title: Gas-phase kinetic measurements of the ligation of Ni+, Cu+, Ni(pyrrole)1,2+ and Cu(pyrrole)1,2+ with CO2, D2O, NH3 and NO.
abstract: The rate and equilibrium kinetics of the reactions of the biologically important metal species M(+), M(+)(pyrrole) and M(+)(pyrrole)(2) (M = Ni, Cu) have been investigated with the biological gases CO(2), D(2)O, NH(3) and NO in the gas phase at 295 +/- 2 K in helium buffer-gas at a pressure of 0.35 +/- 0.01 Torr. The measurements were taken with an Inductively Coupled Plasma/Selected-Ion Flow Tube (ICP/SIFT) tandem mass spectrometer. Only ligation was observed for the reactions of bare Ni(+) and Cu(+) with CO(2), D(2)O and NH(3) with rates consistent with the known strengths of the resulting ligand-metal bonds. Both metal cations appeared to be oxidized and produce N(2)O in interesting reactions that are second order in NO. One pyrrole ligand was observed to increase the rate of ligation by as much as a factor of 100 and to switch off the oxidation with NO. Equilibrium was achieved for the ligation of CO(2), D(2)O and NO to both Ni(+)(pyrrole) and Cu(+)(pyrrole), and so it was possible to determine absolute values for the standard free energies of ligation. No ligand substitution was observed with M(+)(pyrrole). M(+)(pyrrole)(2) was observed to be generally unreactive towards the small molecules investigated: a notable exception is ammonia. Very fast ligand substitution reactions were observed for reactions of M(+)(pyrrole)(2) with NH(2).
authors.affiliation: Department of Chemistry, Centre for Research in Mass Spectrometry and Centre for Research in Earth and Space Science, York University, Toronto, Ontario, Canada, M3J 1P3.
authors.forename: Michael J Y
authors.initials: MJ
authors.lastname: Jarvis
authors.forename: Voilav
authors.initials: V
authors.lastname: Blagojevic
authors.forename: Gregory K
authors.initials: GK
authors.lastname: Koyanagi
authors.forename: Diethard K
authors.initials: DK
authors.lastname: Bohme
mesh_terms: D000641:Ammonia / Q000737:chemistry*; D002245:Carbon Dioxide / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D017666:Deuterium Oxide / Q000737:chemistry*; D005740:Gases / Q000737:chemistry; D007700:Kinetics; D008024:Ligands; D013058:Mass Spectrometry / Q000295:instrumentation / Q000379:methods; D009532:Nickel / Q000737:chemistry*; D009569:Nitric Oxide / Q000737:chemistry*; D011758:Pyrroles / Q000737:chemistry
chemical_list: D005740:Gases; D008024:Ligands; D011758:Pyrroles; D002245:Carbon Dioxide; D009569:Nitric Oxide; D000641:Ammonia; D003300:Copper; D009532:Nickel; D017666:Deuterium Oxide