organic compounds
(Z)-6-[(5-Chloro-2-hydroxyphenyl)aminomethylene]-2-ethoxycyclohexa-2,4-dienone
aDepartment of Physics, Ondokuz Mayıs University, TR-55139, Samsun, Turkey, and bFaculty of Education, Sinop University, Sinop, Turkey
*Correspondence e-mail: arzuozek@omu.edu.tr
The title compound, C15H14ClNO3, exists as the keto–amine form in the crystal and two intramolecular N—H⋯O hydrogen bonds are observed. The aromatic rings are oriented at a dihedral angle of 5.85 (8)°. In the intermolecular O—H⋯O and C—H⋯O hydrogen bonds link the molecules into chains. A π–π contact between the benzene rings [centroid–centroid distance = 3.6623 (10) Å] further stabilizes the structure.
Related literature
For general background, see: Büyükgüngör et al. (2007); Ersanlı et al. (2003); Tanak et al. (2008) For related structures, see: Özek et al. (2007, 2008).
Experimental
Crystal data
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Refinement
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Data collection: X-AREA (Stoe & Cie, 2002); cell X-AREA; data reduction: X-RED32 (Stoe & Cie, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).
Supporting information
10.1107/S1600536809031298/bt5027sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536809031298/bt5027Isup2.hkl
The compound (Z)-6-[(5-chloro-2-hydroxyphenylamino)methylene]-2- ethoxycyclohexa-2,4-dienone was prepared by reflux a mixture of a solution containing 3-ethoxy-2-hydroxybenzaldehyde (0.5 g 3 mmol) in 20 ml e thanol and a solution containing 5-chloro-2-hydroxyaniline (0.43 g 3 mmol) in 20 ml e thanol. The reaction mixture was stirred for 1 h under reflux. The crystals of (Z)-6-[(5-chloro-2-hydroxyphenylamino) methylene]-2-ethoxycyclohexa-2,4-dienone suitable for X-ray analysis were obtained from ethanol by slow evaporation (yield % 89; m.p. 489–491 K).
Data collection: X-AREA (Stoe & Cie, 2002); cell
X-AREA; data reduction: X-RED32 (Stoe & Cie, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).C15H14ClNO3 | F(000) = 608 |
Mr = 291.72 | Dx = 1.489 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ybc | Cell parameters from 15989 reflections |
a = 15.4313 (7) Å | θ = 2.8–26.5° |
b = 7.1710 (2) Å | µ = 0.30 mm−1 |
c = 12.6071 (6) Å | T = 296 K |
β = 111.168 (4)° | Prism, red |
V = 1300.94 (10) Å3 | 0.52 × 0.29 × 0.09 mm |
Z = 4 |
STOE IPDS II diffractometer | 2680 independent reflections |
Radiation source: fine-focus sealed tube | 2084 reflections with I > 2σ(I) |
Plane graphite monochromator | Rint = 0.060 |
Detector resolution: 6.67 pixels mm-1 | θmax = 26.5°, θmin = 2.8° |
ω scans | h = −19→19 |
Absorption correction: integration X-RED32 (Stoe & Cie, 2002) | k = −8→8 |
Tmin = 0.616, Tmax = 0.927 | l = −15→15 |
15989 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)] = 0.041 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.099 | All H-atom parameters refined |
S = 1.05 | w = 1/[σ2(Fo2) + (0.0546P)2 + 0.0402P] where P = (Fo2 + 2Fc2)/3 |
2680 reflections | (Δ/σ)max < 0.001 |
237 parameters | Δρmax = 0.15 e Å−3 |
0 restraints | Δρmin = −0.25 e Å−3 |
C15H14ClNO3 | V = 1300.94 (10) Å3 |
Mr = 291.72 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 15.4313 (7) Å | µ = 0.30 mm−1 |
b = 7.1710 (2) Å | T = 296 K |
c = 12.6071 (6) Å | 0.52 × 0.29 × 0.09 mm |
β = 111.168 (4)° |
STOE IPDS II diffractometer | 2680 independent reflections |
Absorption correction: integration X-RED32 (Stoe & Cie, 2002) | 2084 reflections with I > 2σ(I) |
Tmin = 0.616, Tmax = 0.927 | Rint = 0.060 |
15989 measured reflections |
R[F2 > 2σ(F2)] = 0.041 | 0 restraints |
wR(F2) = 0.099 | All H-atom parameters refined |
S = 1.05 | Δρmax = 0.15 e Å−3 |
2680 reflections | Δρmin = −0.25 e Å−3 |
237 parameters |
Experimental. 314 frames, detector distance = 100 mm |
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 | 0.42045 (11) | 0.1210 (2) | 0.12588 (13) | 0.0348 (3) | |
C2 | 0.35762 (11) | 0.0951 (2) | 0.18490 (13) | 0.0347 (3) | |
C3 | 0.25975 (11) | 0.0968 (2) | 0.11617 (14) | 0.0354 (4) | |
C4 | 0.23136 (12) | 0.1153 (2) | 0.00038 (14) | 0.0405 (4) | |
C5 | 0.29497 (13) | 0.1391 (3) | −0.05529 (15) | 0.0420 (4) | |
C6 | 0.38735 (12) | 0.1431 (2) | 0.00582 (14) | 0.0397 (4) | |
C7 | 0.10537 (12) | 0.1023 (3) | 0.11398 (16) | 0.0429 (4) | |
C8 | 0.05590 (13) | 0.1030 (4) | 0.19698 (19) | 0.0515 (5) | |
C9 | 0.51704 (11) | 0.1302 (2) | 0.18651 (15) | 0.0372 (4) | |
C10 | 0.65028 (11) | 0.1159 (2) | 0.36438 (14) | 0.0349 (3) | |
C11 | 0.67292 (11) | 0.1056 (2) | 0.48215 (14) | 0.0366 (4) | |
C12 | 0.76552 (12) | 0.0967 (3) | 0.55291 (16) | 0.0435 (4) | |
C13 | 0.83466 (12) | 0.0983 (3) | 0.50765 (16) | 0.0446 (4) | |
C14 | 0.81081 (11) | 0.1101 (2) | 0.39143 (16) | 0.0398 (4) | |
C15 | 0.71950 (12) | 0.1205 (2) | 0.31875 (15) | 0.0385 (4) | |
N1 | 0.55488 (9) | 0.1157 (2) | 0.29736 (12) | 0.0375 (3) | |
O1 | 0.38649 (8) | 0.07391 (19) | 0.29284 (10) | 0.0458 (3) | |
O2 | 0.20269 (8) | 0.08261 (18) | 0.17686 (10) | 0.0432 (3) | |
O3 | 0.60157 (9) | 0.10408 (19) | 0.52038 (11) | 0.0462 (3) | |
Cl1 | 0.89826 (3) | 0.10870 (7) | 0.33413 (5) | 0.05476 (17) | |
H1 | 0.5154 (16) | 0.095 (3) | 0.3294 (19) | 0.057 (6)* | |
H3 | 0.6156 (16) | 0.048 (3) | 0.584 (2) | 0.058 (6)* | |
H4 | 0.1662 (17) | 0.112 (3) | −0.044 (2) | 0.067 (7)* | |
H5 | 0.2700 (13) | 0.157 (3) | −0.1342 (18) | 0.048 (5)* | |
H6 | 0.4309 (14) | 0.169 (3) | −0.0299 (16) | 0.047 (5)* | |
H7A | 0.0925 (14) | 0.221 (3) | 0.0713 (18) | 0.055 (6)* | |
H7B | 0.0851 (14) | −0.005 (3) | 0.0600 (18) | 0.049 (5)* | |
H8A | 0.0771 (17) | 0.197 (3) | 0.250 (2) | 0.067 (7)* | |
H8B | 0.0646 (15) | −0.015 (4) | 0.2363 (19) | 0.063 (6)* | |
H8C | −0.0076 (18) | 0.120 (3) | 0.157 (2) | 0.068 (7)* | |
H9 | 0.5538 (13) | 0.150 (2) | 0.1399 (16) | 0.041 (5)* | |
H12 | 0.7798 (15) | 0.087 (3) | 0.633 (2) | 0.055 (6)* | |
H13 | 0.8974 (15) | 0.090 (3) | 0.5585 (18) | 0.053 (6)* | |
H15 | 0.7051 (13) | 0.124 (3) | 0.2410 (18) | 0.046 (5)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0326 (8) | 0.0412 (8) | 0.0316 (8) | 0.0001 (7) | 0.0127 (6) | −0.0005 (7) |
C2 | 0.0332 (8) | 0.0416 (8) | 0.0302 (8) | 0.0009 (7) | 0.0124 (6) | 0.0021 (6) |
C3 | 0.0329 (8) | 0.0404 (8) | 0.0331 (8) | −0.0007 (7) | 0.0122 (6) | −0.0005 (7) |
C4 | 0.0356 (8) | 0.0490 (9) | 0.0333 (8) | 0.0003 (7) | 0.0081 (7) | −0.0003 (7) |
C5 | 0.0454 (10) | 0.0520 (11) | 0.0264 (8) | 0.0044 (8) | 0.0103 (7) | 0.0021 (7) |
C6 | 0.0425 (9) | 0.0470 (10) | 0.0344 (9) | 0.0034 (7) | 0.0197 (7) | 0.0042 (7) |
C7 | 0.0294 (8) | 0.0547 (11) | 0.0421 (9) | 0.0028 (8) | 0.0099 (7) | 0.0023 (9) |
C8 | 0.0334 (9) | 0.0712 (14) | 0.0510 (11) | 0.0059 (9) | 0.0167 (9) | 0.0038 (11) |
C9 | 0.0349 (8) | 0.0439 (9) | 0.0368 (8) | −0.0001 (7) | 0.0178 (7) | 0.0027 (7) |
C10 | 0.0298 (7) | 0.0389 (8) | 0.0367 (9) | −0.0004 (6) | 0.0129 (6) | 0.0021 (7) |
C11 | 0.0352 (8) | 0.0407 (8) | 0.0373 (8) | 0.0004 (7) | 0.0172 (7) | 0.0021 (7) |
C12 | 0.0382 (9) | 0.0533 (10) | 0.0365 (9) | 0.0016 (8) | 0.0102 (7) | 0.0024 (8) |
C13 | 0.0312 (8) | 0.0510 (10) | 0.0475 (10) | 0.0006 (7) | 0.0091 (7) | 0.0016 (8) |
C14 | 0.0313 (8) | 0.0409 (9) | 0.0511 (10) | −0.0009 (7) | 0.0197 (7) | 0.0017 (8) |
C15 | 0.0361 (8) | 0.0447 (9) | 0.0383 (9) | 0.0008 (7) | 0.0178 (7) | 0.0007 (7) |
N1 | 0.0295 (7) | 0.0513 (8) | 0.0334 (7) | −0.0013 (6) | 0.0136 (6) | 0.0017 (6) |
O1 | 0.0332 (6) | 0.0767 (9) | 0.0287 (6) | −0.0018 (6) | 0.0125 (5) | 0.0055 (6) |
O2 | 0.0277 (6) | 0.0683 (8) | 0.0333 (6) | −0.0003 (5) | 0.0107 (5) | 0.0035 (5) |
O3 | 0.0403 (7) | 0.0646 (8) | 0.0403 (7) | 0.0069 (6) | 0.0225 (6) | 0.0103 (6) |
Cl1 | 0.0386 (2) | 0.0643 (3) | 0.0721 (3) | 0.0028 (2) | 0.0328 (2) | 0.0067 (2) |
C1—C9 | 1.410 (2) | C8—H8C | 0.93 (3) |
C1—C6 | 1.421 (2) | C9—N1 | 1.310 (2) |
C1—C2 | 1.432 (2) | C9—H9 | 0.96 (2) |
C2—O1 | 1.279 (2) | C10—C15 | 1.384 (2) |
C2—C3 | 1.445 (2) | C10—C11 | 1.399 (2) |
C3—O2 | 1.363 (2) | C10—N1 | 1.408 (2) |
C3—C4 | 1.371 (2) | C11—O3 | 1.3519 (19) |
C4—C5 | 1.408 (3) | C11—C12 | 1.386 (2) |
C4—H4 | 0.96 (2) | C12—C13 | 1.380 (3) |
C5—C6 | 1.354 (2) | C12—H12 | 0.95 (2) |
C5—H5 | 0.94 (2) | C13—C14 | 1.378 (3) |
C6—H6 | 0.95 (2) | C13—H13 | 0.95 (2) |
C7—O2 | 1.430 (2) | C14—C15 | 1.378 (2) |
C7—C8 | 1.502 (3) | C14—Cl1 | 1.7456 (17) |
C7—H7A | 0.99 (2) | C15—H15 | 0.92 (2) |
C7—H7B | 1.00 (2) | N1—H1 | 0.86 (2) |
C8—H8A | 0.92 (2) | O3—H3 | 0.85 (2) |
C8—H8B | 0.97 (2) | ||
C9—C1—C6 | 118.39 (15) | H8A—C8—H8C | 109 (2) |
C9—C1—C2 | 120.41 (15) | H8B—C8—H8C | 108.4 (19) |
C6—C1—C2 | 121.18 (14) | N1—C9—C1 | 123.47 (15) |
O1—C2—C1 | 121.83 (14) | N1—C9—H9 | 121.9 (11) |
O1—C2—C3 | 121.77 (14) | C1—C9—H9 | 114.6 (11) |
C1—C2—C3 | 116.40 (14) | C15—C10—C11 | 120.52 (15) |
O2—C3—C4 | 125.61 (15) | C15—C10—N1 | 123.16 (15) |
O2—C3—C2 | 114.20 (14) | C11—C10—N1 | 116.29 (14) |
C4—C3—C2 | 120.18 (15) | O3—C11—C12 | 123.59 (16) |
C3—C4—C5 | 122.02 (16) | O3—C11—C10 | 117.09 (15) |
C3—C4—H4 | 118.9 (14) | C12—C11—C10 | 119.32 (15) |
C5—C4—H4 | 119.0 (14) | C13—C12—C11 | 120.32 (17) |
C6—C5—C4 | 119.94 (16) | C13—C12—H12 | 121.3 (13) |
C6—C5—H5 | 123.1 (12) | C11—C12—H12 | 118.4 (13) |
C4—C5—H5 | 116.9 (12) | C14—C13—C12 | 119.38 (16) |
C5—C6—C1 | 120.23 (16) | C14—C13—H13 | 122.5 (13) |
C5—C6—H6 | 120.8 (12) | C12—C13—H13 | 118.1 (13) |
C1—C6—H6 | 118.8 (12) | C15—C14—C13 | 121.78 (16) |
O2—C7—C8 | 108.09 (15) | C15—C14—Cl1 | 118.87 (14) |
O2—C7—H7A | 110.6 (12) | C13—C14—Cl1 | 119.34 (13) |
C8—C7—H7A | 108.8 (12) | C14—C15—C10 | 118.66 (16) |
O2—C7—H7B | 108.1 (12) | C14—C15—H15 | 120.2 (12) |
C8—C7—H7B | 111.4 (12) | C10—C15—H15 | 121.0 (12) |
H7A—C7—H7B | 109.8 (17) | C9—N1—C10 | 127.35 (15) |
C7—C8—H8A | 111.7 (15) | C9—N1—H1 | 113.4 (15) |
C7—C8—H8B | 110.1 (14) | C10—N1—H1 | 119.0 (15) |
H8A—C8—H8B | 109 (2) | C3—O2—C7 | 116.33 (13) |
C7—C8—H8C | 109.0 (15) | C11—O3—H3 | 112.0 (16) |
C9—C1—C2—O1 | −2.2 (3) | C15—C10—C11—C12 | −1.1 (3) |
C6—C1—C2—O1 | 179.60 (16) | N1—C10—C11—C12 | 177.13 (16) |
C9—C1—C2—C3 | 176.96 (15) | O3—C11—C12—C13 | 179.80 (17) |
C6—C1—C2—C3 | −1.3 (2) | C10—C11—C12—C13 | 0.1 (3) |
O1—C2—C3—O2 | 2.8 (2) | C11—C12—C13—C14 | 0.5 (3) |
C1—C2—C3—O2 | −176.34 (14) | C12—C13—C14—C15 | 0.0 (3) |
O1—C2—C3—C4 | −178.42 (16) | C12—C13—C14—Cl1 | −179.07 (14) |
C1—C2—C3—C4 | 2.5 (2) | C13—C14—C15—C10 | −1.0 (3) |
O2—C3—C4—C5 | 176.54 (16) | Cl1—C14—C15—C10 | 178.08 (13) |
C2—C3—C4—C5 | −2.1 (3) | C11—C10—C15—C14 | 1.5 (3) |
C3—C4—C5—C6 | 0.4 (3) | N1—C10—C15—C14 | −176.58 (16) |
C4—C5—C6—C1 | 0.8 (3) | C1—C9—N1—C10 | 177.28 (17) |
C9—C1—C6—C5 | −178.59 (17) | C15—C10—N1—C9 | −4.2 (3) |
C2—C1—C6—C5 | −0.3 (3) | C11—C10—N1—C9 | 177.63 (17) |
C6—C1—C9—N1 | 178.49 (16) | C4—C3—O2—C7 | −4.7 (2) |
C2—C1—C9—N1 | 0.2 (3) | C2—C3—O2—C7 | 174.00 (15) |
C15—C10—C11—O3 | 179.17 (15) | C8—C7—O2—C3 | −174.00 (16) |
N1—C10—C11—O3 | −2.6 (2) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···O1 | 0.86 (2) | 1.88 (2) | 2.5957 (17) | 140 (2) |
N1—H1···O3 | 0.86 (2) | 2.29 (2) | 2.640 (2) | 104.3 (17) |
O3—H3···O1i | 0.85 (2) | 1.79 (2) | 2.6258 (17) | 165 (2) |
C9—H9···O3ii | 0.96 (2) | 2.594 (19) | 3.419 (2) | 143.8 (14) |
Symmetry codes: (i) −x+1, −y, −z+1; (ii) x, −y+1/2, z−1/2. |
Experimental details
Crystal data | |
Chemical formula | C15H14ClNO3 |
Mr | 291.72 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 296 |
a, b, c (Å) | 15.4313 (7), 7.1710 (2), 12.6071 (6) |
β (°) | 111.168 (4) |
V (Å3) | 1300.94 (10) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.30 |
Crystal size (mm) | 0.52 × 0.29 × 0.09 |
Data collection | |
Diffractometer | STOE IPDS II diffractometer |
Absorption correction | Integration X-RED32 (Stoe & Cie, 2002) |
Tmin, Tmax | 0.616, 0.927 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 15989, 2680, 2084 |
Rint | 0.060 |
(sin θ/λ)max (Å−1) | 0.628 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.041, 0.099, 1.05 |
No. of reflections | 2680 |
No. of parameters | 237 |
H-atom treatment | All H-atom parameters refined |
Δρmax, Δρmin (e Å−3) | 0.15, −0.25 |
Computer programs: X-AREA (Stoe & Cie, 2002), X-AREA, X-RED32 (Stoe & Cie, 2002), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 for Windows (Farrugia, 1997), WinGX (Farrugia, 1999).
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···O1 | 0.86 (2) | 1.88 (2) | 2.5957 (17) | 140 (2) |
N1—H1···O3 | 0.86 (2) | 2.29 (2) | 2.640 (2) | 104.3 (17) |
O3—H3···O1i | 0.85 (2) | 1.79 (2) | 2.6258 (17) | 165 (2) |
C9—H9···O3ii | 0.96 (2) | 2.594 (19) | 3.419 (2) | 143.8 (14) |
Symmetry codes: (i) −x+1, −y, −z+1; (ii) x, −y+1/2, z−1/2. |
Acknowledgements
The authors acknowledge the Faculty of Arts and Sciences, Ondokuz Mayıs University, Turkey, for the use of the Stoe IPDS II diffractometer (purchased under grant No. F.279 of the University Research Fund).
References
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As part of our ongoing studies on the syntheses and structural characterizations of Schiff-base compounds (Özek et al., 2008; Özek et al., 2007), we report here in the crystal structure of the title compound.
Schiff bases display two possible tautomeric forms, namely phenol-imine (O—H···N) and keto-amine (N—H···O) forms. o-Hydroxy Schiff bases have previously been observed in the keto form (Tanak et al., 2008) and in the enol form (Büyükgüngör et al., 2007).
The H atom in title compound (I) is located on atom N1, thus the keto-amine tautomer is favored over the phenol-imine form, as indicated by C2—O1 [1.279 (2) Å], C9—N1 [1.310 (2) Å], C1—C9 [1.410 (2) Å] and C1—C2 [1.432 (2) Å] bonds (Fig. 1). The O1—C2 bond length of 1.279 (2) Å indicates double-bond character, whereas the N1—C9 bond length of 1.310 (2) Å indicates a high degree of single-bond character. Similar results were observed for 2-[(2-Hydroxy- 4-nitrophenyl)-aminomethylene]cyclohexa-3,5-dien-1(2H)-οne [C—O = 1.298 (2) and C—N =1.308 (2) Å; Ersanlı et al., 2003].
It is known that Schiff bases may exhibit thermochromism or photochromism, depending on the planarity or non-planarity of the molecule, respectively. Therefore, one can expect thermochromic properties in the title compound caused by planarity of the molecule; the dihedral angle between rings A (C1—C6) and B (C10—C15) is 5.85 (8)°. Intramolecular N—H···O hydrogen bonds (Table 1) result in the formations of planar six- and five-membered rings C (O1/N1/C1/C2/C9/H1) and D (O3/N1/C10/C11/H1). They are oriented with respect to the adjacent rings at dihedral angles of A/C = 1.65 (9), A/D = 5.12 (9), B/C = 7.29 (7), B/D = 4.51 (5) and C/D = 5.61 (12) °. So, they are nearly coplanar.
In the crystal structure, molecules are linked into a three-dimensional network by intermolecular C—H···O and O—H···O hyrogen bonds (Table 1). The C—H···O hydrogen bonds generate C(6) chains along the c axis and O—H···O hydrogen bonds generate R22(18) ring motif (Fig. 2). The π···π contact between the phenyl rings, Cg1—Cg2i [symmetry code: (i) 1 - x, 1/2 + y, 1/2 - z, where Cg1 and Cg2 are centroids of the rings A (C1—C6) and B (C10—C15), respectively] may further stabilize the structure, with centroid-centroid distance of 3.6623 (10) Å.