Steric Environment Triggered Self-Healing CuII/HgII Bimetallic Gel with Old CuII–Schiff Base Complex as a New Metalloligand

Abstract

The present work reports an easy to synthesize CuII–Schiff base complex (C-2), in which tunable access of a vacant coordination site for a guest metal via stereoelectronic modulation of a substituent is possible, which might be of great use in the supramolecular self-aggregation process and thus utilized as a metalloligand for the formation of a hetero-bimetallic CuII/HgII gel in methanol. The gelation property of complex C-2 is found to be dependent upon HgII content, and the initial yellow gel transformed into green with a higher equivalent of Hg(OAc)2. The coordination of HgII to complex C-2 is perceived to cause significant charge polarization around the coordinated imine and ultimately lead to corresponding green 2-hydroxy benzaldehyde coordinated CuII complex (C-3) after the hydrolysis, which is responsible for yellow to green gel transformation. The role of anions, metal salts, ligand, and solvents on the gelation property of complex C-2 along with the effect of various external chemical stimuli on the gel and its self-sustainability were studied in detail. The as-synthesized hetero-bimetallic CuII/HgII gel shows an excellent ability as a reusable material for the adsorption of various cationic as well as anionic dyes.