title: Synthesis and photophysics of thioindigo diimines and related compounds.
abstract: We report the synthesis and comprehensive characterization of diamine and diimine derivatives of the fluorescent compound thioindigo. Diamines 1 were obtained by metal-mediated amine condensation reaction with thioindigo. Oxidation of the products of the coupling reaction provided the diimines 2. X-ray crystal structures, cyclic voltammetry, and spectral and photophysical data of the compounds are presented. X-ray crystal structures demonstrate a planar structure for the diimine derivatives and a twisted conformation for the diamines. The diamine compounds 1 absorb in the UV (λmax 324-328 nm), significantly blue-shifted from the absorption spectrum of thioindigo. Diamines 1 exhibit moderate fluorescence (ΦF = 0.25, 0.045). A transient triplet state is observed in laser flash photolysis (LFP) experiments of 1, with lifetimes 1 order of magnitude longer than those of thioindigo. The diimine compounds 2 absorb at longer wavelengths (λmax 495-510 nm) than the diamines but are still slightly blue-shifted from thioindigo, with molar extinction coefficients 17-70% higher compared to thioindigo. The diimine compounds are not emissive, and LFP studies indicate transient species with microsecond lifetimes. Quenching experiments and transient absorption spectra are consistent with trans-cis isomerization.
authors.affiliation: Department of Chemistry, University of Victoria , P.O. Box 3065 STN CSC, Victoria, BC V8W 3V6, Canada.
authors.forename: Geneviève
authors.initials: G
authors.lastname: Boice
authors.forename: Brian O
authors.initials: BO
authors.lastname: Patrick
authors.forename: Robert
authors.initials: R
authors.lastname: McDonald
authors.forename: Cornelia
authors.initials: C
authors.lastname: Bohne
authors.forename: Robin
authors.initials: R
authors.lastname: Hicks