How do the crystalline forms of dabigatran etexilate mesylate differ structurally and how were these differences characterized?

Dabigatran etexilate mesylate exists in different crystalline forms (polymorphs and a hemihydrate).

Anhydrous form I of dabigatran etexilate mesylate has a monoclinic crystal lattice (C2/c), while anhydrous form II has a triclinic lattice (P1), and the hemihydrate also crystallizes in a monoclinic space group (P2/c). The forms also exhibit distinct crystal morphologies: form I typically forms spherical-like agglomerates, form II has an ill-defined habit, and the hemihydrate appears as long needle-like crystals. These differences were characterized using various techniques, including microscopy, X-ray powder diffraction (XRPD), thermal analysis (DSC and TG), and IR and Raman spectroscopy. Single crystal structure data for all three room-temperature accessible forms of dabigatran etexilate mesylate was obtained using electron diffraction.