Photoluminescent columnar zinc(II) bimetallomesogen of tridentate [ONO]-donor Schiff base ligand

Abstract

A new zinc(II) bimetallomesogenic complex, [Zn₂L₂], of tridentate [ONO]-donor Schiff base ligand (L = N-(2-hydroxyethyl)-4-hexadecyloxysalicylaldimines) was synthesised and their mesomorphic and photoluminescence properties were investigated. The compounds were characterised by Fourier transform infrared spectroscopy (FTIR), ¹H and ¹³C nuclear magnetic resonance (NMR), ultraviolet-visible spectroscopy (UV-Vis) spectroscopy, elemental analyses and fast atom bombardment (FAB) mass spectrometry. The mesomorphic behaviour of the complex was investigated by polarised optical microscopy, differential scanning calorimetry and X-ray diffraction (XRD) study. A rectangular or oblique columnar mesophase is conjectured on the basis of powder X-ray diffraction (PXRD) study. The complex is found to be blue light emitter in solution, in solid and in condensed states with broad emission maxima at ∼427–464 nm. The density functional theory (DFT) calculations revealed a distorted square planar structure around each zinc(II) centre in the dinuclear framework. Time-dependent DFT spectral correlative study was undertaken to account for the electronic transition.

Keywords:

• Zinc
• bimetallomesogen
• columnar mesophase
• photoluminescent
• density functional theory

Acknowledgements

The authors thank Sophisticated Analytical Instrument Facility (SAIF), North-Eastern Hill University (NEHU), Shillong for providing analytical and spectral data. The author Paritosh Mondal thanks the Department of Science and Technology, New Delhi for financial support (SR/FT/CS-86/2010) and CD and DD acknowledges financial support from University Grants Commission. The authors are also thankful to the Department of Biotechnology – e Library Consortium (DeLCON) of Bioinformatics Centre, Assam University, Silchar (India).