Observing Unimolecular Dissociation of Metastable Ions in FT-ICR:  A Novel Application of the Continuous Ejection Technique

Abstract

The application of the continuous ejection technique to observe unimolecular dissociation of metastable organometallic ions in a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer is demonstrated. A radio-frequency ejection voltage is continuously applied at a frequency corresponding to the exact mass of a metastable adduct ion, [MC6H6 +]* (M = Cr and Mn), formed in the reactions of Cr+ and Mn+ with C6H6. By monitoring the initial metal ion intensity as a function of ion ejection time, metastable ion lifetimes and unimolecular dissociation rate constants are obtained. The bond dissociation energies D 0(Cr+−C6H6) = 1.75 ± 0.1 eV and D 0(Mn+−C6H6) = 1.50 ± 0.1 eV are derived from RRKM modeling and are in excellent agreement with other literature values.

Photoelectron spectroscopic and theoretical studies of Fem−(coronene)n (m=1,2, n=1,2) complexes

“…3͑b͔͒. Thus, the competition between the 2 -and 6 -binding sites is observed again, but this time for the neutral system. The calculated EA a value of 1.02 eV is in excellent agreement with the measured value of 1.06 eV.…”

“…9͑b͔͒ the first electron detachment is from a d z 2 antibonding ␣-MO, thus resulting in a neutral triplet state. In addition, it was also seen that the frontier orbitals of the 2 -coordinated isomer are dominated mostly by nonbonding orbitals mainly located on the metal atom, whereas in the case of the 6 -coordinated isomer, the frontier orbitals are dominated by either antibonding or bonding orbitals. For example, the ␣-͑HOMO-1͒ ͑HOMO stands for highest occupied molecular orbital͒ and ␤-HOMO are both bonding orbitals with bonding characteristics between d z 2 of Fe and orbitals of coronene in ␣-͑HOMO-1͒ and between d yz of Fe and orbitals of coronene in ␤-HOMO.…”

“…The development of laser vaporization techniques has extended the range of gas phase studies of the interaction between metal and organic ligands, further developing our understanding of the delicate and complex interactions present in organometallic complexes. Many experimental [1][2][3][4][5][6][7][8][9][10][11][12] and theoretical studies [13][14][15][16][17] have been reported on transition metal ͑TM͒-benzene systems, including their corresponding anions and cations. These studies showed that TM-benzene clusters could form either a sandwich structure ͑Si, Ti, and V͒ or a so-called "rice-ball"metal cluster core covered by benzene molecules-structure ͑Fe, Co, and Ni͒.…”

Gas‐phase ion thermochemistry in organometallic systems

“…The trend resembles those already encountered with other ligands (see above); i.e., BEs slightly decrease going from V þ to Mn þ and from Co þ to Cu þ , whereas there is a sharp increase from Mn þ to Co þ . By the continuous-ejection technique, Lin et al (1997a) found a value for the Cr þ -C 6 H 6 bond energy in excellent agreement with that reported by Lin & Dunbar (1997). Afterwards, Lin et al (1997b) applied the CE technique to obtain the D8(Cr þ -OC(CH 3 ) 2 ) and D8(Cr þ -OC(CD 3 ) 2 ) BDEs, from the unimolecular dissociation of the Cr þ -acetone and Cr þ -acetone-d 6 complexes.…”

New approach for studying slow fragmentation kinetics in FT-ICR: Surface-induced dissociation combined with resonant ejection

“…RRKM modeling of time-and collision energy-resolved FT-ICR SID data [26,35] enables accurate determination of energy and entropy effects in the gas-phase fragmentation of large ions including even- [31,[36][37][38][39][40][41][42][43][44] and odd-electron peptide ions [45][46][47][48][49], noncovalent complexes [50][51][52][53][54], and organometallic complexes [55]. In the present study, we introduce a new approach for examining the kinetics of large ion fragmentation using FT-ICR SID, which is closely related to earlier studies of metastable ion lifetimes in FT-ICR [56,57]. In this approach, SID is coupled with resonant ejection of selected fragment ions [58,59].…”