0000000000062023
AUTHOR
John M. Dyke
A study of the atmospherically important reactions between dimethyl selenide (DMSe) and molecular halogens (X2 = Cl2, Br2, and I2) with ab initio calculations.
The atmospherically relevant reactions between dimethyl selenide (DMSe) and the molecular halogens (X(2) = Cl(2), Br(2), and I(2)) have been studied with ab initio calculations at the MP2/aug-cc-pVDZ level of theory. Geometry optimization calculations showed that the reactions proceed from the reagents to the products (CH(3)SeCH(2)X + HX) via three minima, a van der Waals adduct (DMSe:X(2)), a covalently bound intermediate (DMSeX(2)), and a product-like complex (CH(3)SeCH(2)X:HX). The computed potential energy surfaces are used to predict what molecular species are likely to be observed in spectroscopic experiments such as gas-phase photoelectron spectroscopy and infrared matrix isolation s…
Synthesis and structural characterisation of germanium(II) halide complexes with neutral N-donor ligands.
The Ge(II) complexes [GeX(2)(L-L)] (L-L = 1,10-phen (X = Cl, Br); L-L = Me(2)N(CH(2))(2)NMe(2), 2,2'-bipy (X = Cl)), [GeX(L-L)][GeX(3)] (L-L = 2,2'-bipy (X = Br); L-L = pmdta (MeN(CH(2)CH(2)NMe(2))(2)) (X = Cl, Br)) have been prepared and their crystal structures determined. The crystal structure of [GeCl(2){Me(2)N(CH(2))(2)NMe(2)}] shows a weakly associated centrosymmetric dimer based upon distorted square-pyramidal coordination at Ge(II) and containing asymmetrically chelating diamine ligands. The structure of [GeCl(2)(2,2'-bipy)] contains a chelating 2,2'-bipy ligand and forms a zig-zag chain polymer via long-range intermolecular Ge...Cl bridging interactions, leading to a very distorted…
The gas-phase chemiionization reaction between samarium and oxygen atoms: A theoretical study
The Sm + O chemiionization reaction has been investigated theoretically using a method that allows for correlation and relativistic effects. Potential energy curves have been calculated for several electronic states of SmO and SmO+. Comparison with available spectroscopic and thermodynamic values for these species is reported and a mechanism for the chemiionization reaction Sm + O is proposed. The importance of spin–orbit coupling in the excited states of SmO, in allowing this chemiionization reaction to take place, has been revealed by these calculations. This paper shows the metal-plus-oxidant chemiionization reaction.
A study of the atmospherically important reactions of dimethylsulfide (DMS) with I2 and ICl using infrared matrix isolation spectroscopy and electronic structure calculations.
The reactions of dimethylsulfide (DMS) with molecular iodine (I(2)) and iodine monochloride (ICl) have been studied by infrared matrix isolation spectroscopy by co-condensation of the reagents in an inert gas matrix. Molecular adducts of DMS + I(2) and DMS + ICl have also been prepared using standard synthetic methods. The vapour above each of these adducts trapped in an inert gas matrix gave the same infrared spectrum as that recorded for the corresponding co-condensation reaction. In each case, the infrared spectrum has been interpreted in terms of a van der Waals adduct, DMS : I(2) and DMS : ICl, with the aid of infrared spectra computed for their minimum energy structures at the MP2 lev…
Synthesis, Structures and DFT Calculations on Alkaline-Earth Metal Azide-Crown Ether Complexes
The first examples of azide complexes of calcium, strontium or barium with crown ethers have been prepared and fully characterised, notably [Ba([18]crown-6)(N3)2(MeOH)], [Sr([15]crown-5)(N3)2(H2O)], [Ca([15]crown-5)(N3)2(H2O)] and [Sr([15]crown-5)(N3(NO3)]. Crystal structures reveal the presence of a variety of coordination modes for the azide groups including kappa 1-, mu-1,3- and linkages via H-bonded water molecules, in addition to azide ions. The [Ba([18]crown-6)(N3)2(MeOH)].1/3 MeOH contains dinuclear cations with three mu-1,3-NNN bridges, the first example of this type in main group chemistry. The structures obtained have been compared with molecular structures computed by density fun…
A theoretical study of the gas-phase chemi-ionization reaction between uranium and oxygen atoms
The U+O chemi-ionization reaction has been investigated by quantum chemical methods. Potential-energy curves have been calculated for several electronic states of UO and UO+. Comparison with the available spectroscopic and thermodynamic values for these species is reported and a mechanism for the chemi-ionization reaction U+O -> UO++e(-) is proposed. The U+O and Sm+O chemi-ionization reactions are the first two metal-plus-oxidant chemi-ionization reactions to be studied theoretically in this way.
Unexpected Structural Diversity in Alkali Metal Azide-Crown Ether Complexes: Syntheses, X-ray Structures, and Quantum-Chemical Calculations
A series of alkali metal azide-crown ether complexes, [Li([12]crown-4)(N-3)], [Na([15]crown-5)(N-3)], [Na([15]crown-5)(H2O)(2)]N-3, [K([18]crown-6)(N-3)(H2O)], [Rb([18]crown-6)(N-3)(H2O)], [Cs([18]crown-6)(N-3)](2), and [Cs([18]crown-6)(N-3)(H2O)(MeOH)], has been synthesised. In most cases, single crystals were obtained, which allowed X-ray crystal structures to be derived. The structures obtained have been compared with molecular structures computed by density functional theory (DFT) calculations. This has allowed the effects of the crystal lattice on the structures to be investigated. Also, a study of the M-N-terminal metalazide bond length and charge densities on the metal (M) and termin…
The characterization of molecular alkaly metal azides
Matrix isolation infrared (IR) studies have been carried out on the vaporisation of the alkali-metal azides MN(3) (M = Na, K, Rb and Cs). The results show that under high vacuum conditions, molecular KN(3), RbN(3) and CsN(3) are present as stable high-temperature vapour species, together with variable amounts of nitrogen gas and the corresponding metal atoms. The characterisation of these molecular azides is supported by ab initio molecular orbital calculations and density functional theory (DFT) calculations, and for CsN(3) in particular, by the detection of the isotopomers CS((14)N(15)N(14)N) and Cs((15)N(14)N(14)N). The IR spectra are assigned to a "side-on" (C(2v)) structure by comparis…
ChemInform Abstract: Synthesis, Structures and DFT Calculations on Alkaline-Earth Metal Azide-Crown Ether Complexes.
The first examples of azide complexes of calcium, strontium or barium with crown ethers have been prepared and fully characterised, notably [Ba([18]crown-6)(N3)2(MeOH)], [Sr([15]crown-5)(N3)2(H2O)], [Ca([15]crown-5)(N3)2(H2O)] and [Sr([15]crown-5)(N3)(NO3)]. Crystal structures reveal the presence of a variety of coordination modes for the azide groups including 1-, -1,3- and linkages via H-bonded water molecules, in addition to azide ions. The [Ba([18]crown-6)(N3)2(MeOH)]1/3 MeOH contains dinuclear cations with three -1,3-NNN bridges, the first example of this type in main group chemistry. The structures obtained have been compared with molecular structures computed by density functional th…
Computational Study on Cesium Azide Trapped in a Cyclopeptidic Tubular Structure
The structures and the electronic properties of host-guest complexes formed by a cyclopeptidic tubular aggregate and the species CsN3, CS2(N-3)(2), and CS2N6 have been investigated by means of density functional theory. Taking advantage of the azide property to act as a bridge ligand between two or more metal cations, it may be possible to trap N-3(-) ions inside a confined space. This could be important for the preparation of polynitrogen molecules N-n. Results show that there are significant attractive interactions between the azide ion and the cavity walls, which make the ion stay inside the inner empty space of the cyclopeptidic aggregate. The confinement of the species CS2(N-3)(2) forc…
An ab initio and DFT study of the fragmentation and isomerisation of MeP(O)(OMe)+
The fragmentation behaviour of the ion MeP(O)OMe+ has been investigated using quantum mechanical calculations at the B3LYP and MP2 levels to support experiments made with an Ion Trap Mass Spectrometer. Two mechanisms for the loss of CH2O are found, one involving a 1,3-H migration to phosphorus and the other a 1,2-methyl migration to give P(OMe)2+ followed by a 1,3-H migration. In each case an ion-dipole complex is formed that rapidly dissociates to yield CH2O. The relative importance of each route has been previously determined experimentally via isotopic labelling experiments, and the theoretical results are found to be consistent with these experimental results. The mechanisms suggested i…