Two isostructural halogen derivatives of 9-ethylcarbazole: crystal structure, Hirshfeld surface analysis, and structural comparison with other simple analogs
文摘
This article describes a detailed study of the molecular packing and intermolecular interactions in crystals of two derivatives of 9-ethylcarbazole, i.e., 3-chloro- and 3-bromo-9-ethylcarbazole (1 and 2, respectively). A significance of this study lies both in the comparison drawn between the crystal structures of these compounds and those of several of their simple analogs [i.e., 3,6-dibromo-9-ethylcarbazole (3), 3,6-dibromo-9-methylcarbazole (4), 3,6-dibromocarbazole (5), 3-bromocarbazole (6), 3,6-diiodocarbazole (7), 9-ethylcarbazole (8), 9-methylcarbazole (9) and carbazole (10)], and in the preliminary assessment of their suitability as active materials for organic electronics. This comparison shows a close similarity in the packing of molecules of three of them (i.e., 3, 4, 6) that form the π-stacks along the shortest crystallographic axes, with a substantial spatial overlap between adjacent molecules in the stacks, depending mainly on the length of substituent at position 9 of carbazole skeleton and on the ratio of (%C···H)/(%C···C) interactions. Similar to them, in the crystal structures of 1 and 2 there is slipped face-to-face π···π interaction, but in contrast this interaction connects two molecules of these compounds into the dimers that are further connected by C–H···π interaction. The molecular packing in crystals of these compounds is intermediate between the arrangement of molecules of 3, 4, and 6, where the slipped π-stacking is predominant, and the typical herringbone packing in compounds 5 and 7-strong class="EmphasisTypeBold">10. Thus, it can be supposed that out of ten compounds analyzed here, only 3, 4, and 6 will turn to be the most promising materials for device applications (particularly for field-effect transistors).