UNUSUAL MOLECULAR PACKING WITHIN THE LOW-SYMMETRY MESOPHASES OF ALKYL-ACYLHYDRAZINATONICKEL(II) AND ALKOXY-ACYLHYDRAZINATONICKEL(II) LIQUID-CRYSTALS

Three series of novel thermotropic metallomesogens have been synthesiz ed and characterized using microscopy and DSC. Unexpected X-ray scatte ring is observed within all of the observed mesophases. Diffuse in-lay er reflections are observed both at angles corresponding to approximat ely twice the molecular width and to the side-by-side separation of mo lecules within the nematic, SmA and SmC mesophases. Furthermore, the t ilt angles within the SmC phases are observed to decrease as the termi nal chain lengths decrease. Conoscopic observations show the SmC phase s to be strongly biaxial as expected, but surprisingly, weak biaxialit y is also observed within both the SmA and nematic mesophases. A model to explain the results is proposed, in which the cores remain orthogo nal to the layers, whilst the overall molecular tilt necessary for SmC phase formation is provided by the contribution of the terminal alkyl chains to the overall molecular shape. IR spectroscopy is used to con firm the model.