9-Benzyl-10-methylacridinium trifluoromethanesulfonate

In the crystal structure of the title compound, C21H18N+·CF3OS3 −, 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, C—F⋯π and S—O⋯π interactions. The acridine and benzene ring systems are oriented at a dihedral angle of 76.8 (1)°with respect to each other. The acridine moieties are either parallel or inclined at an angle of 62.4 (1)° in the crystal structure.

Cg4 is the centroid of the C16-C21 ring.
Cg1 and Cg2 are the centroids of the C9/N10/C11-C14 and C1-C4/C11/C12 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. Symmetry code: (iii) -x + 2, -y + 1, -z + 1.
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 ( interactions with neighboring cations. The C-H···O interactions are of the hydrogen bond type (Bianchi et al., 2004;Novoa et al., 2006). The C-H···π interactions should be of an attractive nature (Takahashi et al., 2001), like the C-F···π (Dorn et al., 2005), S-O···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.
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., 2007;Trzybiński et al., 2010). With respective average deviations from planarity of 0.0427 (3) Å and 0.0066 (3) Å, the acridine and benzene ring systems are oriented at 76.8 (1)°.
The acridine moieties in pairs are parallel (remain at an angle of 0.0 (1)°), while in adjacent pairs they are inclined at an angle of 62.4 (1)°. The mutual arrangement of the acridine and benzene ring systems, as well as the acridine skeletons in the crystal lattice is similar in the compound investigated and its precursor -9-benzylacridine (Sikorski et al., 2007).
Experimental 9-Benzylacridine was prepared by treating N-phenylaniline with an equimolar amount of phenylacetic acid, both dispersed in molten zinc chloride (Huntress & Shaw, 1948;Sikorski et al., 2007). The crude product was purified chromatographically (SiO 2 , cyclohexane-ethyl acetate, 5:2 v/v). The compound thus obtained was quaternarized with a five-fold molar excess of methyltrifluoromethanesulfonate dissolved in anhydrous dichloromethane (Trzybiński et al., 2010). The crude 9-benzyl-10-methylacridinium trifluoromethanesulfonate was dissolved in a small amount of ethanol, filtered, and precipitated with a 25 v/v excess of diethyl ether. Light-orange crystals suitable for X-Ray investigations were grown from absolute ethanol solution (m.p. 478-480 K).

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.