Twin peaks: Matrix isolation studies of H2S·amine complexes shedding light on fundamental S-H⋯N bonding.

Noncovalent bonding between atmospheric molecules is central to the formation of aerosol particles and cloud condensation nuclei and, consequently, radiative forcing. While our understanding of O-H⋯B interactions is well developed, S-H⋯B hydrogen bonding has received far less attention. Sulfur- and nitrogen-containing molecules, particularly amines, play a significant role in atmospheric chemistry, yet S-H⋯N interactions are not well understood at a fundamental level.

Closing the Shell: Gas-Phase Solvation of Halides by 1,3-Butadiene.

Gas-phase solvation of halides by 1,3-butadiene has been studied via a combination of photoelectron spectroscopy and density functional theory. Photoelectron spectra for X ⋯(C H ) (X=Cl, Br, I where n=1-3, 1-3 and 1-7 respectively) are presented. For all complexes, the calculated structures indicate that butadiene is bound in a bidentate fashion through hydrogen-bonding, with the chloride complex showing the greatest degree of stabilisation of the internal C-C rotation of cis-butadiene.

Hydrogen Bonding versus Halogen Bonding: Spectroscopic Investigation of Gas-Phase Complexes Involving Bromide and Chloromethanes.

Hydrogen bonding and halogen bonding are important non-covalent interactions that are known to occur in large molecular systems, such as in proteins and crystal structures. Although these interactions are important on a large scale, studying hydrogen and halogen bonding in small, gas-phase chemical species allows for the binding strengths to be determined and compared at a fundamental level. In this study, anion photoelectron spectra are presented for the gas-phase complexes involving bromide and the four chloromethanes, CH Cl, CH Cl , CHCl , and CCl .

Halide-propene complexes: validated DSD-PBEP86-D3BJ calculations and photoelectron spectroscopy.

Anion photoelectron spectroscopy has been used to determine the electron binding energies of the X⋯CH (X = Cl, Br, I) complexes. To complement the experimental spectra the DSD-PBEP86-D3BJ functional has been employed, following comparison with previously calculated halide/halogen-molecule van der Waals complexes. To validate the functional, comparison between the complex geometries and vertical detachment energies with both experimental and CCSD(T)/CBS data for a suite of halide-molecule complexes is also made.

A tale of two conformers: spectroscopic evidence for halide catalysed formic acid isomerisation.

Halide-formic acid complexes have been studied utilising a combined experimental and theoretical approach. Formic acid exists as two conformers, distinguished by the relative rotation about the C-OH bond. Computational investigation of the formic acid isomerisation reaction between the two conformers has revealed the ability of halide anions to catalyse the formation of, and preferentially stabilise, the higher energy conformer.

Molecules of life: studying the interaction between water and phosphine in argon matrices.

The interaction between water and phosphine isolated in solid argon matrices has been investigated. Infrared spectra of matrices containing water and phosphine, as well as their deuterium and O isotopologues, revealed that a weak hydrogen bonded complex is formed, with an O-H⋯P bonding motif. This was supported by high level calculations, which predict a binding energy of only 5.

Spectroscopic Study of the Br +CH I→I +CH Br S 2 Reaction.

Mass spectrometry and anion photoelectron spectroscopy have been used to study the gas-phase reaction involving and . The anion photoelectron spectra associated with the reaction intermediates of this reaction are presented. High-level CCSD(T) calculations have been utilised to investigate the reaction intermediates that may form as a result of the reaction along various different reaction pathways, including back-side attack and front-side attack.

Photoelectron Spectroscopy and High-Level Ab Initio Calculations of the Iodide-Methylperoxy Radical Complex.

Anion photoelectron spectroscopy has been used to investigate the structure and dynamics of CHOOI van der Waals complexes. Peaks within the photoelectron spectrum are attributed to photodetachment to the perturbed P state of I···CHOO (3.46 eV) and the two P states of bare iodine.

Towards an Understanding of Halide Interactions with the Carbonyl-Containing Molecule CH CHO.

The anion photoelectron spectra of Cl ⋅⋅⋅CD CDO, Cl ⋅⋅⋅(CD CDO) , Br ⋅⋅⋅CH CHO, and I ⋅⋅⋅CH CHO are presented with electron stabilisation energies of 0.55, 0.93, 0.

Spectroscopic Investigation of Chalcogen Bonding: Halide-Carbon Disulfide Complexes.

A combined experimental and theoretical approach has been used to study intermolecular chalcogen bonding. Specifically, the chalcogen bonding occurring between halide anions and CS molecules has been investigated using both anion photoelectron spectroscopy and high-level CCSD(T) calculations. The relative strength of the chalcogen bond has been determined computationally using the complex dissociation energies as well as experimentally using the electron stabilisation energies.

Photoelectron Spectroscopy and Structures of X ⋅⋅⋅CH O (X=F, Cl, Br, I) Complexes.

A combined experimental and theoretical approach has been used to investigate X ⋅⋅⋅CH O (X=F, Cl, Br, I) complexes in the gas phase. Photoelectron spectroscopy, in tandem with time-of-flight mass spectrometry, has been used to determine electron binding energies for the Cl ⋅⋅⋅CH O, Br ⋅⋅⋅CH O, and I ⋅⋅⋅CH O species. Additionally, high-level CCSD(T) calculations found a C minimum for these three anion complexes, with predicted electron detachment energies in excellent agreement with the experimental photoelectron spectra.

A matrix isolation ESR investigation of the MgCH radical.

The MgCH radical and its magnesium-25, carbon-13, and deuterated isotopologs have been isolated in low temperature neon matrices and examined by the matrix isolation electron spin resonance technique for the first time. The radicals were formed through the reactions of laser ablated natural abundance magnesium metal and magnesium-25 enriched magnesium metal with carbon-13 and deuterated isotopologs of acetone. The MgCH radical was shown to have a XΣ ground electronic state, and the magnetic parameters determined for this state were g = 2.

The Structure of CCl in the Gas Phase.

The first experimental evidence of the structure of the CCl gas-phase anion complex is presented in conjunction with results from high-level theoretical calculations. The photoelectron spectrum of the system shows a single peak with a maximum at 4.22 eV.

A matrix isolation ESR investigation of Mg-N.

The adducts formed between Mg with N and Mg with N have been trapped in a solid neon matrix and studied with electron spin resonance (ESR) spectroscopy. These radical species were formed through the interaction of laser ablated magnesium and nitrogen gas. The Mg-N radical species was found to have a ground electronic state of Σ in a linear configuration with discrete coupling to the proximate nitrogen resolved in the spectra.

Matrix Isolation ESR and Theoretical Study of ZnN.

The ZnN, ZnN, ZnN, and ZnN radicals have been formed by the reaction of a plume of zinc metal produced with laser ablation and either ammonia vapor or nitrogen atoms isolated in an inert neon matrix at 4.3 K. The ground electronic state of ZnN was determined to be ∑ using electron spin resonance spectroscopy.

Spectrum of antibacterial activity and mode of action of a novel tris-stilbene bacteriostatic compound.

The spectrum of activity and mode of action of a novel antibacterial agent, 135C, was investigated using a range of microbiological and genomic approaches. Compound 135C was active against Gram-positive bacteria with MICs for Staphylococcus aureus ranging from 0.12-0.

A matrix isolation ESR and theoretical study of MgN.

Matrix isolation experiments have been conducted on the MgN, MgN, MgN, and MgN radicals which were formed by the reaction of a plume of magnesium metal produced with laser ablation and either acetonitrile vapour or nitrogen atoms. The radicals were isolated in an inert neon matrix at 4.3 K and studied with electron spin resonance spectroscopy.

Halide-Nitrogen Gas-Phase Clusters: Anion Photoelectron Spectroscopy and High Level ab Initio Calculations.

The gas phase anion photoelectron spectra are presented for the halide-nitrogen clusters X(-)···(N2)n, where X = Br and I and n ≤ 5. Electron binding energies for each cluster in the halide series are determined, with no evidence observed for first solvation shell closure in either series. High level ab initio calculations at the CCSD(T) level of theory are presented for the anion and neutral halogen-nitrogen complexes.

Inspiration from old dyes: tris(stilbene) compounds as potent gram-positive antibacterial agents.

Herein we describe the preparation and structure-activity relationship studies on range of stilbene based compounds and their antibacterial activity. Two related compounds, each bearing carboxylic acid moieties, exhibit good activity against several bacterial strains, including methicillin-resistant Staphylococcus aureus MRSA (ATCC 33592 and NCTC 10442). Compound 10 was most active against Moraxella catarrhalis with minimum inhibitory concentrations (MICs) of 0.

A comparison of common swabbing materials for the recovery of organic and inorganic explosive residues.

The efficiency of solvent based extraction methods used to remove explosive residues from four different swab types was investigated. Known amounts of organic and inorganic residues were spiked onto a swab surface with acetonitrile or ethanol:water combined with ultrasonication or physical manipulation used to extract the residues from each swab. The efficiency of each procedure was then calculated using liquid chromatography-ultraviolet detection for organic residues and ion chromatography for inorganic residues.

A comparison of solvent extract cleanup procedures in the analysis of organic explosives.

The use of an organic solvent to extract explosive residues from hand swabs and postblast debris inevitably leads to the coextraction of unwanted materials, usually in far greater quantities than any explosive residue. In this study, the extraction efficiency of a number of solvent cleanup procedures including solid-phase extraction (SPE), adsorbent resins such as Chromosorb-104, and traditional materials such as silica and Florisil was calculated using a quantitative liquid chromatography-ultraviolet (LC-UV) detection procedure. The Oasis(®) HLB cartridge outperformed other cleanup procedures, with analyte recoveries approaching 95%, while the Amberlite XAD-7 procedure returned the lowest overall recoveries.

Solar irradiation of the seed germination stimulant karrikinolide produces two novel head-to-head cage dimers.

Karrikinolide is a naturally derived potent seed germination stimulant that is responsible for triggering the germination of numerous plant species from various habitats around the world. We now report that solar irradiation of karrikinolide yields two novel head-to-head cage photodimers with the formation, stability and bioactivity of both presented herein.

Anion photoelectron spectra and ab initio calculations of the iodide-carbon monoxide clusters: I(-)···(CO)(n), n = 1-4.

Anion photoelectron spectra are reported for the iodide-carbon monoxide clusters, with supporting ab initio calculations for the 1:1 dimer anion and neutral complexes. A C(s) minimum geometry is predicted for the anion complex, while for the neutral complex two linear van der Waals minima are predicted differing in the attachment point of the iodine, that is, I···CO and I···OC. The predicted adiabatic photodetachment energy agrees well with the experimental spectrum.

Formation of methanol from methane and water in an electrical discharge.

Matrix isolation FTIR experiments have shown that methanol is a major product when argon gas doped with water and methane is exposed to an electrical discharge and condensed to a solid matrix at 11 K. Experiments with (2)H, (17)O and (18)O-labeled isotopologues show the mechanism for the methanol production is likely to be insertion of an excited oxygen atom in the (1)D state into a C-H bond of a methane molecule. In light of these experiments, the possibility of oxygen atom insertion into methane should be considered as a possible mechanism for the production of methanol in interstellar ices.

Matrix isolation ESR and theoretical studies of metal phosphides.

The ZnP, (67)ZnP, CdP, (111)CdP, and (113)CdP radicals have been formed by laser ablation of the metal with GaP pressed into the metal surface, isolated in an inert neon matrix at 4.3 K and their electronic structure was established using electron spin resonance spectroscopy. The following magnetic parameters were determined experimentally for ZnP/(67)ZnP, g(⊥)=1.