Electron paramagnetic resonance(EPR)or electron spin resonance(ESR)has been widely employed to characterize transition metal complexes.However,because of the high degree of complexity of transition metal EPR spectra,h...Electron paramagnetic resonance(EPR)or electron spin resonance(ESR)has been widely employed to characterize transition metal complexes.However,because of the high degree of complexity of transition metal EPR spectra,how to extract the underlying electronicstructure information inevitably poses a major challenge to beginners,in particular for systems with S>1/2.In fact,the physical principles of transition metal EPR have long been well-established and since 1970s a series of dedicated voluminous monographs have been published already.Not surprisingly,they are not appropriate stating points for novices to grasp a panorama of the profound theory prior to scrutinizing in-depth references.The present review aims to fill this gap to provide a perspective of transition metal EPR and unveil some peculiar subtleties thereof on the basis of our recent work.展开更多
Iron sites in both nitrogenase enzymes and chemical catalysts for N_(2) fixation are typically at constrained distances and angles.Herein,we report a one-electron reduction reaction realized by constrained diiron dini...Iron sites in both nitrogenase enzymes and chemical catalysts for N_(2) fixation are typically at constrained distances and angles.Herein,we report a one-electron reduction reaction realized by constrained diiron dinitrogen cores.Using the semicircular bis(β-diketiminate)ligand,a series of diiron dinitrogen complexes were synthesized,in which the N_(2) groups were allowed to bind with Fe-Ct_(N2)-Fe angles ranging from 154°to 158°(Ct_(N2)=centroid of N_(2)).One-electron reduction of complex 2a[LFe(μ-N_(2))Fe(Et_(2)O)]gave dimer product 3a[LFe(μ-N_(2))FeK]_(2)(μ-N_(2))or monomer 3b[LFe(μ-N_(2))Fe(DMAP)K].Based on superconducting quantum interference device measurements and density functional theory calculations,2a,3a,and 3b exhibited ground spin states of S=3,S=5,and S=5/2,respectively.In addition,complex 3 underwent N_(2)derivatization via a silylation pathway followed by an acidic cleavage to yield N_(2)H_(4)as the product.展开更多
基金the financial support from Chinese Academy of Sciences,National Science Foundation of China(92161204)Max-Planck Society。
文摘Electron paramagnetic resonance(EPR)or electron spin resonance(ESR)has been widely employed to characterize transition metal complexes.However,because of the high degree of complexity of transition metal EPR spectra,how to extract the underlying electronicstructure information inevitably poses a major challenge to beginners,in particular for systems with S>1/2.In fact,the physical principles of transition metal EPR have long been well-established and since 1970s a series of dedicated voluminous monographs have been published already.Not surprisingly,they are not appropriate stating points for novices to grasp a panorama of the profound theory prior to scrutinizing in-depth references.The present review aims to fill this gap to provide a perspective of transition metal EPR and unveil some peculiar subtleties thereof on the basis of our recent work.
基金supported by National Natural Science Foundation of China(grant nos.21988101,22201013,92161204)China Postdoctoral Science Foundation(grant no.2020M670016)Beijing Natural Science Foundation(grant no.2222008).
文摘Iron sites in both nitrogenase enzymes and chemical catalysts for N_(2) fixation are typically at constrained distances and angles.Herein,we report a one-electron reduction reaction realized by constrained diiron dinitrogen cores.Using the semicircular bis(β-diketiminate)ligand,a series of diiron dinitrogen complexes were synthesized,in which the N_(2) groups were allowed to bind with Fe-Ct_(N2)-Fe angles ranging from 154°to 158°(Ct_(N2)=centroid of N_(2)).One-electron reduction of complex 2a[LFe(μ-N_(2))Fe(Et_(2)O)]gave dimer product 3a[LFe(μ-N_(2))FeK]_(2)(μ-N_(2))or monomer 3b[LFe(μ-N_(2))Fe(DMAP)K].Based on superconducting quantum interference device measurements and density functional theory calculations,2a,3a,and 3b exhibited ground spin states of S=3,S=5,and S=5/2,respectively.In addition,complex 3 underwent N_(2)derivatization via a silylation pathway followed by an acidic cleavage to yield N_(2)H_(4)as the product.
