NMR Investigation of the Copper(II)-Ciprofloxacin System

A proton NMR study was performed on the copper(ll)-ciprofloxacin system. The proton relaxation times (T(1)) were determined from the titration data in acidic and basic media. In acidic medium the H5 signal is dramatically affected and it is assumed that copper is bonded to the quinolone through carbonyl and one of the carboxyl oxygens. Such bonding is in agreement with the X-ray literature data for the complex [Cu(cf)(1)]Cl(2).6H(2)O isolated from the slightly acidic solution. There are additional significant changes in (1)T(1) of H3' and H5' atoms which suggest that the terminal nitrogen atom of the piperazine ring system-N4' also interacts with copper in the basic conditions. Thus it is plausible that more than one species are present in the solution at high pH values.