Synthesis and Liquid-Crystalline Properties of N,N′-di-(5-(4-Alkoxyphenyl)azo)-Salicylidene-1,2-Phenylene Diiminato Nickel(II) Complexes

Abstract

The synthesis, characterization, and liquid-crystal properties of two new tetradentate N,N′-di-(5-(4-alkoxyphenyl)azo)-salicylidene-1,2 phenylene diimine ligands (alkoxy = octloxy, decyloxy) and their nickel(II) complexes are reported. The ligands were prepared by the condensation of the 5-((4-alkoxyphenyl)azo)salicylaldehydes homologous with 1,2 phenylene diamine. The ligands and their nickel complexes have been characterized by infrared (IR), ¹H nuclear magnetic resonance (NMR), mass spectroscopy, and elemental analyses. The liquid-crystalline properties of the ligands and the related nickel complexes were studied by differential scanning calorimetry (DSC) and by using a polarizing microscope equipped with a heating and cooling stage. None of the free ligands exhibited liquid-crystalline behavior but the copper complexes demonstrated an enantiotropic smectic A mesophase.

Keywords:

• Liquid crystal
• nickel complexes
• salicylaldimine
• Schiff base
• smectic A
• tetradentate

Acknowledgment

The authors sincerely appreciate the financial support from Azarbaijan University of Tarbiat Moallem, Research Vice Chancellor, and Faculty of Basic Science.

Notes

^a Cr = crystal; I = isotropic.

^b Overlapped with a previous transition.