Metal-directed columnar phase formation in tetrahedral zinc(ii) and manganese(ii) metallomesogens

Abstract

New, non-discoid M(II) complexes [MCl₂(L)] {M = Mn, Zn; L = 2,6-diformyl-4-methylphenolbis[3′,4′,5′-tris(hexadecyloxy)phenylimine]} have been prepared and shown to exhibit columnar mesophases, the nature of which was found to be metal-dependent. As analysed by DSC and small-angle X-ray diffraction experiments, the complex [ZnCl₂(L)] exhibits a single mesophase with rectangular symmetry (Col_r) between 46 and 145 °C, whereas the Mn(II) analogue [MnCl₂(L)] displays a purely hexagonal mesophase (Col_h) phase between 55 and 285 °C. By combining these results with those obtained from dilatometry, a model for the molecular organisation within the columnar mesophases is proposed. The single-crystal X-ray structure of the related complex [Zn(NO₃)(L′)₂]NO₃·3MeOH {L′ = 2,6-diformyl-4-methylphenolbis[3′,4′,5′-tris(methoxy)phenylimine]} has been determined and supports the proposed mode of binding of the ligand to the metal via only one imine and a phenol.