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In the crystal structure of the title compound, C21H21NO2, strong N—H...O and O—H...O hydrogen bonds exist. The keto–amine form is favoured over the enol–imine form in the tautomerism. Six-membered chelate rings formed by intra­molecular hydrogen bonds increase the stability of the whole mol­ecule. Inter­molecular hydrogen bonds link adjacent units together, forming an infinite one-dimensional chain parallel to the a axis.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270106051511/av3047sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270106051511/av3047Isup2.hkl
Contains datablock I

CCDC reference: 638313

Comment top

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 C14C15 bond length [1.338 (3) Å] in the title compound is shorter than the expected value (1.40 Å). The C13O2 bond length [1.275 (2) Å] is consistent with an OC 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 C14C15 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 CN 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.

Related literature top

For related literature, see: Elmali, Eleman & Zeyrek (1998); Hökelek et al. (2000); Hadjoudis et al. (1987); Mondal et al. (2002); Ünver (2002); Ünver et al. (2005); Đilović et al. (2005).

Experimental top

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.

Refinement top

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].

Computing details top

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.

Figures top
[Figure 1] Fig. 1. The molecular structure, showing 30% probability displacement ellipsoids.
[Figure 2] Fig. 2. The one-dimensionl hydrogen-bonded chain parallel to the a axis. Some H atoms and tertiary butyl groups have been omitted for clarity. [Symmetry codes: #1) 1/2 + x, 3/2 - y, 2 - z; #2) 1 + x, y, z; #3) -1/2 + x, 3/2 - y, 2 - z)
1-[(5-tert-Butyl-2-hydroxyphenyl)iminomethyl]-2-napthol top
Crystal data top
C21H21NO2Dx = 1.249 Mg m3
Mr = 319.39Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, P212121Cell parameters from 3942 reflections
a = 6.1882 (6) Åθ = 2.4–25.4°
b = 15.9350 (15) ŵ = 0.08 mm1
c = 17.2295 (16) ÅT = 294 K
V = 1699.0 (3) Å3Block, red
Z = 40.26 × 0.20 × 0.16 mm
F(000) = 680
Data collection top
Bruker Model? CCD area-detector
diffractometer
2343 independent reflections
Radiation source: fine-focus sealed tube2039 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.022
ϕ and ω scansθmax = 27.9°, θmin = 1.7°
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
h = 88
Tmin = 0.975, Tmax = 0.987k = 1520
11475 measured reflectionsl = 2222
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.032H 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 reflectionsΔρmax = 0.16 e Å3
229 parametersΔρmin = 0.13 e Å3
0 restraintsExtinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.0126 (17)
Crystal data top
C21H21NO2V = 1699.0 (3) Å3
Mr = 319.39Z = 4
Orthorhombic, P212121Mo Kα radiation
a = 6.1882 (6) ŵ = 0.08 mm1
b = 15.9350 (15) ÅT = 294 K
c = 17.2295 (16) Å0.26 × 0.20 × 0.16 mm
Data collection top
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 = 0.987Rint = 0.022
11475 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0320 restraints
wR(F2) = 0.089H atoms treated by a mixture of independent and constrained refinement
S = 1.06Δρmax = 0.16 e Å3
2343 reflectionsΔρmin = 0.13 e Å3
229 parameters
Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
N10.8843 (2)0.55923 (9)0.95496 (8)0.0390 (3)
H1A0.924 (4)0.6138 (13)0.9501 (11)0.054 (6)*
O10.7245 (3)0.69112 (8)1.01802 (10)0.0690 (5)
H10.684 (4)0.7366 (17)1.0452 (13)0.086 (8)*
O21.1329 (2)0.67339 (7)0.90636 (8)0.0527 (3)
C10.6253 (3)0.61894 (10)1.03795 (10)0.0473 (4)
C20.7063 (3)0.54589 (10)1.00378 (9)0.0376 (3)
C30.6158 (3)0.46859 (10)1.01996 (9)0.0359 (3)
H30.67120.42090.99610.043*
C40.4432 (3)0.46071 (10)1.07125 (9)0.0376 (3)
C50.3636 (3)0.53476 (11)1.10418 (11)0.0503 (4)
H50.24820.53151.13860.060*
C60.4502 (4)0.61232 (12)1.08742 (12)0.0564 (5)
H60.39080.66031.10940.068*
C70.3538 (3)0.37519 (11)1.09540 (9)0.0400 (4)
C80.4345 (4)0.30409 (12)1.04407 (12)0.0598 (6)
H8A0.58900.30041.04790.090*
H8B0.39450.31490.99120.090*
H8C0.37110.25221.06080.090*
C90.4302 (4)0.35749 (14)1.17824 (11)0.0635 (6)
H9A0.58530.35661.17950.095*
H9B0.37540.30411.19490.095*
H9C0.37780.40061.21230.095*
C100.1065 (3)0.37501 (15)1.09408 (15)0.0635 (5)
H10A0.05420.32221.11330.095*
H10B0.05690.38311.04180.095*
H10C0.05320.41961.12630.095*
C111.0025 (3)0.50606 (10)0.91556 (8)0.0362 (3)
H110.96260.44980.91520.043*
C121.1871 (3)0.53059 (10)0.87386 (8)0.0346 (3)
C131.2522 (3)0.61661 (10)0.87657 (9)0.0391 (4)
C141.4599 (3)0.63822 (11)0.84536 (10)0.0461 (4)
H141.51060.69290.85070.055*
C151.5821 (3)0.58138 (12)0.80873 (10)0.0483 (4)
H151.71490.59800.78860.058*
C161.5159 (3)0.49614 (12)0.79942 (9)0.0426 (4)
C171.3171 (3)0.46998 (10)0.83199 (8)0.0368 (4)
C181.2565 (3)0.38556 (11)0.82062 (10)0.0486 (4)
H181.12660.36630.84110.058*
C191.3864 (4)0.33142 (13)0.77978 (12)0.0614 (6)
H191.34320.27600.77320.074*
C201.5807 (4)0.35780 (15)0.74814 (13)0.0653 (6)
H201.66720.32050.72060.078*
C211.6436 (4)0.43900 (14)0.75778 (11)0.0572 (5)
H211.77350.45690.73640.069*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0404 (7)0.0305 (7)0.0462 (7)0.0006 (6)0.0059 (6)0.0027 (6)
O10.0846 (11)0.0324 (7)0.0899 (11)0.0023 (7)0.0361 (10)0.0123 (7)
O20.0554 (7)0.0325 (6)0.0703 (8)0.0038 (6)0.0093 (7)0.0100 (6)
C10.0566 (10)0.0333 (8)0.0520 (9)0.0039 (9)0.0098 (9)0.0046 (8)
C20.0385 (8)0.0362 (8)0.0380 (7)0.0043 (7)0.0035 (7)0.0017 (7)
C30.0342 (7)0.0345 (7)0.0390 (7)0.0057 (7)0.0010 (6)0.0050 (6)
C40.0367 (8)0.0402 (8)0.0360 (7)0.0027 (7)0.0009 (6)0.0034 (7)
C50.0496 (10)0.0501 (10)0.0511 (9)0.0061 (9)0.0166 (9)0.0059 (9)
C60.0646 (12)0.0415 (9)0.0630 (11)0.0094 (9)0.0212 (10)0.0115 (9)
C70.0343 (8)0.0455 (9)0.0400 (8)0.0014 (7)0.0026 (7)0.0015 (8)
C80.0672 (14)0.0449 (10)0.0673 (12)0.0128 (10)0.0164 (11)0.0106 (9)
C90.0734 (14)0.0649 (13)0.0523 (10)0.0078 (12)0.0129 (11)0.0098 (9)
C100.0385 (9)0.0702 (13)0.0819 (14)0.0067 (10)0.0006 (10)0.0056 (13)
C110.0406 (8)0.0301 (7)0.0377 (7)0.0006 (7)0.0008 (7)0.0016 (6)
C120.0365 (8)0.0327 (8)0.0345 (7)0.0003 (7)0.0008 (6)0.0009 (6)
C130.0439 (8)0.0354 (8)0.0380 (7)0.0033 (8)0.0016 (7)0.0002 (7)
C140.0487 (10)0.0410 (9)0.0486 (9)0.0121 (8)0.0007 (8)0.0049 (7)
C150.0402 (9)0.0572 (11)0.0474 (9)0.0081 (9)0.0056 (8)0.0073 (8)
C160.0409 (9)0.0495 (10)0.0373 (7)0.0032 (8)0.0018 (7)0.0048 (7)
C170.0403 (8)0.0364 (8)0.0337 (7)0.0033 (7)0.0016 (6)0.0026 (6)
C180.0530 (10)0.0390 (9)0.0538 (10)0.0012 (9)0.0134 (9)0.0019 (8)
C190.0740 (14)0.0393 (10)0.0710 (13)0.0087 (11)0.0170 (12)0.0073 (9)
C200.0655 (13)0.0598 (13)0.0705 (13)0.0197 (11)0.0213 (12)0.0064 (11)
C210.0484 (11)0.0655 (13)0.0578 (11)0.0082 (10)0.0146 (9)0.0006 (10)
Geometric parameters (Å, º) top
N1—C111.309 (2)C9—H9C0.9600
N1—C21.402 (2)C10—H10A0.9600
N1—H1A0.91 (2)C10—H10B0.9600
O1—C11.348 (2)C10—H10C0.9600
O1—H10.90 (3)C11—C121.405 (2)
O2—C131.275 (2)C11—H110.9300
C1—C61.382 (3)C12—C131.429 (2)
C1—C21.397 (2)C12—C171.449 (2)
C2—C31.382 (2)C13—C141.435 (2)
C3—C41.392 (2)C14—C151.338 (3)
C3—H30.9300C14—H140.9300
C4—C51.399 (2)C15—C161.428 (3)
C4—C71.529 (2)C15—H150.9300
C5—C61.378 (3)C16—C211.403 (3)
C5—H50.9300C16—C171.415 (2)
C6—H60.9300C17—C181.410 (2)
C7—C81.522 (3)C18—C191.373 (3)
C7—C91.530 (2)C18—H180.9300
C7—C101.530 (2)C19—C201.386 (3)
C8—H8A0.9600C19—H190.9300
C8—H8B0.9600C20—C211.361 (3)
C8—H8C0.9600C20—H200.9300
C9—H9A0.9600C21—H210.9300
C9—H9B0.9600
C11—N1—C2130.69 (14)C7—C10—H10A109.5
C11—N1—H1A114.8 (14)C7—C10—H10B109.5
C2—N1—H1A114.5 (13)H10A—C10—H10B109.5
C1—O1—H1115.2 (17)C7—C10—H10C109.5
O1—C1—C6125.37 (16)H10A—C10—H10C109.5
O1—C1—C2116.10 (16)H10B—C10—H10C109.5
C6—C1—C2118.51 (16)N1—C11—C12122.65 (14)
C3—C2—C1120.80 (15)N1—C11—H11118.7
C3—C2—N1125.08 (14)C12—C11—H11118.7
C1—C2—N1114.10 (15)C11—C12—C13118.63 (14)
C2—C3—C4121.31 (14)C11—C12—C17121.36 (14)
C2—C3—H3119.3C13—C12—C17119.94 (14)
C4—C3—H3119.3O2—C13—C12122.04 (15)
C3—C4—C5116.85 (15)O2—C13—C14119.91 (15)
C3—C4—C7122.08 (14)C12—C13—C14118.05 (15)
C5—C4—C7120.94 (14)C15—C14—C13121.37 (17)
C6—C5—C4122.33 (16)C15—C14—H14119.3
C6—C5—H5118.8C13—C14—H14119.3
C4—C5—H5118.8C14—C15—C16122.31 (17)
C5—C6—C1120.16 (16)C14—C15—H15118.8
C5—C6—H6119.9C16—C15—H15118.8
C1—C6—H6119.9C21—C16—C17120.08 (17)
C8—C7—C4112.75 (14)C21—C16—C15120.88 (18)
C8—C7—C9107.67 (16)C17—C16—C15119.03 (16)
C4—C7—C9107.83 (15)C18—C17—C16117.20 (16)
C8—C7—C10108.57 (18)C18—C17—C12123.88 (15)
C4—C7—C10111.09 (16)C16—C17—C12118.92 (14)
C9—C7—C10108.81 (18)C19—C18—C17120.99 (19)
C7—C8—H8A109.5C19—C18—H18119.5
C7—C8—H8B109.5C17—C18—H18119.5
H8A—C8—H8B109.5C18—C19—C20121.3 (2)
C7—C8—H8C109.5C18—C19—H19119.4
H8A—C8—H8C109.5C20—C19—H19119.4
H8B—C8—H8C109.5C21—C20—C19119.22 (19)
C7—C9—H9A109.5C21—C20—H20120.4
C7—C9—H9B109.5C19—C20—H20120.4
H9A—C9—H9B109.5C20—C21—C16121.2 (2)
C7—C9—H9C109.5C20—C21—H21119.4
H9A—C9—H9C109.5C16—C21—H21119.4
H9B—C9—H9C109.5
O1—C1—C2—C3179.68 (17)C11—C12—C13—O29.9 (2)
C6—C1—C2—C31.0 (3)C17—C12—C13—O2173.26 (15)
O1—C1—C2—N11.6 (2)C11—C12—C13—C14169.32 (14)
C6—C1—C2—N1179.72 (16)C17—C12—C13—C147.5 (2)
C11—N1—C2—C30.5 (3)O2—C13—C14—C15175.11 (16)
C11—N1—C2—C1178.15 (17)C12—C13—C14—C155.7 (2)
C1—C2—C3—C40.8 (2)C13—C14—C15—C160.9 (3)
N1—C2—C3—C4177.84 (14)C14—C15—C16—C21177.19 (17)
C2—C3—C4—C51.3 (2)C14—C15—C16—C171.9 (3)
C2—C3—C4—C7174.50 (15)C21—C16—C17—C180.1 (2)
C3—C4—C5—C60.1 (3)C15—C16—C17—C18179.23 (16)
C7—C4—C5—C6175.70 (18)C21—C16—C17—C12179.21 (15)
C4—C5—C6—C11.6 (3)C15—C16—C17—C120.1 (2)
O1—C1—C6—C5179.3 (2)C11—C12—C17—C188.8 (2)
C2—C1—C6—C52.1 (3)C13—C12—C17—C18174.40 (16)
C3—C4—C7—C813.7 (2)C11—C12—C17—C16171.94 (14)
C5—C4—C7—C8170.70 (18)C13—C12—C17—C164.8 (2)
C3—C4—C7—C9105.05 (18)C16—C17—C18—C190.2 (3)
C5—C4—C7—C970.6 (2)C12—C17—C18—C19179.47 (17)
C3—C4—C7—C10135.80 (18)C17—C18—C19—C200.2 (3)
C5—C4—C7—C1048.6 (2)C18—C19—C20—C210.0 (3)
C2—N1—C11—C12174.92 (15)C19—C20—C21—C160.3 (3)
N1—C11—C12—C132.0 (2)C17—C16—C21—C200.4 (3)
N1—C11—C12—C17178.81 (14)C15—C16—C21—C20179.5 (2)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1—H1···O2i0.90 (3)1.69 (3)2.5846 (18)174 (3)
N1—H1A···O20.91 (2)1.77 (2)2.5257 (19)139 (2)
Symmetry code: (i) x1/2, y+3/2, z+2.

Experimental details

Crystal data
Chemical formulaC21H21NO2
Mr319.39
Crystal system, space groupOrthorhombic, P212121
Temperature (K)294
a, b, c (Å)6.1882 (6), 15.9350 (15), 17.2295 (16)
V3)1699.0 (3)
Z4
Radiation typeMo Kα
µ (mm1)0.08
Crystal size (mm)0.26 × 0.20 × 0.16
Data collection
DiffractometerBruker Model? CCD area-detector
diffractometer
Absorption correctionMulti-scan
(SADABS; Sheldrick, 1996)
Tmin, Tmax0.975, 0.987
No. of measured, independent and
observed [I > 2σ(I)] reflections
11475, 2343, 2039
Rint0.022
(sin θ/λ)max1)0.659
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.032, 0.089, 1.06
No. of reflections2343
No. of parameters229
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.16, 0.13

Computer programs: XSCANS (Bruker, 1997), XSCANS, SHELXTL (Bruker, 1997), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), SHELXTL.

Selected geometric parameters (Å, º) top
N1—C111.309 (2)O2—C131.275 (2)
N1—H1A0.91 (2)C14—C151.338 (3)
O1—H10.90 (3)
C11—N1—C2130.69 (14)N1—C11—C12122.65 (14)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1—H1···O2i0.90 (3)1.69 (3)2.5846 (18)174 (3)
N1—H1A···O20.91 (2)1.77 (2)2.5257 (19)139 (2)
Symmetry code: (i) x1/2, y+3/2, z+2.
 

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