1H and79Br NMR in 1,4-Didecyl-1,4-diazoniabicyclo[2.2.2]octane Dibromide and Diiodide

Abstract

Temperature dependence of 1H NMR spin-lattice relaxation time was measured in solid 1,4-didecyl-1,4-diazoniabicyclo[2.2.2]octane dibromide and diiodide (C10–DABCO–C10–Br2 and C10–DABCO–C10–I2). 79Br NMR spin-lattice relaxation time and chemical shift measurements in the high-temperature phase were also performed in C10–DABCO–C10–Br2. It was found that the cation rotates isotropically, while the anion diffuses at a correlation time of ca. 10−8 s in the high-temperature phase of C10–DABCO–C10–Br2. The activation energies for these modes are 30 and 34 kJ mol−1, respectively. Methyl reorientation is activated in the low-temperature phase (Ea=11.8 kJ mol−1 in C10–DABCO–C10–Br2 and Ea=12.0 kJ mol−1 in C10–DABCO–C10–I2). Near the phasetransition temperature some motion of decyl chain is observed (Ea=57 kJ mol−1 in C10–DABCO–C10–Br2 and Ea=35.5 kJ mol−1 in C10–DABCO–C10–I2).