Investigation of solute–solvent interactions in a dithiophosphoroorganic carbohydrate derivative by means of X-ray analysis and solid state NMR

Abstract

Bis[6-O,6′-O-(1,2∶3,4-diisopropylidene-α-D-galactopyranosyl)thiophosphoryl] disulfide 1 (C₄₈H₇₆O₂₄P₂S₄) crystallized from polar and/or nonpolar solvents forms different inclusion complexes and solvates. The X-ray data for complexes of 1 with propan-2-ol (1a) and acetone (1b) are reported. From DSC measurements it is apparent that with loss of the solvent, crystals undergo complex rearrangements below the melting point forming the 1c modification. Each form is characterized by ³¹P CP/MAS experiment. The analysis of the ³¹P δ_ii principal elements of the chemical shift tensor suggests that distinction of δ₃₃ for different modifications is related to O–H· · ·SP and C–H· · ·SP intermolecular contacts. ²H NMR spectroscopy is employed to investigate the mechanism of phase reorientation and molecular dynamics of methyls of the isopropylidene blocking groups. At ambient temperature, the C_3v jump of the methyl group and additional small-amplitude motion of the five membered ring is deduced from line-shape analysis of a ²H QUADECHO experiment. During the change of sample composition at 370 K, fast molecular motion of the methyl groups is observed while the SP–S–S–PS backbone remains rigid. From variable temperature ²H T₁ inversion–recovery measurements it is concluded that the E_a of the C_3v jump strongly depends on molecular packing.