Gas‐phase interactions of organotin compounds with cysteine

Abstract

The gas-phase interactions of cysteine with di-organotin and tri-organotin compounds have been studied by mass spectrometry experiments and quantum calculations. Positive-ion electrospray spectra show that the interaction of di- and tri-organotins with cysteine results in the formation of [(R) Sn(Cys-H)] and [(R) Sn(Cys)] ions, respectively. MS/MS spectra of [(R) Sn(Cys-H)] complexes are characterized by numerous fragmentation processes, notably associated with elimination of NH and (C,H ,O ). Several dissociation routes are characteristic of each given organic species. Upon collision, both the [(R) Sn(Gly)] and [(R) Sn(Cys)] complexes are associated with elimination of the intact amino acid, leading to the formation of [(R) Sn] cation. But for the latter complex, two additional fragmentation processes are observed, associated with the elimination of NH and C H O S. Calculations indicate that the interaction between organotins and cysteine is predominantly electrostatic but also exhibits a considerable covalent character, which is slightly more pronounced in tri-organotin complexes. A preferred bidentate interaction of the type -η -S-NH , with sulfur and the amino group, is observed. As for the [(R) Sn(Cys)] complexes, their stability is due to the combination of the hydrogen bond taking place between the amino group and the sulfur lone pair and the interaction between the carboxylic oxygen atom and the metal. Copyright © 2016 John Wiley & Sons, Ltd.

Interactions of Dimethyltin(IV) with Uracil As Studied in the Gas Phase

“…43 Note that we also tried to examine the reactivity of triorganotins with uracil. However, unlike what we observed with cysteine 20 or glycine, 44 we did not detect any complex during these experiments.…”

“…Analysis of the Wiberg bond index (WBO) shows the same trends if one focuses on the same linkage. However, compared to what was observed in the cysteine-DMT complexes, the WBO values are slightly higher, which might point to a less-pronounced electronic transfer between the interacting entities. In fact, while for cysteine the charge transferred to DMT is ∼1.2 e, in terms of natural charge, the electronic transfer in the case of uracil leads to a net charge on the dimethyltin moiety of ∼1.53 e (Table ).…”

“…MS/MS spectra were carried out by introducing nitrogen as collision gas in the second quadrupole at a total pressure of 3x10 -5 mbar, the background pressure being around 10 -5 mbar as measured by the ion gauge located outside the collision cell. However, the pressure inside the collision cell is indeed in the order of 10 mTorr 7 and consequently as discussed previously, 8 IRMPD spectra were recorded in the fingerprint region (1000-1900 cm -1 ) using the beamline of the free electron laser (FEL) of the Centre Laser Infrarouge d'Orsay (CLIO). 9 For the present study, the electron energy of the FEL was set at 44 MeV to optimize the laser power in the frequency region of interest.…”

“…The pressure inside the collision cell being of several milliTorr, 19 MS/MS spectra are very likely obtained under a multiple-collision regime, as discussed previously. 20 b. IRMPD Spectroscopy. During the present IRMPD experiments, the fingerprint region (1000−1900 cm −1 ) was explored using the beamline of the free electron laser (FEL) of the Centre Laser Infrarouge d'Orsay (CLIO).…”

Alkylation of uracil and thymine in the gas phase through interaction with alkylmercury compounds

“…pressure of 3x10 -5 mbar, the background pressure being around 10 -5 mbar as measured by the ion gauge located outside the collision cell. The actual pressure inside the collision cell being of several mTorr [47], MS/MS spectra are very likely obtained under a multiplecollision regime as discussed in previous work [48].…”