No abstract

It is observed that for a square planar Ni(II)-Schiff base complex of the general formula {Ni(II)L}, where L is {L: N,N'-bis(5-hydroxy-salicylidene)ethylenediamine}, when encapsulated in a supercage of zeolite Y the bulky guest complex adopts a non-planar geometry without disturbing the integrity of the zeolite framework. Detailed comparative characterization is carried out to understand the structural change of the guest complex as a result of steric and electronic interactions with the host framework. UV-Vis spectroscopic studies of the encapsulated and 'neat' complex show a significant blue shift in the d-d transition after encapsulation and the diamagnetic 'neat' complex exhibits paramagnetism after encapsulation. DFT studies of the Ni(II)-Schiff base complex have been carried out for different spin states in neat and encapsulated form and the UV-Vis spectra are simulated using TD-DFT to understand the observed spectra in detail.

Square planar Ni(ii)-Schiff base complexes when encapsulated in a supercage of zeolite Y have shown altered optical, magnetic properties and catalytic activities in comparison to their corresponding free states. Different characterization techniques like XRD analysis, SEM-EDX, AAS, FTIR, UV-Visible spectroscopy and magnetic studies as well as detailed theoretical studies altogether show the differences in the properties of complexes in free and encapsulated states. All these studies have suggested that the largest complex deviates by the maximum amount from its free-state properties and a fascinating correlation between the extent of deviation from molecular dimension and modified catalytic activity of encapsulated complexes is observed.