The first definitive experimental characterization of the unusual HBBH molecule is reported. It has been generated by several different methods and trapped in neon and argon matrices for a detailed electron spin resonance (ESR) investigation. A complete resolution of the IlB and 'H nuclear hyperfine structure into isotropic and dipolar components was possible. Ab initio CI calculations, conducted as part of this experimental study, yielded Aiso and Adip parameters in good agreement with the observed values. These ESR results offer the first confirmation that HBBH has a 3Xgelectronic ground state as predicted by earlier theoretical calculations. The HBBH molecule resembles acetylene with one electron removed from each of the x-type molecular orbitals. Molecules that contain boron-boron double bonds are extremely rare.

Four isotopes of the methanol cation radical (CH3OH+) have been generated by three independent methods and isolated in neon matrices at 4 K for a detailed electron spin resonance (ESR) investigation. The ion generation methods employed were X irradiation, photoionization, and electron ionization. The nuclear hyperfine (A tensors) measurements were compared with those obtained from ab initio extended basis set multireference configuration interaction (CI) wave functions. The relationships between geometry and electronic structures were fully explored. The trend in the large isotropic methyl hydrogen A values for the isoelectronic series CH3F+, CH3OH+, and CH3NH2+ was found to follow the trend in dissociation energies for these radical cations. The neon magnetic parameters for CH3OH+ are gx=2.0036(4) and gz=2.010(1); Aiso (methyl hydrogens)=229(1) MHz, ‖Ax‖=54(2) and ‖Az‖=80(3) MHz for the hydroxy hydrogen; ‖Ax‖=40(2) and ‖Az‖=29(4) MHz for 13C. The observed magnetic parameters for CH2DOH+ indicate an unusually large deuterium effect Aiso (CH2)=329 MHz with ‖Aiso‖=4.1(3) MHz for the methyl deuterium. These results show that averaging of the methyl hydrogen environments is occurring on the ESR time scale.

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ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.