Flipping of Coordinated Triazine Moiety in Cu(I)-L2 and Small Electronic Factor, κ el, for Direct Outer-Sphere Cross Reactions: Syntheses, Crystal Structures and Redox Behavior of Copper(II)/(I)-L2 Complexes (L = 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine)
Flipping of Coordinated Triazine Moiety in Cu(I)-L2 and Small Electronic Factor, κ el, for Direct Outer-Sphere Cross Reactions: Syntheses, Crystal Structures and Redox Behavior of Copper(II)/(I)-L2 Complexes (L = 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine)
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Cu(I)-L2 中配位三嗪部分的翻转和小电子因子 κ el 用于直接外球交叉反应：铜(II)/(I)-L2 配合物的合成、晶体结构和氧化还原行为 (L = 3-(2-吡啶基)-5,6-二苯基-1,2,4-三嗪)
DOI：
10.1039/c5dt01808k
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
and Hideo D. Takagi
中科院分区：
文献类型：
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作者：
Atsutoshi Yamada;Takuya Mabe;Ryohei Yamane;Kyoko Noda;Yuko Wasada;Masahiko Inamo;Koji Ishihara;Takayoshi Suzuki;and Hideo D. Takagi
合成了六配位[Cu（pdt）2（H2O）2]2+和四配位[Cu（pdt）2]+配合物，研究了它们在乙腈（pdt = 3-（2-吡啶基）-5，6-二苯基-1，2，4-三嗪）中的交叉氧化还原反应。单晶结构分析表明，[Cu（pdt）2（H2O）2]（BF 4）2具有两个轴向水分子和两个对称配位的赤道型pdt配体的拟D2 h对称性，而[Cu（pdt）2] BF 4的配位结构为挤压四面体（二面角= 54.87°），通过两个PDT配体进行不对称配位：一个PDT配体通过吡啶-N和三嗪-N2与Cu（I）配位，而另一个PDT配体通过吡啶-N和三嗪-N4与Cu（I）配位，一个pdt配体上的苯环与另一个pdt配体上的三嗪环之间的堆积作用导致了Cu-N键长的不相等和压扁结构。[Cu（pdt）2（H2O）2]2+和[Cu（pdt）2]+在乙腈中的循环伏安图完全相同，且是准可逆的。在乙腈溶液中，[Cu（pdt）2（H2O）2]2+被十甲基二茂铁还原，[Cu（pdt）2]+被[Co（2，2 ′-bipyridine）3]3+氧化，发现这两个交叉反应都是缓慢的门控过程（结构变化发生在电子转移之前），并伴有缓慢的直接电子转移过程.结果表明，pdt配体的三嗪环围绕三嗪环和吡啶环之间的C-C键旋转，动力学参数k = 51 ± 5 s−1（297.8 K），ΔH = 6.2 ± 1.1 kJ mol−1，ΔS = −192 ± 4 J mol−1 K−1。电子自交换过程用谱线展宽法直接测量：kex =（9.9 ± 0.5）× 104 kg mol−1 s−1（297.8 K），ΔH = 44 ± 7 kJ mol−1和ΔS = 0.2 ± 2.6 J mol−1 K−1。通过比较该速率常数与用Marcus交叉关系估算的交叉反应自交换速率常数，估算了[Cu（pdt）2]+/2+与非铜金属（Fe 2+和Co 3+）配合物之间直接电子转移过程的非绝热性（电子）因子κel为ca. 10−7，表明铜和非铜金属的d轨道之间的电子耦合非常小。
Six-coordinate [Cu(pdt)2(H2O)2]2+ and four-coordinate [Cu(pdt)2]+ complexes were synthesized and the cross redox reactions were studied in acetonitrile (pdt = 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine). Single crystal analyses revealed that [Cu(pdt)2(H2O)2](BF4)2 was of pseudo-D2h symmetry with two axial water molecules and two symmetrically coordinated equatorial pdt ligands, while the coordination structure of [Cu(pdt)2]BF4 was a squashed tetrahedron (dihedral angle = 54.87°) with an asymmetric coordination by two pdt ligands: one pdt ligand was coordinated to Cu(I) through pyridine-N and triazine-N2 while another pdt ligand was coordinated through pyridine-N and triazine-N4, and a stacking interaction between the phenyl ring on one pdt ligand and the triazine ring on another pdt ligand caused the squashed structure and non-equivalent Cu–N bond lengths. The cyclic voltammograms for [Cu(pdt)2(H2O)2]2+ and [Cu(pdt)2]+ in acetonitrile were identical to each other and quasi-reversible. The reduction of [Cu(pdt)2(H2O)2]2+ by decamethylferrocene and the oxidation of [Cu(pdt)2]+ by [Co(2,2′-bipyridine)3]3+ in acetonitrile revealed that both cross reactions were sluggish through a gated process (the structural change took place prior to the electron transfer) accompanied by slow direct electron transfer processes. It was found that the triazine ring of the coordinated pdt ligand rotates around the C–C bond between the triazine and pyridine rings with the kinetic parameters k = 51 ± 5 s−1 (297.8 K), ΔH‡ = 6.2 ± 1.1 kJ mol−1 and ΔS‡ = −192 ± 4 J mol−1 K−1. The electron self-exchange process was directly measured using the line-broadening method: kex = (9.9 ± 0.5) × 104 kg mol−1 s−1 (297.8 K) with ΔH‡ = 44 ± 7 kJ mol−1 and ΔS‡ = 0.2 ± 2.6 J mol−1 K−1. By comparing this rate constant with the self-exchange rate constants estimated from the cross reactions using the Marcus cross relation, the non-adiabaticity (electronic) factors, κel, for the direct electron transfer processes between [Cu(pdt)2]+/2+ and non-copper metal (Fe2+ and Co3+) complexes were estimated as ca. 10−7, indicating that the electronic coupling between the d orbitals of copper and of non-copper metals is very small.