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126 Poulter, Charles DaleIsoprenyl diphosphate synthases: protein sequence comparisons, a phylogenetic tree, and predictions of secondary structureIsoprenyl diphosphate synthases are ubiquitous enzymes that catalyze the basic chain-elongation reaction in the isoprene biosynthetic pathway. Pairwise sequence comparisons were made for 6 farnesyl diphosphate synthases, 6 geranylgeranyl diphosphate synthases, and a hexaprenyl diphosphate synthase...Catalytic site; Evolution; Farnesyl diphosphate; Geranylgeranyl diphosphate; Prenyltransferase; Substrate binding:1994
127 Armentrout, Peter B.Kinetic energy dependence of Al+ + O2→AlO+ + OThe endothermic reaction of Al+ with O2 is studied using a guided ion-beam apparatus. The reaction cross section is measured as a function of kinetic energy from 0 to 20 eV. The threshold energy for the reaction, E0, is determined from an empirical model to be 3.64 ± 0.04 eV.Ion-molecule reactions; Translational energy; Threshold behavior; Endothermic reactions; Aluminum; Oxygen1986
128 Armentrout, Peter B.Kinetic energy dependence of association reactions. A new thermokinetic method for large systemsThe reactions of bare alkali metal ions (M+5Li+, Na+, or K+) with dimethoxyethane (CH3OCH2CH2OCH3 , (DXE) are studied using guided ion beam tandem mass spectrometry. The bimolecular reaction forms an associative M1(DXE) complex that is long-lived and dissociates back to the reactants. The kinetic en...Collision-induced dissociation; Association reactions; Bond energies; Dimethoxyethane; Alkali metal ions2003
129 Armentrout, Peter B.Kinetic energy dependence of dissociative charge-transfer reactions of He+, Ne+, Ar+, Kr+, and Xe+ with silaneGuided ion-beam techniques are used to measure the cross sections as a function of kinetic energy for reaction of SiH4 with He +, Ne +, Ar +, Kr +, and Xe +. State-specific data for the 2P3/2 ground spin-orbit states of Kr+ and Xe+ are also obtained.Silane; Charge-transfer reactions; Ion-molecule reactions; Ion energy; Rare gas ions; Plasma systems1990
130 Armentrout, Peter B.Kinetic-energy dependence of competitive spin-allowed and spin-forbidden reactions: V++CS2The kinetic-energy dependence of the V++CS2 reaction is examined using guided ion-beam mass spectrometry. Several different ion sources are used to systematically vary the V+ electronic state distributions and elucidate the reactivities of both the ground and excited state V+ cation.Carbon disulfide; Vanadium ions; Transition metal ions; Bond energies; Endothermic reactions; Exothermic reactions1999
131 Morse, Michael DavidLaser excitation spectroscopy of the A and B states of jet-cooled copper dimer: evidence for large electronic isotope shiftsFluorescence excitation spectra recorded for the A-X system of jet-cooled Cu2 show conclusive evidence of a ?? = 0 transition, and the A state is thereby definitively assigned as ??u+. A previous assignment of the B state as ??u+ is confirmed, but the vibrational levels of this state are complicated...1989
132 Morse, Michael DavidLaser vaporization generation of Y ??B+, Y ??B+, and YAI+ for electron spin resonance studies in neon matrices at 4 K: comparison with theoretical calculationsThe first spectroscopic investigation of 89Y 10B+, 89Y 11B+, and 89Y 27Al+ is reported, revealing that both of these diatomic cation radicals have X 4?- electronic ground states. The ions were generated by three high energy techniques in combination with neon matrix isolation at 4 K and studied by e...1992
133 Morse, Michael DavidLaser vaporization generation of the SiB and SiAi radicals for matrix isolation electron spin resonance studies: comparison with theoretical calculations and assignment of their electronic ground states as X ??The first experimental spectroscopic study of the SiB and SiAl diatomic radicals is reported. Electron spin resonance results indicate that both molecules have X 4? ground electronic states, in agreement with earlier theoretical calculations. The SIB and SiAl radicals were generated in neon matrices...1993
134 Miller, Joel Steven; Epstein, Arthur J.Lattice- and spin-dimensionality crossovers in a linear-chain-molecule-based ferrimagnet with weak spin anisotropy[MnOEP][HCBD], a member of the metalloporphyrin family of donor-acceptor molecule-based magnets, consists of isolated ferrimagnetic chains of alternating S=2, [MnOEP], and s=1/2, [HCBD] units (OEP=octaethylporphyrinato and HCBD=hexacyanobutadiene). Analysis of the exchange pathways reveals an exchan...Magnetic; Magnetization; Interchain1997
135 Poulter, Charles DaleLethal mutations in the isoprenoid pathway of salmonella entericaEssential isoprenoid compounds are synthesized using the 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway in many gram-negative bacteria, some gram-positive bacteria, some apicomplexan parasites, and plant chloroplasts. The alternative mevalonate pathway is found in archaea and eukaryotes, includin...Isoprenoids; Mutation; Bacteria; Antimicrobials2006
136 Morse, Michael DavidLigand-field theory applied to diatomic transition metals. Results for the d?Ad?B?? states of Ni?, the d?Nid??cu?? states of NiCu, and the d?Ni(?F)d??cu???*? excited states of NiCuA ligand-field theory has been developed for transition-metal diatomics having electronic configurations of d?Ad??B??, d?Ad?B?? and d?A(?F)d??B???*?. The theory treats each atom as a point charge and includes spin-orbit interactions. No contributions due to d-orbital chemical bonding are included. ...1992
137 Miller, Joel Steven; Epstein, Arthur J.Linear chain ferromagnetic charge transfer compoundsCharge transfer complexes possessing a ... DADA ... structure with both the donor, D, and acceptor, A, being S = 1/2 radicals may exhibit cooperative magnetic phenomena. The complex [Fe(C5Me5)2]+ [TCNQ]-. exhibits metamagnetic behavior. The similarly structured [TCNE]-. and [C4(CN)6]-. complexes ar...Spin; Exchange; Molecular1986
138 Miller, Joel Steven; Epstein, Arthur J.Local structural order in the disordered vanadium tetracyanoethylene room-temperature molecule-based magnetWe determined the vanadium oxidation state and local coordination environment in disordered samples of magnetic V[TCNE]x(x=2) prepared by chemical vapor deposition (CVD). Systematic studies of the x-ray absorption near-edge structure (XANES) in this material and reference compounds show that V ions ...Magnetic; Solvent; Structure2004
139 Miller, Joel Steven; Epstein, Arthur J.Magnetic behavior of octaethylporphyrinatomanganese(III) tetracyanoethenide, [MnOEP][TCNE], and hexacyanobutadienide, [MnOEP][C4(CN)6]: the importance of a uniform chain for stabilizing strong effective ferromagnetic coupling[MnOEP][A] {A=[TCNE]'- and [C4(CN)6]'-} have been isolated as extended 1D coordination polymers with trans-U2"[A] bridging ligands with strong {A=[C4(CN)6].-} and weak {A=TCNE].-} ferromagnetic coupling as evidenced from the fit of the magnetic susceptibility to the Curie-Weiss law (0=5.1 and 67.1 K...Crystals; Inversion; Coupling1995
140 Miller, Joel StevenMagnetic behaviors of the metamagnetic and ferromagnetic phases of [Fe(C5Me5)2][TCNQ] (TCNQ = 7,7,8,8-tetracyano-p-quinodimethane). Determination of the phase diagram for the metamagnetic phaseThe detailed magnetic behaviors of the ferro- (1FO) and metamagnetic (1MM) phases of [FeCp*2][TCNE] (Cp* = pentamethylcyclopentadienide; TCNE = tetracyanoethylene) aligned parallel to the applied magnetic field, H, were obtained using eicosane (E). The Tc for 1FO is 3.1 K from the maximum in the fr...Properties; Temperature; Ordering2006
141 Miller, Joel Steven; Epstein, Arthur J.Magnetic bistability and nucleation of magnetic bubbles in a layered 2D organic-based magnet [Fe(TCNE)(NCMe)2][FeC14]The 2D layered organic-based magnet [Fe(TCNE)(NCMe)2][FeCl4] (TCNE ¼ tetracyanoethylene) exhibits a unique macroscopic magnetic bistability between the field-cooled and zero-field-cooled states, which cannot be explained by either superparamagnetic behavior or spin freezing due to spin glass orde...Organic-based magnets; Tetracyanoethylene; Magnetic bistability; Nucleation2008-11
142 Miller, Joel Steven; Epstein, Arthur J.Magnetic phase diagram of a molecule-based ferrimagnet: weak ferromagnetism and multiple dimensionality crossoversA detailed study of the magnetic behavior of the molecule-based magnet, [MnOEP][HCBD], (OEP=mesooctaethylporphyrinato, HCBD=hexacyanobutadiene) from 1.7 to 20 K was performed. The earlier reported magnetic transition at 19.6 K, ascribed to a crossover from a one-dimensional Heisenberg-like ferrimag...Transition; Temperature; Magnetization1997
143 Miller, Joel Steven; Epstein, Arthur J.Magnetic properties and critical behavior of Fe(tetracyanoethylene) 2.x(CH2Cl2): a high-Tc molecule-based magnetWe report magnetic studies of Fe(TCNE)2•x(CH2Cl2), a member of the family of high-Tc molecule-based magnets, M(TCNE)x•y (solvent) (M=V, Mn, TCNE=tetracyanoethelyne). Based on extensive static and dynamic magnetic measurements we show that this system has a complex magnetic behavior, with a mixtu...Solvent; Anisotropy; Spin2000
144 Miller, Joel StevenMagnetically ordered molecule-based assembliesThe development of molecules and assemblies of molecules exhibiting technologically important bulk properties, such as magnetic ordering, is an important worldwide research focus. Organic- and molecule-based magnets have been discovered and several families have been reported with magnetic orderin...Organic-based; Lattices; Magnets2006
145 Miller, Joel Steven; Epstein, Arthur J.Magnetization and dynamics of reentrant ferrimagnetic spin-glass [MnTPP]::+[TCNE].-.2PhMeWe present direct current (dc) magnetization M(T,H) and alternating current (ac) susceptibility Xac(T,H,f) data for the quasi-one-dimensional molecule-based ferrimagnet [MnTPP]::+[TCNE].-.•2PhMe (TPP=meso-tetraphenylporphyrinato, TCNE=tetracyanoethylene). Static scaling of the real part X' of ...Ferrimagnetic order; Magnetism1996
146 Miller, Joel StevenMagnetization and static scaling of high-Tc disordered molecular-based magnet V(tetracyanoethylene)x¢y(CH3CN) with x ~ 1.5 and y ~ 2)We report field (H) and temperature (T) -dependent magnetization (M) of a member of the new class of high-Tc molecular-based magnets V(tetracyanoethylene)x .y(solvent) with Tc in an accessible range (solvent =CH3CN). The M (H) at low T saturates slowly with increasing H. The random magnetic anisotro...Temperature; Magnetic; Random1993
147 Miller, Joel StevenManganese(II)octabutoxynaphthalocyanine and its ferrimagnetic electron-transfer salt with TCNEThe magnetic susceptibility (x) of 1,6,10,15,19,25,28,32- octa-n-butoxynaphthalocyaninatomanganese(III) tetracyanoethanide can be fit to a Curie-Weiss expression with O=54 K for T>150 K, and the xT(T) data are consistent with linear chains and can be fit to a Seiden expression for alternating S=2 a...Magnetic; Ordering; Magnetization2000
148 Armentrout, Peter B.Mechanism of proton exchange: guided ion beam studies of the reactions, H(H2O)n+ (n=1-4) + D2O and D(D 2O)n+ (n=1-4) + H2OReactions of protonated water clusters, H(H2O)n+ (n=1-4) with D2O and their "mirror" reactions, D(D2O)n+ (n=1-4) with H2O, are are studied using guided-ion beam mass spectrometry. Absolute reaction cross sections are determined as a function of collision energy from thermal energy to over 10 eV.Collision-induced dissociation; Proton exchange; Protonated water clusters; Exothermic reactions; Deuterium oxide2004
149 Armentrout, Peter B.Methane activation by cobalt cluster cations, Con+ (n=2-16): reaction mechanisms and thermochemistry of cluster-CHx (x=0-3) complexesThe kinetic energy dependences of the reactions of Con + (n=2-16) with CD4 are studied in a guided ion beam tandem mass spectrometer over the energy range of 0-10 eV. The main products are hydride formation, ConD+, dehydrogenation to form ConCD2 +, and double dehydrogenation yielding ConC+.Cobalt ions; Transition metal ions; Bond energies; Endothermic reactions; Dehydrogenation; Deuterated methane2009
150 Armentrout, Peter B.Methane activation by nickel cluster cations, Nin+ (n=2-16): reaction mechanisms and thermochemistry of cluster-CHx (x=0-3) complexesThe kinetic energy dependences of the reactions of Nin+ (n=2-16) with CD4 are studied in a guided ion beam tandem mass spectrometer over the energy range of 0-10 eV. The main products are hydride formation NinD1, dehydrogenation to form NinCD2 1 , and double dehydrogenation yielding NinC1.Nickel ions; Metal clusters; Deuterated methane; Collision-induced dissociation; Endothermic reactions; Bond energies; Dehydrogenation2004
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