2.2.1. Powder X-ray Diffraction (PXRD)

Powder X-ray diffraction patterns were obtained on a PANalytical X'Pert PRO MPD diffractometer (Malvern Panalytical, Almelo, Netherlands) in transmission configuration using Cu Kα1+2 radiation (λ = 1.5418 Å) with a focalizing elliptic mirror and a PIXcel detector working at a maximum detector's active length of 3.347◦. Capillary geometry has been used with samples placed in glass capillaries (Lindemman) of 0.5 mm of diameter measuring from 2 to 60◦ in 2θ, with a step size of 0.026◦ and a total measuring time of 30 min. Flat geometry has been used for routine samples sandwiched between low absorbing films (polyester of 3.6 microns of thickness) measuring 2theta/theta scans from 2 to 40◦ in 2θ with a step size of 0.026◦ and a measuring time of 80 seconds per step.

Powder X-ray diffraction patterns of forms III and SCHCl3-H2O were obtained using synchrotron radiation at ALBA's beam line BL04-MSPD using Mythen detector [16]. The wavelength, 0.63493 Å for form III and 0.61927 Å for SCHCl3-H2O, was selected with a double-crystal Si (111) monochromator and determined from a Si640d NIST standard (a = 5.43123 Å) measurement. The diffractometer is equipped with a so-called MYTHEN detector system especially suited for time-resolved experiments. The capillary of 0.7 mm containing the sample was rotated during data collection to improve diffracting particle statistics. The data acquisition time was 10 min per pattern, and the final treated data are the addition of ten acquisitions to attain very good signal-to-noise ratio over the angular range 0.5–43.6◦ (2θ) at 300K. Both powder diffraction patterns were indexed using DICVOL06 [17], and the obtained cell parameters were refined via pattern matching with Dajust software [18]. The crystal structures were solved with the direct-space strategy TALP [19] introducing the bond distances and angles from the single crystal structure of form I as restraints. Crystal structure solution was followed by the location of the solvent molecules in the difference electron density map and a restrained Rietveld refinement with RIBOLS to obtain the final crystal structures. H-atoms were placed to calculated positions after the final refinement.

Variable temperature experiments of S3CHCl3-H2O sample were performed at the ALBA Synchrotron using a Cyberstar hot gas blower with an Eurotherm temperature controller (Eurotherm, Worthing, UK) and continuously collecting diffraction data during the heating and cooling ramps (30◦ to 230◦ and 230◦ to 30◦ at 2◦/min, 18 sec/pattern). A longer measurement (180s) was performed at room temperature.
