Photoelectron spectrum and quantum chemical analysis of the structure of bis(1,3,6-trimethyluracilyl-5)methane

Photoelectron spectra of bis(1,3,6-trimethyluracilyl-5)methane (I) and 1,3,6-trimethyluracil (II) were studied; AM1 optimization of geometric characteristics was carried out. The total energy minimum and the best agreement between the values of IP_m and -ɛ_m were obtained for conformations with nearly orthogonal location of uracilyl fragments. In such conformations, the highest occupied orbitals are pseudodegenerate. To interpret the photoelectron spectra, we employed ab initio calculations in STO-3G and 4-31G basis sets. For uracil and its derivatives, all methods give the π, π, n⁻, n⁺, π sequence of the highest orbitals. A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center, Russian Academy of Sciences. Translated fromZhurnal Struktumoi Khimii, Vol. 36, No. 1, pp. 102–107, January–February, 1995. Translated by L. Smolina