9-(2,5-Dimethylphenoxycarbonyl)-10-methylacridinium trifluoromethanesulfonate

In the title compound, C23H20NO2 +·CF3SO3 −, the acridine ring system is oriented at a dihedral angle of 23.1 (1)° with respect to the benzene ring and the carboxyl group is twisted at an angle of 74.1 (1)° relative to the acridine skeleton. In the crystal, adjacent cations are linked through C—H⋯π interactions and neighboring cations and anions via weak C—H⋯O hydrogen bonds. The mean planes of adjacent acridine units are either parallel or inclined at angles of 15.0 (1), 26.9 (1) and 48.1 (1)° in the crystal structure.

In the title compound, C 23 H 20 NO 2 + ÁCF 3 SO 3 À , the acridine ring system is oriented at a dihedral angle of 23.1 (1) with respect to the benzene ring and the carboxyl group is twisted at an angle of 74.1 (1) relative to the acridine skeleton. In the crystal, adjacent cations are linked through C-HÁ Á Á interactions and neighboring cations and anions via weak C-HÁ Á ÁO hydrogen bonds. The mean planes of adjacent acridine units are either parallel or inclined at angles of 15.0 (1), 26.9 (1) and 48.1 (1) in the crystal structure.
Data collection: CrysAlis CCD (Oxford Diffraction, 2008); cell refinement: CrysAlis RED (Oxford Diffraction, 2008); data reduction: CrysAlis RED; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXL97 and PLATON (Spek, 2009   Chemiluminescing 9-(phenoxycarbonyl)-10-methylacridinium cations are widely applied as indicators or fragments of labels in assays of biologically and environmentally important entities such as antigens, antibodies, enzymes or DNA fragments (Roda et al., 2003;King et al., 2007;Brown et al., 2009). The cations of these salts are oxidized by H 2 O 2 in alkaline media, a reaction that is accompanied by the removal of the phenoxycarbonyl fragment and the conversion of the remaining part of the molecules to electronically excited, light-emitting 10-methyl-9-acridinone (Krzymiński et al., 2011). The efficiency of chemiluminescence -crucial to analytical applications -is affected by the constitution of the phenyl fragment.
In the cation of the title compound ( In the crystal structure, the adjacent cations are linked by C-H···π (Table 1 (Novoa et al. 2006), while the C-H···π (Takahashi et al., 2001) contacts should be of an attractive nature. The crystal structure is stabilized by a network of these specific short-range interactions and by long-range electrostatic interactions between ions.

Refinement
H atoms were positioned geometrically, with C-H = 0.93 Å and 0.96 Å for the aromatic and methyl H atoms, respectively, and constrained to ride on their parent atoms with U iso (H) = xU eq (C), where x = 1.2 for the aromatic and x = 1.5 for the methyl H atoms.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.