阅读说明：本技术 一种溴原子修饰的蓝光吸收增强型铱(iii)配合物及其制备方法 (Bromine atom modified blue light absorption enhanced iridium (III) complex and preparation method thereof ) 是由 谭桂平 官永昌 陈孟镛 伦振安 邓泳锋 阮巧云 张敏 于 2021-10-14 设计创作，主要内容包括：本发明涉及光催化及有机金属化学领域,特别是涉及一种溴原子修饰的蓝光吸收增强型铱(III)配合物及其制备方法,该铱(III)配合物拥有更强的蓝光吸收能力,如果在460nm光照射下的二氧化碳光催化还原反应中用作光敏剂的话,具有更强的蓝光区域吸光能力,将能吸收更多的蓝光,使光子能力转换为化学反应能量的效率也更高,与现有的铱(III)配合物相比,本发明的铱(III)配合物成为更优秀的光敏剂。(The invention relates to the fields of photocatalysis and organic metal chemistry, in particular to a bromine atom modified blue light absorption enhanced iridium (III) complex and a preparation method thereof, wherein the iridium (III) complex has stronger blue light absorption capacity, has stronger blue light absorption capacity if being used as a photosensitizer in carbon dioxide photocatalytic reduction reaction under 460nm light irradiation, can absorb more blue light, has higher efficiency of converting photon capacity into chemical reaction energy, and becomes a more excellent photosensitizer compared with the existing iridium (III) complex.)

1. A bromine atom modified blue light absorption enhancement type iridium (III) complex is characterized by having the following chemical general formula:

2. a preparation method of a bromine atom modified blue light absorption enhancement type iridium (III) complex is characterized by comprising the following steps:

s1, under the protection of nitrogen, placing the polished magnesium into 5mL of dry tetrahydrofuran organic solvent, slowly dropwise adding the compound 1 dissolved by 20mL of tetrahydrofuran, and continuously stirring for 2 hours after dropwise adding; cooling to-78 ℃ by using a liquid nitrogen-acetone bath, keeping the temperature at low, slowly adding 15mL of tetrahydrofuran solution of trimethyl borate, continuously stirring to return to room temperature after dropwise addition, then carrying out acidification hydrolysis, washing and extracting by using saturated salt solution, evaporating and concentrating, and finally adding n-hexane for recrystallization to obtain a compound 2;

s2, dissolving 2-bromopyridine and the compound 2 in tetrahydrofuran, adding a solution of tetrakistriphenylphosphine palladium and potassium carbonate, carrying out Suzuki coupling reaction at 75 ℃ for 48 hours under the protection of nitrogen, extracting the reaction solution by using ethyl acetate, washing by using saturated saline solution, concentrating and evaporating, using normal hexane as an eluent, carrying out separation and purification by using a silica gel chromatographic column, extracting by using ethyl acetate, washing by using saturated saline solution, concentrating and evaporating, using normal hexane and ethyl acetate as the eluent, and carrying out separation and purification by using the silica gel chromatographic column to obtain a light yellow crystal intermediate product, namely the compound 3;

s3, adding the compound 3 into 45ml of chloroform for dissolving, weighing N-bromosuccinimide (NBS), adding NBS every 3 minutes, adding NBS into chloroform for a small number of times, stirring in the dark for reaction for 8 hours under the reaction condition of ice-water bath, and directly drying the reaction solution by a rotary evaporator in a spinning mode; separating and purifying with silica gel chromatographic column with n-hexane as eluent to obtain white powdered intermediate, compound 4;

s4, adding the compound 4 and iridium trichloride hydrate into 12mL of mixed solution of ethylene glycol ethyl ether and water, heating to 90 ℃ under the protection of nitrogen, stirring for reaction for 12 hours, dissolving and separating out the reaction liquid by using water, and performing suction filtration to obtain a compound 5;

s5, adding the compound 5 and acetylacetone, adding sodium carbonate into 15mL of ethylene glycol ethyl ether, heating to 100 ℃ and reacting for 10 hours, wherein the reaction process is protected by nitrogen; extracting the reaction liquid by using dichloromethane, washing by using a saturated sodium chloride aqueous solution, concentrating and evaporating, and separating and purifying by using normal hexane and dichloromethane as eluent by using a silica gel chromatographic column to obtain a red solid product.

3. The method for producing a bromine-atom-modified blue-light-absorption-enhanced iridium (III) complex according to claim 2, wherein in step S1, the compound 1 is 2-bromothiophene.

4. The method for preparing a bromine-atom-modified blue-light-absorption-enhanced iridium (III) complex according to claim 2, wherein in step S1, the step of acidifying hydrolysis is to add 10% hydrochloric acid to a pH of 1 to 2.

5. The method for producing a bromine-atom-modified blue-light-absorption-enhanced iridium (III) complex according to claim 2, wherein in step S1, the compound 2 is 2-thiopheneboronic acid with a yield of 87.77%.

6. The method for producing a bromine-atom-modified blue-light-absorption-enhanced iridium (III) complex according to claim 2, wherein in step S2, the 2-bromopyridine and the compound 2 are added in a ratio of 1: 2; the ratio of the n-hexane to the ethyl acetate is 6: 1.

7. The method for producing a bromine-atom-modified blue-light-absorption-enhanced iridium (III) complex according to claim 2, wherein in step S2, the compound 3 is 2-thienylpyridine, and the yield thereof is 91.98%.

8. The method for producing a bromine-atom-modified blue-light-absorption-enhanced iridium (III) complex according to claim 2, wherein in step S3, the compound 4 is 2- (5-bromo-2-thienyl) pyridine with a yield of 88.09%.

9. The method for preparing a bromine-atom-modified blue-light-absorption-enhanced iridium (III) complex according to claim 2, wherein in step S4, the ratio of ethylene glycol ethyl ether to water is 3: 1.

10. The method for preparing a bromine-atom-modified blue-light-absorption-enhanced iridium (III) complex according to claim 2, wherein in step S5, the ratio of n-hexane to dichloromethane is 1: 2.

Technical Field

The invention relates to the fields of photocatalysis and organic metal chemistry, in particular to a bromine atom modified blue light absorption enhanced iridium (III) complex and a preparation method thereof.

Background

The existing iridium (III) complex has poor light absorption range and light absorption intensity in a visible light absorption spectrum when a traditional organic ligand, such as a 2-phenylpyridine (ppy) ligand, is used, so that when the iridium (III) complex is used as a photosensitizer in the field of light energy conversion, such as a photocatalytic reaction, the effect is not ideal, wherein the photosensitizer can absorb the energy of visible light and transfer the energy to some reactants insensitive to the visible light in a photochemical reaction to improve or enlarge the light sensitivity of the reactants, so that the reactants can generate a chemical reaction, and the photosensitizer does not participate in the chemical reaction.

Iridium (III) complexes Ir (ppy) based on ppy ligands₂The structure of acac is shown in FIG. 1, a classical iridium (III) complex which has been commercialized and is denoted by Y1 in the present invention.

Disclosure of Invention

In order to solve the technical problems, the invention provides a bromine atom modified blue light absorption enhanced iridium (III) complex with stronger blue light region light absorption capacity and a preparation method thereof.

The invention adopts the following technical scheme:

a bromine atom modified blue light absorption enhancement type iridium (III) complex, which has a chemical formula as follows:

a preparation method of a bromine atom modified blue light absorption enhancement type iridium (III) complex comprises the following steps:

s1, under the protection of nitrogen, placing the polished magnesium into 5mL of dry tetrahydrofuran organic solvent, slowly dropwise adding the compound 1 dissolved by 20mL of tetrahydrofuran, and continuously stirring for 2 hours after dropwise adding; cooling to-78 ℃ by using a liquid nitrogen-acetone bath, keeping the temperature at low, slowly adding 15mL of tetrahydrofuran solution of trimethyl borate, continuously stirring to return to room temperature after dropwise addition, then carrying out acidification hydrolysis, washing and extracting by using saturated salt solution, evaporating and concentrating, and finally adding n-hexane for recrystallization to obtain a compound 2;

s2, dissolving 2-bromopyridine and the compound 2 in tetrahydrofuran, adding a solution of tetrakistriphenylphosphine palladium and potassium carbonate, carrying out Suzuki coupling reaction at 75 ℃ for 48 hours under the protection of nitrogen, extracting the reaction solution by using ethyl acetate, washing by using saturated saline solution, concentrating and evaporating, using normal hexane as an eluent, carrying out separation and purification by using a silica gel chromatographic column, extracting by using ethyl acetate, washing by using saturated saline solution, concentrating and evaporating, using normal hexane and ethyl acetate as the eluent, and carrying out separation and purification by using the silica gel chromatographic column to obtain a light yellow crystal intermediate product, namely the compound 3;

s3, adding the compound 3 into 45ml of chloroform for dissolving, weighing N-bromosuccinimide (NBS), adding NBS every 3 minutes, adding NBS into chloroform for a small number of times, stirring in the dark for reaction for 8 hours under the reaction condition of ice-water bath, and directly drying the reaction solution by a rotary evaporator in a spinning mode; separating and purifying with silica gel chromatographic column with n-hexane as eluent to obtain white powdered intermediate, compound 4;

s4, adding the compound 4 and iridium trichloride hydrate into 12mL of mixed solution of ethylene glycol ethyl ether and water, heating to 90 ℃ under the protection of nitrogen, stirring for reaction for 12 hours, dissolving and separating out the reaction liquid by using water, and performing suction filtration to obtain a compound 5;

s5, adding the compound 5 and acetylacetone, adding sodium carbonate into 15mL of ethylene glycol ethyl ether, heating to 100 ℃ and reacting for 10 hours, wherein the reaction process is protected by nitrogen; extracting the reaction liquid by using dichloromethane, washing by using a saturated sodium chloride aqueous solution, concentrating and evaporating, and separating and purifying by using normal hexane and dichloromethane as eluent by using a silica gel chromatographic column to obtain a red solid product.

In a further improvement of the above technical scheme, in step S1, the compound 1 is 2-bromothiophene.

In a further improvement of the above technical solution, in step S1, the step of acidifying and hydrolyzing includes adding 10% hydrochloric acid to a pH of 1 to 2.

In a further improvement of the above technical scheme, in step S1, the compound 2 is 2-thiopheneboronic acid, and the yield is 87.77%.

The technical scheme is further improved in that in the step S2, the adding ratio of the 2-bromopyridine to the compound 2 is 1: 2; the ratio of the n-hexane to the ethyl acetate is 6: 1.

In a further improvement of the above technical scheme, in step S2, the compound 3 is 2-thienyl pyridine, and the yield is 91.98%.

In a further improvement of the above technical scheme, in step S3, the compound 4 is 2- (5-bromo-2-thienyl) pyridine, and the yield is 88.09%.

In a further improvement of the above technical solution, in step S4, the ratio of the ethylene glycol ethyl ether to water is 3: 1.

The technical scheme is further improved in that in the step S5, the ratio of the n-hexane to the dichloromethane is 1: 2.

The invention has the beneficial effects that:

the iridium (III) complex has stronger blue light absorption capacity, has stronger blue light area light absorption capacity if being used as a photosensitizer in carbon dioxide photocatalytic reduction reaction under 460nm light irradiation, can absorb more blue light, has higher efficiency of converting photon capacity into chemical reaction energy, and becomes a more excellent photosensitizer compared with the existing iridium (III) complex.

Drawings

FIG. 1 is an iridium (III) complex Ir (ppy) based on ppy ligands₂The structure of acac;

FIG. 2 is a synthesis scheme of a bromine atom modified blue light absorption enhancement iridium (III) complex of the present invention;

FIG. 3 is a diagram showing UV-VIS absorption spectra of a bromine atom-modified blue light absorption enhancement type iridium (III) complex C1 and an iridium (III) complex Y1 according to the present invention.

Detailed Description

A bromine atom modified blue light absorption enhancement type iridium (III) complex, which has a chemical formula as follows:

as shown in fig. 2, a preparation method of a bromine atom modified blue light absorption enhancement type iridium (III) complex includes the following steps:

s1, under the protection of nitrogen, putting polished magnesium (0.392g, 0.0163mol) in a dry Tetrahydrofuran (THF) organic solvent (5mL), slowly dropwise adding the compound 1 (2-bromothiophene, 1.64mL, 2.7001g, 0.0166mol) dissolved in THF (20mL), and continuing stirring for 2 hours after dropwise adding. Cooling to-78 ℃ by using a liquid nitrogen-acetone bath, keeping the temperature low while slowly adding a THF (15mL) solution of trimethyl borate (6.0mL, 5.3508g and 0.05149mol), after dropwise addition, continuously stirring to room temperature, then carrying out acidification hydrolysis (adding 10% hydrochloric acid to pH 1-2), washing and extracting with saturated saline solution, evaporating and concentrating, and finally adding n-hexane for recrystallization to obtain the compound 2 (2-thiopheneboronic acid, 1.8650g and 0.01457mol, wherein the yield is 87.77%).

S2, dissolving 2-bromopyridine (1mL, 1.657g, 0.0105mol) and compound 2(2.6943g, 0.02106mol) in THF in an amount of 1:2, adding palladium tetratriphenylphosphine (0.6075g, 0.000525mol) and potassium carbonate solution (2mol/L, 20mL), carrying out Suzuki coupling reaction at 75 ℃ for 48 hours under the protection of nitrogen, extracting the reaction liquid by ethyl acetate, washing by saturated saline, concentrating and evaporating, using normal hexane as eluent, carrying out silica gel chromatographic column separation and purification, extracting by ethyl acetate, washing by saturated saline, concentrating and evaporating, using normal hexane: ethyl acetate ═ 6:1 as eluent, carrying out silica gel chromatographic column separation and purification, and obtaining intermediate product compound 3 (2-thienyl pyridine, 1.557g, 0.009658 mol) which is a light yellow crystal, wherein the yield is 91.98%).

S3, compound 3(0.9460g, 0.005868mol) was dissolved in 45ml of chloroform (CHCl3), N-bromosuccinimide (NBS, 1.0040g, 0.005644mol) was weighed, NBS was added every 3 minutes, NBS was added to chloroform in small amounts, and the mixture was stirred with light for 8 hours under the reaction conditions of an ice-water bath, and the reaction solution was directly dried by a rotary evaporator. Using normal hexane as eluent, separating and purifying by a silica gel chromatographic column to obtain a white powdery solid intermediate product, namely a compound 4[2- (5-bromo-2-thienyl) pyridine, 1.235g, 0.005143mol, wherein the yield is 88.09 percent ].

S4, compound 4(0.4008g, 0.001675mol) and iridium trichloride hydrate (0.2001g, 0.00067mol) were added to ethylene glycol ethyl ether: in a solution of 3:1 (12mL) in water, the mixture was heated to 90 ℃ under nitrogen protection, and the reaction mixture was stirred for 12 hours, whereupon the reaction mixture was dissolved in water and filtered by suction to obtain compound 5(0.3806g, 0.0002696mol, 40.24% yield).

S5, reacting compound 5(0.3806g, 0.0002696mol) with acetylacetone (1mL, 0.975g, 0.009738mol), adding sodium carbonate (0.2560g, 0.002415mol) in ethylene glycol ethyl ether (15mL), heating to 100 ℃ and reacting for 10 hours, wherein the reaction process is protected by nitrogen. The reaction solution was extracted with dichloromethane, washed with saturated aqueous sodium chloride solution, concentrated and evaporated, and the reaction solution was purified by distillation using n-hexane: dichloromethane ═ 1:2 as eluent, and separation and purification by silica gel chromatography gave product C1(0.0722g, 0.000094mol, 34.87% yield) as a red solid.

C1 nuclear magnetic resonance spectrum 1H NMR (cdcl3,400mhz): δ (ppm)1.753(s,3H, acac),1.811(s,3H, acac),5.224(s,1H, acac),6.218(s,1H, Ar),6.461-6.497(m,1H, Ar),7.008(s,1H, Ar),7.097-7.132(m,1H, Ar),7.195-7.221(d, J ═ Hz,1H, Ar),7.275-7.316(m,2H, Ar),7.418-7.441(d, J ═ 1H, Ar),7.670-7.713(m,1H, Ar),8.277-8.296(d, J ═ Hz,1H, Ar); 13C NMR (CDCl3,100MHz) delta (ppm)28.61(acac),100.66(acac),117.11,118.38,128.01,131.80,135.72,148.20,148.43,165.19,184.51 (Ar).

The iridium (III) complex claimed by the invention adopts 2- (5-bromo-2-thienyl) pyridine [2- (5-bromothiophhen-2-yl) pyridine ] as a ligand, replaces a benzene ring on a ppy ligand with a thiophene group grafted with a bromine atom, and obtains a brand new iridium (III) complex after cyclometalation reaction with trivalent iridium ions, wherein C1 is used as a code in the patent; c1 is applied to the carbon dioxide photocatalytic reduction reaction under blue light irradiation, and the iridium (III) complex C1 described by the invention is used as a photosensitizer in the reaction system.

(1) Preparing Y1 stock solution as photosensitizer and Co (TPA) ClO in reaction system by using acetonitrile solvent₄The stock solution is used as a catalyst in a reaction system, and BIH is used as an electronic sacrificial body in the reaction system; in the experiment, a 10ml ground thick-wall round-bottom test tube is used as a reaction container, and the total volume of a reaction system in the photocatalysis experiment is 2 ml;

(2) a stirring magneton is put into a test tube, and a photosensitizer, a catalyst, an electronic sacrificial body and a solvent are added, wherein the concentration of Co (TPA) ClO4 in the system is 0.05mM, and the concentration gradient of Y1 is 0.1mM, 0.2mM, 0.3mM, 0.4mM, 0.5MBIH and acetonitrile are used as solvents. Plugging the bottle neck with a rubber plug, sealing the bottle neck with a sealing film, introducing carbon dioxide into the solution of the test tube with a long needle for 30min to ensure that the carbon dioxide is saturated in the solution, and sealing the rubber plug with an electrical rubber;

(3) and finally, stirring the aerated test tube under a magnetic stirrer, and simultaneously illuminating by using visible light blue light, wherein the reaction temperature is 25 ℃. Performing illumination for 24 hours;

(4) detecting the content of carbon monoxide in a test tube by using gas chromatography, wherein the temperature of a sample inlet heater is 80 ℃, the pressure is 17.162PSI, the sample is injected by adopting a split mode, the split ratio is 6:1, the flow rate of a carrier gas is 20ml/min, the temperature of a detector heater is 200 ℃, the reference flow is 20ml/min, the tail blowing flow is 5ml/min, the flow rate of a chromatographic column is 3ml/min, the pressure is 17.162PSI, and the column temperature is 45 ℃. During sample introduction, a sampling needle is inserted into a test tube to extract 100 mu l of sample, then the sample introduction is carried out rapidly, the carbon monoxide peak emergence time can be obtained by establishing a carbon monoxide standard curve according to the used instrument, and the yield is calculated according to the corresponding peak area;

(5) detecting the content of formate in the test tube by using ion chromatography, wherein the eluent is 4.5mM NaCl₃Solution and 1.4mM NaHCO₃The flow rate of the solution is 1ml/min, the sample introduction amount is 1ml, the column temperature is 25 ℃, the pressure is 2000PSI, the suppressor current is 25mA, 30 mul of reaction solution is extracted from a test tube into a 4ml centrifuge tube, and 3ml of ultrapure water is added to introduce the sample into the centrifuge tubeDiluting, filtering the diluted sample by using a water system filter head, finally extracting 1ml of filtrate, injecting the filtrate into an ion chromatography for detection, establishing a standard curve of the formate according to a used instrument to obtain the peak-off time of the formate, and calculating the yield according to the corresponding peak area.

According to the experimental result, when the concentration of Y1 is 0.4mM, Co (TPA) ClO is found in the system₄At a concentration of 0.05mM and a BIH content of 0.5M, the TONs (ratio of the amount of the reduction product species to the amount of the catalyst species in the system) of CO, H2 and HCOO-reached 28.86, 33.91 and 5.47, respectively, with corresponding selectivities of 42%, 50% and 8%.

Wherein BIH is 1,3-dimethyl-2-phenyl-2, 3-dihydro-1H-benzole, wherein the name is 1,3-dimethyl-2-phenyl-2, 3-dihydro-1H-benzimidazole.

Wherein, the model of the gas chromatograph is as follows: agilent 7820A; the ion chromatograph has the following types: dyan DIONEX LC 25.

In the study of photocatalytic reduction of carbon dioxide, researchers have generally employed blue light from 400nm to 460nm as the light source. When the conventional iridium (III) complex Y1 is used as a photosensitizer, Y1 has an excellent triplet lifetime, but its visible light absorption capacity is insufficient, and particularly, the light absorption capacity in the range of 400nm to 460nm is weak, as shown in fig. 3, the absorption intensity of the ultraviolet-visible light absorption spectrum of Y1 between 400nm and 460nm is small, and is at most 0.023 (at 459 nm). Whereas at the same concentration (1 x 10-4mol/L) we synthesized C1 with an absorption intensity between 400nm and 460nm of at most 0.097 (at 400 nm) and at least 0.038 (at 460 nm), the light absorption capacity of C1 was much stronger than Y1 by a factor of up to 4. Therefore, C1 will have better light absorption efficiency in the photocatalytic reduction of carbon dioxide by blue light irradiation.