Quantum integer-valued polynomials

We define a q-deformation of the classical ring of integer-valued polynomials which we call the ring of quantum integer-valued polynomials. We show that this ring has a remarkable combinatorial structure and enjoys many positivity properties: For instance, the structure constants for this ring with respect to its basis of q-binomial coefficient polynomials belong to \(\mathbb {N}[q]\). We then classify all maps from this ring into a field, extending a known classification in the classical case where \(q=1\).     

Xe+ formation following photolysis of Au-Xe: a velocity map imaging study

The photodissociation dynamics of Au-Xe leading to Xe(+) formation via the Ξ(1∕2)-X(2)Σ(+) (v('), 0) band system (41?500-41?800 cm(-1)) have been investigated by velocity map imaging. Five product channels have been indentified, which can be assigned to photoinduced charge transfer followed by photodissociation in either the neutral or the [Au-Xe](+) species. For the neutral species, charge transfer occurs via a superexcited Rydberg state prior to dissociative ionization, while single-photon excitation of the gold atom in Au(+)-Xe accesses an (Au(+))?-Xe excited state that couples to a dissociative continuum in Au-Xe(+). Mechanisms by which charge transfer occurs are proposed, and branching ratios for Xe(+) formation via the superexcited Rydberg state are reported. The bond dissociation energy for the first excited state of Au(+)-Xe is determined to be ～9720 ± 110 cm(-1).     

Hypervalent Iodine Oxidation of Amines in the Presence of Nitroso Compounds: A Method for the Preparation of Unsymmetrically Substituted Azoxy Compounds

Various amines and amino derivatives such as (tert-butylamine, 4-amino-1,2,4-triazole-p-toluenesulfonamide), and cyanamide, when treated with |(diacetoxy)iodo|benzene in the presence of nitroso compounds (2) yield unsymmetrically substituted azoxy compounds (3).     

Off-resonance laser frequency stabilization using the Faraday effect

We present a simple technique for stabilization of a laser frequency off resonance using the Faraday effect in a heated vapor cell with an applied magnetic field. In particular, we demonstrate stabilization of a 780 nm laser detuned up to 14 GHz from the (85)Rb D(2) 5(2)S(1/2) F = 2 to 5(2)P(3/2) F' = 3 transition. Control of the temperature of the vapor cell and the magnitude of the applied magnetic field allows locking ~6-14 GHz red and blue detuned from the atomic line. We obtain an rms fluctuation of 7 MHz over 1 h without stabilization of the cell temperature or magnetic field.     

Metal-specific interactions of H2 adsorbed within isostructural metal-organic frameworks

Diffuse reflectance infrared (IR) spectroscopy performed over a wide temperature range (35-298 K) is used to study the dynamics of H(2) adsorbed within the isostructural metal-organic frameworks M(2)L (M = Mg, Mn, Co, Ni and Zn; L = 2,5-dioxidobenzene-1,4-dicarboxylate) referred to as MOF-74 and CPO-27. Spectra collected at H(2) concentrations ranging from 0.1 to 3.0 H(2) per metal cation reveal that strongly red-shifted vibrational modes arise from isolated H(2) bound to the available metal coordination site. The red shift of the bands associated with this site correlate with reported isosteric enthalpies of adsorption (at small surface coverage), which in turn depend on the identity of M. In contrast, the bands assigned to H(2) adsorbed at positions >3 ? from the metal site exhibit only minor differences among the five materials. Our results are consistent with previous models based on neutron diffraction data and independent IR studies, but they do not support a recently proposed adsorption mechanism that invokes strong H(2)···H(2) interactions (Nijem et al. J. Am. Chem. Soc.2010, 132, 14834-14848). Room temperature IR spectra comparable to those on which the recently proposed adsorption mechanism was based were only reproduced after contaminating the adsorbent with ambient air. Our interpretation that the uncontaminated spectral features result from stepwise adsorption at discrete framework sites is reinforced by systematic red shifts of adsorbed H(2) isotopologues and consistencies among overtone bands that are well-described by the Buckingham model of molecular interactions in vibrational spectroscopy.     

Solid-phase synthesis of trisubsituted guanidines

The solid-phase library synthesis of trisubstituted guanidines was accomplished. Amines were loaded onto the 4-formyl-3,5-dimethoxyphenoxymethyl linker via reductive amination. Subsequent acylation with Fmoc-4-aminomethylbenzoic acid followed by Fmoc deprotection gave solid-supported primary amines. Alternatively, sulfonylation of resin-bound secondary amines with 4-cyanobenzenesulfonyl chloride followed by borane reduction also gave solid-supported primary amines. Both resins were acylated with isocyanates to furnish solid-supported ureas. Dehydration of ureas with p-toluenesulfonyl chloride in pyridine gave solid-supported carbodiimides. Nucleophilic addition of amines to the carbodiimide bond followed by cleavage off the solid support gave trisubstituted guanidines.     

Enthalpies of ionization for 2,3-diphosphoglyceric acid

A commercial titration calorimeter, modified to measure as little as 2 mcal in 2 mL, was used to perform thermometric titrations on 2,3-diphosphoglyceric acid with both tetraethylammonium hydroxide and sodium hydroxide. The enthalpies of ionization for each of the five ionizable protons on 2,3-diphosphoglyceric acid were derived from calorimetric data to be 0.0±0.3 kcal-mol^?1. Similar titrations with HCl on the penta-anion produced results that are consistent with the values derived from the titrations with base.