Hockey-stick liquid crystalline 6-oxoverdazyl

Abstract

ABSTRACTA series of hockey-stick shaped 6-oxoverdazyl radicals 1[n]–3[n], containing CH3 (a), CF3 (b) and CN (c) groups in the short ‘arm’, were prepared and their physical properties were investigated. Mesogenic behaviour was found only in the CN derivatives with the COO (1[n]c) and N=N (2[12]c) linking groups, which exhibited a nematic phase. Analysis of binary mixtures of selected compounds with bent-core nematic host 4[12] gave virtual nematic-isotropic transition temperatures, [TNI], which follow the order 1[12]b < 1[12]c < 1[12]a in one series and 1[12]c < 2[12]c < (3[12]c) in another. The observed effectiveness of the short-arm substituent, CF3 < CN < CH3, was related to the magnitude and orientation of the molecular dipole moment calculated with density functional theory methods.