Theoretical investigations on the conformation of 1,5,N(4),N(4)-tetramethylcytosine.

Theoretical investigations (Perturbative Configuration Interaction over Localized Orbitals (PCILO) and Intermediate Neglect of Differential Overlap (INDO) methods) of the conformation of tetramethylcystosine, an overcrowded molecule with planar structure, have been carried out. The physical features of rotational bending potentials of the dimethylamino group are discussed. Particularly, the controversial problem concerning the planarity of the molecule is investigated. The obtained results show that the planarity of tetramethylcytosine is an intrinsic property of the molecule. Nevertheless, because of the repulsion between the methyl groups, the planar structure of tetramethylcytosine is slightly destabilized. Further, the functional dependence of the dipole moment of tetramethylcytosine on rotation and bending of the dimethylamino group has been analyzed.