supplementary materials


HTML versionpdf versioncif file3d viewstructure factorssupplementary materialsCIF check reportsimilar papers buy article online

Acta Cryst. (2007). E63, o3746    [ doi:10.1107/S1600536807038615 ]

2,4-Di-tert-butyl-6-(4-nitrophenyliminomethyl)phenol

Y.-F. Sun, X.-L. Wang, S.-Y. Ma and H.-J. Chen

Abstract top

In the title compound, C21H26N2O3, the molecule adopts an E configuration about the central C=N double bond and exists in the phenol-imine tautomeric form. The two benzene rings make a dihedral angle of 38.5 (4)°. Intramolecular O-H...N hydrogen bonding is present.

Comment top

Schiff bases have demonstrated significant biological activities and new examples are being tested for their antitumor, antimicrobial and antiviral activities (Siddiqui et al., 2006). Moreover, Schiff base compounds can be classified by their photochromic and thermochromic characteristics (Unver et al., 2002). Schiff bases have also been employed as ligands for metal complexes (Selvakumar et al., 2007) and as optical sensor (Oter et al., 2007). We herein report the synthesis and crystal structure of the title compound, (I), (Fig.1). The molecule of (I) is not planar and possesses normal geometric parameters. The molecule has E-configuration, across the C=N double bond. A dihedral angle of 38.5 (4)° is found between the mean planes of the two benzene rings. Also, while C14, C17, C18 and C21 are approximately coplanar with their attached benzene ring, C15,C16, C19 and C20 deviate by −1.1043 (5), 1.3469 (5), −1.2082 (6) and 1.3013 (5) Å, respectively. In addition, there is an intramolecular N···H—O hydrogen bond between the N1 and O1 atoms, which makes the phenol-imine form. Similar tautomerism has also been observed in related Schiff bases reported by Sun et al. (2007) and Aazam et al. (2006). However, this is obviously different from other reported Schiff base, in which the Schiff base exist in enamine-keto tautomeric form (Hokelek et al., 2000).

Related literature top

For general literature concerning applications of benzothiazole compounds, see: Siddiqui et al. (2006); Unver et al. (2002); Selvakumar et al. (2007); Oter et al. (2007). Similar tautomerism has also been observed in related Schiff bases reported by Sun et al. (2007) and Aazam et al. (2006). Other reported Schiff bases exist in enamine–keto tautomeric form (Hokelek et al., 2000).

Experimental top

A mixture of 4-nitroaniline (1 mmol) and 3,5-di-tert-butyl-2- hydroxybenzaldehyde (1 mmol) in anhydrous ethanol (30 ml) was refluxed for 3 hr, and then cooled to room temperature. The precipitate was filtered and dried. The crude product was recrystallized from ethanol. Red crystals were thus obtained in 79% yield. Analysis calculated for C21H26N2O3: C, 71.16; H, 7.39; N, 7.90. Found (%): C, 71.33; H, 7.28; N, 7.76. A single-crystal suitable for an X-ray structural analysis was obtained by slowly evaporating a ethanolic solution at room temperature.

Refinement top

All H atoms were initially located in a difference Fourier map. The methyl H atoms were then constrained to an ideal geometry with C—H distances of 0.96 Å and Uiso(H) = 1.5Ueq(C). The hydroxyl H atoms were refined freely along with an isotropic displacement parameter. All other H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms with C—H distances of 0.93 Å d and Uiso(H) = 1.2Ueq(C).

Computing details top

Data collection: R-AXIS (Rigaku, 1996); cell refinement: R-AXIS; data reduction: R-AXIS; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: TEXSAN (Molecular Structure Corporation, 1999); software used to prepare material for publication: TEXSAN.

Figures top
[Figure 1] Fig. 1. View of the molecule of (I) showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms are shown as small spheres of arbitrary radii·The dashed lines indicate hydrogen bonds.
2,4-Di-tert-butyl-6-(4-nitrophenyliminomethyl)phenol top
Crystal data top
C21H26N2O3F000 = 760
Mr = 354.44Dx = 1.160 Mg m−3
Monoclinic, P21/cMo Kα radiation
λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 389 reflections
a = 17.937 (4) Åθ = 2–25.1º
b = 6.4674 (13) ŵ = 0.08 mm−1
c = 19.047 (4) ÅT = 291 (2) K
β = 113.31 (3)ºPrismatic, red
V = 2029.2 (7) Å30.20 × 0.18 × 0.16 mm
Z = 4
Data collection top
Rigaku R-AXIS-IV
diffractometer		3066 independent reflections
Radiation source: fine-focus sealed tube1226 reflections with I > 2σ(I)
Monochromator: graphiteRint = 0.074
T = 291(2) Kθmax = 25.0º
Oscillation frames scansθmin = 1.2º
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)		h = 0→21
Tmin = 0.985, Tmax = 0.988k = −7→7
4678 measured reflectionsl = −22→20
Refinement top
Refinement on F2Hydrogen site location: difference Fourier map
Least-squares matrix: fullH atoms treated by a mixture of
independent and constrained refinement
R[F2 > 2σ(F2)] = 0.078  w = 1/[σ2(Fo2) + (0.062P)2]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.176(Δ/σ)max < 0.001
S = 0.97Δρmax = 0.19 e Å−3
3066 reflectionsΔρmin = −0.15 e Å−3
240 parametersExtinction correction: SHELXL97
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.0059 (13)
Secondary atom site location: difference Fourier map
Crystal data top
C21H26N2O3V = 2029.2 (7) Å3
Mr = 354.44Z = 4
Monoclinic, P21/cMo Kα
a = 17.937 (4) ŵ = 0.08 mm−1
b = 6.4674 (13) ÅT = 291 (2) K
c = 19.047 (4) Å0.20 × 0.18 × 0.16 mm
β = 113.31 (3)º
Data collection top
Rigaku R-AXIS-IV
diffractometer		3066 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)		1226 reflections with I > 2σ(I)
Tmin = 0.985, Tmax = 0.988Rint = 0.074
4678 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.078240 parameters
wR(F2) = 0.176H atoms treated by a mixture of
independent and constrained refinement
S = 0.97Δρmax = 0.19 e Å−3
3066 reflectionsΔρmin = −0.15 e Å−3
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.

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 > 2sigma(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
N10.1937 (2)0.6463 (6)0.0192 (2)0.0652 (12)
N2−0.0060 (3)1.3225 (9)−0.1296 (4)0.0959 (18)
O10.3061 (2)0.3763 (5)0.03105 (19)0.0711 (11)
O2−0.0154 (3)1.4634 (7)−0.0908 (3)0.1241 (18)
O3−0.0361 (4)1.3241 (9)−0.1982 (3)0.177 (3)
C10.3001 (3)0.3053 (7)0.0964 (3)0.0533 (13)
C20.3475 (3)0.1359 (7)0.1350 (3)0.0517 (13)
C30.3358 (3)0.0701 (7)0.1993 (2)0.0555 (13)
H3A0.3667−0.04130.22620.067*
C40.2812 (3)0.1577 (8)0.2269 (2)0.0531 (13)
C50.2370 (3)0.3253 (7)0.1876 (3)0.0580 (14)
H5A0.20100.38960.20480.070*
C60.2454 (3)0.4011 (7)0.1219 (3)0.0503 (13)
C70.1950 (3)0.5732 (8)0.0823 (3)0.0626 (15)
H7A0.16190.63410.10360.075*
C80.1424 (3)0.8192 (8)−0.0155 (3)0.0612 (14)
C90.1280 (3)0.9791 (8)0.0259 (3)0.0711 (15)
H9A0.15120.97510.07910.085*
C100.0792 (3)1.1455 (8)−0.0111 (4)0.0720 (16)
H10A0.06911.25210.01670.086*
C110.0464 (3)1.1489 (10)−0.0892 (4)0.0708 (16)
C120.0606 (3)0.9961 (11)−0.1317 (3)0.0850 (18)
H12A0.03761.0026−0.18480.102*
C130.1093 (3)0.8326 (9)−0.0950 (3)0.0799 (17)
H13A0.12030.7295−0.12360.096*
C140.2742 (3)0.0730 (8)0.2992 (3)0.0622 (14)
C150.2590 (4)−0.1590 (8)0.2925 (3)0.117 (2)
H15A0.3016−0.22630.28270.175*
H15B0.2078−0.18650.25120.175*
H15C0.2579−0.21050.33940.175*
C160.3554 (4)0.1089 (9)0.3677 (3)0.105 (2)
H16A0.39820.03980.35870.158*
H16B0.35200.05480.41330.158*
H16C0.36670.25440.37380.158*
C170.2078 (3)0.1812 (9)0.3168 (3)0.106 (2)
H17A0.21820.32720.32170.160*
H17B0.20730.12810.36370.160*
H17C0.15600.15630.27590.160*
C180.4088 (3)0.0318 (8)0.1086 (3)0.0594 (14)
C190.3662 (3)−0.0516 (7)0.0269 (3)0.0775 (17)
H19A0.3270−0.15400.02570.116*
H19B0.4057−0.11280.01090.116*
H19C0.33940.0598−0.00690.116*
C200.4737 (3)0.1925 (8)0.1101 (3)0.0867 (18)
H20A0.44760.30680.07750.130*
H20B0.51140.12880.09240.130*
H20C0.50230.24130.16140.130*
C210.4521 (4)−0.1499 (9)0.1605 (3)0.112 (2)
H21A0.4128−0.25180.15960.168*
H21B0.4804−0.10100.21180.168*
H21C0.4901−0.21050.14250.168*
H1E0.264 (4)0.487 (11)0.015 (4)0.17 (3)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.068 (3)0.056 (3)0.069 (3)0.001 (3)0.023 (3)0.007 (3)
N20.082 (4)0.086 (5)0.119 (6)0.010 (4)0.039 (4)0.030 (5)
O10.093 (3)0.072 (3)0.064 (2)0.006 (2)0.048 (2)0.011 (2)
O20.110 (4)0.097 (4)0.166 (5)0.030 (3)0.054 (3)0.033 (3)
O30.211 (6)0.175 (6)0.105 (4)0.071 (4)0.021 (4)0.057 (4)
C10.063 (4)0.056 (3)0.049 (3)−0.004 (3)0.031 (3)−0.005 (3)
C20.055 (3)0.056 (3)0.046 (3)−0.001 (3)0.021 (3)0.000 (3)
C30.060 (3)0.057 (3)0.053 (3)0.004 (3)0.026 (3)0.001 (3)
C40.058 (3)0.058 (4)0.049 (3)−0.004 (3)0.029 (3)−0.007 (3)
C50.071 (4)0.057 (3)0.062 (3)0.000 (3)0.042 (3)−0.007 (3)
C60.054 (3)0.042 (3)0.056 (3)0.000 (3)0.023 (3)0.000 (3)
C70.065 (4)0.059 (4)0.069 (4)−0.009 (3)0.033 (3)−0.008 (3)
C80.064 (4)0.056 (4)0.059 (4)−0.011 (3)0.020 (3)0.000 (3)
C90.077 (4)0.058 (4)0.063 (4)−0.006 (3)0.012 (3)−0.004 (4)
C100.066 (4)0.055 (4)0.081 (5)−0.003 (3)0.015 (4)0.001 (4)
C110.049 (4)0.066 (4)0.091 (5)0.004 (3)0.021 (4)0.017 (4)
C120.085 (5)0.092 (5)0.071 (4)0.012 (4)0.023 (4)0.019 (4)
C130.095 (5)0.087 (5)0.068 (4)0.007 (4)0.044 (4)−0.001 (4)
C140.075 (4)0.069 (4)0.052 (3)−0.008 (3)0.035 (3)−0.007 (3)
C150.189 (7)0.083 (5)0.124 (5)−0.023 (5)0.110 (5)0.000 (4)
C160.116 (5)0.149 (6)0.067 (4)−0.001 (5)0.054 (4)0.007 (4)
C170.120 (5)0.135 (5)0.103 (5)0.033 (4)0.086 (5)0.030 (4)
C180.063 (4)0.069 (4)0.059 (3)0.001 (3)0.038 (3)−0.007 (3)
C190.095 (4)0.072 (4)0.085 (4)−0.002 (3)0.057 (4)−0.016 (3)
C200.067 (4)0.118 (5)0.085 (4)−0.014 (4)0.040 (3)−0.022 (4)
C210.130 (5)0.124 (5)0.116 (5)0.073 (5)0.086 (5)0.047 (5)
Geometric parameters (Å, °) top
N1—C71.283 (5)C12—H12A0.9300
N1—C81.432 (6)C13—H13A0.9300
N2—O31.200 (6)C14—C151.521 (6)
N2—O21.226 (6)C14—C171.529 (6)
N2—C111.471 (7)C14—C161.541 (7)
O1—C11.371 (5)C15—H15A0.9600
O1—H1E1.00 (7)C15—H15B0.9600
C1—C61.398 (5)C15—H15C0.9600
C1—C21.403 (6)C16—H16A0.9600
C2—C31.388 (5)C16—H16B0.9600
C2—C181.534 (5)C16—H16C0.9600
C3—C41.402 (5)C17—H17A0.9600
C3—H3A0.9300C17—H17B0.9600
C4—C51.376 (5)C17—H17C0.9600
C4—C141.533 (6)C18—C191.534 (6)
C5—C61.407 (5)C18—C211.534 (6)
C5—H5A0.9300C18—C201.553 (6)
C6—C71.445 (6)C19—H19A0.9600
C7—H7A0.9300C19—H19B0.9600
C8—C91.386 (6)C19—H19C0.9600
C8—C131.394 (6)C20—H20A0.9600
C9—C101.391 (6)C20—H20B0.9600
C9—H9A0.9300C20—H20C0.9600
C10—C111.366 (6)C21—H21A0.9600
C10—H10A0.9300C21—H21B0.9600
C11—C121.365 (7)C21—H21C0.9600
C12—C131.373 (6)
C7—N1—C8119.3 (4)C17—C14—C4112.4 (4)
O3—N2—O2122.7 (7)C15—C14—C16107.3 (5)
O3—N2—C11119.8 (7)C17—C14—C16107.7 (4)
O2—N2—C11117.5 (6)C4—C14—C16108.7 (4)
C1—O1—H1E101 (4)C14—C15—H15A109.5
O1—C1—C6119.0 (4)C14—C15—H15B109.5
O1—C1—C2119.2 (4)H15A—C15—H15B109.5
C6—C1—C2121.8 (4)C14—C15—H15C109.5
C3—C2—C1115.4 (4)H15A—C15—H15C109.5
C3—C2—C18122.2 (4)H15B—C15—H15C109.5
C1—C2—C18122.4 (4)C14—C16—H16A109.5
C2—C3—C4125.4 (4)C14—C16—H16B109.5
C2—C3—H3A117.3H16A—C16—H16B109.5
C4—C3—H3A117.3C14—C16—H16C109.5
C5—C4—C3116.8 (4)H16A—C16—H16C109.5
C5—C4—C14122.5 (4)H16B—C16—H16C109.5
C3—C4—C14120.7 (5)C14—C17—H17A109.5
C4—C5—C6121.1 (4)C14—C17—H17B109.5
C4—C5—H5A119.4H17A—C17—H17B109.5
C6—C5—H5A119.4C14—C17—H17C109.5
C1—C6—C5119.4 (4)H17A—C17—H17C109.5
C1—C6—C7122.7 (4)H17B—C17—H17C109.5
C5—C6—C7117.9 (4)C19—C18—C2110.7 (4)
N1—C7—C6123.3 (5)C19—C18—C21107.8 (4)
N1—C7—H7A118.3C2—C18—C21111.8 (4)
C6—C7—H7A118.3C19—C18—C20108.8 (3)
C9—C8—C13118.5 (5)C2—C18—C20109.3 (4)
C9—C8—N1123.4 (5)C21—C18—C20108.4 (4)
C13—C8—N1118.0 (5)C18—C19—H19A109.5
C8—C9—C10120.7 (5)C18—C19—H19B109.5
C8—C9—H9A119.6H19A—C19—H19B109.5
C10—C9—H9A119.6C18—C19—H19C109.5
C11—C10—C9118.6 (5)H19A—C19—H19C109.5
C11—C10—H10A120.7H19B—C19—H19C109.5
C9—C10—H10A120.7C18—C20—H20A109.5
C12—C11—C10122.3 (6)C18—C20—H20B109.5
C12—C11—N2118.2 (6)H20A—C20—H20B109.5
C10—C11—N2119.6 (6)C18—C20—H20C109.5
C11—C12—C13119.1 (6)H20A—C20—H20C109.5
C11—C12—H12A120.5H20B—C20—H20C109.5
C13—C12—H12A120.5C18—C21—H21A109.5
C12—C13—C8120.9 (5)C18—C21—H21B109.5
C12—C13—H13A119.6H21A—C21—H21B109.5
C8—C13—H13A119.6C18—C21—H21C109.5
C15—C14—C17109.9 (4)H21A—C21—H21C109.5
C15—C14—C4110.7 (4)H21B—C21—H21C109.5
O1—C1—C2—C3−178.1 (4)C9—C10—C11—C12−0.7 (8)
C6—C1—C2—C30.5 (6)C9—C10—C11—N2179.6 (4)
O1—C1—C2—C182.5 (6)O3—N2—C11—C121.7 (8)
C6—C1—C2—C18−178.9 (4)O2—N2—C11—C12−176.8 (5)
C1—C2—C3—C40.5 (6)O3—N2—C11—C10−178.6 (6)
C18—C2—C3—C4179.9 (4)O2—N2—C11—C102.9 (8)
C2—C3—C4—C5−1.4 (7)C10—C11—C12—C130.3 (8)
C2—C3—C4—C14−179.3 (4)N2—C11—C12—C13180.0 (5)
C3—C4—C5—C61.4 (7)C11—C12—C13—C81.5 (8)
C14—C4—C5—C6179.2 (4)C9—C8—C13—C12−2.7 (7)
O1—C1—C6—C5178.1 (4)N1—C8—C13—C12−179.1 (4)
C2—C1—C6—C5−0.5 (7)C5—C4—C14—C15129.0 (5)
O1—C1—C6—C7−0.3 (6)C3—C4—C14—C15−53.3 (6)
C2—C1—C6—C7−178.9 (4)C5—C4—C14—C175.7 (7)
C4—C5—C6—C1−0.5 (7)C3—C4—C14—C17−176.5 (4)
C4—C5—C6—C7177.9 (4)C5—C4—C14—C16−113.4 (5)
C8—N1—C7—C6−179.2 (4)C3—C4—C14—C1664.4 (6)
C1—C6—C7—N13.0 (7)C3—C2—C18—C19121.2 (5)
C5—C6—C7—N1−175.3 (4)C1—C2—C18—C19−59.5 (6)
C7—N1—C8—C935.8 (7)C3—C2—C18—C211.0 (6)
C7—N1—C8—C13−148.0 (5)C1—C2—C18—C21−179.7 (4)
C13—C8—C9—C102.3 (7)C3—C2—C18—C20−119.0 (5)
N1—C8—C9—C10178.4 (4)C1—C2—C18—C2060.3 (6)
C8—C9—C10—C11−0.6 (7)
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
O1—H1E···N11.00 (7)1.65 (7)2.609 (5)159 (6)
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
O1—H1E···N11.00 (7)1.65 (7)2.609 (5)159 (6)
Acknowledgements top

This project was supported by the Foundation of Taishan University.

references
References top

Aazam, E. S., Fawazy, A. & Hitchcock, P. B. (2006). Acta Cryst. E62, o4285–o4287.

Hokelek, T., Isiklan, M. & Kilic, Z. (2000). Anal. Sci. 16, 99–100.

Molecular Structure Corporation (1999). TEXSAN. Version 1.10. MSC, The Woodlands, Texas, USA.

Oter, O., Ertekin, K., Kilincarslan, R., Ulusoy, M., Cetinkaya, B., et al. (2007). Dyes Pigm. 74, 730–735.

Rigaku (1996). R-AXIS. Rigaku Corporation, Tokyo, Japan.

Selvakumar, P. M., Suresh, E. & Subramanian, P. S. (2007). Polyhedron, 26, 749–756.

Sheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.

Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.

Siddiqui, H. L., Iqbal, A., Ahmad, S. & Weaver, G. W. (2006). Molecules, 11, 206–211.

Sun, Y.-F., Li, J.-K., Zheng, Z.-B. & Wu, R.-T. (2007). Acta Cryst. E63, o2522–o2523.

Unver, H., Kendi, E., Guven, K. & Durlu, T. N. Z. (2002). Z. Naturforsch. Teil B, 57, 685–690.