Reorientation of DABCO (1,4-diazabicyclo[2.2.2]octane) in hydrogen-bonded 1:2 molecular complexes DABCO-2(SBA) with substituted benzoic acids SBA

Abstract

The molecular complexes of DABCO-2(SBA) with substituted benzoic acids SBA, which have the hydrogen-bonded trimeric unit, were prepared to investigate the DABCO reorientation in the trimeric unit. By the analysis of the temperature dependence of 1H NMR spin-lattice relaxation time, the correlation time of the DABCO reorientation was determined as a function of the temperature. It is suggested that a change of potential energy of the reorientation is caused with increasing rate of reorientation resulting in a structure change of the trimeric unit to a centrosymmetric structure. The correlation between the activation energy of the DABCO reorientation and the bond nature of the hydrogen bond involved in the trimeric unit is also discussed.