A structure-property relationship study of bent-core mesogens with pyridine as the central unit

Abstract

Three series of bent-core mesogens having pyridine as the central unit have been synthesized and characterized. A series of 2,6-diaminopyridine derivatives capable of forming inter- and intramolecular hydrogen bonds exhibit very high melting points. A decrease in the polarity of the central part of the bent-core obtained by replacing the amide with ester linkages results in derivatives with lower melting points and formation of B2- and B7-like mesophases. The introduction of the olefinic groups, which connect the pyridine ring with the inner aromatic rings, helps to further lower the polarity of the central part in the five ring system and led to the formation of B1 and B7 phases. The phases have been determined by optical microscopy observations and differential scanning calorimetry (DSC) and confirmed by X-ray studies. The bending angles and polarity of the investigated five-ring systems have been calculated by the density functional theory (DFT) method.