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The 1,1,2-triphenylethanol molecule, Ph2(PhCH2)COH (

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Dynamic properties of the hydroxyl groups in a selectively deuterated crystalline sample of ferrocene-1,l'-diylbis(diphenylmethano1) (FBDPM) have been studied via variable-temperature wide-line *H NMR spectroscopy and high-resolution I3C NMR spectroscopy. In crystalline FBDPM, the molecules form hydrogenbonded dimers, with the 0 atoms of the four hydroxyl groups involved in this hydrogen bonding defining a folded trapezium. Each hydroxyl H atom is disordered between two equally populated positions, from which it is inferred that there are two plausible arrangements (clockwise and anticlockwise) of the eight-membered ring hydrogen bonded unit. The temperature dependences of the quadrupole echo 2H NMR line shape in the temperature range 293-370 K, the 2H NMR spin-lattice relaxation time in the temperature range 313-428 K, and the I3C CPMAS NMR spectrum in the temperature range 205-253 K demonstrate that the hydrogenbonding arrangement is dynamic; this dynamic process is interpreted as interconversion between the clockwise and anticlockwise hydrogen-bonding arrangements. The observed temperature dependence of the NMR spectra is consistent with the following dynamic models: (i) transfer of each hydroxyl H atom between adjacent hydroxyl 0 atoms; (ii) a two-site n jump motion of each hydroxyl group about its C -0 bond. In either case, it is inferred that the motions of the four hydroxyl groups in the hydrogen-bonded dimer are highly correlated.In general, these dynamic models could be distinguished on the basis of *H NMR spectroscopy, but for the specific geometry of the intermolecular hydrogen-bonding arrangement in FBDPM, both of these models fit the *H NMR data. On the assumption of Arrhenius behavior for the temperature dependence of the jump frequency, the activation energy for the dynamic process is estimated (from 2H NMR spin-lattice relaxation time measurements and 2H NMR line-shape analysis) to be in the range 53-65 kJ mol-'.