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Blue Luminescent Rigid Molecular Rods Bearing N-7-Azaindolyl and 2,2‘-Dipyridylamino and Their Zn(II) and Ag(I) Complexes

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journal contribution
posted on 25.03.2003 by Youngjin Kang, Corey Seward, Datong Song, Suning Wang
To investigate the luminescent and thermal properties of organic compounds with rigid entities, a series of new blue/purple luminescent bridging ligands, 4,4‘-(N-7-azaindolyl)diphenylacetylene (5), 4-(N-7-azaindolyl)-4‘-(2,2‘-dipyridylamino)diphenylacetylene (6), 4,4‘-(2,2‘-dipyridylamino)diphenylacetylene (7), and 4,4‘-(dipyridylamino)diphenylbutadiyne (8) have been synthesized through Pd-mediated Sonogashira coupling. The structures of compounds 6 and 8 were determined by single-crystal X-ray diffraction analyses. Compounds 58 are luminescent in solution at room temperature, with emission λmax = 361, 382, 386, and 405 nm, respectively. At 77 K, compounds 58 exhibit both fluorescent and phosphorescent emission. The 2,2‘-dipyridylamino symmetrically substituted ligand 7 forms a linear dinuclear complex 9 with zinc(II) ions, in which the two pyridyl rings of the dipyridylamino portion are chelated to the metal center. However, with Ag(I) ions, ligand 7 forms a dinuclear complex (10), which displays a macrocyclic structure with only one of the two pyridyl rings from each dipyridylamino portion being coordinated to the silver atom. Both 9 and 10 exhibit luminescence in the near-UV region in CH2Cl2 at room temperature with λmax = 385 and 384 nm, respectively. The fluorescence of 7 can be partially quenched by either Zn2+ or H+. The behavior of ligands 8 toward Ag(I) and Zn(II) ions is similar to that of 7.