Extended dipolar nonlinear optical chromophores based on trans-bis[1,2-phenylenebis(dimethylarsine)]chlororuthenium(II) centers

Coe, Benjamin J., Harries, Josephine L., Harris, James A., Brunschwig, Bruce S., Horton, Peter N. and Hursthouse, Michael B. (2006) Extended dipolar nonlinear optical chromophores based on trans-bis[1,2-phenylenebis(dimethylarsine)]chlororuthenium(II) centers. Inorganic Chemistry, 45 (26), 11019-11029. (doi:10.1021/ic061659u).

Abstract

Four new complex salts trans-[(RuCl)-Cl-II(pdma)(2)L-A][PF6](n) [pdma = 1,2-phenylenebis(dimethylarsine); L-A =1,4-bis[E-2-(4-pyridyl)ethenyl]benzene (bpvb), n = 1, 1; L-A = N-methyl-1,4-bis(E-2-(4-pyridyl)ethenyl)benzene (Mebpvb(+)), n = 2, 2; L-A = N-phenyl-1,4-bis(E-2-(4-pyridyl)ethenyl)benzene (Phbpvb(+)), n = 2, 3; L-A = N-(2-pyrimidyl)-1,4-bis(E-2-(4-pyridyl) ethenyl) benzene (Pymbpvb(+)), n) 2, 4] have been prepared. The electronic absorption spectra of 1-4 display intense, visible metal-to-ligand charge-transfer (MLCT) bands, with lambda(max) values in the range 432-474 nm in acetonitrile. Intense intraligand charge-transfer (ILCT) bands due to LA are also observed, with lambda(max) values in the range 350-416 nm. Cyclic voltammetric studies in acetonitrile reveal reversible Ru-III/II waves with E-1/2 values of ca. 1.05 V vs Ag/AgCl, together with L-A-based reduction processes that are irreversible with the exception of 1. Salts 1-4 have been investigated by using Stark (electroabsorption) spectroscopy in butyronitrile glasses at 77 K. These studies have afforded dipole moment changes, Delta mu(12), for the MLCT and ILCT transitions which have been used to calculate molecular static first hyperpolarizabilities, beta(0), according to the two-state equation, beta(0) = 3 Delta mu(12)-(mu(12))(2)/(E-max)(2) (mu(12) = transition dipole moment, E-max = MLCT/ILCT energy). In contrast with related Ru-II ammine complexes, replacement of a central E-ethylene bond with a 1,4-phenylene unit does not appear to be an especially effective strategy for combating the NLO transparency-efficiency tradeoff in these pdma complexes. Single-crystal X-ray studies with the complex salts 2 and 3 and also with the pro-ligand salt [Phbpvb(+)]PF6(.)0.5HPF(6) show that these materials all adopt centrosymmetric packing structures.

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Contributors

Author: Peter N. Horton

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