Solvent assisted mechanochemical synthesis, antimicrobial and antioxidant studies of Ni2+, Mn2+, Cr2+ , and Cu2+ Metal complexes of some ligands derived from l-histidine and l-alanine

Abstract

Mechanochemistry enables rapid, quantitative reactions to occur at or close to 27℃. It is a one-step process that allows for reactant homogenization, product nucleation, and particle growth. These processes use little or no solvent, making them less wasteful and more  environmentally friendly than solvent-based reactions. Ni²⁺ , Mn²⁺, Cr²⁺and Cu2+ metal ions were synthesized by grinding in an agate  mortar with pestle using ligands derived from amino acids (Histidine &Alanine) which were further synthesized to form complexes. The  entire experiment was carried out by solvent solvent-assisted mechanochemical process and ethanol was used as liquid liquid-assisted  solvent. The complexes were characterized by IR spectroscopy, U-V spectroscopy, X-ray analysis, melting point, solubility test, and  conductivity measurement. The Solubility test showed that the complexes are soluble in DMSO, DMF, and ethanol and are insoluble in  both hexane and tetrachloromethane. The molar conductivity values are in the range of (6.05-28.56) Ω-1cm2mol^-1 ) indicating the  complexes behave as non-electrolytes. IR analysis showed a vibrational frequency band observed at (1620-1625) cm^-1 which is assigned  to the ʋ(C=N) of the azomethine, also the new bands M=N, M=O indicate the coordination reaction between the metal and the ligands.  The UV visible analysis shows various transitions, the metal complexes showed adsorption bands at λ of 420 and 575nm respectively  because of the ligand-to-metal charge transfer (LMCT). The XRD analysis showed that there was a change in phase between the starting  material and the product which indicate that a reaction occurred, also the nature of the spectra showed that the compounds are all  crystalline. The Antimicrobial activity showed that both the complexes and the ligands have good activity against the bacterial isolates.  Antioxidant activity was also tested and the compound appeared to have moderate scavenging activities compared to the reference used.  The values indicated that the activities are more pronounced when coordinated with metal ions.