Length-dependent convergence and saturation behavior of electrochemical, linear optical, quadratic nonlinear optical, and cubic nonlinear optical properties of dipolar alkynylruthenium complexes with oligo(phenyleneethynylene) bridges

Bandar Babgi, Luca Rigamonti, Marie P. Cifuentes, T. Christopher Corkery, Michael D. Randles, Torsten Schwich, Simon Petrie, Robert Stranger, Ayele Teshome, Inge Asselberghs, Koen Clays, Marek Samoc, Mark G. Humphrey

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    Abstract

    The syntheses of trans-[Ru{4,4′-C≡CC6H 2[2,5-(OEt)2]C≡CC6H4NO 2}Cl(dppm)2] (19), trans-[Ru{4,4′,4″- C≡CC6H4C≡CC6H2[2,5-(OEt) 2]C≡CC6H4NO2}Cl(dppm) 2] (20), trans-[Ru{4,4′,4″,4‴-C≡CC 6H4C≡CC6H2[2,5-(OEt) 2]C≡CC6H2[2,5-(OEt)2] C≡CC6H4NO2}Cl(dppe)2] (21), trans-[Ru{4,4′,4′,4‴-C≡CC6H 4C≡CC6H2[2,5-(OEt)2] C≡CC6H2[2,5-(OEt)2]C≡CC 6H4NO2}Cl(dppm)2] (22), trans-[Ru{4,4′,4″,4‴-C≡CC6H 4C≡CC6H4C≡CC6H 2[2,5-(OEt)2]C≡CC6H4NO 2}Cl(dppm)2] (23), and trans-[Ru{4,4′,4″, 4‴,4′‴-C≡CC6H4C≡CC 6H4C≡CC6H2[2,5-(OEt) 2]C≡CC6H2[2,5-(OEt)2] C≡CC6H4NO2}Cl(dppm)2] (24) are reported, together with those of precursor alkynes, complexes with the donor-π-bridge-acceptor formulation that affords efficient quadratic and cubic NLO compounds; the identity of 19 was confirmed by a structural study. The electrochemical properties of 19-24 and related complexes with shorter π-bridge ligands were assessed by cyclic voltammetry, and the linear optical, quadratic nonlinear optical, and cubic nonlinear optical properties were assayed by UV-vis-NIR spectroscopy, hyper-Rayleigh scattering studies at 1064 and 1300 nm, and broad spectral range femtosecond Z-scan studies, respectively. The RuII/III oxidation potentials and wavelengths of the optical absorption maxima decrease on π-bridge lengthening, until the tri(phenyleneethynylene) complex is reached, further chain lengthening leaving these parameters invariant; theoretical studies employing time-dependent density functional theory have shed light on this behavior. The quadratic nonlinearity β1064 and two-photon absorption cross-section reach maximal values at this same π-bridge length, a similar saturation behavior that may reflect a common importance of ruthenium-to-alkynyl ligand charge transfer in electronic and optical behavior in these molecules.

    Original languageEnglish
    Pages (from-to)10293-10307
    Number of pages15
    JournalJournal of the American Chemical Society
    Volume131
    Issue number29
    DOIs
    Publication statusPublished - 29 Jul 2009

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