The Study of the Correlation between the Detection Limit and the Energy Stability of Two Antimony Complexes by Means of Conceptual DFT

Two organometallic complexes, catechol-antimony and pyrogallo-antimony were theoretically studied by means of density functional theory (DFT) calculations. The concept of detection limit in electroanalysis was put in evidence by quantum chemical calculations onto antimony trace analysis in aqueous solution by using pyrogallol (1, 2, 3-trihydroxybenzene) and catechol (1,2-dihydroxybenzene) as ligands. Based on two previously published works, the study was carried out experimentally by polarography technique where the working electrode was a dropping mercury electrode. The DFT study, carried out at the 6-31G* and 3-21G* basis sets combined to LSDA/B3LYP method, showed the existence of a very strong relationship between the total energy of antimony complexes and the detection limit; thus the more stable complex has the better detection limit value. Based on the Fukui indices, the calculated parameters such as local nucleophilicity indices and HOMO-1 electronic density of the ligands showed a high interaction of antimony(III) with pyrogallol than that with catechol. This finding was in good agreement with the experimental results.