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

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.