Corrin nitrogens and remote dimethylbenzimidazole nitrogen interactions in Cob(II)alamin studied with HYSCORE at X- and Q-band

A continuous wave and pulse electron paramagnetic resonance study of the base-on form of cob(II)alamin diluted in hydroxocob(III)alamin powder is presented. HYSCORE spectroscopy at X- and Q-band was used to study the weakly coupled corrin nitrogens and the remote nitrogen of the axial dimethylbenzimidazole ligand. Simulations of the spectra measured at different field positions enabled the following parameters to be determined; for the corrin nitrogens the hyperfine principal values are A1=−4.5 MHz, A2=−3.4 MHz and A3=(−2.2 to −2.5) MHz with Euler angles [α,β,γ]=[n90,25,0]° and the nuclear quadrupole parameters are e2qQ/h=1.75 MHz and η=0.95 with Euler angles [α,β,γ]=[90+n90,90,12.5]°, where n=0,1,2,3. The remote nitrogen of the dimethylbenzimidazole ligand has A1=1.75 MHz, A2=1.75 MHz and A3=2.10 MHz with Euler angles [α,β,γ]=[−45,−10,0]° and e2qQ/h=−3.3 MHz and η=0.1 with Euler angles [α,β,γ]=[45,90,67]°.