Gas-phase reactions of a novel chemical ionization reagent, ClMn2+, with polar and nonpolar analytes in a linear quadrupole ion trap

Abstract

A chemical ionization reagent ion, ClMn 2 + , has been identified for the analysis of mixtures of organic compounds since it allows ionization of both polar and nonpolar analytes so that only one product ion, ClMn + adduct of the analyte, is generated without fragmentation. The reagent ion is formed upon ionization of ClMn(CO) 5 via corona discharge in an atmospheric pressure chemical ionization source of a linear quadrupole ion trap mass spectrometer. Volatile analytes were introduced into the ion trap via a reagent mixing manifold. Nonvolatile analytes were deposited on a titanium foil and desorbed usinglaser-induced acoustic desorption (LIAD). Formation of a ClMn + adduct with no accompanying fragmentation was observed for all analytes, including branched saturated hydrocarbons. Calculations indicate that ClMn + binds to saturated hydrocarbons via an agostic interaction involving the manganese center and a CÀ ÀH bond of the analyte. The reagent ion Mn + was also investigated. This ion forms a stable adduct with most analytes studied. It binds fairly strongly to saturated hydrocarbons via two agostic interactions with two CÀ ÀH bonds instead of insertion into a CÀ ÀH bond. However, it was found to cause fragmentation for alcohols. ClMn(H 2 O) + has been previously shown to ionize most compounds by ClMn + adduct formation but also to yield molecular ions for amines due to their low ionization energies (<8.3 eV). However, electron transfer was not observed upon ionization of amines with the reagents reported here. The CpCo + ion has been reported earlier to ionize most saturated hydrocarbons without fragmentation. However, it induces CÀ ÀC bond cleavages for highly branched alkanes upon ionization. This was not observed for the reagent ions studied here. ClMn 2 + ion is a more universal ionization reagent than Mn + and the previously reported reagent ions due to its ability to ionize analytes with low ionization energies without electron transfer and due to the complete lack of fragmentation for all analytes. Furthermore, based on the examination of six very different analytes, it has no significant bias toward specific types of analytes.

Gas-Phase Reactions of Atomic Gold Cations with Linear Alkanes (C2–C9)

“…2−6 Owing to a lack of ionizable functional groups, low basicity, or accompanying fragmentation, it is a challenging task to find an appropriate reagent ion that can react with alkanes to yield product ions characteristic of the original alkanes for the aim of chemical ionization mass spectrometry (CIMS) analysis. 7−9 In the search for proper reagent ions, the reactivity of bare or ligated transition metal ions, 10−14 such as Mn + , 15 CpCo + (Cp = cyclopentadienyl), 16−18 ClMn 2 + , 15 and ClMn(H 2 O) + , 19−21 toward alkanes has attracted increasing interest. Of considerable interest here are the gold cations Au + , which are typically quite reactive and have been paid much attention, since Wilkins's group found that Au + could react at thermal energies with a number of hydrocarbons and alcohols.…”

“…In the search for proper reagent ions, the reactivity of bare or ligated transition metal ions, − such as Mn + , CpCo + (Cp = cyclopentadienyl), − ClMn 2 + , and ClMn­(H 2 O) + , − toward alkanes has attracted increasing interest. Of considerable interest here are the gold cations Au + , which are typically quite reactive and have been paid much attention, since Wilkins’s group found that Au + could react at thermal energies with a number of hydrocarbons and alcohols. , Henceforth, the property and activity of the Au + ion have been the focus of research, such as extensive studies of gold cation complexation, − the activity of Au + toward C 6 F 5 H, CH 3 X (X = F, Cl, Br, I), − NO, NH 3 , and CS 2 , and endothermic activation of CH 4 , H 2 , O 2 , , and N 2 O .…”

Chemical Ionization of Large Linear Alkanes and Small Oxidized Volatile Organic Compounds by the Reactions with Atomic Gold Cations

“…However, they also have some shortcomings in the VOCs detection, such as no reactivity of NO + toward HCHO and severe fragmentation of large alkanes caused by O 2 + , CF 3 + , and CF 2 H + . To search for better reagent ions, there has been a renewal of interest in the gas-phase chemistry of bare or ligated transition metal ions, − such as Au + , − Mn + , CpCo + (Cp = cyclopentadienyl), − ClMn 2 + , and ClMn­(H 2 O) + . It is noteworthy that gold cations Au + are typically quite reactive to many chemical molecules − due to the strong relativistic effects. − According to our recent exploratory study, Au + was potentially interesting and would be pursued as an appropriate reagent ion to ionize linear alkanes.…”