Kobayashi Atsushi, Arata Ryuya, Ogawa Tomohiro, Yoshida Masaki, Kato Masako
Department of Chemistry, Faculty of Science, Hokkaido University , North-10 West-8, Kita-ku, Sapporo, Hokkaido 060-0810, Japan.
Inorg Chem. 2017 Apr 17;56(8):4280-4288. doi: 10.1021/acs.inorgchem.6b02578. Epub 2017 Jan 12.
Two luminescent pyrazine-bridged dinuclear Cu(I) complexes, namely, {Cu(PPh)(HO)}(μ-MeOpyz){Cu(PPh)(CHCN)} and {Cu(PPh)(HO)}(μ-MeOpyz){Cu(PPh)(HO)} (HO-Cu-AN and HO-Cu-HO; PPh = triphenylphosphine, MeOpyz = 2-methoxypyrazine), were successfully synthesized and characterized by single-crystal X-ray diffraction and luminescence measurements. X-ray analysis revealed that the water molecules are coordinated to both Cu(I) ions to form almost the same PNO coordination structure in HO-Cu-HO, whereas one of the two Cu ions in HO-Cu-AN was coordinated by acetonitrile instead of water to form a different PN coordination environment. The asymmetric HO-Cu-AN exhibits very bright yellow-green emission with a high emission quantum yield (λ = 550 nm, Φ = 0.70) at room temperature in the solid state in spite of the coordination of water molecule, which usually tends to deactivate the emissive state through O-H vibration. The intense emission at room temperature is a result of thermally activated delayed fluorescence, and the remarkable temperature dependence of emission lifetimes indicates the existence of unique multiple emission states for the asymmetric dinuclear complex. In contrast, the emission of HO-Cu-HO was observed at longer wavelengths with remarkably a lower quantum yield (λ = 580 nm, Φ = 0.05). Time-dependent density functional theory calculations suggested that the emission could result from the metal-to-ligand charge-transfer transition state. However, it could be rapidly deactivated by the structural distortion around the Cu ion with a less-bulky coordination environment in HO-Cu-HO.
成功合成了两种发光的吡嗪桥联双核铜（I）配合物，即{Cu(PPh)(HO)}(μ-MeOpyz){Cu(PPh)(CHCN)}和{Cu(PPh)(HO)}(μ-MeOpyz){Cu(PPh)(HO)}（HO-Cu-AN和HO-Cu-HO；PPh = 三苯基膦，MeOpyz = 2-甲氧基吡嗪），并通过单晶X射线衍射和发光测量对其进行了表征。X射线分析表明，水分子与两个Cu（I）离子配位，在HO-Cu-HO中形成几乎相同的PNO配位结构，而HO-Cu-AN中两个Cu离子之一由乙腈而非水配位，形成不同的PN配位环境。尽管有水分子配位，通常倾向于通过O-H振动使发光态失活，但不对称的HO-Cu-AN在室温下的固态中仍表现出非常明亮的黄绿色发射，具有高发射量子产率（λ = 550 nm，Φ = 0.70）。室温下的强发射是热激活延迟荧光的结果，发射寿命的显著温度依赖性表明不对称双核配合物存在独特的多重发射态。相比之下，HO-Cu-HO的发射在更长波长处观察到，量子产率显著较低（λ = 580 nm，Φ = 0.05）。含时密度泛函理论计算表明，发射可能源于金属到配体的电荷转移跃迁态。然而，在HO-Cu-HO中，由于Cu离子周围配位环境体积较小，结构畸变可能会使其迅速失活。
