A reversible electrochromic viologen ligand Mn complex and preparation method thereof

Abstract

The invention discloses a reversible electrochromic viologen ligand Mn complex and a preparation method thereof, belonging to the field of functional complex chemistry. The molecular formula of the complex is {[Mn(L)(H2O)2](NO3)·2.5H2O} n The complex single crystal is prepared by dissolving 3-(1,2,4-triazole-5-carboxylic acid)-4,4'-bipyridinium chloride and Mn(NO3)2 in a mixed solution of water and ethanol, heating the mixture for reaction, and then naturally cooling the mixture to room temperature. The complex has a reversible electrochromic property. When a voltage of 0.1 to 0.6V is applied, the color can change from light yellow to dark purple, and the complex has good fatigue resistance.

Description

Technical Field

[0001] The invention relates to a reversible electrochromic viologen ligand Mn complex and a preparation method thereof, and belongs to the field of functional complex chemistry. Background Art

[0002] The optical properties of electrochromic materials show reversible changes controlled by external voltage changes, and the appearance shows changes in color or transparency. Compared with light, heat, and solvent-induced chromic materials, electrochromic materials are controlled by external voltage and have many advantages such as low energy consumption, no pollution, good fatigue resistance, and easy regulation. They have received widespread attention in many fields such as smart windows, electrochromic display devices, and anti-glare rearview mirrors.

[0003] Since the synergistic effect and structural diversity between organic and inorganic units in metal organic framework materials (MOFs) can provide favorable conditions for electron transfer, it has become an effective means to develop new electrochromic materials. When synthesizing MOFs materials with electrochromic properties, suitable ligands with redox activity are required. Among them, viologen derivatives (V 2+ , 1,1'-disubstituted-4,4'-bipyridyl salt) has redox activity, good electron accepting ability and reversible color change properties. If it is directly incorporated into MOFs materials as an organic ligand, it is expected to obtain MOFs materials with excellent electrochromic properties. No relevant reports have been seen so far. Summary of the invention

[0004] The invention aims to design and synthesize a single crystal of a metal Mn complex with a reversible electrochromic viologen ligand, so that the single crystal undergoes a reversible color change when a voltage is applied and can maintain a stable crystal structure.

[0005] To achieve the purpose of the present invention, the experimental scheme adopted by the present invention is:

[0006] The molecular formula of the Mn complex containing the viologen derivative is {[Mn(L)(H 2 O) 2 ](NO 3 )·2.5H 2 O} n (n>2). It belongs to the monoclinic system, C2 / c space group, and its crystal structure is as follows Figure 1 , where L is 3-(1,2,4-triazole-5-carboxylic acid)-4,4'-bipyridinium chloride, and the molecular structure is as follows:

[0007]

[0008] The method for preparing the above-mentioned single crystal of the viologen ligand-containing Mn complex is achieved by the following steps:

[0009] Step 1, synthesis of 1-(2,4-dinitrophenyl)-4,4'-bipyridine chloride: dissolve 4,4'-bipyridine and 1-chloro-2,4-dinitrobenzene in acetone, heat to reflux for reaction, cool naturally to room temperature after the reaction, filter and dry to obtain 1-(2,4-dinitrophenyl)-4,4'-bipyridine chloride.

[0010] Step 2, synthesis of 3-(1,2,4-triazole-5-carboxylic acid)-4,4'-bipyridinium chloride: dissolve 1-(2,4-dinitrophenyl)-4,4'-bipyridinium chloride and 3-amino-1,2,4-triazole-5-carboxylic acid in ethanol, heat to reflux for reaction, cool naturally to room temperature after the reaction is completed, remove the solvent, and obtain 3-(1,2,4-triazole-5-carboxylic acid)-4,4'-bipyridinium chloride through recrystallization.

[0011] Step 3, complex {[Mn(L)(H 2 O) 2 ](NO 3 )·2.5H 2 O} n Preparation of single crystal: 3-(1,2,4-triazole-5-carboxylic acid)-4,4'-bipyridinium chloride obtained in the above step was mixed with Mn(NO 3 ) 2 Add to the mixed solution of ethanol and water (V 乙醇 :V 水 =1:1), heated to react, cooled naturally after the reaction, filtered, and obtained the complex {[Mn(L)(H 2 O) 2 ](NO 3 )·2.5H 2 O} n Single crystal.

[0012] The molar ratio of 4,4'-bipyridine to 1-chloro-2,4-dinitrobenzene in step 1 is preferably 1:(1-1.2);

[0013] In step 2, the molar ratio of 1-(2,4-dinitrophenyl)-4,4'-bipyridyl chloride to 3-amino-1,2,4-triazole-5-carboxylic acid is preferably 1:1.3.

[0014] Step 3: 3-(1,2,4-triazole-5-carboxylic acid)-4,4'-bipyridyl chloride and Mn(NO 3 ) 2 The molar ratio is preferably 1:(1.5-2).

[0015] The present invention has the following beneficial effects:

[0016] 1. The viologen ligand Mn complex single crystal prepared by the present invention has reversible electrochromic properties. When the complex is loaded on ITO glass and an external voltage is applied, its color can undergo a reversible change from light yellow to dark purple, and can still maintain good stability and crystallinity after 20 consecutive cycles;

[0017] 2. The raw materials of the present invention are easily available, the synthesis steps are simple, the material cost is low, the operation reproducibility is good, and it is environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 For the complex {[Mn(L)(H 2 O) 2 ](NO 3 )·2.5H 2 O} n Coordination environment diagram;

[0019] Figure 2 For the complex {[Mn(L)(H 2 O) 2 ](NO 3 )·2.5H 2 O} n Schematic diagram of the structure;

[0020] Figure 3 For the complex {[Mn(L)(H 2 O) 2 ](NO 3 )·2.5H 2 O} n Photographs of electrochromic color changes;

[0021] Figure 4 For the complex {[Mn(L)(H 2 O) 2 ](NO 3 )·2.5H 2 O} n Cyclic voltammogram;

[0022] Figure 5 For the complex {[Mn(L)(H 2 O) 2 ](NO 3 )·2.5H 2 O} n PXRD before and after voltage application. DETAILED DESCRIPTION

[0023] The specific implementation modes of the present invention are further described in detail below in conjunction with examples, but the examples are not intended to limit the present invention.

[0024] Example 1

[0025] The method for preparing a single crystal of a viologen ligand Mn complex having reversible electrochromic properties comprises the following steps:

[0026] Step 1, synthesis of 1-(2,4-dinitrophenyl)-4,4'-bipyridine chloride: dissolve 6.0 g-38.4 mmol 4,4'-bipyridine and 8.0 g-39.4 mmol 1-chloro-2,4-dinitrobenzene in 150 mL acetone, reflux at 56° C. for 12 h, cool naturally to room temperature, filter and dry to obtain a light green solid 1-(2,4-dinitrophenyl)-4,4'-bipyridine chloride.

[0027] Step 2, synthesis of 3-(1,2,4-triazole-5-carboxylic acid)-4,4'-bipyridinium chloride: 1.4 g-3.9 mmol 1-(2,4-dinitrophenyl)-4,4'-bipyridinium chloride and 0.7 g-5 mmol 3-amino-1,2,4-triazole-5-carboxylic acid were dissolved in 60% by weight ethanol, refluxed at 80° C. for 24 h, cooled naturally to room temperature, the solvent was removed, and recrystallized to obtain a yellow powder 3-(1,2,4-triazole-5-carboxylic acid)-4,4'-bipyridinium chloride.

[0028] Step 3, {[Mn(L)(H 2 O) 2 ](NO 3 )·2.5H 2 O} n Single crystal preparation: 3-(1,2,4-triazole-5-carboxylic acid)-4,4'-bipyridinium chloride obtained in the above step was mixed with Mn(NO 3 ) 2 Add to V at a molar ratio of 1:1.5 乙醇 With V 水 = 1:1 in 4 ml of a mixed solution, reacted at 100°C for 3 days, cooled naturally, and filtered to collect light yellow block crystals, i.e., the complex {[Mn(L)(H 2 O) 2 ](NO 3 )·2.5H 2 O} n The single crystal of . It is simply recorded as complex 1.

[0029] Example 2

[0030] Preparation of single crystal of complex 1

[0031] Step 1, synthesis of 1-(2,4-dinitrophenyl)-4,4'-bipyridine chloride: dissolve 6.0 g-38.4 mmol 4,4'-bipyridine and 8.0 g-39.4 mmol 1-chloro-2,4-dinitrobenzene in 150 mL acetone, reflux at 56° C. for 12 h, cool naturally to room temperature, filter and dry to obtain a light green solid 1-(2,4-dinitrophenyl)-4,4'-bipyridine chloride.

[0032] Step 2, synthesis of 3-(1,2,4-triazole-5-carboxylic acid)-4,4'-bipyridinium chloride: 1.4 g-3.9 mmol 1-(2,4-dinitrophenyl)-4,4'-bipyridinium chloride and 0.7 g-5 mmol 3-amino-1,2,4-triazole-5-carboxylic acid were dissolved in 75% by weight ethanol, refluxed at 80° C. for 24 h, cooled naturally to room temperature, the solvent was removed, and recrystallized to obtain a yellow powder 3-(1,2,4-triazole-5-carboxylic acid)-4,4'-bipyridinium chloride.

[0033] Step 3, preparation of single crystal of complex 1: 3-(1,2,4-triazole-5-carboxylic acid)-4,4'-bipyridinium chloride obtained in the above step was reacted with Mn(NO 3 ) 2 Add to V at a molar ratio of 1:1.8 乙醇 With V 水 =1:1 in 4 ml of a mixed solution, react at 100°C for 3 days, cool naturally, and filter to collect light yellow block crystals, i.e., single crystals of complex 1.

[0034] Example 3

[0035] Preparation of single crystal of complex 1

[0036] Step 1, synthesis of 1-(2,4-dinitrophenyl)-4,4'-bipyridine chloride: dissolve 6.0 g-38.4 mmol 4,4'-bipyridine and 8.0 g-39.4 mmol 1-chloro-2,4-dinitrobenzene in 150 mL acetone, reflux at 56° C. for 12 h, cool naturally to room temperature, filter and dry to obtain a light green solid 1-(2,4-dinitrophenyl)-4,4'-bipyridine chloride.

[0037] Step 2, synthesis of 3-(1,2,4-triazole-5-carboxylic acid)-4,4'-bipyridinium chloride: 0.7 g-2 mmol 1-(2,4-dinitrophenyl)-4,4'-bipyridinium chloride and 0.35 g-2.5 mmol 3-amino-1,2,4-triazole-5-carboxylic acid were dissolved in 60% by weight ethanol, refluxed at 80° C. for 24 h, cooled naturally to room temperature, the solvent was removed, and recrystallized to obtain a yellow powder 3-(1,2,4-triazole-5-carboxylic acid)-4,4'-bipyridinium chloride.

[0038] Step 3, preparation of single crystal of complex 1: 3-(1,2,4-triazole-5-carboxylic acid)-4,4'-bipyridinium chloride obtained in the above step was reacted with Mn(NO 3 ) 2 Add to V in a molar ratio of 1:2 乙醇 :V 水 =1:1 in 4 ml of a mixed solution, react at 100°C for 3 days, cool naturally, and filter to collect light yellow block crystals, i.e., single crystals of complex 1.

[0039] The performance data of the complex single crystal prepared in Example 1 are used to illustrate the effect of the present invention. The specific crystal data are shown in Tables 1 and 2.

[0040] Table 1 Main crystallographic data of the single crystal of complex 1 obtained in Example 1

[0041]

[0042]

[0043] R 1 =∑||F o |-|F c || / ∑|F o |.wR 2 =[∑w(F o 2 -F c 2 ) 2 / ∑w(F o 2 ) 2 ] 1 / 2

[0044] Table 2 Important bond lengths and bond angles of the single crystal of complex 1 obtained in Example 1

[0045]

[0046]

[0047]

[0048] Application Examples

[0049] The complex prepared in Example 1 of the present invention was used as the object for testing. First, an ITO conductive film modified with complex 1 was prepared: complex 1 (30 mg) was taken, 0.30 mL of ethanol and 15 μL of 5% Nafion by mass were added to form a suspension, and the suspension was fully ground using a ball mill. The suspension was smeared on a cut FTO conductive glass of 1 cm×1.5 cm in size, and allowed to stand overnight in the dark to dry.

[0050] Cyclic voltammetry test of complex 1: The cyclic voltammetry was tested using a three-electrode system, with the ITO film modified with complex 1 as the working electrode, and the platinum mesh and the saturated potassium chloride solution of Ag / AgCl as the counter electrode and the reference electrode, respectively.

[0051] Figure 4 The cyclic voltammetry curve of complex 1 shows that when a voltage of 0.1V to -0.6V is applied, a pair of reversible redox peaks appear on the spectrum, which can be attributed to the redox reaction of the viologen derivative under the applied voltage, and this process is completely reversible. After 50 cycles, complex 1 still maintains good stability. To further verify the reversibility and stability of the ITO film, the powder diffraction (PXRD) of the ITO film before and after the voltage is applied is tested, see Figure 5 , and found that its crystallinity could remain intact.

Claims

1. A reversible electrochromic viologen ligand Mn complex single crystal, characterized in that: Belongs to the monoclinic system, C2 / c space group, a=10.5903(2) Å, b=28.4754(4) Å, c=13.8425(3) Å, α=90, β=112.306(3), γ=90, V=3862.02(15) Å 3 , the molecular formula is {[Mn(L)(H2O)2](NO3)·2.5H2O} n ; Wherein L is the ligand 3-(1,2,4-triazole-5-carboxylic acid)-4,4'-bipyridinium chloride, and the molecular structure of the L ligand is as follows: 。 2. A method for preparing a reversible electrochromic viologen ligand Mn complex single crystal as claimed in claim 1, characterized in that: This is accomplished by the following steps: (1) Synthesis of 1-(2,4-dinitrophenyl)-4,4'-bipyridine chloride: 4,4'-bipyridine and 1-chloro-2,4-dinitrobenzene are dissolved in acetone, heated under reflux for reaction, and naturally cooled to room temperature after the reaction is completed, filtered and dried to obtain 1-(2,4-dinitrophenyl)-4,4'-bipyridine chloride; (2) Synthesis of 3-(1,2,4-triazole-5-carboxylic acid)-4,4'-bipyridinium chloride: 1-(2,4-dinitrophenyl)-4,4'-bipyridinium chloride and 3-amino-1,2,4-triazole-5-carboxylic acid were dissolved in ethanol, heated under reflux for reaction, and naturally cooled to room temperature after the reaction was completed. The solvent was removed and recrystallized to obtain 3-(1,2,4-triazole-5-carboxylic acid)-4,4'-bipyridinium chloride; (3) Complex {[Mn(L)(H2O)2](NO3)·2.5H2O} n Preparation of single crystal: Add 3-(1,2,4-triazole-5-carboxylic acid)-4,4'-bipyridinium chloride and Mn(NO3)2 to a mixed solution of ethanol and water, heat to react, and after the reaction is completed, cool naturally and filter to obtain a Mn complex single crystal.

3. The method for preparing a reversible electrochromic viologen ligand Mn complex single crystal according to claim 2, characterized in that: The molar ratio of 4,4'-bipyridine to 1-chloro-2,4-dinitrobenzene in step (1) is 1:(1-1.2); In step (2), the molar ratio of 1-(2,4-dinitrophenyl)-4,4'-bipyridyl chloride to 3-amino-1,2,4-triazole-5-carboxylic acid is 1:1.3; The molar ratio of 3-(1,2,4-triazole-5-carboxylic acid)-4,4'-bipyridinium chloride to Mn(NO3)2 in step (3) is 1:(1.5-2).

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