The reactivity of ferrocenylalkyl azoles under the conditions of electrospray ionization

Under the conditions of electrospray ionization of ferrocenylalkyl azoles FcCH(R)X (Fc–η5-C5H5Fe-η5-C5H4, R – H, Me, XH – 2-methyl imidazole, pirazole) the processes of oxidation, protonation, fragmentation and ferrocenylalkylation to form, molecular ions [М]+, protonated molecules [М+Н]+, ferrocenylalkyl cations [FсCHR]+ and bisferrocenylalkyl azole cations [(FcCHR)2X]+, respectively, take place. Using special experimental techniques (deuterated solvents, saturation of ionic source of an ESI mass-spectrometer by the vapors of solvents, the experiments under the “inverse” ESI conditions when the solvent is subjected to electrospray in the presence of ferrocenylalkyl derivative vapours) and quantum-chemical calculations at the level of the B3LYP/LanL2DZ theory the scheme of the formation of these ions in a gas phase according to the mechanism of “activating protonation” was suggested. it was found that all these ions are formed through the protonation stage, which is taking place mainly in a gas phase. The key stage is the exothermic process of the protonation of the initial compounds by hydroxonium ions giving rise to protonated [M+H]+ molecules which further oxidize and alkylate ferrocenylalkylazoles to form molecular radical cations and bisferrocenylalkyl azole ions [FcCH(Me)-X-CH(Me)Fc]+. The decomposition of protonated ions with the elimination of the azole molecule gives rise to ferrocenylalkyl cations [FсCHR]+ capable in turn of oxidizing and alkylating the initial compounds.

Under the conditions of electrospray ionization of ferrocenylalkyl azoles FcCH(R)X the processes of oxidation, protonation, fragmentation and ferrocenylalkylation. Using special experimental techniques and quantum-chemical calculations it was found that all these ions are formed through the protonation stage, which is taking place mainly in a gas phase.Figure optionsDownload as PowerPoint slide