ELECTRON SPIN ECHO ENVELOPE MODULATION OF DEOXYCO MYOGLOBIN & PORPHYRIN MODELS

氧钴卟啉的ESEEM和EXAFS研究 [1-甲基咪唑（1-MeIm）进行，以检查 氧亲合势与电子-核耦合的关联 参数和金属-配体键长。 ESEEM表明， 电子核超精细和核四极矩的量级 与1-MeIm的直接配位14 N的偶联降低了 溶剂组成在0 - 50%（v/v）二氯甲烷中变化， 甲苯 对于oxyCo[（o-R）1）TPP][MeIm]（其中R = -H、-NHCOC（CH 3）3， - NHCOCH 3或-NHCONHC 6 H5是四个内消旋基团之一上的邻位取代基， TPP的苯基），与轴向氮的偶联随着 R的吸电子强度增加，即， 酸性的酰胺质子的R，可能与结合 分子氧 EXAFS测量和使用从头算EXAFS的分析 代码和全球映射，发现钴轴氮（Nax） 当溶剂为0.05时，oxyCoTPP-1-MeIm的键缩短0.18 q 0.06。 从100%甲苯（Co-Nax = 2.12）变更为50%甲苯/50% 二氯甲烷（Co-Nax = 1.94）。增加的极性 溶剂和附近的结合双氧增加氧 由于金属离子的离子性增加， 钴-二氧键，表现为还原， 电子核耦合到轴向氮和缩短的 钴-轴向氮键 这些ESEEM和EXAFS表征 金属-配体相互作用的关系表明， 电子-核耦合和金属-配体键长

ESEEM and EXAFS of oxyCo [tetraphenylporphyrin (TPP)] [1-methylimidazole (1-MeIm) were carried out in order to examine the correlation of oxygen affinity withelectron-nuclear coupling parameters and metal-ligand bond lengths. ESEEM demonstrates that the magnitude of the electron-nuclear hyperfine and nuclear quadrupole couplings to the directly-coordinated 14N of 1-MeIm decrease s the solvent composition is varied from 0 to 50% (v/v) dichloromethane in toluene. For oxyCo[(o-R)1)TPP][MeIm] (where R = -H, -NHCOC(CH3)3, -NHCOCH3, or -NHCONHC6H5 an ortho substituent on one of the four meso phenyls of TPP), couplings to the axial nitrogen decrease with increased electron-withdrawing strength of R, i.e, with increased acidity of the amide proton of R that may interact with the bound dioxygen. EXAFS measurements, and analysis using ab initio EXAFS codes and global mapping, find that the cobalt-axial nitrogen (Nax) bond of oxyCoTPP-1-MeIm shortens by 0.18 q 0.06 when the solvent is changed from 100% toluene (Co-Nax = 2.12 ) to 50% toluene/50% dichloromethane (Co-Nax = 1.94 ). Increasing the polarity of the solvent and of the vicinity of the bound dioxygen increases oxygen affinity of the metal due to an increase in the ionicity of the cobalt-dioxygen bond that is manifested in reduction in electron-nuclear couplings to the axial nitrogen and shortening of the cobalt-axial nitrogen bond. These ESEEM and EXAFS characterizations of metal-ligand interactions demonstrate the correlation of electron-nuclear coupling and metal-ligand bond lengths