The metal carbide radicals AlC and AlC2 have been generated by the laser vaporization of aluminum carbide and trapped in neon and argon matrices at 4 K for electron spin resonance (ESR) characterization. These results provide the first experimental evidence showing that AlC has a 4Σ ground electronic state and that AlC2 is X 2A1. Ab initio theoretical calculations were conducted for the geometries and various nuclear hyperfine parameters in both radicals which yielded A values in reasonable agreement with the observed. In AlC, the three unpaired electrons reside primarily on carbon with the following neon matrix magnetic parameters (MHz): g∥=2.000(1); g⊥=2.0010(5); ‖A⊥(Al)‖=33.2(5); ‖A∥(Al)‖=3(3); A⊥(13C)=52.1(5); A∥(13C)=52(2); and D(zero field splitting)=374(1). For AlC2, the spin density resides predominantly in an aluminum 3pz/3s hybrid directed away from C2. The neon magnetic parameters (MHz) are: g∥=2.0005(5); g⊥=1.9965(3); A⊥(Al)=941.5(5); A∥(Al)=1067(1); ‖A∥(13C)‖=59(1); and ‖A⊥(13C)‖=52(1).

The first spectroscopic study of the diatomic radical BC is reported which confirms previous theoretical predictions of a 4∑− electronic ground state. The nuclear hyperfine interactions (A tensors) obtained for 11B, 10B, and 13C from the electron spin resonance (ESR) measurements are compared with extensive ab initio CI calculations. The BC molecule is one of the first examples of a small high spin radical for such an in-depth experimental–theoretical comparison. The electronic structure of BC obtained from an analysis of the nuclear hyperfine interaction (hfi) is compared to that obtained from a Mulliken-type population analysis conducted on a CI wave function which yields Aiso and Adip results in good agreement with the observed values. The BC radical was generated by the laser vaporization of a boron–carbon mixture and trapped in neon, argon, and krypton matrices at 4 K for a complete ESR characterization. The magnetic parameters (MHz) obtained for 11B13C in solid neon are: g∥ =2.0015(3); g⊥ =2.0020(3); D(zfs)=1701(2); 11B: ‖A∥‖ =100(1); ‖A⊥‖ =79(1); 13C: ‖A∥‖ =5(2) and ‖A⊥‖ =15(1). Based on comparison with the theoretical results, the most likely choice of signs is that all A values are positive.

The 11 electron CBC radical has been generated by the pulsed laser vaporization of elemental carbon–boron mixtures and trapped in neon, argon and krypton matrices for detailed electron spin resonance (ESR) studies. Extensive comparisons of the experimental nuclear hyperfine A tenors for carbon and boron were made with a variety of ab initio computational results that involved different levels of theory and basis sets. These new ESR results agree with recent vibrational studies of CBC that show it to have a nonlinear symmetric geometry with a 2A1 electronic ground state. These ESR results provide a description of the singly occupied molecular orbital. The spin density resides primarily on boron in 2s and 2pz orbitals, however a complete resolution of the 13C hyperfine structure does show that approximately 20% resides on the carbon atoms.

No abstract

The Pd12CH3, Pd13CH3, and 105Pd12CH3 radicals have been generated by reactive laser vaporization and isolated in neon matrices at 4 K for electron spin resonance (ESR) investigation. Apparently no previous monomethyl metal radical has been characterized by ESR despite the importance of such species as reactive intermediates. These results allow an experimental description of the electronic structure in the valence region to be obtained. A direct electronic structure comparison between PdH and PdCH3 is also presented. A significant amount of s/d hybridization on Pd is observed which agrees with earlier calculations on the bonding in Pd(CH3)2. The magnetic parameters (MHz) for PdCH3 in neon matrices are: g⊥=2.273(1); for 105Pd, A⊥=−946(2), A∥=−987(20); for H, ‖A‖=13(1); and for 13C, ‖A‖=10.2(4).