1,4-Bis(4-amino­phen­oxy)benzene

Shemsi, A.M.; Butt, S.M.; Fettouhi, M.; Siddiqi, H.M.; Akhter, Z.

doi:10.1107/S160053680800367X

organic compounds

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ISSN: 2056-9890

Volume 64| Part 3| March 2008| Page o581

doi:10.1107/S160053680800367X

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1,4-Bis(4-aminophenoxy)benzene

Ahsan M. Shemsi,^a,^b Saeed M. Butt,^c Mohammed Fettouhi,^a Humaira M. Siddiqi ^c and Zareen Akhter ^c ^*

^aChemistry Department, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia, ^bPAEC 1331, Islamabad, Pakistan, and ^cDepartment of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan
^*Correspondence e-mail: zareenakhter@yahoo.com

(Received 28 July 2007; accepted 2 February 2008; online 13 February 2008)

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—H⋯N intermolecular hydrogen-bonding interactions.

Related literature

For related literature on polyimides and their solubility, see: Yang et al. (2002 ). For examples of chemical- and heat-resistant polyimides, see: Butt et al. (2005 ). Choi et al. (2001 ) discuss polyimides with various length (n-alkoxy)phenyloxy side branches. For polyimides with improved properties such as processing from the melt or from solution, see: Eastmond & Paprotny (1996 ). For different structural modifications of the polymer backbone to reduce the chain interaction and their effect on chain packing and glass transition temperature, see: Yan et al. (2005 ) and references therein.

Experimental

Crystal data

C₁₈H₁₆N₂O₂
M_r = 292.33
Monoclinic, P 2₁ /c
a = 6.9579 (9) Å
b = 22.664 (3) Å
c = 5.1202 (7) Å
β = 111.287 (2)°
V = 752.34 (17) Å³
Z = 2
Mo Kα radiation
μ = 0.09 mm⁻¹
T = 296 (2) K
0.42 × 0.40 × 0.20 mm

Data collection

Bruker SMART APEX area-detector diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 1996 ) T_min = 0.912, T_max = 0.983
6563 measured reflections
1805 independent reflections
1324 reflections with I > 2σ(I)
R_int = 0.016

Refinement

R[F² > 2σ(F²)] = 0.039
wR(F²) = 0.110
S = 1.03
1805 reflections
132 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.11 e Å⁻³
Δρ_min = −0.17 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

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) $[x, -y+{\script{1\over 2}}, z-{\script{1\over 2}}]$ ; (ii) x+1, y, z.

Data collection: SMART (Bruker, 2001 ); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL, WinGX (Farrugia, 1999 ) and Mercury (Macrae et al., 2006 ).

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S160053680800367X/zl2055sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S160053680800367X/zl2055Isup2.hkl

checkCIF report

Comment top

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···C2^iv (iv = 1 + x, y, z) of 2.180 (1) %A.

Related literature top

For related literature about polyimides and their solubility see Yang et al. (2002). For examples of chemical and heat resistant polyimides, see: Butt et al. (2005). Choi et al. (2001) discuss polyimides with various length (n-alkoxy)phenyloxy side branches. For polyimides with improved properties such as processing from the melt or from solution, see: Eastmond & Paprotny (1996). For different structural modifications of the polymer backbone to reduce the chain interaction and their effect on chain packing and glass transition temperature, see: Yan et al. (2005) and references therein.

Experimental top

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).

Computing details top

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).

Figures top

	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).
	Fig. 2. The packing of the compound, viewed down the c axis, showing the zig zag packing pattern.
	Fig. 3. Hydrogen bonding and part of the C—H···π interactions in the title compound.

1,4-Bis(4-aminophenoxy)benzene top

Crystal data top

C₁₈H₁₆N₂O₂	F(000) = 308
M_r = 292.33	D_x = 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 = 1.8–28.3°
b = 22.664 (3) Å	µ = 0.09 mm⁻¹
c = 5.1202 (7) Å	T = 296 K
β = 111.287 (2)°	Parallelepiped, colorless
V = 752.34 (17) Å³	0.42 × 0.40 × 0.20 mm
Z = 2

Data collection top

Bruker SMART APEX area-detector diffractometer	1805 independent reflections
Radiation source: normal-focus sealed tube	1324 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.016
ω scans	θ_max = 28.3°, θ_min = 1.8°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −9→9
T_min = 0.912, T_max = 0.983	k = −29→29
6563 measured reflections	l = −6→6

Refinement top

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)] = 0.039	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.110	H atoms treated by a mixture of independent and constrained refinement
S = 1.03	w = 1/[σ²(F_o²) + (0.0514P)² + 0.0611P] where P = (F_o² + 2F_c²)/3
1805 reflections	(Δ/σ)_max = 0.001
132 parameters	Δρ_max = 0.11 e Å⁻³
0 restraints	Δρ_min = −0.18 e Å⁻³

Crystal data top

C₁₈H₁₆N₂O₂	V = 752.34 (17) Å³
M_r = 292.33	Z = 2
Monoclinic, P2₁/c	Mo Kα radiation
a = 6.9579 (9) Å	µ = 0.09 mm⁻¹
b = 22.664 (3) Å	T = 296 K
c = 5.1202 (7) Å	0.42 × 0.40 × 0.20 mm
β = 111.287 (2)°

Data collection top

Bruker SMART APEX area-detector diffractometer	1805 independent reflections
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	1324 reflections with I > 2σ(I)
T_min = 0.912, T_max = 0.983	R_int = 0.016
6563 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.039	0 restraints
wR(F²) = 0.110	H atoms treated by a mixture of independent and constrained refinement
S = 1.03	Δρ_max = 0.11 e Å⁻³
1805 reflections	Δρ_min = −0.18 e Å⁻³
132 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.

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
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)*

Atomic displacement parameters (Å²) top

	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)

Geometric parameters (Å, º) top

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 code: (i) −x, −y+1, −z+1.

Hydrogen-bond geometry (Å, º) top

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.

Experimental details

Crystal data
Chemical formula	C₁₈H₁₆N₂O₂
M_r	292.33
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	296
a, b, c (Å)	6.9579 (9), 22.664 (3), 5.1202 (7)
β (°)	111.287 (2)
V (Å³)	752.34 (17)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	0.09
Crystal size (mm)	0.42 × 0.40 × 0.20

Data collection
Diffractometer	Bruker SMART APEX area-detector diffractometer
Absorption correction	Multi-scan (SADABS; Sheldrick, 1996)
T_min, T_max	0.912, 0.983
No. of measured, independent and observed [I > 2σ(I)] reflections	6563, 1805, 1324
R_int	0.016
(sin θ/λ)_max (Å⁻¹)	0.666

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.039, 0.110, 1.03
No. of reflections	1805
No. of parameters	132
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.11, −0.18

Computer programs: SMART (Bruker, 2001), SAINT (Bruker, 2001), SHELXTL (Sheldrick, 2008), WinGX (Farrugia, 1999) and Mercury (Macrae et al., 2006).

Hydrogen-bond geometry (Å, º) top

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.

Acknowledgements

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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