NMR Investigation of the Copper(II)-Ciprofloxacin System
Iztok Turel,1Janez Košmrlj,1Bjørn Andersen,2and Einar Sletten2
Received04 Nov 1998
Accepted03 Dec 1998
Abstract
A proton NMR study was performed on the copper(ll)-ciprofloxacin system. The proton
relaxation times (T1)
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)2]Cl2.6H2O
isolated from the
slightly acidic solution. There are additional significant changes in T1 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.