Comparison of conventional and synchrotron X-ray structure deter­minations of the adduct 1,2,4,5-tetrahydroxybenzene-2,5-dihydroxy-1,4-benzoquinone (1/1) and a conventional X-ray structure determination of 1,2,4,5-tetrahydroxybenzene monohydrate

The X-ray structure of 1,2,4,5-tetra­hydroxy­benzene (benzene-1,2,4,5-tetrol) monohydrate, C₆H₆O₄·H₂O, (I), reveals columns of 1,2,4,5-tetra­hydroxy­benzene parallel to the b axis that are separated by 3.364 (12) and 3.453 (11) Å. Molecules in adjacent columns are tilted relative to each other by 27.78 (8)°. Water mol­ecules fill the channels between the columns and are involved in hydrogen-bonding interactions with the 1,2,4,5-tetra­hydroxy­benzene mol­ecules. The crystal structure of the adduct 1,2,4,5-tetra­hydroxy­benzene-2,5-di­hydroxy-1,4-benzo­quinone (1/1), C₆H₆O₄·C₆H₄O₄, (II), reveals alternating mol­ecules of 1,2,4,5-tetra­hydroxy­benzene and 2,5-di­hydroxy-1,4-benzo­quinone (both lying on inversion centers), and a zigzag hydrogen-bonded network connecting mol­ecules in three dimensions. For compound (II), the conventional X-ray determination, (IIa), is in very good agreement with the synchrotron X-ray determination, (IIb). When differences in data collection temperatures are taken into account, even the displacement parameters are in very good agreement.

S1. Comment

Derivatized porphyrins have found extensive use as models for the heme active sites of myoglobin and hemoglobin (Momenteau & Reed, 1994). Compound (I), 1,2,4,5-tetrahydroxybenzene monohydrate, was prepared as a precursor in the synthesis of elaborated porphyrins containing a benzene `cap' linked to the porphyrin by ethoxy linkages (Ma et al., 1993; Johnson et al., 1996; Slebodnick et al., 1996; Jene et al., 1999; Jene & Ibers, 2000). Compound (I) forms pale-pink crystals. The synthesis of (I) is sensitive to the initial reaction conditions and yields products that vary from these crystals to a gray-black amorphous material. All products work in the capped porphyrin synthesis. To understand these products better, we determined the structures of (I) and of the adduct 1,2,4,5-tetrahydroxybenzene-2,5-dihydroxy-1,4-benzoquinone (1/1), (II). Crystals of (II) are stable and of excellent quality. Consequently, a short wavelength (0.354 Å) data set was collected from a crystal of (II) on the Rigaku R-axis image-plate diffractometer at the Advanced Photon Source (APS). Refinement of this data set provides a check on the APS system and an interesting comparison with the results from a conventional structure determination. \sch

The asymmetric unit of compound (I) contains two half-molecules of 1,2,4,5-tetrahydroxybenzene that sit on inversion centers and two half-water molecules that sit on twofold axes (Fig. 1). Selected bond lengths and angles are listed in Table 1. The benzene rings are planar by symmetry. C≐C bond lengths in (I) reflect the fully delocalized nature of the benzene ring. The crystal structure is composed of columnar stacking and two-dimensional networks of hydrogen bonding (Fig. 2). Both unique molecules form separate columns parallel to the b axis. The first column is formed from atoms C1, C2, C3, O1, and O2 and their symmetry-generated counterparts; these are separated by 3.453 (11) Å. The second column is formed from atoms C4, C5, C6, O3, and O4 and their symmetry-generated counterparts; these are separated by 3.364 (12) Å. Molecules in different columns are tilted relative to each other by 27.78 (8)°. A ruffled two-dimensional network of hydrogen bonding exists perpendicular to the columns. Intermolecular and intramolecular hydrogen-bonding interactions are listed in Table 2. The two unique half-water molecules, containing atoms O5 and O6, fill neighboring channels of the column structure but are oriented in opposite directions. The O atoms O5 and O6 of the half-water molecules are involved in four hydrogen bonds to four molecules of 1,2,4,5-tetrahydroxybenzene in neighboring columns.

The synthesis (Jones & Shonle, 1945) and crystal structure (Semmingsen, 1977) of 2,5-dihydroxy-1,4-benzoquinone have been known for some time. In addition, dihydroxyquinones substituted at the 3,6-positions have been prepared with fluoro (Krogh Andersen & Krogh Andersen, 1975), chloro (Krogh Andersen, 1967a,b), bromo (Robl, 1987), iodo (Robl & Sheldrick, 1988), and additional hydroxy (Klug, 1965) substituents.

Molecules of 1,2,4,5-tetrahydroxybenzene and 2,5-dihydroxy-1,4-benzoquinone in compound (II) (Fig. 3) are both located on inversion centers, and the benzene and quinone portions of these molecules are planar by symmetry. These two molecules are related by pseudo symmetry if the positions of the H atoms are ignored. However, the positions of these H atoms refine well when constraints are released. The molecules are tilted relative to each other by 64.00 (5)°, as measured by their mean planes. The two kinds of molecules alternate to form two unique stacks parallel to the a axis and two unique stacks parallel to the b axis (Fig. 4). Metrical details are listed in Tables 3–6, and values for discussion are taken from Tables 5 and 6. The interplanar distances between molecules in the stacks are 2.895 (1) and 3.301 (1) Å along the a axis and 3.115 (1) and 3.304 (1) Å along the b axis. There is a three-dimensional zigzag hydrogen-bonded network in the structure.

The 2,5-dihydroxy-1,4-benzoquinone component of (II) shows pronounced quinoid character, with both short and long C—O bonds and three varied C≐C bond lengths (Tables 3 and 5). These values are similar to those reported earlier by Semmingsen (1977). The difference is an ~180° rotation of a hydroxyl group between the structures. The geometry of the 1,2,4,5-tetrahydroxybenzene component of (II) is very similar to that in (I). The exception is one hydroxyl group that is flipped by ~180° (Tables 3 and 5). This orientation precludes the possibility of intramolecular hydrogen-bonding interactions and underscores the importance of crystal-packing forces on the orientation of hydroxyl groups in compounds of this type.

For compound (II), the conventional X-ray determination, (IIa) (Tables 3 and 4), is in very good agreement with the synchrotron X-ray determination, (IIb) (Table 5 and 6). There are a few possibly significant differences, e.g. C2—C3 [1.389 (2) Å in (IIa) and 1.3953 (4) Å in (IIb)], but since (IIa) is a determination at 163 K and (IIb) at 110 K it is possible that these arise from differences in vibrational foreshortening of the bonds. In this regard, if a linear correction is applied for the differences in temperature (Debye, 1913; Dunitz et al., 1988), then generally the U^ij values from the two determinations agree within about 10%. Since, in X-ray structure determinations, it is the U^ij values that are most sensitive to a variety of systematic errors, we find this agreement very encouraging. The estimated standard deviations associated with derived quantities for (IIb) are roughly 20% of those for (IIa), in part because there are 5678 independent reflections in (IIb) and 842 in (IIa).

Crystals of (II) are dark and shiny, in sharp contrast to crystals of compound (I). The dark color probably arises from a charge-transfer interaction between molecules of 1,2,4,5-tetrahydroxybenzene acting as donors and molecules of 2,5-dihydroxy-1,4-benzoquinone acting as acceptors. Chowdhury (1961) has shown that charge-transfer interactions occur between quinones and aromatic hydrocarbons. Sakurai (1965) has proposed that the color of quinhydrone results from hydroquinone acting as the donor and quinone as the acceptor molecule. One feature of this interaction is abnormally short C···O interactions. Compound (IIb) has short C···O interactions that range from 3.097 (1)–3.241 (1) Å. The shortest of these is shorter than the 3.2 Å value reported by Sakurai (1965). It is also likely that the gray-black material often present in the synthesis of (I) is a mixture of (I) and (II), with (II) forming by partial air oxidation in solution.

Related literature

For related literature, see: Anslow & Raistrick (1939); Chowdhury (1961); Debye (1913); Dunitz et al. (1988); Jene & Ibers (2000); Jene et al. (1999); Johnson et al. (1996); Jones & Shonle (1945); Klug (1965); Krogh (1967a, 1967b); Krogh & Krogh Andersen (1975); Ma et al. (1993); Momenteau & Reed (1994); Robl (1987); Robl & Sheldrick (1988); Sakurai (1965); Semmingsen (1977); Slebodnick et al. (1996); Zaleski et al. (1998).

S2. Experimental

Crystals of compound (I) were prepared by the literature method of Anslow & Raistrick (1939) (m.p. 490–491 K). Compound (II) was prepared by allowing a small quantity of (I) to stand in D₂O. After 1 month, shiny dark crystals of (II) formed (m.p. >673 K). Melting points were measured on a Mel-Temp melting point apparatus (Laboratory Instruments, Holliston, Massachusetts).

S3. Refinement

For compound (IIb), an R-axis IV image plate detector was used in the BMB-5 beamline hutch of the DuPont-Northwestern-Dow Collaborative Access Team (DND-CAT) at the APS. The crystal-to-detector distance was 165.0 (1) mm, and the beam size was 2 mm by 2 mm. Each frame covered 6° in ϕ for 2 min. Data were collected in one group of 20 frames starting at a ϕ setting of 0°. Raw data were corrected for angular variation of the phosphor response of the image plate with a local program, following the method of Zaleski et al. (1998). For all compounds, H atoms were treated as riding, with O—H 0.83–0.84 Å and C—H 0.94–0.95 Å Query. The crystals were attached to glass fibers with a minimum of silicone cement.

Computing details

Data collection: SMART (Bruker, 1998) for (I); CAD-4 Software (Enraf-Nonius, 1993) for (IIa); HKL (Otwinowski & Minor, 1997) for (IIb). Cell refinement: SMART (Bruker, 1998) for (I); DIRAX (Duisenberg, 1992) for (IIa); HKL for (IIb). Data reduction: SAINT-Plus (Bruker, 1998) for (I); local programs for (IIa); HKL for (IIb). For all compounds, program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997a); molecular graphics: SHELXTL/PC (Sheldrick, 1997b); software used to prepare material for publication: SHELXTL/PC.

Figures

	Fig. 1. The molecular structure of (I), showing the atom-numbering scheme and with 50% displacement ellipsoids. H atoms are drawn as small spheres of arbitrary radii.
	Fig. 2. The stereoview of (I), showing columnar stacking, hydrogen-bonding interactions (dashed lines), and the water molecule orientation.
	Fig. 3. The molecular structure of (II) from the R-axis data set, i.e. (IIb), showing the atom-numbering scheme and with 50% displacement ellipsoids. H atoms are drawn as small spheres of arbitrary radii. Only unique atoms are labeled.
	Fig. 4. The stereoview for (IIb) showing columnar stacking and hydrogen-bonding interactions (dashed lines) for compound (IIB).

(I) 1,2,4,5-Tetrahydroxybenzene monohydrate

Crystal data

C6H6O4·H2O	Dx = 1.639 Mg m^−3
Mr = 160.12	Melting point = 490–491 K
Monoclinic, P2/n	Mo Kα radiation, λ = 0.71073 Å
a = 13.487 (3) Å	Cell parameters from 623 reflections
b = 3.647 (1) Å	θ = 1.9–28.3°
c = 13.506 (3) Å	µ = 0.15 mm^−1
β = 102.33 (3)°	T = 203 K
V = 649.1 (2) Å^3	Rectangular prism, pale pink
Z = 4	0.5 × 0.2 × 0.2 mm
F(000) = 336

Data collection

Bruker Smart1000 CCD diffractometer	1270 reflections with I > 2σ(I)
Radiation source: standard-focus sealed tube	Rint = 0.022
Graphite monochromator	θmax = 28.3°, θmin = 1.9°
ω scans	h = −17→13
3708 measured reflections	k = −4→4
1578 independent reflections	l = −11→18

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)] = 0.045	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.149	H-atom parameters constrained
S = 1.22	w = 1/[σ^2(Fo^2) + (0.036P)^2 + 1.0778P] where P = (Fo^2 + 2Fc^2)/3
1578 reflections	(Δ/σ)max < 0.001
116 parameters	Δρmax = 0.39 e Å^−3
0 restraints	Δρmin = −0.26 e Å^−3

Special details

Experimental. For compound (I) the crystal-to-detector distance was 5.023 cm. Each frame covered -0.3° in ω for 20 s. Data were collected in groups of 606, 435, and 230 frames at ϕ settings of 0°, 90°, and 180°, respectively. For compound (IIa) data were collected at a scan rate of 4° to 8°/minute.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O1	0.20737 (11)	0.4354 (5)	0.57575 (12)	0.0246 (4)
H1	0.2390	0.4655	0.5300	0.033 (8)*
O2	0.07215 (12)	0.2709 (5)	0.69800 (12)	0.0258 (4)
H2	0.1271	0.1621	0.7036	0.069 (13)*
O3	−0.07741 (11)	1.1076 (5)	0.79534 (11)	0.0230 (4)
H3A	−0.0308	1.1273	0.7643	0.042 (9)*
O4	0.19309 (11)	0.7111 (5)	1.06635 (12)	0.0225 (4)
H4	0.1986	0.6191	1.1235	0.044 (10)*
O5	1/4	0.3507 (7)	1/4	0.0243 (5)
H5A	0.298 (2)	0.221 (11)	0.250 (3)	0.051 (11)*
O6	1/4	0.8880 (8)	3/4	0.0261 (5)
H6A	0.251 (4)	0.738 (16)	0.692 (3)	0.102 (18)*
C1	0.10420 (16)	0.4680 (6)	0.53592 (16)	0.0190 (5)
C2	0.03826 (16)	0.3815 (6)	0.59895 (16)	0.0188 (5)
C3	−0.06586 (16)	0.4139 (6)	0.56214 (16)	0.0199 (5)
H3B	−0.1107	0.3549	0.6043	0.019 (6)*
C4	−0.03683 (16)	1.0535 (6)	0.89710 (16)	0.0176 (4)
C5	0.05936 (16)	0.9069 (6)	0.93179 (16)	0.0186 (5)
H5B	0.0993	0.8431	0.8853	0.019 (6)*
C6	0.09686 (15)	0.8541 (6)	1.03462 (16)	0.0180 (5)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0151 (7)	0.0399 (10)	0.0192 (8)	−0.0018 (7)	0.0047 (6)	0.0044 (7)
O2	0.0193 (8)	0.0400 (10)	0.0187 (8)	0.0036 (7)	0.0055 (6)	0.0094 (7)
O3	0.0171 (7)	0.0380 (10)	0.0144 (8)	0.0021 (7)	0.0048 (6)	0.0043 (7)
O4	0.0162 (7)	0.0336 (9)	0.0185 (8)	0.0060 (7)	0.0056 (6)	0.0038 (7)
O5	0.0187 (11)	0.0305 (13)	0.0232 (12)	0	0.0031 (9)	0
O6	0.0215 (11)	0.0355 (14)	0.0210 (12)	0	0.0037 (9)	0
C1	0.0150 (9)	0.0230 (11)	0.0194 (10)	−0.0008 (8)	0.0045 (8)	0.0008 (9)
C2	0.0189 (10)	0.0216 (11)	0.0158 (10)	−0.0011 (8)	0.0036 (8)	0.0016 (8)
C3	0.0179 (10)	0.0255 (12)	0.0178 (11)	−0.0017 (9)	0.0074 (8)	0.0030 (9)
C4	0.0170 (10)	0.0218 (11)	0.0144 (9)	−0.0012 (8)	0.0045 (8)	0.0012 (8)
C5	0.0166 (10)	0.0229 (11)	0.0182 (10)	0.0007 (8)	0.0082 (8)	−0.0004 (8)
C6	0.0144 (9)	0.0195 (10)	0.0202 (11)	0.0002 (8)	0.0042 (8)	0.0012 (8)

Geometric parameters (Å, º)

O1—C1	1.386 (2)	O6—H6A^ii	0.95 (5)
O1—H1	0.8300	C1—C3^iii	1.384 (3)
O2—C2	1.378 (3)	C1—C2	1.392 (3)
O2—H2	0.8300	C2—C3	1.391 (3)
O3—C4	1.381 (3)	C3—C1^iii	1.384 (3)
O3—H3A	0.8300	C3—H3B	0.9400
O4—C6	1.379 (3)	C4—C5	1.389 (3)
O4—H4	0.8300	C4—C6^iv	1.392 (3)
O5—H5A^i	0.80 (4)	C5—C6	1.386 (3)
O5—H5A	0.80 (4)	C5—H5B	0.9400
O6—H6A	0.95 (5)	C6—C4^iv	1.392 (3)
C1—O1—H1	109.5	C1^iii—C3—C2	120.7 (2)
C2—O2—H2	109.5	C1^iii—C3—H3B	119.6
C4—O3—H3A	109.5	C2—C3—H3B	119.6
C6—O4—H4	109.5	O3—C4—C5	122.27 (19)
H5A^i—O5—H5A	107 (6)	O3—C4—C6^iv	117.50 (19)
H6A—O6—H6A^ii	110 (7)	C5—C4—C6^iv	120.2 (2)
C3^iii—C1—O1	122.50 (19)	C6—C5—C4	120.41 (19)
C3^iii—C1—C2	119.9 (2)	C6—C5—H5B	119.8
O1—C1—C2	117.57 (19)	C4—C5—H5B	119.8
O2—C2—C3	118.15 (19)	O4—C6—C5	118.79 (19)
O2—C2—C1	122.5 (2)	O4—C6—C4^iv	121.84 (19)
C3—C2—C1	119.4 (2)	C5—C6—C4^iv	119.4 (2)

Symmetry codes: (i) −x+1/2, y, −z+1/2; (ii) −x+1/2, y, −z+3/2; (iii) −x, −y+1, −z+1; (iv) −x, −y+2, −z+2.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···O4^ii	0.83	1.96	2.756 (2)	160
O2—H2···O6^v	0.83	1.92	2.735 (2)	166
O3—H3A···O2^vi	0.83	1.88	2.699 (2)	169
O4—H4···O5^vii	0.83	1.96	2.767 (2)	163
O5—H5A···O3^viii	0.77 (3)	2.07 (3)	2.826 (2)	165 (3)
O6—H6A···O1	0.95 (5)	1.91 (5)	2.832 (2)	162 (3)

Symmetry codes: (ii) −x+1/2, y, −z+3/2; (v) x, y−1, z; (vi) x, y+1, z; (vii) x, y, z+1; (viii) x+1/2, −y+1, z−1/2.

(IIa) 1,2,4,5-Tetrahydroxybenzene-2,5-Dihydroxy-1,4-benzoquinone (1/1)

Crystal data

C6H6O4·C6H4O4	Dx = 1.784 Mg m^−3
Mr = 282.20	Melting point > 673 K
Monoclinic, P21/n	Cu Kα radiation, λ = 1.54178 Å
a = 7.387 (3) Å	Cell parameters from 25 reflections
b = 6.060 (1) Å	θ = 30.8–38.9°
c = 12.198 (2) Å	µ = 1.34 mm^−1
β = 105.78 (2)°	T = 163 K
V = 525.4 (3) Å^3	Rectangular prism, black
Z = 2	0.43 × 0.15 × 0.05 mm
F(000) = 292

Data collection

Enraf-Nonius CAD-4 diffractometer	753 reflections with I > 2σ(I)
Radiation source: standard-focus sealed tube	Rint = 0.021
Graphite monochromator	θmax = 63.0°, θmin = 6.3°
ω/2θ scans	h = −8→8
Absorption correction: analytical face-indexed (de Meulenaer & Tompa, 1965)	k = −6→6
Tmin = 0.877, Tmax = 0.938	l = −14→14
3379 measured reflections	6 standard reflections every 100 reflections
842 independent reflections	intensity decay: <2%

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)] = 0.035	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.114	H-atom parameters constrained
S = 1.14	w = 1/[σ^2(Fo^2) + (0.0694P)^2 + 0.1389P] where P = (Fo^2 + 2Fc^2)/3
842 reflections	(Δ/σ)max < 0.001
94 parameters	Δρmax = 0.19 e Å^−3
0 restraints	Δρmin = −0.25 e Å^−3

Special details

Experimental. For compound (I) the crystal-to-detector distance was 5.023 cm. Each frame covered -0.3° in ω for 20 s. Data were collected in groups of 606, 435, and 230 frames at ϕ settings of 0°, 90°, and 180°, respectively. For compound (IIa) data were collected at a scan rate of 4° to 8°/minute.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O1	0.98007 (14)	0.55646 (16)	−0.22730 (7)	0.0146 (4)
H1	0.9384	0.4434	−0.2657	0.017*
O2	0.82695 (13)	0.15885 (16)	0.08177 (7)	0.0131 (4)
H3	0.7812	0.0663	0.0305	0.016*
O3	0.99530 (13)	−0.06305 (16)	0.27657 (7)	0.0140 (4)
H5	0.9471	0.0412	0.2329	0.017*
O4	1.16048 (13)	−0.34700 (15)	0.43160 (7)	0.0133 (4)
C1	0.98734 (18)	0.5200 (2)	−0.11557 (11)	0.0106 (4)
C2	0.90043 (19)	0.3446 (2)	−0.07742 (11)	0.0114 (4)
H2	0.8324	0.2384	−0.1299	0.014*
C3	0.91311 (18)	0.3248 (2)	0.03786 (11)	0.0112 (4)
C4	0.90720 (19)	0.1594 (2)	0.41533 (11)	0.0116 (4)
H4	0.8454	0.2656	0.3606	0.014*
C5	0.98966 (18)	−0.0161 (2)	0.38227 (11)	0.0111 (4)
C6	1.08814 (18)	−0.1877 (2)	0.46676 (11)	0.0114 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0228 (6)	0.0131 (6)	0.0076 (6)	−0.0044 (4)	0.0037 (4)	−0.0018 (4)
O2	0.0179 (6)	0.0105 (6)	0.0107 (5)	−0.0049 (4)	0.0038 (4)	−0.0010 (4)
O3	0.0209 (6)	0.0131 (6)	0.0078 (6)	0.0041 (4)	0.0036 (4)	0.0013 (4)
O4	0.0161 (6)	0.0111 (6)	0.0127 (6)	0.0029 (4)	0.0040 (4)	−0.0010 (4)
C1	0.0116 (7)	0.0107 (7)	0.0095 (7)	0.0026 (5)	0.0030 (5)	0.0004 (5)
C2	0.0105 (7)	0.0116 (8)	0.0112 (7)	0.0002 (5)	0.0013 (5)	−0.0026 (5)
C3	0.0099 (7)	0.0093 (8)	0.0146 (7)	0.0013 (5)	0.0035 (6)	0.0013 (5)
C4	0.0109 (7)	0.0114 (8)	0.0115 (7)	0.0001 (5)	0.0011 (5)	0.0027 (5)
C5	0.0113 (7)	0.0116 (7)	0.0100 (7)	−0.0028 (5)	0.0024 (5)	−0.0001 (5)
C6	0.0088 (7)	0.0104 (8)	0.0148 (8)	−0.0027 (5)	0.0029 (6)	−0.0008 (5)

Geometric parameters (Å, º)

O1—C1	1.3671 (16)	C2—C3	1.3887 (19)
O1—H1	0.8400	C2—H2	0.9500
O2—C3	1.3742 (17)	C3—C1^i	1.394 (2)
O2—H3	0.8400	C4—C5	1.341 (2)
O3—C5	1.3320 (16)	C4—C6^ii	1.4395 (19)
O3—H5	0.8400	C4—H4	0.9500
O4—C6	1.2355 (17)	C5—C6	1.505 (2)
C1—C2	1.386 (2)	C6—C4^ii	1.4395 (19)
C1—C3^i	1.394 (2)
C1—O1—H1	109.5	C2—C3—C1^i	120.52 (12)
C3—O2—H3	109.5	C5—C4—C6^ii	120.36 (12)
C5—O3—H5	109.5	C5—C4—H4	119.8
O1—C1—C2	124.22 (12)	C6^ii—C4—H4	119.8
O1—C1—C3^i	116.06 (12)	O3—C5—C4	126.65 (13)
C2—C1—C3^i	119.71 (13)	O3—C5—C6	112.26 (12)
C1—C2—C3	119.77 (12)	C4—C5—C6	121.10 (13)
C1—C2—H2	120.1	O4—C6—C4^ii	123.02 (12)
C3—C2—H2	120.1	O4—C6—C5	118.44 (12)
O2—C3—C2	123.18 (12)	C4^ii—C6—C5	118.54 (12)
O2—C3—C1^i	116.29 (12)

Symmetry codes: (i) −x+2, −y+1, −z; (ii) −x+2, −y, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···O4^iii	0.84	2.04	2.737 (1)	140
O2—H3···O4^iv	0.84	1.85	2.686 (2)	172
O3—H5···O2	0.84	1.95	2.719 (1)	152

Symmetry codes: (iii) −x+2, −y, −z; (iv) x−1/2, −y−1/2, z−1/2.

(IIb) 1,2,4,5-Tetrahydroxybenzene-2,5-Dihydroxy-1,4-benzoquinone (1/1)

Crystal data

C6H6O4·C6H4O4	Dx = 1.783 Mg m^−3
Mr = 282.20	Melting point > 673 K
Monoclinic, P21/n	Synchrotron radiation, λ = 0.35400 Å
a = 7.382 (1) Å	Cell parameters from 4909 reflections
b = 6.065 (1) Å	θ = 2.6–25.9°
c = 12.197 (1) Å	µ = 0.09 mm^−1
β = 105.778 (1)°	T = 110 K
V = 525.51 (12) Å^3	Rectangular prism, black
Z = 2	1.12 × 0.33 × 0.20 mm
F(000) = 292

Data collection

R-axis IV image plate diffractometer	4908 reflections with I > 2σ(I)
Radiation source: white-beam	Rint = 0.032
Silicon crystal monochromator	θmax = 25.9°, θmin = 2.6°
ϕ scans	h = −14→16
13465 measured reflections	k = −12→12
5678 independent reflections	l = −25→23

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)] = 0.031	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.113	H-atom parameters constrained
S = 1.04	w = 1/[σ^2(Fo^2) + (0.0738P)^2 + 0.021P] where P = (Fo^2 + 2Fc^2)/3
5678 reflections	(Δ/σ)max = 0.001
94 parameters	Δρmax = 0.58 e Å^−3
0 restraints	Δρmin = −0.48 e Å^−3

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O1	0.98001 (3)	0.55561 (4)	−0.227606 (18)	0.01002 (4)
H1	0.9364	0.4433	−0.2660	0.012*
O2	0.82605 (3)	0.15883 (3)	0.081429 (18)	0.00871 (4)
H3	0.7803	0.0668	0.0299	0.010*
O3	0.99517 (3)	−0.06236 (4)	0.276231 (17)	0.00943 (4)
H5	0.9432	0.0400	0.2325	0.011*
O4	1.16100 (3)	−0.34706 (3)	0.431529 (19)	0.00904 (4)
C1	0.98744 (3)	0.51993 (4)	−0.11610 (2)	0.00659 (4)
C2	0.89983 (3)	0.34416 (4)	−0.07772 (2)	0.00687 (4)
H2	0.8317	0.2380	−0.1302	0.008*
C3	0.91252 (3)	0.32451 (4)	0.03811 (2)	0.00647 (4)
C4	0.90645 (3)	0.16006 (4)	0.41520 (2)	0.00727 (4)
H4	0.8443	0.2663	0.3606	0.009*
C5	0.98999 (3)	−0.01676 (4)	0.38190 (2)	0.00670 (4)
C6	1.08821 (3)	−0.18730 (4)	0.46649 (2)	0.00667 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.01595 (8)	0.00875 (7)	0.00538 (7)	−0.00306 (5)	0.00295 (5)	−0.00055 (5)
O2	0.01211 (7)	0.00630 (7)	0.00769 (7)	−0.00365 (4)	0.00263 (5)	0.00007 (5)
O3	0.01430 (8)	0.00847 (7)	0.00566 (7)	0.00250 (5)	0.00292 (5)	0.00026 (5)
O4	0.01214 (7)	0.00651 (7)	0.00835 (7)	0.00341 (4)	0.00257 (5)	−0.00059 (5)
C1	0.00846 (8)	0.00568 (7)	0.00551 (7)	−0.00122 (5)	0.00172 (5)	−0.00042 (5)
C2	0.00855 (8)	0.00569 (8)	0.00614 (8)	−0.00173 (5)	0.00160 (5)	−0.00084 (5)
C3	0.00780 (8)	0.00514 (7)	0.00639 (7)	−0.00132 (4)	0.00179 (5)	−0.00024 (5)
C4	0.00935 (8)	0.00606 (8)	0.00627 (7)	0.00220 (5)	0.00192 (5)	0.00090 (5)
C5	0.00854 (8)	0.00576 (7)	0.00570 (7)	0.00117 (5)	0.00176 (5)	0.00032 (5)
C6	0.00803 (8)	0.00531 (7)	0.00655 (8)	0.00132 (5)	0.00178 (5)	0.00012 (5)

Geometric parameters (Å, º)

O1—C1	1.3635 (3)	C2—C3	1.3953 (4)
O1—H1	0.8400	C2—H2	0.9500
O2—C3	1.3710 (3)	C3—C1^i	1.3994 (4)
O2—H3	0.8400	C4—C5	1.3533 (4)
O3—C5	1.3289 (3)	C4—C6^ii	1.4423 (4)
O3—H5	0.8400	C4—H4	0.9500
O4—C6	1.2386 (3)	C5—C6	1.5011 (4)
C1—C2	1.3923 (4)	C6—C4^ii	1.4423 (4)
C1—C3^i	1.3994 (4)
C1—O1—H1	109.5	C2—C3—C1^i	120.55 (2)
C3—O2—H3	109.5	C5—C4—C6^ii	120.02 (2)
C5—O3—H5	109.5	C5—C4—H4	120.0
O1—C1—C2	124.09 (2)	C6^ii—C4—H4	120.0
O1—C1—C3^i	116.21 (2)	O3—C5—C4	126.27 (2)
C2—C1—C3^i	119.69 (2)	O3—C5—C6	112.78 (2)
C1—C2—C3	119.76 (2)	C4—C5—C6	120.94 (2)
C1—C2—H2	120.1	O4—C6—C4^ii	122.52 (2)
C3—C2—H2	120.1	O4—C6—C5	118.44 (2)
O2—C3—C2	122.87 (2)	C4^ii—C6—C5	119.04 (2)
O2—C3—C1^i	116.56 (2)

Symmetry codes: (i) −x+2, −y+1, −z; (ii) −x+2, −y, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···O4^iii	0.84	2.04	2.7316 (4)	140
O2—H3···O4^iv	0.84	1.85	2.6816 (4)	171
O3—H5···O2	0.84	1.95	2.7186 (3)	152

Symmetry codes: (iii) −x+2, −y, −z; (iv) x−1/2, −y−1/2, z−1/2.