High-frequency and field EPR investigation of (8,12-diethyl-2,3,7,13,17,18-hexamethylcorrolato)manganese(III)
High-frequency and field EPR investigation of (8,12-diethyl-2,3,7,13,17,18-hexamethylcorrolato)manganese(III)
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DOI：
10.1021/ja010947g
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发表时间：
2001-08-15
影响因子：
15
通讯作者：
Licoccia, S
中科院分区：
文献类型：
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作者：
Krzystek, J;Telser, J;Licoccia, S
固体 (8,12-二乙基-2,3,7, 13,17,18-六甲基相关)锰(III), 1 的高场和频率电子顺磁共振 (HFEPR) 表明，在固态下，它可以很好地描述为三阴离子配体 [(MnC3-)-C-III] 的 S = 2（高自旋）Mn(III) 络合物，就像 Mn(III) 一样卟啉被描述为[(MnP2-)-P-III](+)。 1、Mn(III) 卟啉和不同的 Mn(III) 咔咯 [(tpfc)Mn(OPPh3)] 的结构数据和自旋哈密顿参数之间的比较，之前由 HFEPR 研究过（Bendix, J.；Gray, H. B.；Golubkov. G.；Gross, Z. J. Chem. Soc., Chem. Commun. 2000， 1957-1958）表明，尽管咔咯大环的分子不对称性，Mn（HI）离子的电子结构大致是轴向的。然而，在corroles中，无论轴向配体如何，S = 1（中间自旋）态的能量都比卟啉低得多。在吡啶溶液中于 4.2 K 下测量的 1 的 HFEPR 显示维持了 S = 2 [(MnC3-)-C-III] 体系。电子参数略有变化，这可能是轴向吡啶配体配位的结果。本结果是通过 HFEPR 检测溶液中 Mn(III) 络合物的第一个例子。然而，在环境温度下，在吡啶溶液中经过数小时后，S = 2 Mn(III) 光谱逐渐消失，留下 g = 2 和 Mn-55 的信号。超精细分裂。对该信号的分析也可通过传统 EPR 观察到。导致其分配给可能由原始络合物分解产生的锰物质。低温S = 2 [(MnC3-)-C-III]状态与室温下相反。它被描述为 S = 1 系统，源自 S = (3)/(2) Mn(II) 离子和以咔咯为中心的自由基阳离子之间的反铁磁耦合：[(MnC.2-)-C-II] (Licoccia, S.; Morgante. E.; Paolesse. R., Polizio, F.; Senge, M. O., Tondello. E.; Boschi, T, Inorg.化学 1997, 36, 1564-1570)。在其他金属四吡咯中也观察到了这种温度依赖性价态异构化。
High-field and frequency electron paramagnetic resonance (HFEPR) of solid (8,12-diethyl-2,3,7, 13,17,18-hexamethylcorrolato)manganese(III), 1, shows that in the solid state it is well described as an S = 2 (high-spin) Mn(III) complex of a trianionic ligand, [(MnC3-)-C-III], just as Mn(III) porphyrins are described as [(MnP2-)-P-III](+). Comparison among the structural data and spin Hamiltonian parameters reported for 1, Mn(III) porphyrins, and a different Mn(III) corrole, [(tpfc)Mn(OPPh3)], previously studied by HFEPR (Bendix, J.; Gray, H. B.; Golubkov. G.; Gross, Z. J. Chem. Soc., Chem. Commun. 2000, 1957-1958), shows that despite the molecular asymmetry of the corrole macrocycle, the electronic structure of the Mn(HI) ion is roughly axial. However, in corroles, the S = 1 (intermediate-spin) state is much lower in energy than in porphyrins, regardless of axial ligand. HFEPR of 1 measured at 4.2 K in pyridine solution shows that the S = 2 [(MnC3-)-C-III] system is maintained. with slight changes in electronic parameters that are likely the consequence of axial pyridine ligand coordination. The present result is the first example of the detection by HFEPR of a Mn(III) complex in solution. Over a period of hours in pyridine solution at ambient temperature, however, the S = 2 Mn(III) spectrum gradually disappears leaving a signal with g = 2 and Mn-55. hyperfine splitting. Analysis of this signal, also observable by conventional EPR. leads to its assignment to a manganese species that could arise from decomposition of the original complex. The low-temperature S = 2 [(MnC3-)-C-III] state is in contrast to that at room temperature. which is described as a S = 1 system deriving from antiferromagnetic coupling between an S = (3)/(2) Mn(II) ion and a corrole-centered radical cation: [(MnC.2-)-C-II] (Licoccia, S.; Morgante. E.; Paolesse. R., Polizio, F.; Senge, M. O., Tondello. E.; Boschi, T, Inorg. Chem. 1997, 36, 1564-1570). This temperature-dependent valence state isomerization has been observed for other metallotetrapyrroles.