METHYLATION REDUCES ELECTRON-AFFINITY OF URACIL - AB-INITIO THEORETICAL-STUDY

Following the experimental characterization of the N,N-dimethylated ur acil anion by Bowen and co-workers, we have undertaken an investigatio n of the influence of the methylation on the electron affinity of the uracil molecule. Both experiment and theory agree that, as it is in th e case of the isolated uracil molecule, the methylated uracils can onl y attach excess electrons into diffuse dipole-bound states. The corres ponding electron affinities are very small (several MeV). The bonding effect in the dipole-bound state depends on the magnitude of the molec ular dipole and on the size of the molecule. Selective methylation of the uracil molecule can be used to reduce or increase the dipole value and to change the electron affinity of the molecule. The present calc ulated results are consistent with the experimental determination that N,N-dimethylation of uracil results in reduction of the electron affi nity.