Successive protonation of Lindqvist hexaniobate, [Nb6O19](8-): electronic properties and structural distortions

Autor(es)

Steffler, Fernando ; Haiduke, Roberto L. A.

• Tipo de documento: Artigo Científico
• Fonte: Physical Chemistry Chemical Physics; v. 24, n. 21, p. 11-pg., 2022-05-04.

Resumo

Lindqvist hexaniobate, [Nb6O19](8-), is an intriguing type of polyoxoniobate presenting a significant negative charge, high symmetry, robust structure and applications in photocatalysis. In this work, the [Nb6O19](8-) polyanion was submitted to an investigation of consecutive protonation in water, seeking for the most stable structure in each step. Initially, the preferred protonation sites lie in more distant oxygen atoms from each other, for example, in H-2[Nb6O19](6) the protons added are separated by 4.54 angstrom in the final structure. However, as the successive protonation proceeds, two distinct groups of protons are formed, being clustered at opposite sides of the structure. The geometrical distortions become more significant when an external oxygen site is protonated, with relevant perturbations reaching the structure core. The main ultraviolet/visible excitations along protonation are still associated with an electronic charge transfer phenomenon occurring predominantly from bridging oxygens (O-b) to niobium (Nb) atoms such as those noticed before in the non-protonated structure. Most of the main electronic transitions with photocatalytic interest, with excitation wavelengths between 240 and 200 nm, present a total charge transfer amount near 0.4 e. (AU)

• Processo FAPESP: 14/23714-1 - Cálculos relativísticos de estrutura eletrônica para avaliação de novos conjuntos de funções de base sem prolapso variacional
• Beneficiário: Roberto Luiz Andrade Haiduke
• Modalidade de apoio: Auxílio à Pesquisa - Regular