Efficient Light Harvesting and Energy Transfer in a Red Phosphorescent Iridium Dendrimer

详细信息    查看全文

• 作者：Yang-Jin Cho ; Seong Ahn Hong ; Ho-Jin Son ; Won-Sik Han ; Dae Won Cho ; Sang Ook Kang
• 刊名：Inorganic Chemistry
• 出版年：2014
• 出版时间：December 15, 2014
• 年：2014
• 卷：53
• 期：24
• 页码：13136-13141
• 全文大小：366K
• ISSN：1520-510X

文摘

A series of red phosphorescent iridium dendrimers of the type [Ir(btp)₂(pic-PC_n)] (Ir-G_n; n = 0, 1, 2, and 3) with two 2-(benzo[b]thiophen-2-yl)pyridines (btp) and 3-hydroxypicolinate (pic) as the cyclometalating and ancillary ligands were prepared in good yields. Dendritic generation was grown at the 3 position of the pic ligand with 4-(9H-carbazolyl)phenyl dendrons connected to 3,5-bis(methyleneoxy)benzyloxy branches (PC_n; n = 0, 2, 4, and 8). The harvesting photons on the PC_n dendrons followed by efficient energy transfer to the iridium center resulted in high red emissions at 鈭?00 nm by metal-to-ligand charge transfer. The intensity of the phosphorescence gradually increased with increasing dendrimer generation. Steady-state and time-resolved spectroscopy were used to investigate the energy-transfer mechanism. On the basis of the fluorescence quenching rate constants of the PC_n dendrons, the energy-transfer efficiencies for Ir-G₁, Ir-G₂, and Ir-G₃ were 99, 98, and 96%, respectively. The energy-transfer efficiency for higher-generation dendrimers decreased slightly because of the longer distance between the PC dendrons and the core iridium(III) complex, indicating that energy transfer in Ir-G_n is a F枚rster-type energy transfer. Finally, the light-harvesting efficiencies for Ir-G₁, Ir-G₂, and Ir-G₃ were determined to be 162, 223, and 334%, respectively.