Geometrical and Spectroscopic Simulations in Mixed Lindqvist Polyoxoniobates and Tantalates: A DFT Study

Polyoxometalates are extensively researched chemical entities with well-documented applications ranging from photochemical processes to hydrogen evolution reactions. Niobium and tantalum, two metals that naturally co-occur, present separation challenges experimentally. Consequently, the stability of mixed Lindqvist polyoxoniobates and tantalates was investigated. Density functional theory (DFT) and time-dependent DFT simulations are employed to determine the electronic structures of these compounds. It was found that the cohesive energy of tantalum-based species is lower than that of niobium-based species, suggesting reduced stability in the formation of Lindqvist hexatantalate, with energies of −1846 and 0 kJ mol–1, respectively. The spectrum analysis indicates Nb– O being dominant in the charge-transfer process and therefore more suitable for photochemical applications. This study aims to elucidate the electronic structure and spectroscopic characteristics of mixed Lindqvist species, enhancing understanding for future applications.