UV-Photoelectron Spectroscopic Studies of the Simplest 2,3-Dihydro-1H-1,3,2-diazaboroles [(CHNH)2BX, X = H, CN]

Chrostowska A, Dargelos A, Baylère P, Darrigan C, Weber L, Halama J. UV-Photoelectron Spectroscopic Studies of the Simplest 2,3-Dihydro-1H-1,3,2-diazaboroles [(CHNH)2BX, X = H, CN]. European Journal of Inorganic Chemistry. 2015;2015(31):5196-5201.Flash vacuum thermolysis of N,N′-di-tert-butyl-2,3-dihydro-1H-1,3,2-diazaborole (1) and N,N′-di-tert-butyl-2-cyano-2,3-dihydro-1H-1,3,2-diazaborole (2) has been performed with a progressive increase in temperature and direct analysis of the gaseous flow by UV-photoelectron spectroscopy. The generation of isobutene was confirmed by its PE bands, and the formation of 2,3-dihydro-1H-1,3,2-diazaborole (1′) and 2-cyano-2,3-dihydro-1H-1,3,2-diazaborole (2′) has also been evidenced. These experimental results have been corroborated by TDDFT and OVGF calculations of the ionization energies

New, simple and efficient method for the synthesis of imidazo-azines by flash vacuum thermolysis of tert-butylimines of pyrimidine-2-, pyrazine-2-, quinoline-2-, quinoxaline-2- and isoquinoline-1-carbaldehydes

Flash vacuum thermolysis reactions of N-(tert-butyl)-N-(pyrimidin-2-ylmethylidene)amine (1), N-(tert-butyl)-N-(pyrazin-2-ylmethylidene)amine (2), N-(tert-butyl)-N-(quinolin-2-ylmethylidene)amine (3), N-(tert-butyl)-N-(quinoxalin-2-ylmethylene)amine (4) and N-(tert-butyl)-N-(isoquinolin-2-ylmethylidene)amine (5) have been investigated. The formation of 3-methyl-imidazo[1,5-a]pyrimidine(6), 3-methyl-imidazo[1,5-a]pyrazine (7), 1-methyl-imidazo[1,5-a]quinoline (8), 3-methyl-imidazo[1,5-a] quinoxaline (9) and 3-methyl-imidazo[5,1-a]isoquinoline (10) as reaction products was observed. Excellent yields of imidazoazines from monocyclic imines 1 and 2 were found, whereas from bicyclic imines 3–5 slightly lower yields (50–75%) of the major products and formation of byproducts such as quinolone and isoquinoline were observed. These cyclizations were found to occur fully regioselectively onto the nitrogen atom of the adjacent ring. UV-photoelectron spectroscopy combined with FVT and quantum chemical calculations were applied for direct monitoring and characterization of the thermolysis products. The proposed mechanism of these reactions are substantiated by DFT calculations

A contribution to the direct observation of transient phosphanylidene complexes [RP=W(CO)5] (R: Me, Ph) : a revisited approach to their electronic structure by UV-photoelectron spectroscopy

An original approach involving a coupling in the gas phase between flash vacuum thermolysis (FVT) and UV-photoelectron spectroscopy (UV-PES) allowed the transient terminal electrophilic phosphanylidene complex [MeP=W(CO)5] to be characterized; this is the first direct observation of this P–Me derivative. This approach also permitted the electronic structure of [PhP=W(CO)5] to be revisited and confirmed the results obtained with the methylated analogues. In contrast, [p-NC–C6H4P=W(CO)5] proved to be too reactive to be detected under our experimental conditions. These [RP=W(CO)5] phosphanylidene complexes (R: Me, Ph) were identified by their ionization potentials, which are real “fingerprints”. These experimental data, supported by density functional calculations, give an overall electronic cartography of these transient species. For generation in the gas phase of these phosphanylidene complexes, the thermal degradation of two kinds of precursors were investigated. The joint experimental/theoretical approach allowed us to conclude that phosphanorbornadiene complexes are more suitable precursors than phosphirane complexes

Diastereoselective synthesis of tetraalkyl (R,R)-1,2-cyclohexylene-diamino-di-phosphonates bearing thiophene, furan and pyrrole moieties. Computational and experimental study on their formation

cited By 1International audienceDiastereoselective additions of dialkyl phosphites to three diimines bearing DACH moiety and thiophene, furan or pyrrole rings were studied in the aspect of their stereochemistry, structure of predominant products and mechanism. For these reasons, analysis of reaction mixture, X-ray studies of products, UV-photoelectron spectroscopy and ionization energies of the starting imines were performed experimentally while reaction profiles were calculated at the CAM-B3LYP/6-311G(d,p) level of theory. The calculated energy barriers corresponding to the gas phase are significantly low and seem to explain why the products are formed relatively easily

Direct Spectroscopic Identification of BN-Arynes and Subtle Steric Effects on Nitrogen Fixation

1,2-Azaborinines are the BN analogues of arynes through exchange of the formal CC triple bond by an isoelectronic BN bond. The BN-arynes are an underexplored class of reactive intermediates. Dibenzo[c,e][1,2]azaborinine (10,9-BN-phenanthryne) 1 was inferred as reactive intermediate by trapping reactions. Here it is shown that 1 can be generated in the gas phase by thermolysis from the pyridine adduct of 9-azido-9-borafluorene by cleavage of the dative bond with pyridine and dinitrogen extrusion. The ionization energy of 1 is 8.2 eV with ionization resulting from the π HOMO. Under cryogenic matrix isolation conditions, 9-azido-9-borafluorene photolysis results in isomerization to the dinitrogen adduct of 1 without involvement of a triplet borylnitrene intermediate. Photochemical nitrogen extrusion from 1•N2 is not possible and nitrogen fixation is irreversible under cryogenic conditions. In contrast, 2,4,7,9-tetra-tert-butyldibenzo[c,e][1,2]azaborinine can be photogenerated from the corresponding azidoborole precursor under cryogenic matrix isolation conditions, and nitrogen fixation is precluded due to steric hindrance. The BN stretching vibration at 1751 cm-1 is much weaker than in typical linear diaryl iminoboranes

How to Build Fully π-Conjugated Architectures with Thienylene and Phenylene Fragments

International audienceA series of small-sized model π-conjugated oligomers have been prepared from thienylene and phenylene or dimethylor dimethoxy-substituted phenylene units. Crystallographic data for the methoxylated compound show a quasi-planar conformation with a non-covalent S–O interaction. The resulting strong conjugation in the gas phase has also been highlighted by UV/photoelectron spectroscopy and theoretical calculations (DFT). Indeed, for these compounds there is a large energy gap ΔEπ arising from the interaction between the molecular orbitals of the isolated thienylene-phenylene species. This can be explained in terms of the energies of the two π orbitals of the dimethoxyphenylene unit, the shape of these molecular orbitals in a three-orbital interaction diagram and by the presence of the S···O interaction which re- Introduction π-Conjugated organic polymers have received much attention for several years because of the large variety of applications directly associated with the existence of an extended conjugated π-system along the polymer backbone. They have attracted much interest in the design of electronic and optoelectronic devices such as organic field-effect transistors (OFET), organic light-emitting diodes (OLED) or solar cells because of their remarkable electronic and electro- optical properties[1,2] which are easy to tune as a result of their molecular and supramolecular chemistry. Among the more notable examples, the regioregular poly(3-alkylthiophene) exhibits excellent chain planarity and extended conjugation lengths as a result of its head-to-tail regiochemistry,[ 3] leading to highly conjugated sheets with high field- [a] Hétérochimie Moléculaire et Macromoléculaire, UMR CNRS 5076, Ecole Nationale Supérieure de Chimie de Montpellier, 8, rue de l'Ecole Normale, 34296 Montpellier Cedex 05, France E-mail: [email protected] [b] Equipe de Chimie-Physique, IPREM-UMR CNRS 5254 Avenue de l'Université, B. P. 1155, 64013 Pau Cedex, France E-mail: [email protected] [c] Laboratoire des Agrégats Moléculaires et Matériaux Inorganiques, UMR CNRS 5072, Université Montpellier II, 2 Place Eugène Bataillon, 34095 Montpellier Cedex 5, France Supporting information for this article is available on the WWW under http://www.eurjoc.org or from the author. Eur. J. Org. Chem. 2007, 4019–4031 © 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 4019 duces the inter-ring angle between the two aromatic cycles. The nature of the sulfur–oxygen interaction, discussed from a theoretical point of view, is mainly electrostatic, the orbital contribution from the only correctly directed orbitals nO σ and σ*S–C being slightly stabilising. These results show extensive conjugation of the π system corroborated by a small HOMO– LUMO gap. These studies, carried out in the solid state and in the gas phase, show how important it is to combine thienylene and dialkoxyphenylene fragments to obtain oligomers with a strong electronic delocalisation. Thus, these compounds are of interest in the fields of electronic and optoelectronic devices