Crystal structure of 4-tert-butyl-2-{2-[N-(3,3-dimethyl-2-oxobutyl)-N-isopropylcarbamoyl]phenyl}-1-isopropyl-1H-imidazol-3-ium perchlorate

Bulky isopropyl substituents introduce steric hindrance within the molecule. The organic cation and perchlorate anion are linked by N—H⋯O hydrogen bonding. In the crystal, molecules form separated layers resulting in a low crystal density of 1.18 Mg m−1.

Crystal structure of 4-tert-butyl-2-{2-[N-(3,3dimethyl-2-oxobutyl)-N-isopropylcarbamoyl]-phenyl}-1-isopropyl-1H-imidazol-3-ium perchlorate Olga V. Hordiyenko a and Roman I. Zubatyuk b * a Taras Shevchenko National University of Kyiv, Department of Chemistry, 64/13 Volodymyrska str., Kyiv 01601, Ukraine, and b SSI Institute for Single Crystals NAS of Ukraine, 60 Lenin ave., Kharkiv 61001, Ukraine. *Correspondence e-mail: roman@xray.isc.kharkov.com In the title salt, C 26 H 40 N 3 O 2 + ÁClO 4 À , the positive charge of the organic cation is delocalized between the two N atoms of the imidazole ring. The C . . . N bond distances are 1.338 (2) and 1.327 (3) Å . The substituents on the benzene ring are rotated almost orthogonal with respect to this ring due to the presence of the bulky isopropyl substituents. The dihedral angle between the benzene and imidazole rings is 75.15 (12) . Three of the O atoms of the anion are disordered over two sets of sites due to rotation around one of the O-Cl bonds. The ratio of the refined occupancies is 0.591 (14): 0.409 (14). In the crystal, the cation and perchlorate anion are bound by an N-HÁ Á ÁO hydrogen bond. In addition, the cation-anion pairs are linked into layers parallel to (001) by multiple weak C-HÁ Á ÁO hydrogen bonds.
The organic cation and perchlorate anion are linked by an N-HÁ Á ÁO hydrogen bond (Table 1). The oxygen atoms of the anion are disordered over two sets of sites due to rotation around the O3-Cl bond. The refined occupancy of the major disordered component is 0.591 (14).

Supramolecular features
Several moderate to weak C-HÁ Á ÁO intermolecular hydrogen bonds are observed in the crystal structure (Table 1), which link molecules into layers parallel to (001) (Fig. 2). It should also be noted that the crystal structure contains no residual solvent-accessible voids. However, discernible layers along (101) are observed. The low density [1.18 g mm À1 ] of the crystal could be associated with formation of these layers.

Synthesis and crystallization
The title compound was synthesized according to the literature procedure (Hordiyenko et al., 2009). To a stirred solution of 1-(N-isopropylamino)-3,3-dimethylbutan-2-one (10 mmol) in dry CHCl 3 (10 mL), a solution of 1,1,3-trichloro-1H-isoindole (2.5 mmol) in dry CHCl 3 (10 mL) was added dropwise at room temperature under an argon atmosphere. The reaction mixture was stirred for 8 h, the solvent was evaporated and the residue was dried under reduced pressure (0.01 mm). Then it was treated with 100 ml of distilled water. The aqueous solution was brought to reflux with charcoal, filtered and treated with an excess of lithium perchlorate to precipitate the crude product that was then crystallized from methanol/water (3:1) to yield as colorless crystals. Single crystals suitable for X-ray diffraction were obtained by slow evaporation of a solution of the title compound in ethanol.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. Hydrogen atoms were placed in calculated positions (N-H = 0.86 Å , C-H = 0.93-0.98 Å ) and refined in a riding-model approximation with U iso = nU eq of the carrier atom (n = 1.5 for methyl groups, n = 1. View of the title compound showing the atom-numbering scheme and 30% probability displacement ellipsoids. For clarity, the ClO 4 À anion and H atoms are not shown.