Oleg N. Kadkin

New heteropolynuclear metallomesogens: copper(II), palladium(II), nickel(II) and oxovanadium(IV) chelates with [3]ferrocenophane‐containing Schiff's base and β‐aminovinylketone

New mesogenic heteropolynuclear complexes of Cu(II), Pd(II), Ni(II) and VO(IV) with the [3]ferrocenophane‐containing Schiffs base, and Cu(II) and Pd(II) complexes with the [3]ferrocenophane‐containing β‐aminovinylketone have been synthesised. The obtained heterometallic mesogenes are identified by elemental analysis, proton nuclear magnetic resonance, infrared and ultraviolet–visible spectroscopies. Liquid crystalline properties are studied by thermal polarising optical microscopy and differential scanning calorimetry techniques. Both ligands and heteropolynuclear complexes exhibit thermotropic nematic and smectic C mesophases in various temperature ranges except for the Ni(II) complex. Mesomorphism of the prepared complexes is correlated with the geometry of their central chelate core. Considerably broader mesophases and lower transition temperatures are achieved in the synthesised metallomesogens by using the alkylidene‐bridged ferrocene as a building unit.

Liquid crystal phases generated by supramolecular self-assembly of biforked amphiphilic imidazoles

Functional groups with the capability of hydrogen bonding are widely used in the molecular design and preparation of liquid crystalline supramolecular systems, a rapidly growing area of materials showing a high sensitivity towards external stimuli. A series of novel imidazole-containing Schiffs bases replenishing the family of supramolecular liquid crystals has been synthesised and characterised by proton nuclear magnetic resonance, Fourier transform infrared, and ultraviolet–visible spectroscopy, and elemental analyses. Variation of lengths of the terminal alkyl substituents in the obtained amphiphilic imidazoles within 6, 8, 10, 12, 14 and 16 carbon atoms leads to significant changes in their thermal behaviour, micro-segregation and supramolecular self-assembly. Lower homologues were non-mesomorphic, while intermediate members of the homologous series exhibited monotropic bilayered smectic and columnar mesophases. A higher homologue with 16 carbon atoms has an increased trend towards crystallisation of the aliphatic chains and did not exhibit mesomorphism again. The liquid crystalline mesophases were identified and investigated by polarised optical microscopy, differential scanning calorimetry, X-ray diffraction and thermal emission microscopy methods. According to X-ray diffraction characteristics, the smectic mesophase has a bilayered structure where the hydrophilic imidazole groups form a continuous hydrogen bonded network. The interface curvature created by the second alkyl chain leads to the appearance of columnar nanostructures in homologues with 12 and 14 aliphatic carbon atoms.

Effect of hydrogen-bonded supramolecular assembling on liquid crystal properties of imidazole-containing azomethines and their chelates with copper(II)

A series of imidazole-containing rod-like Schiffs bases and their ionic copper(II) chelates with various lengths of the terminal alkyl chain containing 6, 8, 10, 12, 14 and 16 carbon atoms have been synthesised. The synthesised compounds were characterised by elemental analyses, 1H NMR, IR and UV–vis and mass spectroscopies. Thermotropic smectic C mesophases in the ligands and smectic A mesophases in the copper(II) complexes were identified using POM, DSC and small-angle XRD scattering methods. X-ray diffraction patterns of the prepared imidazole imines indicate to supramolecular self-assembled structures in the liquid crystal state, which are formed by means of intermolecular hydrogen bonds. It was established that both liquid crystal arrangement and supramolecular assemblies in ligands disappeared near 190°C, mainly regardless of the lengths of the terminal alkyl chains. Contrary, assembling of the copper(II) complexes into supramolecular bilayers occurs near 200°C, which causes their transition to a smectic A mesophase.