English

• 0.   Introduction

  Phase transition materials usually have high latent heat and can absorb or release a large amount of heat energy during the phase transition process. The phase transition materials have the advantages of small volume change, good energy-saving effect, and easily controlled, and can be widely used in new energy and energy storage fields^[1-8]. For phase transition materials, besides the traditional inorganic materials, organic-inorganic hybrid materials have attracted more and more attention from researchers due to their significant structural variability and high tunability^[9-12].

  From a view of the application prospect, the aboveroom-temperature phase transition materials are more important due to the high phase transition temperature providing a wide operational temperature range and high stability for the production as key components in a variety of areas^[13-15]. At present, effective methods for the improvement of phase transition temperature have been extensively researched^[16-18]. On the one hand, the introduction of the deuterium effect or fluorine effect can greatly improve the phase transition temperature^[19-24]. On the other hand, reducing molecular symmetry by chemical substitution of organic templates can also achieve the purposes^[25-29]. However, the chemical modification method often requires us to deeply understand the relationship between structure and property.

  In the past few decades, several popular molecules with high phase transition points and other reversible physical properties have been successfully obtained using chemical modification^[30-35]. For example, in 2020, Fu et al. designed two enantiomeric phase transition molecules, [R-2-Me-H₂dabco][TFSA]₂ and [S-2-Me-H₂dabco][TFSA]₂ (Dabco=1, 4-diazabicyclo[2.2.2] octane), by introducing a methyl group on the Dabco molecule^[36]. The obtained two enantiomers showed phase transition temperatures at 405.8 and 415.8 K, higher than other hybrids based on Dabco itself. The key to success is that by introducing methyl into the spherical molecule Dabco can reduce the symmetry of the target molecule and finally lead to high-temperature phase transition materials.

  On this basis, we envisioned adding methyl groups into the cyclic molecule 1, 4, 7, 10-tetraazacy-clododecane (cyclen) because cyclen has a crown etherlike ring structure and the four nitrogen atoms on the same side could be protonated. As shown in Scheme 1, the reactions of cyclen with methyl iodide produced an unsymmetric molecule Me-cyclen. Further treatment of cyclen and Me-cyclen with two equivalents of HReO₄ gave the corresponding compounds (cyclen) (ReO₄)₂ (1) and (Me-cyclen) (ReO₄) ₂ (2) with high yields. Differential scanning calorimetry (DSC) measurement showed the phase transition temperatures of compounds 1 and 2 were at 324 and 384 K, respectively. Herein we report the synthesis, characterization, and phase transition of compounds 1 and 2.

  Scheme 1

  

  Scheme 1.  Molecular structures of cyclen and Me-cyclen

  下载: 全尺寸图片 幻灯片

  1.   Experimental

  1.1   Instruments and materials

  Me-cyclen was prepared according to the literature^[37]. Cyclen (98%) and perrhenic acid (75% in H₂O) were purchased from the Aladdin company and used without further purification. FT-IR spectra were recorded using KBr pellets in a range of 4 000-400 cm^-1 on an ALPHA spectrometer. Powder X -ray diffraction (PXRD) analysis was performed using a D8 ADVANCE diffractometer (Cu Kα graphite, λ =0.154 06 nm) operated at 40 kV and 15 mA with a Kβ foil filter, collecting data in a 2θ range of 5°-52° with a step size of 0.02°. NETZSCH DSC 200 F3 instrument was used to perform DSC measurement at a heating/cooling rate of 10 K·min^-1. The temperature-dependent dielectric constant of the crystal powder sample was measured on the Tonghui TH2828 analyzer at the frequency of 1 MHz.

  1.2   Synthesis

  1.2.1   Synthesis of compound 1

  To a solution of cyclen (0.17 g, 1.0 mmol) in 5 mL distilled water, perrhenic acid (0.72 g, 2.0 mmol, 75%) in 5 mL distilled water was added, and the mixture was stirred at room temperature (298 K) to give a clear solution. The colorless block crystals of 1 were finally obtained by evaporating the solution at room temperature for two days. Yield: 0.53 g (59%). Anal. Calcd. for C₈H ₂₂N₄O₈Re₂(%): C 14.24, H 3.26, N 8.31; Found(%): C 14.44, H 3.36, N 8.67. IR (KBr, cm^-1): 3 893(m), 3 736(w), 3 427(w), 3 305(s), 3 097(s), 2 914(s), 2 863 (s), 2 631(m), 2 358(m), 2 121(m), 1 863(m), 1 712(m), 1 575(s), 1 445(s), 1 267(m), 1 088(m), 911(vs), 755(s), 521(m).

  1.2.2   Synthesis of compound 2

  Me-cyclen (0.37 g, 2.0 mmol) in 10 mL distilled water and HReO₄ (1.68 g, 4.0 mmol, 75%) in 5 mL distilled water were mixed and the obtained solution was being stirred at room temperature (298 K) for 15 min. The white columnar crystals of 2 were isolated by slowly evaporating the solvent at room temperature for two days. Yield: 0.85 g (62%). Anal. Calcd. for C₉H ₂₄N₄O₈Re₂(%): C 15.70, H 3.51, N 8.14; Found(%): C 15.85, H 3.41, N 8.48. IR (KBr, cm^-1): 3 317(m), 3 067(m), 2 837(m), 2 177(w), 1 872(w), 1 561(w), 1 445 (m), 1 390(m), 1 261(m), 1 193(w), 1 126(m), 1 016(m), 963(w), 902(vs), 867(vs), 826(s), 759(s).

  1.3   X⁃ray crystallography

  The single-crystal diffraction data of 1 and 2 were collected by Mo Kα radiation (λ=0.071 073 nm) using a Rigaku Saturn 924 diffractometer at room temperature. Empirical absorption correction was applied when the data processing was performed using the Crystalclear software package. The structures were solved by direct methods and refined with a full-matrix leastsquares technique (Olex2)^[38-40]. All nonhydrogen atoms were refined anisotropically, and the positions of all hydrogen atoms were generated geometrically. Crystallographic data and structure refinements are listed in Table 1.

  Table 1

  

  Table 1.  Crystallographic data for compounds 1 and 2

  下载: 导出CSV

  Parameter	1	2
  Formula	C8H22N4O8Re2	C9H24N4O8Re2
  Formula weight	674.72	688.74
  Crystal system	Triclinic	Monoclinic
  Space group	P1	P21/n
  a/nm	0.868 12(2)	0.866 45(7)
  b/nm	0.961 38(3)	1.647 32(9)
  c/nm	1.190 09(3)	1.282 35(8)
  α/(°)	82.214(2)
  β/(°)	70.818(2)	92.272(6)
  γ/(°)	63.287(2)
  V/nm3	0.837 89(4)	1.828 9(2)
  Z	2	4
  Dc/(g·cm-3)	2.674	2.501
  F(000)	624	1280
  θmax	25	24.99
  μ(Mo Kα)/mm-1	14.475	13.266
  Total reflection	8 244	13 102
  Unique reflection	2 953 (Rint=0.064 9)	3 221 (Rint=0.041 8)
  Number of variables	200	209
  R1, wR2 [I > 2σ(I)]	0.051 1, 0.138 8	0.036 3, 0.082 9
  R1, wR2 (all data)	0.055 0, 0.142 0	0.050 0, 0.088 3
  GOF	1.093	1.032

  2.   Results and discussion

  2.1   Synthesis and characterization

  Compounds 1 and 2 are prepared according to the strict stoichiometry of cyclic amine with perrhenic acid of 1∶2. Excess or less perrhenic acid is easy to give impure products. The crystals of 1 and 2 with high purity were obtained by evaporating solvent at room temperature (298 K) and then washed with petroleum ether. The purity of compounds 1 and 2 was verified by PXRD, microanalysis, and IR. As shown in Fig. S1 (Supporting information), it can be seen that the experimentally measured PXRD data of 1 and 2 were completely consistent with the simulated data obtained by their single-crystal X-ray diffraction, confirming the bulk phase purity. Besides, it can be seen from the IR spectra (Fig.S2) that the absorptive peaks at 3 097 and 3 305 cm^-1 belong to the N—H bonds stretching vibration, the absorption at 1 445 cm^-1 belongs to the C—N bonds stretching vibration, the absorption peaks at 2 914 and 2 863 cm^-1 belong to the C—H stretching vibration of methylene and methyl groups, and the absorptions near 911 and 755 cm^-1 are ascribed to the characteristic absorption peaks of ReO₄^{- [41-43]}.

  2.2   Phase transition

  The DSC test can be used to determine whether the compound has a reversible phase transition during the heating and cooling processes^[44-45]. As shown in Fig. 1, compounds 1 and 2 both exhibited a pair of reversible endothermic and exothermic peaks. Compound 1 had an endothermic peak at 324 K and a corresponding exothermic peak at 313 K; compound 2 had an endothermic peak at 384 K and a corresponding exothermic peak at 361 K. It can be seen that the chemical modification of cyclen with one methyl group on nitrogen atom could greatly increase the phase transition temperature of 60 K. This may be an effective way to improve the phase transition temperature of organic-inorganic hybrid compounds.

  Figure 1

  

  Figure 1.  DSC curves of 1 (red) and 2 (blue) in heating and cooling runs

  下载: 全尺寸图片 幻灯片

  As shown in Table 2, to further study the thermal abnormal behavior of compounds 1 and 2, we have calculated the transformation enthalpy (H) and entropy (S) change of the corresponding compounds. According to the Boltzmann equation ΔS =Rln N (R is the molar gas constant, N is the ratio of the number of possible orientations of the entire disordered system), the N values of compounds 1 and 2 could be calculated to be 15.79 and 53.45, respectively. Generally speaking, the larger the N value of a substance is, the more serious order and disorder phase transition occurred in the substance^[46-47]. So, compound 2 proceeded a more serious order and disorder characteristics than compound 1 during the phase transition.

  Table 2

  

  Table 2.  Thermal values in the phase transition of 1 and 2

  下载: 导出CSV

  Compound	Tp, endoa/K	Tp, exob/K	ΔTc/K	ΔH/(kJ·mol-1)	ΔS/(J·mol-1·K-1)	N
  1	324	313	11	7.43	22.94	15.79
  2	384	361	23	12.70	33.08	53.45
  a Tp, endo is the temperature at the endothermic peak; b Tp, exo is the temperature at the exothermic peak; cΔT=Tp, endo-Tp, exo.

  2.3   Dielectric properties

  Dielectric measurement is a simple and effective method for finding new phase transition materials by studying the dynamic behavior of polar molecules in these structures. The dielectric constant is generally closely related to the molecular structure of compounds themselves^[48-50]. It can be seen from Fig. 2 that compounds 1 and 2 exhibited dielectric anomalies near the phase transition points, which were consistent with the thermal anomaly curves of DSC on heating and cooling. The dielectric anomaly of compound 1 was more obvious than that of compound 2. During the heating process, the real part of the dielectric constant of compound 1 gradually increased with the increase of temperature. When the temperature was close to 311 K, the dielectric constant showed a significant increase, and the value of ε' at 1 MHz gradually increased from 5.36 at 289 K to a maximum of 23.72 near the phase transition. Compared with 1, the ε' value of 2 at 1 MHz increased by about 0.35 times from 335 K to the phase transition point, which is much lower than the 3.4-fold increase of ε' value of 1 at 1 MHz. During the cooling process, dielectric anomalies were also found in compounds 1 and 2 near the phase transition temperatures, which further indicates both compounds have undergone a reversible dielectric transition behavior.

  Figure 2

  

  Figure 2.  Temperature dependence of the real parts (ε') of 1 and 2 at 1 MHz upon heating and cooling

  下载: 全尺寸图片 幻灯片

  2.4   Crystal structure analysis

  At room temperature, compound 1 crystallizes in the triclinic system, the space group is P1, and the asymmetric unit of compound 1 is composed of one (cyclen)⁺ cation and two perrhenate anions. While compound 2 crystallizes in the monoclinic system with the centrosymmetric P2 ₁/n space group, the asymmetric unit is composed of one (Me-cyclen)⁺ cation and two perrhenate anions. In both structures, two hydrogen atoms from perchloric acid have transferred to the nitrogen of cyclen or Me-cyclen. But due to the protonated hydrogen atoms being in a free state, two secondary nitrogen atoms in compounds 1 and 2 were randomly added with hydrogen atoms by the theoretical calculations.

  As shown in Fig. 3, in both structures, the perrhenic anions ReO₄^- are located outside the cyclen ring and interlinked with cations by the classic intermolecular hydrogen bonds (N—H···O). The distances between the donor N atoms and acceptor O atoms are in a range of 0.296 9-0.323 1 nm for 1 and 0.287 4-0.314 7 nm for 2 (Table S1 and S2). Besides the intermolecular hydrogen bonds, there are four intramolecular hydrogen bonds (N—H···N) that can be found in compounds 1 and 2. The distances between the donor N atoms and the acceptor N atoms are in a range of 0.279 7-0.290 1 nm for 1 and 0.281 9-0.294 4 nm for 2. To be noted, the four intramolecular hydrogen bonds force the nitrogen atoms in the cyclen ligand to be located on the same side of the ring (Table S1 and S2). As shown in Table S3 and S4, the bond angles in the cyclen and Me-cyclen rings are as large as possible, which may reduce the tension of the macrocycle to make the ring not fold and keep all atoms in one plane as can as possible. The average bond lengths of C—N in 1 (0.147 7 nm) are longer than those in 2 (0.146 8 nm), but the average bond lengths of C—C in 1 (0.150 7 nm) are shorter than those in 2 (0.152 7 nm). In both crystals, the Re—O bond lengths are about 0.171 0 nm, and the O—Re—O bond angles are near 109° 28x, indicating the ReO₄^- anions choose a slightly irregular tetrahedral structure.

  Figure 3

  

  Figure 3.  Crystal structures of 1 (a) and 2 (b) at room temperature, where the dashed lines represent the hydrogen bonds

  下载: 全尺寸图片 幻灯片

  3.   Conclusions

  In summary, adding a methyl group on the nitrogen atom of cyclen gave a low symmetric ligand Me-cyclen. Reactions of the twelve membered cyclic amine cyclen and Me-cyclen with two equivalents of perrhenic acid in an aqueous solution led to two-phase transition materials (cyclen)(ReO₄)₂ (1) and (Me-cyclen)(ReO₄)₂ (2). The IR, element analysis, and PXRD were carried out to prove their good purity. The DSC and dielectric measures showed the phase transition temperature of 2 at 384 K was much higher than that of compound 1 at 324 K. The analysis of the single-crystal structure reveals that the increase of the phase transition point in 2 is caused by the lower symmetric structure of Mecyclen because the introduction of a methyl group on cyclen increases the internal steric hindrance of a new molecule. This discovery reveals that chemical modification is an effective way to improve the phase transition temperature.

  Supporting information is available at http://www.wjhxxb.cn

  
  Acknowledgments: We thank the National Natural Science Foundation of China (Grants No. 21865015, 22071094, 22075123) for financial support.
• 1. [1]

     Li W D, Ding E Y. Preparation and Characterization of a Novel SolidLiquid PCM: Butanediol Di-Stearate[J]. Mater. Lett., 2007, 61(7):  1526-1528. doi: 10.1016/j.matlet.2006.07.072

  2. [2]

     Su C Y, Lun M M, Chen Y D, Zhou Y C, Zhang Z X, Chen M, Huang P Z, Fu D W, Zhang Y. Hybrid Optical-Electrical Perovskite Can be a Ferroelastic Semiconductor[J]. CCS Chem., 2022, 4(6):  2009-2019. doi: 10.31635/ccschem.021.202101073

  3. [3]

     Wei Z H, Jiang Z T, Zhang X X, Li M L, Tang Y Y, Chen X G, Cai H, Xiong R G. Rational Design of Ceramic-like Molecular Ferroelectric by Quasi-spherical Theory[J]. J. Am. Chem. Soc., 2020, 142:  1995-2000. doi: 10.1021/jacs.9b11665

  4. [4]

     Sha T T, Xiong Y A, Pan Q, Chen X G, Song X J, Yao J, Miao S R, Jing Z Y, Feng Z J, You Y M. Fluorinated 2D Lead Iodide Perovskite Ferroelectrics[J]. Adv. Mater., 2019, 31:  1901843.

  5. [5]

     Wang C H, Lin T, Li N, Zheng H P. Heat Transfer Enhancement of Phase Change Composite Material: Copper Foam/Paraffin[J]. Renew. Energy, 2016, 96:  960-965. doi: 10.1016/j.renene.2016.04.039

  6. [6]

     Zhang Y, Wang L J, Tang B T, Lu R W, Zhang S F. Form-Stable Phase Change Materials with High Phase Change Enthalpy from the Composite of Paraffin and Cross-Linking Phase Change Structure[J]. Appl. Energy, 2016, 184:  241-246. doi: 10.1016/j.apenergy.2016.10.021

  7. [7]

     Mohamed S A, Al-Sulaiman F A, Ibrahim N I, Zahir M H, Al-Ahmed A, Saidur R, Yilbas B S, Sahin A Z. A Review on Current Status and Challenges of Inorganic Phase Change Materials for Thermal Energy Storage Systems[J]. Renew. Sust. Energ. Rev., 2017, 70:  1072-1089. doi: 10.1016/j.rser.2016.12.012

  8. [8]

     Tong X, Li N Q, Zeng M, Wang Q W. Organic Phase Change Materials Confined in Carbon-Based Materials for Thermal Properties Enhancement: Recent Advancement and Challenges[J]. Renew. Sust. Energ. Rev., 2019, 108:  398-422. doi: 10.1016/j.rser.2019.03.031

  9. [9]

     Matsuishi K, Ishihara T, Onari S, Chang Y H, Park C H. Optical Properties and Structural Phase Transitions of Lead-Halide Based Inorganic-Organic 3D and 2D Perovskite Semiconductors under High Pressure.Phys[J]. Status Solidi B-Basic Solid State Phys., 2004, 241(14):  3328-3333. doi: 10.1002/pssb.200405229

  10. [10]

      Zhang Y Q, Li M, Xu G C. Phase Transition and Dielectric Response Originating from Disorder-Order Transition in the In-Based Organic-Inorganic Hybrid Material[NH₃(CH₂)₅NH₃][InCl ₅(H₂O)] ·H₂O[J]. Eur. J. Inorg. Chem., 2021, 2021(13):  1251-1255. doi: 10.1002/ejic.202001156

  11. [11]

      Li M, Xu G C, Xin W B, Zhang Y Q. Switchable Dielectric Behavior and Order-Disorder Phase Transition in a New Organic-Inorganic Hybrid Compound: (CH₃NH ₃)₄[InCl₆]Cl[J]. Eur. J. Inorg. Chem., 2020, 2020:  626-630. doi: 10.1002/ejic.201901303

  12. [12]

      Lv X H, Liao W Q, Li P F, Wang Z X, Mao C Y, Zhang Y. Dielectric and Photoluminescence Properties of a Layered Perovskite-Type Organic-Inorganic Hybrid Phase Transition Compound: NH₃(CH₂)₅ NH₃MnCl₄[J]. J. Mater. Chem. C, 2016, 4:  1881-1885. doi: 10.1039/C5TC04114G

  13. [13]

      Billing D G, Lemmerer A. Synthesis, Characterization and Phase Transitions in the Inorganic-Organic Layered Perovskite-Type Hybrids (C_nH_{2n +1}NH ₃)₂PbI₄, n=4, 5 and 6[J]. Acta Crystallogr. Sect. B, 2007, B63:  735-747.

  14. [14]

      Billing D G, Lemmerer A. Synthesis, Characterization and Phase Transitions of the Inorganic-Organic Layered Perovskite-Type Hybrids (C_nH_{2n +1}NH ₃)₂PbI₄ (n=12, 14, 16 and 18)[J]. New J. Chem., 2008, 32(10):  1736-1746. doi: 10.1039/b805417g

  15. [15]

      Wang B, Ma D W, Zhao H X, Long L S, Zheng L S. Room Temperature Lead-Free Multiaxial Inorganic-Organic Hybrid Ferroelectric[J]. Inorg. Chem., 2019, 58(20):  13953-13959. doi: 10.1021/acs.inorgchem.9b01793

  16. [16]

      Fu X Q, Hang T, Ye Q, Xiong R G. Synthesis, Structure and Dielectric Deuterated Effect of a Novel Organic-Inorganic Hybrid Compound[J]. Inorg. Chem. Commun., 2011, 14(1):  281-284. doi: 10.1016/j.inoche.2010.11.014

  17. [17]

      Tang Y Y, Ai Y, Liao W Q, Li P F, Wang Z X, Xiong R G. H/F-Substitution-Induced Homochirality for Designing High-T_c Molecular Perovskite Ferroelectrics[J]. Adv. Mater., 2019, 31(29):  1902163. doi: 10.1002/adma.201902163

  18. [18]

      Cheng H, Yang M J, Xu Y Q, Li M Z, Ai Y. Target Designing Phase Transition Materials through Halogen Substitution[J]. ChemPhysChem, 2021, 22(8):  752-756. doi: 10.1002/cphc.202100040

  19. [19]

      Ye Q, Zhao H, Qu Z R, Fu D W, Xiong R G, Cui Y P, Akutagawa T, Chan P W H, Nakamura T. Large Anisotropy and Effect of Deuteration on Permittivity in an Olefin Copper(I) Complex[J]. Angew. Chem. Int. Ed., 2007, 46(36):  6852-6856. doi: 10.1002/anie.200700629

  20. [20]

      Hua X N, Liao W Q, Tang Y Y, Li P F, Shi P P, Zhao D, Xiong R G. A Room-Temperature Hybrid Lead Iodide Perovskite Ferroelectric[J]. J. Am. Chem. Soc., 2018, 140(38):  12296-12302. doi: 10.1021/jacs.8b08286

  21. [21]

      Ai Y, Chen X G, Shi P P, Tang Y Y, Li P F, Liao W Q, Xiong R G. Fluorine Substitution Induced High T_c of Enantiomeric Perovskite Ferroelectrics: (R)-and (S)-3-(Fluoropyrrolidinium)MnCl₃[J]. J. Am. Chem. Soc., 2019, 141(10):  4474-4479. doi: 10.1021/jacs.9b00886

  22. [22]

      Shi P P, Lu S Q, Song X J, Chen X G, Liao W Q, Li P F, Tang Y Y, Xiong R G. Two-Dimensional Organic-Inorganic Perovskite Ferroelectric Semiconductors with Fluorinated Aromatic Spacers[J]. J. Am. Chem. Soc., 2019, 141(45):  18334-18340. doi: 10.1021/jacs.9b10048

  23. [23]

      Wang Z X, Zhang Y, Tang Y Y, Li P F, Xiong R G. Fluoridation Achieved Antiperovskite Molecular Ferroelectric in (CH₃)₂(F-CH₂CH₂)NH₃(CdCl₃)(CdCl ₄)[J]. J. Am. Chem. Soc., 2019, 141(10):  4372-4378. doi: 10.1021/jacs.8b13109

  24. [24]

      Chu L L, Zhang T, Gao Y F, Zhang W Y, Shi P P, Ye Q, Fu D W. Fluorine Substitution in Ethylamine Triggers Second Harmonic Generation in Noncentrosymmetric Crystalline NH₃CH₂CH₂F₃BiCl₆[J]. Chem. Mater., 2020, 32(16):  6968-6974. doi: 10.1021/acs.chemmater.0c02223

  25. [25]

      Ye H Y, Zhou Q H, Niu X H, Liao W Q, Fu D W, Zhang Y, You Y M, Wang J L, Chen Z N, Xiong R G. High-Temperature Ferroelectricity and Photoluminescence in a Hybrid Organic-Inorganic Compound: (3-Pyrrolinium)MnCl₃[J]. J. Am. Chem. Soc., 2015, 137(40):  13148-13154. doi: 10.1021/jacs.5b08290

  26. [26]

      Li P F, Tang Y Y, Wang Z X, Ye H Y, You Y M, Xiong R G. Anomalously Rotary Polarization Discovered in Homochiral Organic Ferroelectrics[J]. Nat. Commun., 2016, 7:  13635. doi: 10.1038/ncomms13635

  27. [27]

      Zhang W Y, Tang Y Y, Li P F, Shi P P, Liao W Q, Fu D W, Ye H Y, Zhang Y, Xiong R G. Precise Molecular Design of High-T_c 3D Organic-Inorganic Perovskite Ferroelectric: MeHdabco RbI₃ (MeHdabco=N-Methyl-1, 4-diazoniabicyclo[2.2.2]octane)[J]. J. Am. Chem. Soc., 2017, 139(31):  10897-10902. doi: 10.1021/jacs.7b06013

  28. [28]

      Liao W Q, Zhao D, Tang Y Y, Zhang Y, Li P F, Shi P P, Chen X G, You Y M, Xiong R G. A Molecular Perovskite Solid Solution with Piezoelectricity Stronger than Lead Zirconate Titanate[J]. Science, 2019, 363(6432):  1206-1210. doi: 10.1126/science.aav3057

  29. [29]

      Zhang H Y, Tang Y Y, Shi P P, Xiong R G. Toward the Targeted Design of Molecular Ferroelectrics: Modifying Molecular Symmetries and Homochirality[J]. Acc. Chem. Res., 2019, 52(7):  1928-1938. doi: 10.1021/acs.accounts.8b00677

  30. [30]

      You Y M, Liao W Q, Zhao D, Ye H Y, Zhang Y, Zhou Q, Niu X, Wang J, Li P F, Fu D W, Wang Z, Gao S, Yang K, Liu J M, Li J, Yan Y, Xiong R G. An Organic-Inorganic Perovskite Ferroelectric with Large Piezoelectric Response[J]. Science, 2017, 357(6348):  306-309. doi: 10.1126/science.aai8535

  31. [31]

      Li P F, Tang Y Y, Liao W Q, Shi P P, Hua X N, Zhang Y, Wei Z, Cai H, Xiong R G. Experimental Evidence for a Triboluminescent Antiperovskite Ferroelectric: Tris(trimethylammonium) catena-Tri-μ-chloro-Manganate(Ⅱ) Tetrachloromanganate(Ⅱ)[J]. Angew. Chem. Int. Ed., 2018, 57(37):  11939-11942. doi: 10.1002/anie.201805625

  32. [32]

      Liao W Q, Tang Y Y, Li P F, You Y M, Xiong R G. Competitive Halogen Bond in the Molecular Ferroelectric with Large Piezoelectric Response[J]. J. Am. Chem. Soc., 2018, 140(11):  3975-3980. doi: 10.1021/jacs.7b12524

  33. [33]

      Wei Z, Liao W Q, Tang Y Y, Li P F, Li P P, Cai H, Xiong R G. Discovery of an Antiperovskite Ferroelectric in[(CH₃)₃NH]₃(MnBr₃) (MnBr₄)[J]. J. Am. Chem. Soc., 2018, 140(26):  8110-8113. doi: 10.1021/jacs.8b05037

  34. [34]

      Ye H Y, Tang Y Y, Li P F, Liao W Q, Gao J X, Hua X N, Cai H, Shi P P, You Y M, Xiong R G. Metal-Free Three-Dimensional Perovskite Ferroelectrics[J]. Science, 2018, 361(6398):  151-155. doi: 10.1126/science.aas9330

  35. [35]

      Yang C K, Chen W N, Ding Y T, Wang J, Rao Y, Liao W Q, Tang Y Y, Li P F, Wang Z X, Xiong R G. The First 2D Homochiral Lead Iodide Perovskite Ferroelectrics: [R-and S-1-(4-Chlorophenyl)ethylammonium]₂PbI₄[J]. Adv. Mater., 2019, 31(16):  1808088. doi: 10.1002/adma.201808088

  36. [36]

      Fu D W, Gao J X, He W H, Huang X Q, Liu Y H, Ai Y. High-T_c Enantiomeric Ferroelectrics Based on Homochiral Dabco-Derivatives (Dabco=1, 4-Diazabicyclo[2.2.2]octane)[J]. Angew. Chem. Int. Ed., 2020, 59(40):  17477-17481. doi: 10.1002/anie.202007660

  37. [37]

      Rodriguez-Rodriguez A, Regueiro-Figueroa M, Esteban-Gomez D, Rodriguez-Blas T, Patinec V, Tripier R, Tircso G, Carniato F, Botta M, Platas-Iglesias C. Definition of the Labile Capping Bond Effect in Lanthanide Complexes[J]. Chem. Eur. J., 2017, 23(5):  1110-1117. doi: 10.1002/chem.201604390

  38. [38]

      Tickle I J, Laskowski R A, Moss D S. Error Estimates of Protein Structure Coordinates and Deviations from Standard Geometry by Full-Matrix Refinement of γB-and βB2-crystallin[J]. Acta Crystallogr. Sect. D, 1998, D54:  243-252.

  39. [39]

      Dolomanov O V, Blake A J, Champness N R, Schroder M. OLEX: New Software for Visualization and Analysis of Extended Crystal Structures[J]. J. Appl. Crystallogr., 2003, 36:  1283-1284. doi: 10.1107/S0021889803015267

  40. [40]

      Strokopytov B V. How to Multiply a Matrix of Normal Equations by an Arbitrary Vector Using FFT[J]. Acta Crystallogr. Sect. A, 2008, A64:  601-612.

  41. [41]

      Lebuis A M, Young J M C, Beauchamp A L. Nonstoichiometric Chloride Salts of Dioxotetrakis (Imidazole) Rhenium(Ⅴ) Cations[J]. Can. J. Chem., 1993, 71(12):  2070-2078. doi: 10.1139/v93-257

  42. [42]

      Gassman P L, Mccloy J S, Soderquist C Z, Schweiger M J. Raman Analysis of Perrhenate and Pertechnetate in Alkali Salts and Borosilicate Glasses[J]. J. Raman Spectrosc., 2014, 45(1):  139-147. doi: 10.1002/jrs.4427

  43. [43]

      Hetmańczyk Ł, Hetmańczyk J. Phase Transition and NH₃ Dynamics in[Ni(NH₃)₄](ReO₄)₂ Studied by Infrared Absorption, X -ray Powder Diffraction and Neutron Scattering Methods[J]. Chem. Phys., 2016, 469-470:  9-15. doi: 10.1016/j.chemphys.2016.02.011

  44. [44]

      Castellon C, Guenther E, Mehling H, Hiebler S, Cabeza L F. Determination of the Enthalpy of PCM as a Function of Temperature Using a Heat-Flux DSC-A Study of Different Measurement Procedures and Their Accuracy[J]. Int. J. Energy Res., 2008, 32(13):  1258-1265. doi: 10.1002/er.1443

  45. [45]

      Sharma D, MacDonald J C, Iannacchione G S. Thermodynamics of Activated Phase Transitions of 8CB: DSC and MC Calorimetry[J]. J. Phys. Chem. B, 2006, 110:  16679-16684.

  46. [46]

      Cai H L, Zhang Y, Fu D W, Zhang W, Liu T, Yoshikawa H, Awaga K, Xiong R G. Above-Room-Temperature Magnetodielectric Coupling in a Possible Molecule -Based Multiferroic: Triethylmethylammonium Tetrabromoferrate(Ⅲ)[J]. J. Am. Chem. Soc., 2012, 134(45):  18487-18490. doi: 10.1021/ja3073319

  47. [47]

      Li P F, Liao W Q, Tang Y Y, Qiao W, Zhao D, Ai Y, Yao Y F, Xiong R G. Organic Enantiomeric High-T_c Ferroelectrics[J]. Proc. Natl. Acad. Sci. U.S.A., 2019, 116(13):  5878-5885. doi: 10.1073/pnas.1817866116

  48. [48]

      Huang H, Zhang L, Wang Y, Han X D, Wu Y, Zhang Z, Gan F. Changes of Optical, Dielectric, and Structural Properties of Si ₁₅Sb₈₅ Phase Change Memory Thin Films under Different Initializing Laser Power[J]. J. Alloy. Compd., 2011, 509(16):  5050-5054. doi: 10.1016/j.jallcom.2011.02.031

  49. [49]

      Wang H T, Kong L H, Shi P P, Li Q, Ye Q, Fu D W. The Structure and Dielectric Properties of Ionic Compounds with Flexible Ammonium Moiety[J]. Chin. Chem. Lett., 2015, 26(3):  382-386. doi: 10.1016/j.cclet.2014.10.025

  50. [50]

      Nguyen M D. Impact of Fatigue Behavior on Energy Storage Performance in Dielectric Thin-Film Capacitors[J]. J. Eur. Ceram. Soc., 2020, 40(54):  1886-1895.

• 

  Scheme 1  Molecular structures of cyclen and Me-cyclen

  下载: 全尺寸图片 幻灯片
  

  Figure 1  DSC curves of 1 (red) and 2 (blue) in heating and cooling runs

  下载: 全尺寸图片 幻灯片
  

  Figure 2  Temperature dependence of the real parts (ε') of 1 and 2 at 1 MHz upon heating and cooling

  下载: 全尺寸图片 幻灯片
  

  Figure 3  Crystal structures of 1 (a) and 2 (b) at room temperature, where the dashed lines represent the hydrogen bonds

  下载: 全尺寸图片 幻灯片

  Table 1.  Crystallographic data for compounds 1 and 2

  Parameter	1	2
  Formula	C8H22N4O8Re2	C9H24N4O8Re2
  Formula weight	674.72	688.74
  Crystal system	Triclinic	Monoclinic
  Space group	P1	P21/n
  a/nm	0.868 12(2)	0.866 45(7)
  b/nm	0.961 38(3)	1.647 32(9)
  c/nm	1.190 09(3)	1.282 35(8)
  α/(°)	82.214(2)
  β/(°)	70.818(2)	92.272(6)
  γ/(°)	63.287(2)
  V/nm3	0.837 89(4)	1.828 9(2)
  Z	2	4
  Dc/(g·cm-3)	2.674	2.501
  F(000)	624	1280
  θmax	25	24.99
  μ(Mo Kα)/mm-1	14.475	13.266
  Total reflection	8 244	13 102
  Unique reflection	2 953 (Rint=0.064 9)	3 221 (Rint=0.041 8)
  Number of variables	200	209
  R1, wR2 [I > 2σ(I)]	0.051 1, 0.138 8	0.036 3, 0.082 9
  R1, wR2 (all data)	0.055 0, 0.142 0	0.050 0, 0.088 3
  GOF	1.093	1.032

  下载: 导出CSV

  Table 2.  Thermal values in the phase transition of 1 and 2

  Compound	Tp, endoa/K	Tp, exob/K	ΔTc/K	ΔH/(kJ·mol-1)	ΔS/(J·mol-1·K-1)	N
  1	324	313	11	7.43	22.94	15.79
  2	384	361	23	12.70	33.08	53.45
  a Tp, endo is the temperature at the endothermic peak; b Tp, exo is the temperature at the exothermic peak; cΔT=Tp, endo-Tp, exo.

  下载: 导出CSV
•