Theoretical investigation of paramagnetic group 13 diazabutadiene radicals: insights into the prediction and interpretation of EPR spectroscopy parameters.
نویسندگان
چکیده
The electronic structures and the spin density distributions of the group 13 1,4-diaza(1,3)butadiene (DAB) radicals [(R-DAB)2M]*, [(R-DAB)MX2] and {[(R-DAB)MX]2}** (M = Al, Ga, In; X = F, Cl, Br, I; R = H, Me, tBu, Ph) are studied using density functional theory at both non-relativistic and relativistic levels of theory. The calculations demonstrate that all systems share a qualitatively similar electronic structure and are primarily ligand centred pi-radicals. The calculated metal, nitrogen and hydrogen hyperfine couplings are found to be independent of the identity of the R-group and the halogen atom. They are, however, dependent on the geometry and oxidation state of the metal centre. Both observed trends contrast what has previously been deduced from the interpretation of experimental EPR and ENDOR spectra. Good agreement between the calculated and experimentally determined hyperfine coupling constants is found only for some of the studied systems. Instances where significant discrepancies between the calculated and experimental values exist can be attributed to the tendency of these systems toward complex solution behaviour, which results in differences between the solid state and solution structures of certain complexes. A careful re-evaluation of the experimental data as well as calculated reaction energies lends strong support to this hypothesis. However, further studies are needed before the identity of some of the studied radical species in solution can be unambiguously determined.
منابع مشابه
Demystifying EPR: A Rookie Guide to the Application of Electron Paramagnetic Resonance Spectroscopy on Biomolecules
Electron Paramagnetic Resonance (EPR) spectroscopy, also known as Electron Spin Resonance(ESR) especially among physicists, is a strong and versatile spectroscopic method forinvestigation of paramagnetic systems, i.e. systems like free radicals and most transition metalions, which have unpaired electrons. The sensitivity and selectivity of EPR are notable andintriguing as compared to other spec...
متن کاملELECTRON PARAMAGNETIC RESONANCE (EPR) SPECTROSCOPY AND GEOCHEMISTRY IN TIN EXPLORATION AT RENISON, TASMANIA AUSTRALIA
Rock powder of dolomite samples from the Renison mine area of Tasmania, Australia were analyzed by electron paramagnentic resonance spectroscopy (EPR), Atomic Absorption and Mass Spectrometer to identify alteration related to mineralisation. The least-altered dolomite samples, which are not effected by circulation of diagenetic and hydrothermal fluids are characterised by low Mn and Fe and ...
متن کاملInvestigation of Variations of Isotropic g- and A- Values with Orientation of Trapped O2−, N2− and Cl2− Radicals in KCl and NaCl Crystals
متن کامل
Application of EPR Spectroscopy to Examination of the Effect of Sterilization Process on Free Radicals in Different Herbs
Free radicals in the original and sterilized caraway, curry, curcuma and cardamom were studied. An X-band (9.3 GHz) electron paramagnetic resonance (EPR) spectroscopy was the experimental technique. Effect of microwave power in the range of 2.2-70 mW on amplitudes, linewidths, and lineshape parameters of the EPR spectra was tested. Free radicals concentrations in the non- and sterilized herb sa...
متن کاملThe reactivity of diazabutadienes toward low oxidation state Group 13 iodides and the synthesis of a new gallium(I) carbene analogue†
The reactions of two diazabutadiene ligands, Ar-DAB [(ArN CH)2, Ar = 2,6-Pr2C6H3] and Bu-DAB [(BuN CH)2] with either GaI or an AlI3/Al mixture have afforded the paramagnetic compounds, [{IGa (Bu-DAB)}2], [I2Ga (Bu-DAB)] and [I2Al (Ar-DAB)] which have been characterised by X-ray crystallography and EPR spectroscopy. In addition, the diamagnetic, ionic complex, [I2Al (Ar-DAB)]I, has been prepared...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
- Dalton transactions
دوره 15 شماره
صفحات -
تاریخ انتشار 2006