Antidiabetes, antimicrobial and antioxidant studies of mixed β-diketone and diimine copper(II) complexes

Cu(II) complexes derived from 1,3-diphenylpropane-1,3-dione and 2,2′- bipyridine or 1,10-phenonthroline were synthesized and characterized. The antidiabetics, antimicrobial and antioxidant potency were reported. The drug-likeness of the complexes were also predicted. [Display omitted] A series of copper(II) complexes, [Cu(dbm)(phen)NO3](1), [Cu(dbm)(bipy)NO3](2), [Cu(dbm)(phen)Br](3), [Cu(dbm)(bipy)Br](4), [Cu(dbm)(phen)Cl](5), and [Cu(dbm)(bipy)Cl](6) where dbmH = dibenzoylmethane, bipy = 2,2′- bipyridine and phen = 1,10-phenonthroline have been synthesized and characterized by elemental analysis, molar conductance, magnetic susceptibility, FT-IR and UV–Visible spectroscopies. The crystal structures of complexes 4, 5 and 6 revealed that the geometry around the copper(II) centre is distorted square pyramidal. In this coordination manner, the copper(II) centre bound to two oxygen atoms from dbmH, two nitrogen atoms from the co-ligand (phen or bipy), and also to a counter ion (NO3– or Cl- or Br-). The molar conductivity measurement in nitromethane displayed a Λm value of 14–55 Ω−1 cm2 mole-1, which confirms that they are non-electrolyte. The antimicrobial, antidiabetic studies and antioxidant properties for all six complexes were also evaluated. All the complexes showed moderate to good antibacterial activities against E. coli, P. aeruginosa, S. aureus, and B. subtillis. Complex 5 was observed to be more active than ciprofloxacin against all the tested bacteria. Antidiabetes properties of the complexes were also investigated using α-glucosidase and α-amylase assay. Complex 5 had 27 µM and >1000 µM while the reference drug, acarbose, had 28 µM and 948 µM for α-glucosidase and α-amylase inhibition, respectively. Complex 5 with the lowest IC50 value of 437 µM showed the highest NO• scavenging activity than other complexes and even gallic acid with IC50 values of 457 µM (standard drug). However, all the complexes showed poor free radical scavenging ability. Density functional theory was used to determine the appropriate geometries and electronic properties of complexes 4, 5 and 6 at the atomic level.