Atropoisomeric aromatic cores enhance disorder inside the supramolecular packing of disk‐shaped mesogens. Core‐extension of perylene with an atropoisomeric [4]helicene fragment thus gives rise to a room‐temperature liquid crystal even with extremely short side chains. Replacement of diester moieties by imide substituents allows switching from donor‐ to acceptor‐type electronic characteristics.
Five-coordinate
geometry is the standard binding mode of zinc porphyrins
with pyridine ligands. Here we show that pseudo-octahedral six-coordinate
zinc porphyrin complexes can also be formed in solution, by taking
advantage of the chelate effect. UV–vis–NIR titrations
indicate that the strength of this second coordination is ca. 6–8
kJ mol–1. We have used the formation of six-coordinate
zinc porphyrin complexes to achieve the template-directed synthesis
of a 3D π-conjugated spiro-fused array of 11 porphyrin units,
covalently connected in a nontrivial topology. Time-resolved fluorescence
anisotropy experiments show that electronic excitation delocalizes
between the two perpendicular nanorings of this spiro-system within
the experimental time-resolution of 270 fs.
Benzo[ghi]perylene 1,2,4,5,10,11-hexacarboxylic trialkylimide and dialkylimido-dialkyl ester derivatives, displaying a thermodynamically stable hexagonal columnar liquid-crystalline phase at room temperature, have been obtained by the use of previously unexplored chiral racemic α-branched alkylimide functions. One of the trialkylimides described here is the first room temperature columnar solely oligo-alkylimide-substituted arene, and thus constitutes a prototype case of self-assembling organic acceptor materials. As the related hexacarboxylic hexaesters are found to exhibit only a weak tendency to form columnar mesophases, benzo[ghi]perylene 1,2,5,10-tetracarboxylic tetraalkyl esters have been synthesized by regioselective oxidative Diels-Alder addition of maleic anhydride to 3,10-dicyanoperylene, and a room temperature hexagonal columnar mesophase was obtained with branched alkyl chains. The acceptor-type electronic properties of the tri- and diimides have been found to be considerably more pronounced than those of the hexa- and tetracarboxylic esters, and to approach those of the prototype acceptor material C(60). The formation of bathochromically absorbing donor-acceptor complexes was observed with a di- or triimide as acceptor and a tetraester as donor, but not with a hexaester as donor. Exploiting the non-negligible differences in reduction and oxidation potentials between all four types of materials, the minimum HOMO energy difference necessary for charge-transfer-complex formation has been determined to lie between 0.29 and 0.35 eV.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.