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2864602 
Journal Article 
Evidence for a C-H-center dot center dot center dot pi type weak interaction: 1 : 1 complex of styrene with acetylene studied by mass selective high-resolution UV spectroscopy and ab initio calculations 
Chervenkov, S; Wang, P; Braun, JE; Chakraborty, T; Neusser, HJ 
2007 
1 
Physical Chemistry Chemical Physics
ISSN: 1463-9076
EISSN: 1463-9084 
9 
7 
837-845 
English 
17287877 
WOS:000244062900005 
The 1 : 1 complex of styrene with acetylene has been studied by mass selective low- and high-resolution UV resonance-enhanced two-photon ionisation (R2PI) spectroscopy combined with genetic-algorithm-based computer-aided fit of the spectra with partial rotational resolution, and high level ab initio quantum chemistry calculations. Two stable conformeric geometries of the 1 : 1 complex of styrene and acetylene have been theoretically found: one with acetylene binding to styrene as a proton donor, and one with acetylene acting as a proton acceptor. From the analysis of the vibronic structure of the S1<-- S0 spectrum and the fit of the highly resolved spectrum of the 0 origin band of the complex it is shown that the favoured conformation is the one in which acetylene binds to the benzene ring of styrene through formation of a non-conventional hydrogen bond of C-H...pi type with no marked change of the transition moment orientation of styrene. The styrene moiety remains planar and the acetylene molecule is tilted by a small angle of 4 degrees relative to the C6 symmetry axis of the benzene ring, most likely due to the reduced symmetry of the benzene ring pi electrons rather than to a direct interaction with the vinyl group.