Mesomorphic Substances Containing Some Group IV Elements

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Abstract
A unique series of organometallic substances has been prepared from 4′-methoxy-4-aminobiphenyl and para-substituted benzaldehydes. Among the substituents investigated are trimethylsilyl, trimethylgermyl, trimethyltin, trimethylsiloxy, and pentamethyldisiloxanyl. The compounds were examined for mesomorphic behavior, and the heats and entropies of the mesophase transitions were determined by differential scanning calorimetry. A majority of these compounds exhibit either a smectic or a nematic mesophase, although analogous organometallic anils derived from p-aminophenyl acetate or p-aminophenyl benzoate are non-mesomorphic. The results, taken together with data obtained from carbon-containing “isologs,” indicate that the bulkiness associated with the organometallic substituent does not preclude liquid crystal formation in long molecules, especially when the electronic properties of the end groups, such as high polarizability and mesomeric interactions, are beneficial.