Synthesis and characterization of redox non-innocent cobalt(III) complexes of a O,N,O donor ligand: Radical generation, semi-conductivity, antibacterial and anticancer activities

•Multifunctional Schiff base ligand and its Co-coordination complexes.•I–V & AC study as a full proof of evidence towards usefulness as Semiconductor.•A complete approach (experimental and theory) in exploring redox non-innocence.•Growth inhibition against bacterial and cancer cells growth.

Structural, spectroscopic, electrochemical, electrical conductivity and biological characterizations of cobalt-HBAP [2-(2-hydroxybenzylideneamino) phenol] complexes has been reported. This tridentate HBAP ligand forms a slightly distorted bis octahedral complex, [CoIII(O∩N∩O)2](NEt3H)(H2O)2 (1)−. Several solution state spectroscopic measurements e.g.; UV–Vis, Cyclic voltammetry, EPR, NMR, ESI-MS along with solid state characterizations e.g.; CHN, FT-IR and Single Crystal XRD are performed to authenticate the formation of the ligand as well as its Co-metallated complexes. 1e− oxidation of (1)− to (1)0 have shown an intense phenoxyl radical based transition in UV–Vis spectra. Electron paramagnetic resonance of (1)0 identifies the presence of phenoxyl radical. Meanwhile similar attempt in generation of 1e− reduced species (1)2− provides metal based reduction having metal hyperfines coming from Co nuclear spin I = 7/2. Interestingly, the low spin diamagnetic mononuclear Co(III)-Schiff base complex forms a supramolecular saw teeth like 1D network via hydrogen bonding interaction in presence of countercation [NEt3H]+ and solvent water molecules which are present in the system as solvent of crystallization. Fascinatingly, semiconducting property is found in both ligand and its cobalt metallated complexes. Current–voltage (I–V) and alternating current (AC) studies are carried out to show their effectiveness as functional material. Ligand and Complex (1)− exhibited their effective anti-cancer and anti-bacterial activities. Density functional theoretical (DFT) calculations have shown redox noninnocence of Co-Schiff base complexes is in accord with the experimental outcomes.

Graphical abstractA combination of structural, spectroscopic and theoretical (DFT) calculations of a simple tridentate O,N,O donor Schiff base ligand and its cobalt complexes in different oxidation states have been reported. Multifunctional material properties (both in solid and solution state) have been intensely explored for those materials.Figure optionsDownload full-size imageDownload as PowerPoint slide