Comment

Among the various organic compounds reported for their non-linear optical (NLO) properties, chalcone derivatives are notable for their excellent blue-light transmittance and good crystallizability (Uchida et al., 1998). They provide a necessary molecular electronic configuration to show NLO effects, with two aromatic rings connected through a conjugated bridge (Goto et al., 1991; Tam et al., 1989; Indira et al., 2002). Substitution on either of the benzene rings appears to increase the likelihood of non-centrosymmetric crystal packing, as well as enhancing the electronic properties of the molecule (Fichou et al., 1988). As part of our ongoing studies in this area (Harrison et al., 2005; Harrison, Yathirajan, Sarojini, Narayana & Vijaya Raj, 2006), we have prepared the title chalcone derivative, (I) (Fig. 1).

The geometric parameters for (I) are normal. The dihedral angle between the C1-C6 and C10-C15 benzene rings is 7.15 (10)°. The C16 methyl C atom is displaced from the C10-C15 ring plane by 0.059 (4) Å. The enone group is close to planar (r.m.s. deviation from the mean plane of C6-C10 + O1 = 0.028 Å). Overall, the molecule of (I) is approximately planar, which is different from the significantly more twisted conformation of the 4-chloro derivative (Harrison, Yathirajan, Sarojini, Narayana & Indira, 2006), where the dihedral angle between the benzene rings is 21.82 (6)°.

The only possible non-van der Waals intermolecular interactions in (I) are C-HO and C-HF bonds arising from the methyl group (Table 2, Fig. 2). There are no - stacking interactions in (I).

Compound (I) complements other chalcone derivatives with different substituents X at the 4-fluoro position (see scheme), including X = Cl (Harrison, Yathirajan, Sarojini, Narayana & Indira, 2006), X = OH (Sathiya Moorthi et al., 2005), X = CH₃ (Wang et al., 2005), X = H (Rabinovich & Schmidt, 1970), X = OCH₃ (Zheng et al., 1992) and X = NO₂ (Patil et al., 2006). All of these compounds crystallize with different structures.

Figure 1 A view of (I). Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii.

Figure 2 The packing in (I), viewed down [100], with C-HO and C-HF interactions indicated by dashed lines.

Experimental

4-Fluoroacetophenone (1.38 g, 0.01 mol) in ethanol (25 ml) was mixed with 4-methoxy-benzaldehyde (1.36 g, 0.01 mol) in ethanol (25 ml) and the mixture was treated with an aqueous solution (20 ml) of potassium hydroxide (20 ml, 5%). The resulting mixture was stirred well and left for 24 h, and the solid product was collected by filtration and dried. Crystals of (I) were recrystallized from ethanol (yield 90%; m.p. 371 K). Analysis, found (calculated) for C₁₆H₁₃FO₂: C 74.29 (74.92%), H 5.72 (5.07%).

Crystal data

C16H13FO2 Mr = 256.26 Orthorhombic, P 21 21 21 a = 3.9148 (2) Å b = 10.1977 (5) Å c = 30.8052 (14) Å V = 1229.80 (10) Å3 Z = 4 Dx = 1.384 Mg m-3 Mo K radiation = 0.10 mm-1 T = 120 (2) K Block, colourless 0.65 × 0.20 × 0.15 mm

Data collection

Nonius KappaCCD area-detector diffractometer and scans Absorption correction: multi-scan SADABS (Bruker, 2003) Tmin = 0.938, Tmax = 0.985 8063 measured reflections 1669 independent reflections 1402 reflections with I > 2(I) Rint = 0.034 max = 27.5°

Refinement

Refinement on F2 R[F2 > 2(F2)] = 0.036 wR(F2) = 0.083 S = 1.09 1669 reflections 174 parameters H-atom parameters constrained w = 1/[2(Fo2) + (0.0274P)2 + 0.45P] where P = (Fo2 + 2Fc2)/3 (/)max < 0.001 max = 0.21 e Å-3 min = -0.17 e Å-3 Extinction correction: SHELXL97 (Sheldrick, 1997) Extinction coefficient: 0.017 (3)

Table 1 Selected torsion angles (°) C5-C6-C7-O1 -9.4 (3) O1-C7-C8-C9 -5.8 (4)

Table 2 Hydrogen-bond geometry (Å, °) D-HA D-H HA DA D-HA C16-H16BO1i 0.98 2.56 3.502 (3) 161 C16-H16AF1ii 0.98 2.59 3.458 (3) 148 Symmetry codes: (i) ; (ii) .

In the absence of significant anomalous scattering effects, Friedel pairs were averaged and the absolute structure of the crystal studied is indeterminate. The H atoms were placed in idealized locations (C-H = 0.95-0.98 Å) and refined as riding, with U_iso(H) = 1.2U_eq(C) or 1.5U_eq(methyl C). The methyl group was rotated to fit the electron density.

Data collection: COLLECT (Nonius, 1998); cell refinement: SCALEPACK (Otwinowski & Minor, 1997); data reduction: SCALEPACK, DENZO (Otwinowski & Minor, 1997), and SORTAV (Blessing, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXL97.