[3-(5-Hydroxy-5H-dibenzo[a,d]cyclohepten-5-yl)propyl]dimethylammonium 3-carboxyprop-2-enoate

In the cation of the title salt, C20H24NO+·C4H3O4 −, the N atom in the dimethylammonium group is protonated. The dihedral angle between the mean planes of the two six-membered rings fused to the cyclohepten-5-yl ring is 54.4 (1)°. An intramolecular O—H⋯O hydrogen bond occurs in the anion. The crystal packing is stabilized by intermolecular O—H⋯O and N—H⋯(O,O) hydrogen bonds and weak C—H⋯O interactions, forming a two-dimensional network.

MSS thanks UoM for research facilities. JPJ acknowledges the NSF-MRI program (grant No. CHE1039027) for funds to purchase the X-ray diffractometer.
In the cation of the title salt, C 20 H 24 NO + .C 4 H 3 O 4 -, the N atom in the dimethylammonium group is protonated (Fig 1).

Refinement
H1O and H1N were located by a Fourier map and refined isotropically. All of the remaining H atoms were placed in their calculated positions and then refined using the riding model with C-H lengths of 0.95 Å (CH), 0.99 Å (CH 2 ) or 0.98 Å (CH 3 ). The isotropic displacement parameters for these atoms were set to 1.19-1.21 (CH), 1.18-1.19 (CH 2 ) or 1.50-1.51 (CH 3 ) times U eq of the parent atom. In the absence of anomalous scatterers, 2834 Friedel pairs were merged. Fig. 1. Molecular structure of the title compound, showing the atom-labeling scheme and 30% probability displacement ellipsoids.

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 )
supplementary materials sup-9