乙酸 - 水络合物：首次观察到含有高能乙酸构象异构体的结构。

Acetic acid-water complex: The first observation of structures containing the higher-energy acetic acid conformer.

作者信息

Lopes Susy, Fausto Rui, Khriachtchev Leonid

机构信息

CQC, Department of Chemistry, University of Coimbra, Rua Larga, P-3004-535 Coimbra, Portugal.

Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki, Finland.

出版信息

J Chem Phys. 2016 Feb 28;144(8):084308. doi: 10.1063/1.4942027.

DOI:10.1063/1.4942027

PMID:26931703

Abstract

Non-covalent interaction of acetic acid (AA) and water is studied experimentally by IR spectroscopy in a nitrogen matrix and theoretically at the MP2 and coupled-cluster with single and double and perturbative triple excitations [CCSD(T)]/6-311++G(2d,2p) levels of theory. This work is focused on the first preparation and characterization of complexes of higher-energy (cis) conformer of AA with water. The calculations show three 1:1 structures for the trans-AA⋯H2O complexes and three 1:1 structures for the cis-AA⋯H2O complexes. Two trans-AA⋯H2O and two cis-AA⋯H2O complexes are found and structurally assigned in the experiments. The two cis-AA⋯ ⋅ H2O complexes are obtained by annealing of a matrix containing water and cis-AA molecules prepared by selective vibrational excitation of the ground-state trans form. The less stable trans-AA⋯H2O complex is obtained by vibrational excitation of the less stable cis-AA⋯H2O complex. In addition, the 1:2 complexes of trans-AA and cis-AA with water molecules are studied computationally and the most stable forms of the 1:2 complexes are experimentally identified.

摘要

通过红外光谱在氮基质中对乙酸（AA）与水的非共价相互作用进行了实验研究，并在MP2以及单双激发和微扰三重激发耦合簇[CCSD(T)]/6-311++G(2d,2p)理论水平上进行了理论研究。这项工作的重点是首次制备和表征AA高能（顺式）构象体与水的配合物。计算结果表明，反式AA⋯H₂O配合物有三种1:1结构，顺式AA⋯H₂O配合物也有三种1:1结构。实验中发现并确定了两种反式AA⋯H₂O和两种顺式AA⋯H₂O配合物的结构。通过对含有水和顺式AA分子的基质进行退火处理，得到了两种顺式AA⋯H₂O配合物，该基质是通过对基态反式异构体进行选择性振动激发制备的。通过对较不稳定的顺式AA⋯H₂O配合物进行振动激发，得到了较不稳定的反式AA⋯H₂O配合物。此外，还对反式AA和顺式AA与水分子的1:2配合物进行了计算研究，并通过实验确定了1:2配合物的最稳定形式。