Ab initio structural determination of 2-(2-pyridyl)imino-N-(2-thiazolin-2-yl)thiazolidine from powder diffraction data

Abstract Structural determination using X-ray powder diffraction is usually restricted to relatively simple structures, although powder diffraction data are frequently used to refine, via the Rietveld method, approximately known structures. In this work, the relatively complex crystalline structure of a compound of high pharmaceutical interest (C 11 H 12 N 4 S 2 ) has been firstly ab initio determined from its X-ray powder diffraction pattern and subsequently refined by the Rietveld method. This refined structure is in excellent agreement with that obtained previously from single-crystal data. As a consequence of the severe overlapping between adjacent reflections, direct methods failed, whereas we obtained good outcomes with ‘real space’ methods. This work shows that within the current state-of-art (hardware, software, numerical methods, etc.), relatively complex structures can be afforded by means of powder diffraction.