 1 .99 (m, 4H) ppm.

¹⁹F-NMR (376.3 MHz, CDCI₃): -126.5, -123.6, -122.5, -1 14.3, -80.81 ppm. b) Synthesis of Ruthenium [4,4'-bis(2-methylpropyl) [2,2'-bipyridine]-4,4'- dicarboxylate-κΝΙ ,κΝ1 '][4-methyl-4'-(pernuoro-1 H,1 H,2H,2H,3H,3H-octyl)-2,2'-

b1 .) Formation of the ruthenium complex

[RuCl2(p-cymene)]2 (0.233 g, 0.38 mmol) was dissolved in N,N- dimethylacetamide (35 ml) and [2,2'-Bipyridine]-4,4'-dicarboxylic acid, 4,4'- bis(2-methylpropyl) ester (0.271 g, 0.76 mmol) was then added. The reaction mixture was heated to 65 °C undernitrogen and kept under stirring for 30 min.

mmol) was added and heated to reflux for 2.5 h. Then NH₄NCS (0.579 g; 7.6 mmol) was added to the reaction mixture and the heating continued for further 4 h. The reaction mixture was then cooled down to room temperature and the solvent removed u.v (100 °C/0.26 kPa ).

The complex was purified by silica gel column chromatography eluting with methyl tert-butyl ether/dichloromethane (1 :99). After removal of the solvent u.v. (30 °C/ 2.4 kPa) 0.557 g of the desired compound was obtained as a mixture of both possible isomers.

¹H-NMR (400 MHz, CDCI₃): 9.79 (d, 2H, J=5.9 Hz), 9.33 (d, 1 H, J=5.6 Hz), 9.27 (d, 1 H, J=5.6 Hz), 8.79 (s, 2H), 8.64 (s, 2H), 8.19 (dd, 2H, J=1 .6 Hz, J=5.9 Hz), 8.13 (s, 2H), 7.99 (d, 2H, J=7.1 Hz), 7.69 (t, 2H, J=7.9 Hz), 7.54 (tod, 2H, J=1 .8 Hz, J=5.9 Hz), 7.51 -7.46 (m, 2H), 7.24 (d, 1 H, J=5.9 Hz), 7.16 (d, 1 H, J=5.9 Hz), 6.85-6.80 (m, 2H), 4.35-4.25 (m, 4H), 4.19-4.12 (m, 4H), 3.00 (t, 2H, J=7.7 Hz), 2.72 (t, 2H, J=7.7 Hz), 2.64 (s, 3H), 2.39 (s, 3H), 2.42-2.01 (m, 8H), 1 .88 (q, 4H, J=7.7 Hz), 1 .12 (d, 12H, J=6.8 Hz), 0.99 (d, 12H, J=6.8 Hz) ppm.

¹⁹F-NMR (376.3 MHz, CDCI₃): -126.3, -123.5, -122.7, -1 13.9, -80.77 ppm. b2) Hydrolysis reaction

To a solution of previous compound (0.367 g, 0.367 mmol) in 35 mL of methanol, 1 .38 mL (2.94 mmol) of potassium hydroxide solution (2.5 M in MeOH) were added.

The solution was then stirred at room temperature for 48 hours and the solvent was removed u.v (30°C/2.6 kPa ). The residue was then dissolved in water (20 mL) and the pH of the solution was adjusted to 3.0 with 0.1 M perchloric acid. The suspension was left overnight at -3 °C and the solid was then collected by filtration to yield 0.310 g (mixture of both isomers) of the desired compound. ¹H-NMR (600 MHz, CD₃OD): 9.57 (d, 2H, J=6.2 Hz), 9.22 (d, 1 H, J=5.9 Hz), 9.16 (d, 1 H, J=6.2 Hz), 8.95 (s, 2H), 8.80 (s, 2H), 8.43 (s, 2H), 8.28 (d, 2H, J=5.0 Hz), 8.19 (d, 2H, J=5.9 Hz), 7.80 (d, 1 H, J=5.9 Hz), 7.75 (d, 1 H, J=5.9 Hz), 7.59 (dd, 2H, J=1 .7, J=5.9), 7.57 (tod, 2H, J=1 .7 Hz, J=6.5 Hz), 7.34 (d, 1 H, J=5.9 Hz), 7.27 (d, 1 H, J=5.9 Hz), 6.99 (d, 1 H, J=7.1 Hz), 6.94 (d, 1 H, J=7.1 Hz), 3.00 (t, 2H, J=7.1 Hz), 2.74 (t, 2H, J=7.1 Hz), 2.64 (s, 3H), 2.36 (s, 3H), 2.42-2.30 (m, 2H), 2.18-2.07 (m, 4H), 1 .90-1 .82 (m, 2H) ppm.

1⁹F-NMR (376.3 MHz, CD₃OD): -127.3, -124.3, -123.9, -122.9, -1 15.1 , -82.44 ppm. Example 9 Photovoltaic devices production and testing

A set of photovoltaic devices based on the sensitization of different dye molecules were fabricated as described in the following. The dye-sensitized solar cells (DSSC) have a sandwich-like form, composed by a couple of fluorine-doped tin oxide (FTO) conductive glasses (Pilkington TEC-15, 4 mm thick). The back glass was previously drilled (1 mm diameter) for successive dye flowing and electrolyte injection. The glasses were cleaned with a neutral cleaner (Carlo Erba Ausilab 101 ), sonicated and washed with ethanol, dried and then screen printed with a glass frit paste (patent WO2012035565) as perimetral sealant. After drying, a photo-anode layer (active area 1 ,95 cm²) was screen printed on the front glass using a titanium dioxide paste (Dyesol 18NR- T), while a cathode layer was screen printed on the back glass using a commercial nano platinum paste. The two glasses were sintered in a convection oven (Nabertherm N120/65HAC) up to 450-500°C with a ramp of 2°C/min; subsequently the thickness of the anode is measured with a contact profilometer (KLA Tencor P-10). The thickness of semitransparent T1O2 layer is about 6-7 μm after sintering. After that, the anode and the cathode substrates are overlapped and sealed together in a custom thermo-press by melting the glass frit sealant at 480-520°C with a ramp of 3°C/min (FIG. 1 ). The cell gap spacing after sealing is about 20-30 microns. Different dye solutions were prepared and flushed through the holes for 90 min at 60°C using a syringe pump, as described later. After the impregnation process, the cell were filled with a commercial electrolyte (Dyesol, UHSE), injected with a syringe. Finally, the holes were sealed with a UV-curable resin. All the fluorinated dyes described in Example 1 .Example 2 , Example 3 and the Example 5 (comparison product described by Lagref et al.) were dissolved in ethanol at a concentration of 0.15 mM. The dye solutions were prepared adding the solvent, the magnetic stir at the powder in a dried bottle. The mixtures were sonicated for 10 minutes and stirred at room temperature overnight. Four different DSSC were fabricated for each dye solution. Only average values for each group of cells is give in the following.

The photovoltaic properties of the small DSSC were measured using a Solar Simulator (100 mW cm^"2, AM 1 .5 G filter, Abet Technologies Sun 2000). I-V curves were obtained with by a source meter (Model 2602, Keithley Instruments, Inc.), both at 0 h and after 1000 h of accelerated aging at 85 °C and RH 15% in a climatic chamber (Votsch VCL 4006). The efficiency, η, is the percentage of the incident solar energy that is converted into electrical energy, given by the formula

where the Voc is the open circuit voltage, Isc is the short circuit current, FF is the fill factor, P is the incident luminous power. The trends of the relevant electrical parameters over accelerated aging time up to 1000 h are reported in TABLE 1 (efficiency, open circuit voltage, short circuit current density and fill factor, respectively).

Table 1: accelerated aging test results on DSSC containing a complex of the present invention (Ex. 1, 2, 3, 4, 6, 7, 8) or reference complex (Ex. 5).

The data in Table 1 show that the complexes in accordance with the present invention substantial maintained all cell-related performance parameters (efficiency, open circuit voltage, short circuit current, fill factor) in comparison with the reference example 5 and throughout the accelerated aging test.

Interestingly, the high-extent fluorination of compounds of Examples 1 ,2,3,4 did not significantly reduce the cell efficiency parameters: this is remarkable since a high fluorination of the alkyl chain attached to the ligand was previously associated to a reduction of cell efficiency parameters (Inorganica Chimica Acta,2008 (361), 735; Synthetic Metals,2003 (138), 333). Interesting results also emerge from the aging measurements at 1000 hours: compared to the reference example 5, the tested compounds showed a substantial maintenance or even a slight increase of performance; particularly noteworthy is the performance of the compound of examples 6,7 which, despite a reduction in the fluorine load compared to the reference example 5, did not develop a

significantly higher long-term instability.

Example 10 Solubility testing

Solubility was assessed by measuring the intensity of the NMR signal of saturated solutions of the test compounds. The saturated solutions were prepared by dissolving, in a closed vial, an excess of the test compound (1 1 .5 μιτιοΙ) in 0.500 ml_ of ethanol-_d6, followed by stirring for 30 minutes; then, upon rest and layering of the precipitate at the bottom of the vial, 0.400 ml_ of the resulting clear solution were transferred into the NMR tube. The tube was further added with 2.16 pinoles of maleic acid inhternal standard (dissolved in 0.050 ml_ of ethanol-_d6), additional 0.200 ml_ of ethanol-_d6 and subjected to NMR testing.

For each sample a preliminary screening of the recycle delay time was performed (d1 , with d1 = 1 ,5,10 and 20 s), in order to maximize the ratio between the integral of the aromatic signals of the test compound and of the maleic acid, obtaining the best S/N ratio. All tested samples showed no further improvements were observed beyond d1 =10.

Subsequently, for each test compound (dye), three measurements of the same sample were taken, using the same parameters (nt=64, bs=4, d1 =10): the ratio was then measured between the integrals of the aromatic signals of an aromatic proton of the test compound (average value of the three

measurements) and of two protons of the internal maleic acid standard (ma). The obtained results are summarized in the following TABLE 2.

The values shown in last right column of the table give an indication of the relative solubility of the test compounds with respect to the reference

compound of example 5: these data clearly show that, despite the close similarity in degree of fluorination, there is an unexpected extent of increase in solubility in ethanol when moving from the reference compound of example 5 (wherein R = CH3 and R' = formula (IV) with m=3 and p= 7) to the closest compound of the invention in accordance with Example 7 (wherein R = CH3 and R' = formula (IV) with m=3 and p= 5). Even higher solubility values were found for the bis-fluorinated compounds of examples 3 and 4; this is particularly unexpected, since an increase in fluorination was generally assumed to increase the hydrophobicity of the compounds.

Overall the present data in tables 1 and 2 support that the compounds of the present invention, unexpectedly from what known in this field, are highly efficient charge transfer photosensitizers, advantageously endowed with long- term stability and enhanced solubility in polar solvents.

Claims

1 . Fluorinated metal complexes of formula (I):

wherein:

M is a metal selected from Ru, Pd, Fe, Co, Rh or Re; the two X groups are, independently of each other: -SCN, -NCS, -CN, or -NCO;

L is a ligand of formula (II),

in which the Y groups are, independently of each other: -COOH, -

L' is a ligand of formula (III)

where the groups R and R', independently of each other are: H, C₁ -9 alkyl , -O-C1-9 alkyl , or a group of formula (IV)

where m is 2 or 3 and p is an integer from 2 to 5; with the proviso that:

(a) at least one of R and R' is always a group of formula (IV);

(b) the total number of fluorine atoms present in said R and R' ranges from 7 to 26; and

(c) the difference in number of fluorine atoms between said R and R' ranges from 0 to 13.

Complexes according to claim 1 , wherein one or more of the following conditions applies: M is selected from Ru; X is selected from -NCS or - NCO; Y is selected from -COOH.

Complexes according to any of claims 1 -2 wherein, in formula (IV), m is 3.

Complexes according to any of claims 1 -3 wherein the total number of fluorine atoms present in said R and R' ranges from 14 to 26 or from 7 to 13.

Complexes according to any of claims 1 -4, wherein both R and R', are a group of formula (IV) whose corresponding indexes m may be equal or different from each other, and whose corresponding indexes p may be equal or different from each other.

6. Complexes according to any of claims 1 -5 wherein the difference in number of fluorine atoms between said R and R' is 0.

7. Complexes according to any of claims 1 -6, wherein R and R' have identical structure.

8. Complexes according to any of claims 1 -7, selected from:

or one among the following:

9. A process to manufacture a complex of formula (I) as described in any of claims 1 -8, comprising the following steps:

(a) deprotonation of 4,4'-dimethyl-2,2'-bipyridine with a strong base; (b) reaction of the product of (a) with a iodide of formula l-(CH₂)_m- (CF2)_P-CF3, where m and p are as defined in claim 1 ;

(c) complexation of the product of (b) with a metal M as defined in claim 1 ;

10. Process accoding to claim 9, wherein in step (a) the strong base is

selected from lithium diisopropylamide (LDA), lithium

bis(trimethylsilyl)amide (LiHDMS), butyl lithium, tert-butyl lithium , or sodium hydride and the deprotonation is preformed in a polar solvent chosen from diethyl ether, tetrahydrofurane, 2-methyltetrahydrofurane or mixtures thereof, at a temperature between -80 and 0 °C.

1 1 .Process according to claims 9-10, wherein in step (b) the reaction with the iodide is performed in a solvent chosen among methyl tert-butyl ether, isopropyl ether, diethyl ether, tetrahydrofurane, 2- methyltetrahydrofurane or mixtures thereof, at a temperature between -80 and 25°C, followed by purification of the resulting product.

12. Process according to claims 9-1 1 , wherein in step (c) the product resulting from (b) is reacted with a metal salt or complex chosen from RuCIs, [RuCI₂(p-cymene)]2, RuCI₂(DMSO) . PdCI₂, FeCI₂, FeCIs, CoCI₂, CoCIs, ReCIs, ReCIs, RhCI₂, RhCI₃; RuCIs, [RuCI₂(p-cymene)]₂, RuCI₂(DMSO)₄, and PdCI₂; in a dipolar aprotic solvent solvent chosen from N,N-dimethylformamide, N,N-dimethylacetamide, N- methylpyrrolidone, sulfolane, dimethyl propylene urea (DMPU) and mixtures thereof; at a temperature between 40 °C and the boiling point of said solvent.

13. Process according to clams 9-12, wherein in step (d) the product resulting from (c) is reacted with with [2,2'-bipyridine]-4,4'-dicarboxylic acid, 4,4'-bis (2-methylpropyl) ester, heated to reflux and added with ammonium thiocyanate, followed by purification of the resulting product.

14. Process according to claims 9-13, wherein in step (e) the ester product obtained in (d) is hydrolyzed with sodium or potassium hydroxide in a solvent chosen from a C1 -C4 alkyl alcohol, methylene chloride, ethylene chloride, chloroform and their mixtures, ad a temperature between 20 and 40°C.

15. Use of a complex as described in claims 1 -8, as charge transfer photosensitizer.

16. Use according to claim 15, in the manufacturing of photovoltaic cells, in particular dye-sensitized solar cells (DSSC)..

17. Photovoltaic cell, in particular dye-sensitized solar cell, containing a complex as described in claims 1 -8.