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The crystal structure of the title compound, C
19H
16N
2O
2, displays a
trans configuration of the azo moiety, which forms an intramolecular O—H
N=N hydrogen bond. The H
N and O
N distances are 1.81 (3) and 2.581 (4) Å, respectively. The azobenzene moiety is approximately planar, and has a dihedral angle of
ca 23° with the substituted phenyl group.
Supporting information
CCDC reference: 150358
The title compound was prepared by azoic copulation of 4-methoxyphenyldiazonium salt (0.022 mol of p-anisidine and 0.025 mol of sodium nitrite in strong acidic aqueous solution) with an alkaline aqueous solution of 4-phenylphenol (0.021 mol). After chromatographic purification (hexane-ethyl acetate 70:30 in SiO2 230–400 mesh), the crystals were grown by slow evaporation of the solution at room temperature, m.p. 396–399 K.
Data collection: XSCANS (Siemens, 1994); cell refinement: XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXTL/PC (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL/PC; software used to prepare material for publication: SHELXL97.
4-phenyl-2-[4-Methoxyphenyldiazenyl]phenol
top
Crystal data top
C19H16N2O2 | F(000) = 640 |
Mr = 304.34 | Dx = 1.277 Mg m−3 |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.71073 Å |
a = 6.449 (2) Å | Cell parameters from 49 reflections |
b = 8.638 (2) Å | θ = 4.9–24.5° |
c = 28.414 (17) Å | µ = 0.08 mm−1 |
β = 90.48 (4)° | T = 273 K |
V = 1582.9 (1) Å3 | Prism, red |
Z = 4 | 0.40 × 0.24 × 0.20 mm |
Data collection top
Siemens P4/PC diffractometer | Rint = 0.045 |
Radiation source: fine-focus sealed tube | θmax = 25.0°, θmin = 2.5° |
Graphite monochromator | h = 0→7 |
ω–2θ scans | k = 0→10 |
3062 measured reflections | l = −33→33 |
2794 independent reflections | 3 standard reflections every 97 reflections |
1126 reflections with I > 2σ(I) | intensity decay: <2% |
Refinement top
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)] = 0.048 | H-atom parameters constrained |
wR(F2) = 0.127 | Calculated w = 1/[s2(Fo2) + (0.0488P)2] where P = (Fo2 + 2Fc2)/3 |
S = 0.77 | (Δ/σ)max < 0.001 |
2794 reflections | Δρmax = 0.11 e Å−3 |
212 parameters | Δρmin = −0.20 e Å−3 |
0 restraints | Extinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0102 (11) |
Crystal data top
C19H16N2O2 | V = 1582.9 (1) Å3 |
Mr = 304.34 | Z = 4 |
Monoclinic, P21/n | Mo Kα radiation |
a = 6.449 (2) Å | µ = 0.08 mm−1 |
b = 8.638 (2) Å | T = 273 K |
c = 28.414 (17) Å | 0.40 × 0.24 × 0.20 mm |
β = 90.48 (4)° | |
Data collection top
Siemens P4/PC diffractometer | Rint = 0.045 |
3062 measured reflections | 3 standard reflections every 97 reflections |
2794 independent reflections | intensity decay: <2% |
1126 reflections with I > 2σ(I) | |
Refinement top
R[F2 > 2σ(F2)] = 0.048 | 0 restraints |
wR(F2) = 0.127 | H-atom parameters constrained |
S = 0.77 | Δρmax = 0.11 e Å−3 |
2794 reflections | Δρmin = −0.20 e Å−3 |
212 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 | Uiso*/Ueq | |
O1 | 0.4701 (4) | 1.0730 (3) | 0.09940 (8) | 0.0816 (8) | |
H1 | 0.397 (5) | 1.027 (4) | 0.0774 (10) | 0.060* | |
O2 | −0.1259 (4) | 0.5901 (3) | −0.09131 (8) | 0.0879 (8) | |
N1 | 0.1696 (4) | 0.9116 (3) | 0.06438 (8) | 0.0623 (7) | |
N2 | 0.0578 (4) | 0.9241 (3) | 0.10099 (8) | 0.0621 (7) | |
C1 | 0.0790 (5) | 0.8262 (4) | 0.02666 (9) | 0.0564 (8) | |
C2 | −0.1168 (5) | 0.7605 (4) | 0.02715 (10) | 0.0687 (9) | |
H2 | −0.1991 | 0.7703 | 0.0537 | 0.060* | |
C3 | −0.1895 (5) | 0.6814 (4) | −0.01111 (11) | 0.0687 (9) | |
H3 | −0.3212 | 0.6376 | −0.0104 | 0.060* | |
C4 | −0.0688 (5) | 0.6657 (4) | −0.05120 (10) | 0.0668 (9) | |
C5 | 0.1256 (5) | 0.7332 (4) | −0.05185 (11) | 0.0721 (10) | |
H5 | 0.2063 | 0.7247 | −0.0787 | 0.060* | |
C6 | 0.2014 (5) | 0.8126 (4) | −0.01349 (10) | 0.0664 (9) | |
H6 | 0.3328 | 0.8568 | −0.0142 | 0.060* | |
C7 | −0.3243 (6) | 0.5205 (5) | −0.09392 (13) | 0.0967 (13) | |
H7A | −0.3265 | 0.4300 | −0.0743 | 0.060* | |
H7B | −0.3540 | 0.4915 | −0.1259 | 0.060* | |
H7C | −0.4270 | 0.5927 | −0.0833 | 0.060* | |
C11 | 0.3472 (5) | 1.0766 (4) | 0.13804 (11) | 0.0639 (9) | |
C12 | 0.1504 (5) | 1.0073 (4) | 0.13833 (10) | 0.0564 (8) | |
C13 | 0.0320 (5) | 1.0171 (4) | 0.17951 (10) | 0.0591 (8) | |
H13 | −0.0989 | 0.9720 | 0.1796 | 0.060* | |
C14 | 0.1008 (5) | 1.0906 (4) | 0.21970 (10) | 0.0581 (8) | |
C15 | 0.3002 (5) | 1.1555 (4) | 0.21825 (11) | 0.0681 (9) | |
H15 | 0.3539 | 1.2031 | 0.2451 | 0.060* | |
C16 | 0.4183 (5) | 1.1504 (4) | 0.17804 (11) | 0.0737 (10) | |
H16 | 0.5480 | 1.1975 | 0.1779 | 0.060* | |
C17 | −0.0285 (5) | 1.0970 (4) | 0.26296 (9) | 0.0539 (7) | |
C18 | −0.1834 (5) | 0.9885 (4) | 0.27078 (10) | 0.0655 (9) | |
H18 | −0.2033 | 0.9091 | 0.2491 | 0.060* | |
C19 | −0.3089 (5) | 0.9953 (4) | 0.31004 (11) | 0.0731 (10) | |
H19 | −0.4110 | 0.9208 | 0.3146 | 0.060* | |
C20 | −0.2823 (5) | 1.1124 (4) | 0.34225 (11) | 0.0713 (9) | |
H20 | −0.3674 | 1.1181 | 0.3685 | 0.060* | |
C21 | −0.1304 (6) | 1.2205 (4) | 0.33565 (11) | 0.0700 (10) | |
H21 | −0.1110 | 1.2990 | 0.3577 | 0.060* | |
C22 | −0.0048 (5) | 1.2138 (4) | 0.29625 (10) | 0.0635 (9) | |
H22 | 0.0969 | 1.2887 | 0.2920 | 0.060* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
O1 | 0.0738 (16) | 0.105 (2) | 0.0660 (14) | −0.0193 (15) | 0.0223 (12) | −0.0006 (14) |
O2 | 0.0790 (17) | 0.105 (2) | 0.0796 (16) | −0.0001 (16) | 0.0076 (13) | −0.0338 (16) |
N1 | 0.0703 (17) | 0.0651 (18) | 0.0519 (14) | 0.0013 (15) | 0.0171 (13) | 0.0070 (13) |
N2 | 0.0691 (17) | 0.0682 (17) | 0.0490 (14) | 0.0015 (15) | 0.0114 (13) | 0.0041 (13) |
C1 | 0.066 (2) | 0.0552 (19) | 0.0479 (17) | 0.0025 (17) | 0.0133 (15) | 0.0057 (14) |
C2 | 0.073 (2) | 0.082 (3) | 0.0516 (18) | −0.008 (2) | 0.0200 (16) | −0.0001 (18) |
C3 | 0.066 (2) | 0.074 (2) | 0.066 (2) | −0.0054 (19) | 0.0157 (17) | 0.0047 (18) |
C4 | 0.072 (2) | 0.071 (2) | 0.0570 (19) | 0.010 (2) | 0.0065 (17) | −0.0046 (18) |
C5 | 0.067 (2) | 0.090 (3) | 0.060 (2) | 0.005 (2) | 0.0212 (17) | −0.0045 (19) |
C6 | 0.061 (2) | 0.078 (2) | 0.0606 (19) | −0.0022 (19) | 0.0152 (16) | 0.0025 (18) |
C7 | 0.100 (3) | 0.097 (3) | 0.094 (3) | −0.003 (3) | −0.005 (2) | −0.021 (2) |
C11 | 0.066 (2) | 0.062 (2) | 0.0632 (19) | 0.0008 (19) | 0.0142 (17) | 0.0066 (17) |
C12 | 0.059 (2) | 0.0587 (19) | 0.0519 (17) | 0.0017 (17) | 0.0055 (15) | 0.0042 (15) |
C13 | 0.060 (2) | 0.059 (2) | 0.0581 (18) | −0.0042 (17) | 0.0080 (16) | 0.0056 (16) |
C14 | 0.0601 (19) | 0.0564 (19) | 0.0580 (17) | −0.0014 (17) | 0.0046 (15) | 0.0057 (16) |
C15 | 0.072 (2) | 0.074 (2) | 0.0582 (19) | −0.007 (2) | 0.0004 (17) | −0.0086 (17) |
C16 | 0.062 (2) | 0.087 (3) | 0.071 (2) | −0.020 (2) | 0.0104 (18) | 0.001 (2) |
C17 | 0.0597 (19) | 0.0512 (18) | 0.0508 (16) | 0.0032 (16) | 0.0017 (14) | 0.0021 (15) |
C18 | 0.078 (2) | 0.063 (2) | 0.0563 (18) | −0.003 (2) | 0.0091 (17) | −0.0094 (16) |
C19 | 0.070 (2) | 0.078 (3) | 0.072 (2) | −0.009 (2) | 0.0158 (18) | −0.0007 (19) |
C20 | 0.076 (2) | 0.078 (2) | 0.0601 (19) | 0.004 (2) | 0.0156 (17) | −0.0017 (19) |
C21 | 0.090 (3) | 0.063 (2) | 0.0572 (18) | 0.002 (2) | 0.0057 (18) | −0.0079 (16) |
C22 | 0.071 (2) | 0.057 (2) | 0.0628 (19) | −0.0008 (18) | 0.0057 (17) | 0.0015 (16) |
Geometric parameters (Å, º) top
O1—C11 | 1.361 (4) | C11—C12 | 1.403 (4) |
O1—H1 | 0.87 (3) | C12—C13 | 1.405 (4) |
O2—C4 | 1.360 (4) | C13—C14 | 1.377 (4) |
O2—C7 | 1.414 (4) | C13—H13 | 0.9300 |
N1—N2 | 1.275 (3) | C14—C15 | 1.405 (4) |
N1—C1 | 1.423 (4) | C14—C17 | 1.492 (4) |
N2—C12 | 1.409 (4) | C15—C16 | 1.379 (4) |
C1—C2 | 1.385 (4) | C15—H15 | 0.9300 |
C1—C6 | 1.398 (4) | C16—H16 | 0.9300 |
C2—C3 | 1.365 (4) | C17—C18 | 1.389 (4) |
C2—H2 | 0.9300 | C17—C22 | 1.391 (4) |
C3—C4 | 1.392 (4) | C18—C19 | 1.384 (4) |
C3—H3 | 0.9300 | C18—H18 | 0.9300 |
C4—C5 | 1.382 (5) | C19—C20 | 1.374 (5) |
C5—C6 | 1.373 (4) | C19—H19 | 0.9300 |
C5—H5 | 0.9300 | C20—C21 | 1.369 (5) |
C6—H6 | 0.9300 | C20—H20 | 0.9300 |
C7—H7A | 0.9600 | C21—C22 | 1.388 (5) |
C7—H7B | 0.9600 | C21—H21 | 0.9300 |
C7—H7C | 0.9600 | C22—H22 | 0.9300 |
C11—C16 | 1.377 (4) | | |
| | | |
C11—O1—H1 | 106 (2) | C11—C12—N2 | 126.3 (3) |
C4—O2—C7 | 119.2 (3) | C13—C12—N2 | 115.3 (3) |
N2—N1—C1 | 115.4 (3) | C14—C13—C12 | 123.1 (3) |
N1—N2—C12 | 114.7 (3) | C14—C13—H13 | 118.4 |
C2—C1—C6 | 119.7 (3) | C12—C13—H13 | 118.4 |
C2—C1—N1 | 124.8 (3) | C13—C14—C15 | 116.5 (3) |
C6—C1—N1 | 115.4 (3) | C13—C14—C17 | 121.5 (3) |
C3—C2—C1 | 120.2 (3) | C15—C14—C17 | 121.9 (3) |
C3—C2—H2 | 119.9 | C16—C15—C14 | 121.7 (3) |
C1—C2—H2 | 119.9 | C16—C15—H15 | 119.2 |
C2—C3—C4 | 120.7 (3) | C14—C15—H15 | 119.2 |
C2—C3—H3 | 119.6 | C11—C16—C15 | 120.9 (3) |
C4—C3—H3 | 119.6 | C11—C16—H16 | 119.5 |
O2—C4—C5 | 115.6 (3) | C15—C16—H16 | 119.5 |
O2—C4—C3 | 125.6 (3) | C18—C17—C22 | 117.2 (3) |
C5—C4—C3 | 118.8 (3) | C18—C17—C14 | 120.9 (3) |
C6—C5—C4 | 121.3 (3) | C22—C17—C14 | 121.9 (3) |
C6—C5—H5 | 119.4 | C19—C18—C17 | 121.7 (3) |
C4—C5—H5 | 119.4 | C19—C18—H18 | 119.2 |
C5—C6—C1 | 119.2 (3) | C17—C18—H18 | 119.2 |
C5—C6—H6 | 120.4 | C20—C19—C18 | 119.9 (4) |
C1—C6—H6 | 120.4 | C20—C19—H19 | 120.1 |
O2—C7—H7A | 109.5 | C18—C19—H19 | 120.1 |
O2—C7—H7B | 109.5 | C21—C20—C19 | 119.8 (3) |
H7A—C7—H7B | 109.5 | C21—C20—H20 | 120.1 |
O2—C7—H7C | 109.5 | C19—C20—H20 | 120.1 |
H7A—C7—H7C | 109.5 | C20—C21—C22 | 120.3 (3) |
H7B—C7—H7C | 109.5 | C20—C21—H21 | 119.9 |
O1—C11—C16 | 118.8 (3) | C22—C21—H21 | 119.9 |
O1—C11—C12 | 121.8 (3) | C21—C22—C17 | 121.2 (3) |
C16—C11—C12 | 119.3 (3) | C21—C22—H22 | 119.4 |
C11—C12—C13 | 118.4 (3) | C17—C22—H22 | 119.4 |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···N1 | 0.88 (3) | 1.81 (3) | 2.581 (4) | 146 (3) |
Experimental details
Crystal data |
Chemical formula | C19H16N2O2 |
Mr | 304.34 |
Crystal system, space group | Monoclinic, P21/n |
Temperature (K) | 273 |
a, b, c (Å) | 6.449 (2), 8.638 (2), 28.414 (17) |
β (°) | 90.48 (4) |
V (Å3) | 1582.9 (1) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.08 |
Crystal size (mm) | 0.40 × 0.24 × 0.20 |
|
Data collection |
Diffractometer | Siemens P4/PC diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 3062, 2794, 1126 |
Rint | 0.045 |
(sin θ/λ)max (Å−1) | 0.595 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.048, 0.127, 0.77 |
No. of reflections | 2794 |
No. of parameters | 212 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.11, −0.20 |
Selected geometric parameters (Å, º) topO1—C11 | 1.361 (4) | N1—N2 | 1.275 (3) |
O2—C4 | 1.360 (4) | N1—C1 | 1.423 (4) |
O2—C7 | 1.414 (4) | N2—C12 | 1.409 (4) |
| | | |
N2—N1—C1 | 115.4 (3) | O2—C4—C3 | 125.6 (3) |
N1—N2—C12 | 114.7 (3) | O1—C11—C16 | 118.8 (3) |
C2—C1—N1 | 124.8 (3) | O1—C11—C12 | 121.8 (3) |
C6—C1—N1 | 115.4 (3) | C11—C12—N2 | 126.3 (3) |
O2—C4—C5 | 115.6 (3) | C13—C12—N2 | 115.3 (3) |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···N1 | 0.88 (3) | 1.81 (3) | 2.581 (4) | 146 (3) |
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The extensive application of azo dyes in industry and in analytical determinations has attracted the attention for decades. Some arylazo compounds derived from resorcinol or β-naphtol have widely been used in spectrophotometric determination of metal traces (Betteridge & John, 1973; Pollard et al., 1959). Furthermore, the tautomeric hydroxyazoquinone-hydrazone equilibrium has been evidenced for this kind of compound (Stoyanov & Antonov, 1988; Antonov et al., 1994; Antonov et al., 1995; Antonov & Stoyanov, 1995; Buncel & Keum, 1983). The existence of intramolecular hydrogen bond is of particular interest (Antonov & Stoyanov, 1995). Currently, we are developing a series of novel arylazo dyes derived from 4-phenylphenol in order to investigate the tautomeric equilibrium in solution. X-ray structure analysis of the title compound, (I), has been carried out to observe the conformation of the molecule in the crystals.
The molecular structure is shown in Fig. 1 with atom-numbering scheme. The compound is constituted by phenyl rings A (C1 to C6), B (C11 to C16), C (C17 to C22) and the azo frame D (C1—N1—N2—C12). The phenyl rings A and B adopt a trans configuration about azo functional group, as observed in crystals of the other azo compounds. The dihedral angle between A and B is 2.7 (2)°, which is less than those of 3-tert-butyl-2'-chloro-2-hydroxy-5-methylazobenzene, (I), [5.85° (Isik, Aygün, Kocaokutgen & Tahir, 1998)] and 2-hydroxy-5-tert-butylazobenzene, (II) (3.4°; Candan et al., 1999). The phenyl-azo-benzene frame (A—D—B) is practically planar [shifts of the atoms from the best plane are less than 0.0341 (2) Å], as observed in the crystals of 3-tert-butyl-2-hydroxy-5-methoxyazobenzene, (III) (Isik, Aygün, Kocaokutgen, Tahir et al., 1998). The dihedral angles of the C ring with the ring B and azo frame D are 24.2 (2) and 22.5 (2)°, respectively.
The N1═N2 bond distance is 1.275 (2) Å (Table 1), which is longer than those observed in the azo compounds without intramolecular hydrogen bonds, 2-hydroxy-5-{[4-(2-pyridinylamino)sulfonyl]phenyl}azo)benzoic acid [1.223 (7) Å; van der Sluis & Spek, 1990], and 5'-allyl-2'-benzoyloxy-3'-methoxy-4-nitroazobenzene [1.241 (3) Å; Isik et al., 2000]. The lengthened N═N distance of (I) caused by the intramolecular hydrogen bond (Table 2) with the ortho hydroxyl group in the aromatic moiety is essentially identical to that of (III), 1.274 (3) Å, and a little longer than those of (I) and (II), 1.266 (2) and 1.265 (2) Å, respectively. In bis-4-dimethylaminonaphtaleneazo)-4,4'-stilbene, the N═N distance is 1.256 (3) Å (Foitzik et al., 1991). In (I), the C2—H2···N2 close contact [H2···N2, 2.506 (3) Å, C2···N2, 2.762 (4) Å and C2—H2···N2, 95.9 (2)°] may also contribute to the planarity of the molecule.
The intramolecular hydrogen bond in (I) is comprehensible by comparison with another conformer, (Ia), which can be derived from the concerted rotation of the O1—H1 bond of (I) around the C11—O1 axis by 180°. An ab initio calculation of the optimized geometries (Frisch et al., 1993) indicated that the conformer (I) is more stable than (Ia) by 56.4 kJ mol−1 and 42.5 kJ mol−1 at RHF/3–21 G* and RHF/6–31 G* levels, respectively.