Designing Supramolecular Liquid-Crystalline Hybrids from Pyrenyl-Containing Dendrimers and Arene Ruthenium Metallacycles

摘要

The association of the arene ruthenium metallacycle [Ru_4(p-cymene)_4(bpe)_2(donq)_2][DOS]_4 (bpe = 1,2-bis(4-pyridyl)-ethylene, donq = 5,8-dioxydo-1,4-naphtoquinonato, DOS = dodecyl sulfate) with pyrenyl-functionalized poly(arylester) dendrimers bearing cyanobiphenyl end-groups is reported. The supramolecular dendritic -systems display mesomorphic properties as revealed by polarized optical microscopy, differential scanning calorimetry and small-angle X-ray scattering measurements. The multicomponent nature of the dendrimers and of the corresponding host-guest supramolecules (i.e., end-group mesogens, dendritic core, pyrene unit, aliphatic spacers, and metallacycle) leads to the formation of highly segregated mesophases with a complex multilayered structure due to the tendency of the various constitutive building-blocks to separate in different organized zones. The pyrenyl dendrimers exhibit a multilayered smectic A-like phase, thereafter referred to as LamSmA phase to emphasize this unaccustomed morphology. As for the corresponding Ru_4-metallacycle adducts, they self-organize into a multicontinuous thermotropic cubic phase with the Im3m space group symmetry. This represents a unique example of liquid-crystalline behavior observed for such large and complex supramolecular host-guest assemblies. Models of their supramolecular organizations within both mesophases are proposed.