prashant tevatia

In the past two decades, quest of finding sustainable and environment friendly energy sources has increased enormously. Fuel cell technology has seen exciting growth for the solution of requirement of sustainable energy. Fuel cells are based on electrochemical reactions to change chemical energy into electrical energy. For this, reduction of CO2 and O2 are two of the important reactions. Despite quite stable nature of CO2, its reduction can be achieved effectively in presence of catalyst. Both the CO2RR and ORR reactions yield useful byproducts like water, formic acid, formaldehyde, methanol etc. Earlier Pt based catalysts were in use for these conversions in fuel cells. In the recent years, polyaza macrocycle-based catalysts are being applied as these being cost effective. For both above-described purposes, polyazamacrocyclic complexes, like metalloporphyrin, phthalocyanine, have been proved to be very effective. This article is focused mainly on recent advancement in Tetra, Penta and Hexaazamacrocyclic complexes for CO2 RR and ORR reactions.

In present studies, [MnIILCl2] and [CoIILCl2] pentaazamacrocyclic complexes (where L=Dichloro-2,3-dimethyl[b]-pyridyl-3,6,9,12,15-pentaazacyclopentadeca-2,12-diene) have been synthesized by template method and characterized by microanalysis, UV-Vis, IR and mass spectral studies. On the basis of electronic spectral studies, the saddle-shape octahedral geometry has been assigned to these pentaazamacrocyclic complexes. Electrochemical studies of HOMO-LUMO energy levels of these pentaazamacrocyclic complexes have been carried out by using cyclic voltammetry. The onset oxidation and reduction potentials of [MnIILCl2] and [CoIILCl2] macrocyclic complexes were determined under the similar experimental conditions to calculate the ionization potential (Ip) and electron affinity (Ea) for these macrocyclic complexes. The molecular modeling parameters were also calculated from the calculation of HOMO-LUMO energy levels. The obtained values of these parameters are indicating that [MnIILCl2] macrocyclic complex is more stable than [CoIILCl2] complex. The biological activity of these macrocyclic complexes were also taken into account against E. coli, B. cereus, P. aeruginosa, S. aureus and C. albicans microbial pathogen and compared with the standard drug Gentamycin.