Switchable antenna: a star-shaped ruthenium/osmium tetranuclear complex with azobis(bipyridine) bridging ligands.
Switchable antenna: a star-shaped ruthenium/osmium tetranuclear complex with azobis(bipyridine) bridging ligands.
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DOI：
10.1002/chem.200701691
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发表时间：
2008-03
期刊：
影响因子：
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通讯作者：
J. Otsuki;Arata Imai;Katsuhiko Sato;Dong-Mei Li;Mayumi Hosoda;Masao Owa;T. Akasaka;Isao Yoshikawa;K. Araki;T. Suenobu;S. Fukuzumi
中科院分区：
文献类型：
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作者：
J. Otsuki;Arata Imai;Katsuhiko Sato;Dong-Mei Li;Mayumi Hosoda;Masao Owa;T. Akasaka;Isao Yoshikawa;K. Araki;T. Suenobu;S. Fukuzumi
制备了一个星形的Ru/Os四核配合物，其中一个中心的Os单元通过4,4”-偶氮（2,2'-联吡啶）（偶氮）桥接配体连接到三个外围的Ru单元，以研究其氧化还原态调节的独特光动力学。Ru/Os四核配合物在77k时显示出基于Ru的发光，而Ru/Os配合物的三电子还原（每个偶氮比一个）导致Os单元发光。Ru/Os配合物的光激发态迅速衰减为低能金属到配体的电荷转移态，其中激发电子以偶氮比（.-）的形式定位在偶氮比配体中。偶氮配体在单电子还原后，上述低能态变为光激发配合物不可用。因此，能量从ru基激发态转移到os基激发态成为可能。超快瞬态吸收测量表明，能量传递过程包括两个步骤；分子内电子从末端联吡啶配体（bpy(.-)）转移到偶氮比（2-），然后是金属到金属的电子转移。因此，Ru/Os四核配合物根据桥接配体的氧化还原状态将光能收集到中心Os单元中，成为可切换的天线。
A star-shaped Ru/Os tetranuclear complex, in which a central Os unit is linked to three peripheral Ru units by 4,4''-azobis(2,2'-bipyridine) (azobpy) bridging ligands, was prepared to examine the unique photodynamics regulated by its redox state. The Ru/Os tetranuclear complex exhibits Ru-based luminescence at 77 K, whereas the three-electron reduction (one for each azobpy) of the Ru/Os complex results in luminescence from the Os unit. The photoexcited state of the Ru/Os complex rapidly decays into low energy metal-to-ligand charge-transfer states, in which the excited electron is localized in the azobpy ligand in the form of azobpy(.-). Upon the one-electron reduction of the azobpy ligands, the above-mentioned low-energy states become unavailable to the photoexcited complex. As a result, an energy transfer from the Ru-based excited state to the Os-based excited state becomes possible. Ultrafast transient absorption measurements revealed that the energy transfer process consists of two steps; intramolecular electron transfer from the terminal bipyridine ligand (bpy(.-)) to form azobpy(2-) followed by a metal-to-metal electron transfer. Thus, the Ru/Os tetranuclear complex collects light energy into the central Os unit depending on the redox state of the bridging ligands, qualifying as a switchable antenna.