ss-NMR and single-crystal X-ray diffraction in the elucidation of a new polymorph of bis­chalcone (1E,4E)-1,5-bis­(4-fluoro­phen­yl)penta-1,4-dien-3-one

We report a new polymorph of (1E,4E)-1,5-bis­(4-fluoro­phen­yl)penta-1,4-dien-3-one, C₁₇H₁₂F₂O. Contrary to the precedent literature polymorph with Z′ = 3, our polymorph has one half mol­ecule in the asymmetric unit disordered over two 50% occupancy sites. Each site corresponds to one conformation around the single bond vicinal to the carbonyl group (so-called anti or syn). The other half of the bis­chalcone is generated by twofold rotation symmetry, giving rise to two half-occupied and overlapping mol­ecules presenting both anti and syn conformations in their open chain. Such a disorder allows for distinct patterns of inter­molecular C—H...O contacts involving the carbonyl and anti-oriented β-C—H groups, which is reflected in three ¹³C NMR chemical shifts for the carbonyl C atom. Here, we have also assessed the cytotoxicity of three symmetric bis­chalcones through their in vitro anti­tumour potential against three cancer cell lines. Cytotoxicity assays revealed that this biological property increases as halogen electronegativity increases.

Computing details

Data collection: APEX2 (Bruker, 2003); cell refinement: SAINT (Bruker, 2003); data reduction: SAINT (Bruker, 2003); program(s) used to solve structure: SHELXS2014 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2018 (Sheldrick, 2015b); molecular graphics: WinGX (Farrugia, 1999); software used to prepare material for publication: publCIF (Westrip, 2010) and Mercury (Macrae et al., 2008).

(1E,4E)-1,5-Bis(4-fluorophenyl)penta-1,4-dien-3-one

Crystal data

C17H12F2O	F(000) = 560
Mr = 270.27	Dx = 1.322 Mg m^−3
Monoclinic, C2/c	Cu Kα radiation, λ = 1.54178 Å
a = 30.184 (3) Å	Cell parameters from 1008 reflections
b = 5.8907 (5) Å	θ = 8.7–66.1°
c = 7.7144 (6) Å	µ = 0.84 mm^−1
β = 98.040 (5)°	T = 296 K
V = 1358.18 (19) Å^3	Prism, yellow
Z = 4	0.15 × 0.10 × 0.10 mm

Data collection

Bruker APEXII CCD diffractometer	873 reflections with I > 2σ(I)
CCD scans	Rint = 0.040
Absorption correction: multi-scan (SADABS; Blessing, 1995)	θmax = 66.8°, θmin = 8.7°
Tmin = 0.744, Tmax = 0.920	h = −34→35
4490 measured reflections	k = −7→6
1148 independent reflections	l = −8→9

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.045	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.129	H-atom parameters constrained
S = 1.06	w = 1/[σ^2(Fo^2) + (0.0631P)^2 + 0.1789P] where P = (Fo^2 + 2Fc^2)/3
1148 reflections	(Δ/σ)max < 0.001
177 parameters	Δρmax = 0.14 e Å^−3
0 restraints	Δρmin = −0.13 e Å^−3

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 (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
C4A	0.6814 (8)	0.099 (4)	0.085 (2)	0.080 (4)	0.5
C5A	0.6399 (8)	0.014 (3)	0.044 (2)	0.078 (4)	0.5
H5A	0.635009	−0.130419	−0.004262	0.094*	0.5
C2A	0.6525 (8)	0.444 (3)	0.191 (3)	0.082 (3)	0.5
H2A	0.657795	0.590749	0.232641	0.098*	0.5
C6A	0.6024 (5)	0.1616 (17)	0.0799 (17)	0.067 (2)	0.5
H6A	0.572993	0.113930	0.049982	0.080*	0.5
C8B	0.5441 (2)	0.5655 (9)	0.2198 (5)	0.0741 (11)	0.5
H8B	0.566127	0.676994	0.225990	0.089*	0.5
C9	0.500000	0.6399 (4)	0.250000	0.0739 (6)
C1A	0.6118 (4)	0.3755 (14)	0.1597 (11)	0.068 (2)	0.5
C3A	0.6907 (6)	0.304 (3)	0.165 (2)	0.078 (3)	0.5
H3A	0.719934	0.351665	0.201368	0.094*	0.5
C7A	0.57605 (12)	0.5132 (6)	0.1977 (3)	0.0606 (7)	0.5
H7A	0.583197	0.665009	0.219610	0.073*	0.5
C7B	0.55635 (17)	0.3624 (6)	0.1855 (4)	0.0718 (8)	0.5
H7B	0.535252	0.247067	0.184062	0.086*	0.5
C8A	0.53286 (18)	0.4571 (11)	0.2071 (5)	0.0719 (10)	0.5
H8A	0.523243	0.308082	0.187627	0.086*	0.5
F1B	0.7249 (2)	0.0741 (8)	0.0571 (10)	0.1296 (17)	0.5
C2B	0.6426 (8)	0.427 (3)	0.207 (3)	0.101 (7)	0.5
H2B	0.640642	0.557907	0.272500	0.121*	0.5
F1A	0.7162 (2)	−0.0331 (7)	0.0539 (9)	0.1216 (16)	0.5
C3B	0.6810 (6)	0.362 (3)	0.170 (3)	0.091 (4)	0.5
H3B	0.706072	0.453802	0.196703	0.109*	0.5
C5B	0.6471 (8)	0.031 (3)	0.034 (2)	0.088 (6)	0.5
H5B	0.649620	−0.101089	−0.029744	0.105*	0.5
C1B	0.6027 (3)	0.2985 (14)	0.1472 (11)	0.0596 (16)	0.5
C6B	0.6088 (5)	0.093 (2)	0.0673 (17)	0.066 (2)	0.5
H6B	0.584355	−0.001676	0.037142	0.079*	0.5
C4B	0.6846 (7)	0.157 (4)	0.090 (2)	0.084 (5)	0.5
O1	0.5095 (2)	0.8393 (4)	0.2453 (17)	0.1042 (17)	0.5

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C4A	0.099 (8)	0.072 (7)	0.067 (4)	0.021 (5)	0.004 (4)	−0.009 (4)
C5A	0.096 (8)	0.054 (4)	0.081 (7)	0.001 (5)	−0.001 (5)	0.005 (4)
C2A	0.116 (8)	0.054 (4)	0.075 (7)	0.001 (5)	0.007 (5)	0.002 (4)
C6A	0.070 (4)	0.055 (7)	0.074 (4)	0.010 (4)	0.008 (3)	0.005 (4)
C8B	0.085 (4)	0.065 (3)	0.072 (2)	−0.010 (2)	0.0129 (18)	0.0033 (19)
C9	0.0732 (15)	0.0795 (14)	0.0696 (12)	0.000	0.0120 (9)	0.000
C1A	0.104 (6)	0.044 (4)	0.050 (2)	−0.008 (3)	−0.005 (2)	−0.004 (3)
C3A	0.072 (4)	0.080 (10)	0.080 (3)	−0.006 (5)	0.006 (3)	−0.002 (5)
C7A	0.070 (2)	0.0509 (17)	0.0624 (14)	−0.0034 (18)	0.0138 (13)	−0.0015 (11)
C7B	0.085 (3)	0.064 (2)	0.0647 (17)	−0.006 (2)	0.0035 (16)	0.0017 (14)
C8A	0.079 (3)	0.063 (3)	0.073 (2)	−0.011 (3)	0.0124 (17)	−0.0020 (19)
F1B	0.094 (3)	0.149 (4)	0.154 (3)	0.036 (3)	0.046 (2)	0.017 (4)
C2B	0.165 (17)	0.079 (8)	0.059 (4)	0.001 (8)	0.015 (7)	−0.008 (5)
F1A	0.114 (3)	0.122 (3)	0.127 (2)	0.038 (3)	0.0131 (19)	−0.015 (3)
C3B	0.105 (12)	0.064 (8)	0.099 (5)	−0.006 (6)	0.001 (6)	0.006 (5)
C5B	0.126 (13)	0.078 (9)	0.060 (4)	0.000 (6)	0.019 (5)	−0.006 (4)
C1B	0.077 (4)	0.046 (5)	0.056 (2)	0.007 (3)	0.010 (3)	−0.004 (3)
C6B	0.078 (6)	0.056 (6)	0.065 (2)	0.013 (4)	0.008 (2)	0.001 (4)
C4B	0.066 (4)	0.098 (14)	0.092 (7)	0.010 (6)	0.023 (5)	0.019 (7)
O1	0.105 (6)	0.0680 (12)	0.142 (2)	0.0007 (13)	0.026 (5)	−0.0001 (18)

Geometric parameters (Å, º)

C4A—C5A	1.35 (4)	C3A—H3A	0.9300
C4A—F1A	1.36 (2)	C7A—C8A	1.357 (7)
C4A—C3A	1.37 (3)	C7A—H7A	0.9300
C5A—C6A	1.48 (2)	C7B—C1B	1.518 (10)
C5A—H5A	0.9300	C7B—H7B	0.9300
C2A—C1A	1.28 (3)	C8A—H8A	0.9300
C2A—C3A	1.45 (2)	F1B—C4B	1.37 (2)
C2A—H2A	0.9300	C2B—C3B	1.29 (2)
C6A—C1A	1.414 (11)	C2B—C1B	1.44 (2)
C6A—H6A	0.9300	C2B—H2B	0.9300
C8B—C7B	1.291 (6)	C3B—C4B	1.36 (3)
C8B—C9	1.452 (5)	C3B—H3B	0.9300
C8B—H8B	0.9300	C5B—C6B	1.27 (3)
C9—O1	1.211 (3)	C5B—C4B	1.37 (3)
C9—O1^i	1.211 (3)	C5B—H5B	0.9300
C9—C8A	1.531 (6)	C1B—C6B	1.380 (9)
C9—C8A^i	1.531 (6)	C6B—H6B	0.9300
C1A—C7A	1.413 (11)	O1—O1^i	0.588 (10)
C5A—C4A—F1A	117.5 (19)	C2A—C3A—H3A	121.8
C5A—C4A—C3A	124 (2)	C8A—C7A—C1A	129.7 (6)
F1A—C4A—C3A	118 (2)	C8A—C7A—H7A	115.1
C4A—C5A—C6A	116.4 (18)	C1A—C7A—H7A	115.1
C4A—C5A—H5A	121.8	C8B—C7B—C1B	124.6 (6)
C6A—C5A—H5A	121.8	C8B—C7B—H7B	117.7
C1A—C2A—C3A	123.7 (17)	C1B—C7B—H7B	117.7
C1A—C2A—H2A	118.1	C7A—C8A—C9	119.8 (5)
C3A—C2A—H2A	118.1	C7A—C8A—H8A	120.1
C1A—C6A—C5A	119.6 (15)	C9—C8A—H8A	120.1
C1A—C6A—H6A	120.2	C3B—C2B—C1B	120.6 (18)
C5A—C6A—H6A	120.2	C3B—C2B—H2B	119.7
C7B—C8B—C9	127.4 (6)	C1B—C2B—H2B	119.7
C7B—C8B—H8B	116.3	C2B—C3B—C4B	119 (2)
C9—C8B—H8B	116.3	C2B—C3B—H3B	120.3
O1—C9—O1^i	28.1 (5)	C4B—C3B—H3B	120.3
O1—C9—C8B	93.5 (3)	C6B—C5B—C4B	120.9 (17)
O1^i—C9—C8B	121.6 (3)	C6B—C5B—H5B	119.6
O1—C9—C8B^i	121.6 (3)	C4B—C5B—H5B	119.6
O1^i—C9—C8B^i	93.5 (3)	C6B—C1B—C2B	116.4 (12)
O1—C9—C8A	120.8 (3)	C6B—C1B—C7B	119.2 (8)
O1^i—C9—C8A	148.4 (3)	C2B—C1B—C7B	124.0 (11)
O1—C9—C8A^i	148.4 (3)	C5B—C6B—C1B	121.6 (17)
O1^i—C9—C8A^i	120.8 (3)	C5B—C6B—H6B	119.2
C8A—C9—C8A^i	90.6 (4)	C1B—C6B—H6B	119.2
C2A—C1A—C7A	121.3 (12)	C3B—C4B—F1B	121.9 (18)
C2A—C1A—C6A	119.3 (13)	C3B—C4B—C5B	120.4 (18)
C7A—C1A—C6A	119.3 (10)	F1B—C4B—C5B	117.6 (19)
C4A—C3A—C2A	116.3 (19)	O1^i—O1—C9	76.0 (2)
C4A—C3A—H3A	121.8
F1A—C4A—C5A—C6A	180.0 (12)	O1^i—C9—C8A—C7A	20.9 (13)
C3A—C4A—C5A—C6A	4 (3)	C8A^i—C9—C8A—C7A	−163.9 (4)
C4A—C5A—C6A—C1A	−2 (2)	C1B—C2B—C3B—C4B	−7 (3)
C7B—C8B—C9—O1	−169.9 (7)	C3B—C2B—C1B—C6B	7 (2)
C7B—C8B—C9—O1^i	−168.5 (8)	C3B—C2B—C1B—C7B	179.7 (13)
C7B—C8B—C9—C8B^i	10.8 (3)	C8B—C7B—C1B—C6B	−162.7 (7)
C3A—C2A—C1A—C7A	175.8 (13)	C8B—C7B—C1B—C2B	24.7 (13)
C3A—C2A—C1A—C6A	−6 (2)	C4B—C5B—C6B—C1B	6 (2)
C5A—C6A—C1A—C2A	3.8 (18)	C2B—C1B—C6B—C5B	−6.2 (18)
C5A—C6A—C1A—C7A	−178.3 (10)	C7B—C1B—C6B—C5B	−179.4 (11)
C5A—C4A—C3A—C2A	−6 (3)	C2B—C3B—C4B—F1B	−176.3 (16)
F1A—C4A—C3A—C2A	177.9 (13)	C2B—C3B—C4B—C5B	7 (3)
C1A—C2A—C3A—C4A	7 (3)	C6B—C5B—C4B—C3B	−6 (3)
C2A—C1A—C7A—C8A	−165.4 (11)	C6B—C5B—C4B—F1B	176.9 (14)
C6A—C1A—C7A—C8A	16.8 (10)	C8B—C9—O1—O1^i	178 (3)
C9—C8B—C7B—C1B	177.1 (4)	C8B^i—C9—O1—O1^i	−3 (3)
C1A—C7A—C8A—C9	−179.6 (5)	C8A—C9—O1—O1^i	171 (2)
O1—C9—C8A—C7A	13.2 (8)	C8A^i—C9—O1—O1^i	−14 (4)

Symmetry code: (i) −x+1, y, −z+1/2.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C3A—H3A···F1A^ii	0.93	2.59	3.437 (17)	151
C3A—H3A···F1B^ii	0.93	2.66	3.477 (17)	146
C3B—H3B···F1A^ii	0.93	2.82	3.563 (19)	138
C3B—H3B···F1B^ii	0.93	2.71	3.519 (19)	146
C7B—H7B···O1^iii	0.93	2.84	3.745 (6)	163
C7B—H7B···O1^iv	0.93	2.59	3.448 (4)	154

Symmetry codes: (ii) −x+3/2, y+1/2, −z+1/2; (iii) −x+1, y−1, −z+1/2; (iv) x, y−1, z.