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Issue 25, 2008
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Syntheses, structural characterization and photophysical properties of 4-(2-pyridyl)-1,2,3-triazole rhenium(I) complexes

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Abstract

Novel chelators, i.e., 4-(2-pyridyl)-1,2,3-triazole derivatives, were synthesized by means of Cu(I)-catalyzed 1,3-dipolar cycloaddition and used to prepare luminescent Re(I) complexes [ReCl(CO)3(Bn-pyta)], [ReCl(CO)3(AcGlc-pyta)] and [ReCl(CO)3(Glc-pyta)] (Bn-pyta = 1-benzyl-4-(2-pyridyl)-1,2,3-triazole, AcGlc-pyta = 2-(4-(2-pyridyl)-1,2,3-triazol-1-yl)ethyl 2,3,4,6-tetra-O-acetyl-β-D-glucopyranoside, Glc-pyta = 2-(4-(2-pyridyl)-1,2,3-triazol-1-yl)ethyl β-D-glucopyranoside). X-Ray crystallography of Bn-pyta and Glc-pyta indicated an azocompound-like structure while the 1,2,4-triazole isomer has an azine character. [ReCl(CO)3(Bn-pyta)] crystallized in the monoclinic system with space groupP21/n. Bn-pyta ligand coordinates with the nitrogen atoms of the 2-pyridyl group and the 3-position of 1,2,3-triazole ring, which is a very similar coordinating fashion to that of the 2,2′-bipyridine derivative. The glucoconjugated Re(I) complexes [ReCl(CO)3(AcGlc-pyta)] and [ReCl(CO)3(Glc-pyta)] hardly crystallized, and were analyzed by applying extended X-ray absorption fine structure (EXAFS) analysis. The EXAFS analyses suggested that the glucoconjugation at the 1-position of the 1,2,3-triazole makes no influence to the coordinating fashion of 4-(2-pyridyl)-1,2,3-triazole. [ReCl(CO)3(Bn-pyta)] showed a blue-shifted maximum absorption (333 nm, 3.97 × 103 M−1 cm−1) compared with [ReCl(CO)3(bpy)] (371 nm, 3.35 × 103 M−1 cm−1). These absorptions were clearly assigned to be the mixed metal–ligand-to-ligand charge transfer (MLLCT) on the basis of time-dependent density functional theory calculation. The luminescence spectrum of [ReCl(CO)3(Bn-pyta)] also showed this blue-shifted feature when compared with that of [ReCl(CO)3(bpy)]. The luminescence lifetime of [ReCl(CO)3(Bn-pyta)] was determined to be 8.90 μs in 2-methyltetrahydrofuran at 77 K, which is longer than that of [ReCl(CO)3(bpy)] (3.17 μs). The blue-shifted electronic absorption and elongated luminescence lifetime of [ReCl(CO)3(Bn-pyta)] suggested that 4-(2-pyridyl)-1,2,3-triazole functions as an electron-rich bidentate chelator.

Graphical abstract: Syntheses, structural characterization and photophysical properties of 4-(2-pyridyl)-1,2,3-triazole rhenium(i) complexes

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Publication details

The article was received on 30 Nov 2007, accepted on 08 Apr 2008 and first published on 22 May 2008


Article type: Paper
DOI: 10.1039/B718538C
Citation: Dalton Trans., 2008, 3292-3300
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    Syntheses, structural characterization and photophysical properties of 4-(2-pyridyl)-1,2,3-triazole rhenium(I) complexes

    M. Obata, A. Kitamura, A. Mori, C. Kameyama, J. A. Czaplewska, R. Tanaka, I. Kinoshita, T. Kusumoto, H. Hashimoto, M. Harada, Y. Mikata, T. Funabiki and S. Yano, Dalton Trans., 2008, 3292
    DOI: 10.1039/B718538C

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