title: Binary complexes of ammonia with phenylacetylenes: a combined experimental and computational approach to explore multiple minima on intermolecular potentials.
abstract: The hydrogen-bonded complexes of phenylacetylene, 4-fluorophenylacetylene, 2-fluorophenylacetylene, and 2,6-difluorophenylacetylene with ammonia are investigated using IR-UV double resonance spectroscopy in combination with high-level ab initio calculations at the CCSD(T)/CBS level of theory. The C-H···N hydrogen-bonded complex, which involves an interaction of ammonia with the acetylenic CH group is the global minimum and is observed in all four cases investigated. In addition, phenylacetylene and 4-fluorophenylacetylene form a quasi-planar cyclic complexes with ammonia incorporating N-H···π and C-H···N hydrogen bonds, wherein the π-electron density of the acetylenic C≡C bond acts as an acceptor to the N-H group of ammonia. A third ammonia complex is observed for 4-fluorophenylacetylene in which ammonia interacts with the fluorine atom once again, leading to the formation of a quasi-planar cyclic complex. The substitution of the fluorine atom on the phenyl ring of phenylacetylene modulates the intermolecular potentials, which are dependent on the position of the substitution.
authors.affiliation: Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 40007, India.
authors.forename: Arghya
authors.initials: A
authors.lastname: Dey
authors.forename: Sohidul Islam
authors.initials: SI
authors.lastname: Mondal
authors.forename: G Naresh
authors.initials: GN
authors.lastname: Patwari
mesh_terms: D000114:Acetylene / Q000031:analogs & derivatives* / Q000737:chemistry; D000641:Ammonia / Q000737:chemistry*; D006860:Hydrogen Bonding; D015394:Molecular Structure; D011789:Quantum Theory
chemical_list: C044736:phenylacetylene; D000641:Ammonia; D000114:Acetylene