Low-temperature responsive organic molecular crystals, preparation thereof and use as energy materials

Abstract

The application belongs to the technical field of energy materials, and provides a low-temperature response organic molecular crystal, a preparation method thereof and application thereof as an energy material. 18 H 14 N2O)and compound 2 (C 18 H 12 N2O2)two kinds of cold braking flexible crystals, green (compound 1) and white (compound 2) needle-shaped crystals can be prepared by a liquid phase diffusion method, the fluorescence quantum efficiencies of the two are 0.62 and 0.67 respectively under 365nm ultraviolet light excitation, and the crystals can realize optical signal transmission as optical waveguide devices in straight state and curved state, and the optical loss is low. The crystal will have an instantaneous explosive transition at-120℃, with impact energy release, which can affect the surrounding environment, and the luminescent performance remains unchanged before and after the explosion, and the crystal can be used as an energy material at low temperature. The finding provides a new idea for the development of low-temperature propellant materials and the exploration of low-temperature energy conversion crystals, and has great application potential in the field related to low temperature.

Description

Technical Field

[0001] This invention belongs to the field of energy materials technology, and particularly relates to low-temperature responsive organic molecular crystals, their preparation, and their application as energy materials. Background Technology

[0002] Energy materials, as a core research subject in the field of energy science, play an irreplaceable role in defense, aerospace, propulsion systems, and special energy sources. In recent years, with the rapid development of high-energy chemistry, nanotechnology, and computational materials science, research on energy materials has shifted from the traditional formulation optimization stage to a new stage of molecular design and performance regulation, achieving a series of breakthroughs in this process.

[0003] In the field of energy materials research, thermodynamic crystals, as rare solid materials with unique intelligent functions, have attracted much attention due to their ability to sense and respond to external light, heat, or mechanical stimuli through rapid morphological changes. These materials exhibit significant dimensional changes and mechanical deformations when the temperature changes, including phenomena such as delamination, cracking, fracture, splitting, and even explosive fragmentation. As highly efficient thermal-to-kinetic energy converters, they show great application potential in ultrafast sensing, switching, and actuation. Their characteristic lies in the fact that when the temperature exceeds the phase transition point, a small but sudden change in crystal size occurs immediately, triggering fragmentation or jumping behavior. Combined with other unconventional phenomena such as shape memory effect, thermodynamic crystals become a typical representative of the dynamic properties of molecular solids. With their ability to switch structures in a single operation and strong mechanical effects, they have significant application value in fields such as intelligent temperature sensors, valves, and integrated optical devices.

[0004] Existing thermodynamic crystals have significant shortcomings: firstly, their response types are limited, with most thermodynamic crystals responding only to heat and lacking the ability to respond to cold; secondly, their response intensity is insufficient, resulting only in self-fragmentation and destruction, without impacting the surrounding environment. Therefore, this invention proposes a low-temperature responsive organic molecular crystal, its preparation, and its application as an energy material. Summary of the Invention

[0005] The purpose of this invention is to provide low-temperature responsive organic molecular crystals, their preparation, and their application as energy materials, thereby addressing the problems raised in the background art.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A low-temperature responsive organic molecular crystal, wherein the crystal is a crystal of compound 1 or compound 2, wherein the molecular formula of compound 1 is C1. 18 H 14 N₂O, its structural formula is shown in Formula I:

[0008] ;

[0009] The molecular formula of compound 2 is C 18 H 12 N2O2, its structural formula is shown in Formula II:

[0010] ;

[0011] The synthesis method of compound 1 is as follows: 1.42 g of 4-cyanophenylacetonitrile and 1.50 g of 4-ethoxybenzaldehyde were added to 40 mL of ethanol and stirred at 25 °C for 3 hours; the reaction mixture was filtered, the filter cake was dried and purified by column chromatography to obtain a green solid powder;

[0012] The synthesis method of compound 2 is as follows: 1.42 g of 4-cyanophenylacetonitrile and 1.64 g of methyl-4-formylbenzoate were added to 40 mL of ethanol and stirred at 25 °C for 3 hours; the reaction mixture was filtered, the filter cake was dried and purified by column chromatography to obtain a white solid powder.

[0013] Furthermore, the crystals exhibit luminescence properties under 365 nm ultraviolet light excitation, with fluorescence quantum efficiencies of 0.62 and 0.67 for compound 1 and compound 2, respectively, and maximum emission wavelengths corresponding to the main peaks of their emission spectra being 490 nm and 471 nm, respectively.

[0014] Furthermore, the crystals can function as optical waveguide materials in both straight and bent states; the optical losses of Compound 1 crystal and Compound 2 crystal in the straight state are 0.10 dB mm, respectively. -1 and 0.09 dB mm -1 The optical loss in the bent state is 0.11 dB mm. -1 and 0.15 dB mm -1 .

[0015] Furthermore, the crystal undergoes explosive fragmentation when the temperature drops to -120°C, releasing impact energy, and its luminescent properties remain unchanged before and after the explosion.

[0016] The preparation method of the low-temperature responsive organic molecular crystal described above includes the following steps:

[0017] Dissolve compound 1 or compound 2 in dichloromethane to prepare a saturated solution. Add 3 ml of the saturated solution to a test tube, and then slowly add 6 ml of anhydrous ethanol along the inner wall of the test tube to form a layered interface. Seal the mouth of the test tube and let it stand for 3-5 days to obtain needle-like crystals.

[0018] An energy material comprising the aforementioned low-temperature responsive organic molecular crystal, used to release energy through explosion in a low-temperature environment.

[0019] An optical waveguide device comprising the aforementioned low-temperature responsive organic molecular crystal, used for active or passive optical signal transmission.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] This invention successfully synthesized compound 1 (C 18 H 14 N2O) and compound 2 (C 18 H 12 Two small organic molecule crystals, N₂O₂ and N₂O₂, are cold-actuated flexible crystals. These crystals, green (compound 1) and white (compound 2), can be prepared as needle-like crystals via liquid-phase diffusion. Both crystals exhibit strong luminescence, with fluorescence quantum efficiencies of 0.62 and 0.67 respectively under 365 nm ultraviolet light excitation. They also possess good mechanical compliance, functioning as optical waveguides in both straight and bent states with low optical loss. Crucially, they exhibit unique dynamic behavior at low temperatures. Their structure is stable at room temperature and gradually cooled to -120°C. Upon reaching -120°C, they undergo a sudden explosive transformation, releasing shock energy that can impact the surrounding environment. Their luminescence properties remain unchanged before and after the explosion, making them suitable as energy materials for cryogenic applications. This groundbreaking discovery overturns traditional understanding of material stability, revealing the application potential of such dynamic molecular crystals in cryogenic explosion dynamics, flexible electronics, and optical devices. It provides new insights into the development of cryogenic propulsion materials based on solid-solid transitions and lays the foundation for exploring more potential cryogenic energy conversion crystals. Attached Figure Description

[0022] Figure 1 The proton NMR spectrum of compound 1 in DMSO-d6 ( 1 H NMR 400 MHz).

[0023] Figure 2 The carbon NMR spectrum of compound 1 in DMSO-d6 ( 13 C NMR 101 MHz).

[0024] Figure 3 The proton NMR spectrum of compound 2 in CHC3-d ( 1 H NMR 400 MHz).

[0025] Figure 4 Carbon NMR spectrum of compound 2 in CHC3-d ( 13 C NMR 101 MHz).

[0026] Figure 5This is a ball-and-stick model diagram of compound 1.

[0027] Figure 6 This is a ball-and-stick model diagram of compound 2.

[0028] Figure 7 The optical waveguide and optical loss of Compound 1 crystal in its straight and bent states were measured. Among them, a) is the excitation of Compound 1 crystal in its straight state at different positions by focusing a 365 nm laser; b) is the fluorescence spectrum of the top of the straight-state Compound 1 crystal at 298 K; c) is the optical loss of Compound 1 crystal in its straight state at 298 K; d) is the excitation of Compound 1 crystal in its bent state at different positions by focusing a 365 nm laser; e) is the fluorescence spectrum of the top of the bent-state Compound 1 crystal at 298 K; and f) is the optical loss of Compound 1 crystal in its bent state at 298 K.

[0029] Figure 8 The optical waveguides and optical losses of the compound 2 crystal in its straight and bent states were measured. Among them, a) is the excitation of the straight-state compound 2 crystal at different positions by focusing a 365 nm laser; b) is the fluorescence spectrum of the top of the straight-state compound 2 crystal at 298 K; c) is the optical loss of the compound 2 crystal in its straight state at 298 K; d) is the excitation of the bent-state compound 2 crystal at different positions by focusing a 365 nm laser; e) is the fluorescence spectrum of the top of the bent-state compound 2 crystal at 298 K; and f) is the optical loss of the compound 2 crystal in its bent state at 298 K.

[0030] Figure 9 The images show the low-temperature response and explosion process of Compound 1 crystal; where a is a schematic diagram of the explosion state change of Compound 1 crystal from room temperature (25℃) to -120℃; and b is a high-speed photographic sequence (0-7ms) of the explosion process of Compound 1 crystal.

[0031] Figure 10 The images show the low-temperature response and explosion process of the crystal of compound 2; where a is a schematic diagram of the explosion state change of the crystal of compound 2 from room temperature (25℃) to -120℃; and b is a high-speed photographic sequence (0-7ms) of the explosion process of the crystal of compound 2. Detailed Implementation

[0032] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0033] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0034] Example 1: Synthesis of Compound 1 and Compound 2;

[0035] The molecular formula of compound 1 is C18 H 14 N₂O, its structural formula is shown in Formula I:

[0036] ;

[0037] The synthesis method of compound 1 is as follows:

[0038] 4-Cyanophenylacetonitrile (1.42 g, 10 mmol) and 4-ethoxybenzaldehyde (1.50 g, 10 mmol) were added to 40 mL of ethanol and stirred at 25 °C for 3 hours. The reaction mixture was filtered, and the filter cake was dried and purified by column chromatography (silica gel:petroleum ether / dichloromethane = 1:4) to obtain a green solid powder C. 18 H 14 N2O. Its ball-and-stick model structure ( Figure 5 The molecular structure of the compound is consistent with that of compound 1, which proves that the crystals formed by this compound are very pure substances.

[0039] 1 H NMR (400 MHz, DMSO- d 6) δ 8.11 (s, 1H), 8.00 – 7.91 (m, 4H) 7.88 (d, J = 8.1, 2H), 7.12 – 7.05 (m, 2H), 4.11 (q, J = 6.9, 2H), 1.36 (t, J = 7.1,3H), such as Figure 1 As shown.

[0040] 13 C{ 1 H} NMR (101 MHz, DMSO- d 6) δ 161.60, 145.75, 145.66, 139.20, 139.16, 133.49, 133.45, 132.26, 126.63, 126.58, 126.12, 119.02, 118.34, 115.48, 115.43, 111.29, 105.57, 105.52, 64.04, 14.99. (For example...) Figure 2 As shown.

[0041] The molecular formula of compound 2 is C 18 H 12 N2O2, its structural formula is shown in Formula II:

[0042] ;

[0043] The synthesis method of compound 2 is as follows:

[0044] 1.42 g (10 mmol) of 4-cyanophenylacetonitrile and 1.64 g (10 mmol) of methyl-4-formylbenzoate were added to 40 mL of ethanol and stirred at 25 °C for 3 hours. The reaction mixture was filtered, and the filter cake was dried and purified by column chromatography (silica gel:petroleum ether / dichloromethane = 1:4) to give a white solid powder C. 18 H 12 N2O2. Its ball-and-stick model structure ( Figure 6 The molecular structure of compound 1 is consistent with that of compound 2, which proves that the crystals formed by this compound are very pure substances.

[0045] 1 H NMR (400 MHz, chloroform- d ) δ 8.15 (d, J = 8.2 Hz, 2H), 7.98 (d, J = 8.2 Hz, 2H), 7.82 (d, J = 8.3 Hz, 2H), 7.77 (d, J = 8.3 Hz, 2H), 7.67 (s,1H), 3.96 (s, 3H), like Figure 3 As shown.

[0046] 13 C{ 1 H} NMR (101 MHz, chloroform- d ) δ 166.11, 143.44, 138.28, 136.93, 132.97, 132.33, 130.29, 129.53, 126.78, 118.12, 116.78, 113.25, 112.25, 52.53. (For example...) Figure 4 As shown.

[0047] Example 2: Crystal growth;

[0048] Dissolve either compound 1 or compound 2 in dichloromethane to prepare a saturated solution. Add 3 ml of the saturated solution to a test tube using a dropper. Then, slowly add 6 ml of anhydrous ethanol along the inner wall of the test tube using a dropper, allowing the solution to separate into layers. Seal the test tube tightly with sealing film, allowing the compound molecules to diffuse and grow at the layering interface. Green (compound 1) / white (compound 2) needle-like crystals (0.5–5.0 cm in length) will be obtained in the test tube in approximately 3–5 days.

[0049] Example 3: Photophysical properties of crystals and applications in optical waveguides;

[0050] I. Crystallographic characterization of compound 1;

[0051] (1) Luminescence phenomenon and photophysical properties;

[0052] When the crystal of compound 1 was excited with 365 nm ultraviolet light, obvious luminescence was observed. Figure 7 (Among them, a and d exhibit elongated luminescent signals). Through spectral analysis ( Figure 7 The main peak of the emission spectrum (b and e) corresponds to a maximum emission wavelength of 490 nm. The fluorescence quantum efficiency was calculated to be 0.62, indicating that the crystal has good luminescence performance under ultraviolet excitation.

[0053] (2) Application verification of optical waveguides;

[0054] Straight-state waveguide: A straight-state compound 1 crystal, when excited by ultraviolet light, can transmit the excited light from one end to the other. Figure 7 (a) Intensity analysis of light at different transmission distances (0, 1, 2, 3, 4, 5 mm). Figure 7 (b and c) I tip / I body ( I tip For the light intensity at the end of the crystal, I body Using the bulk light intensity of the crystal as an indicator, the optical loss was fitted to be 0.10 dB / mm². -1 This proves that the straight state can efficiently guide light.

[0055] Bending waveguide: Bending state compound 1 crystal, under ultraviolet light excitation, can also transmit light from one end to the other. Figure 7 Similarly, the light intensity at different transmission distances (d) is analyzed. Figure 7 (e and f) I tip / I body Using this as the indicator, the fitted optical loss was found to be 0.11 dB mm. -1This proves that the bent state also has waveguide function.

[0056] II. Crystal characterization of Compound 2;

[0057] (1) Luminescence phenomenon and photophysical properties;

[0058] When the crystal of compound 2 was excited with 365 nm ultraviolet light, obvious luminescence was observed. Figure 8 (Among them, a and d exhibit elongated luminescent signals). Through spectral analysis ( Figure 8 The main peak of the emission spectrum (b and e) corresponds to a maximum emission wavelength of 471 nm. The fluorescence quantum efficiency was calculated to be 0.67, indicating that the crystal has good luminescence performance under ultraviolet excitation.

[0059] (2) Application verification of optical waveguides;

[0060] Straight-state waveguide: A straight-state compound 2 crystal, when excited by ultraviolet light, can transmit the excited light from one end to the other. Figure 8 (a) Intensity analysis of light at different transmission distances (0, 1, 2, 3, 4, 5 mm). Figure 8 (b and c) I tip / I body ( I tip For the light intensity at the end of the crystal, I body Using the bulk light intensity of the crystal as an indicator, the fitted optical loss was found to be 0.09 dB / mm². -1 This proves that the straight state can efficiently guide light.

[0061] Bending waveguide: Bending state compound 2 crystal, under ultraviolet light excitation, can also transmit light from one end to the other. Figure 8 Similarly, the light intensity at different transmission distances (d) is analyzed. Figure 8 (e and f) I tip / I body Using this as an indicator, the fitted optical loss was found to be 0.15 dB mm. -1 This proves that the bent state also has waveguide function.

[0062] In summary, both compounds exhibit good luminescence performance under 365 nm ultraviolet light excitation, and both their straight and bent states can be used as optical waveguide devices to achieve optical signal transmission.

[0063] Example 4: Low-temperature response and energy properties of crystals;

[0064] Compound 1 crystals remained intact at room temperature (25°C) without being destroyed during gradual cooling; however, when the temperature dropped to -120°C, the crystals of Compound 1 underwent a sudden and drastic change—rapidly shattering from needle-like fragments into an explosive dispersion. Figure 9 (a). High-speed photography (0-7 ms sequence images) shows ( Figure 9 In Figure b), the crystal is intact and needle-like at 0 ms (marked in red). It begins to emit light and fragment at 1 ms, and the fragmentation range expands from 3 to 5 ms. By 7 ms, the fragments are dispersed within the container, visually demonstrating the explosion process. The phenomena indicate that Compound 1 crystals possess the response characteristics of low-temperature triggered explosion: the structure is stable at room temperature and during gradual cooling (before reaching -120℃). Once the critical temperature of -120℃ is reached, it instantly undergoes explosive fragmentation, accompanied by the release of impact energy (the fragmentation morphology and dynamic diffusion observed in high-speed photography corroborate the energy output). Furthermore, comparing the luminescence phenomena before and after the explosion, both the initial excitation luminescence and the fragmentation after the explosion still emit light, indicating that the luminescence performance does not change with the explosion damage.

[0065] Compound 2 crystals are similar to Compound 1 crystals. Compound 2 crystals maintain their original shape at room temperature (25°C) and are not destroyed during gradual cooling; however, when the temperature drops to -120°C, Compound 2 crystals also undergo a sudden and violent explosion, shattering the entire crystal into very fine crystal fragments. Figure 10 (a). High-speed photography (0-7 ms sequence images) shows ( Figure 10 In (b), the crystal is a complete elongated strip at 0 ms (marked by the red box), begins to emit light and fragment at 1 ms, expands the fragmentation range from 3-5 ms, and disperses within the container at 7 ms, exhibiting a dynamic explosion process similar to that of Compound 1. The phenomena indicate that Compound 2 crystal also possesses the response characteristics of a low-temperature triggered explosion: stable at room temperature and during gradual cooling, it undergoes explosive fragmentation at -120℃, accompanied by the release of impact energy (the fragmentation morphology and dynamic diffusion observed in high-speed photography corroborate the energy output). Furthermore, the luminescent properties of the crystal remain unchanged before and after the explosion.

[0066] In summary, the crystals of the two compounds can be used as low-temperature responsive energy materials, releasing energy through explosion at -120℃, which can damage the surrounding environment while retaining luminescent properties.

[0067] Conclusion: The crystals of compounds 1 and 2 possess multiple properties and can be used as flexible light-emitting waveguide materials, suitable for active and passive optical transmission devices in both straight and bent states. Furthermore, both compounds' crystals explode at -120°C, a process accompanied by strong energy that can cause some damage to the surrounding environment. Before and after the explosion, both compounds' crystals maintain good light-emitting properties without any change during the process.

[0068] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.

Claims

1. A low-temperature responsive organic molecular crystal, characterized in that, The crystal is a crystal of compound 1 or compound 2, wherein the molecular formula of compound 1 is C1. 18 H 14 N₂O, its structural formula is shown in Formula I: ； The molecular formula of compound 2 is C 18 H 12 N2O2, its structural formula is shown in Formula II: ； The synthesis method of compound 1 is as follows: 1.42 g of 4-cyanophenylacetonitrile and 1.50 g of 4-ethoxybenzaldehyde were added to 40 mL of ethanol and stirred at 25 °C for 3 hours; the reaction mixture was filtered, the filter cake was dried and purified by column chromatography to obtain a green solid powder; The synthesis method of compound 2 is as follows: 1.42 g of 4-cyanophenylacetonitrile and 1.64 g of methyl-4-formylbenzoate were added to 40 mL of ethanol and stirred at 25 °C for 3 hours; the reaction mixture was filtered, the filter cake was dried and purified by column chromatography to obtain a white solid powder; The preparation method of the low-temperature responsive organic molecular crystal includes the following steps: Dissolve compound 1 or compound 2 in dichloromethane to prepare a saturated solution. Add 3 ml of the saturated solution to a test tube, and then slowly add 6 ml of anhydrous ethanol along the inner wall of the test tube to form a layered interface. Seal the mouth of the test tube and let it stand for 3-5 days to obtain needle-like crystals.

2. The low-temperature responsive organic molecular crystal according to claim 1, characterized in that, The crystals exhibit luminescence properties under 365 nm ultraviolet light excitation. The fluorescence quantum efficiencies of the crystals of compound 1 and compound 2 are 0.62 and 0.67, respectively, and the maximum emission wavelengths corresponding to the main peaks of their emission spectra are 490 nm and 471 nm, respectively.

3. The low-temperature responsive organic molecular crystal according to claim 1, characterized in that, The crystals can function as optical waveguide materials in both straight and bent states; the optical losses of Compound 1 crystal and Compound 2 crystal in the straight state are 0.10 dB mm, respectively. -1 and 0.09 dB mm -1 The optical loss in the bent state is 0.11 dB mm. -1 and 0.15 dB mm -1 .

4. The low-temperature responsive organic molecular crystal according to claim 1, characterized in that, The crystal explodes and shatters when the temperature drops to -120°C, releasing impact energy, and its luminescent properties remain unchanged before and after the explosion.

5. An energy material, characterized in that, The invention comprises the low-temperature responsive organic molecular crystal according to any one of claims 1-4, for releasing energy through explosion in a low-temperature environment.

6. An optical waveguide device, characterized in that, The low-temperature responsive organic molecular crystal according to any one of claims 1-4 is used for active or passive optical signal transmission.

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