Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270106051511/av3047sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270106051511/av3047Isup2.hkl |
CCDC reference: 638313
2-Hydroxy-1-naphthaldehyde (0.172 g, 1 mmol) and 2-amino-4-tert-butylphenol (0.165 g, 1 mmol) were dissolved in ethanol (20 ml) and the solution was refluxed for 2 h. The resulting red product was recrystallized in methanol and dried in vacuum (yield 0.300 g, 85%; m.p. 513–515 K. Elemental analysis found (calculated) for C24H21NO2: C 78.99 (78.97), H 7.12 (6.63), N 4.37% (4.39%). The crystals were obtained from methanol at room temperature by slow evaporation for about a week. After a period of time, the crystals deteriorated into a red powder.
H atoms attached to N or O atoms were located in a difference Fourier synthesis and were refined freely. Other H atoms were positioned geometrically and were constrained to ride on their parent atoms [C—H = 0.93 Å (aromatic H) or 0.96 Å (methyl H); Uiso(H) = 1.2Ueq(C) or 1.5Ueq(C), respectively].
Data collection: XSCANS (Bruker, 1997); cell refinement: XSCANS; data reduction: SHELXTL (Bruker, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.
C21H21NO2 | Dx = 1.249 Mg m−3 |
Mr = 319.39 | Mo Kα radiation, λ = 0.71073 Å |
Orthorhombic, P212121 | Cell parameters from 3942 reflections |
a = 6.1882 (6) Å | θ = 2.4–25.4° |
b = 15.9350 (15) Å | µ = 0.08 mm−1 |
c = 17.2295 (16) Å | T = 294 K |
V = 1699.0 (3) Å3 | Block, red |
Z = 4 | 0.26 × 0.20 × 0.16 mm |
F(000) = 680 |
Bruker Model? CCD area-detector diffractometer | 2343 independent reflections |
Radiation source: fine-focus sealed tube | 2039 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.022 |
ϕ and ω scans | θmax = 27.9°, θmin = 1.7° |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | h = −8→8 |
Tmin = 0.975, Tmax = 0.987 | k = −15→20 |
11475 measured reflections | l = −22→22 |
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)] = 0.032 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.089 | w = 1/[σ2(Fo2) + (0.0487P)2 + 0.151P] where P = (Fo2 + 2Fc2)/3 |
S = 1.06 | (Δ/σ)max = 0.001 |
2343 reflections | Δρmax = 0.16 e Å−3 |
229 parameters | Δρmin = −0.13 e Å−3 |
0 restraints | Extinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0126 (17) |
C21H21NO2 | V = 1699.0 (3) Å3 |
Mr = 319.39 | Z = 4 |
Orthorhombic, P212121 | Mo Kα radiation |
a = 6.1882 (6) Å | µ = 0.08 mm−1 |
b = 15.9350 (15) Å | T = 294 K |
c = 17.2295 (16) Å | 0.26 × 0.20 × 0.16 mm |
Bruker Model? CCD area-detector diffractometer | 2343 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | 2039 reflections with I > 2σ(I) |
Tmin = 0.975, Tmax = 0.987 | Rint = 0.022 |
11475 measured reflections |
R[F2 > 2σ(F2)] = 0.032 | 0 restraints |
wR(F2) = 0.089 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.06 | Δρmax = 0.16 e Å−3 |
2343 reflections | Δρmin = −0.13 e Å−3 |
229 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. |
x | y | z | Uiso*/Ueq | ||
N1 | 0.8843 (2) | 0.55923 (9) | 0.95496 (8) | 0.0390 (3) | |
H1A | 0.924 (4) | 0.6138 (13) | 0.9501 (11) | 0.054 (6)* | |
O1 | 0.7245 (3) | 0.69112 (8) | 1.01802 (10) | 0.0690 (5) | |
H1 | 0.684 (4) | 0.7366 (17) | 1.0452 (13) | 0.086 (8)* | |
O2 | 1.1329 (2) | 0.67339 (7) | 0.90636 (8) | 0.0527 (3) | |
C1 | 0.6253 (3) | 0.61894 (10) | 1.03795 (10) | 0.0473 (4) | |
C2 | 0.7063 (3) | 0.54589 (10) | 1.00378 (9) | 0.0376 (3) | |
C3 | 0.6158 (3) | 0.46859 (10) | 1.01996 (9) | 0.0359 (3) | |
H3 | 0.6712 | 0.4209 | 0.9961 | 0.043* | |
C4 | 0.4432 (3) | 0.46071 (10) | 1.07125 (9) | 0.0376 (3) | |
C5 | 0.3636 (3) | 0.53476 (11) | 1.10418 (11) | 0.0503 (4) | |
H5 | 0.2482 | 0.5315 | 1.1386 | 0.060* | |
C6 | 0.4502 (4) | 0.61232 (12) | 1.08742 (12) | 0.0564 (5) | |
H6 | 0.3908 | 0.6603 | 1.1094 | 0.068* | |
C7 | 0.3538 (3) | 0.37519 (11) | 1.09540 (9) | 0.0400 (4) | |
C8 | 0.4345 (4) | 0.30409 (12) | 1.04407 (12) | 0.0598 (6) | |
H8A | 0.5890 | 0.3004 | 1.0479 | 0.090* | |
H8B | 0.3945 | 0.3149 | 0.9912 | 0.090* | |
H8C | 0.3711 | 0.2522 | 1.0608 | 0.090* | |
C9 | 0.4302 (4) | 0.35749 (14) | 1.17824 (11) | 0.0635 (6) | |
H9A | 0.5853 | 0.3566 | 1.1795 | 0.095* | |
H9B | 0.3754 | 0.3041 | 1.1949 | 0.095* | |
H9C | 0.3778 | 0.4006 | 1.2123 | 0.095* | |
C10 | 0.1065 (3) | 0.37501 (15) | 1.09408 (15) | 0.0635 (5) | |
H10A | 0.0542 | 0.3222 | 1.1133 | 0.095* | |
H10B | 0.0569 | 0.3831 | 1.0418 | 0.095* | |
H10C | 0.0532 | 0.4196 | 1.1263 | 0.095* | |
C11 | 1.0025 (3) | 0.50606 (10) | 0.91556 (8) | 0.0362 (3) | |
H11 | 0.9626 | 0.4498 | 0.9152 | 0.043* | |
C12 | 1.1871 (3) | 0.53059 (10) | 0.87386 (8) | 0.0346 (3) | |
C13 | 1.2522 (3) | 0.61661 (10) | 0.87657 (9) | 0.0391 (4) | |
C14 | 1.4599 (3) | 0.63822 (11) | 0.84536 (10) | 0.0461 (4) | |
H14 | 1.5106 | 0.6929 | 0.8507 | 0.055* | |
C15 | 1.5821 (3) | 0.58138 (12) | 0.80873 (10) | 0.0483 (4) | |
H15 | 1.7149 | 0.5980 | 0.7886 | 0.058* | |
C16 | 1.5159 (3) | 0.49614 (12) | 0.79942 (9) | 0.0426 (4) | |
C17 | 1.3171 (3) | 0.46998 (10) | 0.83199 (8) | 0.0368 (4) | |
C18 | 1.2565 (3) | 0.38556 (11) | 0.82062 (10) | 0.0486 (4) | |
H18 | 1.1266 | 0.3663 | 0.8411 | 0.058* | |
C19 | 1.3864 (4) | 0.33142 (13) | 0.77978 (12) | 0.0614 (6) | |
H19 | 1.3432 | 0.2760 | 0.7732 | 0.074* | |
C20 | 1.5807 (4) | 0.35780 (15) | 0.74814 (13) | 0.0653 (6) | |
H20 | 1.6672 | 0.3205 | 0.7206 | 0.078* | |
C21 | 1.6436 (4) | 0.43900 (14) | 0.75778 (11) | 0.0572 (5) | |
H21 | 1.7735 | 0.4569 | 0.7364 | 0.069* |
U11 | U22 | U33 | U12 | U13 | U23 | |
N1 | 0.0404 (7) | 0.0305 (7) | 0.0462 (7) | −0.0006 (6) | 0.0059 (6) | −0.0027 (6) |
O1 | 0.0846 (11) | 0.0324 (7) | 0.0899 (11) | −0.0023 (7) | 0.0361 (10) | −0.0123 (7) |
O2 | 0.0554 (7) | 0.0325 (6) | 0.0703 (8) | −0.0038 (6) | 0.0093 (7) | −0.0100 (6) |
C1 | 0.0566 (10) | 0.0333 (8) | 0.0520 (9) | 0.0039 (9) | 0.0098 (9) | −0.0046 (8) |
C2 | 0.0385 (8) | 0.0362 (8) | 0.0380 (7) | 0.0043 (7) | 0.0035 (7) | −0.0017 (7) |
C3 | 0.0342 (7) | 0.0345 (7) | 0.0390 (7) | 0.0057 (7) | 0.0010 (6) | −0.0050 (6) |
C4 | 0.0367 (8) | 0.0402 (8) | 0.0360 (7) | 0.0027 (7) | 0.0009 (6) | −0.0034 (7) |
C5 | 0.0496 (10) | 0.0501 (10) | 0.0511 (9) | 0.0061 (9) | 0.0166 (9) | −0.0059 (9) |
C6 | 0.0646 (12) | 0.0415 (9) | 0.0630 (11) | 0.0094 (9) | 0.0212 (10) | −0.0115 (9) |
C7 | 0.0343 (8) | 0.0455 (9) | 0.0400 (8) | −0.0014 (7) | 0.0026 (7) | −0.0015 (8) |
C8 | 0.0672 (14) | 0.0449 (10) | 0.0673 (12) | −0.0128 (10) | 0.0164 (11) | −0.0106 (9) |
C9 | 0.0734 (14) | 0.0649 (13) | 0.0523 (10) | −0.0078 (12) | −0.0129 (11) | 0.0098 (9) |
C10 | 0.0385 (9) | 0.0702 (13) | 0.0819 (14) | −0.0067 (10) | 0.0006 (10) | 0.0056 (13) |
C11 | 0.0406 (8) | 0.0301 (7) | 0.0377 (7) | 0.0006 (7) | 0.0008 (7) | −0.0016 (6) |
C12 | 0.0365 (8) | 0.0327 (8) | 0.0345 (7) | 0.0003 (7) | −0.0008 (6) | 0.0009 (6) |
C13 | 0.0439 (8) | 0.0354 (8) | 0.0380 (7) | −0.0033 (8) | −0.0016 (7) | −0.0002 (7) |
C14 | 0.0487 (10) | 0.0410 (9) | 0.0486 (9) | −0.0121 (8) | −0.0007 (8) | 0.0049 (7) |
C15 | 0.0402 (9) | 0.0572 (11) | 0.0474 (9) | −0.0081 (9) | 0.0056 (8) | 0.0073 (8) |
C16 | 0.0409 (9) | 0.0495 (10) | 0.0373 (7) | 0.0032 (8) | 0.0018 (7) | 0.0048 (7) |
C17 | 0.0403 (8) | 0.0364 (8) | 0.0337 (7) | 0.0033 (7) | 0.0016 (6) | 0.0026 (6) |
C18 | 0.0530 (10) | 0.0390 (9) | 0.0538 (10) | 0.0012 (9) | 0.0134 (9) | −0.0019 (8) |
C19 | 0.0740 (14) | 0.0393 (10) | 0.0710 (13) | 0.0087 (11) | 0.0170 (12) | −0.0073 (9) |
C20 | 0.0655 (13) | 0.0598 (13) | 0.0705 (13) | 0.0197 (11) | 0.0213 (12) | −0.0064 (11) |
C21 | 0.0484 (11) | 0.0655 (13) | 0.0578 (11) | 0.0082 (10) | 0.0146 (9) | 0.0006 (10) |
N1—C11 | 1.309 (2) | C9—H9C | 0.9600 |
N1—C2 | 1.402 (2) | C10—H10A | 0.9600 |
N1—H1A | 0.91 (2) | C10—H10B | 0.9600 |
O1—C1 | 1.348 (2) | C10—H10C | 0.9600 |
O1—H1 | 0.90 (3) | C11—C12 | 1.405 (2) |
O2—C13 | 1.275 (2) | C11—H11 | 0.9300 |
C1—C6 | 1.382 (3) | C12—C13 | 1.429 (2) |
C1—C2 | 1.397 (2) | C12—C17 | 1.449 (2) |
C2—C3 | 1.382 (2) | C13—C14 | 1.435 (2) |
C3—C4 | 1.392 (2) | C14—C15 | 1.338 (3) |
C3—H3 | 0.9300 | C14—H14 | 0.9300 |
C4—C5 | 1.399 (2) | C15—C16 | 1.428 (3) |
C4—C7 | 1.529 (2) | C15—H15 | 0.9300 |
C5—C6 | 1.378 (3) | C16—C21 | 1.403 (3) |
C5—H5 | 0.9300 | C16—C17 | 1.415 (2) |
C6—H6 | 0.9300 | C17—C18 | 1.410 (2) |
C7—C8 | 1.522 (3) | C18—C19 | 1.373 (3) |
C7—C9 | 1.530 (2) | C18—H18 | 0.9300 |
C7—C10 | 1.530 (2) | C19—C20 | 1.386 (3) |
C8—H8A | 0.9600 | C19—H19 | 0.9300 |
C8—H8B | 0.9600 | C20—C21 | 1.361 (3) |
C8—H8C | 0.9600 | C20—H20 | 0.9300 |
C9—H9A | 0.9600 | C21—H21 | 0.9300 |
C9—H9B | 0.9600 | ||
C11—N1—C2 | 130.69 (14) | C7—C10—H10A | 109.5 |
C11—N1—H1A | 114.8 (14) | C7—C10—H10B | 109.5 |
C2—N1—H1A | 114.5 (13) | H10A—C10—H10B | 109.5 |
C1—O1—H1 | 115.2 (17) | C7—C10—H10C | 109.5 |
O1—C1—C6 | 125.37 (16) | H10A—C10—H10C | 109.5 |
O1—C1—C2 | 116.10 (16) | H10B—C10—H10C | 109.5 |
C6—C1—C2 | 118.51 (16) | N1—C11—C12 | 122.65 (14) |
C3—C2—C1 | 120.80 (15) | N1—C11—H11 | 118.7 |
C3—C2—N1 | 125.08 (14) | C12—C11—H11 | 118.7 |
C1—C2—N1 | 114.10 (15) | C11—C12—C13 | 118.63 (14) |
C2—C3—C4 | 121.31 (14) | C11—C12—C17 | 121.36 (14) |
C2—C3—H3 | 119.3 | C13—C12—C17 | 119.94 (14) |
C4—C3—H3 | 119.3 | O2—C13—C12 | 122.04 (15) |
C3—C4—C5 | 116.85 (15) | O2—C13—C14 | 119.91 (15) |
C3—C4—C7 | 122.08 (14) | C12—C13—C14 | 118.05 (15) |
C5—C4—C7 | 120.94 (14) | C15—C14—C13 | 121.37 (17) |
C6—C5—C4 | 122.33 (16) | C15—C14—H14 | 119.3 |
C6—C5—H5 | 118.8 | C13—C14—H14 | 119.3 |
C4—C5—H5 | 118.8 | C14—C15—C16 | 122.31 (17) |
C5—C6—C1 | 120.16 (16) | C14—C15—H15 | 118.8 |
C5—C6—H6 | 119.9 | C16—C15—H15 | 118.8 |
C1—C6—H6 | 119.9 | C21—C16—C17 | 120.08 (17) |
C8—C7—C4 | 112.75 (14) | C21—C16—C15 | 120.88 (18) |
C8—C7—C9 | 107.67 (16) | C17—C16—C15 | 119.03 (16) |
C4—C7—C9 | 107.83 (15) | C18—C17—C16 | 117.20 (16) |
C8—C7—C10 | 108.57 (18) | C18—C17—C12 | 123.88 (15) |
C4—C7—C10 | 111.09 (16) | C16—C17—C12 | 118.92 (14) |
C9—C7—C10 | 108.81 (18) | C19—C18—C17 | 120.99 (19) |
C7—C8—H8A | 109.5 | C19—C18—H18 | 119.5 |
C7—C8—H8B | 109.5 | C17—C18—H18 | 119.5 |
H8A—C8—H8B | 109.5 | C18—C19—C20 | 121.3 (2) |
C7—C8—H8C | 109.5 | C18—C19—H19 | 119.4 |
H8A—C8—H8C | 109.5 | C20—C19—H19 | 119.4 |
H8B—C8—H8C | 109.5 | C21—C20—C19 | 119.22 (19) |
C7—C9—H9A | 109.5 | C21—C20—H20 | 120.4 |
C7—C9—H9B | 109.5 | C19—C20—H20 | 120.4 |
H9A—C9—H9B | 109.5 | C20—C21—C16 | 121.2 (2) |
C7—C9—H9C | 109.5 | C20—C21—H21 | 119.4 |
H9A—C9—H9C | 109.5 | C16—C21—H21 | 119.4 |
H9B—C9—H9C | 109.5 | ||
O1—C1—C2—C3 | −179.68 (17) | C11—C12—C13—O2 | −9.9 (2) |
C6—C1—C2—C3 | −1.0 (3) | C17—C12—C13—O2 | 173.26 (15) |
O1—C1—C2—N1 | 1.6 (2) | C11—C12—C13—C14 | 169.32 (14) |
C6—C1—C2—N1 | −179.72 (16) | C17—C12—C13—C14 | −7.5 (2) |
C11—N1—C2—C3 | −0.5 (3) | O2—C13—C14—C15 | −175.11 (16) |
C11—N1—C2—C1 | 178.15 (17) | C12—C13—C14—C15 | 5.7 (2) |
C1—C2—C3—C4 | −0.8 (2) | C13—C14—C15—C16 | −0.9 (3) |
N1—C2—C3—C4 | 177.84 (14) | C14—C15—C16—C21 | 177.19 (17) |
C2—C3—C4—C5 | 1.3 (2) | C14—C15—C16—C17 | −1.9 (3) |
C2—C3—C4—C7 | −174.50 (15) | C21—C16—C17—C18 | 0.1 (2) |
C3—C4—C5—C6 | −0.1 (3) | C15—C16—C17—C18 | 179.23 (16) |
C7—C4—C5—C6 | 175.70 (18) | C21—C16—C17—C12 | −179.21 (15) |
C4—C5—C6—C1 | −1.6 (3) | C15—C16—C17—C12 | −0.1 (2) |
O1—C1—C6—C5 | −179.3 (2) | C11—C12—C17—C18 | 8.8 (2) |
C2—C1—C6—C5 | 2.1 (3) | C13—C12—C17—C18 | −174.40 (16) |
C3—C4—C7—C8 | −13.7 (2) | C11—C12—C17—C16 | −171.94 (14) |
C5—C4—C7—C8 | 170.70 (18) | C13—C12—C17—C16 | 4.8 (2) |
C3—C4—C7—C9 | 105.05 (18) | C16—C17—C18—C19 | 0.2 (3) |
C5—C4—C7—C9 | −70.6 (2) | C12—C17—C18—C19 | 179.47 (17) |
C3—C4—C7—C10 | −135.80 (18) | C17—C18—C19—C20 | −0.2 (3) |
C5—C4—C7—C10 | 48.6 (2) | C18—C19—C20—C21 | 0.0 (3) |
C2—N1—C11—C12 | −174.92 (15) | C19—C20—C21—C16 | 0.3 (3) |
N1—C11—C12—C13 | 2.0 (2) | C17—C16—C21—C20 | −0.4 (3) |
N1—C11—C12—C17 | 178.81 (14) | C15—C16—C21—C20 | −179.5 (2) |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···O2i | 0.90 (3) | 1.69 (3) | 2.5846 (18) | 174 (3) |
N1—H1A···O2 | 0.91 (2) | 1.77 (2) | 2.5257 (19) | 139 (2) |
Symmetry code: (i) x−1/2, −y+3/2, −z+2. |
Experimental details
Crystal data | |
Chemical formula | C21H21NO2 |
Mr | 319.39 |
Crystal system, space group | Orthorhombic, P212121 |
Temperature (K) | 294 |
a, b, c (Å) | 6.1882 (6), 15.9350 (15), 17.2295 (16) |
V (Å3) | 1699.0 (3) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.08 |
Crystal size (mm) | 0.26 × 0.20 × 0.16 |
Data collection | |
Diffractometer | Bruker Model? CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 1996) |
Tmin, Tmax | 0.975, 0.987 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 11475, 2343, 2039 |
Rint | 0.022 |
(sin θ/λ)max (Å−1) | 0.659 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.032, 0.089, 1.06 |
No. of reflections | 2343 |
No. of parameters | 229 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.16, −0.13 |
Computer programs: XSCANS (Bruker, 1997), XSCANS, SHELXTL (Bruker, 1997), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), SHELXTL.
N1—C11 | 1.309 (2) | O2—C13 | 1.275 (2) |
N1—H1A | 0.91 (2) | C14—C15 | 1.338 (3) |
O1—H1 | 0.90 (3) | ||
C11—N1—C2 | 130.69 (14) | N1—C11—C12 | 122.65 (14) |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···O2i | 0.90 (3) | 1.69 (3) | 2.5846 (18) | 174 (3) |
N1—H1A···O2 | 0.91 (2) | 1.77 (2) | 2.5257 (19) | 139 (2) |
Symmetry code: (i) x−1/2, −y+3/2, −z+2. |
Schiff bases have been widely used as ligands in the formation of transition metal complexes (Elmali et al., 1998). Although many structures of transition metal complexes with Schiff base ligands have been determined, a relatively small number of free Schiff bases have been structurally characterized (Ünver et al., 2005). Schiff bases with an OH group in the position ortho to the imino group are of interest mainly becuase of the existence of either O—H···N or N—H···O hydrogen bonds and tautomerism between enol–imine and keto–amine forms (Ünver et al., 2005; Hökelek et al., 2000; Mondal et al., 2002). These Schiff bases usually have keto–amine form, and show photochromism, because the H atom from the phenol group is reversibly transferred to the imine N atom (Hadjoudis et al., 1987; Elmali et al., 1998).
Selected bond lengths and angles of the title compound are given in Table 1 and the molecular structure is shown in Fig. 1. In the title compound, either atom O1 or O2 may be hydrogen bonded to H1A, but the distance between O1 and H1A [2.10 (2) Å] is significantly longer than the bond length O2···H1A [1.77 (2) Å]. The N1—H1A···O2 hydrogen bond in (I) completes a six-membered chelate ring (C11/C12/C13/O2/H1A/N1), which creates greater π-delocalization with the naphthalene rings, increasing the stability of this compound.
The C14═C15 bond length [1.338 (3) Å] in the title compound is shorter than the expected value (1.40 Å). The C13═O2 bond length [1.275 (2) Å] is consistent with an O═C double bond. The corresponding bond lengths in a substituted naphtalenone are 1.351 (5) Å and 1.274 (4) Å, respectively (Hökelek, et al., 2000). The reason for the shortening of the C13═ O2 and C14═C15 bond lengths in (I) may be the quinoidal structure (keto–amine form), as in the naphthalimine reported by Đilović et al. (2005).
The N1—C11—C12 angle [122.65 (14)°] is near to 120°, while the C2—N1—C11 angle is 130.69 (14)°, thus decreasing the planarity of the whole molecule. The C1–C7 and O2/C11–C21 planes are inclined at an angle of 13.2°; this angle increases to 56.9° when a similar ligand is coordinated to a copper(II) ion (Ünver, 2002).
The O2···N1 distance of 2.5257 (19) Å is clearly indicative of a strong intermolecular hydrogen bond (Table 2); this distance is significantly shorter than the sum (3.07 Å) of the van der Waals radii for N and O atoms. At the same time, the N1—C11 distance of 1.309 (2) Å is slightly longer than a C═N double bond. All these bond lengths reveal that the keto tautomer (N—H···O) is favoured over the enol tautomer (O—H···N).
Intermolecular hydrogen bonds also exist in the crystal structure. Atom O2 is hydrogen bonded to O1#1 (Table 2) from the molecule at (x - 1/2, y + 3/2, -z + 2) [please check; does not match code #1 in Fig. 2], which links adjacent units together, forming a one-dimensional chain parallel to the a axis (Fig. 2).
In addition to hydrogen bonds, the crystal packing of compound (I) is also stabilized by π-stacking interactions between the naphthalene ring system (C12–C21) and the phenyl ring (C1#2–C6#2) at (x + 1, y, z). The distances between the planes and the centroids of the corresponding rings are 3.069 and 4.023 Å, respectively.