The Rotational Orientation Angles of Axial Ligands in Low-Spin Fe(III) Heme Complexes As Determined from Frozen-Solution Samples

从冷冻溶液样品中测定低自旋 Fe(III) 血红素复合物中轴向配体的旋转取向角

• 批准号: 63571026
• 负责人: SATO Mitsuo
• 金额: $ 1.34万
• 依托单位: Teikyo University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1988
• 资助国家: 日本
• 起止时间: 1988 至 1989
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-63571026/
• 关键词: Low-spin Fe(III) heme complex; Rotational orientation of rhombic field; Rotational orientation of axial ligand; Iron-57 hf splitting; Relative orientations of g and hf tensors; Pー450モデル錯体; P-450モデル錯体; 軸配位子の回転配向; Low-spin Fe(III) heme complex; Rotational orientation of rhombic field; Rotational orientation of axial ligand; Iron-57 hf splitting; Relative orientations of g and hf tensors; Pー450モデル錯体; P-450モデル錯体; 軸配位子の回転配向

Hyperfine (hf) splittings due to the ^<57>Fe nucleus (I=1/2) have been observed in frozen-solution ESR measurements on a series of low-spin Fe(III) heme complexes, Fe(TPP)L_1L_2, where TPP =tetraphenylporphine dianion, L_1 = RS^-, L_2 = MeOH, DMF, and RSH, and R = Et, n-Pr, i-Pr, n-Bu, s-Bu, and t-Bu. The hf splitting (A_<(i)>) values of the g_i absorption peaks (i = X, Y, Z) are analyzed within the framework of a low-symmetry (C_2) crystal field model to determine the rotational orientation angle (phi) of the axes of rhombic component field and that (phi_l) of the axial thiolato ligand plane (Fe-S-C plane) with the approximation of phi_l = phi. It is found that phi_l varies from 6 to 37ﾟ depending upon the thiolato ligand (RS^-), the 6th axial ligand (L_2), and the solvent system (CH_2Cl_2 - MeOH, DMF-MeOH, or CH_2Cl_2-RSH), but with no clear correlation between phi_l and RS^-. However, phi_l correlates well with the energy splittings in the three t_2 orbitals: phi_l increases as the tetragonal splitting decreases or as the rhombic splitting and crystal field rhombicly increase. These results suggest that two major factors, namely, steric and electronic effects, influence the axial ligand orientation. The observed angles phi_l = 6-37ﾟ are the results of the two effects.

由于 ^<57> fe核（i = 1/2）引起的超精细（HF）分裂已在一系列低旋转Fe（III）血红素复合物，Fe（TPP）L_1L_2上观察到在冷冻测量ESR测量中N-pr，I-pr，N-BU，S-BU和T-BU。 The hf splitting (A_<(i)>) values ​​of the g_i abstraction peaks (i = X, Y, Z) are analyzed within the framework of a low-symmetry (C_2) crystal field model to determine the rotational orientation angle (phi) of the axes of rhombic component field and that (phi_l) of the axial thiolato ligand plane (Fe-S-C plane) with the approximation of phi_l = phi。发现Phi_l的品种从6到37°ﾟ取决于硫醇配体（rs^ - ），第6轴向配体（L_2）和溶剂系统（CH_2CL_2-MEOH，DMF-MEOH，或CH_2CL_2-RSH），但在Phi__l和Rs^ - rs^------^--------但没有明确的相关性。但是，PHI_L与三个T_2轨道中的能量分割良好相关：PHI_L随着四方分裂的降低或菱形分裂和晶体场的成长而增加。这些结果表明，两个主要因素，即空间和电子效应，影响轴向配体方向。观察到的角度phi_l = 6-37 ﾟ是两种效应的结果。