Structural studies and quantum chemical calculations of Cr(III), Fe(III) and Ru(III) bromazepam complexes

The reaction of bromazepam (7-bromo-1,3-dihydro-5-(2-pyridyl)-2H-1,4-benzodiazepin-2-one, BZM) with Cr(III) (1), Fe(III) (2) and Ru(III) (3) salts gives complexes of the type [M(BZM)₃]⋅3X (X = Cl or NO₃). Structural characterization was extensively carried out using various analytical and spectral tools such as infrared, ¹H NMR and UV–visible spectroscopies and magnetic, conductance, elemental and thermal analyses. BZM is a bidentate ligand and interacts with the metal ions via the pyridine and benzodiazepin-2-one nitrogen atoms. The magnetic and electronic properties of 2 and 3 are consistent with low-spin octahedral complexes. The three BZM molecules are non-isoenergetically coordinated to the metal ions and this is reflected in the values of the second-order interaction energy. The antibacterial activity was studied using Staphylococcus aureus and Escherichia coli. Coordination of BZM to Cr(III) or Ru(III) ions leads to a marked increase in toxicity with respect to the inactive Fe(III) complex 2.