Cobalt (II) phthalocyanine (CoPc) molecules have been encapsulated within the supercage of zeolite-Y. The square-planar complex, being larger than the almost spherical cage, is forced to adopt a distorted geometry on encapsulation. A comparative spectroscopic and magnetic investigation of CoPc encapsulated in zeolite-Y and in the unencapsulated state is reported. These results supported by molecular modeling have been used to understand the nature and extent of the loss of planarity of CoPc on encapsulation. The encapsulated molecule is shown to be the trans-diprotonated species in which the center of inversion is lost due to distortions required to accommodate the square complex within the zeolite. Encapsulation also leads to an enhancement of the magnetic moment of the CoPc. This is shown to be a consequence of the nonplanar geometry of the encapsulated molecule resulting in an excited high-spin state being thermally accessible.

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.

A series of palladium complexes of tetradendate Schiff base ligands L1 (N,N′-bis(salicylidene)phenylene-1,3-diamine) and its derivatives L2 and L3 have been synthesized by using the "flexible ligand method" within the supercage of zeolite-Y. These complexes in both their free and encapsulated states have been thoroughly characterized with the help of different characterization tools such as XRD, SEM-EDS, BET, thermal analysis, XPS, IR, and UV−vis spectroscopic studies. All these encapsulated complexes are identified with a dramatic red shift of the d−d transition in their electronic spectra when compared with their free states. Theoretical as well as experimental studies together suggest a substantial modification of the structural parameters of square planar Pd(II)−Schiff base complexes upon encapsulation within the supercage of zeolite-Y. Encapsulated complexes are also subject to show modified catalytic activities toward the Heck reaction. These heterogeneous catalysts can easily be separated from the reaction mixture and reused.