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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-beta-d-glucopyranoside, Glc-pyta = 2-(4-(2-pyridyl)-1,2,3-triazol-1-yl)ethyl beta-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 group P2(1)/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 x 10(3) M(-1) cm(-1)) compared with [ReCl(CO)(3)(bpy)] (371 nm, 3.35 x 10(3) 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 mus in 2-methyltetrahydrofuran at 77 K, which is longer than that of [ReCl(CO)(3)(bpy)] (3.17 micros). 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.

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The early stage in the nucleation and subsequent aggregative particle growth of the colloidal platinum (Pt) dispersions produced by photoreduction in an aqueous ethanol solution of poly(N-vinyl-2-pyrrolidone) (PVP) was quantitatively investigated by means of in situ quick XAFS (QXAFS) measurements. The stages of the reduction-nucleation and the association process (aggregative particle growth and Ostwald ripening) of Pt atoms to produce Pt nanoparticles was successfully discriminated in course of the photoreduction time. The present QXAFS analysis indicated that Pt nuclei (i.e., (Pt(0))(m) nucleates approximately m = 4) were continuously produced in the reduction-nucleation process at the early time, followed by the aggregative particle growth with the autocatalytic reduction of Pt ionic species on the surface of Pt nuclei to produce Pt nanoparticles. Subsequently the particle growth proceeded via Ostwald ripening, resulting in the production of larger Pt nanoparticles at a later time. It was also found that the aggregative particle growth follows a sigmoidal profile well described either by the solid-state kinetic model or by the chemical-mechanism-based kinetic model, specifically the Avrami-Erofe'ev or Finke-Watzky models. The difference in terms of the formation mechanism was observed between the reduction of Pt(IV)Cl(6)(2-) and Pt(II)Cl(4)(2-) as a source material. Also presented is that the addition of the photoactivator such as benzoin, benzophenone, and acetophenone in the system is very effective to enhance the rate for the formation of Pt nanoparticles.