Iannuzzi Marcella
Physical Chemistry Institute, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
J Chem Phys. 2006 May 28;124(20):204710. doi: 10.1063/1.2202323.
Heterocycles' aggregates show rather good proton conductivity. In particular, condensed structures formed by imidazole rings that are held together by polymeric chains have attracted some interest as possible candidate materials for fuel cell membranes. However, the details of the proton diffusion process could not be resolved by means of experimental measurements because of the fast rearrangement of the structure after each proton exchange. In this work, we report in detail the results of ab initio molecular dynamics calculations, which were briefly presented in a previous Letter [M. Iannuzzi and M. Parrinello, Phys. Rev. Lett. 93, 025901 (2004)]. The conformational changes associated with the diffusion of protons in model crystalline structures containing chains of imidazole rings are described in the framework of an atomistic approach. In particular, the bonding pattern characterizing the structure of imidazole-2-ethylene-oxide doped by an excess proton is also studied through the calculation of the 1H NMR chemical shifts. The unresolved resonances appearing in the experimental spectra could be associated with specific structural features, in connection with the fluctuating hydrogen bonding. The analysis of the distortions that induce or are induced by the mobility of the protons offers some new hints for the engineering of new proton conducting materials.
杂环聚集体表现出相当良好的质子传导性。特别是，由咪唑环通过聚合物链连接形成的凝聚结构，作为燃料电池膜的潜在候选材料引起了一些关注。然而，由于每次质子交换后结构的快速重排，质子扩散过程的细节无法通过实验测量来解析。在这项工作中，我们详细报告了从头算分子动力学计算的结果，这些结果曾在之前的一篇快报中简要介绍过[M. 伊安努齐和M. 帕里内洛，《物理评论快报》93, 025901 (2004)]。在原子方法的框架内描述了与质子在含有咪唑环链的模型晶体结构中扩散相关的构象变化。特别是，还通过计算1H NMR化学位移研究了由过量质子掺杂的咪唑 - 2 - 环氧乙烷结构的键合模式。实验光谱中出现的未解析共振可能与特定的结构特征有关，这与波动的氢键有关。对由质子迁移引起或诱导质子迁移的畸变的分析为新型质子传导材料的设计提供了一些新线索。
