Abstract: In order to develop a novel class of low molecular weight organic gels and to gain an insight into the relationship between molecular structure of gel forming compounds and gel forming properties, a novel family of low molecular weight organic compounds containing terthiophene and tetrathiophene, N, N'-dialkyl-5, 5" (2, 2":5, 2"-tetrathiophene)dicarboxamide(DNC₁₈3T), N, N'-dialkyl-5, 5" (3, 3" dioctyl 2, 2":5, 2"-tetrathiophene) dicarboxamide(DNC_n DOc3T, n=5, 8, 16, 18) and N, N'-dialkyl-5, 5" (3, 3dioctyl 2, 2":5, 2":5", 2"-tetrathiophene) dicarboxamide(DNC₁₈ DOc4T), were designed and synthesized. Whereas DNC₁₈ 3Tand DNC₅DOc3Tdid not form gels with organic solvents, DNC_n DOc3T (n=8, 16, 18) and DNC₁₈ DOc4Twere found to form gels with certain organic solvents. These are the first examples of low molecular weight organic gels containing an oligothiophene moiety. It is of interest to note that while DNC₈DOc3Tforms opaque gels with alcohols, such as ethanol and isopropanol, DNC₁₆ DOc3T, DNC₁₈ DOc3Tand DNC₁₈ DOc4Tformed transparent gels with hydrocarbon solvents such as heptane, octane, undecane, and others. It is shown that the intermolecular hydrogen bonding and intermolecular interaction between the long alkyl chain in the Nalkylcarboxamide group as well as the incorporation of an alkyl group at the β position of the thiophene ring play an important role for the formation of gels. The xerogel showed three dimensional networks of fibrous bundle structure. DNC₁₈ DOc3T/benzonitrile gel and DNC₁₈ DOc4T/benzonitrile gel were found to function as a new type of electrochromic materials, exhibiting a reversible color changes on electrochemical oxidation and reduction.

Key words: Low molecular weight organic gel, Terthiophene, Tetrathiophene, Intermolecular hydrogen bonding, Three dimensional network, Electrochromism