Photoelectron spectroscopic and density functional theoretical studies of the 2′-deoxycytidine homodimer radical anion

The intact (parent) 2′-deoxycytidine homodimer anion, (dC)2•−, was generated in the gas phase (in vacuo) using an infrared desorption/photoemission source and its photoelectron spectrum was recorded using a pulsed, magnetic bottle photoelectron spectrometer. The photoelectron spectrum (PES) revealed a broad peak with the maximum at an electron binding energy between 1.6 and 1.9 eV and with a threshold at ∼1.2 eV. The relative energies and vertical detachment energies of possible anion radicals were calculated at the B3LYP/6-31++G** level of theory. The most stable anion radicals are the complexes involving combinations of the sugar···base and base···base interactions. The calculated adiabatic electron affinities and vertical detachment energies of the most stable (dC)2•− anions agree with the experimental values. In contrast with previous experimental-computational studies on the anionic complexes involving nucleobases with various proton-donors, the electron-induced proton transferred structures of (dC)2...