Hydration of guanine: Electronic singlet excited states for complexes with 19 and 27 water molecules

Computational investigation on the ground and electronic lowest singlet ππ* excited state (S1(ππ*)) of guanine hydrated by a large number (19 and 27) water molecules are reported and obtained results are compared with those for isolated guanine and the comparatively smaller hydrated complexes. Ground state geometries were optimized at the HF level and Configuration Interaction-Singles (CIS) method was used for excited state geometry optimization utilizing the 6-311G(d,p) basis set. It was found that excited state geometry of guanine is significantly different with each other in the studied complexes. The possible effect of hydration on the excited state dynamics of guanine is also discussed.