Acta Cryst. (2008). E64, o581 [ doi:10.1107/S160053680800367X ]
The title compound, C18H16N2O2, is a precusor for the synthesis of polyimides. The molecule is located on a crystallographic inversion center and the terminal aminophenoxy rings are almost perpendicular to the central benzene ring with a dihedral angle of 85.40 (4)°. The molecular conformation is stabilized by N-H
O and N-HN intermolecular hydrogen-bonding interactions.
The title compound was synthesized in two steps. In the first step a mixture of 2.00 g (0.0180 mol) of hydroquinone, 5.00 g (0.0360 mol) of anhydrous K2CO3 and 3.81 ml (0.036 mol) of 4-fluoronitrobenzene in a two neck round bottom flask having 70 ml of dimethyl acetamide was heated at 373 K for 20 h under a nitrogen atmosphere. The colour of the solution changes from yellow to dark brown as the reaction proceeds. After cooling to room temperature, the reaction mixture was poured in 800 ml of water to precipitate a yellow solid which was washed thoroughly with water and then separated by filtration. In the second step a 250 ml two neck flask was charged with 1.00 g (2.84 mmol) of the yellow solid, 10 ml of hydrazine monohydrate, 80 ml of ethanol and 0.06 g of 5% palladium on carbon (Pd/C). The mixture was refluxed for 16 h and then filtered to remove Pd/C. The solvent was evaporated and the resulting crude solid was recrystallized from ethanol to afford crystals suitable for X-ray analysis (yield:85%, m.p.: 455 K).
All hydrogen atoms were located from the difference Fourier map and refined isotropically.
Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT (Bruker, 2001); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008), WinGX (Farrugia, 1999) and Mercury (Macrae et al., 2006).
![[Figure 1]](./zl2055fig1thm.gif)
| Fig. 1. The molecular structure of the compound, with atom labels and 50% probability displacement ellipsoids for non-H atoms. The non-labled atoms have the symmetry operator (-x,-y + 1,-z + 1). |
![[Figure 2]](./zl2055fig2thm.gif)
| Fig. 2. The packing of the compound, viewed down the c axis, showing the zig zag packing pattern. |
![[Figure 3]](./zl2055fig3thm.gif)
| Fig. 3. Hydrogen bonding and part of the C—H···π interactions in the title compound. |
| C18H16N2O2 | F000 = 308 |
| Mr = 292.33 | Dx = 1.290 Mg m−3 |
| Monoclinic, P21/c | Mo Kα radiation λ = 0.71073 Å |
| Hall symbol: -P 2ybc | Cell parameters from 6563 reflections |
| a = 6.9579 (9) Å | θ = 1.8–28.3º |
| b = 22.664 (3) Å | µ = 0.09 mm−1 |
| c = 5.1202 (7) Å | T = 296 (2) K |
| β = 111.287 (2)º | Parallelepiped, colorless |
| V = 752.34 (17) Å3 | 0.42 × 0.40 × 0.20 mm |
| Z = 2 |
| Bruker SMART APEX area-detector diffractometer | 1805 independent reflections |
| Radiation source: normal-focus sealed tube | 1324 reflections with I > 2σ(I) |
| Monochromator: graphite | Rint = 0.016 |
| T = 296(2) K | θmax = 28.3º |
| ω scans | θmin = 1.8º |
| Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | h = −9→9 |
| Tmin = 0.912, Tmax = 0.983 | k = −29→29 |
| 6563 measured reflections | l = −6→6 |
| 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)] = 0.039 | H atoms treated by a mixture of independent and constrained refinement |
| wR(F2) = 0.110 | w = 1/[σ2(Fo2) + (0.0514P)2 + 0.0611P] where P = (Fo2 + 2Fc2)/3 |
| S = 1.03 | (Δ/σ)max = 0.001 |
| 1805 reflections | Δρmax = 0.11 e Å−3 |
| 132 parameters | Δρmin = −0.17 e Å−3 |
| Primary atom site location: structure-invariant direct methods | Extinction correction: none |
| C18H16N2O2 | V = 752.34 (17) Å3 |
| Mr = 292.33 | Z = 2 |
| Monoclinic, P21/c | Mo Kα |
| a = 6.9579 (9) Å | µ = 0.09 mm−1 |
| b = 22.664 (3) Å | T = 296 (2) K |
| c = 5.1202 (7) Å | 0.42 × 0.40 × 0.20 mm |
| β = 111.287 (2)º |
| Bruker SMART APEX area-detector diffractometer | 1805 independent reflections |
| Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | 1324 reflections with I > 2σ(I) |
| Tmin = 0.912, Tmax = 0.983 | Rint = 0.016 |
| 6563 measured reflections |
| R[F2 > 2σ(F2)] = 0.039 | 132 parameters |
| wR(F2) = 0.110 | H atoms treated by a mixture of independent and constrained refinement |
| S = 1.03 | Δρmax = 0.11 e Å−3 |
| 1805 reflections | Δρmin = −0.17 e Å−3 |
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 | ||
| C1 | 0.70301 (18) | 0.32300 (5) | 0.8436 (3) | 0.0594 (3) | |
| C2 | 0.7083 (2) | 0.36502 (6) | 1.0429 (3) | 0.0682 (4) | |
| C3 | 0.5311 (2) | 0.39239 (6) | 1.0395 (3) | 0.0689 (4) | |
| C4 | 0.3455 (2) | 0.37764 (5) | 0.8382 (3) | 0.0624 (3) | |
| C5 | 0.3356 (2) | 0.33551 (6) | 0.6415 (3) | 0.0701 (4) | |
| C6 | 0.5135 (2) | 0.30869 (6) | 0.6426 (3) | 0.0679 (4) | |
| C7 | 0.08726 (18) | 0.45198 (5) | 0.6667 (2) | 0.0575 (3) | |
| C8 | 0.1848 (2) | 0.47745 (6) | 0.5030 (3) | 0.0627 (3) | |
| C9 | −0.0966 (2) | 0.47461 (6) | 0.6631 (3) | 0.0623 (3) | |
| N1 | 0.8832 (2) | 0.29346 (6) | 0.8572 (3) | 0.0754 (4) | |
| O1 | 0.16450 (15) | 0.40403 (4) | 0.8428 (2) | 0.0768 (3) | |
| H1A | 0.992 (2) | 0.3169 (8) | 0.917 (3) | 0.087 (5)* | |
| H2A | 0.871 (2) | 0.2739 (8) | 0.692 (4) | 0.090 (5)* | |
| H2 | 0.837 (2) | 0.3742 (7) | 1.188 (3) | 0.083 (4)* | |
| H3 | 0.536 (2) | 0.4215 (7) | 1.172 (3) | 0.081 (4)* | |
| H5 | 0.210 (2) | 0.3248 (7) | 0.503 (3) | 0.091 (5)* | |
| H6 | 0.506 (2) | 0.2798 (7) | 0.504 (3) | 0.081 (4)* | |
| H8 | 0.311 (2) | 0.4623 (6) | 0.505 (3) | 0.076 (4)* | |
| H9 | −0.1617 (18) | 0.4570 (6) | 0.778 (3) | 0.072 (4)* |
| U11 | U22 | U33 | U12 | U13 | U23 | |
| C1 | 0.0652 (7) | 0.0540 (6) | 0.0638 (7) | −0.0033 (5) | 0.0290 (6) | 0.0066 (5) |
| C2 | 0.0649 (8) | 0.0724 (8) | 0.0656 (8) | −0.0120 (6) | 0.0218 (7) | −0.0073 (6) |
| C3 | 0.0792 (9) | 0.0634 (7) | 0.0692 (8) | −0.0088 (6) | 0.0329 (7) | −0.0109 (6) |
| C4 | 0.0691 (8) | 0.0560 (7) | 0.0680 (7) | 0.0028 (5) | 0.0318 (6) | 0.0093 (5) |
| C5 | 0.0670 (8) | 0.0707 (8) | 0.0645 (8) | −0.0007 (6) | 0.0142 (6) | −0.0013 (6) |
| C6 | 0.0771 (9) | 0.0615 (7) | 0.0640 (8) | −0.0012 (6) | 0.0244 (6) | −0.0075 (6) |
| C7 | 0.0640 (7) | 0.0510 (6) | 0.0590 (7) | −0.0040 (5) | 0.0242 (5) | −0.0042 (5) |
| C8 | 0.0612 (7) | 0.0617 (7) | 0.0716 (8) | −0.0002 (6) | 0.0317 (6) | −0.0022 (6) |
| C9 | 0.0661 (7) | 0.0610 (7) | 0.0680 (7) | −0.0056 (6) | 0.0342 (6) | −0.0008 (6) |
| N1 | 0.0687 (8) | 0.0761 (8) | 0.0871 (9) | −0.0012 (6) | 0.0351 (7) | −0.0007 (6) |
| O1 | 0.0797 (6) | 0.0731 (6) | 0.0908 (7) | 0.0131 (5) | 0.0469 (5) | 0.0202 (5) |
| C1—C6 | 1.3847 (19) | C6—H6 | 0.953 (16) |
| C1—C2 | 1.3865 (18) | C7—C9 | 1.3722 (17) |
| C1—N1 | 1.4009 (17) | C7—C8 | 1.3819 (17) |
| C2—C3 | 1.3746 (19) | C7—O1 | 1.3897 (15) |
| C2—H2 | 0.956 (15) | C8—C9i | 1.3789 (18) |
| C3—C4 | 1.3695 (19) | C8—H8 | 0.941 (14) |
| C3—H3 | 0.939 (15) | C9—C8i | 1.3789 (18) |
| C4—C5 | 1.3717 (19) | C9—H9 | 0.950 (13) |
| C4—O1 | 1.4017 (15) | N1—H1A | 0.884 (17) |
| C5—C6 | 1.3772 (19) | N1—H2A | 0.930 (17) |
| C5—H5 | 0.935 (15) | ||
| C6—C1—C2 | 118.16 (12) | C5—C6—H6 | 119.7 (9) |
| C6—C1—N1 | 121.22 (13) | C1—C6—H6 | 119.6 (9) |
| C2—C1—N1 | 120.50 (13) | C9—C7—C8 | 119.77 (12) |
| C3—C2—C1 | 121.09 (13) | C9—C7—O1 | 116.11 (11) |
| C3—C2—H2 | 119.6 (9) | C8—C7—O1 | 124.12 (11) |
| C1—C2—H2 | 119.3 (9) | C9i—C8—C7 | 119.76 (12) |
| C4—C3—C2 | 119.75 (13) | C9i—C8—H8 | 120.0 (9) |
| C4—C3—H3 | 119.4 (9) | C7—C8—H8 | 120.2 (9) |
| C2—C3—H3 | 120.8 (9) | C7—C9—C8i | 120.46 (12) |
| C3—C4—C5 | 120.29 (13) | C7—C9—H9 | 119.1 (8) |
| C3—C4—O1 | 119.40 (12) | C8i—C9—H9 | 120.4 (8) |
| C5—C4—O1 | 120.25 (12) | C1—N1—H1A | 111.7 (10) |
| C4—C5—C6 | 119.95 (13) | C1—N1—H2A | 113.4 (10) |
| C4—C5—H5 | 121.5 (10) | H1A—N1—H2A | 112.7 (14) |
| C6—C5—H5 | 118.6 (9) | C7—O1—C4 | 117.44 (9) |
| C5—C6—C1 | 120.75 (13) | ||
| C7—O1—C4—C3 | 98.03 (15) | C7—O1—C4—C5 | −84.85 (15) |
| Symmetry codes: (i) −x, −y+1, −z+1. |
| D—H···A | D—H | H···A | D···A | D—H···A |
| N1—H2A···N1ii | 0.930 (17) | 2.321 (18) | 3.2303 (17) | 165.6 (14) |
| N1—H1A···O1iii | 0.884 (17) | 2.412 (17) | 3.1968 (17) | 148.1 (14) |
| Symmetry codes: (ii) x, −y+1/2, z−1/2; (iii) x+1, y, z. |
| D—H···A | D—H | H···A | D···A | D—H···A |
| N1—H2A···N1i | 0.930 (17) | 2.321 (18) | 3.2303 (17) | 165.6 (14) |
| N1—H1A···O1ii | 0.884 (17) | 2.412 (17) | 3.1968 (17) | 148.1 (14) |
| Symmetry codes: (i) x, −y+1/2, z−1/2; (ii) x+1, y, z. |
The Authors are grateful to the Department of Chemistry, Quaid-I-Azam University, Islamabad, Pakistan, and to the Chemistry Department, King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia, for the use of their X-ray facilities.
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Ether containing aromatic diamines are useful monomers for the preparation of soluble polyimides (Yang et al., 2002) which form a group of incredibly strong and astoundingly heat and chemical resistant polymers (Butt et al., 2005). Many efforts have been made to improve their processability while maintaining their excellent thermal and mechanical properties (Choi et al., 2001). Incorporation of flexible groups such as ether linkages were found successful in altering the crystallinity and the intermolecular interactions and to increase the solubility (Eastmond et al., 1996). Different structural modifications of the polymer backbone have been studied to reduce the chain interaction, such as the introduction of flexible links, such as –O– and CH2, to the main chain. This alteration disrupts the conjugation and increases the chain flexibility, which affects the chain packing but not the glass transition temperature (Yan et al., 2005 and references therein).
The title compound crystallizes in the monoclinic space group P21/c and the molecule is located on a crystallographic inversion center. The bond lengths and bond angles are in normal ranges. The terminal aminophenoxy rings are almost perpendicular to the central benzene ring with a dihedral angle of 85.40 (4) °.
The compound exhibits a zigzag like packing pattern (figure 2). The hydrogen atoms of the amino groups are engaged in two types of intermolecular hydrogen bonding interactions. The first one with the nitrogen atoms of other amino groups and the second with the oxygen atoms of the phenoxy groups (Table 1). Intermolecular C—H···π contacts between adjacent phenoxy groups are also present (Fig. 3). The C—C distance of C6—H6···C6iii (iii = x, 0.5 - y, 1/2 + z) is 2.74 (2) Å and C—H···C angle is 175 (1) °, while the dihedral angle between the two phenoxy mean planes is 88.82 (3) °. Additional contacts take place between the central phenyl group and the adjacent terminal phenoxy group with a C—C distance for C9—H9···C2iv (iv = 1 + x, y, z) of 2.180 (1) %A.