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Synthesis and Optical and Electronic Properties of Thiophene Derivatives
Author(s) -
Jimenez Raphael P.,
Parvez Masood,
Sutherland Todd C.,
Viccars Joel
Publication year - 2009
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200900850
Subject(s) - thiophene , chemistry , homo/lumo , substituent , cyclic voltammetry , knoevenagel condensation , malononitrile , photochemistry , absorption spectroscopy , density functional theory , electrochemistry , computational chemistry , organic chemistry , molecule , catalysis , electrode , physics , quantum mechanics
Using the Hinsberg synthesis of thiophenes, a versatile method to prepare fully derivatized, π‐extended thiophenes is reported. Functionalized thiophenes were divergently synthesized to create three classes of compounds – electron‐deficient, extended conjugation and electron‐rich – to assess substituent effects on optical and electrochemical properties. Properties were assessed by solution absorption spectroscopy, solution‐ and solid‐state fluorescence spectroscopy, cyclic voltammetry and density functional theory calculations. Tetracyano derivatives, prepared through Knoevenagel condensations of malononitrile with thiophene‐2,5‐dicarbaldehydes, were used as electron‐poor analogs. These derivatives showed quasireversible reduction reactions and very low‐lying calculated LUMO energies (–0.55 V reduction potentials vs. Fc/Fc + ). The effect of extending π conjugation on the optical and electrochemical properties was investigated by the installation of bis(2‐thienylacryonitrile) groups onto three thiophene cores. The extended conjugation led to compounds that demonstrated both solution‐ and solid‐state fluorescence and moderate, irreversible reduction potentials (–1.2 V versus Fc/Fc + ). The Lewis‐acid‐catalyzed coupling of four indoles to thiophene‐2,5‐dicarbaldehydes was studied to assess the effects of both electron‐donating substituents and a quinoidal thiophene. The tetraindolic thiophenes possessed low HOMO–LUMO energy gaps of 1.91 eV, high‐lying HOMO energy levels and tunable LUMO energy levels, attributed to the thiophene quinoidal ground‐state structure. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)