Issue 1, 2015

Spectroscopic and ab initio investigation of 2,6-difluorophenylacetylene–amine complexes: coexistence of C–H⋯N and lone-pair⋯π complexes and intermolecular coulombic decay

Abstract

Binary complexes of 2,6-difluorophenylacetylene with methylamine, dimethylamine, trimethylamine and triethylamine were investigated using one colour resonant two photon ionization and infrared-optical double resonance spectroscopic techniques combined with high level ab initio calculations. All four amines form CAc–H⋯N hydrogen-bonded complexes. Additionally trimethylamine and triethylamine form complexes characterized by Lp⋯π interactions, due to the electron deficient nature of the phenyl ring of 2,6-difluorophenylacetylene. The Lp⋯π interacting structure of the 2,6-difluorophenylacetylene–trimethylamine complex is about 1.5 kJ mol−1 higher in energy than the CAc–H⋯N hydrogen-bonded structure, which is the global minimum. Energy decomposition analysis indicates that the electrostatics and dispersion interactions favour the formation of CAc–H⋯N and Lp⋯π complexes, respectively. Interestingly the CAc–H⋯N hydrogen-bonded complex of 2,6-difluorophenylacetylene–triethylamine showed a smaller shift in the acetylenic C–H stretching frequency than the 2,6-difluorophenylacetylene–trimethylamine complex. The observed fragmentation of the binary complexes of 2,6-difluorophenylacetylene with the four amines following resonant two-photon ionization can be explained on the basis of the intermolecular coulombic decay process.

Graphical abstract: Spectroscopic and ab initio investigation of 2,6-difluorophenylacetylene–amine complexes: coexistence of C–H⋯N and lone-pair⋯π complexes and intermolecular coulombic decay

Supplementary files

Article information

Article type
Paper
Submitted
02 aug 2014
Accepted
31 okt 2014
First published
31 okt 2014

Phys. Chem. Chem. Phys., 2015,17, 434-443

Spectroscopic and ab initio investigation of 2,6-difluorophenylacetylene–amine complexes: coexistence of C–H⋯N and lone-pair⋯π complexes and intermolecular coulombic decay

S. I. Mondal, A. Dey, S. Sen, G. N. Patwari and D. Ghosh, Phys. Chem. Chem. Phys., 2015, 17, 434 DOI: 10.1039/C4CP03445G

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