STRUCTURE OF A ZEOLITE ZSM-5-BITHIOPHENE COMPLEX AS DETERMINED BY HIGH-RESOLUTION SYNCHROTRON X-RAY-POWDER DIFFRACTION

The structure of a zeolite ZSM-5 complex with ca. 4 molecules/unit cel l of bithiophene was determined by high-resolution synchrotron X-ray p owder diffraction. It adopts monoclinic symmetry in space group P2(1)/ n (a unique) between room temperature and 25 K, with refined lattice p arameters at 25 K of a = 20.0614(4), b = 19.8251(4), c = 13.3623(4) An gstrom, and alpha = 90.848(2)degrees. Structural modeling and Rietveld refinements showed that there are two crystallographically unique bit hiophene molecules, each with an occupancy factor of ca. 0.5. One bith iophene is localized at the center of the straight channels with one o f the rings residing at the intersection with the sinusoidal channels. The other molecule lies in the sinusoidal channels and projects parti ally into the straight channels. The relationship between polythiophen e chain length and the formation of conducting polythiophene molecular wires in the ZSM-5 framework is discussed.