Experimental and Theoretical Evidence for Encapsulation and Tethering of 1,10-Phenanthroline Complexes of Fe, Cu, and Zn in Zeolite-Y

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.