부산대학교 도서관

The electronically excited states of formaldehyde and its complexes with alkali metal ions are investigated with the time-dependent density functional theory (TD DFT) method. Vertical transition energies for several singlet and triplet excited states, adiabatic transition energies for the first singlet and triplet excited states S1 and T1, the adiabatic geometries and vibrational frequencies of the ground state S0 and the first singlet and triplet excited states S1 and T1 for formaldehyde and its complexes are calculated. Better agreement with the experiment than that of the CIS method is obtained for CH2O at the TD DFT level. The nonlinear C=O⋯M+ interaction in the excited states S1 and T1 is weaker than the linear interaction in the ground state. In the S0 and S1 states, the C=O bond is elongated by cation complexation and its stretching frequency is red-shifted, but in the T1 state the C=O bond is shortened and its frequency is blue-shifted. [ABSTRACT FROM AUTHOR]