Coordination Environments and Pi-Conjugation in Dense Lithium Coordination Polymers
Coordination Environments and Pi-Conjugation in Dense Lithium Coordination Polymers
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致密锂配位聚合物中的配位环境和π共轭
DOI：
10.1039/c5ce01658d
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发表时间：
2016
期刊：
影响因子：
3.1
通讯作者：
A. K. Cheetham
中科院分区：
文献类型：
--
作者：
S. Tominaka;H. H.-M. Yeung;S. Henke;A. K. Cheetham
了解锂氧配位体系对于制备更好的锂导体以及锂离子电池活性材料具有重要意义。本文通过合成和分析六种由锂离子和蒽醌衍生物阴离子组成的新晶体，对锂配位聚合物（LCP）中的配位环境进行了系统的研究。通过单晶X射线衍射确定了它们的结构：（1）[Li_2（23 dcaq）（H_2 O）]，空间群P21/c，（2）[Li（23 dcaqH）]，（3）[Li_2（15 dhaq）（H_2 O）_2]，（4）[Li_2（14 dhaq）（H_2 O）_2]，Pnma，（5）P212121中的[Li（14 dhaqH）（H2O）]和（6）P212121中的[Li（14 hnaq）（H2O）]（2, 3dcaq 2 − = 2，3-二羧基-aq，14 dhaq 2 − = 1，4-二羟基-aq，1, 5dhaq 2 − = 1，5-二羟基-aq和14 hnaq − = 1-羟基-4-硝基-aq）。通过对这些材料以及其他LCP的全面结构分析，我们发现，当考虑阴离子有机分子π-共轭体系中最长的C-O键及其与Li离子的配位时，C-O之间存在弱的反关系。Li-O键长。此外，尽管显示出低于2 eV的光学带边和1D π-堆叠连接性，但对1-6的单晶的电导率测量证实它们都是电子绝缘体。我们合理的基础上的π-轨道离域，这是更受限制的aq为基础的LCP相比，已知的半导体混合材料的这一发现。
The understanding of lithium–oxygen coordination systems is important for making better lithium conductors as well as active materials for lithium ion batteries. Here, we report a systematic investigation on coordination environments in lithium coordination polymers (LCPs) through the syntheses and analyses of six new crystals composed of lithium ions and anthraquinone (aq) derivative anions, where the negative charges are distributed in π-conjugation systems. Their structures were determined by single-crystal X-ray diffraction to be (1) [Li2(23dcaq)(H2O)] in space group P21/c, (2) [Li(23dcaqH)] in P21/c, (3) [Li2(15dhaq)(H2O)2] in P21/c, (4) [Li2(14dhaq)(H2O)2] in Pnma, (5) [Li(14dhaqH)(H2O)] in P212121 and (6) [Li(14hnaq)(H2O)] in P212121 (23dcaq2− = 2,3-dicarboxy-aq, 14dhaq2− = 1,4-dihydroxy-aq, 15dhaq2− = 1,5-dihydroxy-aq and 14hnaq− = 1-hydroxy-4-nitro-aq). Through the comprehensive structure analysis of these materials as well as other LCPs, we found that when considering the longest C–O bond in the π-conjugation system of an anionic organic molecule and its coordination to a Li ion, there is a weak inverse relationship between the C–O and Li–O bond lengths. In addition, despite exhibiting optical band edges below 2 eV and 1D π-stacking connectivity, conductivity measurements on single crystals of 1–6 confirmed that they are all electronic insulators. We rationalize this finding on the basis of π-orbital delocalization, which is more restricted in the aq-based LCPs compared to known semiconducting hybrid materials.