Molecular quadratic non-linear optical properties of dipolar trans-tetraammineruthenium(ii) complexes with pyridinium and thiocyanate ligands.

Benjamin J. Coe, Lathe A. Jones, James A. Harris, Emma E. Sanderson, Bruce S. Brunschwig, Inge Asselberghs, Koen Clays, Andre Persoons

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Seven new complex salts trans-[RuII(NCS)(NH3)4(LA)][PF6]2 [LA = N-methyl-4,4'-bipyridinium (MeQ+) 1, N-methyl-2,7-diazapyrenium (Medap+) 2, N-methyl-4-[trans-2-(4-pyridyl)ethenyl]pyridinium (Mebpe+) 3, N-phenyl-4,4'-bipyridinium (PhQ+) 4, N-phenyl-4-[trans-2-(4-pyridyl)ethenyl]pyridinium (Phbpe+) 5, N-(4-acetylphenyl)-4,4'-bipyridinium (4-AcPhQ+) 6, or N-(2-pyrimidyl)-4,4'-bipyridinium (2-PymQ+)7] have been prepd. The electronic absorption spectra of 1-7 display intense, visible metal-to-ligand charge-transfer (MLCT) bands, the energies (Emax) of which decrease in the order 2 > 1 > 3 > 4 > 6 > 5 > 7, as the electron-accepting ability of LA increases. The Emax values generally correlate with cyclic voltammetric and 1H NMR data. Comparisons of the MLCT absorption and electrochem. data for 1-7 show that a trans-{RuII(NCS)(NH3)4}+ center is a stronger electron donor than analogous groups contg. only neutral ligands. Mol. first hyperpolarizabilities .beta. have been measured by using the hyper-Rayleigh scattering technique with acetonitrile solns. and a 1064 nm laser, and static first hyperpolarizabilities .beta.0[H] were obtained by application of the two-state model. Stark (electroabsorption) spectroscopic studies in butyronitrile glasses at 77 K have afforded dipole moment changes .DELTA..mu.12 for the MLCT transitions which have been used to calc. .beta.0[S] values according to the two-state equation .beta.0 = 3.DELTA..mu.12(.mu.12)2/(Emax)2 (.mu.12 = transition dipole moment). Both the .beta.0[H] and .beta.0[S] data confirm that the increased electron donor ability of a trans-{RuII(NCS)(NH3)4}+ center affords enhanced .beta.0 values, when compared with related complexes contg. the neutral trans ligands NH3, 4-(dimethylamino)pyridine, N-methylimidazole (mim) or pyridine. However, the magnitude of the obsd. .beta.0 increase with respect to the analogous mim complexes varies over a range of ca. 25-120%, depending upon LA. [on SciFinder (R)]
    Original languageEnglish
    Pages (from-to)2335-2341
    JournalDalton Transactions
    DOIs
    Publication statusPublished - 2003

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