Palladium determination with a new dye PNBTAN: Structural, UV-VIS, and DFT study

Abstract A new method for the determination of palladium has been developed based on the dispersive liquid–liquid microextraction preconcentration with UV-VIS spectrometry detection. In the proposed approach, 1-[(5-(3-nitrobenzyl)-1,3-thiazol-2-yl)diazenyl]naphthalen-2-ol (PNBTAN) was used as a new chelating agent, and methyl isobutyl ketone and ethanol were selected as extraction and dispersive solvents. The limit of detection (LOD), based on the signal-to-noise (S/N) ratio of 3, was 0.093 µg mL–1. Linearity was observed over the range of 0.24-1.437 µg mL–1 with the correlation coefficient (R) of 0.9993. The developed method has been successfully tested and applied to the determination of trace amounts of palladium in real objects. Analytical properties of PNBTAN and its complexes with palladium were investigated by theoretical calculations and experimental spectrophotometric method. Electron localization function, Fukui function, and molecular electrostatic potential isosurfaces were analyzed as reactivity descriptors for the explanation of the PNBTAN chelation ability. DFT analysis of eleven possible structures of the Pd:PNBTAN (1:2) complex has established the preferred formation of six-membered -O-Pd-N = N- containing cycles. According to the TD-DFT calculations, the experimentally observed bands at 747 and 680 nm in the UV-VIS spectrum of the Pd:PNBTAN (1:2) complex were assigned to the HOMO→LUMO and HOMO→LUMO+1 electron transitions, respectively.