Synthesis and Mesomorphic Studies of Copper(II) with Carboxylato and N-Donor Ligands
Metal containing liquid crystals also known as metallomesogens is an orientationally ordered liquid that combines properties of both crystalline state and liquid state. Three linear and one branched alkyl chain complexes of general formula [Cu2(RCOO)4(X)2], where R = CH3(CH2)13 (Complex 1, Complex 2), p-CH3(CH2)14OC6H4 (Complex 3) and CH3(CH2)7CH[(CH2)5CH3] (Complex 4), X = pyridine or 2,2-bipyridine were prepared. The single crystal X-ray crystallography of [Cu2(CH3(CH2)13COO)4(py)2] (Complex 1) shows dinuclear complexes with each square pyramidally Cu(II) centre was bridged by four carboxylato molecules and a pyridine molecule. For all complexes, the IR spectra gave the Δνcoo values in the range of 164 - 240 cm-1 , suggesting two binding modes of the alkylcarboxylate ligands. The UV-vis spectra shows a broad d-d band at λmax ~ 664 – 699 nm (εmax ~55 – 341 M-1 cm-1 ), indicating that the distorted square pyramidal geometry at Cu(II). From the results of differential scanning calorimetry (DSC) and optical polarizing microscopy (OPM), complexes 1-4 exhibited liquid crystal mesophases.