Study On Molecular Geometry And Nonlinear Optical Property Of Metal Organic Complexes

Geometries structures and nonlinear optical property of metal organic complexes were studied by theory computation. Molecular structures were optimized at B3LYP/6-31+G(d) level, and on this basis, computed UV-VIS spectra were consistent with experimental results, and nonlinear optical property were calculated using the finite field method.For two Ir complexes, the lowest energy absorption peaks were at 540 and 546 nm, coincided with the experimental results. The analysis results of frontier molecular orbits indicated charge transition of similar types and mixed electronic transition of LC(transition within the ligand), LLCT( transition from ligand to another ligand) and MLCT(transition from metal to the ligand). The obtained nonlinear optical property at B3LYP/6-31++G(d,p) level showed that the second nonlinear optical property β were-3625.2 and-2586.5 a.u., and the third nonlinear optical property γ were 439510 and 404930 a.u., respectively.For two Pd complexes, the lowest energy absorption peaks were at 300 and 297 nm, which was not obvious and corresponding absorption peaks of about 260 nm on the experimental spectrum. The other absorption peaks were coincided with experimental results. According to the analysis of frontier molecular orbits, there existed LC, LLCT, MLCT, and electronic transition of HOMO to LUMO was from the acetylacetone ligand and metal atom to the pyridine ligand. There were obvious LC charge transfer with the transition of LUMO to HOMO+3, and the introducing of iodine atom enhanced this transition. Our calculated results showed that the values of β were 1351.8 and 917.1 a.u., and the values of γ were 132590 and 152100 a.u., respectively.The lowest energy absorption peaks of four 8-hydroxyquinoline ramification Ag complexes were at 1000 nm, which were contribution of transition from HOMO to LUMO, and that cannot be observed in absorption spectrum for the extremely small transition oscillation. So we considered the peaks of about 540 nm as the lowest energy absorption peaks. There were alike geometry and charge transfer type of MLCT, and so this five complexes had alike UV-VIS spectra and similar nonlinear optical property. We compared the four complexes with the 8-hydroxyquinoline Ag metal complex(Ag Q), the values of β had smaller than that of Ag Q, but the values of γ were five times to Ag Q, which was about 5×105 a.u..Three geometries were found for five 8-hydroxyquinoline ramification Zn complexes(Zn R1, Zn R5, Zn R9, Zn R11, Zn R13), and the lowest energy absorption peaks of the five complexes were at about 500 nm. The increase of ramification carbon chain did not change position of the lowest energy absorption peaks, and the Zn R5 or Zn R9 had the biggest nonlinear optical property for large absorption intensity. The values of γ were increased significantly with the increase of ramification carbon chain, which was about 6~12×105 a.u..