Experimental and theoretical study of Zn(II) complexation with ceftriaxone

Complexation of Zn2+ cations with antibiotic ceftriaxone anions (Ctx2–) has been studies by pH-metric titration at 25°С and a ionic strength of 0.1 (KNO3). The formation of the ZnCtx complex has been revealed, and logβ(ZnCtx) = 4.45 ± 0.09 has been calculated. The computer model of the complex has been calculated by the DFT method with the use of the B3LYP hybrid functional and the LACV3P**+ basis set. According to these calculations, Zn(II) in the complex has the coordination number 4 and a nearly tetrahedral coordination sphere and is coordinated to Ctx2– through carboxylate, β-lactam, and hydroxytriazinone oxygen atoms and the thiazole nitrogen atom. Formation of the chelate structure accounts for the high stability of the complex.