XRPD as a powerful tool to exploit in organic electronics: shedding light on the first N,N',N''-trialkyldiindolocarbazole crystal structure

Abstract

The first crystal structure of a fully N-alkyl­ated diindolocarbazole derivative, namely, 5,8,14-tri­butyl­diindolo[3,2-b;2′,3′-h]carbazole (1, C36H39N3), has been determined from laboratory powder X-ray diffraction (PXRD) data. A com­plex trigonal structure with a high-volume unit cell of 12987 Å3 was found, with a very long a(=b) [52.8790 (14) Å] and a very short c [5.36308 (13) Å] unit-cell parameter (hexa­gonal setting). The detailed analysis of the inter­molecular inter­actions ob­served in the crystal structure of 1 highlights its potential towards the imple­mentation of this core as a semiconductor in organic thin-film transistor (OTFT) devices. Since the mol­ecule has a flat con­fig­uration reflecting its π-conjugated system, neighbouring mol­ecules are found to stack atop each other in a slipped parallel fashion via π–π stacking inter­actions between planes of ca 3.30 Å, with a centroid–centroid distance between the aromatic rings corresponding to the shortest axis of the unit cell (i.e. c). The alkyl­ation of the three N atoms proves to be a decisive feature since it favours the presence of C—H⋯π inter­actions in all directions, which strengthens the crystal packing. As a whole, PXRD proves to be a valuable option for the resolution of otherwise inaccessible organic crystal structures of inter­est in different areas.