Theoretical studies of the unimolecular and bimolecular tautomerization of cytosineElectronic supplementary information (ESI) available: tables of MP2(full)/6-31G* optimized geometries, rotational constants, and scaled vibrational frequencies for isolated monomers of the six low-energy tautomers of cytosine and corresponding transition states for unimolecular tautomerization; B3LYP/6-31G* optimized geometries, rotational constants, and scaled vibrational frequencies for six cytosine dimers and corresponding transition states for bimolecular tautomerization. See http://www.rsc.org/suppdata/cp/b3/b315089e/