Influence of experimental conditions on electrospray/ionization (ESI) mass spectra of ferrocene derivatives FcCHRAz (Fc = eta5-C5H5-Fe-eta5- C5H4; R = H, Az = benzimidazole; R = Ph, Az = 2-methylimidazole) has been investigated. The spectra of all the compounds revealed [M]+*, product of its fragmentation [FcCHR]+ as well as products of ion/molecular interactions (protonated molecule [MH]+, binuclear ion [(FcCHR)2 Az]+, dimeric ion [M2]+* and its protonated form [M2H]+). Relative abundances of these ions appreciably (more than one order) depend on experimental conditions: analyte concentration, temperature of heated capillary, spray voltage, flow rate of mobile phase and polarity of solvents. Established correlations allow the selection of optimum experimental conditions for registration of ESI mass spectra, as required by the application. If an unknown compound is to be identified, it is necessary to operate by using polar solvents, small concentration, low temperature of heated capillary, high spray voltage and flow rates. There are high-intensity binuclear and protonated dimeric ions in mass spectra under other conditions. It can give rise to wrong interpretation of the structure of investigated compound. At the same time, for study of ion-molecular processes by ESI-MS it is necessary to use concentrated samples in non-polar solvents. In this case the dependence of reaction products yields on temperature and flow rate of mobile phase must be investigated.

No abstract

The formation of molecular ions of ferrocene is detected under the «inverse» conditions of electrospray ionization where the pure solvent alone is electrosprayed in the presence of fer rocene vapor. The quantum chemical calculations using the B3LYP/LanL2DZ method suggest that the ferrocene oxidation occurs in the gas phase and follows the mechanism of activating protonation where a protonated molecule acts as an oxidant for another ferrocene molecule.

The electrospray ionization behavior of some ferrocenylalkylazoles CpFeC 5 H 4 CH(R)Az (AzH are derivatives of imidazole, pyrazole, triazole and their benzo analogs; R = H, Me, Et, Ph), ferrocenylalkanols CpFeC 5 H 4 CH(R)OH (R = H, Me), and mixtures of the latter with azoles was studied. The electrospray ionization mass spectra of these compounds, in addition to the molecular ion [M] +• , the protonated molecule [M + H] + , and ferrocenylalkyl cation [FсCHR] + peaks, exhibit also intensive peaks for the binuclear ions [(FcCHR) 2 Х] + (Х = Az or O), resulting from ferrocenylalkylation of the initial compounds with the ferrocenylalkyl cations. Electrospray ionization of an equimolar mixture of ferrocenylmethanol FcCH 2 OH and imidazole gives the protonated ferrocenylmethylimidazole molecule [FcCH 2 Im + H] + and the [FcCH 2 (Im) 2 + H] + dimer, apart from the ions typical of each component, i.e., ferrocenylalkylation of azoles with the ferrocenylalkylcarbinols, known in the chemistry of solutions, takes place under electrospray conditions.

No abstract