Chloranilic acid: a redetermination at 100 K

doi:10.1107/S1600536810003387

Acta Crystallogr Sect E Struct Rep Online. 2010 February 1; 66(Pt 2): o497–o498.

Published online 2010 January 30. doi: 10.1107/S1600536810003387

PMCID: PMC2979702

Chloranilic acid: a redetermination at 100 K

Grzegorz Dutkiewicz,^a H. S. Yathirajan,^b Q. N. M. Hakim Al-arique,^b B. Narayana,^c and Maciej Kubicki^a^*

^aDepartment of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznań, Poland

^bDepartment of Studies in Chemistry, University of Mysore, Manasagangotri, Mysore 570 006, India

^cDepartment of Studies in Chemistry, Mangalore University, Mangalagangotri 574 199, India

Correspondence e-mail: mkubicki/at/amu.edu.pl

Received January 9, 2010; Accepted January 27, 2010.

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Abstract

The crystal structure of chloranilic acid, C₆H₂Cl₂O₄, was first described by Andersen in 1967 [Andersen, E. K. (1967). Acta Cryst. 22, 188–191] at room temperature using visually estimated intensities. Taking into account the importance of the title compound, we have redetermined the structure at 100 (1) K. The approximately planar molecule [the maximum deviation from the mean plane through the ring is 0.0014 (9) Å for the ring atoms and 0.029 (3) Å for the other atoms] occupies a special position, lying across the center of symmetry. In the crystal structure, a two-dimensional hydrogen-bonded network sustained by O—H (...)

O interactions runs approximately parallel to [101]. The two-dimensional layers are further packed in a parallel fashion, stabilized by Cl (...)

Cl interactions [Cl (...)

Cl = 3.2838 (8) Å, C—Cl (...)

Cl = 152.96 (6)°].

Related literature

For charge-transfer complexes of chloranilic acid, see: Gotoh et al. (2006

, 2007

, 2008

); Gotoh & Ishida (2009

); Ishida (2004

); Ishida & Kashino (1999

). For a recent study of the formation of either salts or co-crystals by chloranilic acid with different organic bases, see: Molčanov & Kojić-Prodić (2010

). For the previous determination of the title structure, see: Andersen (1967a

) and of its hydrate, see: Andersen (1967b

). For hydrogen-bond motifs, see: Bernstein et al. (1995

). For a description of the Cambridge Structural Database, see: (Allen, 2002

An external file that holds a picture, illustration, etc.
Object name is e-66-0o497-scheme1.jpg Object name is e-66-0o497-scheme1.jpg

Experimental

Crystal data

C₆H₂Cl₂O₄
M _r = 208.98
Monoclinic,
a = 7.5338 (12) Å
b = 5.5225 (10) Å
c = 8.5720 (12) Å
β = 104.868 (11)°
V = 344.70 (10) Å³
Z = 2
Mo Kα radiation
μ = 0.90 mm⁻¹
T = 100 K
0.3 × 0.1 × 0.1 mm

Data collection

Oxford Diffraction Xcalibur Eos diffractometer
Absorption correction: multi-scan (CrysAlis PRO; Oxford Diffraction (2009 )) T _min = 0.857, T _max = 1.000
6154 measured reflections
774 independent reflections
698 reflections with I > 2σ(I)
R _int = 0.032

Refinement

R[F ² > 2σ(F ²)] = 0.025
wR(F ²) = 0.056
S = 1.09
774 reflections
59 parameters
All H-atom parameters refined
Δρ_max = 0.37 e Å⁻³
Δρ_min = −0.27 e Å⁻³

Data collection: CrysAlis PRO (Oxford Diffraction, 2009

); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO program(s) used to solve structure: SIR92 (Altomare et al., 1993

); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008

); molecular graphics: Stereochemical Workstation Operation Manual (Siemens, 1989

); software used to prepare material for publication: SHELXL97.

Table 1

Hydrogen-bond geometry (Å, °)

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536810003387/ds2017sup1.cif

Click here to view.^{(12K, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810003387/ds2017Isup2.hkl

Click here to view.^{(38K, hkl)}

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

Acknowledgments

QNMHA thanks the University of Mysore for research facilities.

supplementary crystallographic information

Comment

The crystal structures of various charge-transfer complexes of chloranilic acid have been reported (Gotoh, Asaji et al., 2008; Gotoh, Asaji et al., 2007; Gotoh & Ishida, 2009; Gotoh, Ishikawa, et al., 2006; Ishida, 2004; Ishida & Kashino, 1999). Very recently, a study on the formation of either salts or co-crystals by chloranilic acid with the different organic bases was published (Molčanov & Kojić-Prodić, 2010).

There is a number of structures in the Cambridge Database (Allen, 2002) that contain the chloranilic acid (2,5-dichloro-3,6-dihydroxycyclohexa-2,5-diene-1,4-dione, I - Scheme 1), either as a neutral molecule or as an anion (mono- or di-). Interestingly, the only determination of the structure of the acid itself dates back to 1967 (Andersen, 1967a; hereinafter referred to as KA67). The structure was refined based on the visually estimated intensities of the diffraction spots obtained by means of the Weissenberg equi-inclination method. The quality of this structure is excellent taking into account the technology involved, but - having in mind the importance of this small molecule - thanks to the advancement of the methodology it might be desirable to get the more accurate results. Here we report the results of the structure determination of (I) at 100 (1) K. The unit cell parameters of the accompanying room temperature experiment are in an excellent agreement with the data of KA67, but the model is much better, for instance in terms of R factors (8.9% in 1967, with 22 reflections omitted vs. 2.5% in the present determination), the only symmetry independent hydrogen atom was found in the difference Fourier map in KA67 and left in the position found, while now it was isotropicaly refined, etc. Nevertheless, the basic features of the structure are similar, and both the precision and depth of the analysis in KA67 and accompanying paper on the hydrate (Andersen, 1967b) are really remarkable.

We have chosen to describe the structure in the P2₁/n space group instead of P2₁/a used in KA67, in order to have smaller β angle (104.87° instead of 122.77°); the transformation matrix is {-1 0 -1 0 1 0 1 0 0}. The molecule of I lies in the special position, across the center of symmetry (Z'=1/2). The whole molecule is planar (Fig. 1); the maximum deviation form the mean plane through 6 ring atom is 0.0014 (9) Å for the ring atom and 0.029 (3)Å for the other atoms. The bond length pattern confirms the dominant double-bond character for the bonds C3—O3 (1.224 (2) Å) and C1—C2 (1.349 (2) Å) and single-bond for C2—C3 (1.507 (2) Å) and - to the lesser extent - for C1—C3' (1.450 (2) Å).

In the crystal structure the main packing motif arises as the result of relatively strong intermolecular O—H···O hydrogen bonds, which make the antiparallel chains of molecules related by the 2₁ screw along y direction; using the graph-set notation (Bernstein et al., 1995), these first-order chains will be described as C(5). The neighboring chains are interconnected to give the centrosymmetric second-order rings R44(22) - cf. Fig. 2. These structures produce the one-molecule thick layers of molecules which expand along [101] direction, and the neighboring chains are connected by means of van der Waals interactions and probably also by weak halogen bonds, with Cl···Cl distance of 3.2838 (8)Å and C—Cl···Cl angle of 152.96 (6)° - Fig. 3.

Experimental

Chloranilic acid was purchased from Loba Chemie, Mumbai, India. X-ray quality crystals were obtained from methanol solution after slow evaporation.

Figures

Fig. 1.

Anisotropic ellipsoid representation of the compound I together with atom labelling scheme. The ellipsoids are drawn at 50% probability level, hydrogen atoms are depicted as spheres with arbitrary radii.

Fig. 2.

The hydrogen bonded motifs in the crystal structure of I. Hydrogen bonds are shown as dashed lines. (a) the N—H···N chain. Symmetry codex: (i) x,y,z; (ii) x,-3/2+y,3/2-z; (iii) 2-x,1/2+y,3/2-z; (iv) 2-x,-1/2+y,3/2-z; (v) (more ...)

Fig. 3.

Crystal packing as seen along y-direction. Hydrogen bonds and Cl···Cl contacts are shown as dashed lines.

Crystal data

C₆H₂Cl₂O₄	F(000) = 208
M_r = 208.98	D_x = 2.014 Mg m⁻³
Monoclinic, P2₁/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 4539 reflections
a = 7.5338 (12) Å	θ = 2.8–27.8°
b = 5.5225 (10) Å	µ = 0.90 mm⁻¹
c = 8.5720 (12) Å	T = 100 K
β = 104.868 (11)°	Prism, red
V = 344.70 (10) Å³	0.3 × 0.1 × 0.1 mm
Z = 2

Data collection

Oxford Diffraction Xcalibur Eos diffractometer	774 independent reflections
Radiation source: Enhance (Mo) X-ray Source	698 reflections with I > 2σ(I)
graphite	R_int = 0.032
Detector resolution: 16.1544 pixels mm^-1	θ_max = 27.9°, θ_min = 3.2°
ω–scan	h = −9→9
Absorption correction: multi-scan (CrysAlis PRO; Oxford Diffraction (2009))	k = −7→7
T_min = 0.857, T_max = 1.000	l = −11→10
6154 measured reflections

Refinement

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)] = 0.025	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.056	All H-atom parameters refined
S = 1.09	w = 1/[σ²(F_o²) + (0.0204P)² + 0.3502P] where P = (F_o² + 2F_c²)/3
774 reflections	(Δ/σ)_max < 0.001
59 parameters	Δρ_max = 0.37 e Å⁻³
0 restraints	Δρ_min = −0.27 e Å⁻³

Special details

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

	x	y	z	U_iso*/U_eq
C1	0.8496 (2)	−0.1699 (3)	0.47066 (18)	0.0102 (3)
Cl1	0.66487 (5)	−0.36207 (7)	0.44138 (4)	0.01295 (13)
C2	0.9798 (2)	−0.1990 (3)	0.38967 (18)	0.0101 (3)
O2	0.97189 (15)	−0.3741 (2)	0.28296 (13)	0.0132 (3)
H2	1.064 (3)	−0.381 (4)	0.249 (3)	0.034 (7)*
C3	1.14042 (19)	−0.0274 (3)	0.41584 (17)	0.0095 (3)
O3	1.25301 (15)	−0.0641 (2)	0.33789 (13)	0.0126 (2)

Atomic displacement parameters (Å²)

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.0081 (7)	0.0100 (8)	0.0122 (7)	−0.0022 (6)	0.0020 (6)	0.0014 (6)
Cl1	0.01094 (19)	0.0138 (2)	0.0150 (2)	−0.00495 (14)	0.00488 (13)	−0.00150 (14)
C2	0.0113 (7)	0.0081 (7)	0.0102 (7)	0.0005 (6)	0.0016 (6)	0.0013 (6)
O2	0.0121 (5)	0.0133 (6)	0.0163 (6)	−0.0014 (4)	0.0075 (5)	−0.0045 (4)
C3	0.0084 (7)	0.0103 (7)	0.0098 (7)	0.0010 (6)	0.0021 (6)	0.0041 (6)
O3	0.0121 (5)	0.0131 (6)	0.0147 (5)	0.0003 (4)	0.0072 (4)	0.0008 (4)

Geometric parameters (Å, °)

C1—C2	1.349 (2)	C2—C3	1.508 (2)
C1—C3ⁱ	1.450 (2)	O2—H2	0.82 (2)
C1—Cl1	1.7164 (15)	C3—O3	1.2240 (18)
C2—O2	1.3217 (19)

C2—C1—C3ⁱ	121.02 (14)	C1—C2—C3	120.71 (14)
C2—C1—Cl1	121.38 (12)	C2—O2—H2	112.9 (17)
C3ⁱ—C1—Cl1	117.59 (11)	O3—C3—C1ⁱ	124.53 (14)
O2—C2—C1	122.23 (14)	O3—C3—C2	117.19 (14)
O2—C2—C3	117.05 (13)	C1ⁱ—C3—C2	118.27 (13)

C3ⁱ—C1—C2—O2	−178.48 (14)	O2—C2—C3—O3	−0.8 (2)
Cl1—C1—C2—O2	0.7 (2)	C1—C2—C3—O3	−179.74 (14)
C3ⁱ—C1—C2—C3	0.4 (2)	O2—C2—C3—C1ⁱ	178.55 (13)
Cl1—C1—C2—C3	179.51 (11)	C1—C2—C3—C1ⁱ	−0.4 (2)

Symmetry codes: (i) −x+2, −y, −z+1.

Hydrogen-bond geometry (Å, °)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2···O3ⁱⁱ	0.82 (2)	2.00 (2)	2.7516 (15)	152 (2)

Symmetry codes: (ii) −x+5/2, y−1/2, −z+1/2.

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: DS2017).

References

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