Azomethines (-N=C-) are highly attractive alternatives to currently used conjugated materials. This is due in part to their isoelectronic character relative to their carbon analogues. They are further advantageous because of their simple synthesis without the use of stringent reaction conditions or metal catalysts. They are easily purified, unlike their carbon analogues, and also exhibit high chemical and reductive resistance. The limited number of stable diamino monomer precursors has unfortunately hindered the development of functional materials incorporating azomethines. The 3,4-diethyl ester 2,5-diaminothiophene (1) is an ideal precursor for novel conjugated azomethines.6 In addition to consisting of a thiophene moiety, which is highly desired because of its low oxidation potential, 1 also exhibits a high stability. This is in contrast to its unsubstituted analogue that cannot be isolated and spontaneously decomposes under ambient conditions. Since thiophenes have gained a wide importance because of their spectroscopic and electrochemical properties, azomethines derived from them would therefore possess ideal properties and be suitable for functional materials. The synthesis and characterization of unprecedented thiopheno azomethines derived from diaminothiophene are examined for selective product formation. A one-pot modular synthesis of symmetric and unsymmetric conjugated azomethines consisting of up to five thiophenes is investigated. The resulting photophysical, electrochemical, and band-gap properties, in addition to crystallographic data of these unique and highly conjugated thiopheno azomethines are also presented.
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