Molecular motions and phase transitions in solid bis-n-propylammonium pentabromoantimonate

A nuclear magnetic resonance study of molecular motion in solid tris (n-propylammonium) enneachlorodiantimonate (III) (n-C3H7NH3)3Sb2Cl9

Proton magnetic resonance second moment and spin-lattice relaxation time were carried out on polycrystalline tris (n-propylammonium) enneachlorodiantimonate (III), (n-C3H7NH3)3Sb2Cl9, in the temperature range of 10-370 K. The second moment measurements show that the structure is not rigid on the NMR scale at 10 K, the lowest temperature studied, and that CH3 and NH3 groups execute rotations about C3 axis. The proton spin-lattice relaxation measurements reveal two minima due to the motions of the amino and methyl groups. Analysis of the relaxation data yields the activation energy barriers of 11.0 kJ mol(-1) and 5.8 kJ mol(-1), respectively, for the NH3 and CH3 groups' motion. NMR data confirm the phase transition at Tc = 232 K, known from different studies.

1H NMR studies of molecular dynamics in polycrystalline catecholamines

The proton dynamics in phenylephrine hydrochloride, isoprenaline hydrochloride and norephedrine hydrochloride have been monitored by measuring the temperature dependence of the 1H spin-lattice relaxation times. The results are interpreted as due to C3-hindered reorientation of the NH3 and CH3 groups. The activation parameters have been determined.

Proton dynamics in solid noradrenaline hydrochloride

The temperature dependencies of the proton spin-lattice relaxation times and second moment of the 1H nuclear magnetic resonance line have been measured for noradrenaline hydrochloride. Two symmetric minima of T1 are observed. They can be explained in terms of reorientation of the ammonium groups and proton transfer in the hydrogen bond. The activation parameters have been determined.