A conjugated molecular nonlinear optical compound, its preparation method and applications

Abstract

The present invention discloses a conjugated molecular nonlinear optical compound, a preparation method thereof and an application thereof. The conjugated molecular nonlinear optical compound has a structural formula shown in the following formula I: wherein: each occurrence of the #imgabs0# independently represents an aromatic group having an electron-donating ability; each occurrence of the R independently represents an alkyl group; R1 is selected from hydrogen or #imgabs1#, where * represents the connection site. The pyrrolopyrrolidione-platinum(II) conjugated structure in the compound structure, due to its large conjugated structure and strong donor-acceptor interaction, enables the material to exhibit excellent intramolecular charge transfer absorption; the introduction of heavy metal atoms in its conjugated skeleton, and the spin-orbit coupling generated by the heavy atom effect cause the singlet excited state of the material to undergo intersystem crossing to form a triplet excited state, further enhancing the absorption of the excited state of the material, thereby obtaining high-performance nonlinear optical properties and realizing the application in laser limiting. #imgabs2#

Description

Technical Field

[0001] The present invention relates to the field of nonlinear optical materials. More specifically, it relates to a conjugated molecular nonlinear optical compound, a preparation method thereof, and an application thereof. Background Art

[0002] Since the birth of lasers, lasers have gradually been applied to various fields. At the same time, in order to cope with the blindness and damage caused by lasers to optical sensors and human eyes, the research and development of laser protection materials have received great attention. Among them, optical limiting materials based on nonlinear optical effects have the characteristics of "high resistance and low pass" for lasers, that is, at low-intensity lasers, the transmittance of the material to the laser does not change with the increase in laser intensity, showing linear transmittance, while at high-intensity lasers, the transmittance of the material to the laser decreases with the increase in the incident laser intensity, showing nonlinear transmittance. Therefore, optical limiting materials based on nonlinear optical effects can attenuate high-intensity lasers without affecting the information reception of optical sensors and human eyes, and then protect human eyes and sensitive optical instruments from laser damage. In recent years, the research on optical limiting materials based on nonlinear optical effects has attracted extensive attention.

[0003] The research on optical limiting materials began with inorganic crystals, and its nonlinear effect originated from resonance absorption and lattice distortion. It has the advantages of good stability, simple structure, easy processing, long service life, etc. However, due to its narrow protection band and low damage threshold, its protection effect is not good when dealing with wide-band tunable lasers. Organic optical limiting materials exhibit nonlinear polarization due to the delocalized π-electrons inside the material being affected by an externally applied photoelectric field. Compared with inorganic materials, organic materials can be designed at the molecular level according to requirements, and different from inorganic materials, they can generate nonlinear absorption in the non-resonant region. Among many promising materials, organic conjugated molecules represented by large π-electron conjugated systems such as fullerenes, porphyrins, phthalocyanines and their derivatives exhibit high optical limiting performance. And due to its easy modification and derivation of structure, easy regulation of performance, high nonlinear coefficient, fast response speed and other characteristics, it is considered to be a good candidate material with strong optical limiting response. Large π-electron conjugated systems, strong donor-acceptor interactions, and heavy metal atom effects are the main ways to improve the nonlinear optical properties of materials. However, there is little research on nonlinear optical materials that integrate the three effects in the same functional molecule and their structure-activity relationships, which limits the development and application of high-performance nonlinear optical materials. Summary of the Invention

[0004] Based on the above facts, the object of the present invention is to provide a conjugated molecular nonlinear optical compound, a preparation method thereof and an application thereof. In the structure of the nonlinear optical compound, by utilizing the structural characteristics of the platinum(II) benzimidazole derivative, it is connected with the pyrrolopyrrolidione derivative with strong electron-withdrawing properties through a carbon-carbon triple bond to form an organic conjugated molecule with a large π-electron conjugated system, strong intramolecular charge transfer absorption and the fusion of heavy metal atom effects. The pyrrolopyrrolidione-platinum(II) conjugated structure in this compound, due to its large conjugated structure and strong donor-acceptor interaction, enables the material to exhibit excellent intramolecular charge transfer absorption; the introduction of heavy metal atoms in its conjugated backbone, the spin-orbit coupling generated by the heavy atom effect enables the singlet excited state of the material to undergo intersystem crossing to form a triplet excited state, further enhancing the absorption of the material in the excited state, thereby obtaining high-performance nonlinear optical properties and realizing the application in laser limiting.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] On the one hand, the present invention provides a conjugated molecular nonlinear optical compound having the structural formula shown in Formula I as follows:

[0007]

[0008] Wherein:

[0009] Each occurrence of the independently represents an aromatic group having an electron-donating ability;

[0010] Each occurrence of the R independently represents an alkyl group;

[0011] The R 1 is selected from hydrogen or where * represents the connection site.

[0012] That is to say, the conjugated molecular nonlinear optical compound has the structural formula shown in Formula I-1 or I-2 as follows:

[0013]

[0014] Furthermore, the is selected from one of them, where * represents the connection site.

[0015] In the structure of the compound of the present invention, by constructing an electron donor-acceptor conjugate system and introducing heavy metal atoms, it can effectively promote the intramolecular charge transfer absorption. At the same time, due to the heavy metal atom effect, the singlet excited state is converted into a long-lived triplet excited state through intersystem crossing, generating effective triplet excited state absorption, and then a high-performance nonlinear optical material is obtained.

[0016] Further, the alkyl group is selected from a straight-chain alkyl group or a branched-chain alkyl group.

[0017] Further, the straight-chain alkyl group is selected from -C n H 2n+1 . Exemplary straight-chain alkyl groups include but are not limited to selected from -(CH 2 ) 5 CH 3 , -(CH 2 ) 6 CH 3 , -(CH 2 ) 7 CH 3 , -(CH 2 ) 9 CH 3 , -(CH 2 ) 10 CH 3 or -(CH 2 ) 11 CH 3 among others.

[0018] Further, the branched-chain alkyl group is selected from Exemplary branched-chain alkyl groups include but are not limited to selected from among others.

[0019] Wherein, x, n, and m each independently are selected from positive integers of 1 - 12.

[0020] In another aspect, the present invention provides a preparation method of the conjugate molecular nonlinear optical compound as described above, and this preparation method includes the following steps:

[0021] React the compound shown in formula II

[0022]

[0023] with K 2 PtCl 4 under acidic conditions to obtain the compound shown in formula III

[0024]

[0025] React the compound shown in formula III with the compound shown in formula IV-1 or IV-2

[0026]

[0027] Dissolve it in a solvent, and carry out a reflux reaction under a catalyst, alkaline conditions and an inert atmosphere, and separate and purify to obtain the conjugated molecular nonlinear optical compound;

[0028] Among them, the definitions of the above-mentioned R are as shown above respectively.

[0029] Furthermore, the compound shown in Formula II is prepared by a method including the following steps:

[0030] React isophthalic acid with o-phenylenediamine to obtain a benzimidazole derivative;

[0031] Then alkylate the benzimidazole derivative to obtain the compound shown in Formula II.

[0032] Furthermore, the temperature of the reaction between isophthalic acid and o-phenylenediamine is 220 - 240 °C, preferably 230 °C.

[0033] Furthermore, the temperature of the alkylation reaction is 90 - 110 °C, preferably 100 °C.

[0034] Furthermore, the molar ratio of isophthalic acid to o-phenylenediamine is 1:1 - 1:1.5.

[0035] Furthermore, when the 1 R is hydrogen, the synthesis route of the conjugated molecular nonlinear optical compound is as shown in the following formula:

[0036]

[0037] Furthermore, when the 1 R is , the synthesis route of the conjugated molecular nonlinear optical compound is as shown in the following formula:

[0038]

[0039] Furthermore, in the above synthesis route, the molar ratio of the compound shown in Formula II' to 1-bromobutane is 1:2 - 1:2.5.

[0040] Furthermore, the molar ratio of the compound shown in Formula II to K 2 PtCl 4 is 1:1 - 1:1.5.

[0041] Further, the molar ratio of the compound shown in Formula III to the compound shown in Formula IV-1 is 1:1 - 1:1.5; the molar ratio of the compound shown in Formula III to the compound shown in Formula IV-2 is 2:1 - 2.5:1.

[0042] Further, the catalyst is selected from cuprous iodide.

[0043] Further, the inert atmosphere is a nitrogen atmosphere.

[0044] Further, the basic condition includes triethylamine or diisopropylamine.

[0045] Further, the solvent is chloroform.

[0046] In another aspect, the present invention provides a nonlinear optical material prepared from the conjugated molecular nonlinear optical compound as described above.

[0047] In another aspect, the present invention provides an application of the nonlinear optical material as described above in laser limiting.

[0048] Further, in the above application, the laser used is a pulsed laser; the pulse width of the pulsed laser is 4 - 10 ns, the pulse frequency is 10 Hz, and the wavelength is 532 nm.

[0049] The beneficial effects of the present invention are as follows:

[0050] The conjugated molecular nonlinear optical compound provided in the present invention has nonlinear optical properties and can be used as a nonlinear optical material. In its structure, III and IV-1 or III and IV-2 are linked by a carbon-carbon triple bond, which not only has large conjugated π electrons, a strong donor-acceptor structure to promote intramolecular charge transfer, but also has a heavy metal atom effect. The three produce a synergistic effect, making the material have a large third-order nonlinear coefficient, excellent intramolecular charge transfer absorption and excited-state absorption, showing high nonlinear optical limiting performance and having an important application in laser protection. The preparation method of the conjugated molecular nonlinear optical compound provided in the present invention is simple, and the material structure is easy to modify. Description of the Drawings

[0051] The following further details the specific embodiments of the present invention with reference to the drawings.

[0052] Figure 1 Shows the NMR spectrum of the nonlinear optical material DPP-Th-Pt prepared in Example 1.

[0053] Figure 2 Shows the UV-Vis spectrum of the nonlinear optical material DPP-Th-Pt prepared in Example 1.

[0054] Figure 3 The non-linear optical property diagram of the non-linear optical material DPP-Th-Pt prepared in Example 2 is shown.

[0055] Figure 4 The NMR spectrum diagram of the non-linear optical material DPP-Th-2Pt prepared in Example 2 is shown.

[0056] Figure 5 The UV-Vis spectrum diagram of the non-linear optical material DPP-Th-2Pt prepared in Example 2 is shown. Detailed implementation manners

[0057] To illustrate the present invention more clearly, the present invention will be further described below in conjunction with preferred embodiments and the accompanying drawings. Similar components in the drawings are denoted by the same reference numerals. Those skilled in the art should understand that the content specifically described below is illustrative rather than restrictive, and should not be used to limit the protection scope of the present invention.

[0058] Example 1

[0059] The structural formula of the pyrrolo[3,4-c]pyrrole-2,5-dione-platinum(II) electron donor-acceptor type conjugated molecule non-linear optical material (conjugated molecule non-linear optical compound) DPP-Th-Pt in this example is as follows:

[0060]

[0061] The synthesis route of the pyrrolo[3,4-c]pyrrole-2,5-dione-platinum(II) electron donor-acceptor type conjugated molecule non-linear optical material DPP-Th-Pt is as follows:

[0062]

[0063] The synthesis of the pyrrolo[3,4-c]pyrrole-2,5-dione-platinum(II) electron donor-acceptor type conjugated molecule non-linear optical material DPP-Th-Pt is as follows:

[0064] Synthesis of Cl-Pt: The synthesis of this compound was carried out with reference to, but not limited to, the methods disclosed in the literature "Light-emitting tridentate cyclometalated platinum(II) complexes containing σ-alkynyl auxiliaries: tuning of photo- and electrophosphorescene, J. Am. Chem. Soc., 2004, 126, 4958" and "Design strategy for high-performance dendritic carbazole-containing alkynylplatinum(II) complexes and their application in solution-processable organic light-emitting devices, J. Am. Chem. Soc., 2016, 138, 6281".

[0065] Synthesis of DPP-Th-d-TMS: Dissolve DPP-Th-Br (0.94 g, 1 mmol) and trimethylsilylacetylene (0.29 g, 2.95 mmol) in 20 ml of tetrahydrofuran and place them in a two-necked flask. Under a nitrogen atmosphere, add bis(triphenylphosphine)palladium(II) chloride (0.07 g, 0.1 mmol) and copper(I) iodide (0.057 g, 0.3 mmol), and react at room temperature. After filtering through a short silica gel column to remove the solvent, precipitate with dichloromethane / methanol to obtain purple solid DPP-Th-TMS (0.95 g, yield 98%). Dissolve DPP-Th-TMS (0.92 g, 0.96 mmol) and potassium carbonate (0.40 g, 2.88 mmol) in a mixed solvent of 50 ml of tetrahydrofuran and 50 mL of ethanol and place them in a two-necked flask, and react at room temperature. After filtering through a short silica gel column to remove the solvent, precipitate with dichloromethane to obtain dark blue solid DPP-Th-d-TMS (0.35 g, yield 41%). 1 H NMR (400 MHz, CDCl 3 ): δ = 8.92 - 8.91 (1H, d), 8.78 - 8.77 (1H, d), 7.65 - 7.63 (1H, d), 7.38 - 7.37 (1H, d), 4.02 - 3.97 (4H, m), 3.57 (1H, s), 1.90 (2H, s), 1.28 - 1.21 (64H, m), 0.89 - 0.84 (12H, m).

[0066] Synthesis of DPP-Th-Pt: Under nitrogen protection, Cl-Pt (157 mg, 0.24 mmol), DPP-Th-d-TMS (212.5 mg, 0.24 mmol), and copper(I) iodide (5 mg, 0.026 mmol) were dissolved in 35 ml of chloroform and placed in a two-necked flask. The flask was purged with nitrogen three times, and then degassed diisopropylamine (1 ml) was added. The mixture was stirred overnight at room temperature. After removing the solvent, the solid was precipitated with dichloromethane / methanol, and then washed three times with water and methanol, and dried under vacuum to obtain a black solid DPP-Th-Pt (180 mg, yield 50%). The NMR spectrum is as shown in Figure 1 shown below. 1 1H NMR (400 MHz, CDCl 3 3): δ = 9.27 - 9.26 (1H, d), 8.83 - 8.82 (1H, dd), 8.74 - 8.72 (2H, d), 7.59 - 7.57 (1H, dd), 7.48 - 7.46 (2H, d), 7.37 - 7.32 (3H, m), 7.18 - 7.13 (3H, m), 4.53 - 4.49 (4H, t), 4.12 - 4.07 (4H, m), 1.94 - 1.86 (6H, m), 1.33 - 1.19 (64H, m), 0.99 - 0.95 (6H, t), 0.89 - 0.80 (12H, m). The UV-Vis spectrum is as shown in Figure 2 shown below. The compound exhibits broad absorption bands centered at 305 nm, 386 nm, 556 nm, and 591 nm.

[0067] Optical limiting performance of the pyrrolopyrrole dione-platinum(II) electron donor-acceptor type conjugated molecular nonlinear optical material DPP-Th-Pt: DPP-Th-Pt was dissolved in 1,1,2,2-tetrachloroethane, placed in a 1-mm quartz cuvette, and adjusted to have a linear transmittance of 70% at a wavelength of 532 nm. The nonlinear optical properties of the material were measured by Z-scan technology. The test laser was a Nd:YAG pulsed laser with a pulse width of 4 ns, a pulse frequency of 10 Hz, and a laser wavelength of 532 nm. The incident laser energy was 20 μJ. As shown in Figure 3 shown below, the material exhibits typical reverse saturable absorption nonlinear optical properties, and the normalized transmittance drops to 0.66. Therefore, the pyrrolopyrrole dione-platinum(II) electron donor-acceptor type conjugated molecular nonlinear optical material DPP-Th-Pt has a laser limiting effect and can be used for laser protection.

[0068] Example 2

[0069] The structural formula of the pyrrolopyrrole dione-platinum(II) electron donor-acceptor type conjugated molecular nonlinear optical material DPP-Th-2Pt in this example is as follows:

[0070]

[0071] The synthetic route of DPP-Th-2Pt is as follows:

[0072]

[0073] The synthesis of the DPP-Th-2Pt-based electron donor-acceptor type conjugated molecular nonlinear optical material is as follows:

[0074] Synthesis of Cl-Pt: The synthesis of this compound refers to but is not limited to the methods disclosed in the literature "Light-emitting tridentate cyclometalated platinum(II) complexes containing σ-alkynyl auxiliaries: tuning of photo- and electrophosphorescene, J. Am. Chem. Soc., 2004, 126, 4958" and "Design strategy for high-performance dendritic carbazole-containing alkynyl platinum(II) complexes and their application in solution-processable organic light-emitting devices, J. Am. Chem. Soc., 2016, 138, 6281".

[0075] Synthesis of DPP-Th-d-2TMS: Dissolve DPP-Th-2Br (0.54 g, 0.82 mmol) and trimethylsilylacetylene (0.32 g, 3.28 mmol) in 30 ml of tetrahydrofuran and place it in a two-necked flask. Under a nitrogen atmosphere, add bis(triphenylphosphine)palladium(II) chloride (0.11 g, 0.16 mmol) and copper(I) iodide (0.048 g, 0.25 mmol), and react at room temperature. After filtration through a short silica gel column to remove the solvent, precipitate with dichloromethane / methanol to obtain purple solid DPP-Th-2TMS (0.48 g, yield 78%). Dissolve DPP-Th-2TMS (0.66 g, 0.63 mmol) and potassium carbonate (0.26 g, 1.89 mmol) in a mixed solvent of 40 ml of tetrahydrofuran and 40 mL of ethanol and place it in a two-necked flask, and react at room temperature. After filtration through a short silica gel column to remove the solvent, precipitate with dichloromethane / methanol to obtain blue solid DPP-Th-d-2TMS (0.67 g, yield 84%).1 HNMR(400MHz,CDCl 3 ): δ = 8.82 - 8.81(2H, d), 7.38 - 7.37(2H, d), 3.98 - 3.96(4H, d), 3.58(2H, s), 1.90(2H, s), 1.29 - 1.21(64H, m), 0.89 - 0.84(12H, m).

[0076] Synthesis of DPP-Th-2Pt: Under nitrogen protection, Cl-Pt (157 mg, 0.24 mmol), DPP-Th-d-2TMS (110 mg, 0.12 mmol), and copper(I) iodide (5 mg, 0.026 mmol) were dissolved in 35 ml of chloroform and placed in a two-necked flask. The flask was purged with nitrogen three times, and then degassed triethylamine (1 ml) was added. The mixture was stirred overnight at room temperature. After removing the solvent, the solid was precipitated with dichloromethane / methanol, and then washed with water and methanol three times. The solid was dried under vacuum to obtain black solid DPP-Th-2Pt (100 mg, yield 39%). The NMR spectrum is as Figure 4 shown. 1 H NMR(400MHz,CDCl 3 ): δ = 9.23 - 9.22(2H, d), 8.81 - 8.79(4H, d), 7.52 - 7.51(4H, d), 7.41 - 7.37(4H, t), 7.34 - 7.28(6H, m), 7.22 - 7.17(6H, m), 4.56 - 4.53(8H, t), 4.19 - 4.17(4H, d), 2.02 - 2.00(2H, d), 1.95 - 1.91(8H, t), 1.47 - 1.21(64H, m), 1.01 - 0.97(12H, t), 0.85 - 0.82(12H, m). The UV-visible spectrum is as Figure 5 shown, and the compound exhibits broad absorption bands centered at 307 nm, 383 nm, 587 nm, and 636 nm.

[0077] Optical limiting performance of the diketopyrrolopyrrole-platinum(II) electron donor-acceptor type conjugated molecular nonlinear optical material DPP-Th-2Pt: Dissolve DPP-Th-2Pt in 1,1,2,2-tetrachloroethane, place it in a 1-mm quartz cuvette, and adjust its linear transmittance at a wavelength of 532 nm to 70%. Test the nonlinear optical properties of the material by the Z-scan technique. The test laser is a Nd:YAG pulsed laser with a pulse width of 4 ns, a pulse frequency of 10 Hz, and a laser wavelength of 532 nm. The incident laser energy is 20 μJ. This material has reverse saturation absorption nonlinear optical properties similar to those of Example 1, and the normalized transmittance drops to 0.57. Therefore, the diketopyrrolopyrrole-platinum(II) electron donor-acceptor type conjugated molecular nonlinear optical material DPP-Th-2Pt has a laser limiting effect and can be used for laser protection.

[0078] Example 3

[0079] The structural formula of the diketopyrrolopyrrole-platinum(II) electron donor-acceptor type conjugated molecular nonlinear optical material DPP-Ph-Pt in this example is as follows:

[0080]

[0081] The synthesis route of the diketopyrrolopyrrole-platinum(II) electron donor-acceptor type conjugated molecular nonlinear optical material DPP-Ph-Pt is similar to that of Example 1, except that and in the diketopyrrolopyrrole structure in the synthesis route are both replaced by and The specific synthesis route is as follows:

[0082]

[0083] The nuclear magnetic resonance spectrum and ultraviolet-visible spectrum of the compound are similar to those of Example 1.

[0084] Optical limiting performance of the dithieno[3,2-b:2′,3′-d]pyrrole-diaminoplatinum(II) electron donor-acceptor type conjugated molecular nonlinear optical material DPP-Ph-Pt: Dissolve DPP-Ph-Pt in 1,1,2,2-tetrachloroethane, place it in a 1-mm quartz cuvette, and adjust its linear transmittance at a wavelength of 532 nm to 70%. Test the nonlinear optical properties of the material by Z-scan technique. The test laser is a Nd:YAG pulsed laser with a pulse width of 4 ns, a pulse frequency of 10 Hz, and a laser wavelength of 532 nm. The laser incident energy is 20 μJ. This material has reverse saturable absorption nonlinear optical properties similar to those of Example 1, and the normalized transmittance drops to 0.73. Therefore, the dithieno[3,2-b:2′,3′-d]pyrrole-diaminoplatinum(II) electron donor-acceptor type conjugated molecular nonlinear optical material DPP-Ph-Pt has a laser limiting effect and can be used for laser protection.

[0085] Example 4

[0086] The structural formula of the dithieno[3,2-b:2′,3′-d]pyrrole-diaminoplatinum(II) electron donor-acceptor type conjugated molecular nonlinear optical material DPP-Ph-2Pt in this example is as follows:

[0087]

[0088] The synthesis route of the dithieno[3,2-b:2′,3′-d]pyrrole-diaminoplatinum(II) electron donor-acceptor type conjugated molecular nonlinear optical material DPP-Ph-2Pt is similar to that of Example 1, except that and in the dithieno[3,2-b:2′,3′-d]pyrrole structure in the synthesis route is replaced by The specific synthesis route is as follows:

[0089]

[0090] The nuclear magnetic resonance spectrum and ultraviolet-visible spectrum of the compound are similar to those of Example 2.

[0091] Optical limiting performance of the dithieno[3,2-b:2′,3′-d]pyrrole-diaminoplatinum(II) electron donor-acceptor type conjugated molecular nonlinear optical material DPP-Ph-2Pt: Dissolve DPP-Ph-2Pt in 1,1,2,2-tetrachloroethane, place it in a 1-mm quartz cuvette, and adjust its linear transmittance at a wavelength of 532 nm to 70%. Test the nonlinear optical properties of the material by Z-scan technique. The test laser is a Nd:YAG pulsed laser with a pulse width of 4 ns, a pulse frequency of 10 Hz, and a laser wavelength of 532 nm. The laser incident energy is 20 μJ. This material has reverse saturable absorption nonlinear optical properties similar to those of Example 1, and the normalized transmittance drops to 0.68. Therefore, the dithieno[3,2-b:2′,3′-d]pyrrole-diaminoplatinum(II) electron donor-acceptor type conjugated molecular nonlinear optical material DPP-Ph-2Pt has a laser limiting effect and can be used for laser protection.

[0092] Comparative Example 1

[0093] The structural formula of DPP-Th-Ph in this comparative example is as follows:

[0094]

[0095] The synthesis route of the said DPP-Th-Ph is as follows:

[0096]

[0097] The nonlinear optical properties of the said DPP-Th-Ph: Dissolve DPP-Th-Ph in 1,1,2,2-tetrachloroethane, place it in a 1-mm quartz cuvette, and adjust its linear transmittance at a wavelength of 532 nm to 70%. Test the nonlinear optical properties of the material by Z-scan technology. The test laser is a Nd:YAG pulsed laser, with a pulse width of 4 ns, a pulse frequency of 10 Hz, a laser wavelength of 532 nm, and a laser incident energy of 20 μJ. This material has reverse saturable absorption nonlinear optical properties similar to those of Example 1, and the normalized transmittance drops to 0.81. Compared with the example, this compound has weak nonlinear optical properties.

[0098] Comparative Example 2

[0099] The structural formula of DPP-Th-2Ph in this comparative example is as follows:

[0100]

[0101] The synthesis route of the said DPP-Th-2Ph is as follows:

[0102]

[0103] The nonlinear optical properties of the said DPP-Th-2Ph: Dissolve DPP-Th-2Ph in 1,1,2,2-tetrachloroethane, place it in a 1-mm quartz cuvette, and adjust its linear transmittance at a wavelength of 532 nm to 70%. Test the nonlinear optical properties of the material by Z-scan technology. The test laser is a Nd:YAG pulsed laser, with a pulse width of 4 ns, a pulse frequency of 10 Hz, a laser wavelength of 532 nm, and a laser incident energy of 20 μJ. This material has reverse saturable absorption nonlinear optical properties similar to those of Example 1, and the normalized transmittance drops to 0.75. Compared with the example, this compound has weak nonlinear optical properties.

[0104] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, based on the above description, other different forms of changes or modifications can be made. It is impossible to enumerate all the implementation manners here. Any obvious changes or modifications derived from the technical solutions of the present invention still fall within the protection scope of the present invention.

Claims

1. A conjugated molecular nonlinear optical compound, characterized in that, it has a structural formula shown in the following formula I: I； Wherein: The R 1 is selected from hydrogen or , where * represents the linking site; The said selected from or , where * represents the linking site; Each occurrence of R independently represents ; wherein, the x, n, and m each independently selected from positive integers of 1-12.

2. The preparation method of the conjugated molecular nonlinear optical compound according to claim 1, characterized in that, comprises the following steps: Dissolve the compound shown in formula II II With K 2 PtCl 4 React under acidic conditions to obtain the compound shown in Formula III III; Dissolve the compound shown in formula III and the compound shown in formula IV-1 or IV-2 IV-1 IV-2 in a solvent, and carry out a reflux reaction under a catalyst, alkaline conditions, and an inert atmosphere, and separate and purify to obtain the conjugated molecular nonlinear optical compound; Among them, the , and the definition of R is as shown in claim 1 respectively.

3. According to the preparation method described in claim 2, characterized in that, the compound shown in formula II is prepared by a method comprising the following steps: React isophthalic acid and o-phenylenediamine to obtain a benzimidazole derivative; Then alkylate the benzimidazole derivative to obtain the compound shown in formula II.

4. According to the preparation method described in claim 3, characterized in that, the reaction temperature between isophthalic acid and o-phenylenediamine is 220-240 °C; the reaction temperature of the alkylation reaction is 90-110 °C.

5. According to the preparation method described in claim 3, characterized in that, the reaction temperature between isophthalic acid and o-phenylenediamine is 230 °C.

6. According to the preparation method described in claim 3, characterized in that, the reaction temperature of the alkylation reaction is 100 °C.

7. According to the preparation method described in claim 2, characterized in that, the catalyst is selected from cuprous iodide; and / or the inert atmosphere is a nitrogen atmosphere; and / or the alkaline conditions include triethylamine or diisopropylamine; and / or the solvent is chloroform.

8. A nonlinear optical material, characterized in that, it is prepared from the conjugated molecular nonlinear optical compound according to claim 1.

9. The application of the nonlinear optical material according to claim 8 in laser limiting.

10. According to the application described in claim 9, characterized in that, in the application, the laser used is a pulsed laser; the pulse width of the pulsed laser is 4-10 ns, the pulse frequency is 10 Hz, and the wavelength is 532 nm.

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