Synthesis, molecular structure and mesomorphic phase behavior of n¹-benzylideneaniline palladium(II) complexes

The synthesis and characterization of very stable Pd(II) n¹-imine complexes of bis(3,4-dialkyloxybenzylidene3′,4′-dialkyloxyaniline) dichloropalladium(II) with alkyl chain of hexyl (8), octyl (9), decyl (10) and dodecyl (11) groups, and of bis(4-ethyloxybenzylidene-4′-ethyloxyaniline)dichloropalladium(II) as a model complex are described. The molecular structure with twisted board-like geometry of the complex resulting from the coordination of Pd(II) with n¹-imine bonding was confirmed by X-ray crystallographic analysis of the model complex. In contrast to the imine ligands, all the complexes with an exception of 11 display a thermally stable monotropic smectic A mesophase without any decomposition of the complex. These results, characterized by a combination of differential scanning calorimetry, optical polarized microscopy, and powder X-ray scattering experiments, are discussed.