9-(2-Ethylphenoxycarbonyl)-10-methylacridinium trifluoromethanesulfonate

In the crystal structure of the title compound, C23H20NO2 +·CF3SO3 −, the cations form inversion dimers through π–π interactions between the acridine ring systems. These dimers are further linked by C—H⋯π interactions. The cations and anions are connected by C—H⋯O and C—F⋯π interactions. The acridine and benzene ring systems are oriented at a dihedral angle of 20.8 (1)°. The carboxyl group is twisted at an angle of 66.2 (1)° relative to the acridine skeleton. The mean planes of adjacent acridine units are parallel in the lattice.


D-HÁ
Cg1, Cg2 and Cg3 are the centroids of the C9/N10/C11-C14, C1-C4/C11/C12 and C5-C8/C13/C14 rings, respectively. CgIÁ Á ÁCgJ is the distance between ring centroids. The dihedral angle is that between the planes of the rings I and J. CgI_Perp is the perpendicular distance of CgI from ring J. CgI_Offset is the distance between CgI and perpendicular projection of CgJ on ring I. 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 (Sheldrick, 2008) and PLATON (Spek, 2009). Comment 9-(Phenoxycarbonyl)-10-alkylacridinium salts have long been known as chemiluminescent indicators or the chemiluminogenic fragments of chemiluminescent labels (Zomer & Jacquemijns, 2001). These compounds are commonly applied in assays of biologically and environmentally important entities such as antigens, antibodies, enzymes or DNA fragments (Roda et al., 2003;Brown et al., 2009). The reaction of the cations of these salts with hydrogen peroxide in alkaline media produces light. Our own investigations (Rak et al., 1999) and those of others (Zomer et al., 2001) have revealed that oxidation of acridinium chemiluminogens is accompanied by the removal of the phenoxycarbonyl fragment and the conversion of the remaining molecules to electronically excited, light-emitting 10-alkyl-9-acridinones. It has been found that the efficiency of chemiluminescence -crucial for analytical applications -is affected by the constitution of the phenyl fragment (Zomer & Jacquemijns, 2001). In the search for efficient chemiluminogens we undertook investigations on 9-(phenoxycarbonyl)-10methylacridinium derivatives substituted in the phenyl fragment. Here we present the structure of one such derivative.
In the cation of the title compound ( Fig. 1), the bond lengths and angles characterizing the geometry of the acridinium moiety are typical of acridine-based derivatives (Sikorski et al., 2005a,b). With respective average deviations from planarity of 0.022 (3) Å and 0.002 (3) Å, the acridine and benzene ring systems are oriented at 20.8 (1)°. The carboxyl group is twisted at an angle of 66.2 (1)° relative to the acridine skeleton. The mean planes of the adjacent acridine moieties are parallel (remain at an angle of 0.0 (1)°) in the lattice. The mutual arrangement of the carboxyl group relative to the acridine skeleton is similar in the compound investigated and its precursor -2-ethylphenyl acridine-9-carboxylate (Sikorski et al., 2005a).
On the other hand, the acridine and benzene ring systems are oriented quite differently in the compound investigated and its precursor.
In the crystal structure, the inversely oriented cations form dimers through multidirectional π-π interactions involving acridine moieties (Table 3, Fig. 2). These dimers are linked by C-H···O (Table 1 (Steiner, 1999;Bianchi et al. 2004). The C-H···π interactions should be of an attractive nature (Takahashi et al., 2001), like the C-F···π (Dorn et al., 2005) and the π-π (Hunter et al., 2001) interactions. The crystal structure is stabilized by a network of these short-range specific interactions and by long-range electrostatic interactions between ions.

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.