Computation of magnetic shielding to simultaneously validate a crystal structure and assign a solid-state NMR spectrum

The validity of the structure of diterbutaline sulphate diacetic acid solvate in the Cambridge Crystallographic Database (code ZIYXAG) was checked using 13C solid-state NMR together with shielding computations and was found to be in error as far as the geometry of one acetic acid molecule is concerned. A new X-ray diffraction study confirmed the existence of an error and showed there was disorder in the molecule in question. Techniques of NMR crystallography were used to further understand the situation. Two-dimensional (13C, 1H) heteronuclear correlation experiments enabled the 1H chemical shifts to be determined, including those of the hydrogen-bonded protons. NMR was also used to monitor partial desolvation and the 13C spectrum of a new solvate, diterbutaline sulphate monoacetic acid, is reported. Heteronuclear correlation experiments on this new compound allowed most of its proton chemical shifts to be determined and showed that it had one hydrogen bond stronger than any of those in the diacetic acid solvate.

► Validation of X-ray structure by NMR and shielding computation.
► Revision of X-ray structure to include disorder.
► Solid-state proton chemical shifts via HETCOR.
► Partial desolvation to give new compound.