Theoretical studies on the properties of tropolone and tropolone-X (XÂ =Â HF, H2O, NH3) complexes in the ground and excited states

The S0 and S1 geometries, vibrational frequencies, binding energies, intramolecular proton transfer reactions of Tropolone and Tropolone-X (X = HF, H2O, NH3) complexes, were investigated comprehensively at B3LYP and CASSCF theoretical levels. The geometry and NBO analysis indicates that the first excited states of Tropolone and Tropolone-X (X = HF, H2O, NH3) complexes come from π → π∗ transitions. Frequency discussion indicates that the formation of the complexes has considerable influence on O-H structure of Tropolone in the ground state, while significant influence on CO was found in S1 state. Stronger hydrogen bond interaction in Tropolone-HF than those in Tropolone-H2O and Tropolone-NH3 was found from the H-bond stabilization energy computations. The proton transfer results indicate that the proton transfer reactions are concerted reactions through cyclic transition states. In the ground state, the existing of HF makes for the proton transfer reaction, but H2O and NH3 decrease the proton transfer reaction rate. HF, H2O, NH3 complexing to Tropolone contributes to the proton transfer in the first excited state.