Pentacyanoiron(II) as an electron donor group for nonlinear optics: Medium-responsive properties and comparisons with related pentaammineruthenium(II) complexes

Benjamin J. Coe, Josephine L. Harries, Madeleine Helliwell, Lathe A. Jones, Inge Asselberghs, Koen Clays, Bruce S. Brunschwig, James A. Harris, Javier Garin, Jesus Orduna

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    Abstract

    In this article, we describe a series of complex salts in which electron-rich {FeII(CN)5}3- centers are coordinated to pyridyl ligands with electron-accepting N-methyl/aryl-pyridinium substituents. These compounds have been characterized by using various techniques including electronic absorption spectroscopy and cyclic voltammetry. Molecular quadratic nonlinear optical (NLO) responses have been determined by using hyper-Rayleigh scattering (HRS) at 1064 nm, and also via Stark (electroabsorption) spectroscopic studies on the intense, visible d → π* metal-to-ligand charge-transfer (MLCT) bands. The relatively large static first hyperpolarizabilities, β0, increase markedly on moving from aqueous to methanol solutions, accompanied by large red-shifts in the MLCT transitions. Acidification of aqueous solutions allows reversible switching of the linear and NLO properties, as shown via both HRS and Stark experiments. Time-dependent density functional theory and finite field calculations using a polarizable continuum model yield relatively good agreement with the experimental results and confirm the large decrease in β0 on protonation. The Stark-derived β0 values are generally larger for related {RuII(NH3) 5}2+ complexes than for their {FeII(CN) 5}3- analogues, consistent with the HRS data in water. However, the HRS data in methanol show that the stronger solvatochromism of the FeII complexes causes their NLO responses to surpass those of their RuII counterparts upon changing the solvent medium. © 2006 American Chemical Society.
    Original languageEnglish
    Pages (from-to)12192-12204
    Number of pages12
    JournalJournal of the American Chemical Society
    Volume128
    Issue number37
    DOIs
    Publication statusPublished - 20 Sept 2006

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