The synthesis of the novel bidentate ligands 4,4'-bis(trifluoromethyl)-2,2'-bipyridine (4,4'-BTFMB), 5,5'-bis-(trifluoromethyl)-2,2'-bipyridine (5,5'-BTFMB), and 4,4',5,5'-tetrakis(trifluoromethyl)-2,2'-bipyridine (4,4',5,5'-TTFMB) is reported. The photophysical and photochemical properties of a series of tris-chelate complexes [Ru(bpy)"(BTFMB)3-n]2+ ( = 0-2; bpy = 2,2'-bipyridine) are described. From spectroscopic and electrochemical measurements, it has been shown that the BTFMB ligand has lower lying ir* levels which not only lead to significant changes in ground-and excited-state redox potentials but also exert relatively large effects on absorption and emission spectral properties. From measurements of emission lifetime and quantum yield at room temperature, the radiative (kr) and nonradiative (knr) decay rate constants were obtained. Trends in k", properties are understandable on the basis of the energy gap law. Possible applications in excited-state redox chemistry are also discussed.

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Isotactic polypropylene (iPP) has been crystallized in the presence of talc under the quiescent state and shear flow of injection molding. The resulting morphology has been investigated by means of polarizing microscopy, transmission electron microscopy, and wide angle X‐ray diffraction. In the quiescent state, the iPP lamellae grew from the surface of talc and the transcrystalline region was formed at the interface between iPP melt and the talc. The nucleation of iPP was very frequent on the cleavage plane of talc. The X‐ray diffraction pattern of the transcrystal showed a*‐axis orientation to the crystal growing direction. In injection‐molded samples of the talc‐filled iPP, the morphology of lamella growing from talc appeared as same as that of the transcrystal. However, the crystalline orientation of injection‐molded talc‐filled iPP, in which the b axis was oriented to the thickness direction and the a* and the c axis was oriented to the flow direction, was quite different from that of the transcrystal. This b‐axis orientation results from the orientation of the plate plane of talc, which induces the nucleation and the crystallization under shear flow. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1693–1703, 2001

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