JP2009234915A - Compound or its salt, method of producing the same, aromatic azo compound, and fluorescent material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluorescent substance that has excellent characteristics and is expected to be used in a variety of applications. <P>SOLUTION: It has been discovered that a family of aromatic azo compounds (azoarene derivatives) exhibit a high fluorescence quantum yield. In particular, [2-(4-methoxyphenylazo)phenyl]bis(pentafluorophenyl)borane which is an azobenzene derivative, exhibits the historically highest fluorescence quantum yield of 0.99 in a room-temperature solution. A variety of research works have been carried out to date on azobenzene derivatives, and a number of synthetic methods therefor have been established. A useful fluorescent material can be provided thanks to it that versatility and simplicity of synthesis methods of the azobenzene derivatives can be succeeded and the fluorescence wavelength is easily controlled. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a compound or a salt thereof and a production method thereof, particularly an aromatic azo compound and a fluorescent material.

The fluorescent material is important as a light emitting material, a fluorescent probe, and a molecular recognition material. In particular, organic fluorescent materials are attracting attention because they easily change their properties. For example, tris (8-hydroxyquinoline) aluminum and many other organic molecules are used as light-emitting elements in organic light-emitting diodes (OLEDs) that cause electroluminescence (EL) for display applications. ing. As another example, dye molecules such as rhodamine and fluorescein, which are known to have high luminous efficiency, are used for biolabeling for protein detection.

On the other hand, azobenzene which is an aromatic azo compound (azoarene derivative) is one of the most common dye materials. Azo dyes such as Orange II and Congo Red are also azobenzene. Azo dyes account for about half of the global dye production.

However, in general, azobenzene emits little light and does not emit fluorescence. When azobenzene is photoexcited, radiation deactivation is sufficiently slow, and thus non-radiation deactivation or photoisomerization proceeds. Therefore, azobenzene may be used as a photoresponsive molecular switch by utilizing the latter photoisomerization property. For example, catecholborane having an azo group as an intramolecular ligand has been synthesized by the present inventors, and the characteristics of a photoresponsive molecular switch by photoisomerization have been reported.

"Photoswitching of the Lewis Acidity of a Catecholborane Bearing an Azo Group Based on the Change in Coordination Number of Boron" N. Kano, J. Yoshino, and T. Kawashima, Org. Lett., 7, 3909-3911 (2005).

The present invention has been made in view of the above-described background art, and an object thereof is to provide a fluorescent substance having excellent characteristics.

According to this invention, in order to achieve the above-mentioned object, the configuration as described in the claims is adopted. Hereinafter, the present invention will be described in detail.

The first aspect of the present invention is:
formula
[Where:
X and Y may have a substituent, and may be a condensed aromatic ring,
Ar ₁ and Ar ₂ are C ₆ F ₅ . ]
Or a salt thereof.

According to this configuration, a fluorescent material having excellent characteristics can be obtained.

The second aspect of the present invention is
A reaction between a metallized aromatic azo compound and a boron-containing compound
[Where:
X and Y may have a substituent, and may be a condensed aromatic ring,
Ar ₁ and Ar ₂ are C ₆ F ₅ . ]
In the manufacturing method of the compound or its salt which manufactures the compound or its salt represented by these.

According to this configuration, a fluorescent material having excellent characteristics can be obtained with few steps.

Examples of the aromatic ring include a benzene ring, a condensed benzene ring, a thiophene, and a pyridine ring.

Examples of the substituent include (i) alkyl group, (ii) alkoxy group, (iii) alkylthio group, (iv) dialkylamino group, (v) pyrrolidino group, (vi) piperidino group, (vii) morpholino Group, (viii) aryl group, (ix) aryloxy group, (x) hydroxy group, (xi) amino group, (xii) monoalkylamino group, (xiii) acylamino group, (xiv) acyloxy group, (xv) An alkylsulfonylamino group or hydrogen is mentioned. (x) hydroxy group, (xi) amino group, (xii) monoalkylamino group, (xiii) acylamino group, (xiv) acyloxy group, (xv) alkylsulfonylamino group are functional groups after protection-deprotection or synthesis. It may be introduced into the aromatic ring by group conversion or the like. The number of carbon atoms of the substituent is preferably 1 to 22, more preferably 1 to 6.

The third aspect of the present invention is
Excited state ¹ (n, ^{π *)} excited state energy level lower than ^{1 (π, π *)} has, aromatic azo compound and at least one NNCC dihedral angle is fixed It is in.

According to this configuration, a fluorescent material having excellent characteristics can be obtained due to the N-N-C-C dihedral angle being fixed by a chemical bond or the like.

According to the present invention, a fluorescent material having excellent characteristics can be obtained.

Other objects, features, or advantages of the present invention will become apparent from the detailed description based on the embodiments of the present invention described later and the accompanying drawings.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[Synthesis method]

Various compounds were synthesized according to the following scheme.

Boron-substituted azobenzene derivatives were synthesized by nucleophilic substitution reaction on boron reagent with 2-lithioazobenzene. As is apparent from the scheme, this synthesis method is superior to conventional synthesis methods in that it is a one-pot, one-step process.

First, fluorobis (pentafluorophenyl) borane (2a) was prepared by reacting BF ₃ .OEt ₂ with pentafluorophenyl magnesium bromide. Next, for (E) -2-iodoazobenzene ((E) -1), n-butyllithium (1.10 equivalent) and fluorobis (pentafluorophenyl) borane (2a) in ether at −112 ° C. (1.10 equivalents) were sequentially reacted to synthesize bis (pentafluorophenyl) [2- (phenylazo) phenyl] borane ((E) -3a) as a stable brown solid in air in a yield of 28%.

Bis (4-fluorophenyl) [2- (phenylazo) phenyl] borane ((E) -3b) was prepared in the same manner from compound (E) -1 and bis (4-fluorophenyl) isopropoxyborane ((E ) -2b) in 31% yield.

Furthermore, [2- (4-methoxyphenylazo) phenyl] bis (pentafluorophenyl) borane ((E) -3c) is also represented by (E) -2-iodo-4′-methoxyazobenzene ((E) -4) And compound (E) -2a was synthesized in 27% yield.

[Crystal structure, coordination number]

In the 11B NMR spectrum in CDCl ₃ , compound (E) -3a-c showed a broad peak in the region of the tetracoordinate boron compound, so that compound (E) -3a-c was 4 in solution. It was found to be a coordinated boron compound.

FIG. 1 is an ORTEP diagram of compound (E) -3a. The crystal structure of compound (E) -3a was determined by X-ray crystal structure analysis. Judging from N2-B1 bond length [1.625 (2) Å] and bond angle around boron [95.53 (12) -117.93 (13) °], (E) -3a has N2-B1 bond, It was found that it has a distorted tetrahedral structure centered on boron. The bond length of the N2-B1 coordination bond is the shortest among the BN bond lengths that have been reported so far to form a five-membered ring [range of data stored in the Cambridge Structural Database: 1.625-1.842Å]. Is a class of things. The N1-N2 bond length [1.2704 (18) Å] is almost the same as the average value (1.25Å) of (E) -azobenzene derivatives reported in the past, which clearly shows that it is a double bond.

The bond length (Å) and bond angle (deg) as found from this X-ray crystal structure analysis were as follows. N1-N2, 1.2704 (18); B1-N2, 1.625 (2); B1-C1, 1.599 (2); B1-C13, 1.629 (2); B1-C19, 1.627 (2); C1-B1-C13 , 117.74 (13); C1-B1-C19, 106.04 (13); C13-B1-C19, 117.93 (13); C1-B1-N2, 95.53 (12); C13-B1-N2, 105.07 (12); C19-B1-N2, 112.35 (13).

[Spectral properties, molecular orbitals involved in fluorescence]

Figure 2 shows (A) the absorption spectrum and fluorescence spectrum of compound (E) -3a in hexane at room temperature (excitation at 386 nm), (B) compound (E) -3a in an environment irradiated with light of 360 nm from the left side. (C) Absorption spectrum and fluorescence spectrum of compound (E) -3c in hexane at room temperature (excitation at 439 nm), (D) In an environment irradiated with 360 nm light from the left side 2 is a photograph of a hexane solution (about 5 μM) of compound (E) -3c.

In the ultraviolet-visible absorption spectrum in hexane, Compound (E) -3a exhibited the maximum absorption wavelength attributed to the π-π ^* transition of the azo group at 386 nm (ε = 1.9 × 10 ⁴ ). The large red shift from unsubstituted (E) -azobenzene (λ = 315 nm) suggests that the azobenzene moiety is heavily perturbed by the coordination of (E) -3a from nitrogen to boron. Absorption based on the n-π ^* transition of the azo group is not observed as a clear absorption band, and is thought to overlap with the red-shifted π-π ^* transition, as supported by the theoretical calculation described later. It is done.

When compound (E) -3a in heavy benzene solution was irradiated with light at room temperature using a high-pressure mercury lamp (λ = 360 nm), photoisomerization to (Z) -3a did not proceed, and most of the azobenzene derivatives In contrast to the case, it showed strong green fluorescence. The fluorescence spectrum in the hexane solution showed a maximum emission at 503 nm when (E) -3a was excited at 386 nm. Since the excitation spectrum observed at 500 nm coincided with the absorption spectrum due to the π-π ^* transition, this emission was attributed to the emission based on the transition from ¹ (π, π ^* ) to the ground state. The fluorescence quantum yield Φ of (E) -3a in hexane at room temperature was determined to be 0.40. This value is extremely higher than the fluorescence quantum yield of unsubstituted azobenzene (Φ = 2.53 × 10 ⁻⁵ ) and higher than any azobenzene derivative reported so far. The fluorescence quantum yield refers to the number of emitted fluorescence photons / absorbed photons, and is a value representing how much light is emitted as fluorescence when 1 light is applied. The larger this value, the stronger the fluorescence.

The azobenzene compound (E) -3c also showed strong green fluorescence as with (E) -3a when irradiated with light. In the fluorescence spectrum in hexane, compound (E) -3c showed an emission maximum at 524 nm when excited at 439 nm. The fluorescence quantum yield Φ of (E) -3c at room temperature in hexane was determined to be 0.99. This value is the highest ever recorded as an azobenzene derivative.

On the other hand, the fluorescence quantum yield Φ of compound (E) -3b excited at 370 nm was 0.01 or less. Considering that there is almost no peak in the wavelength based on the π-π ^* transition in the excitation spectrum and there is a main peak in the short wavelength corresponding to the transition of the aryl group, the emission of the compound (E) -3b is emitted from the azobenzene moiety. It is considered that light is emitted from an aryl group bonded to boron.

Considering the above results and the fact that 2- [2- (phenylazo) phenyl] -1,3,2-benzodioxaborole having an intramolecular BN coordination bond does not emit fluorescence even when irradiated with light, It can be seen that the choice of substituents on the boron is important with respect to the intensity of fluorescence.

[Factors of luminous characteristics]

In order to elucidate the factors of the characteristic emission characteristics of Compound (E) -3a and Compound (E) -3c, we used Gaussian 03 for the electronic state and excitation energy of Compound (E) -3a-c and unsubstituted azobenzene. The B3PW91 / 6-31G (d) level was obtained by DFT and TD-DFT calculations.

FIG. 3 shows calculated energy levels of frontier molecular orbitals and calculated singlet excitation energy.
The optimized structure of compound (E) -3a is in good agreement with the crystal structure. Its molecular orbitals were very different from those of unsubstituted azobenzene. In unsubstituted azobenzene, the π ^* , n, and π orbitals are attributed to LUMO, HOMO, and HOMO-1, respectively, but the energy level of the (E) -3a orbital based on the n orbitals of the azo group is It is lower than the energy level derived from the π orbit. Orbitals derived from π orbitals split into multiple energy levels as a result of interaction with two pentafluorophenyl groups bonded to boron. In addition, in (E) -3a, HOMO is not present at the azobenzene moiety but is localized at the pentafluorophenyl group. The decrease in the energy level of the n-orbital is due to the bonding interaction between the lone pair of nitrogen in the azo group and the empty p-orbital of boron. The (E) -3a ¹ (π, π ^* ) excited state is at a lower level than the ¹ (n, π ^* ) excited state. The inversion of the energy levels of the ¹ (n, π ^* ) and ¹ (π, π ^* ) levels increases the transition probability from the excited state to the ground state based on the orbital symmetry. This reversal phenomenon is considered to be one of the reasons that protonated azobenzene and 4- (dialkylamino) azobenzene emit fluorescence. Therefore, the characteristic emission characteristic of (E) -3a is attributed to the inversion of the levels of ¹ (n, π ^* ) and ¹ (π, π ^* ). In addition, the boron atom is fixed at a position suitable for intramolecular interaction with nitrogen of the azo group, so that a strong boron-nitrogen coordination bond is formed. As a result, the NNCC dihedral angle formed by both the nitrogen atom of the azo group and the benzene ring on the boron bonded side of the carbon atoms to which the azo group is bonded, and the carbon atom adjacent to the benzene ring is fixed. It is possible to form a rigid structure as compared with azobenzene in which the group is protonated or azobenzene in which the para position is substituted with an amino group. As a result of the increased rigidity of the structure of (E) -3a, the conformational change around the azo group is suppressed, which helps to show a relatively high fluorescence quantum yield.

In (E) -3b, the energy level of the bonding orbital is derived from the n orbital of the azo group, and is lower than the energy level derived from the n orbital of the azo group, as in (E) -3a. However, in contrast to the case of (E) -3a, the HOMO of (E) -3b has an n-orbital contribution of the azo group. This n-orbital contribution is thought to originate from the interaction between the occupied orbitals on the two aryl groups and the antibonding orbitals of the BN coordination orbitals. The energy level of the occupied orbital of the aryl group bonded to boron in (E) -3b is relatively high, so that it can interact with the antibonding orbital of the BN bond. This interaction results in a contribution to the HOMO from the n orbitals of the azo group. The contribution of HOMO from n orbitals in (E) -3b has the lowest singlet excited state of ¹ (n, π ^* ) and its fluorescence quantum yield is suppressed to a very low value. . Azobenzene (E) -3a is thought to lack the interaction between the antibonding orbitals of the boron-nitrogen coordination bond and the occupied orbitals of the two pentafluorophenyl groups. This is because the energy level of the occupied orbital of the C ₆ F ₅ group, which is an electron withdrawing group, is low, and the reaction of the strong boron-nitrogen bond consisting of _two electron withdrawing B (C ₆ F ₅ ) groups. This is because both the effects of the high energy level of the binding orbital are obtained, and as a result, (E) -3a has a light emission characteristic.

In (E) -3c, HOMO is derived from the π orbital of the azo group. Since (E) -3c has a structure in which (E) -3a is further substituted with an electron-donating methoxy group, it is considered that the energy level of this orbit is increased. In (E) -3c, the energy level of the orbit derived from the n orbital of the azo group is clearly lower than that of HOMO, and as in (E) -3a, there is a contribution from the n orbital of the azo group. There are no orbits at higher energy levels than orbits derived from π orbitals. The ¹ (π, π ^* ) excited state of (E) -3c is not only lower than the ¹ (n, π ^* ) excited state, but also the lowest singlet excited state. It is considered that the lowest singlet excited state is ¹ (π, π ^* ), which is the reason why (E) -3c has extremely high emission characteristics.

<Example>

[Solvent, synthesis environment, measuring equipment, etc.]

The solvent was purified before use. In principle, all reactions were carried out under an argon atmosphere. Spectral data of ¹ H NMR (400 MHz), ¹¹ B NMR (128 MHz), ¹³ C NMR (100 MHz) and ¹⁹ F NMR (376 MHz) were obtained using JEOL AL400. ¹³ C NMR (126 MHz) spectral data were obtained using a Bruker DRX-500. Tetramethylsilane was used as an external standard in 1H NMR and ¹³ C NMR, and BF ₃ · OEt ₂ and CCl ₃ F were used as external standards in ¹¹ B NMR and ¹⁹ F NMR, respectively. Absorption spectrum and fluorescence spectrum were measured with JASCO V-530 UV-vis spectrometer and Hitachi F-4500 fluorescence spectrometer, respectively. Preparative gel permeation liquid chromatography was performed using a JAIGEL H1 + H2 column and LC-908 (Nippon Analytical Industrial Co., Ltd.) using toluene as a solvent. All melting points are uncorrected values. Elemental analysis was performed in the organic element analysis room of the University of Tokyo. 2-Iodoazobenzene (2-Iodoazobenzene ((E) -1) and bis (4-fluorophenyl) isopropoxyborane (2b)) were synthesized by techniques described in the literature. The absolute value of the quantum yield was calculated by assuming that the quantum yield of fluorescein (0.1 M NaOH aqueous solution) was 0.92.

The following compounds will be described.

[Synthesis of Fluorobis (pentafluorophenyl) borane Diethyl Etherate (2a)]

Diethyl ether (Et ₂ O) solution (15 mL) of C ₆ F ₅ MgBr synthesized from Bromopentafluorobenzene (1.05 mL, 8.29 mmol) and magnesium (196 mg, 8.07 mmol) was added to BF ₃ · OEt ₂ (0.510 mL, 4.02 mmol) Was added at once to a diethyl ether solution (10 mL) at 0 ° C. The reaction solution was stirred for 30 minutes at 0 ° C., and then the solvent was removed under reduced pressure at 0 ° C. to obtain a gray solid. This crude solid was used in subsequent reactions without purification.

[(E) -Bis (pentafluorophenyl) [2- (phenylazo) phenyl] borane (Synthesis of (E) -3a)]

n-BuLi (1.66 M in hexane, 2.42 mL, 4.02 mmol) was added to a diethyl ether solution (30 mL) of 2-Iodoazobenzene ((E) -1) (1.13 g, 3.65 mmol) at −112 ° C. The reaction solution was stirred at −112 ° C. for 30 minutes, and then added to a diethyl ether solution (20 mL) of Fluoroborane 2a (4.02 mmol) at −112 ° C. The reaction temperature was gradually raised to room temperature. After removing the solvent under reduced pressure, the residue was dissolved in toluene, and the insoluble material was removed by filtration with a glass filter. The filtrate was concentrated and separated by preparative gel permeation liquid chromatography to give (E) -3a (539 mg, 28%).

The physical properties of this compound were as follows. (E) -3a: Brown crystals (Benzene / Hexane), mp 178.7-179.1 ° C ¹ H NMR (400MHz, CDCl3) δ 7.45-7.55 (m, 4H), 7.58 (dt, ³ J = 7.2 Hz, 4J = 1.2 Hz, 1H), 7.65 (d, ³ J = 6.8 Hz, 1H), 8.04 (d, ³ J = 7.6 Hz, 2H), 8.35 (d, ³ J = 7.5 Hz, 1H). ¹¹ B NMR (128 MHz , CDCl ₃ ) δ -0.8 (line width h _1/2 = 152 Hz) ¹³ C { ¹ H} NMR (100 MHz, CDCl ₃ ) δ 114.25 (br s, CB), 122.61 (s, CH), 128.39 ( s, CH), 128.57 (s, CH), 128.74 (s, CH), 129.67 (s, CH), 132.68 (s, CH), 135.96 (s, CH), 135.65-138.59 (m, CF), 138.62 . -141.59 (m, CF), 143.76 (s, CN), 146.21-149.06 (m, CF), 155.43 (br s, CB), 156.29 (s, CN) 19F NMR (376 MHz, CDCl 3) δ - 163.90 to -163.70 (m, 4F), -157.39 (t, ³ J = 19 Hz, 2F), -132.75 to -132.60 (m, 4F) .MS (EI, 70 eV) m / z 526 (M ⁺ , 15), 507 (3), 77 (100%). UV / vis (hexane) λ _max (ε) 243 (1.3 × 10 ⁴ ), 386 nm (1.9 × 10 ⁴ L mol ^-1 cm ^-1 ). Anal Calcd for C ₂₄ H ₉ BF ₁₀ N ₂ : C, 54.79; H, 1.72; N, 5.32. Found: C, 54.93; H, 1.99; N, 5.10 %.

[Synthesis of (E) -Bis (4-fluorophenyl) [2- (phenylazo) phenyl] borane ((E) -3b)]

(E) -1 (1.82 g, 5.90 mmol) in diethyl ether (40 mL) and n-BuLi (1.63 M in hexane, 4.30 mL, 6.57 mmol) and Isopropoxyborane 2b (1.67 g, 6.44 mmol) in diethyl ether A continuous reaction with the solution (10 mL) gave a yellow precipitate. After removing the supernatant from the precipitate, the solvent of the supernatant was removed under reduced pressure, and the residue was washed with cooled hexane (10 mL) to obtain a yellow solid. The solid was combined with the initial precipitate. The combined solids were dissolved in toluene and heated to reflux for 2 hours. The solvent was removed under reduced pressure to give (E) -3b (782 mg, containing 0.72 molar amount of Lithium Isopropoxide, 31%).

The physical properties of this compound were as follows. (E) -3b: yellow solid, mp 130.3-132.3 ° C (dec.). 1H NMR (400 MHz, CDCl3) δ 6.83-6.90 (m, 4H), 7.10-7.19 (m, 4H), 7.35-7.42 ( m, 2H), 7.42-7.50 (m, 2H), 7.50-7.55 (m, 1H), 7.56-7.61 (m, 1H), 7.98-8.03 (m, 2H), 8.32 (d, ³ J = 7.8 Hz , 1H). 11B NMR (128 MHz, CDCl3) δ 7.0 (line width h1 / 2 = 223 Hz). 13 C {1 H} NMR (126 MHz, C 6 D 6) δ 115.52 (d, 2 J CF = 20 Hz, CH), 124.34 (s, CH), 127.95 (s, CH), 128.68 (s, CH), 129.63 (s, CH), 130.23 (s, CH), 132.50 (s, CH), 134.96 ( s, CH), 135.58 (d, ³ J _CF = 6.9 Hz, CH), 141.77 (br s, CB), 145.12 (s, CN), 156.71 (s, CN), 163.05 (d, ¹ J _CF = 245 Hz, CF), 163.39 (br s, CB). 19 F NMR (376 MHz, CDCl 3) δ -118.47 ~ -118.37 (m, 2F). HRMS (FAB +) m / z calcd for C 24 H 17 BF ₂ N ₂ 382.1453, found 382.1432.

[Synthesis of 2-Iodo-4'-methoxyazobenzene ((E) -4)]

An aqueous solution (10 mL) of sodium nitrite (690 mg, 10.0 mmol) was added dropwise to a solution of 2-iodoaniline (2.19 g, 10.0 mmol) in hydrochloric acid (0.24 M, 100 mL, 24 mmol) at 0 ° C. for 10 minutes. Stir at ° C. An aqueous solution of Phenol (942 mg, 10.0 mmol) in sodium hydroxide (0.25 M, 40 mL, 10 mmol) was added to the reaction mixture at 0 ° C. and gradually warmed to room temperature. After stirring for an additional 16 hours, aqueous sodium hydroxide was added until the reaction mixture was basic. After washing with chloroform, hydrochloric acid was added to acidify the aqueous layer. The organic layer was extracted with chloroform, dried over anhydrous magnesium sulfate, and the solvent was removed under reduced pressure to obtain a deep red oil. Separation by silica gel column chromatography using chloroform and recrystallization from benzene-hexane gave 4- (2-Iodophenylazo) phenol (1.59 g, 48%) containing 0.096 mol of Phenol. This 4- (2-Iodophenylazo) phenol (1.55 g, 4.64 mmol) was added to a mixture of Dimethyl Sulfoxide (10 mL) and powdered potassium hydroxide (1.22 g, 21.7 mmol) at room temperature. Methyl Iodide (0.7 mL, 11 mmol) was added to the mixture and then stirred for 5 hours at room temperature. The reaction mixture was poured into water and extracted with chloroform. The organic layer was washed with water, dried over anhydrous magnesium sulfate, the solvent was removed under reduced pressure, and recrystallization from ethanol gave (E) -4 (1.39 g, 88%).

The physical properties of this compound were as follows. (E) -4: Red plate 1H NMR (400 MHz, CDCl ₃ ) δ 3.90 (s, 3H), 7.00-7.04 (m, 2H), 7.12 (ddd, ³ J = 7.6 Hz, ³ J = 7.6 Hz, 4J = 1.5 Hz, 1H), 7.40 (ddd, ³ J = 7.9 Hz, ³ J = 7.4 Hz, ⁴ J = 1.2 Hz, 1H), 7.60 (dd, ³ J = 7.9 Hz, ⁴ J = 1.5 Hz , 1H), 7.96-8.01 (m, 3H).

[Synthesis of (E)-[2- (4-Methoxyphenylazo) phenyl] bis (pentafluorophenyl) borane ((E) -3c)]

2-Iodo-4'-methoxyazobenzene ((E) -4) (1.02 g, 3.02 mmol) in diethyl ether (80 mL) was added to n-BuLi (1.6 M in Hexane, 2.00 mL, 3.20 mmol) and Fluoroborane 2a ( 5.05 mmol) in diethyl ether (15 mL) was continuously reacted. After removing the solvent under reduced pressure, the residue was dissolved in toluene, and the insoluble material was removed by filtration with a glass filter. Concentration of the filtrate and gel permeation liquid chromatography using toluene gave (E) -3c (448 mg, 27%). (E) -3c: orange solid, mp 204.3-205.3 ° C. ¹ H NMR (400 MHz, CDCl ₃ ) δ 3.87 (s, 3H), 6.91-6.96 (m, 2H), 7.45-7.54 (m, 2H) , 7.61 (d, ³ J = 6.1 Hz, 1H), 7.99-8.04 (m, 2H), 8.23 (d, ³ J = 6.3 Hz, 1H). ¹¹ B NMR (128 MHz, CDCl ₃ ) δ -0.6 ( _{line width h 1/2 = 201 Hz)} . 13 C {1 H} NMR (126 MHz, CDCl 3) δ 55.82 (s, CH 3), 114.99 (s, CH), 124.71 (s, CH), 127.71 ( s, CH), 128.26 (s, CH), 128.44 (s, CH), 134.92 (s, CH), 135.91-138.37 (m, CF), 137.79 (s, CO), 138.79-141.23 (m, CF) , 146.40-148.75 (m, CF), 151.89 (br s, CB), 156.22 (s, CN), 159.56 (br s, CB), 163.22 (br s, CB). 19F NMR (376 MHz, CDCl ₃ ) δ -162.34 to -162.15 (m, 4F), -155.93 (t, ³ J = 22 Hz, 2F), -131.18 (dd, ³ J = 22 Hz, ⁴ J = 7.4 Hz, 4F) .MS (EI, 70 eV) m / z 556 (M ⁺ , 100), 541 (24), 107 (45), 92 (32), 77 (55%). UV / vis (hexane) λ _max (ε) 250 (7.5 × 10 ³ ), 306 (1.2 × 10 ³ ), 439 nm (1.2 × 10 ⁴ L mol ^-1 cm ^-1 ). Anal. Calcd for C ₂₅ H ₁₁ BF ₁₀ N ₂ O: C, 53.99; H, 1.99; N, 5.04. Found: C, 54.17; H, 2.26; N, 4.86%.

[Theoretical calculation]

All calculations were performed at the DFT level using the Gaussian 03 (Revision B.01) program and using the B3PW91 exchange-correlation functional. In all calculations, 6-31G (d) was used as the basis set. The transition energy was obtained by time-dependent DFT (TD-DFT) method. The zero point energy is not corrected in all calculations.

The calculation results are shown below.

[Other Embodiments]

The following compounds were also synthesized in which boron substituents were bonded to the two benzene rings of azobenzene, respectively. In both benzene rings, an n-butyl group is bonded to the para position of nitrogen, unlike the case where only one boron is substituted. From the properties of this compound, it was found that the color tone changes dramatically when two boron substituents are introduced. Even in this case, various substituents can be introduced into the benzene rings A and B. In this case, as a raw material compound (starting material), for example, a 2,2′-diiodoazobenzene derivative may be used.

In addition, azobenzene is famous as a pigment, so there are numerous examples of synthesis. For example, synthetic methods such as azo coupling, hydrazobenzene oxidation, aniline oxidation, nitrobenzene reduction, azoxybenzene reduction, dehydration condensation of nitrosobenzene and aniline are known. By incorporating these synthetic methods into the above-described embodiment, it is also conceivable to introduce compounds having various characteristics such as fluorescence wavelength according to various uses by introducing various substituents into the benzene ring.

As apparent from the above synthesis method, there is no problem even if it is other than substituted benzene or condensed. Similar aromatic azo compounds can be synthesized from other aromatic rings, thiophene, and pyridine.

[Summary]

Azobenzene is one of the most common pigment materials and accounts for about half of the world's total dye production when viewed as an azo dye application. Azobenzene was generally considered not to emit light, but the compounds exhibiting the above-mentioned light emission characteristics are expected to be useful fluorescent materials due to the diversity and simplicity of the synthesis method and the ease of adjustment of the fluorescence wavelength. In this respect, the above-described embodiment is epoch-making.

It was found that [2- (4-methoxyphenylazo) phenyl] bis (pentafluorophenyl) borane, which is a boron-substituted azobenzene, exhibits the highest fluorescence quantum yield as an azobenzene derivative. The fluorescence quantum yield in room temperature solution was determined to be 0.99. Both the existence of a coordination bond between boron and nitrogen in the molecule and the fact that the coordination bond does not interact with the occupied orbitals of the pentafluorophenyl group cause the emission characteristics. It is thought that there is.

[Application]

Since the compound of the present embodiment has excellent characteristics, various applications are conceivable.

For example, it can also be used as a fluorescent paint or fluorescent dye. Since the compound of this embodiment has high brightness even in a small amount, it is excellent as a material for fluorescent paints and fluorescent dyes. It can also be used as a fluorescent ink. If used as a translucent fluorescent ink, it can also be applied to a fluorescent pen. Because it is translucent, it is easy to read overcoated characters and it is easily noticeable with fluorescent colors, so it may be widely used as a writing instrument for checking. In addition, fluorescent dyes can be added to white clothing and clothing detergents for the purpose of whitening by fluorescence, and dyes that emit colorless and blue fluorescence in visible light have the effect of concealing the yellowing of paper and cloth. It can also be used as an optical brightener.

It may be applied to fluorescent labels for biological materials, fluorescent probes (cell detection, DNA detection, protein detection), and clinical diagnosis, which often require high sensitivity. In particular, the compound of the present embodiment is suitable for a technique of coloring a specific biological tissue, cell, organelle, etc. with a special dye, and for staining. In the case of use as a staining agent or staining agent, a specific dye strongly binds to characteristic biomolecules (proteins, nucleic acids, lipids, hydrocarbons, etc.) contained in the specimen to be observed. Even if it utilizes, the substrate which reacts with a specific enzyme and develops color may be used.

Fluorescence is more sensitive than observing absorption. Therefore, when performing a microanalysis using HPLC or the like, the target is converted to a derivative of the present embodiment that emits fluorescence and analyzed. It is also possible.

A flow cytometer, a device used for flow cytometry, which is a method of optically analyzing individual particles by dispersing fine particles in a fluid and flowing the fluid finely. It is also possible to employ the compound of this embodiment for (Flow Cytometers). Similarly, fine particles can be selectively recovered. An example of this principle is as follows. A light beam having a certain wavelength (for example, laser light) is applied to the fluid, and usually forward scattering in the direction along the light beam and side scatter in the direction perpendicular to the light beam are detected. In addition, one or more fluorescence detectors are provided for detecting the fluorescence generated by the laser light by labeling the fine particles with a fluorescent substance. These detectors detect light and fluorescence affected by particles in the fluid.

Application to fluorescent fundus imaging in which the fluorescent dye of the present embodiment is put into blood and the fundus is photographed with fluorescence is also conceivable.

It is also conceivable to apply the compound of the present embodiment as a light emitting element of organic electroluminescence (Organic Electroluminescence, organic EL, Organic Light Emitting Diode, OLED). In the case of a light emitting element, it is incorporated in a display, a lighting fixture or the like. When the fluorescent material is applied to organic electroluminescence, it is desirable that the fluorescent material has a high quantum yield in order to obtain high luminance with low energy (low power), but the compound of this embodiment is advantageous in that respect. It is.

It is also conceivable to apply the compound of this embodiment to a cathode ray tube. In this case, for example, electrons are focused on a single electron beam, deflected by a magnetic field, scanned on a display surface (anode, anode) coated with a fluorescent material, and light is emitted when the electrons collide with the fluorescent material. The It is also conceivable to apply the compound of the present embodiment to a field emission display (FED). In this case, for example, the emitted electrons are pulled to the anode side on the anode side, and light emission is obtained by causing the electrons to collide with the phosphor on the anode side. Furthermore, it is also conceivable to apply the compound of the present embodiment to a surface-conduction electron-emitter display (SED). In this case, for example, when a voltage is applied between nano-order slits made of an ultrafine particle film, electrons are emitted by the tunneling effect, and the principle of emitting light by colliding with the phosphor is applied. Further, it can be applied to an electron tube, a fluorescent display tube, a fluorescent display tube module, and a fluorescent light emitting print head.

It is also conceivable to apply the compound of this embodiment to a fluorescent lamp. In this case, for example, a substance that absorbs ultraviolet rays emitted from mercury and emits visible light as fluorescence is applied to the surface of the low-pressure mercury lamp. It is also conceivable to apply the compound of this embodiment to a cold cathode tube and further to a light source for a liquid crystal backlight. The types of fluorescent lamps include, for example, general fluorescent lamps, straight pipes, rod-shaped fluorescent lamps, ring-shaped fluorescent lamps, donut-shaped fluorescent lamps, slim type, twin type, ring-shaped fluorescent lamps, bulb-type fluorescent lamps, compact fluorescent lamps Fluorescent lamps dedicated to high-frequency lighting, cold cathode fluorescent lamps (cold cathode fluorescent lamps), long afterglow fluorescent lamps, fluorescent lamps with a photocatalyst film, fluorescent lamps with synthetic resin coating, electrodeless fluorescent lamps, fluorescent lamps for insecticide devices , Fluorescent lamps for insect repellent, and those with small metal balls.

When a substance having an appropriate energy level capable of absorbing energy is added to a substance emitting fluorescence, the fluorescence disappears. It is also conceivable to use the compound of this embodiment in combination with a quencher that is a substance that causes this quenching.

Azobenzene derivatives have many examples of research as photochromic dyes. Applications such as control of host-guest chemistry with azobenzene derivatives, control of polymer and film properties with azobenzene, control of liquid crystal properties with azobenzene, and a combination of azobenzene photochromism and electrochemistry are also possible. For the compound of the present embodiment, the boron-nitrogen bond is cleaved by, for example, coordinating other elements to boron after the synthesis, so that the compound has properties as a general azobenzene derivative, and photoresponse from the phosphor. It can also be changed to a sex molecule switch.

[Others]

Most azobenzenes are not used as light-emitting moieties, but some azobenzene derivatives that are exceptionally fluorescent are known. Protonated azobenzene, hydroxyazobenzene, aminoazobenzene and the like are examples of azobenzene derivatives exhibiting fluorescence. Many of the azobenzene derivatives exhibiting fluorescence exhibit fluorescence only in a low temperature matrix, and their fluorescence quantum yield is extremely low. In addition, azobenzene metallated in the ortho position and self-assembled azobenzene aggregates have also been reported to emit light although being azobenzene, which is about 10 ^{-3 in} a room temperature solution, which is relatively higher than the above azobenzene. High fluorescence quantum yield is shown. It is argued that the azobenzene complex metallated at the ortho position exhibits high emission characteristics because the structure near the azo group becomes rigid due to the coordinate bond between the nitrogen and transition metal. In the case of an azobenzene derivative aggregate, it is said that strong fluorescence is exhibited depending on the excited state generated by the association. However, in the case of fluorescence generated as a result of nitrogen-metal coordination bond or association, the fluorescence quantum yield is relatively high when viewed as azobenzene, but is low compared to other organic fluorescent materials.

In the above-described embodiment, since an azobenzene derivative having high emission characteristics and high fluorescence quantum yield can be synthesized, it is expected that the possibility of application as a fluorescent probe of a chemical sensor or a light emitting element will be greatly expanded.

In particular, it is advantageous that fluorescence can be observed at a high temperature including room temperature and a wide temperature range.

In general, factors that determine the intensity of fluorescence include the intensity of light hitting a substance, the thickness of the substance, the molar concentration of the substance, and the fluorescence quantum yield of the substance. Among these, the fluorescence quantum yield of the substance is a property unique to the substance, and in reality, there are not many substances having a high fluorescence quantum yield. Furthermore, even when a substance (compound) having a high fluorescence quantum yield is applied to a material, it is easy to synthesize, has multiple synthesis methods, has a simple structure, and has various derivatives. It is desirable to satisfy the requirements such as being able to synthesize, and having many research examples on the relationship between structure and properties. Also in this point, the aromatic azo compound of the above-described embodiment is excellent.

In addition, since various synthetic methods are known for aromatic azo compounds and azobenzene, it is expected that when applied as a fluorescent moiety, an organic fluorescent material can be prepared more easily and characteristics such as wavelength can be easily controlled.

In particular, it has been found that the azobenzene derivative of the above-described embodiment emits fluorescence not only when it is made into a solution but also when it is applied in the form of a thin film. Thereby, since the film-like phosphor can be easily obtained, the azobenzene derivative of the above-described embodiment has a great use.

The inventors have so far reported that the coordination number of silicon, boron, and phosphorus can be switched by light irradiation using intramolecular coordination and photoisomerization of azobenzene. The above-mentioned matters are based on the results of detailed studies that led to the discovery of an azobenzene derivative exhibiting the highest fluorescence quantum yield in the history of various investigations by the inventors regarding the azobenzene derivative.

[About right interpretation]

The present invention has been described above with reference to specific embodiments. However, it is obvious that those skilled in the art can make modifications or substitutions of the embodiment without departing from the gist of the present invention. That is, the present invention has been disclosed in the form of exemplification, and the contents described in the present specification should not be interpreted in a limited manner. In order to determine the gist of the present invention, the claims section described at the beginning should be considered.

It will also be appreciated that illustrative embodiments of the invention achieve the above objects, but that many modifications and other examples can be made by those skilled in the art. The elements or components of each embodiment described in the claims, specification, drawings, and description may be employed in combination with one or more other elements. The claims are intended to cover such modifications and other embodiments, which are within the spirit and scope of the present invention.

FIG. 4 is an ORTEP diagram of compound (E) -3a. (A) Absorption spectrum and fluorescence spectrum of compound (E) -3a in hexane at room temperature (excitation at 386 nm), (B) Hexane solution of compound (E) -3a in an environment irradiated with light of 360 nm from the left side ( (5) photo, (C) absorption spectrum and fluorescence spectrum of compound (E) -3c in hexane at room temperature (excitation at 439 nm), (D) compound in an environment irradiated with 360 nm light from the left side (E) This is a photograph of a -3c hexane solution (about 5 μM). It is the calculated value of the energy level of a frontier molecular orbital, and the calculated value of a singlet excitation energy.

Claims (14)

formula
[Where:
X and Y may have a substituent, and may be a condensed aromatic ring,
Ar ₁ and Ar ₂ are C ₆ F ₅ . ]
Or a salt thereof. The substituent is (i) an alkyl group, (ii) an alkoxy group, (iii) an alkylthio group, (iv) a dialkylamino group, (v) a pyrrolidino group, (vi) a piperidino group, (vii) a morpholino group, (viii) ) Aryl group, (ix) aryloxy group, (x) hydroxy group, (xi) amino group, (xii) monoalkylamino group, (xiii) acylamino group, (xiv) acyloxy group, (xv) alkylsulfonylamino group 2. The compound or a salt thereof according to claim 1, which is hydrogen. formula
[Where:
A ring and B ring are optionally substituted benzene rings,
A _r1 and Ar ₂ are C ₆ F ₅
R1 is hydrogen, an alkyl group having 1, 2, 3, 4, 5 or 6 carbon atoms or an alkoxy group having 1, 2, 3, 4, 5 or 6 carbon atoms. ]
Or a salt thereof. formula
[Wherein Ar ₁ and Ar ₂ are C ₆ F ₅ . ]
Or a salt thereof. formula
[Where:
X and Y may have a substituent, and may be a condensed aromatic ring,
Ar ₁ , Ar ₂ , Ar ₃ and Ar ₄ are C ₆ F ₅ . ]
Or a salt thereof. The substituent is (i) an alkyl group, (ii) an alkoxy group, (iii) an alkylthio group, (iv) a dialkylamino group, (v) a pyrrolidino group, (vi) a piperidino group, (vii) a morpholino group, (viii) ) Aryl group, (ix) aryloxy group, (x) hydroxy group, (xi) amino group, (xii) monoalkylamino group, (xiii) acylamino group, (xiv) acyloxy group, (xv) alkylsulfonylamino group 6. The compound or a salt thereof according to claim 5, which is hydrogen. formula
[Where:
A ring and B ring are optionally substituted benzene rings,
Ar ₁ , Ar ₂ , Ar ₃ and Ar ₄ are C ₆ F ₅ ,
R1 and R2 are hydrogen, an alkyl group having 1, 2, 3, 4, 5 or 6 carbon atoms or an alkoxy group having 1, 2, 3, 4, 5 or 6 carbon atoms. ]
Or a salt thereof. A reaction between a metallized aromatic azo compound and a boron-containing compound
[Where:
X and Y may have a substituent, and may be a condensed aromatic ring,
Ar ₁ and Ar ₂ are C ₆ F ₅ . ]
The manufacturing method of the compound or its salt which manufactures the compound represented by these, or its salt. A reaction between a metallized aromatic azo compound and a boron-containing compound
[Where:
X and Y may have a substituent, and may be a condensed aromatic ring,
Ar ₁ , Ar ₂ , Ar ₃ and Ar ₄ are C ₆ F ₅ . ]
The manufacturing method of the compound or its salt which manufactures the compound represented by these, or its salt. Excited state ¹ (n, ^{π *)} excited state energy level lower than ^{1 (π, π *)} has, aromatic azo compound and at least one NNCC dihedral angle is fixed . An aromatic azo compound characterized in that the lowest singlet excited state is ¹ (π, π ^* ) and at least one NNCC dihedral angle is fixed. 12. The aromatic azo compound according to claim 10, wherein an N—N—C—C dihedral angle is fixed by bonding boron to the 2-position of azobenzene and a diazediyl group. 13. The aromatic azo compound according to claim 12, wherein an aryl group is bonded to boron. Excited state ¹ (n, ^{π *)} excited state ^{1 (π, π *)} of lower energy level than have, characterized in that it contains an aromatic azo compound of at least one NNCC dihedral angle is fixed Fluorescent material.