Binuclear copper complexes with non-steroidal anti-inflammatory drugs as studied by electrospray ionization mass spectrometry

Abstract

Abstract The solutions containing one of the copper salts (CuCl2, Cu(ClO4)2, Cu(NO3)2, and CuSO4) and one of the non-steroidal anti-inflammatory drugs (NSAIDs, ibuprofen, ketoprofen or naproxen) were analyzed by electrospray ionization mass spectrometry. Three of the salts, namely CuCl2, Cu(ClO4)2 and Cu(NO3)2, yielded binuclear complexes of drug:metal stoichiometry 1:2. Existence of the complexes of such stoichiometry has not been earlier observed. For copper(II) chloride the complexes (ions of the type [M-HCOOH+Cu2Cl]+ and [M+Cu2Cl]+, M stands for the drug molecule) were formed in the gas phase. When copper(II) perchlorate or copper(II) nitrate was used, the observed binuclear copper complexes (ions of the type [M-H+Cu2(ClO4)2+CH3OH]+, [M-H+Cu2(ClO4)2]+ and [M-H+Cu2(NO3)2+CH3OH]+, [M-H+Cu2(NO3)2]+) were observed at low cone voltage, thus these complexes must have already existed in the solution analysed. Therefore, such complexes may also exist under physiological conditions.