Microhydrated cobalt-nitrate cations [Co(NO 3)(H 2O) n] + ( n = 2, 3) studied by infrared spectroscopy in the gas phase

Abstract

The microhydrated cations [Co(NO 3)(H 2O) n ] + ( n = 2, 3) generated via electrospray ionization of aqueous cobalt(II) nitrate are studied by means of infrared-multiphoton dissociation (IRMPD) spectroscopy in an ion-trap mass spectrometer (IT-MS) at the free electron laser CLIO. While [Co(NO 3)(H 2O) 3] + shows a simple photo-induced fragmentation upon IRMPD, the situation is more complex for [Co(NO 3)(H 2O) 2] + because during storage in the IT-MS the ion associates with background water to afford [Co(NO 3)(H 2O) 3] +, and both species adsorb IR photons in the same range. By means of kinetic modeling, it is demonstrated that also in such a more complicated situation useful insights can be achieved. For all [Co(NO 3)(H 2O) n ] + cations studied ( n = 0–3) in parallel theoretical studies, a bidentate coordination of the nitrato ligand is preferred, and this conclusion finds support by a comparison of the computed and experimental IR spectra. In addition, the binuclear cluster [Co 2(NO 3) 3(H 2O) 3] + is probed by means of IRMPD.