Electron spin resonance (ESR) studies are reported for the first time on the various isotopomers of the CH3Cd radical isolated in neon and argon matrices. The radicals were generated in neon matrices by the reaction of laser-ablated cadmium metal and various methyl precursors, and in argon matrices by x-irradiation. The neon matrix values measured were g⊥=1.9491(1), A⊥(H)=17.0(1) MHz, A⊥(D)=2.6(1) MHz, A⊥(13C)=163(3) MHz, and A⊥(111Cd)=−3083(3) MHz, and estimates were derived for A∥(13C)=230(50) MHz and A∥(111Cd)=−3486(5) MHz. The argon matrix values measured were g⊥=1.952(1), A⊥(H)=16(1) MHz and A⊥(111Cd)=−3301(3) MHz, and an estimate was derived for A∥(111Cd)=−3704(5) MHz. The ESR experimental Adip(111Cd) values for the neon and the argon matrices agree with the reported gas-phase value [J. Chem. Phys. 101, 6396 (1994)]. The matrix ESR Aiso(111Cd) values show small shifts compared with the gas-phase results (5% greater for the neon matrix and 12% greater for the argon matrix). At 4.3 K in the neon matrices, additional ESR lines assigned to tunneling phenomena were observed. The radical geometry obtained from ab initio calculations was consistent with that reported from the various experimental results. Multireference single and double excitation configuration interaction (MRSDCI) calculations of the hyperfine interactions gave values that were consistently below the experimental values of Aiso and Adip for 111Cd, H, and 13C. MRSDCI calculations for the CdH radical showed an analogous trend.

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The 12CH3Zn, 12CH3 67Zn, 13CH3Zn, 13CH3 67Zn, 13CD3 67Zn, and 13CD3Zn radicals have been isolated in an inert neon matrix at 4.3 K. Their electronic structure has been probed for the first time using matrix-isolation electron spin resonance spectroscopy (MI-ESR). These radicals were generated by the reaction of laser-ablated zinc metal with the appropriate methyl precursor. The magnetic parameters (MHz) were determined to be g ⊥ = 1.9835(4), A ⊥(H) = 14(1), A ⊥(D) = 2.2(4), A ⊥(13C) = 166(3), and A ⊥(67Zn) = 547(1). Estimates were derived for A ∥(13C) = 211(50) and A ∥(67Zn) = 608(5). The 67ZnH radical was also generated by the reaction of laser-ablated zinc metal and hydrogen gas and studied for the first time by MI-ESR after isolation in solid neon matrixes at 4 K. The values of the 67ZnH magnetic parameters (MHz) were determined to be g ⊥ = 1.9841(3), g ∥ = 1.9990(5), A ⊥(H) = 505(1), A ∥(H) = 503(1), A ⊥(67Zn) = 615(1), and A ∥(67Zn) = 660(1). Earlier argon MI-ESR studies produced ZnH by conventional high-temperature methods and determined only the hydrogen hyperfine interaction and the molecular g tensor. Hartree−Fock single- and double-excitation configuration interaction (HFSDCI) and multireference single- and double-excitation configuration interaction (MRSDCI) ab initio calculations of the magnetic hyperfine interactions in the CH3Zn and ZnH radicals were performed. The A iso(67Zn) and the A dip(67Zn) values calculated for both radicals were within 10% of the experimental observations. However, the calculated A iso(13C) values for the CH3Zn radical were low by about 50%, and the calculated A iso(H) value for ZnH was low by 60%. Density functional theory (DFT) yielded A iso values for H and 13C in much closer agreement with experiment. A comparison is presented between the ESR results for the CH3Zn and ZnH radicals and their cadmium analogues, which have been investigated previously by MI-ESR.

radicals have been isolated in an inert neon matrix at 4.3 K and their electronic structure probed, for the first time, using matrix isolation electron spin resonance (MI-ESR) spectroscopy. These radicals were formed from the reaction of laserablated magnesium metal and an appropriately labeled derivative of acetone or methyl iodide. The spin Hamiltonian parameters, g ⊥ ) 1.9999(4), A ⊥ ( 25 Mg) ) -184(1) MHz, A ⊥ ( 13 C) ) 128(2) MHz and A ⊥ (H) ) 7(1) MHz were determined from an exact diagonalization analysis of the experimental spectra and estimates were derived for A | ( 25 Mg) ) -197(10) MHz and A | ( 13 C) ) 180( 20) MHz assuming g | ) 2.0023. A model for the bonding in the CH 3 Mg radical is derived using this hyperfine data. Comparisons are made between the CH 3 Mg radical and other related magnesium and monomethylmetal radicals, MgH, MgOH, CH 3 Cd, CH 3 Zn, and CH 3 Ba. Theoretical nuclear hyperfine coupling constants for the CH 3 Mg radical were evaluated using Hartree-Fock single and double excitation configuration interaction (HFSDCI), multireference single and double excitation configuration interaction (MRSDCI) and density functional theory (DFT) ab initio calculations. While these theoretical methods yielded values for A dip ( 25 Mg) and A dip ( 13 C) in agreement with the experimental values, the calculated A iso ( 25 Mg) value was low by 4% (HFSDCI) and 15% (MRSDCI). Whereas the calculated A iso ( 13 C) values were low by 50% (HFSDCI) and 32% (MRSDCI). Unrestricted DFT calculations using the B3PW91 and B3LYP functionals yielded values of A iso ( 25 Mg) low by approximately 15% for both functionals and values of A iso ( 13 C) in agreement with experiment for UB3LYP and low by 10% for UB3PW91. The discrepancy between the calculated and experimental values of A iso ( 13 C) for the CI results is attributed to the limited reference space resulting in an overestimation of the ionic character in the bonding of the CH 3 Mg radical.

The Hg12CH3, Hg13CH3, Hg12CD3, 199Hg12CH3, 201Hg12CH3, 201Hg13CH3, 199Hg12CD3, and 201Hg12CD3 radicals have all been formed in a microwave discharge and isolated in an inert neon matrix. Their electronic structure was established for the first time using electron spin resonance (ESR) spectroscopy. The following magnetic parameters were determined from the experimental spectra, g ⊥ = 1.84525(20), A ⊥(199Hg) = 4337(3) MHz, A ⊥(201Hg) = 1604(1) MHz, A ⊥(13C) = 146(2) MHz, A ⊥(H) = 31(1) MHz, and A ⊥(D) = 5(1) MHz. Estimates were made for the following magnetic parameters, g ∥ = 1.990(5), A ∥(199Hg) = 5658(10) MHz, A ∥(201Hg) = 2094(10) MHz, and A ∥(13C) = 270(25) MHz. The free atom comparison method (FACM) was used to determine the unpaired electron spin density distribution for the radical and to develop a bonding model. The HgCH3 radical results are compared with our previous results for the ZnCH3 and CdCH3 radicals as well as other mercury-containing radicals such as HgH, HgCN, and HgF.