A reaction of N₁,N₃-bis(3-methoxysalicylidene) diethylenetriamine (H₂Vd) and Zn(NO₃)₂·6H₂O, ZnBr₂, ZnI₂ and Cd(NO₃)₂·4H₂O in a methanol solution led to zinc and cadmium complexes of different nuclearities, [Zn₂(Vd·H)₂(X)₂]·CH₃OH (X = NO₃, Br, I) [1a, 1b and 1c] and Cd₃(Vd)₂(NO₃)₂ (2). In 1(a–c), two H₂Vd ligands bridge the two metal centers whereas in 2, they provide sideways support to two terminal Cd²⁺ ions, providing an all-oxygen envelope to the central Cd²⁺ ion. All four compounds were characterized by elemental analysis, FT-IR spectroscopy and single crystal X-ray diffraction analysis. Complexes 1(a–c) exhibit dinuclear structures, whereas 2 exhibits a nearly linear trinuclear structure. The structural differences among these complexes are attributable to various coordination modes and flexible configurations of the H₂Vd ligand. The ligand H₂Vd is an excellent probe for sensing Zn²⁺ in solution, whereas complexes 1(a–c) are able to selectively detect pyrophosphate (PPi) in aqueous medium. The structure of the pyrophosphate (PPi) complex has been proposed using DFT calculations and the selectivity is due to the unique ability of this anion to simultaneously coordinate to both the Zn metal centers. The anticancer activity of complexes 1(a–c) was also explored.

We have synthesized and structurally characterized a new doubly chloro bridged dimeric copper(II) complex, [Cu₂(μ-Cl)₂(HL)₂Cl₂] (1) based on a Schiff base ligand, 5-[(pyridin-2-ylmethylene)-amino]-pentan-1-ol). Single crystal X-ray diffraction shows the presence of dinuclear copper(II) centres in a square pyramidal geometry linked by obtuse double chloro bridge. The magnetic study illustrated that weak antiferromagnetic interactions (J = −0.47 cm⁻¹) prevail in complex 1 which is well supported by magneto-structural correlation. This compound adds to the library of doubly chloro bridged copper(II) complexes in the regime of spin state cross over. DFT calculations have been conducted within a broken-symmetry (BS) framework to investigate the exchange interaction further which depicts that the approximate spin projection technique yields the best corroboration of the experimental J value. Spin density plots show the presence of an ∼0.52e charge residing on the copper atom along with a substantial charge on bridging and peripheral chlorine atoms. The potential of complex 1 to act as an anticancer agent is thoroughly examined on a series of liver cancer cell lines and screening shows the HepG2 cell line exhibits maximum cytotoxicity by phosphatidyl serine exposure in the outer cell membrane associated with ROS generation and mitochondrial depolarization with increasing time in the in vitro model system.