Formation of Diclofenac Molecular Ions as the Effect of Cu²⁺—π Interaction under Electrospray Ionization Mass Spectrometry Conditions

Abstract

Solutions containing diclofenac (M) and a copper salt [CuCl2, Cu(ClO4)2, Cu(NO3)2, CuSO4) were analysed by electrospray ionisation mass spectrometry (ESI-MS). Because of the cation-pi interactions in diclofenac-Cu(II) complexes, the diclofenac molecular ion M+* at m/z 295 was formed. It was found that the solvent composition (methanol versus water/methanol) and counter ion strongly affect the M+* ion formation. Formation pathways of ion M+* are discussed.

Formation of Curcumin Molecular Ion under Electrospray Ionisation Conditions in the Presence of Metal Cations

“…27 In this way, organic radical cations are often formed under electrospray ionisation (ESI) conditions and the respective molecular ions M +• are clearly seen in ESI mass spectra. [28][29][30][31][32][33][34][35][36] Under ESI conditions, organic radical cations can be also formed from compounds with low oxidation potential through their oxidation by capillary voltage. 37,38 In this paper it is shown that under ESI conditions, in the simultaneous presence of copper cations and other metal cations, namely Co 2+ , Ni 2+ Mn 2+ , Zn 2+ , the curcumin molecular ion is formed.…”

Oxidation of paracetamol by Cu2+ – formation of the paracetamol radical cation

“…Under these conditions, organic radical cations M +• (oxidizing organic molecule) are clearly seen in the mass spectra obtained. [14][15][16][17][18][19] In this letter, we report the study of paracetamol oxidation by the Cu 2+ cation (formation of the [PAR] +• ion) by ESI-CID-MS/MS and ESI-MS. It is worth adding that oxidation of the paracetamol molecule in the ion source has been already studied under electron-capture negativeion chemical ionization (ECNICI) conditions.…”

Detection of Cu(III)‐containing [Diclofenac–H+CuNO3]+ ion by electrospray ionization mass spectrometry

“…[23][24][25][26][27][28] Recently, it has been demonstrated that a cation-p interaction exists between the diclofenac molecule and the Cu 2+ cation. [29] Detailed analysis of the ESI mass spectra obtained for a solution containing diclofenac and Cu(NO 3 ) 2 revealed the presence of the ion [M-H+CuNO 3 ] + at m/z 419 (M stands for a neutral diclofenac molecule). This is an unusual ion since formally it contains copper in the +3 oxidation state.…”