title: Density functional theory study on the structure and vibrational frequencies of glycylglycine.
abstract: Eleven possible conformers of glycylglycine have been studied by using the BLYP, B3LYP methods of density functional theory and the HF method at the basis set of 6-311++G**. BLYP (using Becke's and Lee-Yang-Parr's correlation functionals), ab initio Hartree-Fock (HF) and hybrid DFT/HF B3LYP calculations have been carried out to study the structure and vibrational spectra of glycylglycine. Glycylglycine crystal structure has been determined by X-ray diffraction analysis. The title compound has been crystallizes in the orthorhombic space group C1, with Z=4. And the unit cell parameters are: a=8.1184(12)A, b=9.5542(14)A, c=7.8192(11)A and V=577.95(15)A(3). Molecular conformation calculations have got 11 possible conformers. In these possible conformers, the most stable one has been selected. The BLYP/6-311++G** and scaled HF/6-311++G** frequencies correspond well with available experimental assignments of the normal vibrational modes. Comparison of the observed fundamental vibrational frequencies of glycylglycine and calculated results by density functional B3LYP and Hartree-Fock (HF) methods indicates that B3LYP is superior to the scaled Hartree-Fock (HF) for molecular vibrational issues.
authors.affiliation: College of Chemistry, Qufu Normal University, Shandong, Qufu 273165, PR China. bzhaochem@hotmail.com
authors.forename: Bin
authors.initials: B
authors.lastname: Zhao
authors.forename: Chun
authors.initials: C
authors.lastname: Wang
authors.forename: Shulei
authors.initials: S
authors.lastname: Zhao
authors.forename: Mei
authors.initials: M
authors.lastname: Qin
authors.forename: Zhengyu
authors.initials: Z
authors.lastname: Zhou
authors.forename: Yuxi
authors.initials: Y
authors.lastname: Sun
mesh_terms: D018360:Crystallography, X-Ray; D006033:Glycylglycine / Q000737:chemistry*; D006860:Hydrogen Bonding; D008956:Models, Chemical; D008968:Molecular Conformation; D013055:Spectrophotometry, Infrared; D014732:Vibration
chemical_list: D006033:Glycylglycine