Flavoquinone-metal complexes. II. Paramagnetic interactions
Flavoquinone-metal complexes. II. Paramagnetic interactions
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黄酮醌金属络合物。
DOI：
10.1021/ic50151a027
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发表时间：
1975
影响因子：
4.6
通讯作者：
J. Lhoste
中科院分区：
文献类型：
--
作者：
J. Lauterwein;P. Hemmerich;J. Lhoste
使用3d系列的二价顺磁离子：Mn 11、Fe 11、Co 11、Ni 11、Cu 11对黄醌复合物进行质子磁共振研究。磁化率和电子自旋共振测量提供了有关这些复合物的磁状态的补充信息。的顺磁性的配体共振的线宽的贡献进行了分析，作为金属的黄素浓度和温度的函数，以估计在弛豫过程中所涉及的相关时间的值。各向同性的位移进行了分析，在接触和pseudocontact相互作用，使用松弛数据和结构信息，以及由电子自旋共振测量的g-张量各向异性。这两种相互作用的相对重要性与从通常的因式分解过程中得出的结果相比毫不逊色。伪接触位移出现明显的Co 11和Cu 11配合物和可忽略的Ni 11和Fe 11配合物。接触位移表现出的各种配体共振非常相似的稳定的bidendate螯合物，这可能是由于a-电子自旋负极化的配体轨道之间的分布模式。自旋转移机制似乎是由于在配位点的间接自旋极化结合负极化自旋在配体成键轨道的离域。这种接触相互作用的机制表明，在非质子溶剂中的黄酮-金属络合物的稳定性来自型键合，很少，如果有的话，键合。
Proton magnetic resonance studies were carried out on flavoquinone complexes using divalent paramagnetic ions of the 3d series: Mn11, Fe11, Co11, Ni11, Cu11. Magnetic susceptibility and electron spin resonance measurements provided complementary information about the magnetic state of these complexes. The paramagnetic contribution to the line width of the ligand resonances was analyzed as a function of metal to flavine concentration and of temperature in order to estimate the value of the correlation times involved in the relaxation processes. The isotropic shifts were analyzed in terms of contact and pseudocontact interactions using the relaxation data and structural information derived earlier, together with the g-tensor anisotropy measured by electron spin resonance. The relative importance of the two kinds of interactions compares favorably with that derived from the usual factorization procedure. Pseudocontact shifts appear noticeable in Co11 and Cu11 complexes and negligible in Ni11 and Fe11 complexes. The contact shifts exhibit a distribution pattern for the various ligand resonances very similar among the stable bidendate chelates, which could be attributed to a-electron spin negatively polarized in the ligand orbitals. The spin-transfer mechanism appears to result from indirect- spin polarization at the coordination site combined with a delocalization of negatively polarized spin in the ligand-bonding orbitals. This mechanism for contact interaction indicates that the stability of the flavoquinone-metal complexes inaprotic solvents arises from-type bonding, with little, if any, bonding.