organic compounds
3-[(Z)-(4-Diethylamino-6-oxocyclohexa-2,4-dien-1-ylidene)methylamino]benzoic acid
aDepartment of Chemistry, Sambhram Institute of Technology, Bangalore 560 098, India, bDepartment of Studies in Chemistry, Mangalore University, Mangalagangotri 574 199, India, cDepartment of Studies in Chemistry, University of Mysore, Manasagangotri, Mysore 570 006, India, dDepartment of Chemistry, P. A. College of Engineering, Nadupadavu, Mangalore 574 153, India, and eDepartment of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznań, Poland
*Correspondence e-mail: mkubicki@amu.edu.pl
The title compound, C18H20N2O3, crystallizes as the keto tautomer, unlike the vast majority of similar structures that have been reported that contain the hydroxy tautomer. There are two strong hydrogen bonds in the both accepted by the same carbonyl group: one intramolecular N—H⋯O and one intermolecular O—H⋯O. As a result, the carbonyl C=O distance is long, at 1.310 (2) Å, which may suggest the molecule has a significant zwitterionic character. The dihedral angle between the benzene ring planes is 15.05 (7)°. As a result of the intramolecular hydrogen bond, the bridging C—C=N—C group is almost coplanar with the benzene ring that has the diethylamino substituent [dihedral angle 2.35 (15)°].
Related literature
For related structures, see: Büyükgüngör et al. (2007); Odabaşoğlu et al. (2007); Yathirajan et al. (2007). For biological applications, see Hodnett & Dunn (1970); Misra et al. (1981); Agarwal et al. (1983); Varma et al. (1986); Singh & Dash (1988). For related literature, see: Allen (2002).
Experimental
Crystal data
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Data collection
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Refinement
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Data collection: CrysAlis CCD (Oxford Diffraction, 2006); cell CrysAlis RED (Oxford Diffraction, 2006); data reduction: CrysAlis RED; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP (Siemens, 1989); software used to prepare material for publication: SHELXL97and WinGX (Farrugia, 1999).
Supporting information
https://doi.org/10.1107/S1600536807064446/cs2063sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536807064446/cs2063Isup2.hkl
A mixture of 3-aminobenzoic acid (1.37 g, 0.01 mol) and 4-(diethylamino)-2-hydroxybenzaldehyde (1.92 g, 0.01 mol) in 25 ml of absolute ethanol containing 2 drops of 4 M sulfuric acid was refluxed for about 5 h. On cooling, the separated solid was filtered and recrystallized from DMF (m.p.: 483–485 K). The expected product was 3-({(1E)-[4-(diethylamino)-2-hydroxyphenyl]methylene}amino)benzoic acid, but the obtained product was the tautomeric form 3-({(Z)-[4-(diethylamino)-6-oxocyclohexa-2,4-dien-1-ylidene]methyl} amino)benzoic acid. Analysis for C18H20N2O3: Found (Calculated): C: 69.12 (69.21); H: 6.38 (6.45); N: 8.90% (8.97%).
The hydrogen atoms were located in the difference Fourier maps and refined as 'riding model'. Isotropic displacement parameters for hydrogen atoms were set at 1.2 (1.3 for methyl group) times the Ueq values of appropriate carrier atoms.
Schiff bases are used as substrates in the preparation of number of industrial and biologically active compounds via ring closure,
and replacement reactions. Some Schiff base derivatives were reported to possess antimicrobial, anti-inflammatory and central nervous system activities. Moreover, are also known to have biological activities such as antimicrobial, antifungal, antitumor and as herbicides (e.g. Hodnett et al., 1970, Singh & Dash, 1988, Varma et al., (1986)). In the course of our studies of (e.g. Büyükgüngör et al., 2007; Odabaşoğlu et al., 2007; Yathirajan et al., 2007), the title compound, C18H20N2O3 was synthesized and its is reported.The title compound crystallizes as the keto-tautomer (Fig. 1), unlike the majority of the similar compounds. In the CSD (Allen, 2002) the hydroxy tautomers were found in 218 compounds while the keto ones only in 17 compounds (Version Nov. 2006, updates up to August 2007; only organic compounds). In this case the presence of the certain tautomer is proven by the succesful location and
of the hydrogen atom bonded to N7 nitrogen atom (Fig. 2a). Short and relatively linear intramolecular N—H···O hydrogen bond forms an almost planar (maximum deviation 0.017 (1) Å) six-membered ring. The same O10 oxygen atom which accepts the intramolecular hydrogen bond is involved in a very short (O···O distance is 2.467 (1) Å) intermolecular O—H···O hydrogen bond. As a result the C10—O10 bond of 1.310 (2)Å is significantly longer than a typical C?O double bond. CSD search results show that such elongation is typical for similar compounds, the mean C—O distance being 1.348 (17)Å for hydroxy tautomers, but it may also be as large as 1.299 (17)Å also for the keto-tautomers. Together with the observation of bond lengths around N7 atom this implies some degree of zwitterionic character of the molecule, with partial positive charge at N7—H7 group and negative at O10 atom. These perturbations disturb also the benzene ring. The ring A (C1 - C6) is closer to planarity than the ring B (C9 - C14). Maximum deviations from the least-squares planes are 0.0103 (11)Å for ring A and 0.0219 (12)Å for ring B. Also the bond lengths and angles are much more uniform within the ring A than in ring B.The conformation of the molecule is described by the dihedral angles between benzene ring planes of 15.05 (7)°. As a result of the intramolecular hydrogen bond, the bridging C—C?N—C group is almost coplanar with the ring B (dihedral angle 2.35 (15)°). The COO group is significantly, by 21.73 (10)°, twisted with respect to its parent ring's plane. On the other end of the molecule, the C—N—C fragment is twisted by 17.0 (2)°, while the terminal C—C bonds are almost perpendicular to the CNC plane.
In the
the molecules are connected by strong intermolecular O—H···O hydrogen bonds into tapes along the y-direction. The O—H bond is significantly elongated, to 1.07 (3)Å due to the formation of the hydrogen bond (cf. Fig. 2 b). The tapes are connected by relatively strong inter-tape C—H···O hydrogen bonds into the layers (Fig. 3). Some additional C—H···O interactions (Table 1) also play a role in the building of the crystal structure.For related structures, see: Büyükgüngör et al. (2007); Odabaşoğlu et al. (2007); Yathirajan et al. (2007). For biological applications, see Hodnett & Dunn (1970); Misra et al. (1981); Agarwal et al. (1983); Varma et al. (1986); Singh & Dash (1988).
For related literature, see: Allen (2002); Farrugia (1999).
Data collection: CrysAlis CCD (Oxford Diffraction, 2006); cell
CrysAlis RED (Oxford Diffraction, 2006); data reduction: CrysAlis RED (Oxford Diffraction, 2006); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP (Siemens, 1989); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997).Fig. 1. Anisotropic displacement ellipsoids representation (50% probability level) of the molecule with the atom labelling scheme, iIntramolecular hydrogen bond is depicted in dashed line. | |
Fig. 2. Difference Fourier map slices calculated for a model without the hydrogen atoms involved in intramolecular hydrogen bonds: (a) H7, (b) H1A2 (Farrugia, 1999). Solid lines: positive values, dashed: negative; contour level: 0.04 e\%A^-3^. | |
Fig. 3. The hydrogen-bonded layer as seen approximately along the c axis. Symmetry codes: (i) x,y,z (ii) x,-1 + y,z (iii) x,1 + y,z (iv) 5/2 - x,1/2 + y,5/2 - z (v) 5/2 - x,-1/2 + y,5/2 - z. |
C18H20N2O3 | F(000) = 664 |
Mr = 312.36 | Dx = 1.314 Mg m−3 |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2yn | Cell parameters from 5056 reflections |
a = 9.0904 (13) Å | θ = 3–24° |
b = 9.8993 (9) Å | µ = 0.09 mm−1 |
c = 17.8208 (19) Å | T = 295 K |
β = 100.068 (2)° | Block, purple |
V = 1579.0 (3) Å3 | 0.3 × 0.2 × 0.2 mm |
Z = 4 |
KUMA KM4CCD four-circle diffractometer | 2464 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.020 |
Graphite monochromator | θmax = 28.0°, θmin = 2.4° |
Detector resolution: 8.1929 pixels mm-1 | h = −11→11 |
ω scan | k = −12→12 |
12993 measured reflections | l = −23→21 |
3514 independent reflections |
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)] = 0.041 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.124 | w = 1/[σ2(Fo2) + (0.063P)2 + 0.4649P] where P = (Fo2 + 2Fc2)/3 |
S = 0.98 | (Δ/σ)max = 0.003 |
3514 reflections | Δρmax = 0.25 e Å−3 |
283 parameters | Δρmin = −0.17 e Å−3 |
0 restraints | Extinction correction: SHELXL, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0026 (8) |
C18H20N2O3 | V = 1579.0 (3) Å3 |
Mr = 312.36 | Z = 4 |
Monoclinic, P21/n | Mo Kα radiation |
a = 9.0904 (13) Å | µ = 0.09 mm−1 |
b = 9.8993 (9) Å | T = 295 K |
c = 17.8208 (19) Å | 0.3 × 0.2 × 0.2 mm |
β = 100.068 (2)° |
KUMA KM4CCD four-circle diffractometer | 2464 reflections with I > 2σ(I) |
12993 measured reflections | Rint = 0.020 |
3514 independent reflections |
R[F2 > 2σ(F2)] = 0.041 | 0 restraints |
wR(F2) = 0.124 | H atoms treated by a mixture of independent and constrained refinement |
S = 0.98 | Δρmax = 0.25 e Å−3 |
3514 reflections | Δρmin = −0.17 e Å−3 |
283 parameters |
x | y | z | Uiso*/Ueq | ||
C1 | 1.03151 (16) | 0.06899 (14) | 1.12525 (8) | 0.0326 (3) | |
C1A | 1.00497 (17) | −0.07858 (14) | 1.10991 (8) | 0.0353 (3) | |
O1A1 | 1.09883 (14) | −0.16365 (11) | 1.13287 (7) | 0.0535 (3) | |
O1A2 | 0.87299 (13) | −0.10532 (11) | 1.07198 (7) | 0.0509 (3) | |
H1A2 | 0.850 (3) | −0.211 (3) | 1.0667 (14) | 0.098 (8)* | |
C2 | 0.94453 (17) | 0.16506 (14) | 1.08096 (8) | 0.0330 (3) | |
H2 | 0.8663 (17) | 0.1354 (16) | 1.0377 (9) | 0.035 (4)* | |
C3 | 0.96859 (17) | 0.30147 (14) | 1.09759 (8) | 0.0347 (3) | |
C4 | 1.07595 (18) | 0.34076 (15) | 1.15860 (9) | 0.0401 (4) | |
H4 | 1.0907 (18) | 0.4382 (18) | 1.1696 (9) | 0.043 (4)* | |
C5 | 1.16149 (19) | 0.24488 (17) | 1.20297 (9) | 0.0432 (4) | |
H5 | 1.234 (2) | 0.2745 (18) | 1.2469 (10) | 0.050 (5)* | |
C6 | 1.14098 (17) | 0.10890 (16) | 1.18570 (9) | 0.0388 (3) | |
H6 | 1.2029 (19) | 0.0408 (19) | 1.2189 (10) | 0.048 (5)* | |
N7 | 0.88185 (16) | 0.40373 (12) | 1.05574 (7) | 0.0401 (3) | |
H7 | 0.887 (2) | 0.489 (2) | 1.0747 (11) | 0.065 (6)* | |
C8 | 0.78879 (19) | 0.39282 (15) | 0.99049 (9) | 0.0411 (4) | |
H8 | 0.7807 (19) | 0.3078 (19) | 0.9646 (10) | 0.051 (5)* | |
C9 | 0.70296 (19) | 0.49992 (14) | 0.95604 (9) | 0.0398 (4) | |
C10 | 0.71045 (18) | 0.63293 (14) | 0.99024 (8) | 0.0372 (3) | |
O10 | 0.80433 (15) | 0.65435 (10) | 1.05372 (6) | 0.0485 (3) | |
C11 | 0.62075 (19) | 0.73538 (15) | 0.95329 (9) | 0.0392 (4) | |
H11 | 0.6353 (18) | 0.8253 (17) | 0.9767 (9) | 0.041 (4)* | |
C12 | 0.53163 (17) | 0.71697 (15) | 0.88196 (9) | 0.0388 (4) | |
C13 | 0.5272 (2) | 0.58514 (17) | 0.84767 (10) | 0.0482 (4) | |
H13 | 0.466 (2) | 0.5678 (18) | 0.7969 (11) | 0.054 (5)* | |
C14 | 0.6085 (2) | 0.48282 (16) | 0.88451 (10) | 0.0482 (4) | |
H14 | 0.602 (2) | 0.392 (2) | 0.8607 (10) | 0.059 (5)* | |
N15 | 0.45111 (16) | 0.82021 (13) | 0.84509 (8) | 0.0449 (3) | |
C16 | 0.3912 (2) | 0.8173 (2) | 0.76261 (10) | 0.0495 (4) | |
H16A | 0.457 (2) | 0.7599 (18) | 0.7356 (10) | 0.054 (4)* | |
H16B | 0.394 (2) | 0.908 (2) | 0.7398 (10) | 0.054 (4)* | |
C17 | 0.2318 (2) | 0.7704 (3) | 0.74366 (13) | 0.0670 (6) | |
H17A | 0.228 (3) | 0.675 (3) | 0.7658 (15) | 0.098 (5)* | |
H17B | 0.200 (3) | 0.773 (3) | 0.6867 (16) | 0.098 (5)* | |
H17C | 0.161 (3) | 0.833 (3) | 0.7715 (15) | 0.098 (5)* | |
C18 | 0.4280 (2) | 0.94628 (17) | 0.88460 (10) | 0.0442 (4) | |
H18A | 0.4192 (18) | 0.9237 (17) | 0.9378 (10) | 0.045 (3)* | |
H18B | 0.334 (2) | 0.9777 (17) | 0.8604 (10) | 0.045 (3)* | |
C19 | 0.5467 (2) | 1.05246 (19) | 0.88190 (13) | 0.0552 (5) | |
H19A | 0.647 (2) | 1.021 (2) | 0.9066 (12) | 0.071 (4)* | |
H19B | 0.523 (2) | 1.138 (2) | 0.9093 (12) | 0.071 (4)* | |
H19C | 0.549 (2) | 1.075 (2) | 0.8283 (13) | 0.071 (4)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0348 (8) | 0.0296 (7) | 0.0333 (7) | 0.0018 (6) | 0.0059 (6) | 0.0005 (6) |
C1A | 0.0403 (8) | 0.0294 (7) | 0.0354 (7) | 0.0035 (6) | 0.0047 (6) | 0.0014 (6) |
O1A1 | 0.0530 (7) | 0.0334 (6) | 0.0680 (8) | 0.0117 (5) | −0.0068 (6) | 0.0036 (5) |
O1A2 | 0.0482 (7) | 0.0247 (6) | 0.0722 (8) | 0.0033 (5) | −0.0105 (6) | −0.0060 (5) |
C2 | 0.0366 (8) | 0.0272 (7) | 0.0338 (7) | −0.0008 (6) | 0.0021 (6) | −0.0013 (5) |
C3 | 0.0417 (8) | 0.0271 (7) | 0.0361 (7) | −0.0003 (6) | 0.0090 (6) | 0.0001 (6) |
C4 | 0.0453 (9) | 0.0298 (8) | 0.0445 (9) | −0.0059 (6) | 0.0061 (7) | −0.0067 (6) |
C5 | 0.0408 (9) | 0.0453 (9) | 0.0410 (9) | −0.0053 (7) | 0.0001 (7) | −0.0081 (7) |
C6 | 0.0365 (8) | 0.0386 (8) | 0.0395 (8) | 0.0031 (7) | 0.0017 (6) | 0.0005 (6) |
N7 | 0.0538 (8) | 0.0219 (6) | 0.0418 (7) | 0.0012 (6) | 0.0009 (6) | 0.0000 (5) |
C8 | 0.0562 (10) | 0.0224 (7) | 0.0436 (8) | −0.0012 (7) | 0.0053 (7) | −0.0022 (6) |
C9 | 0.0525 (9) | 0.0240 (7) | 0.0405 (8) | −0.0010 (7) | 0.0020 (7) | −0.0010 (6) |
C10 | 0.0470 (9) | 0.0256 (7) | 0.0371 (8) | −0.0022 (6) | 0.0022 (7) | −0.0021 (6) |
O10 | 0.0707 (8) | 0.0234 (5) | 0.0433 (6) | 0.0011 (5) | −0.0131 (6) | −0.0034 (4) |
C11 | 0.0502 (9) | 0.0243 (7) | 0.0407 (8) | 0.0022 (6) | 0.0009 (7) | −0.0047 (6) |
C12 | 0.0407 (9) | 0.0317 (7) | 0.0423 (8) | 0.0012 (6) | 0.0021 (7) | −0.0018 (6) |
C13 | 0.0555 (11) | 0.0379 (9) | 0.0449 (9) | −0.0005 (8) | −0.0087 (8) | −0.0082 (7) |
C14 | 0.0636 (11) | 0.0276 (8) | 0.0489 (9) | −0.0003 (7) | −0.0026 (8) | −0.0076 (7) |
N15 | 0.0495 (8) | 0.0375 (7) | 0.0436 (7) | 0.0080 (6) | −0.0031 (6) | −0.0014 (6) |
C16 | 0.0528 (11) | 0.0497 (10) | 0.0452 (9) | 0.0063 (8) | 0.0059 (8) | 0.0031 (8) |
C17 | 0.0530 (12) | 0.0885 (17) | 0.0554 (12) | 0.0000 (11) | −0.0018 (10) | −0.0032 (11) |
C18 | 0.0447 (10) | 0.0390 (8) | 0.0480 (9) | 0.0116 (7) | 0.0058 (8) | 0.0012 (7) |
C19 | 0.0618 (12) | 0.0410 (10) | 0.0636 (12) | 0.0016 (9) | 0.0128 (10) | −0.0003 (9) |
C1—C6 | 1.390 (2) | C10—C11 | 1.393 (2) |
C1—C2 | 1.391 (2) | C11—C12 | 1.395 (2) |
C1—C1A | 1.498 (2) | C11—H11 | 0.982 (17) |
C1A—O1A1 | 1.2177 (18) | C12—N15 | 1.3578 (19) |
C1A—O1A2 | 1.2972 (19) | C12—C13 | 1.439 (2) |
O1A2—H1A2 | 1.07 (3) | C13—C14 | 1.354 (2) |
C2—C3 | 1.392 (2) | C13—H13 | 0.991 (18) |
C2—H2 | 0.998 (16) | C14—H14 | 1.00 (2) |
C3—C4 | 1.384 (2) | N15—C18 | 1.466 (2) |
C3—N7 | 1.4132 (19) | N15—C16 | 1.476 (2) |
C4—C5 | 1.384 (2) | C16—C17 | 1.503 (3) |
C4—H4 | 0.989 (17) | C16—H16A | 1.004 (19) |
C5—C6 | 1.386 (2) | C16—H16B | 0.990 (19) |
C5—H5 | 0.975 (18) | C17—H17A | 1.03 (3) |
C6—H6 | 1.002 (18) | C17—H17B | 1.01 (3) |
N7—C8 | 1.317 (2) | C17—H17C | 1.07 (3) |
N7—H7 | 0.91 (2) | C18—C19 | 1.513 (3) |
C8—C9 | 1.394 (2) | C18—H18A | 0.990 (18) |
C8—H8 | 0.956 (19) | C18—H18B | 0.942 (18) |
C9—C14 | 1.417 (2) | C19—H19A | 0.99 (2) |
C9—C10 | 1.448 (2) | C19—H19B | 1.02 (2) |
C10—O10 | 1.3097 (18) | C19—H19C | 0.99 (2) |
C6—C1—C2 | 120.30 (13) | N15—C12—C11 | 121.38 (14) |
C6—C1—C1A | 119.30 (13) | N15—C12—C13 | 120.31 (14) |
C2—C1—C1A | 120.38 (13) | C11—C12—C13 | 118.31 (14) |
O1A1—C1A—O1A2 | 124.32 (14) | C14—C13—C12 | 120.03 (15) |
O1A1—C1A—C1 | 122.15 (14) | C14—C13—H13 | 119.0 (11) |
O1A2—C1A—C1 | 113.51 (13) | C12—C13—H13 | 120.9 (11) |
C1A—O1A2—H1A2 | 113.4 (13) | C13—C14—C9 | 122.70 (15) |
C1—C2—C3 | 119.34 (14) | C13—C14—H14 | 119.1 (11) |
C1—C2—H2 | 119.7 (9) | C9—C14—H14 | 118.2 (11) |
C3—C2—H2 | 121.0 (9) | C12—N15—C18 | 121.24 (13) |
C4—C3—C2 | 120.21 (14) | C12—N15—C16 | 122.74 (14) |
C4—C3—N7 | 117.72 (13) | C18—N15—C16 | 115.87 (13) |
C2—C3—N7 | 122.02 (14) | N15—C16—C17 | 113.77 (16) |
C3—C4—C5 | 120.31 (14) | N15—C16—H16A | 110.0 (10) |
C3—C4—H4 | 118.8 (9) | C17—C16—H16A | 110.3 (10) |
C5—C4—H4 | 120.8 (10) | N15—C16—H16B | 111.0 (11) |
C4—C5—C6 | 119.92 (15) | C17—C16—H16B | 106.3 (11) |
C4—C5—H5 | 119.0 (11) | H16A—C16—H16B | 105.0 (15) |
C6—C5—H5 | 121.0 (11) | C16—C17—H17A | 106.9 (15) |
C5—C6—C1 | 119.89 (15) | C16—C17—H17B | 108.2 (15) |
C5—C6—H6 | 118.8 (10) | H17A—C17—H17B | 113 (2) |
C1—C6—H6 | 121.2 (10) | C16—C17—H17C | 110.5 (14) |
C8—N7—C3 | 128.32 (13) | H17A—C17—H17C | 107 (2) |
C8—N7—H7 | 113.0 (13) | H17B—C17—H17C | 112 (2) |
C3—N7—H7 | 118.7 (13) | N15—C18—C19 | 114.44 (15) |
N7—C8—C9 | 123.38 (14) | N15—C18—H18A | 108.1 (10) |
N7—C8—H8 | 118.8 (11) | C19—C18—H18A | 111.4 (10) |
C9—C8—H8 | 117.8 (11) | N15—C18—H18B | 104.8 (11) |
C8—C9—C14 | 120.66 (14) | C19—C18—H18B | 110.6 (11) |
C8—C9—C10 | 121.66 (14) | H18A—C18—H18B | 107.1 (14) |
C14—C9—C10 | 117.65 (14) | C18—C19—H19A | 111.7 (13) |
O10—C10—C11 | 121.99 (13) | C18—C19—H19B | 110.3 (12) |
O10—C10—C9 | 119.11 (13) | H19A—C19—H19B | 107.8 (18) |
C11—C10—C9 | 118.86 (14) | C18—C19—H19C | 109.2 (13) |
C10—C11—C12 | 122.32 (13) | H19A—C19—H19C | 109.2 (17) |
C10—C11—H11 | 115.8 (10) | H19B—C19—H19C | 108.5 (17) |
C12—C11—H11 | 121.3 (9) | ||
C6—C1—C1A—O1A1 | −21.1 (2) | C14—C9—C10—O10 | −175.35 (15) |
C2—C1—C1A—O1A1 | 160.84 (14) | C8—C9—C10—C11 | −179.40 (15) |
C6—C1—C1A—O1A2 | 157.39 (14) | C14—C9—C10—C11 | 2.7 (2) |
C2—C1—C1A—O1A2 | −20.7 (2) | O10—C10—C11—C12 | 173.43 (15) |
C6—C1—C2—C3 | 0.2 (2) | C9—C10—C11—C12 | −4.5 (2) |
C1A—C1—C2—C3 | 178.28 (13) | C10—C11—C12—N15 | −176.43 (16) |
C1—C2—C3—C4 | −1.3 (2) | C10—C11—C12—C13 | 3.3 (3) |
C1—C2—C3—N7 | −178.63 (13) | N15—C12—C13—C14 | 179.57 (17) |
C2—C3—C4—C5 | 0.8 (2) | C11—C12—C13—C14 | −0.1 (3) |
N7—C3—C4—C5 | 178.23 (14) | C12—C13—C14—C9 | −1.6 (3) |
C3—C4—C5—C6 | 0.8 (2) | C8—C9—C14—C13 | −177.61 (18) |
C4—C5—C6—C1 | −1.9 (2) | C10—C9—C14—C13 | 0.3 (3) |
C2—C1—C6—C5 | 1.4 (2) | C11—C12—N15—C18 | −13.4 (2) |
C1A—C1—C6—C5 | −176.68 (14) | C13—C12—N15—C18 | 166.90 (16) |
C4—C3—N7—C8 | 170.02 (16) | C11—C12—N15—C16 | 162.02 (16) |
C2—C3—N7—C8 | −12.6 (3) | C13—C12—N15—C16 | −17.7 (3) |
C3—N7—C8—C9 | 176.68 (15) | C12—N15—C16—C17 | 95.6 (2) |
N7—C8—C9—C14 | 177.89 (16) | C18—N15—C16—C17 | −88.7 (2) |
N7—C8—C9—C10 | 0.0 (3) | C12—N15—C18—C19 | 89.8 (2) |
C8—C9—C10—O10 | 2.6 (2) | C16—N15—C18—C19 | −86.0 (2) |
D—H···A | D—H | H···A | D···A | D—H···A |
N7—H7···O10 | 0.91 (2) | 1.81 (2) | 2.578 (2) | 140 (2) |
O1A2—H1A2···O10i | 1.07 (3) | 1.40 (3) | 2.467 (1) | 173 (2) |
C5—H5···O1A1ii | 0.98 (2) | 2.48 (2) | 3.449 (2) | 174 (2) |
C8—H8···O1A1iii | 0.96 (2) | 2.63 (2) | 3.436 (2) | 142 (1) |
C11—H11···O1A2iv | 0.98 (2) | 2.60 (2) | 3.244 (2) | 124 (1) |
C16—H16A···O1A1v | 1.00 (2) | 2.60 (2) | 3.570 (2) | 163 (1) |
Symmetry codes: (i) x, y−1, z; (ii) −x+5/2, y+1/2, −z+5/2; (iii) −x+2, −y, −z+2; (iv) x, y+1, z; (v) x−1/2, −y+1/2, z−1/2. |
Experimental details
Crystal data | |
Chemical formula | C18H20N2O3 |
Mr | 312.36 |
Crystal system, space group | Monoclinic, P21/n |
Temperature (K) | 295 |
a, b, c (Å) | 9.0904 (13), 9.8993 (9), 17.8208 (19) |
β (°) | 100.068 (2) |
V (Å3) | 1579.0 (3) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.09 |
Crystal size (mm) | 0.3 × 0.2 × 0.2 |
Data collection | |
Diffractometer | KUMA KM4CCD four-circle diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 12993, 3514, 2464 |
Rint | 0.020 |
(sin θ/λ)max (Å−1) | 0.661 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.041, 0.124, 0.98 |
No. of reflections | 3514 |
No. of parameters | 283 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.25, −0.17 |
Computer programs: CrysAlis CCD (Oxford Diffraction, 2006), CrysAlis RED (Oxford Diffraction, 2006), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), XP (Siemens, 1989).
D—H···A | D—H | H···A | D···A | D—H···A |
N7—H7···O10 | 0.91 (2) | 1.81 (2) | 2.578 (2) | 140 (2) |
O1A2—H1A2···O10i | 1.07 (3) | 1.40 (3) | 2.467 (1) | 173 (2) |
C5—H5···O1A1ii | 0.98 (2) | 2.48 (2) | 3.449 (2) | 174 (2) |
C8—H8···O1A1iii | 0.96 (2) | 2.63 (2) | 3.436 (2) | 142 (1) |
C11—H11···O1A2iv | 0.98 (2) | 2.60 (2) | 3.244 (2) | 124 (1) |
C16—H16A···O1A1v | 1.00 (2) | 2.60 (2) | 3.570 (2) | 163 (1) |
Symmetry codes: (i) x, y−1, z; (ii) −x+5/2, y+1/2, −z+5/2; (iii) −x+2, −y, −z+2; (iv) x, y+1, z; (v) x−1/2, −y+1/2, z−1/2. |
Acknowledgements
MTS thanks Sambhram Institute of Technology for the research facilities.
References
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This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.
Schiff bases are used as substrates in the preparation of number of industrial and biologically active compounds via ring closure, cycloaddition and replacement reactions. Some Schiff base derivatives were reported to possess antimicrobial, anti-inflammatory and central nervous system activities. Moreover, Schiff bases are also known to have biological activities such as antimicrobial, antifungal, antitumor and as herbicides (e.g. Hodnett et al., 1970, Singh & Dash, 1988, Varma et al., (1986)). In the course of our studies of Schiff bases (e.g. Büyükgüngör et al., 2007; Odabaşoğlu et al., 2007; Yathirajan et al., 2007), the title compound, C18H20N2O3 was synthesized and its crystal structure is reported.
The title compound crystallizes as the keto-tautomer (Fig. 1), unlike the majority of the similar compounds. In the CSD (Allen, 2002) the hydroxy tautomers were found in 218 compounds while the keto ones only in 17 compounds (Version Nov. 2006, updates up to August 2007; only organic compounds). In this case the presence of the certain tautomer is proven by the succesful location and refinement of the hydrogen atom bonded to N7 nitrogen atom (Fig. 2a). Short and relatively linear intramolecular N—H···O hydrogen bond forms an almost planar (maximum deviation 0.017 (1) Å) six-membered ring. The same O10 oxygen atom which accepts the intramolecular hydrogen bond is involved in a very short (O···O distance is 2.467 (1) Å) intermolecular O—H···O hydrogen bond. As a result the C10—O10 bond of 1.310 (2)Å is significantly longer than a typical C?O double bond. CSD search results show that such elongation is typical for similar compounds, the mean C—O distance being 1.348 (17)Å for hydroxy tautomers, but it may also be as large as 1.299 (17)Å also for the keto-tautomers. Together with the observation of bond lengths around N7 atom this implies some degree of zwitterionic character of the molecule, with partial positive charge at N7—H7 group and negative at O10 atom. These perturbations disturb also the benzene ring. The ring A (C1 - C6) is closer to planarity than the ring B (C9 - C14). Maximum deviations from the least-squares planes are 0.0103 (11)Å for ring A and 0.0219 (12)Å for ring B. Also the bond lengths and angles are much more uniform within the ring A than in ring B.
The conformation of the molecule is described by the dihedral angles between benzene ring planes of 15.05 (7)°. As a result of the intramolecular hydrogen bond, the bridging C—C?N—C group is almost coplanar with the ring B (dihedral angle 2.35 (15)°). The COO group is significantly, by 21.73 (10)°, twisted with respect to its parent ring's plane. On the other end of the molecule, the C—N—C fragment is twisted by 17.0 (2)°, while the terminal C—C bonds are almost perpendicular to the CNC plane.
In the crystal structure the molecules are connected by strong intermolecular O—H···O hydrogen bonds into tapes along the y-direction. The O—H bond is significantly elongated, to 1.07 (3)Å due to the formation of the hydrogen bond (cf. Fig. 2 b). The tapes are connected by relatively strong inter-tape C—H···O hydrogen bonds into the layers (Fig. 3). Some additional C—H···O interactions (Table 1) also play a role in the building of the crystal structure.