Emission and metal- and ligand-centered-redox characteristics of the hexarhenium(III) clusters trans- and cis-[Re6(mu 3-S)8Cl4(L)2]2-, where L is a pyridine derivative or pyrazine.
Emission and metal- and ligand-centered-redox characteristics of the hexarhenium(III) clusters trans- and cis-[Re6(mu 3-S)8Cl4(L)2]2-, where L is a pyridine derivative or pyrazine.
复制标题
六铼(III)簇反式和顺式-[Re6(mu 3-S)8Cl4(L)2]2-的发射和以金属和配体为中心的氧化还原特性，其中L是吡啶衍生物或吡嗪。
DOI：
10.1021/ic991282a
复制
发表时间：
2000
影响因子：
4.6
通讯作者：
N. Kitamura
中科院分区：
文献类型：
--
作者：
T. Yoshimura;K. Umakoshi;Y. Sasaki;S. Ishizaka;H. B. Kim;N. Kitamura
具有两个N-杂环配体的一系列面封八面体六铼（III）簇合物[Bu 4 N]2[trans-Re 6（mu 3-S）8 Cl 4（L）2]]的制备（Bu 4 N + =四正丁基铵阳离子; L =吡嗪（1a）、4，4 '-联吡啶（3a）、4-甲基吡啶（5a）、4-（二甲氨基）吡啶（6a））及其顺式类似物（分别为1b、3b、5 b和6 b）的电化学和物理化学性质。对1a进行X射线晶体结构测定以确认反式构型（C40 H80 N6 S8 Cl 4 Re 6，斜方晶系，空间群Cmca（No.64），a = 19.560（5）A，B = 19.494（4）A，c = 18.592（4）A，β = 115.76（2）度，Z = 4）。这些配合物和先前报道的[Bu 4 N]2[trans-and cis-[Re 6（mu 3-S）8 Cl 4]的可逆ReIII 6/ReIII 5 ReIV过程的氧化还原电位（4-氰基吡啶）2]（分别为2a和2b）和[Bu 4 N]2[反式-和顺式-[Re 6（mu 3-S）8 Cl 4（吡啶）2]]（分别为4a和4 b）在乙腈中的电位线性地依赖于N-杂环配体的pKa，碱性配体的电位更负。观察到1a、1b、2a和2b的配体中心氧化还原波为分裂波（Δ E1/2 = 90-140 mV），顺式异构体的分裂程度较大，吡嗪络合物的分裂程度最大。两个配体之间通过[Re 6（mu 3-S）8]2+核的电子相互作用已被提出。还观察到3a和3b的第二配体还原波，电位正移，在加入弱质子供体咪唑时与第一还原波合并。这是由4，4 '-联吡啶配体的游离吡啶基位点处的质子偶联氧化还原反应引起的。所有配合物在乙腈中室温下均能发光。而吡啶和4-甲基吡啶的配合物则表现出物理化学性质（λ em 740-750 nm，φ em 0.031-0.057，τ em 4.2-6.2微秒）类似于那些（分别为770 nm，0.039和6.3微秒）的[Re 6（μ 3-S）8 Cl 6]4-，其他配合物的发射明显较弱，λ em，φ em，和τ em值分别在763-785 nm、0.0010-0.0017和0.013-0.029微秒的范围内。对位于团簇核心和配体π * 轨道上的激发态给出了建议。
Preparations of a series of face-capped octahedral hexarhenium(III) clusters having two N-heterocyclic ligands, [Bu4N]2[trans-[Re6(mu 3-S)8Cl4(L)2]] (Bu4N+ = tetra-n-butylammonium cation; L = pyrazine (1a), 4,4'-bipyridine (3a), 4-methylpyridine (5a), 4-(dimethylamino)pyridine (6a)) and their cis analogues (1b, 3b, 5b, and 6b, respectively), and their electrochemical and photophysical properties have been reported. An X-ray crystal structure determination has been carried out for 1a to confirm the trans configuration (C40H80N6S8Cl4Re6, orthorhombic, space group Cmca (No. 64), a = 19.560(5) A, b = 19.494(4) A, c = 18.592(4) A, beta = 115.76(2) degrees, Z = 4). The redox potential of the reversible ReIII6/ReIII5ReIV process of these complexes and previously reported [Bu4N]2[trans- and cis-[Re6(mu 3-S)8Cl4(4-cyanopyridine)2]] (2a and 2b, respectively) and [Bu4N]2[trans- and cis-[Re6(mu 3-S)8Cl4(pyridine)2]] (4a and 4b, respectively) in acetonitrile depends linearly on the pKa of the N-heterocyclic ligands, with the potentials being more negative with basic ligands. The ligand-centered-redox waves for 1a, 1b, 2a, and 2b were observed as split waves (delta E1/2 = 90-140 mV), the extent of the splitting being larger for the cis isomer and largest for the pyrazine complexes. Electronic interaction between the two ligands through the [Re6(mu 3-S)8]2+ core has been suggested. The second ligand-reduction wave was also observed for 3a and 3b, the potential being shifted positively to coalesce with the first reduction wave on addition of the weak proton donor imidazole. This is accounted for by the proton-coupled redox reaction at the free pyridyl site of the 4,4'-bipyridine ligands. All of the complexes show luminescence in acetonitrile at room temperature. While the complexes of pyridine and 4-methylpyridine show photophysical characteristics (lambda em 740-750 nm, phi em 0.031-0.057, tau em 4.2-6.2 microseconds) similar to those (770 nm, 0.039, and 6.3 microseconds, respectively) of [Re6(mu 3-S)8Cl6]4-, emissions of other complexes are significantly weak with lambda em, phi em, and tau em values in the ranges 763-785 nm, 0.0010-0.0017, and 0.013-0.029 microsecond, respectively. Suggestions are given for the excited states localized on the cluster core and the ligand pi* orbitals.