Preparation, X-ray structure and properties of a hexabrominated, symmetric indole trimer and its TCNQ adduct: a new route to functional molecular systems

Reaction of indole with Br2 led to isolation of an indole trimer 2, formed by linking the 2- and 3-positions of each indole to form a central aromatic ring, and brominated at the 5- and 6-positions of each indole. The X-ray structure of [2]·acetone·2DMF showed π-stacking of the planar aromatic molecules with two different overlap modes with interplanar distances of 3.287 Å and 3.378 Å. Cyclic voltammetry showed one reversible oxidation for 2 and phosphorescence from frozen ethanol solution was observed. The X-ray structure of the adduct [2][TCNQ]2·4DMSO was determined and showed a mixed stack arrangement where 2 alternates with two adjacent TCNQ molecules.