organic compounds
Diethyl 2-amino-5-[(E)-(furan-2-ylmethylidene)amino]thiophene-3,4-dicarboxylate
aDepartment of Chemistry, University of Montreal, CP 6128, succ. Centre-ville, Montréal, Québec, Canada H3C 3J7
*Correspondence e-mail: w.skene@umontreal.ca
In the 15H16N2O5S, the azomethine adopts the E configuration. The two heterocyclic rings adopt an antiperiplanar orientation. The mean planes of the thiophene and furan rings are twisted by 2.51 (4)°. The exhibits intermolecular N—H⋯O hydrogen bonding. π–π stacking is also observed, the centroid-to-centroid distance being 3.770 (4) Å.
of the title compound, CRelated literature
For general background, see: Dufresne & Skene (2008). For a related see: Skene et al. (2006)
Experimental
Crystal data
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Refinement
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Data collection: SMART (Bruker, 2003); cell SAINT (Bruker, 2004); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008) and ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: UdMX (Marris, 2004).
Supporting information
https://doi.org/10.1107/S1600536810043746/wn2415sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536810043746/wn2415Isup2.hkl
2-Furaldehyde (37 mg, 0.39 mmol) and 2,5-diamino-thiophene-3,4-dicarboxylic acid diethyl ester (100 mg, 0.39 mmol) were mixed in anhydrous 2-propanol with a catalytic amount of TFA and refluxed for 12 h. The reaction was then purified by flash
to afford the title compound as a brownish yellow solid (110 mg, 85%). Single crystals were obtained by slow evaporation of an acetone solution.Carbon-bound H atoms were placed in calculated positions (Cmethyl—H = 0.98 Å, Cmethylene—H = 0.99 Å and Csp2—H = 0.95 Å) and included in the
in the riding-model approximation, with Uiso(H) = kUeq(C), where k = 1.5 for Cmethyl and 1.2 for Cmethylene and Csp2. The H atoms of the amino group were placed in calculated positions (N—H = 0.88 Å) and included in the in the riding-model approximation, with Uiso(H) = 1.2Ueq(N).During the course of our ongoing conjugated azomethine research, we prepared the title compound. The X-ray crystallographic analysis not only confirmed the structure (Fig. 1), but that the energetically stable E isomer was formed. Neither solvent nor counter-ions were found in the structure.
The heterocyclic rings were found not to be coplanar; the angle between the heterocyclic mean planes is 2.51 (4)°. This angle is less than that in a previously reported azomethine thiophene system, whose angle is 7.25 (11)° (Skene et al., 2006).
A major point of interest is the azomethine bond. The bond lengths for N2—C4, N2—C5 and C5—C6 are 1.382 (2), 1.289 (2) and 1.420 (2) Å, respectively. These are similar to the related azomethine thiophene compound (Skene et al., 2006), whose homologous lengths are 1.381 (3), 1.283 (3) and 1.426 (3) Å.
Fig. 2 shows that two different hydrogen bonds occur in the π-stacking takes place between two different molecules, at [x, y, z] and [1 - x, -y, 1 - z]. Fig. 3 shows the interactions, with the distance between the planes being 3.440 (4) Å. The centroid···centroid distance between the two rings is 3.770 (4) Å.
viz. N1—H1A···O2iii and N1—H1B···O4ii. The D—H···A angles are 135° and 122° and distances of 2.880 (3) Å and 3.059 (3) Å were measured between the nitrogen and oxygens (Table 1). Dimerization of two molecules occurs via H-bonding between N1—H1A···O2iii. Additionally,For general background, see: Dufresne & Skene (2008). For a related
see: Skene et al. (2006)Data collection: SMART (Bruker, 2003); cell
SAINT (Bruker, 2004); data reduction: SAINT (Bruker, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008) and ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: UdMX (Marris, 2004).C15H16N2O5S | F(000) = 704 |
Mr = 336.36 | Dx = 1.461 Mg m−3 |
Monoclinic, P21/n | Melting point: 425(2) K |
Hall symbol: -P 2yn | Cu Kα radiation, λ = 1.54178 Å |
a = 9.3452 (19) Å | Cell parameters from 3360 reflections |
b = 14.635 (3) Å | θ = 5.0–38.8° |
c = 11.343 (2) Å | µ = 2.14 mm−1 |
β = 99.73 (3)° | T = 123 K |
V = 1529.0 (5) Å3 | Block, yellow |
Z = 4 | 0.14 × 0.10 × 0.04 mm |
Bruker SMART 6000 diffractometer | 3005 independent reflections |
Radiation source: rotating anode | 2475 reflections with I > 2σ(I) |
Montel 200 optics monochromator | Rint = 0.036 |
Detector resolution: 5.5 pixels mm-1 | θmax = 72.3°, θmin = 5.0° |
ω scans | h = −11→11 |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | k = −17→18 |
Tmin = 0.728, Tmax = 0.920 | l = −13→13 |
6320 measured reflections |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.037 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.102 | H-atom parameters constrained |
S = 1.03 | w = 1/[σ2(Fo2) + (0.0643P)2] where P = (Fo2 + 2Fc2)/3 |
3005 reflections | (Δ/σ)max = 0.001 |
210 parameters | Δρmax = 0.29 e Å−3 |
0 restraints | Δρmin = −0.34 e Å−3 |
C15H16N2O5S | V = 1529.0 (5) Å3 |
Mr = 336.36 | Z = 4 |
Monoclinic, P21/n | Cu Kα radiation |
a = 9.3452 (19) Å | µ = 2.14 mm−1 |
b = 14.635 (3) Å | T = 123 K |
c = 11.343 (2) Å | 0.14 × 0.10 × 0.04 mm |
β = 99.73 (3)° |
Bruker SMART 6000 diffractometer | 3005 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | 2475 reflections with I > 2σ(I) |
Tmin = 0.728, Tmax = 0.920 | Rint = 0.036 |
6320 measured reflections |
R[F2 > 2σ(F2)] = 0.037 | 0 restraints |
wR(F2) = 0.102 | H-atom parameters constrained |
S = 1.03 | Δρmax = 0.29 e Å−3 |
3005 reflections | Δρmin = −0.34 e Å−3 |
210 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. |
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 | ||
S1 | 0.15876 (5) | 0.01058 (3) | 0.62132 (4) | 0.02153 (13) | |
O3 | 0.26457 (13) | 0.20322 (8) | 0.97617 (10) | 0.0216 (3) | |
O5 | 0.53448 (13) | 0.16250 (8) | 0.86520 (11) | 0.0229 (3) | |
O1 | 0.53601 (14) | 0.14839 (10) | 0.36188 (11) | 0.0299 (3) | |
O4 | 0.42258 (13) | 0.28091 (8) | 0.76310 (11) | 0.0261 (3) | |
O2 | 0.11370 (14) | 0.08821 (9) | 1.00209 (11) | 0.0280 (3) | |
N2 | 0.37833 (15) | 0.11513 (10) | 0.55344 (12) | 0.0201 (3) | |
N1 | 0.01952 (16) | −0.02136 (10) | 0.80267 (14) | 0.0247 (3) | |
H1A | −0.0029 | −0.0108 | 0.8737 | 0.030* | |
H1B | −0.0274 | −0.0637 | 0.7563 | 0.030* | |
C13 | 0.42543 (18) | 0.20165 (12) | 0.79259 (14) | 0.0180 (3) | |
C2 | 0.21155 (17) | 0.09610 (11) | 0.82328 (15) | 0.0177 (3) | |
C4 | 0.29499 (18) | 0.09523 (12) | 0.63985 (15) | 0.0194 (4) | |
C10 | 0.19189 (18) | 0.12672 (12) | 0.94126 (15) | 0.0192 (4) | |
C3 | 0.30893 (17) | 0.13360 (12) | 0.75044 (14) | 0.0175 (3) | |
C14 | 0.65332 (19) | 0.22184 (13) | 0.91629 (17) | 0.0274 (4) | |
H14A | 0.6231 | 0.2619 | 0.9780 | 0.033* | |
H14B | 0.6830 | 0.2608 | 0.8533 | 0.033* | |
C1 | 0.12570 (18) | 0.02730 (12) | 0.76478 (15) | 0.0191 (4) | |
C6 | 0.42538 (19) | 0.08612 (12) | 0.35493 (16) | 0.0218 (4) | |
C5 | 0.35120 (19) | 0.07232 (12) | 0.45285 (15) | 0.0225 (4) | |
H5 | 0.2757 | 0.0281 | 0.4435 | 0.027* | |
C11 | 0.2356 (2) | 0.24369 (13) | 1.08714 (15) | 0.0259 (4) | |
H11A | 0.2526 | 0.1984 | 1.1528 | 0.031* | |
H11B | 0.1335 | 0.2646 | 1.0776 | 0.031* | |
C8 | 0.5077 (2) | 0.08255 (14) | 0.18213 (16) | 0.0284 (4) | |
H8 | 0.5204 | 0.0675 | 0.1031 | 0.034* | |
C7 | 0.4049 (2) | 0.04441 (13) | 0.24649 (16) | 0.0272 (4) | |
H7 | 0.3351 | −0.0014 | 0.2191 | 0.033* | |
C9 | 0.5836 (2) | 0.14410 (15) | 0.25473 (17) | 0.0316 (5) | |
H9 | 0.6604 | 0.1800 | 0.2343 | 0.038* | |
C15 | 0.7766 (2) | 0.16205 (14) | 0.97085 (18) | 0.0320 (4) | |
H15A | 0.7455 | 0.1231 | 1.0321 | 0.048* | |
H15B | 0.8583 | 0.2002 | 1.0075 | 0.048* | |
H15C | 0.8068 | 0.1237 | 0.9087 | 0.048* | |
C12 | 0.3367 (2) | 0.32281 (13) | 1.11445 (17) | 0.0351 (5) | |
H12A | 0.4372 | 0.3007 | 1.1284 | 0.053* | |
H12B | 0.3167 | 0.3543 | 1.1862 | 0.053* | |
H12C | 0.3227 | 0.3653 | 1.0467 | 0.053* |
U11 | U22 | U33 | U12 | U13 | U23 | |
S1 | 0.0226 (2) | 0.0245 (2) | 0.0170 (2) | −0.00387 (17) | 0.00208 (16) | −0.00373 (16) |
O3 | 0.0288 (7) | 0.0215 (6) | 0.0158 (6) | −0.0027 (5) | 0.0072 (5) | −0.0041 (5) |
O5 | 0.0206 (6) | 0.0213 (6) | 0.0245 (7) | −0.0023 (5) | −0.0025 (5) | −0.0003 (5) |
O1 | 0.0275 (7) | 0.0373 (8) | 0.0254 (7) | −0.0063 (6) | 0.0062 (6) | −0.0053 (6) |
O4 | 0.0286 (7) | 0.0206 (7) | 0.0278 (7) | −0.0032 (5) | 0.0013 (5) | 0.0036 (5) |
O2 | 0.0310 (7) | 0.0308 (7) | 0.0253 (7) | −0.0070 (6) | 0.0134 (6) | −0.0019 (6) |
N2 | 0.0221 (7) | 0.0234 (8) | 0.0148 (7) | 0.0023 (6) | 0.0036 (6) | 0.0009 (6) |
N1 | 0.0242 (8) | 0.0269 (8) | 0.0239 (8) | −0.0083 (6) | 0.0069 (6) | −0.0038 (6) |
C13 | 0.0205 (8) | 0.0216 (9) | 0.0131 (8) | 0.0010 (6) | 0.0060 (6) | −0.0011 (6) |
C2 | 0.0171 (8) | 0.0183 (8) | 0.0175 (8) | 0.0003 (6) | 0.0028 (6) | 0.0004 (6) |
C4 | 0.0191 (8) | 0.0222 (9) | 0.0170 (8) | 0.0003 (7) | 0.0032 (7) | 0.0008 (7) |
C10 | 0.0178 (8) | 0.0213 (9) | 0.0184 (8) | 0.0015 (6) | 0.0025 (7) | 0.0006 (7) |
C3 | 0.0174 (8) | 0.0184 (8) | 0.0168 (8) | 0.0013 (6) | 0.0032 (6) | 0.0017 (6) |
C14 | 0.0222 (9) | 0.0273 (10) | 0.0309 (10) | −0.0057 (7) | −0.0011 (8) | −0.0059 (8) |
C1 | 0.0181 (8) | 0.0200 (8) | 0.0185 (8) | 0.0023 (6) | 0.0013 (7) | 0.0006 (7) |
C6 | 0.0235 (8) | 0.0226 (9) | 0.0188 (8) | 0.0000 (7) | 0.0022 (7) | 0.0008 (7) |
C5 | 0.0267 (9) | 0.0222 (9) | 0.0188 (9) | −0.0013 (7) | 0.0041 (7) | 0.0005 (7) |
C11 | 0.0380 (10) | 0.0256 (9) | 0.0154 (8) | 0.0023 (8) | 0.0080 (8) | −0.0038 (7) |
C8 | 0.0314 (10) | 0.0375 (11) | 0.0174 (9) | 0.0075 (8) | 0.0076 (8) | 0.0002 (8) |
C7 | 0.0365 (10) | 0.0259 (10) | 0.0198 (9) | −0.0008 (8) | 0.0061 (8) | −0.0038 (7) |
C9 | 0.0266 (10) | 0.0429 (12) | 0.0278 (10) | −0.0014 (8) | 0.0115 (8) | 0.0052 (9) |
C15 | 0.0236 (9) | 0.0391 (11) | 0.0303 (10) | 0.0003 (8) | −0.0043 (8) | −0.0037 (9) |
C12 | 0.0578 (14) | 0.0241 (10) | 0.0235 (10) | −0.0043 (10) | 0.0078 (9) | −0.0049 (8) |
S1—C1 | 1.7242 (18) | C14—C15 | 1.495 (3) |
S1—C4 | 1.7633 (18) | C14—H14A | 0.99 |
O3—C10 | 1.334 (2) | C14—H14B | 0.99 |
O3—C11 | 1.4573 (19) | C6—C7 | 1.357 (2) |
O5—C13 | 1.3272 (19) | C6—C5 | 1.420 (2) |
O5—C14 | 1.451 (2) | C5—H5 | 0.95 |
O1—C9 | 1.364 (2) | C11—C12 | 1.494 (3) |
O1—C6 | 1.370 (2) | C11—H11A | 0.99 |
O4—C13 | 1.206 (2) | C11—H11B | 0.99 |
O2—C10 | 1.224 (2) | C8—C9 | 1.340 (3) |
N2—C5 | 1.289 (2) | C8—C7 | 1.416 (3) |
N2—C4 | 1.382 (2) | C8—H8 | 0.95 |
N1—C1 | 1.349 (2) | C7—H7 | 0.95 |
N1—H1A | 0.88 | C9—H9 | 0.95 |
N1—H1B | 0.88 | C15—H15A | 0.98 |
C13—C3 | 1.493 (2) | C15—H15B | 0.98 |
C2—C1 | 1.385 (2) | C15—H15C | 0.98 |
C2—C3 | 1.437 (2) | C12—H12A | 0.98 |
C2—C10 | 1.452 (2) | C12—H12B | 0.98 |
C4—C3 | 1.360 (2) | C12—H12C | 0.98 |
C1—S1—C4 | 91.65 (8) | C7—C6—C5 | 129.21 (18) |
C10—O3—C11 | 115.96 (13) | O1—C6—C5 | 120.86 (16) |
C13—O5—C14 | 116.42 (14) | N2—C5—C6 | 125.07 (17) |
C9—O1—C6 | 105.92 (15) | N2—C5—H5 | 117.5 |
C5—N2—C4 | 118.38 (15) | C6—C5—H5 | 117.5 |
C1—N1—H1A | 120 | O3—C11—C12 | 106.90 (15) |
C1—N1—H1B | 120 | O3—C11—H11A | 110.3 |
H1A—N1—H1B | 120 | C12—C11—H11A | 110.3 |
O4—C13—O5 | 124.46 (16) | O3—C11—H11B | 110.3 |
O4—C13—C3 | 124.88 (16) | C12—C11—H11B | 110.3 |
O5—C13—C3 | 110.65 (14) | H11A—C11—H11B | 108.6 |
C1—C2—C3 | 111.96 (15) | C9—C8—C7 | 106.42 (17) |
C1—C2—C10 | 120.84 (15) | C9—C8—H8 | 126.8 |
C3—C2—C10 | 127.08 (15) | C7—C8—H8 | 126.8 |
C3—C4—N2 | 126.11 (16) | C6—C7—C8 | 106.60 (17) |
C3—C4—S1 | 110.77 (13) | C6—C7—H7 | 126.7 |
N2—C4—S1 | 123.06 (13) | C8—C7—H7 | 126.7 |
O2—C10—O3 | 122.79 (16) | C8—C9—O1 | 111.14 (17) |
O2—C10—C2 | 123.91 (16) | C8—C9—H9 | 124.4 |
O3—C10—C2 | 113.27 (14) | O1—C9—H9 | 124.4 |
C4—C3—C2 | 113.65 (15) | C14—C15—H15A | 109.5 |
C4—C3—C13 | 121.43 (15) | C14—C15—H15B | 109.5 |
C2—C3—C13 | 124.67 (15) | H15A—C15—H15B | 109.5 |
O5—C14—C15 | 107.41 (15) | C14—C15—H15C | 109.5 |
O5—C14—H14A | 110.2 | H15A—C15—H15C | 109.5 |
C15—C14—H14A | 110.2 | H15B—C15—H15C | 109.5 |
O5—C14—H14B | 110.2 | C11—C12—H12A | 109.5 |
C15—C14—H14B | 110.2 | C11—C12—H12B | 109.5 |
H14A—C14—H14B | 108.5 | H12A—C12—H12B | 109.5 |
N1—C1—C2 | 128.96 (16) | C11—C12—H12C | 109.5 |
N1—C1—S1 | 118.97 (13) | H12A—C12—H12C | 109.5 |
C2—C1—S1 | 111.94 (13) | H12B—C12—H12C | 109.5 |
C7—C6—O1 | 109.92 (16) | ||
C14—O5—C13—O4 | 3.5 (2) | O5—C13—C3—C4 | −101.12 (18) |
C14—O5—C13—C3 | −177.89 (14) | O4—C13—C3—C2 | −108.6 (2) |
C5—N2—C4—C3 | 179.86 (17) | O5—C13—C3—C2 | 72.8 (2) |
C5—N2—C4—S1 | 2.9 (2) | C13—O5—C14—C15 | −167.31 (15) |
C1—S1—C4—C3 | −1.07 (14) | C3—C2—C1—N1 | −177.66 (17) |
C1—S1—C4—N2 | 176.35 (15) | C10—C2—C1—N1 | −1.3 (3) |
C11—O3—C10—O2 | −5.4 (2) | C3—C2—C1—S1 | −1.82 (18) |
C11—O3—C10—C2 | 172.78 (14) | C10—C2—C1—S1 | 174.49 (12) |
C1—C2—C10—O2 | 9.1 (3) | C4—S1—C1—N1 | 177.96 (14) |
C3—C2—C10—O2 | −175.17 (17) | C4—S1—C1—C2 | 1.66 (13) |
C1—C2—C10—O3 | −169.01 (15) | C9—O1—C6—C7 | 0.0 (2) |
C3—C2—C10—O3 | 6.7 (2) | C9—O1—C6—C5 | 179.52 (17) |
N2—C4—C3—C2 | −177.09 (15) | C4—N2—C5—C6 | 178.96 (16) |
S1—C4—C3—C2 | 0.22 (19) | C7—C6—C5—N2 | 179.79 (19) |
N2—C4—C3—C13 | −2.6 (3) | O1—C6—C5—N2 | 0.3 (3) |
S1—C4—C3—C13 | 174.76 (12) | C10—O3—C11—C12 | 175.14 (15) |
C1—C2—C3—C4 | 1.0 (2) | O1—C6—C7—C8 | −0.1 (2) |
C10—C2—C3—C4 | −175.00 (16) | C5—C6—C7—C8 | −179.58 (18) |
C1—C2—C3—C13 | −173.30 (15) | C9—C8—C7—C6 | 0.2 (2) |
C10—C2—C3—C13 | 10.7 (3) | C7—C8—C9—O1 | −0.2 (2) |
O4—C13—C3—C4 | 77.5 (2) | C6—O1—C9—C8 | 0.1 (2) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1A···O2i | 0.88 | 2.20 | 2.889 (2) | 135 |
N1—H1B···O4ii | 0.88 | 2.50 | 3.059 (3) | 122 |
Symmetry codes: (i) −x, −y, −z+2; (ii) −x+1/2, y−1/2, −z+3/2. |
Experimental details
Crystal data | |
Chemical formula | C15H16N2O5S |
Mr | 336.36 |
Crystal system, space group | Monoclinic, P21/n |
Temperature (K) | 123 |
a, b, c (Å) | 9.3452 (19), 14.635 (3), 11.343 (2) |
β (°) | 99.73 (3) |
V (Å3) | 1529.0 (5) |
Z | 4 |
Radiation type | Cu Kα |
µ (mm−1) | 2.14 |
Crystal size (mm) | 0.14 × 0.10 × 0.04 |
Data collection | |
Diffractometer | Bruker SMART 6000 |
Absorption correction | Multi-scan (SADABS; Sheldrick, 1996) |
Tmin, Tmax | 0.728, 0.920 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 6320, 3005, 2475 |
Rint | 0.036 |
(sin θ/λ)max (Å−1) | 0.618 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.037, 0.102, 1.03 |
No. of reflections | 3005 |
No. of parameters | 210 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.29, −0.34 |
Computer programs: SMART (Bruker, 2003), SAINT (Bruker, 2004), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008) and ORTEP-3 (Farrugia, 1997), UdMX (Marris, 2004).
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1A···O2i | 0.88 | 2.20 | 2.889 (2) | 135 |
N1—H1B···O4ii | 0.88 | 2.50 | 3.059 (3) | 122 |
Symmetry codes: (i) −x, −y, −z+2; (ii) −x+1/2, y−1/2, −z+3/2. |
Acknowledgements
NSERC Canada is thanked for DG and RTI grants allowing this work to be performed, in addition to CFI for additional equipment funding. SD also thanks NSERC for a graduate scholarship. WGS also acknowledges both the Alexander von Humboldt Foundation and the RSC for J. W. T. Jones Travelling fellowships, allowing the completion of this manuscript.
References
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During the course of our ongoing conjugated azomethine research, we prepared the title compound. The X-ray crystallographic analysis not only confirmed the structure (Fig. 1), but that the energetically stable E isomer was formed. Neither solvent nor counter-ions were found in the structure.
The heterocyclic rings were found not to be coplanar; the angle between the heterocyclic mean planes is 2.51 (4)°. This angle is less than that in a previously reported azomethine thiophene system, whose angle is 7.25 (11)° (Skene et al., 2006).
A major point of interest is the azomethine bond. The bond lengths for N2—C4, N2—C5 and C5—C6 are 1.382 (2), 1.289 (2) and 1.420 (2) Å, respectively. These are similar to the related azomethine thiophene compound (Skene et al., 2006), whose homologous lengths are 1.381 (3), 1.283 (3) and 1.426 (3) Å.
Fig. 2 shows that two different hydrogen bonds occur in the crystal structure, viz. N1—H1A···O2iii and N1—H1B···O4ii. The D—H···A angles are 135° and 122° and distances of 2.880 (3) Å and 3.059 (3) Å were measured between the nitrogen and oxygens (Table 1). Dimerization of two molecules occurs via H-bonding between N1—H1A···O2iii. Additionally, π-stacking takes place between two different molecules, at [x, y, z] and [1 - x, -y, 1 - z]. Fig. 3 shows the interactions, with the distance between the planes being 3.440 (4) Å. The centroid···centroid distance between the two rings is 3.770 (4) Å.