Experimental study and computer modeling of Ni(II) and Cu(II) complexation with ceftazidime

Abstract

The protonation constants of the anion of the cephalosporin antibiotic ceftazidime Ctzd^– and formation constants of its complexes with Ni²⁺ and Cu²⁺ have been determined by pH metric titration at 25°С and ionic strength 0.1 (KNO₃): logβ(HCtzd) = 4.82 ± 0.04, logβ(H₂Ctzd⁺) = 7.62 ± 0.06, logβ(H₃Ctzd²⁺) = 9.23 ± 0.09, logβ(NiCtzd⁺) = 4.04 ± 0.03, logβ(Ni(Ctzd)₂) = 6.41 ± 0.06, and logβ(CuCtzd⁺) = 5.03 ± 0.06. The potentiometric method has failed to reveal the complexation of Ctzd^– with Co²⁺, Zn²⁺, and Cd²⁺. The composition of the [Ni(Ctzd)₂] and [CuCtzd]⁺ complexes has been confirmed by spectrophotometry. The computer models of the [NiCtzd]⁺ and [CuCtzd]⁺ complexes have been calculated by the DFT method with the use of the B3LYP hybrid functional and the LACV3P**++ basis set.