两例配位聚合物[MCl2β-ala)]n(M=Co,Ni;β-ala=3-氨基丙酸)的结构相变
Phase Transitions of Two Coordination Polymers [MCl2(β-ala)]n (M=Co, Ni; β-ala=3-Aminopropionic Acid)
作者单位E-mail
苏榆钧 中山大学化学学院, 广州 510275  
许可 中山大学化学学院, 广州 510275  
袁伟 中山大学化学学院, 广州 510275  
黄瑞康 中山大学化学学院, 广州 510275  
张伟雄 中山大学化学学院, 广州 510275 zhangwx6@mail.sysu.edu.cn 
陈小明 中山大学化学学院, 广州 510275 cxm@mail.sysu.edu.cn 
摘要: 利用3-氨基丙酸( β-ala)和过渡金属氯化物构筑了2例互为异质同晶的配位聚合物[MCl2β-ala)]n(M=Co2+1),Ni2+2)),并通过差示扫描量热法、变温X射线单晶衍射以及变温介电测试研究了它们的结构相变。配合物12的结构中,相邻的M2+离子通过2个氯离子和1个双齿羧基的桥联作用形成一维配位链。在升/降温过程中,12分别在236、224 K和309、302 K附近发生高温相(Pnam)与低温相(Pna21)之间的温致结构相变;该相变主要是由配体的铵乙基由高温相中的两重无序状态冻结为低温相中的有序状态而引起的,该有序-无序型相变使这两个化合物在相变温度附近都表现出介电台阶及介电弛豫的共存现象。
关键词: 配位聚合物  结构相变  有序-无序相变  介电异常
基金项目: 国家自然科学基金(No.21290173,91422302,21671202)资助项目。
Abstract: Two new isomorphic coordination polymers, [MCl2( β-ala)]n (M=Co2+ (1) or Ni2+ (2), β-ala=3-aminopropi-onic acid), were constructed by assembling 3-aminopropionic acid and transition metal chlorides. Their reversible structural phase transitions were disclosed by differential scanning calorimetry (DSC), variable-temperature single-crystal X-ray diffraction and dielectric measurements. In 1 and 2, the adjacent M2+ ions are mix-bridged by two μ2-Cl- ions and a syn-syn carboxylate group from β-ala ligand, resulting in one-dimensional polymeric coor-dination chains. Both 1 and 2 undergo reversible phase transitions, which occur at critical temperature (Tc-heating, Tc-cooling) of 236, 224 K and 309, 302 K, respectively, with a change of space group between Pnam at the high-temperature phase (HTP) and Pna21 at the low-temperature phase (LTP). The phase transitions are mainly related to the dynamic change of ammonium ethyl group from two-fold disorder in HTP to static ordered state in LTP. Such order-disorder structural phase transitions lead to the coexistence of step-like dielectric anomaly and dielectric relaxation in the vicinity of the phase transition.
Keywords: coordination polymer  structural phase transition  order-disorder phase transition  dielectric anomaly
投稿时间:2017-07-31 修订日期:2017-09-21
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苏榆钧,许可,袁伟,黄瑞康,张伟雄,陈小明.两例配位聚合物[MCl2β-ala)]n(M=Co,Ni;β-ala=3-氨基丙酸)的结构相变[J].无机化学学报,2017,33(11):2005-2010.
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