(E)-1-(2-Aminophenyl)-3-(3,4,5-trimethoxyphenyl)prop-2-en-1-one

In the asymmetric unit of the title chalcone derivative, C18H19NO4, there are three crystallographically independent molecules (molecules A, B and C). In molecule A, the dihedral angle between two benzene rings is 12.22 (10)° and the plane of the central prop-2-en-1-one unit makes dihedral angles of 11.02 (13) and 2.64 (12)° with the two adjacent benzene rings. The corresponding angles in molecule B are 12.35 (10), 18.78 (12) and 7.29 (12)°, respectively, and those in molecule C are 15.40 (10), 15.62 (3) and 3.19 (13)°. In each molecule, an intramolecular N—H⋯O hydrogen bond generates an S(6) ring motif. In the crystal structure, the molecules B are linked by intermolecular N—H⋯O hydrogen bonds into a zigzag chain along the c axis, while the molecules A and C are linked together via an N—H⋯O hydrogen bond into a dimer. Adjacent dimers are further connected by N—H⋯N hydrogen bonds into a three-dimensional network. Weak C—H⋯O and C—H⋯π interactions are also observed.

However our experiment shows that (I) doesn't exhibit both antibacterial and tyrosinase inhibitory activities. Herein the crystal structure is reported.
There are three crystallographically independent molecules A, B and C in the asymmetric unit of (I) with differences in bond angles (Fig. 1). The molecular structure of (I), C 18 H 19 NO 4 is twisted with the the dihedral angle between the C1-C6 and C10-C15 benzene rings being 12.22 (10)° in molecule A whereas it is 12.35 (10) and 15.40 (10)° in molecules B and C, respectively. The central prop-2-en-1-one bridge (C7-C9/O1) in molecule A is planar whereas in molecules B and C it is slightly twisted which can be indicated by the torsion angle O1-C7-C8-C9 = 1.4 (3), 7.6 (3) and -3.4 (3)° in molecules  (Table 1) generates an S(6) ring motif (Bernstein et al., 1995). The bond distances agree with the literature values (Allen et al., 1987) and are comparable with the related structures (Fun et al., 2010;Suwunwong, Chantrapromma, Pakdeevanich & Fun, 2009).
In the crystal packing (Fig. 2), the molecules B are linked by intermolecular N-H···O hydrogen bonds (Table 1) into a zigzag chain along the c axis, while the molecules A and C are linked together via an N-H···O hydrogen bond into a dimer. Adjacent dimers are further connected by N-H···N hydrogen bonds (Table 1) into a three-dimensional network.
The crystal is stabilized by intermolecular N-H···O and N-H···N hydrogen bonds together weak C-H···O and C-H···π interactions (Table 1).
2-aminoacetophenone 0.31 ml (2.55 mmol) and 30% NaOH aqueous solution (5 ml) were then added. The mixture was stirred at room temperature for 2 hr. A yellow precipitate was formed and was then filtered, washed with distilled water and dried in vacuum. Yellow block-shaped single crystals of the title compound suitable for x-ray structure determination were recrystalized from ethanol by the slow evaporation of the solvent at room temperature after a week, Mp. 391-393 K.

Refinement
All H atoms were positioned geometrically and allowed to ride on their parent atoms, with d(N-H) = 0.84-0.93 Å, d(C-H) = 0.95 Å for aromatic and CH, and d(C-H) = 0.98 Å for CH 3 . The U iso values were constrained to be 1.5U eq of the carrier atom for methyl H atoms and 1.2U eq for the remaining H atoms. A rotating group model was used for the methyl groups.
The highest residual electron density peak is located at 0.84 Å from C5A and the deepest hole is located at 1.32 Å from C9C. Fig. 1. The molecular structure of the title compound, showing 50% probability displacement ellipsoids and the atom-numbering scheme. N-H···O hydrogen bonds are shown as dash lines.

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 120.0 (1) K.