Competing forces in the self-assembly of amide-functionalized discotic mesogens.

The effect of incorporating a single amide group on the self-assembly of discotic mesogens was examined. Two series of tetraalkoxydibenzophenazines amides were prepared: tertiary diethyl amides, dEt(n) incapable of hydrogen bonding, and secondary amides HBu(n) that can act as both H-bond donors and acceptors. These compounds exhibit markedly different behavior in solution; NMR studies of dEt(n) show no evidence of self-association, whereas HBu(n) strongly associate via H-bonding and π-stacking.

Pi-Extended Ethynyl 21,23-Dithiaporphyrins: A Synthesis and Comparative Study of Electrochemical, Optical, and Self-Assembling Properties.

21,23-Dithiaporphyrins were synthesized containing pi-extending ethynyl substituents at the meso positions. These porphyrins displayed highly bathochromic and broadened absorbance profiles spanning 400-900 nm with molar absorptivities ranging from 2500 to 300,000 M(-1) cm(-1). Electrochemically, these ethynyl dithiaporphyrins undergo a single oxidation at 0.

Liquid Crystalline Esters of Dibenzophenazines.

A series of esters of 2,3,6,7-tetrakis(hexyloxy)dibenzo[,]phenazine-11-carboxylic acid was prepared in order to probe the effects of the ester groups on the liquid crystalline behavior. These compounds exhibit columnar hexagonal phases over broad temperature ranges. Variations in chain length, branching, terminal groups, and the presence of cyclic groups were found to modify transition temperatures without substantially destabilizing the mesophase range.

Synthesis and mesomorphic properties of novel dibenz[a,c]anthracenedicarboximides.

The synthesis and characterization of a novel series of dibenz[a,c]anthracenedicarboximides is reported. Incorporating electron-withdrawing imides bearing flexible alkyl chains allowed for the production of materials that self-assemble into hexagonal columnar mesophases featuring broad temperature ranges. Furthermore, longer N-alkyl chains or branched N-alkyl chains broaden the mesophase temperature range by lowering the melting transition without greatly influencing the clearing point.

Folded discotic dimers.

We report the synthesis and properties of a dibenzophenazine discotic dimer, which was found to adopt a folded conformation in solution. This stable π-stacked structure persists at elevated temperatures and in all solvents examined. Folding allows the dimer to assemble into a columnar liquid crystal phase, despite its short linking group.