4-{(E)-2-[4-(But-3-en-1-yl­oxy)phen­yl]diazen-1-yl}benzoic acid

Md Lutfor Rahman; Huey Chong Kwong; Mashitah Mohd Yusoff; Gurumurthy Hegde; Mohamed Ibrahim Mohamed Tahir; Mohamad Zaki Ab Rahman

doi:10.1107/S1600536812038718

. 2012 Sep 19;68(Pt 10):o2958. doi: 10.1107/S1600536812038718

4-{(E)-2-[4-(But-3-en-1-yloxy)phenyl]diazen-1-yl}benzoic acid

Md Lutfor Rahman ^a,^*, Huey Chong Kwong ^b, Mashitah Mohd Yusoff ^a, Gurumurthy Hegde ^a, Mohamed Ibrahim Mohamed Tahir ^b, Mohamad Zaki Ab Rahman ^b

PMCID: PMC3470328 PMID: 23125741

Abstract

The title compound, C₁₇H₁₆N₂O₃, has an E conformation about the azobenzene (–N=N–) linkage. The benzene rings are twisted slightly with respect to each other [6.79 (9)°], while the dihedral angle between the plane through the carboxy group and the attached benzene ring is 3.2 (2)°. In the crystal, molecules are oriented with the carboxy groups head-to-head, forming O—H⋯O hydrogen-bonded inversion dimers. These dimers are connected by C—H⋯O hydrogen-bonds into layers lying parallel to the (013) plane.

Related literature

For the physical properties of compounds containing an azobenzene (–N=N–) linkage, see: Chigrinov (2005 ▶); Hegde (2007 ▶). For related structures, see: Yu & Liu (2009 ▶); Lai et al. (2002 ▶); Centore & Tuzi (2003 ▶). For standard bond lengths, see Allen et al. (1987 ▶).

Experimental

Crystal data

C₁₇H₁₆N₂O₃
M _r = 296.33
Triclinic,
a = 7.0937 (7) Å
b = 9.8687 (10) Å
c = 11.2490 (11) Å
α = 87.334 (8)°
β = 73.475 (8)°
γ = 75.174 (8)°
V = 729.54 (13) Å³
Z = 2
Cu Kα radiation
μ = 0.77 mm⁻¹
T = 100 K
0.26 × 0.16 × 0.04 mm

Data collection

Oxford Diffraction Gemini diffractometer
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2006 ▶) T _min = 0.85, T _max = 0.97
9940 measured reflections
2783 independent reflections
2298 reflections with I > 2.0σ(I)
R _int = 0.024

Refinement

R[F ² > 2σ(F ²)] = 0.054
wR(F ²) = 0.146
S = 1.00
2773 reflections
199 parameters
H-atom parameters constrained
Δρ_max = 0.51 e Å⁻³
Δρ_min = −0.33 e Å⁻³

Data collection: CrysAlis CCD (Oxford Diffraction, 2006 ▶); cell refinement: CrysAlis CCD; data reduction: CrysAlis RED (Oxford Diffraction, 2006 ▶); program(s) used to solve structure: Superflip (Palatinus & Chapuis, 2007 ▶); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003 ▶); molecular graphics: Mercury (Macrae et al., 2006 ▶); software used to prepare material for publication: CRYSTALS.

Supplementary Material

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S1600536812038718/su2476sup1.cif

e-68-o2958-sup1.cif^{(17.4KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536812038718/su2476Isup2.hkl

e-68-o2958-Isup2.hkl^{(174.8KB, hkl)}

Supplementary material file. DOI: 10.1107/S1600536812038718/su2476Isup3.cml

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O3—H2⋯O1ⁱ	0.87	1.76	2.612 (3)	166 (1)
C21—H211⋯O1ⁱⁱ	0.95	2.50	3.275 (3)	139 (1)

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Symmetry codes: (i) Inline graphic ; (ii) .

Acknowledgments

This research was supported by a UMP research grant (No. RDU100338).

supplementary crystallographic information

Comment

An in a molecule introduces the possibility of photochromism and photoisomerization (Chigrinov, 2005). Photonics, in which the light can be controlled by light as stimulus has been exploited (Hegde, 2007). Upon absorption of UV light (~ 365 nm) the energetically more stable E conformation, transforms into the Z conformation. The reverse transformation of the Z isomer into the E isomer can be brought about by irradiation with visible light (in the range of 400–500 nm). The latter can also occur in the "dark" by a process known as "thermal back relaxation" in a period ranging from minutes to tens of hours depending on the system. In this case molecules again transform from the metastable cis-conformation to the energetically stable trans-conformation. In conclusion, the present investigation on rod-shaped azo dyes is very useful for a variety of photonic applications. Excellent quality, cost effective, easy to prepare, are properties which make these devices very attractive for future generations. Detailed investigations on the physics of these azo dyes is under intense consideration.

The bond lengths (Allen et al.,1987) and bond angles in the titled compound (Fig. 1) are normal. The carbonyl group (C2/O1/O3) is almost coplanar with the attached benzene ring (C4-C7/C21/C22) with a dihedral angle of only 3.2 (2)°. The length of N8═N9 bond is 1.263 (2) Å and the torsion angle for the azo unit (C7—N8—N9—C10) is -177.75 (16)° rather than ca. ±180° as observed elsewhere: For example: 4,4-Azinodibenzoic acid (Yu and Liu, 2009) and (E)-ethyl 4-((4-(decanoyloxy)phenyl)diazenyl)benzoate (Lai et al.,2002). However, it is comparable with the value of 175.10° observed for (E)-4-((4-((2-hydroxyethyl)(methyl)amino)phenyl)diazenyl)benzoic acid (Centore & Tuzi, 2003). The benzene rings (C4-C7/C21/C22 and C10-C3/C19/C20) lie at a mutual dihedral angles of 6.79 (9)°, compared to 16.69° in (E)-4-((4-((2-hydroxyethyl)(methyl)amino)phenyl)diazenyl)benzoic acid (Centore & Tuzi, 2003). The C15—C16—C17—C18 torsion angle in the butyl group is 126.1 (3)°.

In the crystal, the carboxyl groups are oriented head-to-head forming hydrogen bonded inversion dimers (Table 1 and Fig. 2). These dimers are further linked by C—H···O hydrogen bonds to a generate a layer parallel to the (013) plane (Table 1 and Fig. 2).

Experimental

The title compound was prepared from ethyl 4-aminobenzoate. Firstly the diazonuim salt was prepared using one equivalent of sodium nitrite to one equivalent of ethyl 4-aminobenzoate in methanol - water mixture at 275 K, in the presence of 3 equivalents of aqueous hydrochloric acid, which was coupled with phenol to yield ethyl 4-[(4-hydroxyphenyl)diazenyl]benzoate. This compound was then alkylated with 4-bromo-1-butene in the presence of potassium carbonate as base to give the ester, ethyl 4-{[4-(but-3-en-1-yloxy)phenyl]diazenyl}benzoate. This compound was then hydrolyzed under basic conditions to yield the title benzoic acid. Brown plate-like crystals of the title compound were obtained by slow evaporation of a solution in methanol.