Mk. Shukla et Pc. Mishra, EXCITED-STATE MOLECULAR ELECTRIC PROPERTIES OF SOME BIOLOGICALLY IMPORTANT PURINES, PYRIMIDINES, AND AZINES - AN AB-INITIO STUDY, Journal of chemical information and computer sciences, 38(4), 1998, pp. 678-684
Citations number
40
Categorie Soggetti
Computer Science Interdisciplinary Applications","Computer Science Information Systems","Computer Science Interdisciplinary Applications",Chemistry,"Computer Science Information Systems
Electronic charge distributions and molecular electrostatic potentials
(MEP) in the ground and lowest singlet pi-pi and n-pi* excited state
s of certain azines, biologically important pyrimidines, and purines w
ere studied using ab initio calculations where excited-state wave func
tions were generated using configuration interaction involving singly
excited configurations (CIS). Further, these results were obtained by
optimizing ground- and excited-state geometries of the molecules, and
the 3-21G basis set was used. The MEP-fitted atomic point charges were
obtained using the CHelpG procedure, and these charges were then dist
ributed in three dimensions the forms of the squares of the correspond
ing valence Slater ns (n = principal quantum number) atomic orbitals.
It is found that while pi-pi excited-state charges and MEP patterns a
re usually not too different from those of the ground states, the corr
esponding patterns in the n-pi excited states are drastically differe
nt. The charge redistributions in the azines following their n-pi exc
itations appear to follow an ortho, para directing effect. The compute
d dipole moment changes following excitations of the molecules are in
satisfactory agreement with experiment.