title: A theoretical study of nonlinearity in heterocyclic hydrogen-bonded complexes.
abstract: Ab initio calculations are performed at the MP2/6-311++G(d,p) and DFT/B3LYP/6-311++G(d,p) theoretical levels to obtain geometries, H-bond energies and harmonic infrared vibrational properties for the Cs symmetry structures of heterocyclic hydrogen-bonded complexes, CnHmY-HX. The H-bond lengths in DFT/B3LYP calculation level are in better agreement with the experimental values than the MP2 results. The geometry optimization are interpreted in terms of hydrogen bond nonlinearity represented by theta; and phi angles, once the hydrogen bond is formed among n-electrons pairs of the heteroatom in heterocyclic and the hydrogen atom in HX. The hydrogen bond energy after of the zero-point vibrational energy (ZPE) and basis set superposition error (BSSE) corrections are overestimated at DFT/B3LYP, whereas the MP2 BSSE corrections are very large than corresponding DFT/B3LYP. For example, the BSSE corrections for the C2H4S-HNC complex are 7.60 and 0.09 kJ mol(-1) in MP2 and DFT/B3LYP calculations levels, respectively. The new vibrational modes in infrared harmonic spectrum arising from complexation show several interesting features, especially the intermolecular stretching mode.
authors.affiliation: Departamento de Química, Universidade Federal da Paraíba, 58036-300-João Pessoa, PB, Brazil.
authors.forename: B G
authors.initials: BG
authors.lastname: Oliveira
authors.forename: E M
authors.initials: EM
authors.lastname: Duarte
authors.forename: R C M U
authors.initials: RC
authors.lastname: Araújo
authors.forename: M N
authors.initials: MN
authors.lastname: Ramos
authors.forename: A B
authors.initials: AB
authors.lastname: Carvalho
mesh_terms: D004563:Electrochemistry; D006571:Heterocyclic Compounds / Q000737:chemistry*; D006860:Hydrogen Bonding; D015394:Molecular Structure; D013057:Spectrum Analysis
chemical_list: D006571:Heterocyclic Compounds