Aluminum(III) complexes of aroylhydrazones derived from nicotinic acid hydrazide: MS, UV-Vis and DFT study

Abstract

In the continuation of our study on aroylhydrazones, the binding properties of N'-(2,3-dihydroxy-phenylmethylidene)-3-pyridinecarbohydrazide (H2L1 ), N'-(2,4-dihydroxy-phenylmethylidene)-3-pyridinecarbohydrazide (H2L2 ) and N'-(2,5-dihydroxy-phenylmethylidene)-3-pyridinecarbohydrazide (H2L3 ) towards potential toxic Al(III) ions were investigated in methanol/water 50/50 solution by mass spectrometry, UV-Vis spectrophotometry and DFT calculations. The stability constants (logK) for Al(III)-H2L 1:1 complexes in MeOH/H2O 1/1 at pH 2.52 were determined as 3.39, 2.87 and 2.59, respectively. Detailed characterization of complexes was performed by high-resolution mass spectrometry. The MS spectra reveal the formation of 1:1 complexes with decreasing stability in the order H2L1 > H2L2 > H2L3 . DFT calculations revealed several possible modes of ligand coordination, acting as bidentate or tridentate ligands. The comparison with analogous Ga(III) complexes was made as well.