Experimental and predicted crystal energy landscapes of chlorothiazide

An experimental search for physical forms of the thiazide diuretic compound chlorothiazide comprising 402 different crystallizations identified one nonsolvated form and ten crystalline solvates. There are five distinct conformations in the experimental crystal structures which are in good agreement with the conformational minima found by ab initio optimization of the isolated molecule structure. An approximate rigid-body crystal energy landscape using these five conformations produced a diverse range of low energy crystal structures, with the anhydrous structure among the most stable. Inspection of the molecular packing adopted in both the experimental and predicted structures highlighted a number of chlorothiazide···chlorothiazide motifs that result from packing the different conformers. Specifically, four bimolecular face-to-face motifs were observed in most of the predicted structures and all of the experimental structures. The role of these robust intermolecular packing motifs and of the organic solvent molecules in stabilizing the experimental solvate structures of chlorothiazide is discussed. The results highlight the value of the approximate crystal energy landscape for flexible organic molecules in assisting with the interpretation of solid-state diversity in chlorothiazide crystal structures and identifying key stabilizing packing features.