Packing modes in crystals of mesogenic biphenyl esters with normal alkyl and/or alkoxy chains

Crystal structures determined for eight compounds R-C6H4-C6H4-COO-C6H4-R', where R and R' are achiral, four with octyloxy and/or octyl chains and four with a methyl or methoxy group at one end, are classified into three modes . First is a smectic-like layer composed of parallel molecules with closely arranged ester linkages; second is a layer comprising two crystallographic ally independent molecules, among which the ester linkages are close. Compo unds with an octyloxy chain take these modes. Thirdly, for molecules with a lkyl chains, the ester linkages are far apart among the parallel molecules. Melting and clearing points suggest stronger intermolecular interactions i n the former two modes than in the last mode.