Mononuclear and binuclear complexes of salicylidene Schiff bases: synthesis and mesogenic properties

Abstract

The synthesis of new mononuclear and binuclear copper complexes derived from Schiff bases, namely N(4-nalkyloxysalicylidene)-4¢-n-alkylanilines is carried out and their structure and liquid crystalline properties have been investigated. The ligands exhibit rich polymesomorphism; mononuclear complexes exhibit smectic A, smectic C and smectic E phases, while the binuclear complexes mostly exhibit viscous smectic A phase. The isotropic-liquid crystalline transition temperatures of the binuclear complexes in general are found to be lower than their corresponding mononuclear homologues. It was found that the mononuclear complexes exhibit sharp liquid crystalline-isotropic transition temperatures while the binuclear complexes melts over a temperature range. The liquid crystalline phases were characterised by differential scanning calorimetry (DSC) analysis and optical polarised microscopy. X-ray diffraction studies revealed that the intermolecular distance in binuclear complexes is larger than in the mononuclear complexes.

Synthesis and Structural Characterization of Some Lanthanide(III) Nitrate Complexes with a Mesogenic Schiff-Base, N,N’-di-4-(4’-heptadecyloxybenzoate) salicylidene-1,3-diaminopropane Derived from 2,4- dihydroxybenzaldehyde

“…Schiff-base metal complexes have drawn the attention of inorganic chemists because of the interesting properties of these complexes [12,13]. Such complexes play an important role in the development of metallomesogens [9,14,15]. The salicylaldimine ligand system has many advantages in the synthesis of metallomesogen because of its considerable flexibility in the synthetic procedure.…”

“…The salicylaldimine ligand system has many advantages in the synthesis of metallomesogen because of its considerable flexibility in the synthetic procedure. This allows the preparation of a wide variety of liquid crystalline complexes, whose properties are strongly dependent on the ligand structure and the metal ion used [15]. As a part of our further investigation on systematic structural and spectroscopic studies of 3d and 4f metal complexes of a series of Schiff-bases [16][17][18][19][20], we now report here the synthesis and structural characterizations of some Ln III complexes with a Schiff-base, N,N'-di-4-(4-heptadecyloxybenzoate) salicylidene-1,3-diaminopropane derived from 2,4-dihydroxybenzaldehyde.…”