Two rhodamine derivatives: 9-[2-(ethoxycarbonyl)phenyl]-3,6-bis-(ethylamino)-2,7-dimethylxanthylium chloride monohydrate and 3,6-diamino-9-[2-(methoxycarbonyl)-phenyl]xanthylium chloride trihydrate.

The title compounds, C28H31N2O3(+)-Cl(-)-H2O (common name rhodamine-6g), (I), and C21H17N2O3(+)-Cl(-)-3H2O (common name rhodamine-123), (II), both have planar xanthene skeletons with a formal +1 charge on the amino N atoms delocalized through the pi-electron system so that the N-Csp(2) bond distances indicate significant double-bond character. The substituted planar phenyl groups make angles of 63.29 (8) and 87.96 (11) degrees with the xanthene planes in (I) and (II), respectively. In both molecules, the carbonyl bond vectors point toward the xanthene rings. The ethylamine groups in (I) are oriented similarly with their CH2-CH3 bond vectors pointing nearly perpendicular to the xanthene plane. The chloride ions and water molecules are disordered in both structures. In (I), the chloride ion and water molecule are disordered between two sites. One water and chloride alternately occupy the same site with occupancy factors of 0.5. The other 0.5-chloride and 0.5-water occupy two distinct positions separated by 0.747 (8) A. In (II), the chloride ion is disordered between three sites and one of the waters is disordered about two other sites. Both crystal structures are stabilized by hydrogen bonds involving the chloride ions, amino groups and water molecules, as well as by pi-pi stacking between xanthene planes.