Cobalt (II)-complex as well as preparation method and application thereof

Abstract

The invention relates to the technical field of laser materials, in particular to a cobalt (II)-complex and a preparation method and application thereof. The chemical formula of the coordination compound is CoC44H30N8O12, the abbreviation formula of the coordination compound is [Co (H2TBC) 2 (PDD) 2], H2TB is trimesic acid without monoprotons, and PDD is 3, 5-bis (4-pyridyl) pyrazole. A crystal of the complex belongs to a monoclinic system and a C2 / c space group, and cell parameters are as follows: # imgabs0 # imgabs1 # beta = 124.5900 (10) degrees and # imgabs2 #. In the complex, Co (II) ions are respectively coordinated with carboxyl oxygen atoms from two H2TBs and nitrogen atoms from two PDDs, so that mononuclear complex molecules are constructed. In addition, molecules of the complex are mutually connected through hydrogen bonds, so that a stable three-dimensional supramolecular structure is formed; the preparation method is simple and easy to operate and low in cost, and the prepared complex can be applied to optical devices in the fields of ultrashort pulse lasers, fiber lasers and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of excimer materials, and in particular to a cobalt (II) complex and a preparation method and application thereof. Background Art

[0002] The third-order nonlinear optical effect has important application value in the fields of laser technology, optical information processing, optical communication, etc. Among them, saturation absorption, as a typical third-order nonlinear phenomenon, can achieve passive laser mode locking and Q switching through the absorption characteristics of light intensity dependence, thereby generating ultrashort pulses (picosecond / femtosecond level). At present, commercial saturation absorption materials (such as semiconductor saturable absorption mirrors SESAM, organic dyes, Cr 4+ :YAG crystals, etc.) have obvious defects: SESAM preparation process is complex, costly and has strong band limitation; organic dyes have poor thermal stability and are easy to degrade. Therefore, the development of new saturation absorption materials with low cost and high stability has become a current research hotspot. Cobalt (II) complexes have high stability due to their tetrahedral coordination structure and d 7 The high spin arrangement of electronic configuration has attracted much attention in optical, electrical and magnetic functional materials. A typical example is K2[Co(SCN)4], in which the central Co 2+ The ion is located at the center of the tetrahedral field and is bound to the four SCNs by strong coordination bonds. - Ions combine to form an inert complex. This structure makes it difficult to dissociate under acid / base conditions, and its thermal stability is significantly better than that of transition metal complexes such as Ni(II) (such as (Ni(NH3)6)Cl2 rapidly decomposes in acid). Existing studies have shown that the ligand type and coordination environment of cobalt complexes can significantly regulate their optical properties. For example, by introducing organic ligands containing conjugated structures (such as 2,2'-bipyridine, such as 4,4'-bipyridine, etc.), metal-organic frameworks (MOFs) or coordination polymers can be formed, thereby enhancing the nonlinear optical activity of the material. Based on the above background, the present invention focuses on the molecular structure design of cobalt (II) complexes, and constructs new complexes by introducing conjugated bridging ligands, aiming to achieve the following breakthroughs: regulating the electronic transition energy level of the complex through ligand engineering to expand its saturation absorption band; utilizing Co in the tetrahedral field to obtain the optical properties of the complex. 2+ ion dd transition characteristics, reducing the photoexcitation threshold of the material; through the rigid ligand and Co 2+ The strong coordination effect improves the thermal stability and anti-light aging performance of the material.

[0003] The present invention is dedicated to developing a new third-order nonlinear material with high stability, low threshold and strong third-order nonlinear saturation absorption, so as to solve the problems existing in the prior art such as complex process, low stability and low third-order nonlinear saturation absorption, and promote the innovation of ultrashort pulse lasers and fiber lasers. Summary of the Invention

[0004] In order to comprehensively solve the above problems, the purpose of the present invention is to overcome the defects of the prior art and provide a simple and easy-to-operate cobalt (II) complex and its preparation method and application. The method has low manufacturing cost and high stability. The prepared material has a strong third-order nonlinear optical saturation absorption effect. The third-order nonlinear saturation absorption coefficient of the material is -3.14×10 -5 m / W, third-order nonlinear susceptibility χ (3) 5.06×10 -7 ESU can be widely used in device preparation in the fields of ultrashort pulse lasers, fiber lasers, etc.

[0005] In order to achieve the above object, the first aspect of the present invention provides a cobalt (II) complex having the chemical formula CoC 44 H 30 N8O 12 , the abbreviation is [Co(H2TBC)2(PDD)2], where H2TB is deprotonated trimesic acid and PDD is 3,5-di(4-pyridyl)pyrazole;

[0006] The crystal structure of the complex belongs to the monoclinic system, C2 / c space group, and the unit cell parameters are: β=124.5900(10)°,

[0007] A second aspect of the present invention provides a method for preparing a cobalt (II) complex, comprising the following steps:

[0008] Step 1: Place a transition metal salt containing Co(II), trimesic acid, 3,5-di(4-pyridyl)pyrazole, and distilled water into a reaction kettle, stir, adjust the pH value of the reaction solution with NaOH, and seal the reaction kettle;

[0009] Step 2: The reactor in step 1 was reacted under constant temperature. After the reaction was completed, the reactor was naturally cooled to room temperature, the reaction liquid was filtered, and the filter cake was washed with water and ethanol to obtain red block crystals, which were naturally dried in the air to obtain red block CoC 44 H 30 N8O 12 solid.

[0010] Preferably, in step 1, the molar ratio of the transition metal salt containing Co(II), trimesic acid, 3,5-di(4-pyridyl)pyrazole and distilled water is 2:1:2:500.

[0011] Preferably, the transition metal salt containing Co(II) in step 1 is any one of cobalt acetate tetrahydrate, cobalt chloride hexahydrate, cobalt nitrate hexahydrate or cobalt sulfate heptahydrate.

[0012] Preferably, in step 1, the pH value of the reaction solution is adjusted to 4-5 by NaOH.

[0013] Preferably, the reaction temperature of the reactor in step 2 is 160° C. and the reaction time is 72 h.

[0014] The cobalt(II) complex prepared according to the above steps is stable below 400°C.

[0015] A third aspect of the present invention provides a cobalt (II) complex for use in preparing ultrashort pulse lasers and fiber laser devices.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. The present invention successfully prepared CoC 44 H 30 N8O 12 , prepared from three raw materials: a transition metal salt of cobalt(II), trimesic acid, and PDD (3,5-di(4-pyridyl)pyrazole). This compound is distinguished from other compounds by its unit cell parameters. The cobalt(II) complex crystal belongs to the monoclinic system, C2 / c space group, and the unit cell parameters are: β=124.5900(10)°,

[0018] 2. CoC prepared by the present invention 44 H 30 N8O 12 The Co(II) ion coordinates with the carboxyl oxygen atoms from two H2TBs and the nitrogen atoms from two PDDs, respectively, to form a mononuclear complex molecule. Furthermore, the complex molecules are interconnected by hydrogen bonds, forming a stable three-dimensional supramolecular structure.

[0019] 3. The raw materials of the present invention are simple, the preparation method is simple and easy to operate, the cost is low, and no special precursor preparation is required. Instead, the material can be directly prepared in one pot. The material has high stability and is stable below 400 degrees. The material has a strong third-order nonlinear saturation absorption effect, and the third-order nonlinear saturation absorption coefficient is -3.14×10 -5 m / W, third-order nonlinear susceptibility χ (3) 5.06×10 -7 The synthesized materials can be used to prepare optical devices in fields such as ultrashort pulse lasers and fiber lasers. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0021] In the attached figure:

[0022] Figure 1 Schematic diagram of the coordination configuration and ligand connection method of the present invention;

[0023] Figure 2 is the ultraviolet-visible region electronic absorption spectrum of the present invention;

[0024] Figure 3 The thermal stability diagram of the present invention is

[0025] Figure 4 is the third-order nonlinear optical saturation absorption diagram of the present invention; DETAILED DESCRIPTION

[0026] The following combination Figures 1-4 It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0027] The first aspect of the present invention provides a cobalt (II) complex having the chemical formula CoC 44 H 30 N8O 12 , the abbreviation is [Co(H2TBC)2(PDD)2], where H2TB is deprotonated trimesic acid and PDD is 3,5-di(4-pyridyl)pyrazole;

[0028] The cobalt (II) complex crystallizes in the monoclinic system, in the C2 / c space group, with unit cell parameters: β=124.5900(10)°,

[0029] like Figure 1 As shown, Figure 1 The coordination configuration of the metal ion and the connection mode of the ligand in the structural unit of the present invention are clearly shown. The structure of the coordination polymer includes a cobalt (II) ion, two deprotonated trimesic acid molecules, and two PDD molecules.

[0030] In the structure, the cobalt(II) ion adopts a four-coordinate tetrahedral coordination configuration. The cobalt(II) ion is coordinated with oxygen atoms from two H2TBC molecules and nitrogen atoms from two PDD molecules, completing the four-coordinate tetrahedral configuration. The complex molecules are connected by hydrogen bonds, forming a three-dimensional supramolecular structure.

[0031] Elemental analysis of the coordination polymer: theoretical value (%): C, 57.46; H, 3.07; N, 12.18; experimental value (%): C, 57.42; H, 3.08; N, 12.13. Infrared spectrum (KBr, cm -1 ): 3445(s), 1610(s), 1434(w), 1374(w), 1158(w), 982(w), 707(w).

[0032] A method for preparing a cobalt (II) complex comprises:

[0033] Step 1: Add a cobalt (II)-containing transition metal salt, trimesic acid, 3,5-di(4-pyridyl)pyrazole, and distilled water in a molar ratio of 2:1:2:500 into a reactor, stir for 20 minutes, adjust the pH of the reaction solution to 4-5 with NaOH, and seal the reactor;

[0034] Step 2: The reactor in step 1 was reacted at a constant temperature of 160°C for 72 hours. After the reaction, the reactor was naturally cooled to room temperature, the reaction liquid was filtered, and the filter cake was washed with water and ethanol to obtain red block crystals, which were naturally dried in the air to obtain red block CoC 44 H 30 N8O 12 solid.

[0035] Furthermore, the transition metal salt containing cobalt (II) in step 1 is any one of cobalt acetate tetrahydrate, cobalt chloride hexahydrate, cobalt nitrate hexahydrate or cobalt sulfate heptahydrate.

[0036] The cobalt (II) complex prepared by the above method is stable below 400 degrees and can be used to prepare optical devices in the fields of ultrashort pulse lasers, fiber lasers, etc.

[0037] Example 1:

[0038] A method for preparing a cobalt (II) complex comprises:

[0039] Step 1: Cobalt acetate tetrahydrate (0.2 mmol, 0.05 g), trimesic acid (0.1 mmol, 0.021 g), 3,5-di(4-pyridyl)pyrazole (0.2 mmol, 0.044 g) and distilled water (9 ml) were placed in a reactor and stirred for 20 min. The pH of the reaction solution was adjusted to 5.0 with NaOH (0.4 mmol, 0.016 g), and the reactor was sealed.

[0040] Step 2: The reactor in step 1 was reacted at a constant temperature of 160°C for 72 hours. After the reaction, the reactor was naturally cooled to room temperature, the reaction liquid was filtered, and the filter cake was washed with water and ethanol to obtain red block crystals, which were naturally dried in the air to obtain red block CoC 44 H 30 N8O 12 solid.

[0041] The yield of the cobalt (II) complex prepared in this example was 82%. The powder diffraction pattern of the solid prepared in this example was consistent with the simulated pattern of single crystal structure analysis, confirming that the obtained solid was the target compound.

[0042] Example 2:

[0043] A method for preparing a cobalt (II) complex comprises:

[0044] Step 1: Cobalt chloride hexahydrate (0.2 mmol, 0.048 g), trimesic acid (0.1 mmol, 0.021 g), 3,5-di(4-pyridyl)pyrazole (0.2 mmol, 0.044 g), and distilled water (9 ml) were placed in a reactor and stirred for 20 min. The pH of the reaction solution was adjusted to 4.0 with NaOH (0.4 mmol, 0.016 g), and the reactor was sealed.

[0045] Step 2: The reactor in step 1 was reacted at a constant temperature of 160°C for 72 hours. After the reaction, the reactor was naturally cooled to room temperature, the reaction liquid was filtered, and the filter cake was washed with water and ethanol to obtain red block crystals, which were naturally dried in the air to obtain red block CoC 44 H 30 N8O 12 solid.

[0046] The yield of the cobalt (II) complex prepared in this example was 73%. The powder diffraction pattern of the solid prepared in this example was consistent with the simulated pattern of single crystal structure analysis, confirming that the obtained solid was the target compound.

[0047] Example 3:

[0048] A method for preparing a cobalt (II) complex comprises:

[0049] Step 1: Cobalt nitrate hexahydrate (0.2 mmol, 0.058 g), 5-pyromellitic acid (0.1 mmol, 0.021 g), 3,5-di(4-pyridyl)pyrazole (0.2 mmol, 0.044 g), and distilled water (9 ml) were placed in a reactor and stirred for 20 min. The pH of the reaction solution was adjusted to 5.0 with NaOH (0.4 mmol, 0.016 g), and the reactor was sealed.

[0050] Step 2: The reactor in step 1 was reacted at a constant temperature of 160°C for 72 hours. After the reaction, the reactor was naturally cooled to room temperature, the reaction liquid was filtered, and the filter cake was washed with water and ethanol to obtain red block crystals, which were naturally dried in the air to obtain red block CoC 44 H 30 N8O 12 solid.

[0051] The yield of the cobalt (II) complex prepared in this example was 81%. The powder diffraction pattern of the solid prepared in this example was consistent with the simulated pattern of single crystal structure analysis, confirming that the obtained solid was the target compound.

[0052] Example 4:

[0053] A method for preparing a cobalt (II) complex comprises:

[0054] Step 1: Cobalt sulfate heptahydrate (0.2 mmol, 0.056 g), 5-pyromellitic acid (0.1 mmol, 0.021 g), 3,5-di(4-pyridyl)pyrazole (0.2 mmol, 0.044 g), and distilled water (9 ml) were placed in a reactor and stirred for 20 min. The pH of the reaction solution was adjusted to 5.0 with NaOH (0.4 mmol, 0.016 g), and the reactor was sealed.

[0055] Step 2: The reactor in step 1 was reacted at a constant temperature of 160°C for 72 hours. After the reaction, the reactor was naturally cooled to room temperature, the reaction liquid was filtered, and the filter cake was washed with water and ethanol to obtain red block crystals, which were naturally dried in the air to obtain red block CoC 44 H 30 N8O 12 solid.

[0056] The yield of the cobalt (II) complex prepared in this example was 56%. The powder diffraction pattern of the solid prepared in this example was consistent with the simulated pattern of single crystal structure analysis, confirming that the obtained solid was the target compound.

[0057] Experimental characterization of target product:

[0058] 1. Crystallographic data of cobalt(II) complexes

[0059] Select crystals of appropriate size from the product of Example 1 and place them on a SMART 1K CCD diffractometer to collect diffraction intensity data. Mo Kα rays monochromatized by a graphite monochromator were used to Diffraction intensity data were collected using a scanning method at a test temperature of 25°C. All diffraction intensity data were corrected for Lp absorption factors and multiple scan absorption corrections. Initial structural model analysis and calculations were performed using the SHELXS-97 structure analysis program using a direct method. The structures were then solved using the SELXL-97 structure analysis program and refined using full-matrix least-squares methods. All non-hydrogen atoms were corrected using anisotropy parameters. Hydrogen atoms in all compounds were treated using theoretical hydrogenation methods. Crystallographic parameters and diffraction data collection conditions are shown in Table 1 below.

[0060] Table 1 Crystallographic data of cobalt (II) complexes

[0061]

[0062]

[0063] 2. UV-visible electronic absorption spectrum of the target product

[0064] Take 30 mg of the target product in Example 2, place it in a mortar, and grind it carefully until the particle size of the solid is less than 1 micron. Test the solid diffuse reflectance spectrum of the target product, as shown in the attached figure. Figure 2 As shown in the figure, the compound exhibits strong absorption at 286 nm. This absorption is attributed to π…π* absorption. The compound also exhibits absorption at 369 nm, which is attributed to the LMCT transition within the compound. The compound also exhibits absorption at 524 nm, also attributable to LMCT absorption. The solid diffuse reflectance results for the compound indicate that the compound has some absorption in the visible region and is prone to resonant absorption in strong photoelectric fields.

[0065] 3. Thermal stability analysis of target products

[0066] 20 mg of the target product from Example 3 was heated from room temperature to 800°C in an air atmosphere at a rate of 10°C / minute. As can be seen from the graph, the target compound rapidly decomposes above 409°C. Therefore, the compound is stable below 400°C.

[0067] 4. Analysis of the third-order nonlinear optical activity of the target product

[0068] Similarly, 50 mg of the target product from Example 4 was weighed and placed in a mortar and ground carefully until the solid particles had a particle size of approximately less than 1 μm. The solid was dispersed in 20 ml of ethanol using an ultrasonic device. The sample was then spin-coated onto a silica-based glass slide using a conventional spin coating method (spin coater speed 1000 rpm). The coating thickness was measured using a thickness meter and was found to be 4 μm.

[0069] The silica-based glass slide coated with the sample with a thickness of 4 μm prepared above was placed on a third-order nonlinear optical tester to test the third-order nonlinear optical properties of the compound.

[0070] The laser used in the experiment was 7 nanoseconds, with a wavelength of 532 nanometers and a frequency of 10 Hz. A single-beam Z-scan method was used to measure the third-order nonlinear optical activity of the material. The power density irradiated onto the sample at the focus was 0.00215 GW / cm 2 .

[0071] Under this condition, the material exhibits a strong third-order nonlinear optical saturation absorption effect. The third-order nonlinear saturation absorption coefficient of the material is -3.14×10 -5 m / W, third-order nonlinear susceptibility χ (3) 5.06×10 -7 esu, the third-order nonlinear saturation absorption test results are as follows Figure 4 This value is much larger than the nonlinear polarizability of existing inorganic semiconductors and organic copolymers.

[0072] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A cobalt(II) complex, characterized in that: The chemical formula of the complex is CoC 44 H 30 N8O 12 , the abbreviation is [Co(H2TBC)2(PDD)2], where H2TB is deprotonated trimesic acid and PDD is 3,5-di(4-pyridyl)pyrazole; The cobalt (II) complex crystallizes in the monoclinic system, in the C2 / c space group, with unit cell parameters: β=124.5900(10)°, 2. A method for preparing a cobalt (II) complex, characterized in that: include: Step 1: Place a transition metal salt containing Co(II), trimesic acid, 3,5-di(4-pyridyl)pyrazole, and distilled water into a reaction kettle, stir, adjust the pH value of the reaction solution with NaOH, and seal the reaction kettle; Step 2: The reactor in step 1 was reacted under constant temperature. After the reaction was completed, the reactor was naturally cooled to room temperature, the reaction liquid was filtered, and the filter cake was washed with water and ethanol to obtain red block crystals, which were naturally dried in the air to obtain red block CoC 44 H 30 N8O 12 solid.

3. The method for preparing a cobalt (II) complex according to claim 2, characterized in that: In step 1, the molar ratio of the transition metal salt containing Co(II), trimesic acid, 3,5-di(4-pyridyl)pyrazole and distilled water is 2:1:2:

500.

4. The method for preparing a cobalt (II) complex according to claim 3, characterized in that: In step 1, the transition metal salt containing Co(II) is any one of cobalt acetate tetrahydrate, cobalt chloride hexahydrate, cobalt nitrate hexahydrate or cobalt sulfate heptahydrate.

5. The method for preparing a cobalt (II) complex according to claim 2, characterized in that: In step 1, the pH value of the reaction solution is adjusted to 4-5 by adding NaOH.

6. The method for preparing a cobalt (II) complex according to claim 2, characterized in that: The reaction temperature of the reactor in step 2 is 160°C and the reaction time is 72h.

7. A method for preparing a cobalt (II) complex as claimed in claim 2, characterized in that The prepared cobalt(II) complex is stable below 400°C.

8. Use of a cobalt (II) complex prepared by the method according to any one of claims 2 to 6, characterized in that: It is used to prepare optical devices in the fields of ultrashort pulse lasers, fiber lasers, etc.

Images