A redetermination of 2-(6-diethyl-amino-3-diethyl-iminio-3H-xanthen-9-yl)benzoate-ethyl gallate (1/1) at room temperature.

TLDR: This work has found the RBB molecule to be disordered with a methyl group of one ethyl substituent of a diethylamino group at one extremity of the xanthene unit disordered over two positions, which leads to four kinds of RBB conformations, which, in turn, results in the formation of 16 discrete RBB⋯EG⋰EG ⋯RBB dimers in the crystal.

Abstract: The title compound, C28H30N2O3·C9H10O5, is a well known red leuco complex of 2-(6-diethyl­amino-3-diethyl­iminio-3H-xanthene-9-yl)benzoate (rhodamine B base abbreviated to RBB: leuco dye) with ethyl gallate (EG: developer). The structure of the complex at room temperature has recently been reported by Sekiguchi, Takayama, Gotanda & Sano [(2007) Chem. Lett. 36, 1010–1011]. The RBB–EG complex forms a dimer (RBB⋯EG⋯EG⋯RBB) through inter­molecular O—H⋯O hydrogen bonds. In a subsequent re-examination of the structure at room temperature, we found the RBB mol­ecule to be disordered with a methyl group of one ethyl substituent of a diethyl­amino group at one extremity of the xanthene unit disordered over two positions [occupancies: 0.735 (5)/0.265 (5)]. Furthermore, at the other end of the xanthene residue, the entire diethyl­amino substituent (i.e. the N atom and the associated C and H atoms) was also disordered over two sites with occupancies 0.653 (7)/0.347 (7). This leads to four kinds of RBB conformations, which, in turn, results in the formation of 16 discrete RBB⋯EG⋯EG⋯RBB dimers in the crystal.