Synthesis, crystal structure and action on Escherichia coli by microcalorimetry of copper complexes with 1,10-phenanthroline and amino acid

Copper complexes: Cu(phen)(L-Ser)(H₂O)Cl] (1), Cu(phen)(Gly)(H₂O)]Cl·3H₂O (2), Cu(phen)(L-Ala)(H₂O)]Cl·H₂O (3), Cu(phen)(L-Phe)(H₂O)]Cl·2.5H₂O (4), Cu(phen)₂Cl₂·6H₂O (5) (phen = 1,10-phenanthroline) were synthesized and characterized. The structure of 1 was characterized by X-ray crystallography and showed in a triclinic system with space group P1, a = 6.8953(15) Å, b = 10.737(2) Å, c = 11.894(3) Å, α = 110.395(3)°, β = 94.183(4)° and γ = 100.540(3)°. The antibacterial activities on Escherichia coli (E. coli) of these five copper complexes and CuCl₂ (6) were investigated by microcalorimetry. By analyzing the obtained metabolic thermogenic data and curves, crucial parameters such as rate constant of bacterial growth (k), half inhibitory concentration (IC₅₀), and generation time (t_G) were determined. All these copper complexes could stimulate the growth of the E. coli at their lower concentration. At their higher concentration they all showed antibacterial action. The inhibition on E. coli was 5 > 1 ≈ 2 ≈ 3 ≈ 4 > 6. And the antibacterial mechanism was discussed preliminarily.