Interplay of intrinsic and environmental effects on the magnetic properties of free radicals issuing from H-atom addition to cytosine

Possible radical reaction products issuing from II-atom addition to cytosin e have been characterized and analyzed by means of a comprehensive quantum mechanical approach including density functional computations (B3LYP), toge ther with simulation of the solvent by the polarizable continuum model (PCM ), and averaging of spectroscopic properties over the most important vibrat ional motions. The hyperfine couplings of the semirigid 5,6-dihydrocytos-6y l radical computed at the optimized geometry are in good agreement with the ir experimental counterparts. On the other hand, vibrational averaging is m andatory for obtaining an effectively planar structure for the 5,6-dihydroc ytos-5yl radical with the consequent equivalence of beta -hydrogens. Finall y, only proper consideration of environmental effects restores the agreemen t between computed and experimental couplings for the base anion protonated at N3.