Organic-inorganic hybrid iodogermanium cluster crystal material, preparation method and application thereof

Abstract

The application provides an organic-inorganic hybrid iodine-germanium cluster crystal material, a preparation method and application thereof, a general formula of the crystal material is (A)4Ge5I 18 , A is an organic amine cation, and the organic amine cation is selected from polyamino-substituted C4-C5 saturated monocyclic nitrogen heterocyclic cations. The crystal material provided by the application takes a discrete multi-nuclear [Ge5I 18 ] 8‑ cluster as a non-organic building unit, the SHG response intensity is about 0.6-0.7 times of KDP, the crystal material has stable second-order nonlinear optical activity and good functional consistency, can provide a new material system for the design of hybrid nonlinear optical materials, and the optical band gap of the crystal material is between 2.6-2.8 eV, has stable and adjustable optical properties, is in a suitable optical band gap range, and has application potential in the fields of laser frequency doubling, frequency conversion and optoelectronic functional devices.

Description

Technical Field

[0001] This invention belongs to the field of crystal materials technology, specifically providing a class of organic-inorganic hybrid iodine-germanium cluster crystal materials, their preparation methods, and applications. Background Technology

[0002] Organic-inorganic hybrid halide materials combine the designability of the organic component with the optoelectronic properties of the inorganic component, attracting widespread attention in recent years in fields such as nonlinear optics, luminescence, photoelectric conversion, and ferroelectricity. For second-order nonlinear optical materials, a bulk second harmonic response typically requires a non-centrosymmetric crystal structure. In existing technologies, inducing the formation of non-centrosymmetric hybrid halide structures by introducing enantiochiral organic cations is one common approach to obtaining second harmonic responses. Furthermore, Ge... 2+ Sn 2+ Sb 3+ and Bi 3+ Main clan ns 2+ Metal ions, due to their high polarizability and stereochemically active lone pairs of electrons, are conducive to inducing local coordination distortion and charge distribution asymmetry, thus facilitating the construction of non-centrosymmetric structural units. Compared with lead-based systems, germanium-based halide materials have lower toxicity and certain environmental advantages, and are gradually becoming one of the important research directions in the field of hybrid halides.

[0003] However, existing technologies still have the following shortcomings: First, the chiral cation route is limited by the high cost of obtaining enantiomers, the limited candidate cation library, and the complex preparation process; second, the existing germanium-based hybrid halides have relatively limited structural types, which restricts the development of crystal materials; third, the regulation of the crystal structure and second-order nonlinear optical response of iodine-germanium clusters by organic template agents in different chiral states is still unclear, and whether non-centrosymmetric structures can be stably obtained and reproducible second harmonic responses can be generated under racemic or achiral conditions still lacks systematic research.

[0004] Therefore, it is necessary to develop a new type of iodine-germanium cluster crystal material with novel structure, stable non-centrosymmetric configuration, simple preparation route, and potential for nonlinear optical applications. Summary of the Invention

[0005] This invention aims to at least partially address one of the technical problems in the prior art. Therefore, one objective of this invention is to propose a class of organic-inorganic hybrid iodine-germanium cluster crystal materials, their preparation methods, and applications, in order to solve the problems of high material cost, complex processes, and limited structural types in the preparation of existing non-centrosymmetric crystal structures.

[0006] In a first aspect, the present invention discovers a class of organic-inorganic hybrid iodine-germanium cluster crystal materials, the general formula of which is (A)4Ge5I.18 A is an organic amine cation, which is selected from polyamino-substituted C4-C5 saturated monocyclic nitrogen heterocyclic cations.

[0007] The inventors discovered that, through specific organic amine cations, a product with the general formula (A)4Ge5I is formed. 18 The crystalline materials described herein are all crystallized in a non-centrosymmetric space group, exhibiting a non-centrosymmetric crystal structure. The organic amine cations can be chiral or racemic, overcoming the limitations of existing chiral cation routes, which are constrained by high enantiomeric acquisition costs and a limited candidate cation library. In particular, the crystalline materials formed by chiral or racemic cations can generate reproducible second harmonic responses, possessing potential for nonlinear optical applications. Furthermore, the (A)4Ge5I provided by this invention... 18 Using multinuclear discrete iodine-germanium clusters as inorganic building blocks, specifically, the inorganic building blocks are discrete multinuclear [Ge5I] 18 ] 8- Cluster, the [Ge5I 18 ] 8- The cluster consists of a central divalent Ge atom and four terminal divalent Ge atoms. Each Ge atom coordinates with surrounding I atoms to form a distorted octahedral coordination configuration. The central GeI6 octahedron and the four terminal GeI6 octahedrons are connected through face sharing, forming a discrete five-nuclear zero-dimensional cluster unit. 18 ] 8- There is no Ge-I covalent bond between the clusters; the organic amine cation fills the inter-cluster voids and is linked to [Ge5I] via NH···I hydrogen bonds. 18 ] 8- Cluster interactions collectively construct a non-centrosymmetric crystal structure, organizing into a macroscopically non-centrosymmetric stack in a non-cancelling manner, thereby generating a stable second-order nonlinear optical response. This invention broadens the structural types of germanium-based hybrid halides and discovers a novel class of iodine-germanium cluster crystal materials.

[0008] Furthermore, the crystal material provided by this invention exhibits a second harmonic response, the response intensity of which is 0.6-0.7 times that of potassium dihydrogen phosphate (KH₂PO₄, KDP). The responses of enantiomeric, racemic, and chiral cation-guided samples obtained by this invention are on the same order of magnitude, with no significant difference, indicating that the second-order nonlinear optical activity of the iodine-germanium cluster crystal material of this invention is [Ge₅I₂]. 18 ] 8- The dominant electronic asymmetry driven by lone pair electrons of Ge(II) within the cluster means that the molecular chirality of the organic cation is not a necessary condition for obtaining the second harmonic generation (SHG) response, thus breaking through the limitation of enantiomeric chiral cations in the prior art.

[0009] In some embodiments of the present invention, the organic amine cation includes ( R )-3-aminopyrrolidine cation (abbreviated as) R -3AP), ( S )-3-aminopyrrolidine cation (abbreviated as) S -3AP), racemic 3-aminopyrrolidine cation ( rac One of the following is a cation: -3AP, 4-aminopiperidine cation (4APD). Racemic and chiral cation-directed crystal materials can also be stably crystallized in non-centrosymmetric space groups and exhibit SHG responses of the same order as enantiomeric pure samples, indicating that the second-order nonlinear optical activity of this type of material is similar to that of [Ge5I]. 18 ] 8- The structural characteristics and electronic distribution characteristics of the cluster unit are related, but not entirely dependent on the molecular chirality of organic cations, providing a new material system for the design of hybrid nonlinear optical materials that do not require enantiomeric separation.

[0010] Further, the organic amine cation is ( R When the cation is 3-aminopyrrolidine, the cell parameters of the crystal material are: a = 11.9487(4) Å, b = 12.1379(5) Å, c = 21.8680(7) Å, α = β = γ = 90°, V = 3171.6(2) Å 3 , Z = 2. The organic amine cation is ( S When the cation is 3-aminopyrrolidine, the cell parameters of the crystal material are: a = 11.9707(4) Å, b = 12.1350(5) Å, c = 21.8997(7) Å, α = β = γ =90°, V = 3181.2(2) Å 3 , Z = 2. When the organic amine cation is a racemic 3-aminopyrrolidine cation, the cell parameters of the crystal material are: a = b = 11.9651(2) Å, c = 21.8862(5) Å, α = β = γ= 90°, V =3133.31(13) Å 3 , Z = 2. When the organic amine cation is a 4-aminopiperidine cation, the cell parameters of the crystal material are: a = b = 12.1793(3) Å, c = 22.8357(12) Å, α = β = γ = 90°, V = 3387.3(3)Å 3 , Z = 2.

[0011] Further, the organic amine cation is ( R )-3-aminopyrrolidine cation or ( S When the 3-aminopyrrolidine cation is present, the crystalline material crystallizes in an orthorhombic crystal system. I Space group 222. When the organic amine cation is a racemic 3-aminopyrrolidine cation or a 4-aminopiperidine cation, the crystalline material crystallizes in the tetragonal crystal system. I -42 m Space group.

[0012] Further, the organic amine cation is ( R When the organic amine cation is 3-aminopyrrolidine, the optical band gap of the crystal material is 2.78 eV. S When the organic amine cation is a racemic 3-aminopyrrolidine cation, the optical band gap of the crystal material is 2.75 eV. When the organic amine cation is a racemic 3-aminopyrrolidine cation, the optical band gap of the crystal material is 2.79 eV. When the organic amine cation is a 4-aminopiperidine cation, the optical band gap of the crystal material is 2.68 eV. The above four crystal materials exhibit good phase purity, and the PXRD measured spectra are basically consistent with the single-crystal simulated spectra. The band gaps of the four materials are similar and within a suitable optical band gap range, indicating that this type of material has stable and tunable optical properties.

[0013] Further, the organic amine cation is ( R )-3-aminopyrrolidine cation, ( S When the crystalline material is a 3-aminopyrrolidine cation or a racemic 3-aminopyrrolidine cation, the molecular formula of the crystalline material is (C4H4H4) 12 N2)4Ge5I 18 The molecular weight is 2999.77. When the organic amine cation is a 4-aminopiperidine cation, the molecular formula of the crystalline material is (C5H...14 N2)4Ge5I 18 Its molecular weight is 3055.87.

[0014] In a second aspect, the present invention provides a method for preparing the above-mentioned organic-inorganic hybrid iodine-germanium cluster crystal material, comprising: After mixing HI aqueous solution and H3PO2 aqueous solution, GeO2 is added, and the mixture is heated and stirred at a first temperature to obtain a precursor solution. After adding organic amine dihydrochloride template agent to the precursor solution, it is kept at a second temperature, and after the heat preservation is completed, it is cooled to room temperature and allowed to stand.

[0015] This invention employs a solvothermal method, dissolving GeO2 in a mixed solution of HI and H3PO2 and heating to form a homogeneous germanium-iodine precursor solution. An organic amine dihydrochloride template agent is then added, and the solution is kept at a constant temperature in a sealed reactor. After programmed cooling and settling at room temperature, the target crystal is obtained. The method provided by this invention is simple, the conditions are controllable, and it can obtain high-purity yellow blocky crystals suitable for single-crystal structure characterization.

[0016] In some embodiments of the present invention, the molar ratio of HI in the HI aqueous solution to H3PO2 in the H3PO2 aqueous solution is (1-2):1. For example, the molar ratio is 1:1, 1.5:1, 2:1, etc., or any range between the two values ​​mentioned above.

[0017] In some embodiments of the present invention, the mass concentration of the HI aqueous solution is 50-60%.

[0018] In some embodiments of the present invention, the mass concentration of the H3PO2 aqueous solution is 45-55%.

[0019] In some embodiments of the present invention, the first temperature is 110-130°C, and the heating and stirring time at the first temperature is 20-40 minutes. For example, the first temperature is 110°C, 115°C, 120°C, 125°C, 130°C, etc., or any range between any two of the above values; the heating and stirring time is 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, etc., or any range between any two of the above values.

[0020] In some embodiments of the present invention, the organic amine dihydrochloride template agent includes ( R )-3-aminopyrrolidine dihydrochloride, ( S One of 3-aminopyrrolidine dihydrochloride, racemic 3-aminopyrrolidine dihydrochloride, and 4-aminopiperidine dihydrochloride.

[0021] In some embodiments of the present invention, the molar ratio of GeO2 to the organic amine dihydrochloride template agent is (6-4):4. For example, the molar ratio is 6:4, 5:4, 4:4, etc., or any range between the two values ​​mentioned above.

[0022] In some embodiments of the present invention, the second temperature is 80-100°C, and the temperature is maintained at the second temperature for 1.5-2.5 hours. For example, the second temperature is 80°C, 85°C, 90°C, 95°C, 100°C, etc., or any range between any two of the above values; the maintenance time at the second temperature is 1.5 hours, 2 hours, 2.5 hours, etc., or any range between any two of the above values.

[0023] In some embodiments of the present invention, the cooling rate to room temperature after the heat preservation is completed is 3-5℃·h. -1 .

[0024] In some embodiments of the present invention, the time for cooling to room temperature and standing after the heat preservation is completed is 20h-30h.

[0025] In a third aspect, the present invention proposes the application of the above-described organic-inorganic hybrid iodine-germanium cluster crystal material or the organic-inorganic hybrid iodine-germanium cluster crystal material prepared by the above method in laser frequency doubling devices, optical parametric oscillators, frequency conversion devices or second harmonic generation devices.

[0026] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects: (1) This invention provides a class of discrete multi-core [Ge5I] 18 ] 8- The cluster is an organic-inorganic hybrid iodine-germanium cluster crystal material with inorganic building blocks. The [Ge5I] 18 ] 8- The cluster is composed of five GeI6 octahedra connected together, forming a novel discrete multinuclear iodine-germanium framework that is different from the existing common germanium-based hybrid halide structures, thus expanding the structural types and composition range of germanium-based hybrid halide materials.

[0027] (2) This invention demonstrates, through the systematic construction of three types of organic amine templates—enantiomeric, racemic, and achiral—that racemic and achiral cation-directed iodine-germanium cluster crystal materials can also crystallize in a non-centrosymmetric space group and exhibit SHG responses on the same order of magnitude as the enantiomeric samples. This illustrates the second-order nonlinear optical activity of the system of this invention compared to [Ge5I] 18 ] 8- The structure and electronic distribution characteristics of cluster units are related, providing new experimental evidence for understanding the structure-property relationship of this type of material.

[0028] (3) This invention provides a preparation route for hybrid iodine-germanium cluster crystal materials with second-order nonlinear optical activity without enantiomeric separation. The SHG response intensities of the four representative compounds are on the same order of magnitude, approximately 0.6-0.7 times that of KDP, indicating that these materials have relatively stable second-order nonlinear optical activity and good functional consistency, and can provide a new material system for the design of hybrid nonlinear optical materials.

[0029] (4) The preparation method of the present invention is simple and the conditions are controllable. The yellow blocky crystal with good phase purity and suitable for single crystal structure characterization can be obtained by using the solvothermal method under closed conditions. The PXRD measured spectrum of the obtained sample is basically consistent with the single crystal simulated spectrum, indicating that the sample has good phase purity, and the method has good repeatability and potential for promotion.

[0030] (5) The optical band gaps of the four materials obtained in this invention are 2.78 eV, 2.75 eV, 2.79 eV and 2.68 eV, respectively, indicating that these materials have relatively stable and tunable optical properties and are in a relatively suitable optical band gap range, and have application potential in the fields of laser frequency doubling, frequency conversion and optoelectronic functional devices. Attached Figure Description

[0031] Figure 1 These are single-crystal photographs of the multinuclear iodine-germanium cluster crystal materials obtained in Examples 1-4 of this invention; Figure 2 These are schematic diagrams of the single-crystal structures of the crystal materials in Examples 1 and 3 of the present invention; Figure 3 These are comparison diagrams of the measured and simulated PXRD spectra of the crystal materials in Examples 1-4 of this invention; Figure 4 The Tauc diagrams are of the crystal materials in Examples 1-4 of this invention; Figure 5 The diagram shows a comparison of the powder second harmonic response of the crystal material and the KDP reference material in Examples 1-4 of this invention. Detailed Implementation

[0032] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention. The invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the invention in any way.

[0033] All reagents and solvents used in this invention are commercially available and can be used directly. Operations involving concentrated HI and H3PO2 are preferably performed in a fume hood with appropriate personal protective measures. After a closed solvothermal reaction is completed, the reactor should be cooled to room temperature and stabilized before being opened. Unless otherwise stated, all temperatures in this invention are in Celsius.

[0034] Example 1 This embodiment provides a crystal material with the chemical formula ( ). R -3AP)4Ge5I 18 Its preparation method is as follows.

[0035] 4.0 mL of a 57% (w / w) HI aqueous solution and 4.0 mL of a 50% (w / w) H3PO2 aqueous solution were mixed in a 15 mL screw-top flask, and 0.523 g (5.0 mmol) of GeO2 was added. The flask was sealed and heated at 120 °C with magnetic stirring for 30 min until a homogeneous, light yellow solution was formed. Then, the hot solution was transferred to a 15 mL polytetrafluoroethylene-lined stainless steel reactor, and (… R 0.636 g (4.0 mmol) of 3AP·2HCl was sealed and heated at 100 °C for 2 h, followed by heating at 1 °C·h. -1 The solution was slowly cooled to room temperature and allowed to stand at room temperature for 24 hours to obtain yellow blocky crystals. The chemical formula of the obtained crystals is (C4H4H2O). 12 N2)4Ge5I 18 Its molecular weight is 2999.77.

[0036] Example 2 This embodiment provides a crystal material with the chemical formula ( ). S -3AP)4Ge5I 18 The preparation steps are basically the same as in Example 1, except that the template agent added is ( S 0.636 g (4.0 mmol) of 3AP·2HCl was added, and the remaining reaction conditions were kept constant, eventually yielding yellow blocky crystals. The chemical formula of the obtained crystals is (C4H4PO4). 12 N2)4Ge5I 18 Its molecular weight is 2999.77.

[0037] Example 3 This embodiment provides a crystal material with the chemical formula ( ). rac -3AP)4Ge5I 18 The preparation steps are basically the same as in Example 1, except that the template agent added is... rac-3AP·2HCl 0.636 g (4.0 mmol), with other reaction conditions kept constant, finally yielded yellow blocky crystals. The chemical formula of the obtained crystals is (C4H 12 N2)4Ge5I 18 Its molecular weight is 2999.77.

[0038] Example 4 This embodiment provides a crystal material with the chemical formula (4APD)4Ge5I. 18 The preparation steps were basically the same as in Example 1, except that the template agent added was 0.692 g (4.0 mmol) of 4APD·2HCl, and the other reaction conditions remained unchanged, ultimately yielding yellow blocky crystals. The chemical formula of the obtained crystals is (C5H 14 N2)4Ge5I 18 Its molecular weight is 3055.87.

[0039] Single crystal photographs of the multinuclear iodine-germanium cluster crystal materials obtained in Examples 1-4 of this invention are shown below. Figure 1 As shown, Figure 1 In the middle, (a) is ( R -3AP)4Ge5I 18 (b) is ( S -3AP)4Ge5I 18 (c) is ( rac -3AP)4Ge5I 18 , (d) is (4APD)4Ge5I 18 .

[0040] The relevant properties of the crystal materials in Examples 1-4 were tested, as follows: (1) Single crystal structure determination Single-crystal X-ray diffraction tests were performed on the yellow blocky crystals obtained in Examples 1-4, respectively. The tests were conducted at 293 K, where ( R -3AP)4Ge5I 18 、( rac -3AP)4Ge5I 18 and (4APD)4Ge5I 18 Measurements were taken using a Rigaku Synergy Custom single-crystal diffractometer equipped with a HyPix detector, with Cu K as the radiation source. α ray( λ = 1.54184 Å); ( S -3AP)4Ge5I 18 Measurements were taken using a Bruker APEX-II CCD single-crystal diffractometer, with the radiation source being Mo K. α ray( λ= 0.71073 Å). After integration, absorption correction, structure solving, and refinement, the single-crystal structures of the four crystalline materials were obtained.

[0041] The results show that, R -3AP)4Ge5I 18 and( S -3AP)4Ge5I 18 They all crystallize in orthorhombic crystal systems I Space group 222; rac -3AP)4Ge5I 18 and (4APD)4Ge5I 18 They all crystallize in the tetragonal crystal system. I -42 m Space group. Further analysis shows that the [Ge5I] 18 ] 8- The cluster consists of a central Ge(II) atom and four terminal Ge(II) atoms. Each Ge atom is coordinated with surrounding I atoms to form an octahedral coordination environment. The central GeI6 octahedron and the four terminal GeI6 octahedrons are connected through face sharing, forming discrete five-nuclear zero-dimensional cluster units. There are no Ge-I covalent bonds between clusters. Organic amine cations fill the inter-cluster voids and interact with [Ge5I] through intermolecular interactions such as NH···I hydrogen bonds. 18 ] 8- Clusters combine to construct a non-centrosymmetric crystal structure. See the schematic diagram for the relevant structure. Figure 2 (a) is a schematic diagram of the crystal material structure of Example 1, and (b) is a schematic diagram of the crystal material structure of Example 3.

[0042] (2) Powder X-ray diffraction test Powder X-ray diffraction (PXRD) tests were performed on the crystalline materials obtained in Examples 1-4, and the results are as follows: Figure 3 As shown, Figure 3 In the middle, (a) is ( R -3AP)4Ge5I 18 (b) is ( S -3AP)4Ge5I 18 (c) is ( rac -3AP)4Ge5I 18 , (d) is (4APD)4Ge5I 18 The experimental PXRD patterns of each crystalline material sample are basically consistent with the simulated patterns calculated based on the single crystal structure, indicating that the obtained crystalline samples have good phase purity and no obvious impurity phases were observed.

[0043] (3) Optical bandgap test The crystal materials obtained in Examples 1-4 were subjected to ultraviolet-visible diffuse reflectance tests, and their optical band gaps were estimated using the Tauc plotting method. The results are as follows: Figure 4 As shown, Figure 4 In the middle, (a) is ( R -3AP)4Ge5I 18 (b) is ( S -3AP)4Ge5I 18 (c) is ( rac -3AP)4Ge5I 18 , (d) is (4APD)4Ge5I 18 .in,( R -3AP)4Ge5I 18 The optical band gap is approximately 2.78 eV; S -3AP)4Ge5I 18 The optical band gap is approximately 2.75 eV; rac -3AP)4Ge5I 18 The optical band gap is approximately 2.79 eV; (4APD)4Ge5I 18 The optical band gap is approximately 2.68 eV. These results indicate that the iodine-germanium cluster crystal material of this invention possesses a relatively stable and tunable optical band gap.

[0044] (4) Powder Second Harmonic Response Test The powder second harmonic response (SHG) of the crystalline materials obtained in Examples 1-4 was tested, using KH2PO4 (KDP) as the reference material. The second harmonic signals of each sample were recorded under the same test conditions, and the results are as follows. Figure 5 As shown in the figure. Test results indicate that all four compounds exhibit detectable second harmonic responses, with response intensities approximately 0.6–0.7 times that of KDP. This demonstrates that the iodine-germanium cluster crystal material described in this invention possesses certain nonlinear optical activity and has potential applications in frequency doubling and frequency conversion.

[0045] Crystallographic data of the crystalline materials of Examples 1 and 2 are shown in Table 1.

[0046] Table 1

[0047] Crystallographic data of the crystalline materials in Examples 3 and 4 are shown in Table 2.

[0048] Table 2

[0049] Any numerical value mentioned in this invention, if there is only a two-unit interval between any minimum and any maximum value, includes all values ​​that increase by one unit each time from the minimum to the maximum value. For example, if the amount of a component, or the value of a process variable such as temperature, pressure, or time, is stated as 50-90, in this specification it means specifically listing values ​​such as 51-89, 52-88… and 69-71 and 70-71, etc. For non-integer values, it may be appropriately considered that a unit is 0.1, 0.01, 0.001, or 0.0001. These are merely some specifically specified examples. In this application, in a similar manner, all possible combinations of numerical values ​​between the listed minimum and maximum values ​​are considered to have been disclosed.

[0050] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A class of organic-inorganic hybrid iodine-germanium cluster crystal materials, characterized in that, The general formula of the crystal material is (A)4Ge5I. 18 A is an organic amine cation, which is selected from polyamino-substituted C4-C5 saturated monocyclic nitrogen heterocyclic cations.

2. The crystal material according to claim 1, characterized in that, The organic amine cations include ( R )-3-aminopyrrolidine cation, ( S One of the following: 3-aminopyrrolidine cation, racemic 3-aminopyrrolidine cation, and 4-aminopiperidine cation; And / or, the crystal material has a non-centrosymmetric crystal structure.

3. The crystal material according to claim 1, characterized in that, The inorganic building blocks of the crystal material are discrete multinuclei [Ge5I] 18 ] 8- Cluster, the [Ge5I 18 ] 8- The cluster consists of a central divalent Ge atom and four terminal divalent Ge atoms. Each Ge atom coordinates with surrounding I atoms to form a distorted octahedral coordination configuration. The central GeI6 octahedron and the four terminal GeI6 octahedrons are connected through face sharing, forming a discrete five-nuclear zero-dimensional cluster unit. 18 ] 8- There is no Ge-I covalent bond between the clusters; the organic amine cation fills the inter-cluster voids and is linked to [Ge5I] via NH···I hydrogen bonds. 18 ] 8- Clusters interact to jointly construct non-centrosymmetric crystal structures.

4. The crystal material according to claim 2 or 3, characterized in that, The organic amine cation is ( R When the cation is 3-aminopyrrolidine, the cell parameters of the crystal material are: a = 11.9487(4) Å, b = 12.1379(5) Å, c =21.8680(7) Å, α = β = γ = 90°, V = 3171.6(2) Å 3 , Z = 2; The organic amine cation is ( S When the cation is 3-aminopyrrolidine, the cell parameters of the crystal material are: a =11.9707(4) Å, b = 12.1350(5) Å, c = 21.8997(7) Å, α = β = γ = 90°, V = 3181.2(2)Å 3 , Z = 2; When the organic amine cation is a racemic 3-aminopyrrolidine cation, the cell parameters of the crystal material are: a = b = 11.9651(2) Å, c = 21.8862(5) Å, α = β = γ = 90°, V = 3133.31(13) Å 3 , Z = 2; When the organic amine cation is a 4-aminopiperidine cation, the cell parameters of the crystal material are: a = b =12.1793(3) Å, c = 22.8357(12) Å, α = β = γ = 90°, V = 3387.3(3) Å 3 , Z = 2.

5. The crystal material according to claim 2 or 3, characterized in that, The organic amine cation is ( R )-3-aminopyrrolidine cation or ( S When the 3-aminopyrrolidine cation is present, the crystalline material crystallizes in an orthorhombic crystal system. I Space Group 222; When the organic amine cation is a racemic 3-aminopyrrolidine cation or a 4-aminopiperidine cation, the crystalline material crystallizes in the tetragonal crystal system. I -42 m Space group.

6. The crystal material according to claim 2 or 3, characterized in that, The organic amine cation is ( R When the cation is 3-aminopyrrolidine, the optical band gap of the crystal material is 2.78 eV; The organic amine cation is ( S When the cation is 3-aminopyrrolidine, the optical band gap of the crystal material is 2.75 eV; When the organic amine cation is a racemic 3-aminopyrrolidine cation, the optical band gap of the crystal material is 2.79 eV; When the organic amine cation is a 4-aminopiperidine cation, the optical band gap of the crystal material is 2.68 eV.

7. The crystal material according to any one of claims 1-3, characterized in that, The crystal material has a second harmonic response, and the response intensity of the crystal material is 0.6-0.7 times that of potassium dihydrogen phosphate.

8. A method for preparing the organic-inorganic hybrid iodine-germanium cluster crystal material according to any one of claims 1-7, characterized in that, include: After mixing HI aqueous solution and H3PO2 aqueous solution, GeO2 is added, and the mixture is heated and stirred at a first temperature to obtain a precursor solution. After adding organic amine dihydrochloride template agent to the precursor solution, it is kept at a second temperature, and after the heat preservation is completed, it is cooled to room temperature and allowed to stand.

9. The method according to claim 8, characterized in that, The molar ratio of HI in the HI aqueous solution to H3PO2 in the H3PO2 aqueous solution is (1-2):1; And / or, the mass concentration of the HI aqueous solution is 50-60%; And / or, the mass concentration of the H3PO2 aqueous solution is 45-55%; And / or, the first temperature is 110-130°C, and the heating and stirring time at the first temperature is 20-40 min; And / or, the organic amine dihydrochloride template agent includes ( R )-3-aminopyrrolidine dihydrochloride, ( S One of 3-aminopyrrolidine dihydrochloride, racemic 3-aminopyrrolidine dihydrochloride, and 4-aminopiperidine dihydrochloride; And / or, the molar ratio of GeO2 to the organic amine dihydrochloride template agent is (6-4):4; And / or, the second temperature is 80-100℃, and the temperature is maintained at the second temperature for 1.5-2.5h.

10. The application of the organic-inorganic hybrid iodine-germanium cluster crystal material according to any one of claims 1-7 or the organic-inorganic hybrid iodine-germanium cluster crystal material prepared by the method of claim 8 or 9 in laser frequency doubling devices, optical parametric oscillators, frequency conversion devices or second harmonic generation devices.

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