ABSTRACT
Correction for 'Successive protonation of Lindqvist hexaniobate, [Nb6O19]8-: electronic properties and structural distortions' by Fernando Steffler et al., Phys. Chem. Chem. Phys., 2022, 24, 13083-13093, https://doi.org/10.1039/d2cp00607c.
ABSTRACT
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 H2[Nb6O19]6 the protons added are separated by 4.54 Å 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 (Ob) 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.
ABSTRACT
A new class of polyoxoniobate complex has been synthesized and characterized as a novel anticancer agent for photodynamic therapy. The complex inhibits the growth of chronic myelogenous leukemia cells with an IC50 value of 30 µM, in the dark. However, upon exposure to light (365 nm) there is a fivefold increase in the cytotoxic activity. Light radiation activate the complex with the formation of radical species capable of interacting with DNA according to our experimental and theoretical data.
