Ground and excited states of naphthalene-water (naphtha-W-6) clusters: a computational study

An MP2 and DFT study of the structures of naphthalene-water hexamer clusters has been performed for both the prism and cage forms of the cluster. These have been corrected for zero-point energy and counterpoise effects and show a larger binding energy for the prism structures. These have been analysed in terms of the number and type of hydrogen-bonding interactions present. We have also performed time-dependent DFT computations of the electronic excited states with a variety of functionals. Our results show good agreement between TD-CAM-B3LYP and TD-M06-2X, and predict that the presence of the water cluster red-shifts and lowers the intensity of the primary pi -> pi* transition. This effect is more pronounced in the prism than the cage cluster. We also calculate weaker higher energy features involving charge transfer from the naphthalene to the water cluster.