COLUMNAR AND NEMATIC PHASES OF NEW MACROD ISCOTIC MATERIALS

The first radially multi(biphenylethinyl) substituted arenes possessin g benzene or naphthalene cycles as molecular centers as well as Pallad ium atoms containing macrocyclic complexes derived from hexaalkoxy sub stituted aldobisimines by cyclopalladation have been synthesized and i nvestigated by physical methods. Most of these flat compounds with mol ecular core diameters greater-than-or-equal-to 24 angstrom and molecul ar weights up to 4000 are novel thermotropic liquid crystals, in part highly unsaturated or metallomesogens in structure, respectively, exhi biting columnar and/or nematic phases. Sterical influences on the meso phase formation of these spacious molecules are discussed as well as i nteresting changes of their properties by variation of their self-orga nization occurring in binary systems. Thus, addition of an electron ac ceptor, for example 2,4,7-trinitrofluorenone, leads to the formation o f charge transfer complexes, mesophase stabilizations or even to induc tions of other mesophases including nematic ones of the N(D) or N(C) t ype. Dissolving such thermotropic columnar mesogens in various organic solvents gives rise to lyomesomorphism; in case of at least one of th e palladomesogens a transition between two different lyotropic nematic phases (N1 and N2) has been observed.