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.

Keywords:

• Aluminum
• hydrazone complexes
• coordination properties
• mass spectrometry
• UV-Vis
• DFT calculations

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Croatian Science Foundation (Project IP-2014-09-4841) and by the project FarmInova (KK.01.1.1.02.0021) funded by the European Regional Development Fund. Computations were performed using the Advanced computing service provided by University of Zagreb University Computing Centre - SRCE.