We report the first infrared spectra of multiply-charged anions in the gas phase. The spectra of SO(4) (2-)(H(2)O)(n), with n=3-24, show four main bands assigned to two vibrations of the dianionic core, the water bending mode, and solvent libration. The triply degenerate SO(4) (2-) antisymmetric stretch vibration probes the local solvent symmetry, while the solvent librational band is sensitive to the hydrogen bonding network. The spectra and accompanying electronic structure calculations indicate a highly symmetric structure for the n=6 cluster and closure of the first solvation shell at n=12.
A technique for high resolution anion photodetachment spectroscopy is presented that combines velocity map imaging and anion threshold photodetachment. This method, slow electron velocity-map imaging, provides spectral line widths of better than 1 meV. Spectra over a substantial range of electron kinetic energies are recorded in a single image, providing a dramatic reduction of data acquisition time compared to other techniques with comparable resolution. We apply this technique to atomic iodine and the van der Waals cluster I.CO2 as test systems, and then to the prereactive Cl.D2 complex where partially resolved structure assigned to hindered rotor motion is observed.
Compounds with carbon-boron bonds are versatile intermediates for building more complex molecules via the elaboration of the carbon-boron bonds into other carbon-element bonds. The synthesis of carbon-boron bonds by catalytic dehydrogenative borylation of carbon-hydrogen bonds with dialkoxyboranes (RO)2BH is particularly attractive. It has been demonstrated for a variety of carbon-hydrogen bond types but not for the C(sp)-H bonds of terminal alkynes, for which hydroboration of the triple bond is a competing process. We report a new iridium catalyst that is strictly chemoselective for C-H borylation of terminal alkynes. The key to the success of this catalyst appears to be the new ancillary SiNN pincer ligand that combines amido, quinoline, and silyl donors and gives rise to structurally unusual Ir complexes. A variety of terminal alkynes (RC≡C-H) can be converted to their alkynylboronates (RC≡C-Bpin, where pin = pinacolate) in high yield and purity within minutes at ambient temperature.
Infrared multiple photon dissociation spectra for size-selected water cluster anions (H2O)n−, n=15–50, are presented covering the frequency range of 560–1820cm−1. The cluster ions are trapped and cooled by collisions with ambient He gas at 20K, with the goal of defining the cluster temperature better than in previous investigations of these species. Signal is seen in two frequency regions centered around 700 and 1500–1650cm−1, corresponding to water librational and bending motions, respectively. The bending feature associated with a double-acceptor water molecule binding to the excess electron is clearly seen up to n=35, but above n=25; this feature begins to blueshift and broadens, suggesting a more delocalized electron binding motif for the larger clusters in which the excess electron interacts with multiple water molecules.
Although zinc oxide (ZnO), a low-cost and naturally abundant material, has a high theoretical specific capacity of 987 mA h g for hosting lithium ions, its application as an anode material has been hindered by its rapid capacity fading, mainly due to a large volume change (around 228%) upon repeated charge-discharge cycles. Herein, using carbon black (CB) powder as a support, ZnO-carbon black (denoted as ZnO-CB) nanocomposites were successfully fabricated using the atomic layer deposition (ALD) method. This method was able to produce strong interfacial molecular bindings between ZnO nanoclusters and the carbon surface that provide stable and robust electrical contact during lithiation and delithiation processes, as well as ZnO nanoclusters rich in oxygen vacancies (OVs) for faster Li-ion transport. Overall, the nanocomposites were able to deliver a high discharge specific capacity of 2096 mA h g at 100 mA g and stable cyclic stability with a specific capacity of 1026 mA h g maintained after 500 cycles. The composites also have excellent rate capability, and a reversible capacity at a high 1080 mA h g at 2000 mA g. The facile but unique synthesis method demonstrated in this work for producing nanostructures rich in OVs and nanocomposites with strong coupling via interfacial molecular bindings could be extended to the synthesis of other oxide based anode materials and therefore could have general significance for developing high energy density lithium ion batteries.
Ozerov and colleagues describe the synthesis and characterization of linear, twocoordinate, cationic phosphine complexes of monovalent Pd and Pt. Comparison of the structures of these complexes to the neutral, zero-valent analogs revealed significant elongation of the M-P bond upon oxidation. Computational studies offer an explanation for the observed phenomenon, showing that molecularorbital-based arguments alone cannot provide a satisfactory rationalization. HIGHLIGHTS Two-coordinate, cationic complexes of monovalent Pd and Pt are synthesized The monovalent cations possess longer, stronger M-L bonds than their zero-valent analogs Theoretical consideration of electrostatic and Pauli effects offers an explanation MacInnis et al., Chem 1, 902-920 December 8, 2016 ª 2016 Elsevier Inc. http://dx.SUMMARY One-electron oxidation of known ( t Bu 3 P) 2 M (1, M = Pd; 2, M = Pt) with [Ph 3 C] [HCB 11 Cl 11 ] leads to two-coordinate, monovalent cations of the formula [( t Bu 3 P) 2 M][HCB 11 Cl 11 ] (3, M = Pd; 4, M = Pt), which also possess linear geometry but with elongated M-P bonds. Spectroscopic and computational studies consistently show that the unpaired electron of the d 9 configuration of 3 and 4 belongs to largely non-bonding orbitals: the s/d z2 hybrid for Pd and the degenerate d x2-y2 /d xy pair for Pt. We show that molecular-orbital-based arguments alone are incapable of predicting or rationalizing the observed M-P bond lengthening on oxidation; correct prediction and rationalization are achieved only by inclusion of electrostatic and Pauli effects. This emphasizes the dangers of interpreting any perturbative changes in bond metrics solely on the basis of energies and occupancies of molecular orbitals; the inclusion of electrostatic and Pauli components is essential to providing a more complete picture. 7 8 9 10 Scheme 1. Synthesis and Reactivity of Pd(I) and Pt(I) Complexes
Coordinated copper hydroxide centers can play an important role in copper catalyzed water oxidation reactions. To have a better understanding of the interactions involved in these complexes, we studied the vibrational spectra of D2 tagged CuOH(+)(H2O)n clusters in the OH stretch region. These clusters are generated by electrospray ionization and probed via cryogenic ion vibrational spectroscopy. The results show that the copper center in the n = 3 clusters has a distorted square planar geometry. The coordination in CuOH(+)(H2O)n is therefore more akin to Cu(2+)(H2O)n with four ligands in the first solvation shell than Cu(+)(H2O)n with two ligands in the first solvation shell. There is also no evidence of any strong axial ligand interactions. The well-resolved experimental spectra enabled us to point out some discrepancies in the calculated spectra, which were found to be highly dependent on the level of theory used.
CrGeTe3 recently emerges as a new two-dimensional (2D) ferromagnetic semiconductor that is promising for spintronic device applications. Unlike CrSiTe3 whose magnetism can be understood using the 2D-Ising model, CrGeTe3 exhibits a smaller van der Waals gap and larger cleavage energy, which could lead to a transition of magnetic mechanism from 2D to 3D. To confirm this speculation, we investigate the critical behavior of CrGeTe3 around the second-order paramagnetic-ferromagnetic phase transition. We obtain the critical exponents estimated by several common experimental techniques including the modified Arrott plot, Kouvel-Fisher method and critical isotherm analysis, which show that the magnetism of CrGeTe3 follows the tricritical mean-field model with the critical exponents β, γ, and δ of 0.240±0.006, 1.000±0.005, and 5.070±0.006, respectively, at the Curie temperature of 67.9 K. We therefore suggest that the magnetic phase transition from 2D to 3D for CrGeTe3 should locate near a tricritical point. Our experiment provides a direct demonstration of the applicability of the tricritical mean-field model to a 2D ferromagnetic semiconductor.
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