Competitive Complexation of Gaseous Mn^II by 1,10-Phenanthroline, 2,2‘-Bipyridine, and 4,5-Diazafluorene

Abstract

Complexes of Mn(II) with 1,10-phenanthroline (phen) and 2,2'-bipyridine (bipy) are investigated by means of electrospray ionization (ESI) mass spectrometry. Under the conditions used, [MnL(n)]2+ with n = 2 and 3, [MnL(n)Cl]+ with n = 0-2, and [Mn2L(n)Cl3]+ with n = 2 and 3 are produced (where L = phen or bipy). The collision-induced dissociation (CID) spectra of the mass-selected ions show various dissociation pathways, most notable among them is the reduction of the ligated Mn(II) to Mn(I) by intracomplex electron transfer. CID experiments of mixed-ligand complexes formed upon ESI from solutions which contain both phen and bipy exhibit preferential eliminations of bipy, indicating that bipy is a significantly weaker ligand for Mn(II) than phen. This effect is mainly attributed to the flexibility of the bipy ligand concomitant with thermodynamic control in ion dissociation. To support this hypothesis, mixed complexes with some methylated derivatives as well as those containing 4,5-diazafluorene (daf) are examined also. Interestingly, the differences between the ligands diminish in charge-separation reactions of dicationic Mn(II) complexes, due to the joined operation of thermodynamic as well as kinetic effects. In addition, the complexes [Mn(bipy)]+, [Mn(phen)]+, [Mn(bipy)]2+, [Mn(phen)]2+, and [Mn(bipy)(phen)]2+ are computed using the mPW1PW91 hybrid density functional along with the Stuttgart-Cologne-type pseudopotential and basis-set suite, and relative energies for charge-separation reactions and losses of neutral ligands are evaluated.

C–H Bond Activation ofMethane with Gaseous [(CH3)Pt(L)]+ Complexes (L = Pyridine, Bipyridine, and Phenanthroline)

“…Interestingly, H/D exchange is most pronounced in the case of the bipyridine complex. Although a more profound insight would require much more detailed studies, and preferentially also the inclusion of quantum-chemical treatments, as a plausible explanation we propose that the higher flexibility of the bipy ligand in comparison to phen [27] leads to an increased lifetime of the intermediate methane complexes, which would result in an increased k ex /k diss ratio and thus enhance the amount of H/D exchange.…”

Ligand size distribution of phenanthroline-functionalized polyethylene glycol-iron(II) complexes determined by electrospray ionization mass spectrometry and computer simulation

“…In addition, the collision-induced dissociation (CID) of the Fe(mPEG_phen) 3 2ϩ complex was also studied by tandem mass spectrometry (ESI-MS/MS) and by computer simulation, as well. [1] offers a unique tool for the investigation of metal-containing complexes because it overcomes the propensity of these complex ions to dissociate when transferred from solution into the gas phase [2][3][4][5][6][7][8]. In addition, the gas-phase complex ions of interest can then be selected and subjected to collisioninduced dissociation (CID) to promote the detachment of the intact ligands.…”

“…The ESI-MS/MS intensity distribution of the Fe(mPEG_phen) 2 2ϩ formed from Fe(mPEG_ phen) 3 2ϩ by the loss of an mPEG_phen ligand under CID conditions fits quite well to the calculated one. (J Am Soc Mass Spectrom 2010, 21, 1561-1564) © 2010 American Society for Mass Spectrometry E lectrospray ionization mass spectrometry (ESI-MS) [1] offers a unique tool for the investigation of metal-containing complexes because it overcomes the propensity of these complex ions to dissociate when transferred from solution into the gas phase [2][3][4][5][6][7][8]. In addition, the gas-phase complex ions of interest can then be selected and subjected to collisioninduced dissociation (CID) to promote the detachment of the intact ligands.…”

Growth of Larger Hydrocarbons in the Ionosphere of Titan

“…The vertical axis refers to an intensity of 1 for the parent ion (shifted upwards by 0.5 for the reaction with CD 4 ), the mass-region from m/z 10-40 is amplified by a factor of 50, and the mass-region from m/z 50-120 is amplified by a factor of 10; the application of different factors in low-and high-mass regions is due to the discrimination of light fragment ions in detection. [11,12] Two expanded insets show the isotope patterns of the dicationic CÀC coupling products in the mass range m/z 50-56. The monocations C 2 H 3 + and C 5 H 3 + due to unimolecular dissociation of metastable C 7 H 6 2 + are denoted with an asterix.…”