Preparation and characterization of novel azomethine comonomers prepared from conjugated aminothiophene comonomers

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Conjugated materials have gained a wide importance because of their physical properties making them ideal for emitting devices and plastic electronics. Among the most attractive properties are their low oxidation potentials and photo- and electrochemically excited states affording suitable emissions for electronic devices. Unfortunately, the preparation of these desired materials requires stringent reaction conditions using metal catalysts that are problematic to remove. Furthermore, the coupling methods used to prepare such materials lead to inconsistent products with unreliable properties. Azomethines (-N=C-) comonomers are ideal alternatives because they are easily formed without stringent reaction conditions with consistent product formation. When using aryl precursors, the resulting bond is hydrolytically, reductively, and oxidatively resistant. What is proposed is the synthesis of novel comonomers containing 2 or 3 covalently linked thiophenes containing terminal amines. This affords amino bithiophene and terthiophene derivatives that can be condensed with various aromatic aldehydes affording highly conjugated compounds. Given the importance of thiophene as a precursor for conjugated polymers, the synthesis of 2,2'-diaminoterthiophene is proposed using the Gewald reaction starting from 2,5-thiophene carbaldehyde. The well established substitution chemistry of thiophene is proposed to synthesize various 2,2'-diaminoterthiophene derivatives. Various electron donors and withdrawing groups can be easily incorporated into the 3 and 4 positions allowing the fine tuning of the physical properties in addition to increasing the solubility. The condensation of the various precursors with fluorene and thiophene dialdehydes will be pursued. The resulting physical properties including the redox potentials, fluorescence quantum yields, the excited state lifetimes, anodic electropolymerization, and spectroelectrochemistry are proposed.