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Structure analysis of the title compound, C9H6BrNO, has established that bromination of an 8-hydroxyquinoline derivative occurred in the 7-position. Intermolecular and weak intramolecular O—H...N hydrogen bonds are present, the former causing the mol­ecules to pack as hydrogen-bonded dimers in the solid state.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270103013714/ga1024sup1.cif
Contains datablocks global, II

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270103013714/ga1024IIsup2.hkl
Contains datablock II

pdf

Portable Document Format (PDF) file https://doi.org/10.1107/S0108270103013714/ga1024sup3.pdf
Supplementary material

CCDC reference: 219573

Comment top

Because of our interest in synthesizing a variety of 7-substituted 8-hydroxyquinoline ligands, studies into the electrophilic aromatic halogenation of 8-hydroxyquinoline, (I), were considered. The literature presents four key papers that describe the synthesis of 7-bromo-8-hydroxyquinoline, (II), via two different routes. The earliest procedure (Claus & Giwartovsky, 1896), which was later optimized by Gershon et al., 1969) brominated 8-hydroxyquinoline-5-sulfonic acid and subjected this material to acid hydrolysis to afford a product concluded to be (II) (m.p. 411 and 412–413 K, respectively). Alternatively, low-temperature base-induced bromination of (I) (Pearson et al., 1945; Schmitz & Pagenkopf, 1985) gave a product also concluded to be (II) because it has a similar melting point (m.p. 410– 411 K). Unfortunately, no detailed spectral information was provided with these experimental procedures to substantiate the incorporation of the Br atom ortho to the phenolic group.

On further investigation of the literature, it became apparent that there has been some contention regarding the regio-selective halogenation of 8-hydroxyquinoline derivatives and the assignment of the products (Prasad et al., 1965; Gershon et al., 1969). To add to this uncertainty, it has been reported that the acid hydrolysis of 7-bromo-8-hydroxyquinoline-5-sulfonic acid results in the facile migration of the Br atom, thus affording the 5-bromo-8-hydroxyquinoline isomer, (III) (Suzuki et al., 1980). Recently, the NMR assignment for the structure of 7-iodo-8-hydroxyquinoline (Clarke et al., 1998) has been revised on the basis of X-ray crystallographic data (Gershon et al., 1997). A search of the Cambridge Structure Database (Allen, 2002), in which dimerized quinolines at the 7-position were ignored, revealed six reported 7-substituted 8-hydroxyquinoline structures (Albrecht et al., 1999; Boeyens, 1976; Faizi et al., 1997; Gershon et al., 1997; Rericha et al., 1989; Rericha et al., 1990), one of which was the related 7-iodo-8-hydroxyquinoline of Gershon et al. (1997). Because of the limited amount of reported information and the conflicting literature reports, we decided that it was prudent to perform an X-ray crystal structure analysis of the monobromide product using the procedures of Pearson and Gershon.

The structure of (II) was solved in space group C2/c and is shown in Fig. 1, thus confirming that bromination has occurred in the 7-position. The fused ring system is planar, with a r.m.s. deviation from planarity of 0.0181 (12) Å. Both the phenol O atom and the bromo substituent lie essentially in this plane [the out-of-plane distances for atoms O1 and Br1 are 0.090 (6) and 0.060 (2) Å, respectively]. Weak intramolecular hydrogen-bonding interactions are present between the phenol donor (located from a difference map) and the adjacent pyridine N-atom acceptor [O1—H1···N1; O1···N1 = 2.768 (6) Å and O1—H1···N1 = 110.4°]. Moderate intermolecular hydrogen bonds are also present [O1—H1···N1; O1···N1 = 2.736 (6) Å and O1—H1···N1(-x + 1, y, −z + 1/2) = 152.0°]. To facilitate the intermolecular hydrogen bonding, there exists a slight twist of the fused aromatic rings, with an angle of 1.6 (3)° between ring planes. In addition, the mean planes of the two hydrogen-bonded molecules are at an angle of 59.6 (2)° with respect to one another, so that overall the molecules are packed as twisted hydrogen-bonded dimers (Fig. 1).

The current crystallographic data suggest that the synthetic methods of both Gershon et al. (1969) and Pearson et al. (1945) result in the formation of the reported 7-bromo-8-hydroxyquinoline, (II).

Experimental top

The title compound was synthesized following two known literature procedures and was recrystallized to give (II) (m.p. 412–413 K). 1H NMR (CDCl3, TMS): 8.80 (1H, 1J 4.2 3J 1.5 Hz, H2), 8.15 (1H, 1J 8.4 3J 1.5 Hz, H4), 7.62 (1H, 1J 9 Hz, H6), 7.47 (1H, 1J1 8.4 1J2 4.2 Hz, H3), 7.25 (1H, 1J 9 Hz, H5). A sample of (II) was crystallized from cyclohexane, to give needle-like crystals of which a fragment was suitable for X-ray diffraction.

Refinement top

The phenol H atom was located from a difference map, refined using a riding model and given an isotropic displacement parameter equal to 1.2 tomes that of atom O1. All other H atoms were placed in calculated positions, refined using a riding model, and given an isotropic displacement parameter equal to 1.2 times the equivalent isotropic displacement parameter of the atom to which they are attached. There were three remaining residual peaks greater than 0.37 e Å−3, two of which were within 1.1 Å of atom Br1 (1.05 and 0.84 e Å−3). The third and largest residual peak (1.94 e Å−3) was 1.60 Å from atom C5, in-plane with the aromatic ring system but 'leaning' slightly towards atom C4 (Q1—C5—C4 = 111.9°). This peak has been attributed to a minor cocrystallization impurity of 5,7-dibromo-8-hydroxyquinoline (modeling resulted in a <3% occupancy factor for Q1 as Br). 1H NMR analysis of the crystal sample was consistent with this assignment.

Computing details top

Data collection: SMART (Siemens, 1996); cell refinement: SAINT (Siemens, 1996); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 1997); software used to prepare material for publication: SHELXTL.

Figures top
[Figure 1] Fig. 1. ORTEP view of the hydrogen-bonded dimer of 7-bromo-8-hydroxyquinoline (II), showing the atom-labeling scheme and displacement ellipsoids at the 50% probability level.
7-Bromo-8-hydroxyquinoline top
Crystal data top
C9H6BrNOF(000) = 880
Mr = 224.06Dx = 1.853 Mg m3
Monoclinic, C2/cMelting point: 139-140°C K
Hall symbol: -c 2ycMo Kα radiation, λ = 0.71073 Å
a = 26.770 (8) ÅCell parameters from 4647 reflections
b = 4.020 (1) Åθ = 1.7–25.4°
c = 16.344 (5) ŵ = 5.06 mm1
β = 114.077 (5)°T = 203 K
V = 1605.9 (8) Å3Plate, colourless
Z = 80.32 × 0.12 × 0.08 mm
Data collection top
Bruker P4/CCD
diffractometer
1465 independent reflections
Radiation source: fine-focus sealed tube1272 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.026
Detector resolution: 0 pixels mm-1θmax = 25.4°, θmin = 1.7°
ω and ϕ scansh = 3228
Absorption correction: empirical (using intensity measurements)
SADABS (Sheldrick, 1996)
k = 44
Tmin = 0.20, Tmax = 0.67l = 1719
4647 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.049Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.127H-atom parameters constrained
S = 1.11 w = 1/[σ2(Fo2) + (0.0708P)2 + 7.273P]
where P = (Fo2 + 2Fc2)/3
1465 reflections(Δ/σ)max < 0.001
110 parametersΔρmax = 1.94 e Å3
0 restraintsΔρmin = 0.30 e Å3
Crystal data top
C9H6BrNOV = 1605.9 (8) Å3
Mr = 224.06Z = 8
Monoclinic, C2/cMo Kα radiation
a = 26.770 (8) ŵ = 5.06 mm1
b = 4.020 (1) ÅT = 203 K
c = 16.344 (5) Å0.32 × 0.12 × 0.08 mm
β = 114.077 (5)°
Data collection top
Bruker P4/CCD
diffractometer
1465 independent reflections
Absorption correction: empirical (using intensity measurements)
SADABS (Sheldrick, 1996)
1272 reflections with I > 2σ(I)
Tmin = 0.20, Tmax = 0.67Rint = 0.026
4647 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0490 restraints
wR(F2) = 0.127H-atom parameters constrained
S = 1.11Δρmax = 1.94 e Å3
1465 reflectionsΔρmin = 0.30 e Å3
110 parameters
Special details top

Experimental. The following alerts were generated using cif validation in PLATON (Spek, 2002):

094_ALERT_2_B Ratio of Maximum / Minimum Residual Density.. 6.43 Caused by large residual density at a distance of 1.60 Å from C5. Modelling of this as Br resulted in < 3% occupancy. (Co-editor comment): The authors will address the presence of the 5,7-dibromo-8-hydroxyquinoline impurity in a future paper.

341_ALERT_3_C Low Bond Precision on C—C bonds (x 1000) Ang.. 8 no action

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
xyzUiso*/Ueq
Br10.33687 (2)1.14151 (12)0.00079 (3)0.0453 (2)
O10.44173 (15)0.8943 (10)0.1431 (3)0.0466 (9)
H10.46800.77730.17270.070*
N10.45946 (18)0.5781 (11)0.3030 (3)0.0400 (10)
C20.4666 (2)0.4121 (14)0.3768 (4)0.0467 (13)
H2B0.50210.35580.41550.056*
C30.4233 (3)0.3149 (14)0.4002 (4)0.0481 (14)
H3A0.42990.19590.45240.058*
C40.3713 (2)0.4024 (13)0.3432 (4)0.0441 (13)
H4A0.34220.34450.35740.053*
C50.3082 (2)0.6763 (13)0.2034 (4)0.0443 (13)
H50.27780.62530.21510.053*
C60.3019 (2)0.8468 (13)0.1276 (4)0.0441 (13)
H6A0.26720.91460.08820.053*
C70.3473 (2)0.9211 (12)0.1086 (3)0.0369 (11)
C80.3996 (2)0.8248 (12)0.1652 (3)0.0365 (11)
C90.4068 (2)0.6587 (11)0.2451 (3)0.0355 (11)
C100.3612 (2)0.5775 (13)0.2640 (3)0.0389 (11)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Br10.0546 (4)0.0364 (3)0.0375 (3)0.0092 (2)0.0113 (2)0.0032 (2)
O10.0406 (19)0.056 (2)0.040 (2)0.0048 (18)0.0131 (16)0.0093 (17)
N10.041 (2)0.040 (2)0.031 (2)0.0004 (19)0.0074 (18)0.0002 (19)
C20.054 (3)0.042 (3)0.035 (3)0.003 (3)0.008 (2)0.002 (2)
C30.064 (4)0.040 (3)0.037 (3)0.005 (3)0.018 (3)0.003 (2)
C40.055 (3)0.039 (3)0.041 (3)0.007 (2)0.022 (3)0.009 (2)
C50.045 (3)0.040 (3)0.048 (3)0.002 (2)0.019 (2)0.007 (2)
C60.040 (3)0.038 (3)0.046 (3)0.004 (2)0.009 (2)0.008 (2)
C70.045 (3)0.028 (2)0.035 (3)0.001 (2)0.012 (2)0.004 (2)
C80.039 (3)0.031 (3)0.033 (2)0.001 (2)0.008 (2)0.005 (2)
C90.039 (3)0.026 (2)0.035 (3)0.004 (2)0.009 (2)0.007 (2)
C100.046 (3)0.031 (3)0.037 (3)0.006 (2)0.015 (2)0.011 (2)
Geometric parameters (Å, º) top
Br1—C71.888 (5)C4—H4A0.9300
O1—C81.346 (7)C5—C61.364 (8)
O1—H10.8200C5—C101.416 (8)
N1—C21.322 (7)C5—H50.9300
N1—C91.378 (6)C6—C71.403 (8)
C2—C31.416 (9)C6—H6A0.9300
C2—H2B0.9300C7—C81.382 (7)
C3—C41.366 (9)C8—C91.409 (7)
C3—H3A0.9300C9—C101.415 (7)
C4—C101.399 (8)
C8—O1—H1109.5C5—C6—H6A119.6
C2—N1—C9118.1 (5)C7—C6—H6A119.6
N1—C2—C3123.8 (5)C8—C7—C6121.6 (5)
N1—C2—H2B118.1C8—C7—Br1118.7 (4)
C3—C2—H2B118.1C6—C7—Br1119.7 (4)
C4—C3—C2117.5 (5)O1—C8—C7119.6 (5)
C4—C3—H3A121.2O1—C8—C9122.4 (4)
C2—C3—H3A121.2C7—C8—C9118.1 (5)
C3—C4—C10121.3 (5)N1—C9—C8117.5 (5)
C3—C4—H4A119.3N1—C9—C10121.9 (5)
C10—C4—H4A119.3C8—C9—C10120.6 (5)
C6—C5—C10119.5 (5)C4—C10—C9117.3 (5)
C6—C5—H5120.2C4—C10—C5123.4 (5)
C10—C5—H5120.2C9—C10—C5119.3 (5)
C5—C6—C7120.8 (5)
C9—N1—C2—C30.6 (8)O1—C8—C9—N12.4 (7)
N1—C2—C3—C40.8 (8)C7—C8—C9—N1177.0 (4)
C2—C3—C4—C100.9 (8)O1—C8—C9—C10177.2 (4)
C10—C5—C6—C70.9 (8)C7—C8—C9—C103.4 (7)
C5—C6—C7—C80.1 (8)C3—C4—C10—C90.3 (8)
C5—C6—C7—Br1177.4 (4)C3—C4—C10—C5179.4 (5)
C6—C7—C8—O1178.4 (5)N1—C9—C10—C41.8 (7)
Br1—C7—C8—O11.0 (6)C8—C9—C10—C4177.8 (4)
C6—C7—C8—C92.3 (7)N1—C9—C10—C5178.0 (5)
Br1—C7—C8—C9179.6 (3)C8—C9—C10—C52.4 (7)
C2—N1—C9—C8177.7 (4)C6—C5—C10—C4179.9 (5)
C2—N1—C9—C101.9 (7)C6—C5—C10—C90.2 (7)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1—H1···N10.822.372.768 (6)110
O1—H1···N1i0.821.982.736 (6)152
Symmetry code: (i) x+1, y, z+1/2.

Experimental details

Crystal data
Chemical formulaC9H6BrNO
Mr224.06
Crystal system, space groupMonoclinic, C2/c
Temperature (K)203
a, b, c (Å)26.770 (8), 4.020 (1), 16.344 (5)
β (°) 114.077 (5)
V3)1605.9 (8)
Z8
Radiation typeMo Kα
µ (mm1)5.06
Crystal size (mm)0.32 × 0.12 × 0.08
Data collection
DiffractometerBruker P4/CCD
diffractometer
Absorption correctionEmpirical (using intensity measurements)
SADABS (Sheldrick, 1996)
Tmin, Tmax0.20, 0.67
No. of measured, independent and
observed [I > 2σ(I)] reflections
4647, 1465, 1272
Rint0.026
(sin θ/λ)max1)0.603
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.049, 0.127, 1.11
No. of reflections1465
No. of parameters110
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)1.94, 0.30

Computer programs: SMART (Siemens, 1996), SAINT (Siemens, 1996), SAINT, SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997), SHELXTL (Bruker, 1997), SHELXTL.

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1—H1···N10.822.372.768 (6)110.4
O1—H1···N1i0.821.982.736 (6)152.0
Symmetry code: (i) x+1, y, z+1/2.
 

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