Re-determination of the crystal structure of NaBr·Sucrose·2H 2O

Abstract

The NaBr·Sucrose·2H 2O complex crystallizes in the P2 12 12 1 space group with cell constants of a = 8.484(4), b = 9.745(2), c = 21.948(5) Å. The asymmetric unit consists of a Na-Br ion-pair, two water molecules, and one sucrose molecule. Inside the unit cell, there are four channels running along the b axis, which accommodate infinite arrays of iso-oriented Br −-Na +-2H 2O units. This arrangement is not far from a van der Waals packing of sugar molecules in which neutral solvated NaBr moieties are embedded. Calculations of the electrostatic potential spanned by the sucrose and water molecules show that the electrostatic field of polyhydroxylated ligands can be modified to fit different ionic arrangements by a simple mechanism involving rotation of hydroxyl groups.