Novel intermolecular C-H pi interactions: An ab initio and density functional theory study

被引:50
作者
Fan, MF
Lin, ZY
McGrady, JE
Mingos, DMP
机构
[1] HONG KONG UNIV SCI & TECHNOL,DEPT CHEM,KOWLOON,HONG KONG
[2] UNIV LONDON IMPERIAL COLL SCI TECHNOL & MED,DEPT CHEM,KENSINGTON SW7 2AY,ENGLAND
来源
JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2 | 1996年 / 04期
关键词
D O I
10.1039/p29960000563
中图分类号
O62 [有机化学];
学科分类号
070303 ; 081704 ;
摘要
The recent characterisation of short contacts between chloroform solvate molecules and the C-C triple bond of gold ethynides has prompted a theoretical investigation of the strength of C-H ...pi interactions. Extensive ab initio and density functional theory calculations have been performed on a variety of model systems displaying a T-shaped C-H ...pi motif. The interaction of ethyne, C2H2, with a variety of small proton donor molecules (HCN, CH4-nCln, n = 0-3) is invariably found to be weak (Delta E(int) < 10 kJ mol(-1)). Replacement of the two acetylenic protons with more electron-donating sodium atoms increases the electron density in the C-C pi bond and results in a substantial increase in the interaction with the proton donor. The calculated interaction energies rise to as much as 60 kJ mol(-1) in the case of C2Na2 ... CHCl3. The interaction of CHCl3 with a model gold ethynide, H3PAuCCAuPH3, is intermediate between these two extremes, ab initio and density functional calculations both giving estimates of ca. 25 kJ mol(-1) comparable to a reasonably strong hydrogen bond. The unusually strong C-H ...pi interactions in the gold ethynide arise directly as a consequence of the electron-donating properties of the AuPR(3) fragment and are fundamentally different to the much weaker C-H ...pi interactions in purely organic systems.
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页码:563 / 568
页数:6
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