Hydrogen bonding in the inner-salt zwitterion and in two different charged forms of 5,6-bis(2-pyridyl)pyrazine-2,3-dicarboxylic acid

5,6-Bis(2-pyridyl)­pyrazine-2,3-di­carboxyl­ic acid exists as an inner-salt zwitterion, 3-carboxy-5-(2-pyridinio)-6-(2-pyridyl)­pyrazine-2-carboxyl­ate, (Ia), C₁₆H₁₀N₄O₄. The adjacent pyridine and pyridinium rings are almost coplanar due to the presence of an intramolecular hydrogen bond involving the pyridine N atom and the NH H atom of the pyridinium group. In the crystal of (Ia), symmetry-related mol­ecules are hydrogen bonded via the carboxyl­ic acid OH group and one of the carboxyl­ate O atoms to form a polymer, which exhibits a channel-type structure. In the HCl, HClO₄ and HPF₆ salts, 6-­carboxy-5-carboxyl­ato­pyrazine-2,3-diyldi-2-pyridinium chloride 2.25-hydrate, (II), C₁₆H₁₁N₄O₄⁺·Cl^-·2.25H₂O, 6-­carboxy-5-carboxyl­ato­pyrazine-2,3-diyldi-2-pyridinium perchlor­ate trihydrate, (IIIa), C₁₆H₁₁N₄O₄⁺·ClO₄^-·3H₂O, and 6-car­boxy-5-carboxyl­ato­pyrazine-2,3-diyldi-2-pyridinium hexa­fluoro­phosphate trihydrate, (IIIb), C₁₆H₁₁N₄O₄⁺·PF₆^-·3H₂O, both pyridine rings are protonated. In the perchlorate form, and in the isomorphous hexa­fluoro­phosphate form, the mol­ecule possesses C₂ symmetry, with has a symmetrical intramolecular hydrogen bond involving the adjacent carboxyl­ate and carboxyl­ic acid substituents. In the crystals of the chloride and perchlorate (or hexa­fluoro­phosphate) salts, hydrogen-bonded polymers are formed which are three-dimensional and one-dimensional, respectively.

S1. Comment

The potentially bis-tridentate coordinating ligand 5,6-bis(2-pyridyl)pyrazine-2,3-dicarboxylic acid, (I), was synthesized in order to study its coordination behaviour with transition metals, and it does indeed exhibit a highly diverse coordination geometry. At least eight different coordination modes have been observed in the formation of mononuclear, binuclear and polymeric coordination complexes (Alfonso et al., 2001). A prominent characteristic of this compound is its amphoteric character. It can exist as an inner salt zwitterion, (Ia), and as different charged species, for example as in the chloride 2.25 hydrate, (II), or the perchlorate and hexafluorophosphate trihydrate salts, (IIIa) and (IIIb), as shown in the Scheme. \sch

When recrystallized from water, compound (I) exists as the inner-salt zwitterion, (Ia) (Fig. 1). As a result of an intramolecular hydrogen bond involving the pyridinium N⁺—H and the pyridine N atoms, the adjacent pyridine (py) rings are almost coplanar with the central pyrazine (pz) ring, with a pyH-to-pz dihedral angle of 4.3 (1)° and a py-to-pz dihedral angle of 7.9 (1)°. The N atoms are separated by 2.528 (3) Å, and this rather short intramolecular hydrogen bond [N3—H3 1.22 (3) and H3···N4 1.32 (3) Å, and N3—H3···N4 167 (3)°; Table 1] leads to a slight twist of the pyrazine ring (plane C1/N1/C4 to plane C2/N2/C3) of 3.6 (4)°, as well as to two unusually large exocyclic angles, C3—C4—C5 [131.0 (3)°] and C4—C3—C10 [131.2 (2)°]. This type of hydrogen-bond, with almost identical bond distances and angles, was also found in the diprotonated form of tetra(2-pyridyl)pyrazine by Bock et al. (1992) and analysed theoretically. An analysis of hydrogen bonding in organoammonium H(N) atoms of this type has been made by Robertson et al. (1998).

The carboxylate group (C16/O3/O4) and the carboxylic acid group (C15/O1/O2) are rotated out of the plane of the pyrazine ring. They are inclined to one another by 59.5 (3)°, and to the pyrazine ring by 37.9 (1) and 58.3 (2)°, respectively. In the crystal of (Ia), symmetry-related molecules are hydrogen bonded via the carboxylic acid OH group and one of the carboxylate O atoms (Table 1). This results in the formation of a one-dimensional polymer with a channel-type structure (Fig. 2). A similar strong intermolecular O—H.·O hydrogen bond, with almost identical bond distances and angles, has been observed previously in caesium trihydrogen diphthalate (Krol et al., 1983).

Recrystallization of (Ia) from 1M HCl yielded colourless single crystals of (II) (Fig. 3). Here, both of the pyridine rings are protonated and they are both rotated by ca 180° from their positions in (Ia). They are inclined to one another by 65.6 (1)°, and by 49.2 (1)° (N3/C5—C9) and 30.8 (1)° (N4/C10—C14) to the pyrazine ring. This places the pyridine N atoms slightly above and below the plane of the pyrazine ring, which is twisted by 4.9 (2)° (plane C1/N1/C4 to plane C2/N2/C3). The carboxylic acid group (C15/O1/O2) is out of the plane of the pyrazine ring by 75.7 (1)°, compared with 58.3 (1)° in (Ia). The carboxylate group (C16/O3/O4) is inclined to the pyrazine ring by only 15.3 (3)°, compared with 37.9 (1)° in (Ia).

This triprotonated form, (II), also differs from (Ia) in the type of hydrogen bonding. There are no intramolecular hydrogen bonds in the crystal structure of (II). However, symmetry-related molecules are linked by hydrogen bonds to form a three-dimensional hydrogen-bonded network. This involves the N atoms of both protonated pyridine rings, the O atoms of the carboxylate, the OH of the carboxylic acid, the lattice water molecules and the Cl^- anion, which participates in four hydrogen-bond interactions. Details are given in Table 2 and Fig. 4.

A second triprotonated form, (IIIa), was obtained on slow evaporation of a solution of (Ia) in 1M HClO₄. Compound (IIIa) possesses C₂ symmetry and its structure differs significantly from that of (Ia) (Fig. 5). Here again, both pyridine rings are protonated and are twisted out of the plane of the pyrazine ring by 34.8 (1)°, and inclined to one another by 62.2 (1)°. The carboxylate and carboxylic acid groups are both inclined to the pyrazine plane by 19.7 (3)° and to one another by 5.2 (4)°. This arrangement is the result of the presence of a strong symmetrical intramolecular hydrogen bond (Table 3). This type of symmetrical hydrogen bond has been observed previously in pyrazine-2,3-dicarboxylic acid 3-amino-1,2,4-triazole (Lynch et al., 1994) and in bis[dihydrogen 1,2,4,5-benzenetetracarboxylate(2-)] (Karanović et al., 1999). It is interesting to note that the deviation from planarity of the pyrazine ring is larger than in (Ia) or (II), with a twist angle of 9.6 (4)°. In the crystal, the C₁₆H₁₁N₄O₄⁺ cations and the lattice water form a one-dimensional hydrogen-bonded polymer, separated by the disordered perchlorate anions. Details are given in Table 3 and Fig. 6.

From the reaction of (Ia) with Ag[PF₆] in water, a silver complex was not obtained, but slow evaporation of the solution gave crystals of (IIIb) (Fig. 7), which proved to be isomorphous with (IIIa). The structural details for (IIIb) are very similar to those observed for (IIIa). Details concerning the hydrogen bonding are given in Table 4 and Fig. 8.

S2. Experimental

Compound (Ia) was prepared by adding 2,3-bis(2-pyridyl)quinoxaline (5.7 g, 20 mmol; Goodwin & Lions, 1959) to water (450 ml). This solution was heated to 368 K with stirring. KMnO₄ (25 g, 0.16 mol) was then added in small portions over a period of 2 h. The reaction mixture was stirred for 1 h and the temperature reduced to 348 K. Ethanol (10 ml) was added to remove the excess KMnO₄. The reaction mixture was filtered to give a colourless filtrate, which was concentrated to 20 ml and acidified with 4M HCl until a white precipitate formed. The crude product was dissolved in water (15 ml) and the solution was acidified again with concentrated HCl to yield a white solid. The product, (Ia), was filtered off, washed with ethanol, recrystallized from water and dried under vacuum (yield 3.9 g, 60.5%; m.p. 533–534 K). Analysis calculated for C₁₆H₁₀N₄O₄: C 59.6, H 3.1, N 17.4%; found: C 59.5, H 3.0, N 17.3%. Selected IR bands (KBr, cm^-1): 3426 (br, m), 3083 (w), 3026 (w), 2922 (w), 2854 (w), 1706 (m), 1653 (m), 1602 (versus), 1488 (s), 1433 (m), 1337 (m), 1268 (s), 1148 (s), 1115 (s), 1083 (s), 1040 (m), 943 (m), 865 (m), 820 (w), 793 (versus), 743 (s); ¹H NMR (D₂O, 200 MHz, δ, p.p.m.): 8.84–8.82 (m, 2H, PyH), 8.46–8.37 (m, 2H, PyH), 8.08–7.99 (m, 4H, PyH); ¹³C NMR (D₂O, 50 MHz, δ, p.p.m): 170.2, 150.2, 148.3, 148.1, 147.8, 147.4, 130.6, 130.3; DCI-MS (DCI is?) (m/z): 323 (MH⁺, 4), 322 (M⁺, 2). Compound (II) was obtained by dissolving (Ia) in a 1M HCl aqueous solution, which on slow evaporaton gave colourless rod-like crystals. Compound (IIIa) was obtained by dissolving (Ia) in a 1M HClO₄ aqueous solution, which on slow evaporation yielded pale-yellow block-like crystals. Compound (IIIb) was obtained by dissolving (Ia) in an aqueous solution of Ag[PF₆]. On slow evaporation, pale-yellow block-like crystals were obtained.

S3. Refinement

The H atoms were located from difference Fourier maps and refined isotropically. The pyNH and CO₂H H atoms were all located from difference maps and refined isotropically. For compounds (Ia) and (II), the hydrogen bonds involving these H atoms are of the unusual symmetric type, hence the long N—H, H···N, O—H and O···H distances. This type of hydrogen bond, N—H···N for example, with identical bond distances and angles, has been observed previously and analysed theoretically by Bock et al. (1992). In compound (II), water molecules O2W and O3W are the same atom but disordered over two sites, with refined occupancies of 0.62 and 0.38. In compound (IIIa), the perchlorate anion possesses C₂ symmetry and the O atoms, O12, O13 and O14, are disordered. In some cases, the water H atoms could be located from difference Fourier maps and were refined isotropically. When the refinement was unstable in the final cycles of refinement they were held fixed, as for water O4W in (II) and O2W in (IIIa) and (IIIb) (U_iso = 0.1 Ų).

Computing details

Data collection: STADI4 (Stoe & Cie, 1997) for (Ia); EXPOSE (Stoe & Cie, 2000) for (II), (IIIa), (IIIb). Cell refinement: STADI4 for (Ia); CELL (Stoe & Cie, 2000) for (II), (IIIa), (IIIb). Data reduction: X-RED in STADI4 for (Ia); INTEGRATE (Stoe & Cie, 2000) for (II), (IIIb); X-RED in STADI4 (Stoe & Cie, 1997) for (IIIa). For all compounds, program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON99 (Spek, 1990); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. The molecular structure of (Ia) showing the atom-numbering scheme and with displacement ellipsoids at the 50% probability level. H atoms are shown as small spheres of arbitrary radii.
	Fig. 2. The crystal packing of (Ia) viewed down the c axis. The hydrogen bonding is shown as dashed lines [symmetry code as in Table 1].
	Fig. 3. The molecular structure of (II) showing the atom-numbering scheme and with displacement ellipsoids at the 50% probability level. H atoms are shown as small spheres of arbitrary radii.
	Fig. 4. The crystal packing of (II) viewed down the b axis. The hydrogen bonding is shown as dashed lines [symmetry codes as in Table 2].
	Fig. 5. The molecular structure of (IIIa) showing the atom-numbering scheme and with displacement ellipsoids at the 50% probability level. H atoms are shown as small spheres of arbitrary radii.
	Fig. 6. Part of the crystal packing of (IIIa) viewed down the a axis. The hydrogen bonding, which extends in both the a and c directions, is shown as dashed lines [symmetry codes as in Table 3].
	Fig. 7. The molecular structure of (IIIb) showing the atom-numbering scheme and with displacement ellipsoids at the 50% probability level. H atoms are shown as small spheres of arbitrary radii.
	Fig. 8. Part of the crystal packing of (IIIb) viewed down the a axis. The hydrogen bonding, which extends in both the a and the c directions, is shown as dashed lines [symmetry codes as in Table 4].

(Ia) 3-Carboxy-5-(2-pyridinio)-6-(2-pyridyl)pyrazine-2-carboxylate

Crystal data

C16H10N4O4	F(000) = 664
Mr = 322.28	Dx = 1.599 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 10.477 (1) Å	Cell parameters from 20 reflections
b = 13.523 (2) Å	θ = 14–19°
c = 10.058 (1) Å	µ = 0.12 mm^−1
β = 110.07 (1)°	T = 293 K
V = 1338.5 (3) Å^3	Plate, pale yellow
Z = 4	0.46 × 0.30 × 0.11 mm

Data collection

Stoe four-circle diffractometer	Rint = 0.039
Radiation source: fine-focus sealed tube	θmax = 25.0°, θmin = 2.1°
Graphite monochromator	h = 0→12
2θ/ω scans	k = −16→0
2356 measured reflections	l = −11→11
2336 independent reflections	3 standard reflections every 60 min
1227 reflections with I > 2σ(I)	intensity decay: <2%

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.049	All H-atom parameters refined
wR(F^2) = 0.092	w = 1/[σ^2(Fo^2) + (0.029P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 0.90	(Δ/σ)max < 0.001
2336 reflections	Δρmax = 0.17 e Å^−3
258 parameters	Δρmin = −0.20 e Å^−3
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.014 (2)

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq
O1	−0.0606 (2)	0.16027 (19)	0.7237 (2)	0.0590 (7)
O2	−0.1543 (2)	0.26898 (18)	0.5480 (2)	0.0416 (6)
O3	−0.2703 (2)	0.07332 (17)	0.3870 (2)	0.0471 (7)
O4	−0.26759 (19)	0.13092 (17)	0.1812 (2)	0.0417 (6)
N1	0.1355 (2)	0.16093 (19)	0.5751 (2)	0.0360 (7)
N2	0.0163 (2)	0.10376 (19)	0.2992 (2)	0.0350 (7)
N3	0.4589 (2)	0.12789 (19)	0.5341 (2)	0.0374 (7)
N4	0.3489 (2)	0.09486 (19)	0.2720 (3)	0.0355 (7)
C1	0.0013 (3)	0.1570 (2)	0.5164 (3)	0.0334 (8)
C2	−0.0600 (3)	0.1244 (2)	0.3771 (3)	0.0319 (8)
C3	0.1531 (3)	0.1131 (2)	0.3540 (3)	0.0291 (8)
C4	0.2148 (3)	0.1377 (2)	0.4983 (3)	0.0309 (8)
C5	0.3616 (3)	0.1443 (2)	0.5897 (3)	0.0312 (7)
C6	0.3982 (3)	0.1669 (3)	0.7323 (3)	0.0415 (9)
C7	0.5345 (3)	0.1726 (3)	0.8139 (4)	0.0449 (9)
C8	0.6322 (3)	0.1562 (3)	0.7545 (3)	0.0415 (9)
C9	0.5914 (3)	0.1339 (3)	0.6132 (3)	0.0396 (9)
C10	0.2126 (3)	0.0967 (2)	0.2395 (3)	0.0328 (8)
C11	0.1310 (3)	0.0839 (3)	0.0996 (3)	0.0427 (9)
C12	0.1874 (3)	0.0685 (3)	−0.0032 (4)	0.0474 (10)
C13	0.3273 (3)	0.0655 (3)	0.0342 (3)	0.0429 (9)
C14	0.4054 (3)	0.0804 (3)	0.1723 (3)	0.0420 (9)
C15	−0.0765 (3)	0.1949 (3)	0.6078 (3)	0.0383 (9)
C16	−0.2119 (3)	0.1083 (2)	0.3103 (3)	0.0335 (8)
H2O	−0.200 (4)	0.315 (3)	0.623 (4)	0.095 (13)*
H3N	0.419 (3)	0.112 (2)	0.407 (3)	0.071 (11)*
H6	0.326 (3)	0.171 (2)	0.768 (3)	0.044 (9)*
H7	0.561 (2)	0.1891 (19)	0.912 (3)	0.028 (8)*
H8	0.723 (3)	0.1572 (19)	0.805 (3)	0.025 (8)*
H9	0.659 (3)	0.120 (2)	0.560 (3)	0.059 (10)*
H11	0.034 (3)	0.087 (2)	0.074 (3)	0.056 (10)*
H12	0.127 (3)	0.059 (2)	−0.104 (3)	0.063 (10)*
H13	0.368 (3)	0.052 (2)	−0.035 (3)	0.039 (9)*
H14	0.515 (3)	0.076 (2)	0.207 (3)	0.065 (10)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0600 (16)	0.088 (2)	0.0356 (14)	0.0218 (15)	0.0250 (12)	0.0141 (14)
O2	0.0344 (13)	0.0594 (17)	0.0292 (13)	0.0129 (12)	0.0088 (11)	−0.0012 (12)
O3	0.0373 (13)	0.0647 (18)	0.0432 (13)	−0.0069 (12)	0.0188 (11)	0.0060 (13)
O4	0.0267 (12)	0.0652 (17)	0.0311 (13)	−0.0086 (11)	0.0073 (10)	0.0025 (12)
N1	0.0257 (15)	0.0509 (19)	0.0301 (15)	0.0025 (13)	0.0079 (12)	0.0009 (13)
N2	0.0279 (15)	0.0460 (19)	0.0315 (14)	0.0005 (12)	0.0109 (12)	−0.0058 (13)
N3	0.0264 (16)	0.057 (2)	0.0270 (14)	−0.0026 (13)	0.0068 (12)	−0.0029 (14)
N4	0.0258 (15)	0.0508 (19)	0.0292 (15)	−0.0008 (13)	0.0086 (12)	−0.0044 (13)
C1	0.0287 (17)	0.044 (2)	0.0300 (17)	0.0042 (16)	0.0130 (14)	0.0040 (16)
C2	0.0282 (17)	0.035 (2)	0.0336 (18)	0.0023 (15)	0.0127 (14)	0.0007 (15)
C3	0.0257 (17)	0.033 (2)	0.0292 (17)	−0.0005 (14)	0.0098 (14)	−0.0034 (15)
C4	0.0229 (16)	0.036 (2)	0.0336 (17)	0.0007 (14)	0.0092 (14)	0.0017 (15)
C5	0.0289 (18)	0.034 (2)	0.0304 (17)	−0.0001 (15)	0.0094 (14)	0.0016 (15)
C6	0.033 (2)	0.057 (3)	0.035 (2)	0.0019 (17)	0.0117 (17)	0.0005 (18)
C7	0.039 (2)	0.062 (3)	0.0295 (19)	0.0001 (18)	0.0064 (17)	−0.0061 (19)
C8	0.0265 (19)	0.054 (2)	0.037 (2)	−0.0026 (18)	0.0015 (16)	0.0003 (18)
C9	0.0227 (18)	0.056 (3)	0.0390 (19)	−0.0007 (16)	0.0095 (16)	0.0018 (18)
C10	0.0275 (18)	0.040 (2)	0.0319 (18)	0.0013 (15)	0.0112 (14)	0.0005 (16)
C11	0.0285 (19)	0.065 (3)	0.0338 (19)	0.0040 (18)	0.0101 (17)	−0.0053 (17)
C12	0.035 (2)	0.074 (3)	0.032 (2)	0.0027 (19)	0.0102 (17)	−0.0065 (19)
C13	0.045 (2)	0.057 (3)	0.034 (2)	0.0038 (18)	0.0224 (18)	−0.0040 (18)
C14	0.0323 (19)	0.058 (3)	0.041 (2)	0.0000 (18)	0.0197 (17)	−0.0051 (18)
C15	0.0217 (18)	0.057 (3)	0.0338 (19)	−0.0012 (17)	0.0067 (15)	−0.0041 (18)
C16	0.0276 (17)	0.038 (2)	0.0385 (19)	0.0002 (15)	0.0163 (16)	−0.0019 (16)

Geometric parameters (Å, º)

O1—C15	1.214 (3)	C3—C10	1.502 (4)
O2—C15	1.301 (4)	C4—C5	1.499 (4)
O2—H2O	1.20 (4)	C5—C6	1.386 (4)
O3—C16	1.231 (3)	C6—C7	1.383 (4)
O4—C16	1.265 (3)	C6—H6	0.94 (3)
N1—C1	1.326 (4)	C7—C8	1.368 (4)
N1—C4	1.352 (3)	C7—H7	0.96 (2)
N2—C2	1.327 (3)	C8—C9	1.370 (4)
N2—C3	1.354 (3)	C8—H8	0.91 (2)
N3—C5	1.338 (3)	C9—H9	1.03 (3)
N3—C9	1.345 (3)	C10—C11	1.384 (4)
N3—H3N	1.22 (3)	C11—C12	1.372 (4)
N4—C14	1.342 (3)	C11—H11	0.95 (3)
N4—C10	1.351 (3)	C12—C13	1.383 (4)
N4—H3N	1.32 (3)	C12—H12	1.00 (3)
C1—C2	1.398 (4)	C13—C14	1.364 (4)
C1—C15	1.512 (4)	C13—H13	0.95 (3)
C2—C16	1.516 (4)	C14—H14	1.08 (3)
C3—C4	1.411 (4)
C15—O2—H2O	115.4 (17)	C6—C7—H7	119.8 (15)
C1—N1—C4	120.2 (2)	C7—C8—C9	118.4 (3)
C2—N2—C3	120.6 (2)	C7—C8—H8	123.2 (16)
C5—N3—C9	121.5 (3)	C9—C8—H8	118.4 (16)
C5—N3—H3N	115.7 (14)	N3—C9—C8	121.2 (3)
C9—N3—H3N	122.7 (14)	N3—C9—H9	115.6 (16)
C14—N4—C10	121.5 (3)	C8—C9—H9	123.2 (16)
C14—N4—H3N	123.8 (13)	N4—C10—C11	118.5 (3)
C10—N4—H3N	114.6 (13)	N4—C10—C3	120.0 (2)
N1—C1—C2	120.7 (3)	C11—C10—C3	121.6 (3)
N1—C1—C15	115.3 (3)	C12—C11—C10	120.6 (3)
C2—C1—C15	123.9 (3)	C12—C11—H11	119.6 (17)
N2—C2—C1	119.7 (3)	C10—C11—H11	119.8 (17)
N2—C2—C16	117.5 (3)	C11—C12—C13	119.4 (3)
C1—C2—C16	122.8 (3)	C11—C12—H12	119.6 (17)
N2—C3—C4	119.2 (3)	C13—C12—H12	121.1 (17)
N2—C3—C10	109.5 (2)	C14—C13—C12	118.8 (3)
C4—C3—C10	131.2 (2)	C14—C13—H13	120.6 (16)
N1—C4—C3	119.2 (2)	C12—C13—H13	120.6 (16)
N1—C4—C5	109.8 (2)	N4—C14—C13	121.2 (3)
C3—C4—C5	131.0 (3)	N4—C14—H14	117.3 (15)
N3—C5—C6	119.3 (3)	C13—C14—H14	121.4 (15)
N3—C5—C4	120.1 (2)	O1—C15—O2	126.8 (3)
C6—C5—C4	120.6 (3)	O1—C15—C1	121.9 (3)
C7—C6—C5	119.2 (3)	O2—C15—C1	111.3 (3)
C7—C6—H6	125.0 (17)	O3—C16—O4	125.7 (3)
C5—C6—H6	115.5 (17)	O3—C16—C2	116.6 (3)
C8—C7—C6	120.5 (3)	O4—C16—C2	117.7 (3)
C8—C7—H7	119.7 (15)
C4—N1—C1—C2	3.1 (5)	C5—C6—C7—C8	0.0 (6)
C4—N1—C1—C15	−173.8 (3)	C6—C7—C8—C9	−0.1 (6)
C3—N2—C2—C1	0.7 (4)	C5—N3—C9—C8	0.6 (5)
C3—N2—C2—C16	−177.6 (3)	C7—C8—C9—N3	−0.2 (5)
N1—C1—C2—N2	−4.8 (5)	C14—N4—C10—C11	−0.5 (5)
C15—C1—C2—N2	171.8 (3)	C14—N4—C10—C3	180.0 (3)
N1—C1—C2—C16	173.4 (3)	N2—C3—C10—N4	−174.9 (3)
C15—C1—C2—C16	−10.0 (5)	C4—C3—C10—N4	7.0 (5)
C2—N2—C3—C4	4.9 (4)	N2—C3—C10—C11	5.6 (4)
C2—N2—C3—C10	−173.5 (3)	C4—C3—C10—C11	−172.5 (3)
C1—N1—C4—C3	2.5 (4)	N4—C10—C11—C12	0.8 (5)
C1—N1—C4—C5	−178.0 (3)	C3—C10—C11—C12	−179.6 (3)
N2—C3—C4—N1	−6.5 (4)	C10—C11—C12—C13	0.2 (6)
C10—C3—C4—N1	171.4 (3)	C11—C12—C13—C14	−1.5 (6)
N2—C3—C4—C5	174.1 (3)	C10—N4—C14—C13	−0.9 (5)
C10—C3—C4—C5	−8.0 (6)	C12—C13—C14—N4	1.9 (5)
C9—N3—C5—C6	−0.7 (5)	N1—C1—C15—O1	−57.6 (4)
C9—N3—C5—C4	179.6 (3)	C2—C1—C15—O1	125.6 (4)
N1—C4—C5—N3	−177.5 (3)	N1—C1—C15—O2	119.9 (3)
C3—C4—C5—N3	2.0 (5)	C2—C1—C15—O2	−56.8 (4)
N1—C4—C5—C6	2.8 (4)	N2—C2—C16—O3	140.5 (3)
C3—C4—C5—C6	−177.7 (3)	C1—C2—C16—O3	−37.8 (5)
N3—C5—C6—C7	0.4 (5)	N2—C2—C16—O4	−39.0 (4)
C4—C5—C6—C7	−179.9 (3)	C1—C2—C16—O4	142.8 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2O···O4^i	1.20 (4)	1.29 (4)	2.475 (3)	169 (3)
N3—H3N···N4	1.22 (3)	1.32 (3)	2.528 (3)	167 (3)

Symmetry code: (i) x, −y+1/2, z+1/2.

(II) 6-Carboxy-5-carboxylatopyrazine-2,3-diyldi-2-pyridinium chloride 2.25 hydrate

Crystal data

C16H11N4O4^+·Cl^−·2.25H2O	F(000) = 1652
Mr = 399.27	Dx = 1.464 Mg m^−3
Monoclinic, I2/a	Mo Kα radiation, λ = 0.71073 Å
a = 19.5883 (17) Å	Cell parameters from 5000 reflections
b = 8.0623 (5) Å	θ = 2.1–25.9°
c = 22.936 (2) Å	µ = 0.26 mm^−1
β = 90.559 (11)°	T = 293 K
V = 3622.0 (5) Å^3	Rod, colourless
Z = 8	0.5 × 0.2 × 0.1 mm

Data collection

Stoe IPDS diffractometer	1943 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.055
Graphite monochromator	θmax = 25.9°, θmin = 2.1°
Detector resolution: 0.81Å pixels mm^-1	h = −24→23
ϕ oscillation scans	k = −9→9
13718 measured reflections	l = −28→28
3488 independent reflections

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) = 0.093	All H-atom parameters refined
S = 0.82	w = 1/[σ^2(Fo^2) + (0.05P)^2] where P = (Fo^2 + 2Fc^2)/3
3488 reflections	(Δ/σ)max = 0.027
327 parameters	Δρmax = 0.63 e Å^−3
0 restraints	Δρmin = −0.26 e Å^−3

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
O1	0.00022 (9)	0.1926 (2)	0.33297 (7)	0.0504 (5)
O2	−0.04931 (9)	0.4384 (2)	0.31389 (8)	0.0468 (4)
H2O	−0.0711 (17)	0.427 (4)	0.3513 (16)	0.098 (11)*
O3	−0.12559 (9)	0.1414 (3)	0.14811 (8)	0.0677 (6)
O4	−0.12505 (7)	0.1999 (2)	0.24294 (7)	0.0445 (4)
N1	0.07729 (9)	0.3448 (2)	0.23364 (8)	0.0335 (5)
N2	−0.00305 (9)	0.2937 (2)	0.13643 (8)	0.0332 (4)
N3	0.20722 (9)	0.4782 (3)	0.21689 (8)	0.0362 (5)
H3N	0.1784 (14)	0.552 (4)	0.2371 (11)	0.059 (8)*
N4	0.04464 (11)	0.2977 (3)	0.02828 (8)	0.0419 (5)
H4N	0.0143 (14)	0.218 (4)	0.0390 (11)	0.056 (9)*
C1	0.01098 (10)	0.3102 (3)	0.23847 (9)	0.0299 (5)
C2	−0.02847 (10)	0.2726 (3)	0.18944 (9)	0.0315 (5)
C3	0.06192 (11)	0.3391 (3)	0.13071 (9)	0.0327 (5)
C4	0.10405 (10)	0.3533 (3)	0.17995 (9)	0.0316 (5)
C5	0.17977 (11)	0.3684 (3)	0.17965 (10)	0.0347 (5)
C6	0.22210 (13)	0.2671 (4)	0.14841 (12)	0.0462 (7)
H6	0.2041 (12)	0.194 (3)	0.1250 (11)	0.043 (8)*
C7	0.29176 (13)	0.2780 (4)	0.15607 (13)	0.0529 (7)
H7	0.3200 (15)	0.208 (4)	0.1362 (12)	0.068 (9)*
C8	0.31845 (13)	0.3931 (4)	0.19409 (12)	0.0492 (7)
H8	0.3652 (14)	0.403 (3)	0.2006 (10)	0.051 (7)*
C9	0.27469 (12)	0.4937 (4)	0.22394 (12)	0.0438 (7)
H9	0.2894 (12)	0.575 (3)	0.2516 (11)	0.043 (7)*
C10	0.08151 (12)	0.3768 (3)	0.06990 (10)	0.0367 (6)
C11	0.12867 (14)	0.4934 (4)	0.05341 (12)	0.0500 (7)
H11	0.1562 (14)	0.547 (4)	0.0826 (12)	0.060 (8)*
C12	0.13715 (17)	0.5273 (5)	−0.00524 (13)	0.0633 (9)
H12	0.1709 (15)	0.608 (4)	−0.0163 (12)	0.063 (8)*
C13	0.09857 (17)	0.4461 (4)	−0.04616 (13)	0.0629 (9)
H14	0.0993 (16)	0.469 (4)	−0.0863 (15)	0.089 (10)*
C14	0.05233 (17)	0.3294 (4)	−0.02876 (12)	0.0562 (8)
H13	0.0220 (14)	0.270 (4)	−0.0548 (12)	0.064 (9)*
C15	−0.01420 (11)	0.3048 (3)	0.30038 (10)	0.0357 (6)
C16	−0.09956 (11)	0.1984 (3)	0.19289 (11)	0.0389 (6)
Cl1	0.12673 (3)	0.94713 (9)	0.07395 (3)	0.0540 (2)
O1W	0.44735 (11)	0.9286 (3)	0.04654 (11)	0.0664 (6)
H1A	0.4215 (18)	0.931 (4)	0.0177 (16)	0.084 (12)*
H1B	0.4188 (19)	0.899 (5)	0.0784 (18)	0.106 (13)*
O2W	0.2565 (4)	0.7120 (7)	0.1020 (5)	0.089 (3)	0.62 (2)
H21	0.228 (4)	0.789 (11)	0.088 (3)	0.09 (2)*	0.62 (2)
H22	0.288 (4)	0.774 (10)	0.107 (4)	0.11 (3)*	0.62 (2)
O3W	0.2358 (5)	0.770 (2)	0.1446 (9)	0.115 (8)	0.38 (2)
H31	0.286 (5)	0.786 (10)	0.145 (4)	0.06 (2)*	0.38 (2)
H32	0.210 (6)	0.846 (15)	0.115 (7)	0.11 (4)*	0.38 (2)
O4W	0.2500	0.1391 (9)	0.0000	0.137 (4)	0.50
H41	0.2187	0.0920	0.0189	0.100*	0.50

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0583 (11)	0.0532 (13)	0.0397 (10)	0.0104 (9)	0.0035 (8)	0.0102 (9)
O2	0.0603 (11)	0.0369 (11)	0.0434 (10)	0.0024 (9)	0.0184 (8)	0.0000 (8)
O3	0.0412 (10)	0.1094 (19)	0.0523 (12)	−0.0232 (11)	−0.0046 (9)	−0.0108 (11)
O4	0.0344 (9)	0.0507 (12)	0.0484 (10)	−0.0046 (8)	0.0079 (7)	0.0039 (8)
N1	0.0317 (10)	0.0371 (13)	0.0316 (10)	−0.0004 (9)	0.0024 (8)	−0.0011 (8)
N2	0.0316 (10)	0.0360 (13)	0.0322 (10)	0.0009 (9)	−0.0007 (8)	0.0001 (9)
N3	0.0273 (10)	0.0426 (14)	0.0386 (11)	0.0000 (9)	0.0024 (8)	−0.0017 (10)
N4	0.0490 (12)	0.0445 (15)	0.0321 (11)	0.0066 (11)	0.0014 (9)	−0.0029 (10)
C1	0.0300 (12)	0.0264 (14)	0.0333 (12)	0.0007 (10)	0.0034 (9)	0.0015 (10)
C2	0.0288 (11)	0.0315 (15)	0.0341 (13)	0.0022 (9)	0.0005 (10)	0.0024 (10)
C3	0.0344 (12)	0.0299 (14)	0.0337 (12)	0.0022 (10)	0.0033 (9)	−0.0003 (10)
C4	0.0296 (11)	0.0314 (15)	0.0338 (12)	−0.0002 (10)	0.0024 (9)	−0.0014 (10)
C5	0.0313 (12)	0.0395 (15)	0.0333 (12)	0.0002 (11)	0.0031 (9)	0.0026 (11)
C6	0.0408 (15)	0.0471 (19)	0.0509 (16)	0.0011 (13)	0.0116 (12)	−0.0069 (14)
C7	0.0398 (15)	0.052 (2)	0.0667 (19)	0.0112 (14)	0.0168 (13)	0.0061 (15)
C8	0.0282 (13)	0.056 (2)	0.0635 (18)	0.0039 (13)	0.0038 (12)	0.0153 (15)
C9	0.0322 (13)	0.0515 (19)	0.0477 (15)	−0.0048 (12)	−0.0025 (11)	0.0044 (13)
C10	0.0372 (12)	0.0394 (15)	0.0334 (13)	0.0061 (11)	0.0026 (10)	0.0007 (11)
C11	0.0477 (16)	0.055 (2)	0.0471 (16)	−0.0023 (14)	0.0053 (13)	0.0104 (14)
C12	0.0627 (19)	0.070 (2)	0.0571 (19)	0.0060 (17)	0.0208 (15)	0.0231 (17)
C13	0.077 (2)	0.075 (2)	0.0372 (16)	0.0269 (19)	0.0155 (16)	0.0134 (17)
C14	0.072 (2)	0.063 (2)	0.0329 (15)	0.0233 (17)	−0.0009 (14)	−0.0036 (14)
C15	0.0331 (12)	0.0373 (16)	0.0365 (13)	−0.0036 (11)	0.0018 (10)	−0.0006 (12)
C16	0.0286 (12)	0.0420 (16)	0.0460 (15)	0.0017 (11)	−0.0025 (11)	0.0027 (12)
Cl1	0.0539 (4)	0.0623 (5)	0.0460 (4)	0.0026 (3)	0.0048 (3)	−0.0016 (3)
O1W	0.0630 (13)	0.0796 (17)	0.0565 (13)	0.0058 (11)	−0.0065 (12)	0.0218 (12)
O2W	0.062 (4)	0.065 (4)	0.141 (7)	0.009 (3)	−0.028 (4)	−0.007 (3)
O3W	0.057 (6)	0.137 (12)	0.150 (14)	−0.001 (5)	−0.008 (6)	0.077 (11)
O4W	0.159 (7)	0.069 (5)	0.187 (8)	0.000	0.151 (7)	0.000

Geometric parameters (Å, º)

O1—C15	1.205 (3)	C7—C8	1.373 (4)
O2—C15	1.317 (3)	C7—H7	0.92 (3)
O2—H2O	0.97 (4)	C8—C9	1.369 (4)
O3—C16	1.231 (3)	C8—H8	0.93 (3)
O4—C16	1.256 (3)	C9—H9	0.95 (3)
N1—C1	1.334 (3)	C10—C11	1.373 (4)
N1—C4	1.345 (3)	C11—C12	1.384 (4)
N2—C2	1.329 (3)	C11—H11	0.96 (3)
N2—C3	1.332 (3)	C12—C13	1.366 (5)
N3—C9	1.336 (3)	C12—H12	0.96 (3)
N3—C5	1.339 (3)	C13—C14	1.368 (5)
N3—H3N	0.94 (3)	C13—H14	0.94 (3)
N4—C14	1.343 (3)	C14—H13	0.96 (3)
N4—C10	1.351 (3)	O1W—H1A	0.83 (4)
N4—H4N	0.91 (3)	O1W—H1B	0.95 (4)
C1—C2	1.392 (3)	O2W—H21	0.89 (9)
C1—C15	1.508 (3)	O2W—H22	0.81 (9)
C2—C16	1.518 (3)	O2W—H31	1.29 (8)
C3—C4	1.397 (3)	O2W—H32	1.45 (12)
C3—C10	1.482 (3)	O3W—H21	1.32 (6)
C4—C5	1.488 (3)	O3W—H22	1.34 (7)
C5—C6	1.371 (3)	O3W—H31	1.00 (10)
C6—C7	1.377 (4)	O3W—H32	1.05 (14)
C6—H6	0.87 (3)	O4W—H41	0.8444
C15—O2—H2O	112 (2)	C8—C9—H9	123.5 (14)
C1—N1—C4	118.39 (18)	N4—C10—C11	119.0 (2)
C2—N2—C3	119.48 (18)	N4—C10—C3	115.2 (2)
C9—N3—C5	122.0 (2)	C11—C10—C3	125.5 (2)
C9—N3—H3N	118.5 (16)	C10—C11—C12	119.4 (3)
C5—N3—H3N	119.4 (16)	C10—C11—H11	119.4 (16)
C14—N4—C10	122.3 (3)	C12—C11—H11	121.2 (16)
C14—N4—H4N	118.5 (17)	C13—C12—C11	120.1 (3)
C10—N4—H4N	119.2 (17)	C13—C12—H12	121.3 (17)
N1—C1—C2	120.78 (19)	C11—C12—H12	118.6 (17)
N1—C1—C15	114.33 (18)	C12—C13—C14	119.5 (3)
C2—C1—C15	124.77 (19)	C12—C13—H14	125 (2)
N2—C2—C1	120.09 (19)	C14—C13—H14	116 (2)
N2—C2—C16	116.74 (19)	N4—C14—C13	119.7 (3)
C1—C2—C16	123.09 (19)	N4—C14—H13	115.7 (17)
N2—C3—C4	120.02 (19)	C13—C14—H13	124.5 (17)
N2—C3—C10	113.93 (19)	O1—C15—O2	126.0 (2)
C4—C3—C10	126.0 (2)	O1—C15—C1	121.9 (2)
N1—C4—C3	120.24 (19)	O2—C15—C1	112.0 (2)
N1—C4—C5	113.94 (19)	O3—C16—O4	126.9 (2)
C3—C4—C5	125.7 (2)	O3—C16—C2	118.4 (2)
N3—C5—C6	119.1 (2)	O4—C16—C2	114.6 (2)
N3—C5—C4	116.4 (2)	H1A—O1W—H1B	105 (3)
C6—C5—C4	124.2 (2)	H21—O2W—H22	95 (7)
C5—C6—C7	119.9 (3)	H21—O2W—H31	103 (6)
C5—C6—H6	118.9 (16)	H22—O2W—H31	42 (6)
C7—C6—H6	121.2 (16)	H21—O2W—H32	33 (6)
C8—C7—C6	119.7 (3)	H22—O2W—H32	90 (7)
C8—C7—H7	120.3 (19)	H31—O2W—H32	78 (7)
C6—C7—H7	120.0 (19)	H21—O3W—H22	57 (5)
C9—C8—C7	118.8 (3)	H21—O3W—H31	96 (6)
C9—C8—H8	119.1 (16)	H22—O3W—H31	41 (5)
C7—C8—H8	122.1 (16)	H21—O3W—H32	40 (6)
N3—C9—C8	120.5 (3)	H22—O3W—H32	87 (7)
N3—C9—H9	116.0 (14)	H31—O3W—H32	114 (8)
C4—N1—C1—C2	4.4 (3)	C5—C6—C7—C8	−1.4 (4)
C4—N1—C1—C15	−179.5 (2)	C6—C7—C8—C9	0.5 (4)
C3—N2—C2—C1	4.9 (3)	C5—N3—C9—C8	−1.9 (4)
C3—N2—C2—C16	−171.9 (2)	C7—C8—C9—N3	1.1 (4)
N1—C1—C2—N2	−9.6 (3)	C14—N4—C10—C11	−0.2 (4)
C15—C1—C2—N2	174.7 (2)	C14—N4—C10—C3	174.3 (2)
N1—C1—C2—C16	167.0 (2)	N2—C3—C10—N4	−26.8 (3)
C15—C1—C2—C16	−8.7 (4)	C4—C3—C10—N4	155.6 (2)
C2—N2—C3—C4	4.3 (3)	N2—C3—C10—C11	147.2 (2)
C2—N2—C3—C10	−173.4 (2)	C4—C3—C10—C11	−30.3 (4)
C1—N1—C4—C3	4.9 (3)	N4—C10—C11—C12	0.2 (4)
C1—N1—C4—C5	−171.7 (2)	C3—C10—C11—C12	−173.6 (2)
N2—C3—C4—N1	−9.5 (3)	C10—C11—C12—C13	0.4 (4)
C10—C3—C4—N1	167.9 (2)	C11—C12—C13—C14	−1.0 (5)
N2—C3—C4—C5	166.7 (2)	C10—N4—C14—C13	−0.4 (4)
C10—C3—C4—C5	−15.9 (4)	C12—C13—C14—N4	1.0 (4)
C9—N3—C5—C6	1.0 (4)	N1—C1—C15—O1	−72.5 (3)
C9—N3—C5—C4	174.7 (2)	C2—C1—C15—O1	103.4 (3)
N1—C4—C5—N3	−45.6 (3)	N1—C1—C15—O2	104.1 (2)
C3—C4—C5—N3	138.0 (2)	C2—C1—C15—O2	−80.0 (3)
N1—C4—C5—C6	127.8 (3)	N2—C2—C16—O3	9.8 (3)
C3—C4—C5—C6	−48.6 (4)	C1—C2—C16—O3	−166.9 (2)
N3—C5—C6—C7	0.7 (4)	N2—C2—C16—O4	−171.5 (2)
C4—C5—C6—C7	−172.5 (2)	C1—C2—C16—O4	11.8 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2O···Cl1^i	0.97 (4)	2.05 (4)	2.9996 (18)	168 (3)
N3—H3N···O4^ii	0.94 (3)	1.65 (3)	2.582 (3)	167 (2)
N4—H4N···O1W^iii	0.91 (3)	1.78 (3)	2.674 (3)	169 (3)
O1W—H1A···Cl1^iv	0.83 (4)	2.30 (4)	3.112 (3)	167 (3)
O1W—H1B···O3^v	0.95 (4)	1.86 (4)	2.802 (3)	170 (3)
O2W—H21···Cl1	0.89 (9)	2.38 (10)	3.230 (6)	160 (6)
O2W—H22···O3^v	0.81 (9)	2.04 (10)	2.794 (6)	155 (8)
O3W—H31···O3^v	1.00 (10)	1.82 (10)	2.809 (9)	168 (7)
O3W—H32···Cl1	1.05 (14)	2.04 (14)	3.028 (9)	157 (9)
O4W—H41···Cl1^vi	0.84	2.50	3.344 (3)	179

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

(IIIa) 6-carboxy-5-carboxylatopyrazine-2,3-diyldi-2-pyridinium perchlorate trihydrate

Crystal data

C16H11N4O4^+·ClO4^−·3H2O	F(000) = 492
Mr = 476.79	Dx = 1.609 Mg m^−3
Monoclinic, P2/c	Mo Kα radiation, λ = 0.71073 Å
a = 6.1401 (7) Å	Cell parameters from 5000 reflections
b = 15.6358 (12) Å	θ = 1.7–26.1°
c = 10.7154 (8) Å	µ = 0.27 mm^−1
β = 106.934 (8)°	T = 223 K
V = 984.13 (15) Å^3	Block, pale yellow
Z = 2	0.36 × 0.35 × 0.26 mm

Data collection

Stoe IPDS diffractometer	1419 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.033
Graphite monochromator	θmax = 25.9°, θmin = 2.4°
Detector resolution: 0.82Å pixels mm^-1	h = −7→7
ϕ oscillation scans	k = −19→19
7650 measured reflections	l = −13→13
1914 independent reflections

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)] = 0.040	Hydrogen site location: difference Fourier map
wR(F^2) = 0.115	All H-atom parameters refined
S = 1.02	w = 1/[σ^2(Fo^2) + (0.0786P)^2] where P = (Fo^2 + 2Fc^2)/3
1914 reflections	(Δ/σ)max < 0.001
190 parameters	Δρmax = 0.18 e Å^−3
0 restraints	Δρmin = −0.58 e Å^−3

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
O1	0.3233 (3)	−0.03491 (9)	0.10493 (15)	0.0487 (4)
O2	0.1347 (3)	−0.12771 (9)	0.18880 (15)	0.0464 (4)
H2O	0.0000	−0.130 (3)	0.2500	0.080 (12)*
N1	0.0965 (3)	0.09766 (9)	0.15109 (14)	0.0297 (4)
N2	0.1821 (3)	0.24553 (10)	0.03765 (14)	0.0321 (4)
H2N	0.285 (4)	0.2022 (15)	0.051 (2)	0.047 (6)*
C1	0.0643 (3)	0.02366 (11)	0.20518 (16)	0.0298 (4)
C2	0.0346 (3)	0.17086 (11)	0.19261 (16)	0.0276 (4)
C3	0.0324 (3)	0.24614 (11)	0.10802 (16)	0.0291 (4)
C4	−0.1222 (4)	0.31173 (12)	0.09105 (19)	0.0362 (5)
H4	−0.229 (4)	0.3116 (13)	0.1394 (19)	0.035 (5)*
C5	−0.1203 (4)	0.37640 (13)	0.0023 (2)	0.0447 (5)
H5	−0.224 (5)	0.4201 (16)	−0.010 (2)	0.054 (7)*
C6	0.0372 (4)	0.37459 (14)	−0.0665 (2)	0.0456 (5)
H6	0.045 (4)	0.4182 (16)	−0.125 (2)	0.053 (6)*
C7	0.1876 (4)	0.30819 (13)	−0.04735 (19)	0.0402 (5)
H7	0.299 (4)	0.3010 (14)	−0.096 (2)	0.045 (6)*
C8	0.1833 (4)	−0.05126 (12)	0.16216 (18)	0.0351 (4)
Cl1	0.5000	0.44850 (5)	0.2500	0.0616 (3)
O11	0.5000	0.35788 (14)	0.2500	0.0530 (6)
O12	0.5187 (7)	0.4638 (2)	0.4036 (3)	0.0658 (10)	0.50
O13	0.2741 (12)	0.4793 (5)	0.2005 (7)	0.100 (3)	0.50
O14	0.3338 (13)	0.4887 (5)	0.2673 (6)	0.093 (2)	0.50
O1W	0.5044 (3)	0.12538 (10)	0.06311 (16)	0.0441 (4)
H1A	0.552 (5)	0.1116 (17)	0.000 (3)	0.072 (9)*
H1B	0.442 (5)	0.0793 (18)	0.080 (2)	0.054 (7)*
O2W	0.5000	0.25145 (16)	0.7500	0.0713 (8)
H2WA	0.3585	0.2104	0.7136	0.100*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0584 (10)	0.0409 (8)	0.0574 (10)	0.0081 (7)	0.0338 (9)	−0.0015 (6)
O2	0.0539 (9)	0.0312 (8)	0.0586 (9)	0.0040 (6)	0.0236 (8)	−0.0015 (6)
N1	0.0274 (8)	0.0322 (8)	0.0301 (8)	0.0009 (6)	0.0094 (6)	−0.0005 (6)
N2	0.0342 (9)	0.0329 (8)	0.0317 (8)	−0.0027 (7)	0.0135 (7)	−0.0034 (6)
C1	0.0287 (10)	0.0312 (9)	0.0277 (8)	−0.0013 (7)	0.0056 (7)	−0.0019 (7)
C2	0.0235 (9)	0.0299 (9)	0.0297 (9)	0.0004 (7)	0.0085 (7)	−0.0008 (7)
C3	0.0300 (10)	0.0310 (9)	0.0271 (8)	−0.0030 (7)	0.0095 (7)	−0.0022 (7)
C4	0.0376 (11)	0.0370 (10)	0.0360 (10)	0.0026 (8)	0.0137 (9)	0.0014 (8)
C5	0.0534 (14)	0.0365 (11)	0.0431 (11)	0.0085 (10)	0.0125 (10)	0.0067 (9)
C6	0.0654 (15)	0.0396 (11)	0.0345 (10)	−0.0026 (10)	0.0187 (10)	0.0069 (9)
C7	0.0508 (13)	0.0416 (11)	0.0331 (10)	−0.0093 (9)	0.0198 (9)	−0.0019 (8)
C8	0.0385 (11)	0.0342 (10)	0.0325 (9)	0.0043 (8)	0.0103 (8)	−0.0013 (8)
Cl1	0.0433 (5)	0.0381 (4)	0.0898 (7)	0.000	−0.0020 (4)	0.000
O11	0.0560 (14)	0.0413 (12)	0.0661 (14)	0.000	0.0249 (12)	0.000
O12	0.086 (3)	0.071 (2)	0.0430 (18)	−0.023 (2)	0.0225 (18)	−0.0166 (16)
O13	0.069 (3)	0.070 (3)	0.122 (5)	0.022 (2)	−0.032 (4)	0.013 (4)
O14	0.115 (6)	0.086 (4)	0.104 (5)	0.052 (4)	0.073 (4)	0.017 (4)
O1W	0.0407 (9)	0.0466 (9)	0.0517 (9)	0.0004 (7)	0.0236 (7)	−0.0074 (7)
O2W	0.0666 (18)	0.0549 (15)	0.096 (2)	0.000	0.0298 (15)	0.000

Geometric parameters (Å, º)

O1—C8	1.219 (2)	C5—H5	0.92 (3)
O2—C8	1.284 (2)	C6—C7	1.365 (3)
O2—H2O	1.1965 (19)	C6—H6	0.94 (2)
N1—C2	1.323 (2)	C7—H7	0.98 (2)
N1—C1	1.334 (2)	Cl1—O14	1.258 (6)
N2—C7	1.345 (2)	Cl1—O14^ii	1.258 (6)
N2—C3	1.348 (2)	Cl1—O11	1.417 (2)
N2—H2N	0.91 (2)	Cl1—O13^ii	1.418 (6)
C1—C1^i	1.410 (4)	Cl1—O13	1.418 (6)
C1—C8	1.522 (3)	Cl1—O12	1.634 (3)
C2—C2^i	1.413 (3)	Cl1—O12^ii	1.634 (3)
C2—C3	1.483 (2)	O12—O14	1.615 (8)
C3—C4	1.373 (3)	O13—O14	0.718 (7)
C4—C5	1.391 (3)	O1W—H1A	0.84 (3)
C4—H4	0.95 (2)	O1W—H1B	0.86 (3)
C5—C6	1.376 (3)	O2W—H2WA	1.0590
C8—O2—H2O	113 (2)	O2—C8—C1	119.08 (17)
C2—N1—C1	120.69 (15)	O14—Cl1—O14^ii	120.0 (8)
C7—N2—C3	121.96 (18)	O14—Cl1—O11	120.0 (4)
C7—N2—H2N	119.7 (14)	O14^ii—Cl1—O11	120.0 (4)
C3—N2—H2N	118.3 (14)	O14—Cl1—O13^ii	121.5 (4)
N1—C1—C1^i	118.63 (10)	O14^ii—Cl1—O13^ii	30.4 (4)
N1—C1—C8	113.01 (16)	O11—Cl1—O13^ii	109.9 (3)
C1^i—C1—C8	128.32 (11)	O14—Cl1—O13	30.4 (4)
N1—C2—C2^i	118.77 (10)	O14^ii—Cl1—O13	121.5 (4)
N1—C2—C3	115.67 (15)	O11—Cl1—O13	109.9 (3)
C2^i—C2—C3	125.48 (10)	O13^ii—Cl1—O13	140.3 (6)
N2—C3—C4	119.27 (17)	O14—Cl1—O12	66.4 (3)
N2—C3—C2	116.75 (16)	O14^ii—Cl1—O12	104.7 (3)
C4—C3—C2	123.80 (16)	O11—Cl1—O12	98.43 (13)
C3—C4—C5	119.36 (19)	O13^ii—Cl1—O12	78.5 (4)
C3—C4—H4	119.3 (12)	O13—Cl1—O12	95.8 (4)
C5—C4—H4	121.4 (12)	O14—Cl1—O12^ii	104.7 (3)
C6—C5—C4	119.9 (2)	O14^ii—Cl1—O12^ii	66.4 (3)
C6—C5—H5	120.4 (16)	O11—Cl1—O12^ii	98.43 (13)
C4—C5—H5	119.7 (16)	O13^ii—Cl1—O12^ii	95.8 (4)
C7—C6—C5	119.05 (19)	O13—Cl1—O12^ii	78.5 (4)
C7—C6—H6	119.3 (15)	O12—Cl1—O12^ii	163.1 (3)
C5—C6—H6	121.6 (15)	O14—O12—Cl1	45.6 (2)
N2—C7—C6	120.44 (19)	O14—O13—Cl1	62.4 (8)
N2—C7—H7	115.9 (13)	O13—O14—Cl1	87.2 (9)
C6—C7—H7	123.6 (13)	O13—O14—O12	150.7 (12)
O1—C8—O2	123.39 (17)	Cl1—O14—O12	68.0 (4)
O1—C8—C1	117.52 (17)	H1A—O1W—H1B	104 (3)
C2—N1—C1—C1^i	8.5 (3)	O11—Cl1—O12—O14	−119.1 (4)
C2—N1—C1—C8	−169.67 (16)	O13^ii—Cl1—O12—O14	132.2 (4)
C1—N1—C2—C2^i	9.4 (3)	O13—Cl1—O12—O14	−8.0 (7)
C1—N1—C2—C3	−167.37 (16)	O12^ii—Cl1—O12—O14	60.9 (4)
C7—N2—C3—C4	1.2 (3)	O14^ii—Cl1—O13—O14	−96.5 (14)
C7—N2—C3—C2	176.52 (16)	O11—Cl1—O13—O14	115.8 (11)
N1—C2—C3—N2	−29.8 (2)	O13^ii—Cl1—O13—O14	−64.2 (11)
C2^i—C2—C3—N2	153.7 (2)	O12—Cl1—O13—O14	14.6 (12)
N1—C2—C3—C4	145.31 (18)	O12^ii—Cl1—O13—O14	−149.3 (12)
C2^i—C2—C3—C4	−31.2 (3)	Cl1—O13—O14—O12	−31 (2)
N2—C3—C4—C5	−0.4 (3)	O14^ii—Cl1—O14—O13	102.1 (12)
C2—C3—C4—C5	−175.34 (18)	O11—Cl1—O14—O13	−77.9 (12)
C3—C4—C5—C6	−0.7 (3)	O13^ii—Cl1—O14—O13	137.5 (11)
C4—C5—C6—C7	0.9 (3)	O12—Cl1—O14—O13	−164.1 (13)
C3—N2—C7—C6	−1.0 (3)	O12^ii—Cl1—O14—O13	31.1 (13)
C5—C6—C7—N2	−0.1 (3)	O14^ii—Cl1—O14—O12	−93.9 (3)
N1—C1—C8—O1	12.7 (2)	O11—Cl1—O14—O12	86.1 (3)
C1^i—C1—C8—O1	−165.2 (2)	O13^ii—Cl1—O14—O12	−58.4 (5)
N1—C1—C8—O2	−168.12 (16)	O13—Cl1—O14—O12	164.1 (13)
C1^i—C1—C8—O2	14.0 (3)	O12^ii—Cl1—O14—O12	−164.8 (2)
O14^ii—Cl1—O12—O14	116.7 (8)	Cl1—O12—O14—O13	34 (3)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2O···O2^i	1.20 (1)	1.20 (1)	2.392 (3)	177 (4)
N2—H2N···O1W	0.91 (2)	1.78 (3)	2.684 (2)	172 (2)
O1W—H1A···O1^iii	0.84 (3)	1.94 (3)	2.734 (2)	156 (3)
O1W—H1B···O1	0.86 (3)	1.98 (3)	2.830 (2)	172 (3)
O2W—H2WA···O2^iv	1.06	1.85	2.889 (2)	167

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

(IIIb) 6-carboxy-5-carboxylatopyrazine-2,3-diyldi-2-pyridinium hexafluorophosphate trihydrate

Crystal data

C16H11N4O4^+·PF6^−·3H2O	F(000) = 532
Mr = 522.31	Dx = 1.722 Mg m^−3
Monoclinic, P2/c	Mo Kα radiation, λ = 0.71073 Å
a = 6.1910 (6) Å	Cell parameters from 5000 reflections
b = 15.6564 (11) Å	θ = 1.7–26.1°
c = 10.8349 (10) Å	µ = 0.24 mm^−1
β = 106.400 (11)°	T = 293 K
V = 1007.48 (15) Å^3	Rod, pale yellow
Z = 2	0.70 × 0.20 × 0.15 mm

Data collection

Stoe IPDS diffractometer	1628 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.029
Graphite monochromator	θmax = 25.9°, θmin = 3.3°
Detector resolution: 0.81Å pixels mm^-1	h = −7→7
ϕ oscillation scans	k = −19→19
7713 measured reflections	l = −13→13
1944 independent reflections

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)] = 0.044	Hydrogen site location: difference Fourier map
wR(F^2) = 0.152	All H-atom parameters refined
S = 1.20	w = 1/[σ^2(Fo^2) + (0.1018P)^2 + 0.1313P] where P = (Fo^2 + 2Fc^2)/3
1944 reflections	(Δ/σ)max < 0.001
186 parameters	Δρmax = 0.25 e Å^−3
0 restraints	Δρmin = −0.83 e Å^−3

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq
N1	0.4040 (3)	0.09425 (10)	0.34843 (16)	0.0286 (4)
N2	0.3208 (3)	0.24229 (11)	0.46196 (15)	0.0302 (4)
H2N	0.214 (6)	0.2008 (19)	0.451 (3)	0.049 (7)*
O1	0.1776 (3)	−0.03754 (11)	0.39442 (18)	0.0473 (5)
O2	0.3656 (3)	−0.13016 (10)	0.31136 (18)	0.0478 (5)
H2O	0.5000	−0.124 (4)	0.2500	0.101 (19)*
C1	0.4356 (3)	0.02054 (13)	0.29450 (18)	0.0293 (4)
C2	0.4658 (3)	0.16771 (12)	0.30675 (17)	0.0263 (4)
C3	0.4688 (3)	0.24235 (13)	0.39136 (17)	0.0265 (4)
C4	0.6261 (4)	0.30703 (14)	0.40890 (19)	0.0334 (5)
H4	0.747 (5)	0.3146 (17)	0.359 (3)	0.045 (7)*
C5	0.6266 (4)	0.37137 (15)	0.4977 (2)	0.0407 (5)
H5	0.725 (5)	0.4157 (19)	0.508 (3)	0.048 (8)*
C6	0.4718 (4)	0.36946 (15)	0.5673 (2)	0.0411 (6)
H6	0.474 (5)	0.413 (2)	0.634 (3)	0.053 (8)*
C7	0.3190 (4)	0.30384 (14)	0.54757 (19)	0.0363 (5)
H7	0.215 (5)	0.2940 (17)	0.592 (3)	0.042 (7)*
C8	0.3177 (4)	−0.05412 (14)	0.3380 (2)	0.0361 (5)
O1W	−0.0014 (3)	0.12351 (12)	0.43619 (18)	0.0434 (5)
H1WA	−0.047 (6)	0.110 (2)	0.495 (4)	0.069 (11)*
H1WB	0.059 (7)	0.076 (2)	0.416 (4)	0.074 (11)*
O2W	0.0000	−0.2445 (3)	0.2500	0.1238 (18)
H2WA	−0.1451	−0.2321	0.2136	0.100*
P1	0.0000	0.45753 (5)	0.2500	0.0331 (3)
F1	0.0000	0.35438 (12)	0.2500	0.0437 (5)
F2	0.0000	0.55917 (14)	0.2500	0.0610 (6)
F3	0.0436 (3)	0.45621 (10)	0.40178 (13)	0.0532 (5)
F4	0.2650 (2)	0.45701 (10)	0.26905 (15)	0.0523 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0279 (8)	0.0322 (9)	0.0258 (8)	−0.0012 (6)	0.0075 (6)	0.0005 (6)
N2	0.0326 (9)	0.0330 (9)	0.0257 (8)	0.0021 (7)	0.0096 (7)	0.0023 (7)
O1	0.0580 (11)	0.0395 (9)	0.0541 (10)	−0.0102 (7)	0.0317 (9)	0.0014 (7)
O2	0.0599 (11)	0.0300 (8)	0.0578 (11)	−0.0040 (7)	0.0233 (9)	0.0021 (7)
C1	0.0298 (9)	0.0313 (10)	0.0254 (9)	−0.0001 (8)	0.0053 (8)	0.0009 (8)
C2	0.0238 (8)	0.0295 (10)	0.0253 (9)	0.0000 (7)	0.0066 (7)	0.0014 (7)
C3	0.0288 (9)	0.0297 (10)	0.0213 (9)	0.0016 (7)	0.0073 (7)	0.0025 (7)
C4	0.0378 (11)	0.0348 (11)	0.0280 (9)	−0.0044 (9)	0.0102 (8)	0.0000 (8)
C5	0.0532 (14)	0.0362 (12)	0.0301 (10)	−0.0089 (10)	0.0073 (10)	−0.0024 (9)
C6	0.0590 (14)	0.0384 (12)	0.0253 (10)	0.0030 (10)	0.0112 (9)	−0.0040 (9)
C7	0.0472 (12)	0.0390 (12)	0.0259 (9)	0.0067 (10)	0.0155 (9)	0.0021 (8)
C8	0.0415 (12)	0.0342 (11)	0.0316 (10)	−0.0045 (9)	0.0088 (9)	0.0030 (8)
O1W	0.0399 (9)	0.0472 (11)	0.0491 (10)	−0.0032 (7)	0.0223 (8)	0.0074 (8)
O2W	0.089 (3)	0.099 (3)	0.182 (6)	0.000	0.037 (3)	0.000
P1	0.0331 (4)	0.0381 (5)	0.0288 (5)	0.000	0.0101 (3)	0.000
F1	0.0530 (11)	0.0404 (11)	0.0437 (10)	0.000	0.0233 (9)	0.000
F2	0.0629 (14)	0.0399 (12)	0.0721 (15)	0.000	0.0060 (12)	0.000
F3	0.0609 (9)	0.0684 (10)	0.0307 (8)	0.0100 (7)	0.0136 (6)	−0.0075 (6)
F4	0.0354 (8)	0.0632 (10)	0.0596 (10)	−0.0034 (6)	0.0153 (7)	−0.0023 (7)

Geometric parameters (Å, º)

N1—C2	1.331 (3)	C5—C6	1.377 (4)
N1—C1	1.333 (3)	C5—H5	0.91 (3)
N2—C7	1.340 (3)	C6—C7	1.372 (4)
N2—C3	1.349 (3)	C6—H6	0.99 (3)
N2—H2N	0.91 (3)	C7—H7	0.92 (3)
O1—C8	1.222 (3)	O1W—H1WA	0.79 (4)
O2—C8	1.279 (3)	O1W—H1WB	0.89 (4)
O2—H2O	1.206 (5)	O2W—H2WA	0.8946
C1—C1^i	1.414 (4)	P1—F3^ii	1.5897 (14)
C1—C8	1.522 (3)	P1—F3	1.5897 (14)
C2—C2^i	1.409 (4)	P1—F2	1.591 (2)
C2—C3	1.482 (3)	P1—F4^ii	1.5948 (14)
C3—C4	1.380 (3)	P1—F4	1.5948 (14)
C4—C5	1.393 (3)	P1—F1	1.615 (2)
C4—H4	1.05 (3)
C2—N1—C1	120.49 (17)	N2—C7—C6	120.4 (2)
C7—N2—C3	122.12 (19)	N2—C7—H7	112.7 (17)
C7—N2—H2N	116.9 (18)	C6—C7—H7	126.8 (17)
C3—N2—H2N	121.0 (19)	O1—C8—O2	123.6 (2)
C8—O2—H2O	107 (3)	O1—C8—C1	117.53 (19)
N1—C1—C1^i	118.69 (12)	O2—C8—C1	118.9 (2)
N1—C1—C8	112.74 (17)	H1WA—O1W—H1WB	104 (4)
C1^i—C1—C8	128.56 (12)	F3^ii—P1—F3	178.51 (13)
N1—C2—C2^i	118.84 (11)	F3^ii—P1—F2	90.75 (6)
N1—C2—C3	115.22 (16)	F3—P1—F2	90.75 (6)
C2^i—C2—C3	125.84 (11)	F3^ii—P1—F4^ii	89.88 (8)
N2—C3—C4	119.21 (18)	F3—P1—F4^ii	90.11 (8)
N2—C3—C2	117.27 (17)	F2—P1—F4^ii	90.30 (7)
C4—C3—C2	123.29 (17)	F3^ii—P1—F4	90.11 (8)
C3—C4—C5	119.3 (2)	F3—P1—F4	89.88 (8)
C3—C4—H4	126.3 (15)	F2—P1—F4	90.30 (7)
C5—C4—H4	114.3 (15)	F4^ii—P1—F4	179.41 (13)
C6—C5—C4	119.8 (2)	F3^ii—P1—F1	89.25 (6)
C6—C5—H5	119.8 (19)	F3—P1—F1	89.25 (6)
C4—C5—H5	120.3 (19)	F2—P1—F1	180.0
C7—C6—C5	119.1 (2)	F4^ii—P1—F1	89.70 (7)
C7—C6—H6	119.7 (18)	F4—P1—F1	89.70 (7)
C5—C6—H6	121.1 (18)
C2—N1—C1—C1^i	9.0 (3)	N2—C3—C4—C5	−0.9 (3)
C2—N1—C1—C8	−169.71 (17)	C2—C3—C4—C5	−175.14 (19)
C1—N1—C2—C2^i	9.2 (3)	C3—C4—C5—C6	0.4 (3)
C1—N1—C2—C3	−167.13 (17)	C4—C5—C6—C7	0.0 (3)
C7—N2—C3—C4	1.0 (3)	C3—N2—C7—C6	−0.7 (3)
C7—N2—C3—C2	175.63 (17)	C5—C6—C7—N2	0.2 (3)
N1—C2—C3—N2	−30.2 (2)	N1—C1—C8—O1	13.5 (3)
C2^i—C2—C3—N2	153.7 (2)	C1^i—C1—C8—O1	−165.0 (3)
N1—C2—C3—C4	144.14 (19)	N1—C1—C8—O2	−168.02 (19)
C2^i—C2—C3—C4	−31.9 (3)	C1^i—C1—C8—O2	13.5 (4)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2O···O2^i	1.21 (1)	1.21 (1)	2.405 (4)	171 (6)
N2—H2N···O1W	0.91 (3)	1.77 (3)	2.683 (3)	177 (3)
O1W—H1WA···O1^iii	0.79 (4)	1.98 (4)	2.739 (2)	160 (4)
O1W—H1WB···O1	0.89 (4)	1.96 (4)	2.841 (3)	171 (4)
O2W—H2WA···O2^ii	0.89	2.07	2.815 (4)	140

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