The ground states and excitation states of 1-methylamideanthraquinone (MAAQ) are studied by using density functional theory (DFT) combined with time-dependent density functional theory. In the S0 state of MAAQ, amide group is coplanar with anthraquinone, and an intramolecular hydrogen bond C=O???H-N is formed. The S0→S1 transition belongs to π→π*. Two stable structures (planar nMAAQ and twisted tMAAQ) have been obtained in the S1 state of MAAQ, nMAAQ is the dominant conformation in the S1 state of MAAQ and the emission spectra of tMAAQ is not observed in the solution of MAAQ. In the S1 state, twisted intramolecular charge transfer (TICT) process occurs in MAAQ. An intermolecular hydrogen bond F???H-N is formed in the S0 state, and ESIPT happens in the S1 state for MAAQ-F-.
