Crystal structure of 8-hy­droxy­quinoline: a new monoclinic polymorph

In an attempt to grow 8-hy­droxy­quinoline–acetamino­phen co-crystals from equimolar amounts of conformers in a chloro­form–ethanol solvent mixture at room temperature, the title compound, C₉H₇NO, was obtained. The mol­ecule is planar, with the hy­droxy H atom forming an intra­molecular O—H...N hydrogen bond. In the crystal, mol­ecules form centrosymmetric dimers via two O—H...N hydrogen bonds. Thus, the hy­droxy H atoms are involved in bifurcated O—H...N hydrogen bonds, leading to the formation of a central planar four-membered N₂H₂ ring. The dimers are bound by inter­molecular π–π stacking [the shortest C...C distance is 3.2997 (17) Å] and C—H...π inter­actions into a three-dimensional framework. The crystal grown represents a new monoclinic polymorph in the space group P2₁/n. The mol­ecular structure of the present monoclinic polymorph is very similar to that of the ortho­rhom­bic polymorph (space group Fdd2) studied previously [Roychowdhury et al. (1978). Acta Cryst. B34, 1047–1048; Banerjee & Saha (1986). Acta Cryst. C42, 1408–1411]. The structures of the two polymorphs are distinguished by the different geometries of the hydrogen-bonded dimers, which in the crystal of the ortho­rhom­bic polymorph possess twofold axis symmetry, with the central N₂H₂ ring adopting a butterfly conformation.

Key indicators

• Single-crystal X-ray study
• T = 100 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.039
• wR factor = 0.109
• Data-to-parameter ratio = 17.4

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S1. Comment

Cocrystallization represents a form of supramolecular synthesis where molecules are linked by non–valent intermolecular interactions without making or breaking covalent bonds (Aakeröy et al., 2009; Lemmerer et al., 2011). Cocrystals are distinctly different from solid solutions or mixed crystals, and can be considered as molecular complexes (Desiraju, 2003; Dunitz, 2003). The ability of organic compounds to form cocrystals is dependent on a range of variables, including the types of co–formers, co–former ratios, solvents, temperature, pressure, crystallization technique etc. A systematic exploration of a combination of relevant variables increases the chance of discovering cocrystals with favourable properties.

In this work we attempted to prepare cocrystals of 8-hydroxyquinoline with acetaminophen by cocrystallization from chloroform–ethanol solvent mixture at room temperature. The structures of several cocrystals with 8-hydroxyquinoline have been already reported (Prout & Wheeler, 1967; Castellano & Prout, 1971; Liu & Meng, 2006; Westcott et al., 2009). Unexpectedly, a new polymorph of 8-hydroxyquinoline, C₉H₇NO (I), was isolated, and its crystal structure was studied by X–ray diffraction analysis. However, no polymorphs of 8-hydroxyquinoline were found in Cambridge strustural database. The result presented here can be considered as a new example of so called "induced polymorphism" (Bernstein, 2002; Timofeeva et al., 2003).

The molecule of I is planar, with the hydroxyl–H atom forming the intramolecular O—H···N hydrogen bond (Figure 1, Table 1). The crystal grown represents the new monoclinic polymorph in space group P2₁/n. The molecular structure of the monoclinic polymorph of I is very close to that of the orthorhombic polymorph in space group Fdd2 studied previously (Roychowdhury et al., 1978; Banerjee & Saha, 1986). The structures of the two polymorphs are distinct by the different geometries of supramolecular synthons. In the crystals of the both polymorphs, molecules form dimers by the two intermolecular O—H···N hydrogen bonds. Thus, the hydroxyl–H atoms are involved in the bifurcated O—H···N hydrogen bonds leading to the formation of the central four–membered N₂H₂–ring (Table 1 for I). However, the dimers in the crystal of the monoclinic polymorph are centrosymmetrical (C_i, the molecules within the dimer are parallel to each other, the central N₂H₂–ring is planar) (Figure 2), while those in the crystal of the orthorhombic polymorph possess the twofold axis symmetry (C_2, the molecules within the dimer are twisted by 52.4° (av.) relative to each other, the central N₂H₂–ring adopts a butterfly conformation) (Figure 3).

Further, the dimers are bound by the intermolecular π–π stacking (the interplane distance between the mean planes of closest parallel molecules in I is 3.3155 (17) Å) and C—H···π (H2···C4Aⁱ 2.86 Å, H2···C5ⁱ 2.87 Å; H3···C8ⁱ 2.78 Å, H3···C8Aⁱ 3.08 Å) (in the case of the monoclinic polymorph, Figure 4) or C—H···O (in the case of the orthorhombic polymorph) hydrogen bonding interactions into three–dimensional framework. Symmetry code: (i) 1/2-x, 1/2+y, 3/2-z.

Related literature

For general background on cocrystallization of organic compounds, see: Bernstein (2002); Desiraju (2003); Dunitz (2003); Timofeeva et al. (2003); Aakeröy et al. (2009); Lemmerer et al. (2011). For cocrystallization of 8-hydroxyquinoline with different molecules, see: Prout & Wheeler (1967); Castellano & Prout (1971); Liu & Meng (2006); Westcott et al. (2009). For crystal structure of the orthorhombic polymorph of 8-hydroxyquinoline, see: Roychowdhury et al. (1978); Banerjee & Saha (1986).

S2. Experimental

8-Hydroxiquinoline and acetaminophen were purchased from Matheson Coleman & Bell and Aldrich, respectively, and used without any further purification. 8-Hydroxyquinoline (4 mg, 27.5 mmol) and acetaminophen (4.16 mg, 27.5 mmol) were dissolved in a 1:1 chloroform–ethanol solvent mixture (3 mL). The single crystals of I were obtained by slow evaporation of the solvents at room temperature.

S3. Refinement

The hydrogen atom of the hydroxy group was localized in the difference–Fourier maps and refined isotropically with fixed displacement parameters (U_iso(H) = 1.5U_eq(O)). The other hydrogen atoms were placed in calculated positions with C—H = 0.95 Å and refined within the riding model with fixed isotropic displacement parameters U_iso(H) = 1.2U_eq(C).

Computing details

Data collection: APEX2 (Bruker, 2005); 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).

Figures

	Fig. 1. Molecular structure of I. Displacement ellipsoids are presented at the 50% probability level. H atoms are depicted as small spheres of arbitrary radius. The intramolecular O—H···N hydrogen bond is drawn by dashed line.
	Fig. 2. The centrosymmetric H–bonded dimers in the monoclinic polymorph of I. The hydrogen bonds are drawn by dashed lines.
	Fig. 3. The H–bonded dimers in the orthorhombic polymorph of I, in which the molecules are related by the twofold axis. The hydrogen bonds are drawn by dashed lines.
	Fig. 4. A portion of crystal packing of the H–bonded dimers in the monoclinic polymorph of I. The hydrogen bonds are drawn by dashed lines.

8-Hydroxyquinoline

Crystal data

C9H7NO	F(000) = 304
Mr = 145.16	Dx = 1.423 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 2841 reflections
a = 6.620 (3) Å	θ = 4.2–34.9°
b = 9.243 (4) Å	µ = 0.09 mm^−1
c = 11.070 (4) Å	T = 100 K
β = 90.718 (6)°	Prism, colourless
V = 677.3 (5) Å^3	0.30 × 0.25 × 0.20 mm
Z = 4

Data collection

Bruker APEXII CCD diffractometer	1795 independent reflections
Radiation source: fine–focus sealed tube	1494 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.023
ϕ and ω scans	θmax = 29.0°, θmin = 4.2°
Absorption correction: multi-scan (SADABS; Bruker, 2003)	h = −9→9
Tmin = 0.972, Tmax = 0.981	k = −12→12
7049 measured reflections	l = −15→15

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.039	Hydrogen site location: difference Fourier map
wR(F^2) = 0.109	H atoms treated by a mixture of independent and constrained refinement
S = 1.08	w = 1/[σ^2(Fo^2) + (0.0558P)^2 + 0.1943P] where P = (Fo^2 + 2Fc^2)/3
1795 reflections	(Δ/σ)max = 0.001
103 parameters	Δρmax = 0.39 e Å^−3
0 restraints	Δρmin = −0.20 e Å^−3

Special details

Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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 (Ų)

	x	y	z	Uiso*/Ueq
O1	0.34421 (12)	0.32417 (9)	1.07956 (7)	0.0200 (2)
H1	0.423 (2)	0.3920 (19)	1.0538 (14)	0.030*
N1	0.32084 (13)	0.48141 (10)	0.86794 (8)	0.0156 (2)
C2	0.30597 (17)	0.55312 (12)	0.76494 (10)	0.0176 (2)
H2	0.4192	0.6081	0.7398	0.021*
C3	0.13175 (17)	0.55296 (12)	0.68997 (10)	0.0180 (2)
H3	0.1291	0.6066	0.6168	0.022*
C4	−0.03295 (17)	0.47463 (11)	0.72420 (10)	0.0166 (2)
H4	−0.1519	0.4741	0.6753	0.020*
C4A	−0.02507 (15)	0.39431 (11)	0.83296 (9)	0.0139 (2)
C5	−0.18735 (16)	0.30848 (11)	0.87370 (10)	0.0161 (2)
H5	−0.3103	0.3046	0.8286	0.019*
C6	−0.16632 (16)	0.23086 (12)	0.97870 (10)	0.0168 (2)
H6	−0.2752	0.1726	1.0054	0.020*
C7	0.01393 (16)	0.23605 (12)	1.04765 (9)	0.0159 (2)
H7	0.0260	0.1805	1.1196	0.019*
C8	0.17237 (16)	0.32095 (11)	1.01141 (9)	0.0146 (2)
C8A	0.15734 (15)	0.40160 (11)	0.90195 (9)	0.0131 (2)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0147 (4)	0.0215 (4)	0.0238 (4)	−0.0034 (3)	−0.0053 (3)	0.0075 (3)
N1	0.0139 (4)	0.0140 (4)	0.0190 (5)	0.0000 (3)	0.0010 (3)	−0.0005 (3)
C2	0.0170 (5)	0.0162 (5)	0.0198 (5)	−0.0027 (4)	0.0025 (4)	0.0002 (4)
C3	0.0230 (6)	0.0165 (5)	0.0147 (5)	−0.0010 (4)	−0.0002 (4)	0.0016 (4)
C4	0.0180 (5)	0.0160 (5)	0.0158 (5)	0.0002 (4)	−0.0032 (4)	−0.0011 (4)
C4A	0.0139 (5)	0.0126 (5)	0.0152 (5)	0.0005 (4)	0.0002 (4)	−0.0021 (4)
C5	0.0134 (5)	0.0173 (5)	0.0175 (5)	−0.0016 (4)	−0.0011 (4)	−0.0019 (4)
C6	0.0147 (5)	0.0168 (5)	0.0190 (5)	−0.0031 (4)	0.0020 (4)	−0.0013 (4)
C7	0.0168 (5)	0.0156 (5)	0.0154 (5)	0.0004 (4)	0.0002 (4)	0.0013 (4)
C8	0.0133 (5)	0.0138 (5)	0.0166 (5)	0.0017 (4)	−0.0017 (4)	−0.0015 (4)
C8A	0.0122 (5)	0.0115 (4)	0.0157 (5)	0.0012 (3)	0.0008 (4)	−0.0021 (4)

Geometric parameters (Å, º)

O1—C8	1.3575 (13)	C4A—C5	1.4139 (15)
O1—H1	0.865 (17)	C4A—C8A	1.4224 (14)
N1—C2	1.3214 (14)	C5—C6	1.3716 (16)
N1—C8A	1.3667 (14)	C5—H5	0.9500
C2—C3	1.4125 (16)	C6—C7	1.4093 (15)
C2—H2	0.9500	C6—H6	0.9500
C3—C4	1.3664 (16)	C7—C8	1.3739 (15)
C3—H3	0.9500	C7—H7	0.9500
C4—C4A	1.4149 (15)	C8—C8A	1.4250 (15)
C4—H4	0.9500
C8—O1—H1	109.6 (10)	C6—C5—H5	120.2
C2—N1—C8A	117.24 (9)	C4A—C5—H5	120.2
N1—C2—C3	123.92 (10)	C5—C6—C7	121.16 (10)
N1—C2—H2	118.0	C5—C6—H6	119.4
C3—C2—H2	118.0	C7—C6—H6	119.4
C4—C3—C2	119.09 (10)	C8—C7—C6	120.38 (10)
C4—C3—H3	120.5	C8—C7—H7	119.8
C2—C3—H3	120.5	C6—C7—H7	119.8
C3—C4—C4A	119.54 (10)	O1—C8—C7	119.19 (10)
C3—C4—H4	120.2	O1—C8—C8A	120.68 (9)
C4A—C4—H4	120.2	C7—C8—C8A	120.11 (9)
C5—C4A—C4	123.08 (10)	N1—C8A—C4A	123.20 (9)
C5—C4A—C8A	119.91 (10)	N1—C8A—C8	118.01 (9)
C4—C4A—C8A	117.01 (9)	C4A—C8A—C8	118.79 (9)
C6—C5—C4A	119.63 (10)
C8A—N1—C2—C3	0.76 (16)	C2—N1—C8A—C4A	−0.76 (15)
N1—C2—C3—C4	−0.05 (17)	C2—N1—C8A—C8	178.60 (9)
C2—C3—C4—C4A	−0.66 (16)	C5—C4A—C8A—N1	179.57 (9)
C3—C4—C4A—C5	−178.83 (10)	C4—C4A—C8A—N1	0.07 (15)
C3—C4—C4A—C8A	0.64 (15)	C5—C4A—C8A—C8	0.21 (14)
C4—C4A—C5—C6	178.39 (10)	C4—C4A—C8A—C8	−179.28 (9)
C8A—C4A—C5—C6	−1.07 (15)	O1—C8—C8A—N1	0.19 (15)
C4A—C5—C6—C7	0.60 (16)	C7—C8—C8A—N1	−178.25 (9)
C5—C6—C7—C8	0.77 (16)	O1—C8—C8A—C4A	179.58 (9)
C6—C7—C8—O1	179.90 (9)	C7—C8—C8A—C4A	1.14 (15)
C6—C7—C8—C8A	−1.63 (16)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···N1	0.865 (17)	2.310 (15)	2.7596 (15)	112.5 (12)
O1—H1···N1^i	0.865 (17)	2.228 (17)	2.9072 (14)	135.3 (13)

Symmetry code: (i) −x+1, −y+1, −z+2.