Abstract: The structures of the H3PAuPh and (H3PAu)2(1,4-C6H4)2 are optimized using the density functional theory for the ground states. The lowest-energy absorption spectra are calculated by the time-dependent density functional theory，and it is found that the 257.5nm line arises from 1A＇→1A＇ transition for H3PAuPh and the 307.6nm line arises from 1A→1A transition for (H3PAu)2(1,4-C6H4)2. The lowest-energy absorption spectra of the Au complexes have the nature of pπ(aromatic_nucleus)→pπ*(aromatic_nucleus)C(2p)→Au(6p) charge transfer which is accompanied by Au(5d)→Au(6p) transition character. The (H3PAu)2(1,4-C6H4)2 is approximately made up of double H3PAuPh. So the molecular orbitals of (H3PAu)2(1,4-C6H4)2 can be regarded as the compounding of the molecular orbitals of H3PAuPh. The compounding of the molecular orbitals with the reciprocities of pπ* or pπ makes the lowest-energy absorption energy of (H3PAu)2(1,4-C6H4)2 lower than that of H3PAuPh.

Keywords: 
• excited state /
• spectral /
• density functional theory /
• AuPH3K2