Excited-state properties of octahedral hexarhenium(III) complexes with redox-active N-heteroaromatic ligands.
Excited-state properties of octahedral hexarhenium(III) complexes with redox-active N-heteroaromatic ligands.
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DOI：
10.1021/ic9015788
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发表时间：
2010-01
影响因子：
4.6
通讯作者：
T. Yoshimura;Chiaki Suo;K. Tsuge;S. Ishizaka;K. Nozaki;Y. Sasaki;N. Kitamura;A. Shinohara
中科院分区：
文献类型：
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作者：
T. Yoshimura;Chiaki Suo;K. Tsuge;S. Ishizaka;K. Nozaki;Y. Sasaki;N. Kitamura;A. Shinohara
含4-苯基吡啶(PPY)或1，2-二(4-吡啶基)乙烷(BPe)((n-C(4)H(9))(4)N)[mer-{Re(6)S(8)Cl(3)(ppy)(3)}]((Bu(4)N)[1])的新的硫化物封端的八面体六面体六(III)配合物，((n-C(4)H(9))(4)N)(2)[trans-{Re(6)S(8)Cl(4)(ppy)(2)}]((Bu(4)N)(2)[2a])，((n-C(4)H(9))(4)N)(2)[cis-{Re(6)S(8)Cl(4)(ppy)(2)}]((Bu(4)N)(2)[2b])，制备了((n-C(4)H(9))(4)N)(2)[trans-{Re(6)S(8)Cl(4)(bpe)(2)}]((Bu(4)N)(2)[3a])和((n-C(4)H(9))(4)N)(2)[cis-{Re(6)S(8)Cl(4)(bpe)(2)}]((Bu(4)N)(2)[3b])，并对(Bu(4)N)(2)[2a]和(Bu(4)N)(2)[3a]进行了X射线单晶结构测定。研究了这些配合物在298K的乙腈溶液中以及298K和80K的固态条件下的光物理性质，以及已知的4，4‘-联吡啶类似物((n-C(4)H(9))(4)N)[mer-{Re(6)S(8)Cl(3)(bpy)(3)}]((Bu(4)N)[4])的光物理性质。((n-C(4)H(9))(4)N)(2)[trans-{Re(6)S(8)Cl(4)(bpy)(2)}]((Bu(4)N)(2)[5a])和((n-C(4)H(9))(4)N)(2)[cis-{Re(6)S(8)Cl(4)(bpy)(2)}]((Bu(4)N)(2)[5b])。[5a](2-)和[5b](2-)在溶液和固体中的光物理数据与其他配合物有显著不同。根据[2a](2-)和[5a](2-)的实验观测和密度泛函理论计算，[5a](2-)和[5b](2-)表现出金属(Re(6)S(8)核)到配体(BPY)的电荷转移(MLCT型)发射。这是第一次明确地证明了六茂金属络合物的MLCT类型的发射。在排放[1](-)、[2a](2-)、[2b](2-)和[4](-)的情况下，如果存在MLCT成分，这些成分是次要的；这主要可以解释为核心内电子跃迁的贡献。[3a](2-)和[3b](2-)的发射几乎完全归属于Re(6)S(8)核内的电子跃迁。三(Bpy)配合物([4](-))的双(Bpy)配合物([5a](2-)和[5b](2-))的不同发射特性是由于Re(6)S(8)核上氮施主数目的增加而使Re(6)S(8)核的能量稳定到比bpy配体pi*轨道能量低的水平。另一方面，研究表明，双(Ppy)([2a](2-)和[2b](2-))和双(BPE)配合物([3a](2-)和[3b](2-))的发射最好地被每个N-杂芳族配体的较高的pi*能级所表征，这导致在配合物的发射激发态下具有更强的金属特征。
New sulfide-capped octahedral hexarhenium(III) complexes containing 4-phenylpyridine (ppy) or 1,2-bis(4-pyridyl)ethane (bpe) ((n-C(4)H(9))(4)N)[mer-{Re(6)S(8)Cl(3)(ppy)(3)}] ((Bu(4)N)[1]), ((n-C(4)H(9))(4)N)(2)[trans-{Re(6)S(8)Cl(4)(ppy)(2)}] ((Bu(4)N)(2)[2a]), ((n-C(4)H(9))(4)N)(2)[cis-{Re(6)S(8)Cl(4)(ppy)(2)}] ((Bu(4)N)(2)[2b]), ((n-C(4)H(9))(4)N)(2)[trans-{Re(6)S(8)Cl(4)(bpe)(2)}] ((Bu(4)N)(2)[3a]), and ((n-C(4)H(9))(4)N)(2)[cis-{Re(6)S(8)Cl(4)(bpe)(2)}] ((Bu(4)N)(2)[3b]) were prepared, and X-ray single-crystal structure determination was carried out for (Bu(4)N)(2)[2a] and (Bu(4)N)(2)[3a]. The photophysical properties of these complexes were studied both in acetonitrile at 298 K and in the solid state at 298 and 80 K, along with those of the known 4,4'-bipyridine (bpy) analogues ((n-C(4)H(9))(4)N)[mer-{Re(6)S(8)Cl(3)(bpy)(3)}] ((Bu(4)N)[4]), ((n-C(4)H(9))(4)N)(2)[trans-{Re(6)S(8)Cl(4)(bpy)(2)}] ((Bu(4)N)(2)[5a]), and ((n-C(4)H(9))(4)N)(2)[cis-{Re(6)S(8)Cl(4)(bpy)(2)}] ((Bu(4)N)(2)[5b]). The photophysical data of [5a](2-) and [5b](2-) in solution and in the solid state were significantly different from those of other complexes. On the basis of experimental observations of [2a](2-) and [5a](2-) and density-functional theory (DFT) calculations, it was concluded that [5a](2-) and [5b](2-) exhibited metal (Re(6)S(8) core)-to-ligand (bpy) charge transfer (MLCT) type emission. This is the first unambiguous demonstration of MLCT type emissions for the hexarhenium complexes. The MLCT components, where present, are only minor in the case of the emissions of [1](-), [2a](2-), [2b](2-), and [4](-); these can be explained primarily as the contributions of the intracore electronic transitions. The emissions of [3a](2-) and [3b](2-) can be assigned almost completely to the electronic transitions within the Re(6)S(8) core. The different emission characteristics of the bis(bpy) complexes ([5a](2-) and [5b](2-)) from the tris(bpy) complex ([4](-)) are a result of the increase in the number of nitrogen donors on the Re(6)S(8) core, which stabilizes the Re(6)S(8) core energy to a lower level than the energy of the bpy ligand pi* orbital. On the other hand, it has been shown that the emissions of the bis(ppy) ([2a](2-) and [2b](2-)) and bis(bpe) complexes ([3a](2-) and [3b](2-)) are best characterized by the higher pi* energy level of each N-heteroaromatic ligand, which lead to a stronger metal character in the emissive excited state of the complex.