Complex formation between some metals and a quinolone family member (ciprofloxacin)

Some metal [Ca(II), Co(II), Ni(II), Cu(II), Zn(II), Al(III) and Fe(III)] complexes of the quinolone family member (ciprofloxacin = cf) were studied by potentiometric and spectroscopic methods in solution. The results of EPR and polarographic methods are also included. The titration curves for the metal ion-ciprofloxacin were evaluated by assuming all possible models. It was found that a lot of protonated complexes are formed before precipitation in the systems studied. The UV-vis results in the Cu(II)-cf system showed that in the more acidic region a 1:1 complex is favoured; whereas a 1:2 complex prevailed at higher pH values. The coordination of the second ligand is somewhat more favoured than that of the first ligand, and it seems probable that the 1:1 complex is more distorted. Some ternary complexes [Cu(II)-cf-2,2'-bipyridyl, -glycine and -tyrosine] were studied as well. From the Delta log K value, it was deduced that the formation of the mixed ligand complex in the system Cu(II)-cf-2,2'-bipyridyl is favoured due to back-coordination.