9-Phenyl-10H-acridinium trifluoromethanesulfonate

In the crystal structure of the title compound, C19H14N+·CF3SO3 −, the cations are linked to each other by very weak C—H⋯π interactions, while the cations and anions are connected by N—H⋯O, C—H⋯O and S—O⋯π interactions. The acridine ring system and the phenyl ring are oriented at an angle of 80.1 (1)° with respect to each other. The mean planes of adjacent acridine units are either parallel or inclined at an angle of 35.6 (1)°. The trifluoromethanesulfonate anions are disordered over two positions; the site occupancy factors are 0.591 (8) and 0.409 (8).

The compound whose crystal structure is reported here -9-phenyl-10H-acridinium trifluoromethanesulfonate -was obtained by the reaction of 9-phenylacridine with methyl trifluoromethanesulfonate, which usually leads to the quaternarization of the endocyclic N atom (Sato, 1996). Since protonation at the endocyclic N atom took place, we presume that traces of water caused the conversion of methyl trifluoromethanesulfonate to trifluoromethanesulfonic acid and methanol, and the reaction of the former entity with 9-phenylacridine. The cations of the title compound have a protonated endocyclic N atom, which enable their reaction with oxidants. It is worth mentioning that salts containing protonated 9-phenylacridines exhibit interesting chromoisomeric features and potential chemiluminogenic ability (Toma et al., 1994).
In the crystal structure, cations are linked by C-H···π interactions (Table 1 C-H···O (Novoa et al. 2006) interactions are of the hydrogen bond type. 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 S-O···π (Dorn et al., 2005) interactions. The crystal structure is stabilized by a network of these short-range specific interactions and by long-range electrostatic interactions between the ions.
Experimental 9-Phenylacridine was synthesized by heating a mixture of N-phenylaniline with an equimolar amount of benzoic acid, both dispersed in molten zinc chloride (493 K, 26 h) (Tsuge et al., 1965). The crude product was purified by gravitational chromatography (SiO 2 , n-hexane-ethyl acetate, 5:1 v/v). 9-Phenyl-10H-acridinium trifluoromethanesulfonate was obtained supplementary materials sup-2 by dissolving 9-phenylacridine and methyl trifluoromethanesulfonate (fivefold molar excess) in anhydrous dichloromethane and leaving the mixture for 3 h (Ar atmosphere, room temperature) (Zadykowicz et al., 2009b). The crude salt was dissolved in a small amount of ethanol, filtered, and precipitated with a 25 v/v excess of diethyl ether. Yellow crystals suitable for X-ray analysis were grown from absolute ethanol solution (m.p. 429-431 K).

Refinement
The H atom at N10 was refined freely with U iso (H) = 1.2U eq (N10). Other H atoms were positioned geometrically, with C-H = 0.93 Å and constrained to ride on their parent atoms with U iso (H) = 1.2U eq (C). The trifluoromethanesulfonate anions were found to be disordered. The structure was resolved on the assumption that the C25-S21 bond is a common one and that the SO 3 and CF 3 groups occupy two positions -A and B. The occupancy ratio was initially determined by isotropic refinement of the disordered site and the structure was refined freely during the subsequent anisotropic refinement of A. The disordered SO 3 and CF 3 groups were refined assuming two ideal triangles for A and B, respectively, with a restrained standard deviation of 0.001 Å for the O···O and F···F distances (SADI instruction in SHELXL97) (Müller et al., 2006).  [Symmetry codes: (i) -x + 1, -y + 2, -z + 1; (ii) -x + 3/2, y -1/2, -z + 1/2; (iii) -x + 1, -y + 1, -z + 1; (iv) -x + 2, -y + 1, -z + 1.]

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ.