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Synthesis and Photophysical Properties of Neutral Luminescent Rhenium-Based Molecular Rectangles

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journal contribution
posted on 12.09.2003, 00:00 authored by T. Rajendran, Bala. Manimaran, Rong-Tang Liao, Ren-Jay Lin, P. Thanasekaran, Gene-Hsiang Lee, Shie-Ming Peng, Yen-Hsiang Liu, I-Jy Chang, S. Rajagopal, Kuang-Lieh Lu
A series of neutral luminescent molecular rectangles [{Re(CO)3(μ-bpy)Br}{Re(CO)3(μ-L)Br}]2 (14) having fac-Re(CO)3Br as corners and 4,4‘-bipyridine (bpy) as the bridging ligand on one side and other bipyridyl ligands of varying length (L) on the other side have been synthesized and characterized. The crystal structure of 1 shows a rectangular cavity with the dimensions of 11.44 × 7.21 Å. When the cavity size is tuned from 1 to 4, a dimension of 11.4 × 20.8 Å could be achieved, as revealed by the molecular modeling. These rectangles exhibit luminescence in solution at room temperature. In particular, compound 4 containing 1,4-bis(4‘-pyridylethynyl)benzene (bpeb) as bridging ligand shows the excited-state lifetime of 495 ns. Fine-tuning of the cavity size of the rectangles improves their excited-state properties. These properties facilitate the study of excited-state electron-transfer reactions with electron acceptors and donors and host−guest binding. Crystallographic information:  1·6CH3COCH3 is monoclinic, P21/c, with a = 12.0890(2), b = 24.2982(2), and c = 12.8721(2) Å, β = 107.923(1)°, and Z = 2.