Acceptorless dehydrogenation of ethane was achieved in the gas phase via a two-step catalytic cycle involving ternary cationic metal hydrides, [(phen)­M­(H)]+, 1, and metal ethides, [(phen)­M­(CH2CH3)]+, 2, (where M = Ni, Pd, or Pt, and phen = 1,10-phenanthroline). Species 1 and 2 were generated and their reactivity studied in a quadrupole ion trap mass spectrometer. It was found that 1 readily reacted with ethane releasing H2 and forming 2, with the relative reactivity being Pt > Ni ≫ Pd. Density functional theory (DFT) calculations for this metathesis reaction agree with the experimental reactivity order. Species 2 can in turn be converted into 1 and release ethylene when sufficient energy is supplied via collision-induced dissociation. DFT calculations also provided insight into competing side reactions (e.g., dehydrogenation of 2 and formation of protonated phen ligand) that become competitive during this endothermic step. The catalytic cycle can be repeated in the mass spectrometer several times. Multiple entry points into the cycle have been identified and discussed.

Background/Aims: In an antiglomerular basement membrane glomerulonephritis (GN) model, GN-resistant Lewis (LEW) rats naturally recover from early glomerular inflammation (days 21–23). We have previously identified a glomeruli-infiltrating CD8α⁺CD11^highMHC II⁺ cell (GIL CD8α⁺ cell) in GN-prone Wistar Kyoto (WKY) rats, which terminates glomerular inflammation through inducing T cell apoptosis prior to glomerular fibrosis at days 35–40. We investigated if GIL CD8α⁺ cells were also associated with the recovery in LEW rats. Methods: GIL CD8α⁺ cells in LEW rats were characterized; their infiltration was observed in connection with T cell apoptosis in glomeruli. Results: An influx of GIL CD8α⁺ cells into inflamed glomeruli was confirmed in the immunized LEW rats at days 17–22, which was much earlier than days 28–35 in WKY rats. Notably, LEW rats had a GIL CD8α⁺CD11^high subpopulation after day 17, while WKY rats lacked this population until after day 30. Analyses further revealed a large number of clustered apoptotic CD4⁺ or CD3⁺ T cells in the glomeruli during recovery (day 23) in LEW rats, as compared to day 35 (transition to fibrosis) in WKY rats. Thus, infiltration of GIL CD8α⁺ cells coincided with decline of glomerular inflammation and T cell apoptosis during recovery in LEW rats. Isolated GIL CD8α⁺ cells were able to infiltrate glomeruli in both WKY and LEW rats at day 20. Conclusion: Our data revealed a strong association between GIL CD8a+ cells and recovery from early glomerular inflammation. It raises a possibility of involvement of GIL CD8a+ cells in the recovery.

The ternary Pd complexes [(phen)­Pd­(H)]+ (1-Pd) and [(phen)­Pd­(CH3)]+ (5-Pd) (where phen = 1,10-phenanthroline) both react with hexane in a linear ion trap mass spectrometer, forming the C–H activation product [(phen)­Pd­(C6H11)]+ (3-Pd) and releasing H2 and CH4, respectively. Density functional theory (DFT) calculations agree well with the experiments in predicting low barriers for these reactions proceeding via a metathesis mechanism. Species 3-Pd undergoes extensive fragmentation, or “cracking”, of the hydrocarbon chain when sufficient energy is supplied via collision-induced dissociation (CID), resulting in the extrusion of a mixture of alkenes, methane, and hydrogen. DFT calculations show that Pd “chain-walking” from α (terminal carbon) to β and from β to γ positions can proceed with barriers sufficiently below those required for chain “cracking”. The fragmentation reactions can be made catalytic if 1-Pd and 5-Pd produced by CID of 3-Pd are allowed to react with hexane again. Ni complexes largely mirrored the chemistry observed for Pd. Both 1-Ni and 5-Ni reacted with hexane, forming 3-Ni, which fragmented under CID conditions in a fashion similar to 3-Pd. In contrast, only 5-Pt reacted with hexane to form 3-Pt, which fragmented predominantly via sequential losses of H2.

Using fatty acids as renewable sources of biofuels requires deoxygenation. While a number of promising catalysts have been developed to achieve this, their operating mechanisms are poorly understood. Here, model molecular systems are studied in the gas phase using mass spectrometry experiments and DFT calculations. The coordinated metal complexes [(phen)M(O2CR)]+ (where phen=1,10‐phenanthroline; M=Ni or Pd; R=CnH2n+1, n≥2) are formed via electrospray ionization. Their collision‐induced dissociation (CID) initiates deoxygenation via loss of CO2 and [C,H2,O2]. The CID spectrum of the stearate complexes (R=C17H35) also shows a series of cations [(phen)M(R’)]+ (where R’ < C17) separated by 14 Da (CH2) corresponding to losses of C2H4‐C16H32 (cracking products). Sequential CID of [(phen)M(R’)]+ ultimately leads to [(phen)M(H)]+ and [(phen)M(CH3)]+, both of which react with volatile carboxylic acids, RCO2H, (acetic, propionic, and butyric) to reform the coordinated carboxylate complexes [(phen)M(O2CR)]+. In contrast, cracking products with longer carbon chains, [(phen)M(R)]+ (R>C2), were unreactive towards these carboxylic acids. DFT calculations are consistent with these results and reveal that the approach of the carboxylic acid to the “free” coordination site is blocked by agostic interactions for R > CH3.

As eries of zinc-based catalysts wase valuated for their efficiency in decomposing formic acid into molecular hydrogen and carbon dioxide in the gas phase using quadrupole ion trap mass spectrometry experiments.T he effectiveness of the catalysts in the series [(L)Zn(H)] + ,w here L = 2,2':6',2''-terpyridine (tpy), 1,10-phenanthroline (phen) or 2,2'-bipyrydine( bpy), wasf ound to dependo nt he ligand used, whicht urned out to be fundamental in tuning the catalytic properties of the zinc complex. Specifically, [(tpy)Zn(H)] + displayed the fastest reaction with formic acid proceedingb yd ehydrogenation to produce the zinc formate complex [(tpy)Zn(O 2 CH)] + and H 2 .T he catalysts [(L)Zn(H)] + are reformed by decarboxylating the zinc formate complexes [(L)Zn(O 2 CH)] + by collision-induced dissociation, which is the only reactionc hannel for each of the ligands used. The decarboxylation reactionw as found to be reversible, since the zinc hydride complexes [(L)Zn(H)] + react with carbon dioxide yielding the zinc formate complex. This reactionw as again substantially faster for L = tpy than L = phen or bpy.T he energetics and mechanisms of these processes were modelled using severall evelso fd ensity functional theory (DFT) calculations. Experimental results are fully supported by the computational predictions.

<i>Background:</i> In our rat model for anti-GBM GN, severe fibrosis follows glomerular inflammation. A potential role of extracellular matrix protein osteopontin (OPN) in glomerular fibrosis was investigated. <i>Methods:</i> Neutralizing OPN antiserum or control normal serum was injected into the experimental rats at late inflammatory/early fibrotic stage. Glomerular inflammation and fibrosis were determined. <i>Results:</i> OPN antiserum treatment had little effect on glomerular inflammation. However, the antiserum treatment resulted in a significant reduction in number of fibrotic glomeruli (50% of the controls). Histology observation showed that fibrotic tissue in glomeruli of the antiserum treated rats was mild and poorly developed. OPN antiserum treatment resulted in downregulated glomerular expression of collagen 1α1; collagen deposition in the antiserum treated rats reduced to <30% of that for normal serum controls. <i>Conclusion:</i> Neutralization of OPN inhibited progression of fibrosis in vivo when given at early fibrotic stage. Thus, OPN may be a therapeutic target for glomerular fibrosis.

Gas-phase cationic ternary complexes of group 10 metals of the formula [(phen)M(X)] + , where phen = 1,10phenanthroline (M = Ni, Pd, or Pt; and X = H or CH 3 ), react with cyclohexane via C−H activation, forming the respective cyclohexyl species [(phen)M(c-C 6 H 11 )] + . Upon collisional activation, these species undergo two key competing processes: (i) ring opening followed by "cracking" of the hydrocarbon chain leading to extrusion of propylene and ethylene as major products among other hydrocarbons; and (ii) dehydrogenation of the cyclohexyl ring leading to the loss of one, two, or three hydrogen molecules, with subsequent loss of cyclohexenes or benzene. The relative prevalence of these two pathways strongly depends on the metal ion, with Pt preferring dehydrogenation over ring opening. The multiple catalytic cycles operating within both pathways are described. Density functional theory (DFT) calculations are used to shed light on mechanistic aspects associated with the experimental results.

Gas‐phase C―C coupling reactions mediated by Ni (II) complexes were studied using a linear quadrupole ion trap mass spectrometer. Ternary nickel cationic carboxylate complexes, [(phen)Ni (OOCR1)]+ (where phen = 1,10‐phenanthroline), were formed by electrospray ionization. Upon collision‐induced dissociation (CID), they extrude CO2 forming the organometallic cation [(phen)Ni(R1)]+, which undergoes gas‐phase ion‐molecule reactions (IMR) with acetate esters CH3COOR2 to yield the acetate complex [(phen)Ni (OOCCH3)]+ and a C―C coupling product R1‐R2. These Ni(II)/phenanthroline‐mediated coupling reactions can be performed with a variety of carbon substituents R1 and R2 (sp3, sp2, or aromatic), some of them functionalized. Reaction rates do not seem to be strongly dependent on the nature of the substituents, as sp3‐sp3 or sp2‐sp2 coupling reactions proceed rapidly. Experimental results are supported by density functional theory calculations, which provide insights into the energetics associated with the C―C bond coupling step.