Gas‐phase fragmentation of metal adducts of alkali‐metal oxalate salts

Upon collisional activation, gaseous metal adducts of lithium, sodium and potassium oxalate salts undergo an expulsion of CO₂, followed by an ejection of CO to generate a product ion that retains all three metals atoms of the precursor. Spectra recorded even at very low collision energies (2 eV) showed peaks for a 44‐Da neutral fragment loss. Density functional theory calculations predicted that the ejection of CO₂ requires less energy than an expulsion of a Na⁺ and that the [Na₃CO₂]⁺ product ion formed in this way bears a planar geometry. Furthermore, spectra of [Na₃C₂O₄]⁺ and [³⁹K₃C₂O₄]⁺ recorded at higher collision energies showed additional peaks at m/z 90 and m/z 122 for the radical cations [Na₂CO₂]^+? and [K₂CO₂]^+?, respectively, which represented a loss of an M^? from the precursor ions. Moreover, [Na₃CO₂]⁺, [³⁹K₃CO₂]⁺ and [Li₃CO₂]⁺ ions also undergo a CO loss to form [M₃O]⁺. Furthermore, product‐ion spectra for [Na₃C₂O₄]⁺ and [³⁹K₃C₂O₄]⁺ recorded at low collision energies showed an unexpected peak at m/z 63 for [Na₂OH]⁺ and m/z 95 for [³⁹K₂OH]⁺, respectively. An additional peak observed at m/z 65 for [Na₂¹⁸OH] ⁺ in the spectrum recorded for [Na₃C₂O₄]⁺, after the addition of some H₂¹⁸O to the collision gas, confirmed that the [Na₂OH] ⁺ ion is formed by an ion–molecule reaction with residual water in the collision cell. Copyright © 2014 John Wiley & Sons, Ltd.     

Dinuclear Ruthenium(II) Complexes as Two‐Photon,Time‐Resolved Emission Microscopy Probes for Cellular DNA

The first transition‐metal complex‐based two‐photon absorbing luminescence lifetime probes for cellular DNA are presented. This allows cell imaging of DNA free from endogenous fluorophores and potentially facilitates deep tissue imaging. In this initial study, ruthenium(II) luminophores are used as phosphorescent lifetime imaging microscopy (PLIM) probes for nuclear DNA in both live and fixed cells. The DNA‐bound probes display characteristic emission lifetimes of more than 160 ns, while shorter‐lived cytoplasmic emission is also observed. These timescales are orders of magnitude longer than conventional FLIM, leading to previously unattainable levels of sensitivity, and autofluorescence‐free imaging.     

Computational thermochemistry of glycolaldehyde

We use a variant of the focal point analysis to refine estimates of the relative energies of the four low‐energy torsional conformers of glycolaldehyde. The most stable form is the cis‐cis structure which enjoys a degree of H‐bonding from hydroxyl H to carbonyl O; here dihedral angles τ₁ (O?C? C? O) and τ₂ (C? C? O? H) both are zero. We optimized structures in both CCSD(T)/aug‐cc‐pVDZ and aug‐cc‐pVTZ; the structures agree within 0.01 Å for bond lengths and 1.0 degrees for valence angles, but the larger basis brings the rotational constants closer to experimental values. According to our extrapolation of CCSD(T) energies evaluated in basis sets ranging to aug‐cc‐pVQZ the trans‐trans form (180°, 180°) has a relative energy of 12.6 kJ/mol. The trans‐gauche conformer (160°, ±75°) is situated at 13.9 kJ/mol and the cis‐trans form (0°, 180°) at 18.9 kJ/mol. Values are corrected for zero point vibrational energy by MP2/aug‐cc‐pVTZ frequencies. Modeling the vibrational spectra is best accomplished by MP2/aug‐cc‐pVTZ with anharmonic corrections. We compute the Watsonian parameters that define the theoretical vibrational‐rotational spectra for the four stable conformers, to assist the search for these species in the interstellar medium. Six transition states are located by G4 and CBS‐QB3 methods as well as extrapolation using energies for structures optimized in CCSD(T)/aug‐cc‐pVDZ structures. We use two isodesmic reactions with two well‐established thermochemical computational schemes G4 and CBS‐QB3 to estimate energy enthalpy and Gibbs energy of formation as well as the entropy of the gas phase system. Our extrapolated electronic energies of species appearing in the isodesmic reactions produce independent values of thermodynamic quantities consistent with G4 and CBS‐QB3. © 2013 Wiley Periodicals, Inc.     

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Existence and comparison results for noncoercive and nonmonotone multivalued elliptic problems

We consider noncoercive quasilinear elliptic inclusions under multivalued flux boundary conditions involving multifunctions of Clarke’s generalized gradient. Our main goal is to provide existence and comparison results which are based on an appropriate generalization of the notions of subsolutions and supersolutions. Furthermore, compactness and extremality results of the solution set enclosed by an ordered pair of sub–supersolutions will be proved.