Some square-planar phenyl metal complexes [XM(PEt₃)₂-C₆H₄-R] (M＝Pd, Pt, X＝Br, I, R＝NO₂, CHO) were reported to possess rather large hyperpolarizabilities. This series of complexes have been studied by ab initio method. An extending Lanl2DZ basis set was used in calculations, which is augmented with one diffuse function in each shell with their exponents determined from the even-tempered sequences. Only one polarization function has been augmented for each atom and its exponent determined from the exponents of most two diffuse functions of outermost occupied shell of the definite atom, the square root of their product. According to our RHF/extending-Lanl2DZ calculations, the trans influence of X was more evident with the bromo ligand than iodo ligand for β. The importance of electrowithdrawing substituent R was also evident, and β values were found to be increased with electrowithdrawing strength, leading to the higher values of the nitro derivatives.

Key words: metal complex, hyperpolarizability, basis set, ab initio