Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536807050842/cv2319sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S1600536807050842/cv2319Isup2.hkl |
CCDC reference: 667389
(2E)-1-(2,4-Dichlorophenyl)-3-(2-methoxyphenyl)prop-2-en-1-one (3.07 g, 0.01 mol) was treated with bromine in acetic acid (30%) until the orange colour of the solution persisted. After stirring for half an hour, the content was poured on to crushed ice. The resulting solid mass was collected by filtration. The compound was dried and recrystallized from ethanol. Crystals suitable for structure determination were obtained from ethyl acetate by slow evaporation (yield 70%; m.p. 385–388 K). Analysis for C16H11Br3Cl2O2 found (calculated): C: 35.12 (35.20), H: 1.99% (2.03%).
The hydrogen atoms were placed in the idealized positions (C—H 0.93–0.98 Å) and refined using a riding model approximation, with Uiso(H)=1.2 or 1.3 Ueq(C).
For a structurally simple group of compounds, chalcones display an impressive array of biological activities, among which antimalarial (Liu et al., 2003), antiprotozoal (Nielsen et al., 1998), nitric oxide inhibition (Rojas et al., 2002) and anticancer activities have been reported in the literature. Among several organic compounds reported for non-linear optical (NLO) properties, chalcone derivatives are notable materials for their excellent blue light transmittance and good crystallizability (Indira et al., 2002; Sarojini et al., 2006). They provide a necessary configuration to show NLO properties, with two planar rings connected through a conjugated double bond. The substitution of a bromo group on either of the phenyl rings greatly influences the non-centrosymmetric crystal packing. The bromo group can obviously improve the molecular first-order hyperpolarizabilities and can effectively reduce dipole - dipole interactions between the molecules. Chalcone derivatives usually have a lower melting temperature, which can be a drawback when we use these crystals in optical instruments, but chalcone dibromides usually have higher melting points and are thermally stable. A new chalcone dibromide (1), C16H12Br2Cl2O2, was prepared by the bromination of the chalcone, (2E)-1-(2,4-Dichlorophenyl)-3-(2-methoxyphenyl)prop-2-en-1-one. During the bromination process the excess bromine reacted with the dibromide to form 2,3-dibromo-3-(5-bromo-2-methoxyphenyl)-1-(2,4-dichlorophenyl) propan-1-one (1). Due to the space group symmetry, the racemic mixture is present in the crystal structure.
The conformation of 1 (Fig. 1) can be described by the torsion angles between two approximately planar benzene rings with maximum deviations from mean planes of 0.009 (3) Å and 0.019 (3) Å for the rings C11 - C16 (A) and C31 - C36 (B), respectively, and the central C1—C2—C3 bridge (C). The values of these angles: A/B 39.54 (15)°, A/C 56.8 (3)°, and B/C 44.4 (3)° show that the rings are twisted in opposite sense with respect to the central bridge. The bromine Br2 and Br3 atoms are in mutual trans position, the torsion angle Br2—C2—C3—Br3 is 179.0 (2)°. The C—Br distances for C(sp3) and C(sp2) carbon atoms are significantly different: 2.007 (5) Å and 2.018 (5) Å for the former and 1.898 (5) Å for the latter.
In the crystal structure, besides the van der Waals forces (Fig. 2) there are also some C···C short contacts between neighbouring benzene rings: C14···C14(1 - x,-y,1 - z) of 3.429 (3) Å and C34···C36(-x,-y,-z) of 3.349 (3) Å. Only in the latter case, however, there is an overlap between the rings with the short distance of 3.753 (5) Å between their centroids, thus only in this case some π-π interaction is possible. Additionally, some directional weak C—H···Br interactions (Table 1) can be important. Short contact Cl12···Br2(x,1 + y,z) of 3.590 (5) Å is observed within the chains of molecules along [010] direction.
For related structures, see: Yathirajan et al. (2007a,b); Butcher et al. (2006a,b,c); Harrison et al. (2005). Various biological activities of chalcones were reported e.g. by Nielsen et al. (1998); Rojas et al. (2002) and Liu et al. (2003). For non-linear optical (NLO) properties of chalcone derivatives, see, for example, Indira et al. (2002) and Sarojini et al. (2006).
Data collection: CrysAlis CCD (Oxford Diffraction, 2006); cell refinement: CrysAlis RED (Oxford Diffraction, 2006); data reduction: CrysAlis RED (Oxford Diffraction, 2006); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP (Siemens, 1989); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997).
C16H11Br3Cl2O2 | F(000) = 1048 |
Mr = 545.88 | Dx = 2.015 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ybc | Cell parameters from 7661 reflections |
a = 15.9189 (8) Å | θ = 4–24° |
b = 7.3729 (3) Å | µ = 7.03 mm−1 |
c = 15.4895 (7) Å | T = 295 K |
β = 98.125 (4)° | Plate, colourless |
V = 1799.73 (14) Å3 | 0.4 × 0.2 × 0.1 mm |
Z = 4 |
Kuma KM-4-CCD four-circle diffractometer | 3104 independent reflections |
Radiation source: fine-focus sealed tube | 2223 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.034 |
Detector resolution: 8.1929 pixels mm-1 | θmax = 25.0°, θmin = 2.6° |
ω scans | h = −18→18 |
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2006) | k = −8→8 |
Tmin = 0.12, Tmax = 0.495 | l = −18→18 |
17972 measured reflections |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.037 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.099 | H-atom parameters constrained |
S = 1.20 | w = 1/[σ2(Fo2) + (0.05P)2] where P = (Fo2 + 2Fc2)/3 |
3104 reflections | (Δ/σ)max < 0.001 |
209 parameters | Δρmax = 0.70 e Å−3 |
0 restraints | Δρmin = −0.62 e Å−3 |
C16H11Br3Cl2O2 | V = 1799.73 (14) Å3 |
Mr = 545.88 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 15.9189 (8) Å | µ = 7.03 mm−1 |
b = 7.3729 (3) Å | T = 295 K |
c = 15.4895 (7) Å | 0.4 × 0.2 × 0.1 mm |
β = 98.125 (4)° |
Kuma KM-4-CCD four-circle diffractometer | 3104 independent reflections |
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2006) | 2223 reflections with I > 2σ(I) |
Tmin = 0.12, Tmax = 0.495 | Rint = 0.034 |
17972 measured reflections |
R[F2 > 2σ(F2)] = 0.037 | 0 restraints |
wR(F2) = 0.099 | H-atom parameters constrained |
S = 1.20 | Δρmax = 0.70 e Å−3 |
3104 reflections | Δρmin = −0.62 e Å−3 |
209 parameters |
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. |
x | y | z | Uiso*/Ueq | ||
C1 | 0.3657 (3) | 0.0862 (6) | 0.2091 (3) | 0.0477 (11) | |
O1 | 0.3990 (2) | 0.0840 (5) | 0.1434 (2) | 0.0666 (10) | |
C11 | 0.4172 (3) | 0.1263 (6) | 0.2947 (3) | 0.0414 (10) | |
C12 | 0.3936 (3) | 0.2306 (6) | 0.3619 (3) | 0.0432 (11) | |
Cl12 | 0.29453 (8) | 0.33676 (17) | 0.35285 (9) | 0.0624 (4) | |
C13 | 0.4480 (3) | 0.2662 (6) | 0.4375 (3) | 0.0492 (11) | |
H13 | 0.4311 | 0.3387 | 0.4811 | 0.059* | |
C14 | 0.5279 (3) | 0.1913 (6) | 0.4466 (3) | 0.0524 (12) | |
Cl14 | 0.59819 (10) | 0.2366 (2) | 0.54041 (10) | 0.0784 (5) | |
C15 | 0.5540 (3) | 0.0844 (7) | 0.3831 (3) | 0.0589 (13) | |
H15 | 0.6080 | 0.0335 | 0.3908 | 0.071* | |
C16 | 0.4987 (3) | 0.0538 (7) | 0.3077 (3) | 0.0547 (12) | |
H16 | 0.5164 | −0.0176 | 0.2642 | 0.066* | |
C2 | 0.2743 (3) | 0.0217 (6) | 0.2043 (3) | 0.0508 (12) | |
H2 | 0.2455 | 0.0871 | 0.2468 | 0.061* | |
Br2 | 0.28480 (3) | −0.24233 (7) | 0.23529 (4) | 0.06278 (19) | |
C3 | 0.2234 (3) | 0.0314 (7) | 0.1163 (3) | 0.0578 (13) | |
H3 | 0.2552 | −0.0256 | 0.0737 | 0.069* | |
Br3 | 0.21543 (4) | 0.30078 (7) | 0.09355 (4) | 0.0685 (2) | |
C31 | 0.1356 (3) | −0.0502 (6) | 0.1079 (3) | 0.0506 (12) | |
C32 | 0.0821 (3) | −0.0102 (6) | 0.1681 (3) | 0.0510 (12) | |
H32 | 0.1003 | 0.0653 | 0.2151 | 0.061* | |
C33 | 0.0011 (3) | −0.0831 (6) | 0.1581 (3) | 0.0520 (12) | |
Br33 | −0.07145 (3) | −0.03042 (8) | 0.24203 (4) | 0.0726 (2) | |
C34 | −0.0275 (3) | −0.1906 (6) | 0.0881 (4) | 0.0588 (13) | |
H34 | −0.0830 | −0.2333 | 0.0802 | 0.071* | |
C35 | 0.0263 (4) | −0.2350 (6) | 0.0297 (4) | 0.0634 (14) | |
H35 | 0.0078 | −0.3117 | −0.0168 | 0.076* | |
C36 | 0.1081 (3) | −0.1660 (6) | 0.0397 (3) | 0.0557 (13) | |
O36 | 0.1652 (3) | −0.2010 (6) | −0.0165 (2) | 0.0818 (12) | |
C361 | 0.1462 (4) | −0.3400 (8) | −0.0815 (4) | 0.086 (2) | |
H36A | 0.1380 | −0.4535 | −0.0535 | 0.112* | |
H36B | 0.1925 | −0.3508 | −0.1147 | 0.112* | |
H36C | 0.0954 | −0.3084 | −0.1196 | 0.112* |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.038 (3) | 0.060 (3) | 0.047 (3) | −0.005 (2) | 0.009 (2) | −0.005 (2) |
O1 | 0.046 (2) | 0.105 (3) | 0.049 (2) | −0.0172 (19) | 0.0083 (18) | −0.0083 (19) |
C11 | 0.034 (2) | 0.047 (2) | 0.043 (3) | −0.0069 (19) | 0.003 (2) | −0.001 (2) |
C12 | 0.035 (2) | 0.048 (2) | 0.044 (3) | −0.0035 (19) | −0.002 (2) | 0.008 (2) |
Cl12 | 0.0471 (7) | 0.0673 (8) | 0.0685 (9) | 0.0130 (6) | −0.0066 (6) | −0.0155 (6) |
C13 | 0.049 (3) | 0.049 (2) | 0.047 (3) | −0.004 (2) | −0.003 (2) | −0.002 (2) |
C14 | 0.041 (3) | 0.052 (3) | 0.057 (3) | −0.012 (2) | −0.016 (2) | 0.012 (2) |
Cl14 | 0.0676 (9) | 0.0796 (9) | 0.0751 (11) | −0.0176 (7) | −0.0345 (8) | 0.0084 (7) |
C15 | 0.028 (3) | 0.073 (3) | 0.072 (4) | 0.003 (2) | −0.004 (3) | 0.006 (3) |
C16 | 0.039 (3) | 0.069 (3) | 0.057 (3) | −0.003 (2) | 0.009 (3) | −0.005 (2) |
C2 | 0.039 (3) | 0.060 (3) | 0.051 (3) | −0.008 (2) | 0.001 (2) | −0.006 (2) |
Br2 | 0.0519 (3) | 0.0546 (3) | 0.0794 (4) | −0.0009 (2) | 0.0010 (3) | 0.0113 (2) |
C3 | 0.047 (3) | 0.064 (3) | 0.059 (3) | −0.015 (2) | −0.003 (3) | −0.012 (2) |
Br3 | 0.0631 (4) | 0.0594 (3) | 0.0772 (4) | −0.0182 (2) | −0.0099 (3) | 0.0201 (3) |
C31 | 0.041 (3) | 0.056 (3) | 0.052 (3) | −0.013 (2) | −0.006 (2) | −0.007 (2) |
C32 | 0.042 (3) | 0.055 (3) | 0.052 (3) | −0.011 (2) | −0.009 (2) | −0.004 (2) |
C33 | 0.042 (3) | 0.044 (2) | 0.066 (3) | −0.006 (2) | −0.006 (2) | 0.008 (2) |
Br33 | 0.0480 (3) | 0.0734 (4) | 0.0972 (5) | −0.0069 (3) | 0.0132 (3) | 0.0007 (3) |
C34 | 0.044 (3) | 0.051 (3) | 0.073 (4) | −0.013 (2) | −0.020 (3) | 0.008 (3) |
C35 | 0.067 (4) | 0.052 (3) | 0.061 (4) | −0.018 (3) | −0.024 (3) | 0.001 (2) |
C36 | 0.061 (3) | 0.054 (3) | 0.049 (3) | −0.010 (2) | −0.003 (3) | −0.007 (2) |
O36 | 0.086 (3) | 0.101 (3) | 0.058 (2) | −0.029 (2) | 0.008 (2) | −0.033 (2) |
C361 | 0.122 (6) | 0.071 (4) | 0.063 (4) | −0.017 (4) | 0.006 (4) | −0.017 (3) |
C1—O1 | 1.212 (5) | C3—Br3 | 2.018 (5) |
C1—C11 | 1.487 (6) | C3—H3 | 0.9800 |
C1—C2 | 1.523 (6) | C31—C36 | 1.381 (6) |
C11—C12 | 1.387 (6) | C31—C32 | 1.381 (6) |
C11—C16 | 1.391 (6) | C32—C33 | 1.385 (6) |
C12—C13 | 1.380 (6) | C32—H32 | 0.9300 |
C12—Cl12 | 1.749 (5) | C33—C34 | 1.368 (7) |
C13—C14 | 1.377 (7) | C33—Br33 | 1.898 (5) |
C13—H13 | 0.9300 | C34—C35 | 1.370 (8) |
C14—C15 | 1.369 (7) | C34—H34 | 0.9300 |
C14—Cl14 | 1.736 (5) | C35—C36 | 1.387 (7) |
C15—C16 | 1.379 (7) | C35—H35 | 0.9300 |
C15—H15 | 0.9300 | C36—O36 | 1.368 (6) |
C16—H16 | 0.9300 | O36—C361 | 1.438 (6) |
C2—C3 | 1.485 (7) | C361—H36A | 0.9600 |
C2—Br2 | 2.007 (5) | C361—H36B | 0.9600 |
C2—H2 | 0.9800 | C361—H36C | 0.9600 |
C3—C31 | 1.510 (6) | ||
O1—C1—C11 | 120.0 (4) | C31—C3—Br3 | 110.0 (3) |
O1—C1—C2 | 118.9 (4) | C2—C3—H3 | 109.3 |
C11—C1—C2 | 120.6 (4) | C31—C3—H3 | 109.3 |
C12—C11—C16 | 116.7 (4) | Br3—C3—H3 | 109.3 |
C12—C11—C1 | 127.2 (4) | C36—C31—C32 | 119.3 (4) |
C16—C11—C1 | 116.0 (4) | C36—C31—C3 | 120.1 (4) |
C13—C12—C11 | 122.6 (4) | C32—C31—C3 | 120.6 (4) |
C13—C12—Cl12 | 115.6 (3) | C31—C32—C33 | 119.6 (4) |
C11—C12—Cl12 | 121.7 (4) | C31—C32—H32 | 120.2 |
C14—C13—C12 | 118.0 (4) | C33—C32—H32 | 120.2 |
C14—C13—H13 | 121.0 | C34—C33—C32 | 120.9 (5) |
C12—C13—H13 | 121.0 | C34—C33—Br33 | 119.7 (4) |
C15—C14—C13 | 121.9 (4) | C32—C33—Br33 | 119.4 (4) |
C15—C14—Cl14 | 119.1 (4) | C33—C34—C35 | 119.5 (5) |
C13—C14—Cl14 | 119.0 (4) | C33—C34—H34 | 120.2 |
C14—C15—C16 | 118.7 (4) | C35—C34—H34 | 120.2 |
C14—C15—H15 | 120.7 | C34—C35—C36 | 120.2 (5) |
C16—C15—H15 | 120.7 | C34—C35—H35 | 119.9 |
C15—C16—C11 | 122.1 (4) | C36—C35—H35 | 119.9 |
C15—C16—H16 | 119.0 | O36—C36—C31 | 115.8 (4) |
C11—C16—H16 | 119.0 | O36—C36—C35 | 123.9 (5) |
C3—C2—C1 | 115.0 (4) | C31—C36—C35 | 120.3 (5) |
C3—C2—Br2 | 106.4 (3) | C36—O36—C361 | 119.1 (4) |
C1—C2—Br2 | 104.1 (3) | O36—C361—H36A | 109.5 |
C3—C2—H2 | 110.3 | O36—C361—H36B | 109.5 |
C1—C2—H2 | 110.3 | H36A—C361—H36B | 109.5 |
Br2—C2—H2 | 110.3 | O36—C361—H36C | 109.5 |
C2—C3—C31 | 115.9 (4) | H36A—C361—H36C | 109.5 |
C2—C3—Br3 | 102.7 (3) | H36B—C361—H36C | 109.5 |
O1—C1—C11—C12 | 140.4 (5) | Br2—C2—C3—C31 | 59.0 (5) |
C2—C1—C11—C12 | −48.3 (6) | C1—C2—C3—Br3 | −66.3 (4) |
O1—C1—C11—C16 | −38.1 (6) | Br2—C2—C3—Br3 | 178.98 (19) |
C2—C1—C11—C16 | 133.2 (4) | C2—C3—C31—C36 | −132.5 (5) |
C16—C11—C12—C13 | 1.6 (6) | Br3—C3—C31—C36 | 111.5 (4) |
C1—C11—C12—C13 | −177.0 (4) | C2—C3—C31—C32 | 47.4 (6) |
C16—C11—C12—Cl12 | 177.7 (3) | Br3—C3—C31—C32 | −68.5 (5) |
C1—C11—C12—Cl12 | −0.8 (6) | C36—C31—C32—C33 | −1.5 (7) |
C11—C12—C13—C14 | −1.4 (6) | C3—C31—C32—C33 | 178.5 (4) |
Cl12—C12—C13—C14 | −177.7 (3) | C31—C32—C33—C34 | −1.7 (7) |
C12—C13—C14—C15 | 0.0 (7) | C31—C32—C33—Br33 | 179.1 (3) |
C12—C13—C14—Cl14 | 179.1 (3) | C32—C33—C34—C35 | 3.7 (7) |
C13—C14—C15—C16 | 1.0 (7) | Br33—C33—C34—C35 | −177.1 (4) |
Cl14—C14—C15—C16 | −178.0 (4) | C33—C34—C35—C36 | −2.4 (7) |
C14—C15—C16—C11 | −0.7 (7) | C32—C31—C36—O36 | −179.1 (4) |
C12—C11—C16—C15 | −0.5 (7) | C3—C31—C36—O36 | 0.8 (7) |
C1—C11—C16—C15 | 178.2 (4) | C32—C31—C36—C35 | 2.8 (7) |
O1—C1—C2—C3 | −23.5 (6) | C3—C31—C36—C35 | −177.2 (5) |
C11—C1—C2—C3 | 165.1 (4) | C34—C35—C36—O36 | −178.8 (5) |
O1—C1—C2—Br2 | 92.6 (5) | C34—C35—C36—C31 | −0.9 (8) |
C11—C1—C2—Br2 | −78.8 (4) | C31—C36—O36—C361 | 171.0 (5) |
C1—C2—C3—C31 | 173.7 (4) | C35—C36—O36—C361 | −11.0 (8) |
D—H···A | D—H | H···A | D···A | D—H···A |
C32—H32···Br33i | 0.93 | 3.10 | 3.814 (5) | 135 |
C361—H36A···Br3ii | 0.96 | 3.03 | 3.839 (7) | 143 |
C361—H36B···Br2iii | 0.96 | 3.00 | 3.881 (6) | 153 |
Symmetry codes: (i) −x, y+1/2, −z+1/2; (ii) x, y−1, z; (iii) x, −y−1/2, z−1/2. |
Experimental details
Crystal data | |
Chemical formula | C16H11Br3Cl2O2 |
Mr | 545.88 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 295 |
a, b, c (Å) | 15.9189 (8), 7.3729 (3), 15.4895 (7) |
β (°) | 98.125 (4) |
V (Å3) | 1799.73 (14) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 7.03 |
Crystal size (mm) | 0.4 × 0.2 × 0.1 |
Data collection | |
Diffractometer | Kuma KM-4-CCD four-circle |
Absorption correction | Multi-scan (CrysAlis RED; Oxford Diffraction, 2006) |
Tmin, Tmax | 0.12, 0.495 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 17972, 3104, 2223 |
Rint | 0.034 |
(sin θ/λ)max (Å−1) | 0.594 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.037, 0.099, 1.20 |
No. of reflections | 3104 |
No. of parameters | 209 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.70, −0.62 |
Computer programs: CrysAlis CCD (Oxford Diffraction, 2006), CrysAlis RED (Oxford Diffraction, 2006), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), XP (Siemens, 1989).
D—H···A | D—H | H···A | D···A | D—H···A |
C32—H32···Br33i | 0.93 | 3.10 | 3.814 (5) | 135 |
C361—H36A···Br3ii | 0.96 | 3.03 | 3.839 (7) | 143 |
C361—H36B···Br2iii | 0.96 | 3.00 | 3.881 (6) | 153 |
Symmetry codes: (i) −x, y+1/2, −z+1/2; (ii) x, y−1, z; (iii) x, −y−1/2, z−1/2. |
For a structurally simple group of compounds, chalcones display an impressive array of biological activities, among which antimalarial (Liu et al., 2003), antiprotozoal (Nielsen et al., 1998), nitric oxide inhibition (Rojas et al., 2002) and anticancer activities have been reported in the literature. Among several organic compounds reported for non-linear optical (NLO) properties, chalcone derivatives are notable materials for their excellent blue light transmittance and good crystallizability (Indira et al., 2002; Sarojini et al., 2006). They provide a necessary configuration to show NLO properties, with two planar rings connected through a conjugated double bond. The substitution of a bromo group on either of the phenyl rings greatly influences the non-centrosymmetric crystal packing. The bromo group can obviously improve the molecular first-order hyperpolarizabilities and can effectively reduce dipole - dipole interactions between the molecules. Chalcone derivatives usually have a lower melting temperature, which can be a drawback when we use these crystals in optical instruments, but chalcone dibromides usually have higher melting points and are thermally stable. A new chalcone dibromide (1), C16H12Br2Cl2O2, was prepared by the bromination of the chalcone, (2E)-1-(2,4-Dichlorophenyl)-3-(2-methoxyphenyl)prop-2-en-1-one. During the bromination process the excess bromine reacted with the dibromide to form 2,3-dibromo-3-(5-bromo-2-methoxyphenyl)-1-(2,4-dichlorophenyl) propan-1-one (1). Due to the space group symmetry, the racemic mixture is present in the crystal structure.
The conformation of 1 (Fig. 1) can be described by the torsion angles between two approximately planar benzene rings with maximum deviations from mean planes of 0.009 (3) Å and 0.019 (3) Å for the rings C11 - C16 (A) and C31 - C36 (B), respectively, and the central C1—C2—C3 bridge (C). The values of these angles: A/B 39.54 (15)°, A/C 56.8 (3)°, and B/C 44.4 (3)° show that the rings are twisted in opposite sense with respect to the central bridge. The bromine Br2 and Br3 atoms are in mutual trans position, the torsion angle Br2—C2—C3—Br3 is 179.0 (2)°. The C—Br distances for C(sp3) and C(sp2) carbon atoms are significantly different: 2.007 (5) Å and 2.018 (5) Å for the former and 1.898 (5) Å for the latter.
In the crystal structure, besides the van der Waals forces (Fig. 2) there are also some C···C short contacts between neighbouring benzene rings: C14···C14(1 - x,-y,1 - z) of 3.429 (3) Å and C34···C36(-x,-y,-z) of 3.349 (3) Å. Only in the latter case, however, there is an overlap between the rings with the short distance of 3.753 (5) Å between their centroids, thus only in this case some π-π interaction is possible. Additionally, some directional weak C—H···Br interactions (Table 1) can be important. Short contact Cl12···Br2(x,1 + y,z) of 3.590 (5) Å is observed within the chains of molecules along [010] direction.