A review on the synthesis, characterization and application of Schiff bases containing resorcinol moieties and their first row transition metal complexes

Resorcinol based carbonyl precursors such as 4, 6-Diacetylresorcinol, 2, 4-dihydroxy- acetophenone and 2, 4-dihydroxybenzaldehyde were used for the synthesis of different Schiff bases mainly through conventional method of synthesis. The reviewed Schiff bases were synthesized by condensation reactions between either of these resorcinol based carbonyls and primary amines such as o-aminophenol, o-phenylenediamine, oxalyldihydrazine,1,8-naphthalenediamine,4-methyl-2-amino phenol, hydrazine monohydrate and isatin, 2-amino-4-methylthiazole,4-halo aniline, aminated silica gel, amine derived from hydrazine hydrate, carbon disulfide and benzyl chloride, ethanolamine, 3-hydrazino-5,6-diphenyl-1,2,4-triazine, p-phenylene diamine, semicarbazide hydrochloride, chitosan,α-naphthylamine, paraaminophenol, 4-aminoantipyrine 3,3-Dimethoxybenzidine and benzoylhydrazide. These Schiff bases were formed from different complexes by reacting with different first row transition metal ions. The structures of the Schiff bases and their complexes were elucidated mainly by infrared, UV–visible, nuclear magnetic resonance, mass spectroscopies and elemental analysis. The complexes were also characterized by ESR spectroscopy, conductance & magnetic susceptibility measurement and thermogravimetric analysis. The Schiff base ligands and their first row transition metal complexes were screened for activities including biological, catalytic and chemosensor activities. This review incorporates the progresses that have been observed from 2007 through 2021 on synthesis, characterization and application studies of resorcinol based Schiff bases and their first row transition metal complexes.