Monitoring mettalic toxins using azomethinic cyclic and semi cyclic receptors

Abstract

The work described in the thesis was aimed to develop strategies for selective recognition, efficient extraction, and sensitive quantification of metallic toxins. To accomplish framed objectives of the proposed plan, some azomethinic receptors were synthesized and characterized by suitable techniques. The denticity of Schiff base was varied to get heterodentate receptors possessing N4O3, N2O3, N3O2, N6O2, N4O2, N6O2, N4O2, N2O2, NO2 and N6 donor systems. Besides, presence of multiple hydroxyl groups along with N donor sites favour strong coordination of metal ions with Schiff base receptors. The synthesized receptors were investigated for their colorimetric, spectrophotometric and spectrofluorimetric response towards various metal ions like Fe2+, Fe3+, Zn2+, Cd2+ and oxyanions such as SeO32- and AsO2-. In order to use the azomethinic receptors as probes for monitoring metallic toxins, protocols were standardized for developing recognition, quantification and extraction strategies for various metal ions. The interaction of receptors with metallic toxins was investigated by NMR titrations, spectrophotometric and spectrofluorimetric experiments. The selectivity of probes was assured by investigating interference of co-existing metal ions and anions. Besides, receptors were incorporated on the silica and graphene surfaces to obtain heterogenous materials for easy separation of probes from samples. To immobilize the azomethinic receptors on solid surfaces, silatranyl derivatives of some receptor were obtained. The silatranyl moieties are excellent for anchoring organic moieties on various surfaces. In the present work, silatranyl receptors were immobilized on silica nanoparticles, mesoporous silica nanoparticles and graphene oxide sheets via sol-gel method. The fabricated surfaces were further used for the adsorption of toxic metal ions. newline newline newline