Solid-state grinding of palladium and copper salts allowed the growth of palladium/copper oxide interface at the zeolite-Y surface. The hybrid nanostructured material was used as reusable heterogeneous catalyst for selective oxidation of various benzyl alcohols. The large surface area provided by the zeolite-Y matrix highly influenced the catalytic activity, as well as the recyclability of the synthesized catalyst. Impregnation of PdO-CuO nanoparticles on zeolite crystallite leads to the generation of mesoporous channel that probably prevented the leaching of the metal-oxide nanoparticles and endorsed high mass transfer. Formation of mesoporous channel at the external surface of zeolite-Y was evident from transmission electron microscopy and surface area analysis. PdO-CuO nanoparticles were found to be within the range of 2-5 nm. The surface area of PdO-CuO-Y catalyst was found to be much lower than parent zeolite-Y. The decrease in surface area as well as the presence of hysteresis loop in the N-adsoprtion isotherm further suggested successful encapsulation of PdO-CuO nanoparticles via the mesoporous channel formation. The high positive shifting in binding energy in both Pd and Cu was attributed to the influence of zeolite-Y framework on lattice contraction of metal oxides via confinement effect. PdO-CuO-Y catalyst was found to oxidize benzyl alcohol with 99% selectivity. On subjecting to microwave irradiation the same oxidation reaction was found to occur at ambient condition giving same conversion and selectivity.

Iron(III) Schiff-base complexes of general formula [Fe(L)(2)Cl]·2H(2)O, where L = N,Ń-bis(salicylidene)ethylenediamine and N,Ń-disalicylidene-1,2-phenylenediamine have been encapsulated within various alkali exchanged zeolites viz. LiY, NaY, and KY by flexible ligand method. The encapsulated complexes are characterized by EDX, scanning electron microscopy (SEM), powder X-ray diffraction (XRD), FT-IR, UV-vis, diffuse reflectance spectroscopy (DRS), electron spin resonance spectroscopy (ESR) and cyclic voltammetry studies. The diffuse reflectance UV-vis spectra of encapsulated complexes show a dramatic red shift of the charge transfer band with increasing electropositivity of the exchangeable cations. The electrochemical analysis predicts the shifting of the reduction potential toward negative values with increasing size of the alkali exchanged cations. The zeolite encapsulated Schiff-base complexes of iron are found to be catalytically active toward the oxidative coupling of 2-napthol. Metal complexes incorporated in potassium exchanged zeolite-Y are found to be more effective for catalytic conversion of 2-naphthol to binaphthol and induces higher selectivity toward the R-conformation. The catalytic conversion of 2-napthol to BINOL is found to depend on the reduction potential of the catalyst, with a more negative reduction potential being better for the catalytic conversion. Density functional calculation is being carried out on both the neat Fe-Salen and Fe-Salophen complexes and those encapsulated in NaY zeolite to investigate change in structural parameters, energies of the HOMO and LUMO, and global hardness and softness. Fukui functions, as local descriptors, are used to analyze the hard-hard interaction at a particular site of the complexes.

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Pd–Au nanoalloy supported on zeolite-Y (Pd–Au–Y) matrix was found to be an effective catalyst for C–Cl bond activation and oxidative coupling of 2-naphthol, leading to the formation of various biaryl products and 1,1′-bi-2-naphthol, BINOL. The same catalyst was also highly efficient for selective oxidation of benzylic alcohols to benzaldehydes. Cinnamaldehydes were obtained directly from benzaldehydes by aldol condensation with acetaldehyde generated in situ by partial oxidation of ethanol in the presence of Pd–Au–Y catalyst at 120 °C under basic condition. The biaryl products were also obtained directly from benzylic alcohols in a one-pot system by reacting with phenylboronic acid. The formation of biaryls from benzylic alcohols was believed to occur via one-pot benzylic C–H and C–Cl bond activation. A high % yield of biaryls, BINOL, aldehydes, and cinnamaldehydes was obtained by performing different reactions using the single Pd–Au–Y catalyst. The strong interaction of chloro-benzylic alcohol was predominantly located at active gold species. X-ray photoelectron and diffuse reflectance spectroscopic studies revealed the strong interaction between Pd and Au particles. Electrochemical studies provided proper evidence for the individual role of the nanoparticles (NPs) in one-pot synthesis of biaryls from benzylic alcohols.

A DFT and ab initio quantum chemical study has been carried out at different theoretical levels to delve into the role of the cation-π interaction within the main group metal cations (Li(+), Na(+) and K(+)), substituted benzene and borazine. The effects of electron withdrawing and electron donating groups on these non-covalent forces of interaction were also studied. The excellent correlation between Hammett constants and binding energy values indicates that the cation-π interaction is influenced by both inductive and resonance effects. Electron donating groups (EDG) such as -CH3 and -NH2 attached to benzene at the 1, 3 and 5 position and the three boron atoms of borazine were found to strengthen these interactions, while electron withdrawing groups (EWG) such as -NO2 did the reverse. These results were further substantiated by topological analysis using the quantum theory of atoms in molecules (QTAIM). The polarized continuum model (PCM) and the discrete solvation model were used to elucidate the effect of solvation on the cation-π interaction. The size of the cations and the nature of the substituents were found to influence the enthalpy and binding energy of the systems (or complex). In the gas phase, the cation-π interaction was found to be exothermic, whereas in the presence of a polar solvent the interaction was highly endothermic. Thermochemical analysis predicts the presence of thermodynamic driving forces for borazine and benzene substituted with EDG. DFT based reactivity descriptors, such as global hardness (η), chemical potential (μ) and the electrophilicity index (ω) were used to elucidate the effect of the substituent on the reactivity of the cation-π complexes.

Tris(1,10-phenanthroline) complexes of iron(II), copper(II), and zinc(II) have been encapsulated within the supercage of zeolite–NaY by the reaction of exchanged metal ion and flexible ligand that diffuses into the cavities. The hybrid material obtained has been characterized by elemental analysis (EDX), SEM, powder XRD, FTIR, UV–vis/DRS, cyclic voltammetry, and EPR techniques. The Fe and Cu complexes show electrochemical behavior in the presence of 0.1 M TBAP, whereas Zn complex gives electrochemical response only in the presence of H+ ion. This difference in electrochemical behavior of the complexes indicates an intrazeolite electron transport in the case of Fe and Cu phenanthroline complexes and an extrazeolite electron transport in the case of Zn complex anchored on the surface of zeolite–Y. The red shifting of UV–vis spectra and changes in redox properties of intrazeolite complexes in comparison to those of the neat complexes suggest that the zeolite matrix influences the electronic properties. This has been further supported by computational studies where we found a change in the energies of the HOMO and LUMO. TDDFT calculations on the neat phenanthroline complexes are being carried out in order to allow an accurate characterization and assignment of UV–vis absorption features for direct comparison of calculated absorption spectra with the solution experimental data. Density functional theory is being used to calculate a range of DFT-based descriptors such as global hardness, local softness, and Fukui functions in order to investigate the change in the reactivity of the metal complexes upon encapsulation.

Two chiral Schiff-base complexes of copper(II) have been successfully encapsulated inside the cavity of zeolite-NaY via a "ship in a bottle" synthesis method. The presence of the two complexes inside the cages of zeolite-Y has been confirmed based on various spectrochemical and physicochemical techniques, viz. FTIR, UV-vis/DRS, ESR, XPS, CV, EDX, SEM, and TGA. Zeolite-encapsulated chiral copper(II) Schiff-base complexes are found to give a high-enantioselective (84% ee, R conformation) nitro-aldol product at -20 °C. The encapsulated copper complexes are found to show higher catalytic efficiency than their homogeneous counterparts under identical conditions. Density functional theory (DFT) calculation has been implemented to understand the effect of the zeolite matrix on structural, electronic, and reactivity properties of the synthesized complexes. Theoretical calculation predicts that upon encapsulation into the zeolite matrix the Cu center becomes more susceptible to nucleophilic attack, favoring a nitro-aldol reaction. A plausible mechanism is suggested based on the experimental and theoretical results. The structures of reaction intermediates and transition state(s) involved in the catalytic cycle are derived using DFT.