Stable square planar organocopper(III) complexes (CuNCC2, CuNCC4, and CuBN) supported by carbacorrole-based tetradentate macrocyclic ligands with NNNC coordination cores were synthesized, and their structures were elucidated by spectroscopic means including X-ray crystallographic analysis. On the basis of their distinct planar structures, X-ray absorption/photoelectron spectroscopic features, and temperature-independent diamagnetic nature, these organocopper complexes can be preferably considered as novel organocopper(III) species. The remarkable stability of the high-valent Cu(III) states of the complexes stems from the closed-shell electronic structure derived from the peculiar NNNC coordination of the corrole-modified frameworks, which contrasts with the redox-noninnocent radical nature of regular corrole copper(II) complexes with an NNNN core. The proposed structure was supported by DFT (B3LYP) calculations. Furthermore, a π-laminated dimer architecture linked through the inner carbons was obtained from the one-electron oxidation of CuNCC4. We envisage that the precise manipulation of the molecular orbital energies and redox profiles of these organometallic corrole complexes could eventually lead to the isolation of yet unexplored high-valent metal species and the development of their organometallic reactions.

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Chemical looping combustion (CLC) is a key technology for oxy-fuel combustion with inherent separation of CO2 from a flue gas, in which oxygen is derived from a solid oxygen carrier. Multi-cycle CLC performance and the product selectivity towards CO2 formation were achieved using mixed oxide of Cu and Mn (CuMn2O4) (Fd3[combining macron]m, a = b = c = 0.83 nm) as an oxygen carrier. CuMn2O4 was prepared by the co-precipitation method followed by annealing at 900 °C using copper(II) nitrate trihydrate and manganese(II) nitrate tetrahydrate as metal precursors. CuMn2O4 showed oxygen-desorption as well as reducibility at elevated temperatures under CLC conditions. The lattice of CuMn2O4 was altered significantly at higher temperature, however, it was reinstated virtually upon cooling in the presence of air. CuMn2O4 was reduced to CuMnO2, Mn3O4, and Cu2O phases at the intermediate stages, which were further reduced to metallic Cu and MnO upon the removal of reactive oxygen from their lattice. CuMn2O4 showed a remarkable activity towards methane combustion reaction at 750 °C. The reduced phase of CuMn2O4 containing Cu and MnO was readily reinstated when treated with air or oxygen at 750 °C, confirming efficient regeneration of the oxygen carrier. Neither methane combustion efficiency nor oxygen carrying capacity was altered with the increase of CLC cycles at any tested time. The average oxygen carrying capacity of CuMn2O4 was estimated to be 114 mg g(-1), which was not altered significantly with the repeated CLC cycles. Pure CO2 but no CO, which is one of the possible toxic by-products, was formed solely upon methane combustion reaction of CuMn2O4. CuMn2O4 shows potential as a practical CLC material both in terms of multi-cycle performance and product selectivity towards CO2 formation.

Unambiguous evidence has been obtained to explain the presence and effects of both framework and extraframework silver on catalytic properties of Pr(Ag)MnO 3+δ perovskite type materials, using various tools such as XPS, HR-TEM, O 2 -TPD, and H 2 -TPR analysis. Three types of Agincorporated PrMnO 3 perovskite samples were synthesized by means of Ag partial substitution in perovskite lattice and Ag dispersion on the surface of the synthesized perovskite phase, using two different calcination temperatures of 200 and 550 °C. The amount of silver used was 1 wt % (0.000225 mol), in all three catalysts. On the basis of extensive characterization studies, it was clearly explained that the partially substituted Ag for Pr is present in the lattice along with Pr at the "A" site of the ABO 3 perovskite structure. The Ag surface incorporated PrMnO 3+δ sample calcined at 550 °C shows both surface metallic silver and partially substituted Ag in perovskite lattice, whereas Ag 2 O nanoparticles were observed on the surface in the case of another sample calcined at 200 °C. All of the synthesized materials were evaluated for their CO and soot oxidation activity, considering the renewed interest in Ag promoted catalytic materials and ambiguity about its location in the perovskite structure as well as its role in promoting catalytic and other properties of perovskite type materials. Perovskites with surface Ag species show better catalytic activity than the Ag substituted counterpart. This improved and better activity of Ag dispersed samples was because of the presence of the surface active redox couple of Ag/Ag 2 O, which facilitates the surface redox reaction pathway of CO and soot oxidation reactions.

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