A series of large molecular quadratic hyperpolarizabilities in donor/acceptor substituted trans-tetraammineruthenium(II) complexes [Ru(NH_3)_4L~DL~A]~(n+) (n = 2, L~D = 4-(dimethylamino)pyridine, L~A = 4-pyridinecarboxaldehyde (1), 4-acetylpyridine (2), ethyl isonicotinate (3), or n = 3, L~A = N-methyl-4,4'-bipyridinium (4), N- (4-acetylphenyl)-4,4'-bipyridinium (4-AcPhQ~+) (5), and n = 3, L~D = NH_3, L~A = (4-AcPhQ~+) (6) has been studied by using the TDDFT and ab initio HF method. It is found that the magnitude of the static hyperpolarizabilities β_0 increases as the donor/accepter strength of L~D/L~A increases. The co-planes of pyridine or benzene ring are not necessary to maintain the large nonlinear optic properties. According to our study on Ru complexes, TDDFT method is more reliable than HF method in β-calculation.

Key words: RUTHENIUM COMPLEX, NON LINEAR OPTICS, AB INITIO CALCULATION