title: Computational study on C-H...π interactions of acetylene with benzene, 1,3,5-trifluorobenzene and coronene.
abstract: Meta-hybrid density functional theory calculations using M06-2X/6-31+G(d,p) and M06-2X/6-311+G(d,p) levels of theory have been performed to understand the strength of C-H(…)π interactions of two possible types for benzene-acetylene, 1,3,5-trifluorobenzene-acetylene and coronene-acetylene complexes. Our study reveals that the C-H(...)π interaction complex where acetylene located above to the center of benzene ring (classical T-shaped) is the lowest energy structure. This structure is twice more stable than the configuration characterized by H atom of benzene interacting with the π-cloud of acetylene. The binding energy of 2.91 kcal/mol calculated at the M06-2X/6-311+G(d,p) level for the lowest energy configuration (1A) is in very good agreement with the experimental binding energy of 2.7 ± 0.2 kcal/mol for benzene-acetylene complex. Interestingly, the C-H(...)π interaction of acetylene above to the center of the aromatic ring is not the lowest energy configuration for 1,3,5-trifluorobenzene-acetylene and coronene-acetylene complexes. The lowest energy configuration (2A) for the former complex possesses both C-H(...)π interaction and C-H(...)F hydrogen bond, while the lowest energy structure for the coronene-acetylene complex involves both π-π and C-H(...)π interactions. C-H stretching vibrational frequencies and the frequency shifts are reported and analyzed for all of the configurations. We observed red-shift of the vibrational frequency for the stretching mode of the C-H bond that interacts with the π-cloud. Acetylene in the lowest-energy structures of the complexes exhibits significant red-shift of the C-H stretching frequency and change in intensity of the corresponding vibrational frequency, compared to bare acetylene. We have examined the molecular electrostatic potential on the surfaces of benzene, 1,3,5-trifluorobenzene, coronene and acetylene to explain the binding strengths of various complexes studied here.
authors.affiliation: Interdisciplinary Center for Nanotoxicity, Department of Chemistry and Biochemistry, Jackson State University, 1400 J. R. Lynch Street, Jackson, MS 39217, USA. dina@icnanotox.org
authors.forename: Tandabany C
authors.initials: TC
authors.lastname: Dinadayalane
authors.forename: Guvanchmyrat
authors.initials: G
authors.lastname: Paytakov
authors.forename: Jerzy
authors.initials: J
authors.lastname: Leszczynski
mesh_terms: D000114:Acetylene / Q000737:chemistry*; D001554:Benzene / Q000737:chemistry*; D003198:Computer Simulation; D005464:Fluorobenzenes / Q000737:chemistry*; D006860:Hydrogen Bonding; D011083:Polycyclic Compounds / Q000737:chemistry*; D011789:Quantum Theory; D013816:Thermodynamics
chemical_list: D005464:Fluorobenzenes; D011083:Polycyclic Compounds; C012256:coronene; C519635:1,3,5-trifluorobenzene; D001554:Benzene; D000114:Acetylene