Encapsulated Schiff base nickel complex in zeolite Y: Correlation between catalytic activities and extent of distortion supported by experimental and DFT studies

Abstract

It is observed that planar Ni(II)–Schiff base complexes of general formulae NiL with L as N, Ń-bis(4-hydroxy salicylidene)ethylenediamine (4-OH-salen) when encapsulated in the supercage of zeolite Y, the complex adopts non-planar geometry. The detailed characterization studies of the 4-OH-Ni-salen complex when compared with Ni-salen complex encapsulated in zeolite Y (Ni-salen-Y) Choudhary et al. (2016) have suggested that the complex undergoes more distortion in order to accommodate itself inside the supercage of zeolite-Y. Optical spectroscopic studies show relatively more blue shifted and intensified d-d transition for 4-OH-Ni-salen complex after encapsulation. We also report the catalytic activities and enhanced magnetization of encapsulated complex though it is diamagnetic in the ‘free’ state. DFT studies of these complexes have been carried out in different spin states and electronic spectra are simulated to have better insight about the geometries adopted by the guest complexes inside the host framework.