New Zn(II) diaqua complex with pivalic acid: Synthesis, characterization, DFT calculations, photoluminescence and photocatalytic properties

A zinc(II) complex, [Zn(H2O)2(piv)2], (1) is prepared by the reaction of ZnCl2 with pivalic acid (piv) in the presence of sodium azide. Structural analysis indicates that the symmetric unit of the complex consists of one Zn (II) molecule with two pivalate ions involved in their oxygen atom and two water molecules occupied the terminal position. We observed the photoluminescence (PL) characteristics at a wavelength of 226 nm, and the broad peaks in the spectrum could potentially originate from inherent defect states in the zinc structure. The photocatalytic activity of 1 was studied against aqueous methylene blue (MB) dye, and degradation was found to be 79.98 % at optimized conditions of MB concentration = 30 mg/L, catalyst dosage = 10 mg, pH = 8, and temperature = 313K. The reaction kinetics showed that degradation efficiency was increased by increasing the light irradiation time with a high-rate constant of 0.00919 min-1, and the reaction followed pseudo-first order kinetics. Furthermore, the recyclability test confirmed that 1 retained excellent photodegradation efficiency, and the radical scavenging assay showed the active participation of holes, hydroxyl radicals, and superoxide anions in carrying out the degradation process. The experimental data supports the theoretical calculations.