Reactivity of Cytosine with Alkylmercury Ions in the Gas Phase: the Critical Role of the Alkyl Chain

The gas-phase reactivity towards cytosine (C) of alkylmercury cations CnH2n+1Hg+, and more particularly CH3Hg+, C2H5Hg+, n-C4H9Hg+ t-C4H9Hg+, has been studied for the first time by combining tandem mass spectrometry, infrared multiple photon dissociation spectroscopy (IRMPD) density functional theory (DFT) calculations. Under electrospray conditions, interaction C with derived from chloride compounds gives rise to a single type complex general formula [RHg(C)]+, except t-butylmercury which turned be unreactive. Subsequent MS/MS experiments showed that [RHg]+ ions (R=Me, Et, n-Bu) exhibit peculiar characterized transfer alkyl group, R, nucleobase leading [(C)R]+ ion, accompanied reduction metal loss 0Hg. As length chain increases (n≥2), new fragmentation path protonated is opened, associated elimination Cn,H2n,Hg moiety. This latter process clearly overwhelming n-BuHg+. mechanisms both channels were examined through use IRMPD data in fingerprint region, exploring corresponding potential energy surfaces DFT framework.