organic compounds
4-Diethylamino-3,5-diisopropylbenzaldehyde
aUniversity Mainz, Duesbergweg 10-14, 55099 Mainz, Germany
*Correspondence e-mail: detert@uni-mainz.de
The title benzaldehyde, C17H27NO, was prepared via lithiation of bromoaniline and reaction with DMF. In the crystal, the molecule adopts a C2-symmetrical conformation; nevertheless, two modes of disorder are present: the orientation of the aldehyde group (occupancy ratio 0.5:0.5) and of symmetry-equivalent ethyl groups [occupancy ratio 0.595 (7):0.405 (7)]. The phenylene ring and the carbonyl group are essentially coplanar [C—C—C—O torsion angle = −179.0 (4)°] but the dihedral angle between the mean planes of the phenylene ring and the amino group = 67.5 (2)°. This and the long [1.414 (3) Å] aniline C—N bond indicate electronic decoupling between the carbonyl and amino groups. The angle sum of 359.9 (2)° around the N atom results from steric compression-induced rehybridization.
Related literature
The title compound was prepared as an intermediate in the synthesis of highly solvatochromic (Detert et al., 2002; Detert & Schmitt, 2006) or acidochromic fluorophores (Schmitt et al., 2008, 2011). For crystal structures of anilines with a p-accetor substituent, see: Fischer et al. (2011); Moschel et al. (2011). Acceptor-substituted anilines display dual fluorescence due to the formation of TICT (twisted intramolecular charge-transfer) states, see: Rotkiewicz et al. (1973); Okada et al. (1999). For the of 4-dimethylaminobenzaldehyde, see: Gao & Zhu (2008).
Experimental
Crystal data
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Data collection: CAD-4 Software (Enraf–Nonius, 1989); cell CAD-4 Software; data reduction: CORINC (Dräger & Gattow, 1971); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: PLATON.
Supporting information
https://doi.org/10.1107/S1600536811047672/bt5711sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536811047672/bt5711Isup2.hkl
Supporting information file. DOI: https://doi.org/10.1107/S1600536811047672/bt5711Isup3.cml
4-Bromo-N,N-diethyl-2,6-diisopropylaniline (0.76 g, 2.5 mmol) was dissolved in THF (15 ml) under nitrogen in a flame-dried Schlenk tube. The solution was cooled to195 K and n-BuLi (2.5 M in heptane, 1 ml) was added dropwise. After stirring for 1 h, dry DMF (0.2 ml, 2.5 mmol) was added carefully, stirring was continued for 15 min at 195 K, and the solution was allowed to reach room temperature. Aqueous NH4Cl (conc. 15 ml) was added and the mixture extracted with ethyl acetate (3 * 20 ml). The pooled organic solutions were dried (Na2SO4), concentrated in vacuo and the product was isolated via
(SiO2, petroleum ether / ethyl acetate = 15 / 1) Rf = 0.4 (petroleum ether / ethyl acetate = 9 / 1). The aldehyde was isolated as a yellowish oil that crystallized upon standing for several days. Yield: 0.23 g (35%)Hydrogen atoms attached to carbons were placed at calculated positions with C—H = 0.95 Å (aromatic) or 0.98–0.99 Å (sp3 C-atom). All H atoms were refined in the riding-model approximation with isotropic displacement parameters set at 1.2–1.5 times of the Ueq of the parent atom.
The aldehyde forms needle-shaped crystals of the monoclinic
C2/c.The compound crystallizes in parallel layers composed of geometrical dimers with C2 symmetry and z = 2. Two modes of disorder are present. A symmetry axis through C11—C4—C1—N4 results in a C2-symmetry of the molecule - but the carboxaldehyde group is disordered (50/50). The symmetry equivalent ethyl groups are also disordered but the s.o.f. is 60/40. The planes of the amino group and the benzene ring open an angle of 67.3 (3) ° whereas the carbonyl group and the aromatic system are essentially coplanar (torsion angle C3—C4—C11—O12: -179.0 (4) °). The sum of the bond angles around the nitrogen atom in both conformers is 359.9 (2) °, corresponding to a sp2 With 1.414 (3) Å, the aniline C—N bond is much longer than the corresponding bond (1.366 (2) Å) in the sterically undisturbed dimethylaminobenzaldehyde (Gao & Zhu, 2008). This may be in part due to steric congestion, but also due to inhibited conjugation. Correspondingly, the carbonyl bond length of 1.114 (4) Å in the title compound is shorter than in the dimethylamino derivative (1.204 (2) Å, 1.212 (3) Å) and with 1.470 (4) Å the aryl-carbonyl bond C4—C11 is longer than in the reference compound (1.457 (3) Å, 1.454 (2) Å).The title compound was prepared as an intermediate in the synthesis of highly solvatochromic (Detert et al., 2002; Detert & Schmitt, 2006) or acidochromic fluorophores (Schmitt et al., 2008, 2011). For crystal structures of anilines with a p-accetor substituent, see: Fischer et al. (2011); Moschel et al. (2011). Acceptor-substituted anilines display dual fluorescence due to the formation of TICT (twisted intramolecular charge-transfer) states, see: Rotkiewicz et al. (1973); Okada et al. (1999). For the
of 4-dimethylaminobenzaldehyd, see: Gao & Zhu (2008).Data collection: CAD-4 Software (Enraf–Nonius, 1989); cell
CAD-4 Software (Enraf–Nonius, 1989); data reduction: CORINC (Dräger & Gattow, 1971); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: PLATON (Spek, 2009).Fig. 1. View of compound I. Displacement ellipsoids are drawn at the 50% probability level. Only major conformer is shown. |
C17H27NO | F(000) = 576 |
Mr = 261.40 | Dx = 1.081 Mg m−3 |
Monoclinic, C2/c | Cu Kα radiation, λ = 1.54178 Å |
Hall symbol: -C 2yc | Cell parameters from 25 reflections |
a = 11.8061 (9) Å | θ = 60–70° |
b = 14.3419 (7) Å | µ = 0.50 mm−1 |
c = 10.7891 (8) Å | T = 173 K |
β = 118.478 (3)° | Needle, colourless |
V = 1605.78 (19) Å3 | 0.50 × 0.20 × 0.05 mm |
Z = 4 |
Enraf–Nonius CAD-4 diffractometer | Rint = 0.065 |
Radiation source: rotating anode | θmax = 70.0°, θmin = 5.3° |
Graphite monochromator | h = 0→14 |
ω/2θ scans | k = 0→17 |
1607 measured reflections | l = −13→11 |
1533 independent reflections | 60 standard reflections every 60 min |
1165 reflections with I > 2σ(I) | intensity decay: 3% |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.057 | H-atom parameters constrained |
wR(F2) = 0.186 | w = 1/[σ2(Fo2) + (0.1003P)2 + 0.8224P] where P = (Fo2 + 2Fc2)/3 |
S = 1.07 | (Δ/σ)max < 0.001 |
1533 reflections | Δρmax = 0.31 e Å−3 |
117 parameters | Δρmin = −0.23 e Å−3 |
0 restraints | Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0061 (10) |
C17H27NO | V = 1605.78 (19) Å3 |
Mr = 261.40 | Z = 4 |
Monoclinic, C2/c | Cu Kα radiation |
a = 11.8061 (9) Å | µ = 0.50 mm−1 |
b = 14.3419 (7) Å | T = 173 K |
c = 10.7891 (8) Å | 0.50 × 0.20 × 0.05 mm |
β = 118.478 (3)° |
Enraf–Nonius CAD-4 diffractometer | Rint = 0.065 |
1607 measured reflections | 60 standard reflections every 60 min |
1533 independent reflections | intensity decay: 3% |
1165 reflections with I > 2σ(I) |
R[F2 > 2σ(F2)] = 0.057 | 0 restraints |
wR(F2) = 0.186 | H-atom parameters constrained |
S = 1.07 | Δρmax = 0.31 e Å−3 |
1533 reflections | Δρmin = −0.23 e Å−3 |
117 parameters |
Experimental. 1H-NMR (400 MHz, CDCl3): 9.95 (s, 1 H, CHO), 6.61 (s, 2 H, 2-H, 6-H), 3.49 (sept, 3J = 6.9 Hz, 2 H, CH (i-Pr)), 3.11 (q, 3J = 7.1 Hz, 4 H, N-CH2), 1.22 (d, 3J = 6.9 Hz, 12 H, CH3 (iPr)), 1.04 (t, 3J = 7.1 Hz, 6 H, CH3 (Et)). 13C-NMR (75 MHz, CDCl3): 192.5 (CHO), 152.3 (C-4), 150.9 (C-3, C-5), 134.3 (C-1), 126.0 (C-2, C-6), 48.9 (N-CH2), 29.2 (CH (iPr), 24.5 (CH3 (iPr)), 15.2 (CH3 (Et)). IR (ATR) ν = 2963, 2928, 2869, 2723, 1696, 1594, 1568, 1457, 1365, 1268, 1170, 1104, 1065, 941, 892, 783, 724 cm-1. HR-ESI-MS: found 262.2177, calc. 262.2171 for (M+H+). |
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 | Occ. (<1) | |
C1 | 0.5000 | 0.29898 (16) | 0.2500 | 0.0301 (6) | |
C2 | 0.49043 (16) | 0.25001 (12) | 0.13197 (17) | 0.0329 (5) | |
C3 | 0.49237 (18) | 0.15335 (13) | 0.13533 (18) | 0.0407 (5) | |
H3 | 0.4884 | 0.1198 | 0.0574 | 0.049* | |
C4 | 0.5000 | 0.10460 (18) | 0.2500 | 0.0445 (7) | |
N5 | 0.5000 | 0.39757 (14) | 0.2500 | 0.0394 (6) | |
C6 | 0.3927 (4) | 0.4517 (2) | 0.2464 (5) | 0.0477 (12) | 0.595 (7) |
H6A | 0.4284 | 0.5063 | 0.3095 | 0.057* | 0.595 (7) |
H6B | 0.3471 | 0.4125 | 0.2841 | 0.057* | 0.595 (7) |
C7 | 0.2975 (5) | 0.4852 (3) | 0.1028 (5) | 0.0704 (16) | 0.595 (7) |
H7A | 0.3405 | 0.5274 | 0.0668 | 0.106* | 0.595 (7) |
H7B | 0.2275 | 0.5186 | 0.1082 | 0.106* | 0.595 (7) |
H7C | 0.2620 | 0.4318 | 0.0391 | 0.106* | 0.595 (7) |
C6A | 0.3813 (6) | 0.4420 (4) | 0.1519 (7) | 0.0511 (19) | 0.405 (7) |
H6C | 0.3242 | 0.3953 | 0.0827 | 0.061* | 0.405 (7) |
H6D | 0.3999 | 0.4910 | 0.0997 | 0.061* | 0.405 (7) |
C7A | 0.3127 (8) | 0.4849 (6) | 0.2250 (9) | 0.084 (3) | 0.405 (7) |
H7D | 0.2754 | 0.4355 | 0.2570 | 0.126* | 0.405 (7) |
H7E | 0.2439 | 0.5260 | 0.1593 | 0.126* | 0.405 (7) |
H7F | 0.3741 | 0.5212 | 0.3064 | 0.126* | 0.405 (7) |
C8 | 0.47720 (17) | 0.29910 (13) | 0.00066 (18) | 0.0384 (5) | |
H8 | 0.4765 | 0.3678 | 0.0159 | 0.046* | |
C9 | 0.5913 (2) | 0.27726 (19) | −0.0249 (2) | 0.0577 (7) | |
H9A | 0.6715 | 0.2966 | 0.0573 | 0.087* | |
H9B | 0.5812 | 0.3111 | −0.1085 | 0.087* | |
H9C | 0.5941 | 0.2101 | −0.0399 | 0.087* | |
C10 | 0.3504 (2) | 0.27324 (18) | −0.1286 (2) | 0.0535 (6) | |
H10A | 0.3516 | 0.2070 | −0.1502 | 0.080* | |
H10B | 0.3397 | 0.3108 | −0.2094 | 0.080* | |
H10C | 0.2786 | 0.2853 | −0.1093 | 0.080* | |
C11 | 0.5000 | 0.0021 (2) | 0.2500 | 0.0730 (11) | |
H11 | 0.4960 | −0.0251 | 0.1677 | 0.088* | 0.50 |
O12 | 0.5039 (6) | −0.0493 (2) | 0.3294 (5) | 0.1012 (16) | 0.50 |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0306 (11) | 0.0327 (12) | 0.0323 (12) | 0.000 | 0.0193 (9) | 0.000 |
C2 | 0.0347 (9) | 0.0379 (10) | 0.0326 (9) | 0.0009 (7) | 0.0213 (7) | 0.0008 (6) |
C3 | 0.0542 (11) | 0.0377 (10) | 0.0404 (10) | 0.0018 (8) | 0.0309 (9) | −0.0059 (7) |
C4 | 0.0589 (17) | 0.0334 (14) | 0.0487 (15) | 0.000 | 0.0317 (13) | 0.000 |
N5 | 0.0500 (13) | 0.0301 (11) | 0.0438 (12) | 0.000 | 0.0272 (10) | 0.000 |
C6 | 0.051 (2) | 0.0404 (19) | 0.046 (2) | 0.0115 (16) | 0.0187 (17) | −0.0043 (15) |
C7 | 0.062 (3) | 0.062 (3) | 0.073 (3) | 0.008 (2) | 0.020 (2) | 0.017 (2) |
C6A | 0.063 (4) | 0.037 (3) | 0.054 (4) | 0.012 (3) | 0.028 (3) | 0.008 (2) |
C7A | 0.068 (5) | 0.082 (5) | 0.092 (6) | 0.020 (4) | 0.031 (4) | −0.032 (4) |
C8 | 0.0425 (10) | 0.0476 (11) | 0.0311 (9) | −0.0020 (8) | 0.0225 (8) | 0.0020 (7) |
C9 | 0.0548 (13) | 0.0874 (17) | 0.0472 (12) | −0.0001 (11) | 0.0374 (10) | 0.0050 (11) |
C10 | 0.0519 (12) | 0.0748 (15) | 0.0329 (10) | −0.0049 (10) | 0.0194 (9) | 0.0035 (9) |
C11 | 0.112 (3) | 0.0387 (17) | 0.083 (3) | 0.000 | 0.059 (2) | 0.000 |
O12 | 0.195 (5) | 0.0416 (19) | 0.101 (3) | −0.003 (2) | 0.098 (3) | 0.0176 (19) |
C1—C2 | 1.411 (2) | C6A—C7A | 1.505 (10) |
C1—C2i | 1.411 (2) | C6A—H6C | 0.9900 |
C1—N5 | 1.414 (3) | C6A—H6D | 0.9900 |
C2—C3 | 1.387 (3) | C7A—H7D | 0.9800 |
C2—C8 | 1.522 (2) | C7A—H7E | 0.9800 |
C3—C4 | 1.386 (2) | C7A—H7F | 0.9800 |
C3—H3 | 0.9500 | C8—C10 | 1.527 (3) |
C4—C3i | 1.386 (2) | C8—C9 | 1.530 (3) |
C4—C11 | 1.470 (4) | C8—H8 | 1.0000 |
N5—C6Ai | 1.441 (6) | C9—H9A | 0.9800 |
N5—C6A | 1.441 (6) | C9—H9B | 0.9800 |
N5—C6i | 1.470 (4) | C9—H9C | 0.9800 |
N5—C6 | 1.470 (4) | C10—H10A | 0.9800 |
C6—C7 | 1.495 (6) | C10—H10B | 0.9800 |
C6—H6A | 0.9900 | C10—H10C | 0.9800 |
C6—H6B | 0.9900 | C11—O12i | 1.114 (4) |
C7—H7A | 0.9800 | C11—O12 | 1.114 (4) |
C7—H7B | 0.9800 | C11—H11 | 0.9500 |
C7—H7C | 0.9800 | ||
C2—C1—C2i | 120.3 (2) | C7A—C6A—H6D | 109.2 |
C2—C1—N5 | 119.86 (11) | H6C—C6A—H6D | 107.9 |
C2i—C1—N5 | 119.86 (11) | C6A—C7A—H7D | 109.5 |
C3—C2—C1 | 118.74 (16) | C6A—C7A—H7E | 109.5 |
C3—C2—C8 | 118.68 (15) | H7D—C7A—H7E | 109.5 |
C1—C2—C8 | 122.58 (17) | C6A—C7A—H7F | 109.5 |
C4—C3—C2 | 121.39 (17) | H7D—C7A—H7F | 109.5 |
C4—C3—H3 | 119.3 | H7E—C7A—H7F | 109.5 |
C2—C3—H3 | 119.3 | C2—C8—C10 | 111.02 (15) |
C3i—C4—C3 | 119.4 (2) | C2—C8—C9 | 111.38 (15) |
C3i—C4—C11 | 120.29 (12) | C10—C8—C9 | 110.43 (16) |
C3—C4—C11 | 120.29 (12) | C2—C8—H8 | 108.0 |
C1—N5—C6Ai | 116.2 (2) | C10—C8—H8 | 108.0 |
C1—N5—C6A | 116.2 (2) | C9—C8—H8 | 108.0 |
C6Ai—N5—C6A | 127.5 (5) | C8—C9—H9A | 109.5 |
C1—N5—C6i | 121.86 (16) | C8—C9—H9B | 109.5 |
C6A—N5—C6i | 108.1 (3) | H9A—C9—H9B | 109.5 |
C1—N5—C6 | 121.86 (16) | C8—C9—H9C | 109.5 |
C6Ai—N5—C6 | 108.1 (3) | H9A—C9—H9C | 109.5 |
C6i—N5—C6 | 116.3 (3) | H9B—C9—H9C | 109.5 |
N5—C6—C7 | 114.2 (4) | C8—C10—H10A | 109.5 |
N5—C6—H6A | 108.7 | C8—C10—H10B | 109.5 |
C7—C6—H6A | 108.7 | H10A—C10—H10B | 109.5 |
N5—C6—H6B | 108.7 | C8—C10—H10C | 109.5 |
C7—C6—H6B | 108.7 | H10A—C10—H10C | 109.5 |
H6A—C6—H6B | 107.6 | H10B—C10—H10C | 109.5 |
N5—C6A—C7A | 112.0 (6) | O12i—C11—C4 | 131.4 (3) |
N5—C6A—H6C | 109.2 | O12—C11—C4 | 131.4 (3) |
C7A—C6A—H6C | 109.2 | O12—C11—H11 | 114.3 |
N5—C6A—H6D | 109.2 | C4—C11—H11 | 114.3 |
C2i—C1—C2—C3 | −0.85 (12) | C1—N5—C6—C7 | −97.8 (3) |
N5—C1—C2—C3 | 179.15 (12) | C6Ai—N5—C6—C7 | 123.5 (4) |
C2i—C1—C2—C8 | 178.76 (17) | C6A—N5—C6—C7 | −4.4 (4) |
N5—C1—C2—C8 | −1.24 (17) | C6i—N5—C6—C7 | 82.2 (3) |
C1—C2—C3—C4 | 1.7 (2) | C1—N5—C6A—C7A | 107.0 (5) |
C8—C2—C3—C4 | −177.89 (13) | C6Ai—N5—C6A—C7A | −73.0 (5) |
C2—C3—C4—C3i | −0.89 (12) | C6i—N5—C6A—C7A | −111.7 (5) |
C2—C3—C4—C11 | 179.11 (12) | C6—N5—C6A—C7A | −2.0 (4) |
C2—C1—N5—C6Ai | −112.2 (3) | C3—C2—C8—C10 | 61.2 (2) |
C2i—C1—N5—C6Ai | 67.8 (3) | C1—C2—C8—C10 | −118.38 (18) |
C2—C1—N5—C6A | 67.8 (3) | C3—C2—C8—C9 | −62.3 (2) |
C2i—C1—N5—C6A | −112.2 (3) | C1—C2—C8—C9 | 118.10 (18) |
C2—C1—N5—C6i | −67.7 (2) | C3i—C4—C11—O12i | −179.0 (4) |
C2i—C1—N5—C6i | 112.3 (2) | C3—C4—C11—O12i | 1.0 (4) |
C2—C1—N5—C6 | 112.3 (2) | C3i—C4—C11—O12 | 1.0 (4) |
C2i—C1—N5—C6 | −67.7 (2) | C3—C4—C11—O12 | −179.0 (4) |
Symmetry code: (i) −x+1, y, −z+1/2. |
Experimental details
Crystal data | |
Chemical formula | C17H27NO |
Mr | 261.40 |
Crystal system, space group | Monoclinic, C2/c |
Temperature (K) | 173 |
a, b, c (Å) | 11.8061 (9), 14.3419 (7), 10.7891 (8) |
β (°) | 118.478 (3) |
V (Å3) | 1605.78 (19) |
Z | 4 |
Radiation type | Cu Kα |
µ (mm−1) | 0.50 |
Crystal size (mm) | 0.50 × 0.20 × 0.05 |
Data collection | |
Diffractometer | Enraf–Nonius CAD-4 |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 1607, 1533, 1165 |
Rint | 0.065 |
(sin θ/λ)max (Å−1) | 0.609 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.057, 0.186, 1.07 |
No. of reflections | 1533 |
No. of parameters | 117 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.31, −0.23 |
Computer programs: CAD-4 Software (Enraf–Nonius, 1989), CORINC (Dräger & Gattow, 1971), SIR97 (Altomare et al., 1999), SHELXL97 (Sheldrick, 2008), PLATON (Spek, 2009).
Acknowledgements
The authors are grateful to Heinz Kolshorn for the NMR spectra and invaluable discussions.
References
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The aldehyde forms needle-shaped crystals of the monoclinic space group C2/c.The compound crystallizes in parallel layers composed of geometrical dimers with C2 symmetry and z = 2. Two modes of disorder are present. A symmetry axis through C11—C4—C1—N4 results in a C2-symmetry of the molecule - but the carboxaldehyde group is disordered (50/50). The symmetry equivalent ethyl groups are also disordered but the s.o.f. is 60/40. The planes of the amino group and the benzene ring open an angle of 67.3 (3) ° whereas the carbonyl group and the aromatic system are essentially coplanar (torsion angle C3—C4—C11—O12: -179.0 (4) °). The sum of the bond angles around the nitrogen atom in both conformers is 359.9 (2) °, corresponding to a sp2 hybridization. With 1.414 (3) Å, the aniline C—N bond is much longer than the corresponding bond (1.366 (2) Å) in the sterically undisturbed dimethylaminobenzaldehyde (Gao & Zhu, 2008). This may be in part due to steric congestion, but also due to inhibited conjugation. Correspondingly, the carbonyl bond length of 1.114 (4) Å in the title compound is shorter than in the dimethylamino derivative (1.204 (2) Å, 1.212 (3) Å) and with 1.470 (4) Å the aryl-carbonyl bond C4—C11 is longer than in the reference compound (1.457 (3) Å, 1.454 (2) Å).