Takahashi Kiyonori, Miyazaki Yuji, Noro Shin-Ichiro, Nakano Motohiro, Nakamura Takayoshi, Akutagawa Tomoyuki
Research Institute for Electronic Science, Hokkaido University, Sapporo, Hokkaido 001-0020, Japan.
Research Center for Thermal and Entropic Science, Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043, Japan.
Dalton Trans. 2021 Oct 12;50(39):13680-13685. doi: 10.1039/d1dt02118d.
A series of mononuclear Cu complexes, [Cu(4-FBA)(py)(HO)] (1), [Cu(3-FBA)(py)(HO)] (2), and [Cu(3,4-FBA)(py)(HO)] (3), where 4-FBA = 4-fluorobenzoate, 3-FBA = 3-fluorobenzoate, 3,4-FBA = 3,4-difluorobenzoate, and py = pyridine, respectively, was synthesized and the complexes crystallographically identified. All the Cu complex crystals share a one-dimensional O-H⋯O hydrogen-bonding chain substructure, although the mutual alignment of fluorinated benzoate (FBA) ligands exhibits subtle differences among the various compounds, , FBA ligands align in an antiparallel fashion in crystals 1 and 3, while 3-FBA ligands in crystal 2 are interdigitated with a tilt along the axis. Reversible phase transitions were found upon heating at 170.7, 171.3, and 267.5 K for crystals 1, 2, and 3, respectively; all crystals showed approximately 3% expansion and shrinkage of the intermolecular O-H⋯O hydrogen bond distances associated with the thermally activated orientational fluctuations of the FBA ligands in crystals 1 and 3. The increase in dielectric constant with increasing temperature, at 240 K, activated molecular fluctuation in the 3,4-FBA ligands in crystal 3. Heat capacity measurements indicated that both the expansion and shrinkage of hydrogen bonds, and the molecular fluctuation in 3,4-FBA ligands, contributed to phase transition, and the latter caused dipole fluctuation, resulting in a dielectric anomaly in crystal 3.
合成了一系列单核铜配合物，分别为[Cu(4 - FBA)(py)(HO)] (1)、[Cu(3 - FBA)(py)(HO)] (2)和[Cu(3,4 - FBA)(py)(HO)] (3)，其中4 - FBA = 4 - 氟苯甲酸酯，3 - FBA = 3 - 氟苯甲酸酯，3,4 - FBA = 3,4 - 二氟苯甲酸酯，py = 吡啶，并通过晶体学方法对这些配合物进行了鉴定。尽管氟化苯甲酸酯（FBA）配体的相互排列在不同化合物之间存在细微差异，但所有铜配合物晶体都具有一维O - H⋯O氢键链亚结构。在晶体1和3中，FBA配体以反平行方式排列，而在晶体2中，3 - FBA配体沿轴倾斜相互交错排列。分别在170.7、171.3和267.5 K加热时，发现晶体1、2和3发生了可逆相变；对于晶体1和3，所有晶体中与FBA配体的热激活取向波动相关的分子间O - H⋯O氢键距离均显示出约3%的膨胀和收缩。在240 K时，晶体3中3,4 - FBA配体的介电常数随温度升高而增加，激活了分子波动。热容测量表明，氢键的膨胀和收缩以及3,4 - FBA配体中的分子波动都对相变有贡献，后者导致偶极波动，从而在晶体3中产生介电异常。
