ELECTRON SPIN ECHO ENVELOPE MODULATION OF DEOXYCO MYOGLOBIN & PORPHYRIN MODELS

氧钴[四苯基卟啉(TPP)]的ESEEM和EXAFS研究 [1-甲基咪唑(1-MeIm)]检查 氧亲和力与电子-核耦合的关系 参数和金属-配体键长。ESEEM演示了 电子-核超精细和核四极矩的大小 1-MeIM直接配位的14N偶联降低了S的 溶剂组成从0到50%(v/v)的二氯甲烷在 甲苯。对于氧钴[(o-R)1)TPP][MeIm](其中R=-H，-NHCOC(CH3)3， -NHCOCH3或-NHCONHC6H5是四个介孔分子中的一个上的邻位取代基 TPP的苯基)，与轴向氮的偶联度随着 增加了R的吸电子强度，即随着增加 可能与结合态相互作用的R的酰胺质子的酸性 氧气。EXAFS测量，并使用从头算EXAFS进行分析 编码和全球映射，发现钴轴向氮(Nax) OxCoTPP-1-MeIm在溶剂为 从100%甲苯(Co-Nax=2.12)变为50%甲苯/50% 二氯甲烷(Co-Nax=1.94)。增加了分子的极性 溶剂和结合氧附近的氧增加了氧 由于金属的电离性增加而引起的金属亲和力 钴-二氧键，表现为还原 电子-核耦合到轴向氮和缩短 钴-轴向氮键。这些ESEEM和EXAFS特征 证明了金属-配体相互作用的相关性 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