title: Stability and Anharmonic N-H Stretching Frequencies of 1-Methylthymine Dimers: Hydrogen Bonding versus π-Stacking.
abstract: Stability of three hydrogen-bonded and six stacked 1-methylthymine (1 mT) dimers was studied with the DFT-D3 method at various temperatures. It was demonstrated that the stacked dimers are slightly less stable than the hydrogen-bonded counterparts. Existence of T-shaped dimers is addressed. Anharmonic couplings that involve N-H stretching modes of the nine species are studied. Surprisingly, we find that N-H stretching modes of the two 1 mT molecules are significantly coupled in four stacked dimers. The presented results shed light on existence of strong mode couplings between the two N-H stretching modes in stacked aromatic species. Our calculations support the proposal ( J. Phys. Chem. A 2011 , 115 , 9429 - 9439 ) that presence of several dimers is responsible for appearance of wide and structured bands in 1 mT homodimers' jet-cooled spectra above 2900 cm(-1).
authors.affiliation: Faculty of Physical Chemistry, University of Belgrade Studentski trg 12-16, 11 158 Belgrade, Serbia.
authors.forename: Milena
authors.initials: M
authors.lastname: Petković
authors.affiliation: Faculty of Physical Chemistry, University of Belgrade Studentski trg 12-16, 11 158 Belgrade, Serbia.
authors.forename: Miroslav
authors.initials: M
authors.lastname: Ristić
authors.affiliation: Faculty of Physical Chemistry, University of Belgrade Studentski trg 12-16, 11 158 Belgrade, Serbia.
authors.forename: Mihajlo
authors.initials: M
authors.lastname: Etinski
mesh_terms: D019281:Dimerization; D006860:Hydrogen Bonding; D013055:Spectrophotometry, Infrared; D013941:Thymine / Q000031:analogs & derivatives* / Q000737:chemistry
chemical_list: C030630:1-methylthymine; D013941:Thymine