Germanium Hydride Radical Trapped during the Photolysis/Thermolysis of Diarylgermylene

Abstract

Herein, we report the characterization of a novel germanium hydride radical arising from the photolysis/thermolysis of the diarylgermylene GeR 2 [R = terphenyl:) 2 ] by using electron paramagnetic resonance spectroscopy complemented with theoretical calculations. The trapped germanium radical is a pseudoplanar S = 1 / 2 germanium(III) hydride, i.e.,• GeHRR′ (R = Ar iPr4 or Ar iPr6 ; R′ is a quaternary carbon), with a g tensor of [2.029, 2.003, 1.990], a 73 Ge hyperfine tensor of [−10, −90, −10] MHz, and a strong 1 H hyperfine tensor of [−23.0, −20.5, −31.5] MHz for the hydride. The germanium(III) hydride radical is a result of the insertion of a germanium(I) radical intermediate (:G ̇eR) in a C−H bond, due to the greater reactivity of the germanium(I) radical intermediate in comparison with the tin(I) counterpart that we trapped earlier.

Trapping a cross-linked lysine–tryptophan radical in the catalytic cycle of the radical SAM enzyme SuiB

“…These results confirm that the radical resides on the indole sidechain. EPR spectral simulations, in conjunction with density functional theory (DFT) calculations using the ZORA-def2-TZVP basis set (33) and the BP86 density functional (34)(35)(36), clearly identified three strongly coupled protons in this intermediate, one isotropic out-of-plane proton (H7, A = [80, 80, 80] MHz) and two anisotropic in-plane protons (H4, H6, with A = [20,50,30] MHz and [50,20,30] MHz, respectively), validating this intermediate as the hypothesized Lys-Trp• (Fig. 2B), and excluding the possibility of the C7-deprotonated radical anion.…”

“…The geometry optimization and EPR parameter calculation of the doubly methyl-capped Lys-Trp• radical shown in Fig. 2B were carried out using the ORCA 4.0.1 quantum chemistry program (62) using the ZORA-def2-TZVP basis set (33) and the BP86 density functional (34,35) as previously described (36). See SI Appendix, Table S3 for optimized atomic coordinates.…”

Applications of electron paramagnetic resonance spectroscopy to heavy main-group radicals

“…The large Ga, In, and Tl hyperfine couplings observed affirm that the radical is overwhelmingly a metal centred radical. Heavier Group 14 radical complexes 9,10,12,47,48 are of particular interest for numerous analogues within carbon chemistry. Previously, several Group 14 radicals generated within solid matrixes through 60 Co γ-irradiation or other means such as E-X halogen abstraction have been characterized by EPR spectroscopy.…”

“…11 The Power group in collaboration with the EPR group of Britt, have characterized a Ge(III) hydride radical product formed from a Ge(I) radical intermediate's C-H bond insertion. 9 The Ge(I) radical appears very reactive and has precluded trapping and characterization by EPR. The EPR spectrum of the Ge(III) hydride product exhibits large 1 H proton splittings and orientation-selective ENDOR spectroscopy 50 allowed for the complete refinement of the hydride's hyperfine tensor and orientation relative to the g-tensor.…”

Ligand Field Inversion as a Mechanism to Gate Bioorganometallic Reactivity: Investigating a Biochemical Model of Acetyl CoA Synthase Using Spectroscopy and Computation

“…Using 3777 and 107.4 MHz for the atomic isotropic and anisotropic hyperfine constants for a 13 C nucleus, respectively, an s-orbital spin density of 1.4% and a p-orbital spin density of −4.7% on the 13 C nucleus are estimated for the Ni–CO Az species. We note that the substantial degree of rhombicity of the 13 C hyperfine tensor is indicative of significant local contributions to the coupling. − The direct interaction between the nickel and carbon center diminish the utility of this simplistic point-dipole approximation to evaluate the spin density in the 13 C p-orbitals, overestimating the spin density by ignoring the radial extent of spin distribution over both the carbon p-orbitals and nickel d-orbital. , While obtaining numerical estimates for the radial spin distribution of π radicals based on main group elements interacting with protons has been developed, , the substantial asymmetry of the SOMO around the Ni center and delocalization onto the thiolate complicates derivation of such values for the Ni–CO Az system.…”