Hydrogen bonding and π–π inter­actions in 1-benzofuran-2,3-dicarboxylic acid and its 1:1 cocrystals with pyridine, phenazine and 1,4-phenyl­enediamine

The structure of 1-benzofuran-2,3-dicarboxylic acid (BFDC), C₁₀H₆O₅, (I), exhibits an intra­molecular hydrogen bond between one –COOH group and the other, while the second carboxyl function is involved in inter­molecular hydrogen bonding to neighbouring species. The latter results in the formation of flat one-dimensional hydrogen-bonded chains in the crystal structure, which are π–π stacked along the normal to the plane of the mol­ecular framework, forming a layered structure. 1:1 Cocrystallization of BFDC with pyridine, phenazine and 1,4-phenyl­enediamine is associated with H-atom transfer from BFDC to the base and charge-assisted hydrogen bonding between the BFDC⁻ monoanion and the corresponding ammonium species, while preserving, in all cases, the intra­molecular hydrogen bond between the carboxyl and carboxyl­ate functions. The pyridinium 2-carboxyl­ato-1-benzofuran-3-carboxylic acid, C₅H₆N⁺·C₁₀H₅O₅⁻, (II), and phenazinium 3-carboxyl­ato-1-benzofuran-2-carboxylic acid, C₁₂H₉N₂⁺·C₁₀H₅O₅⁻, (III), adducts form discrete hydrogen-bonded ion-pair entities. In the corresponding crystal structures, the two components are arranged in either segregated or mixed π–π stacks, respectively. On the other hand, the structure of 4-amino­anilinium 2-carboxyl­ato-1-benzofuran-3-carboxylic acid, C₆H₉N₂⁺·C₁₀H₅O₅⁻, (IV), exhibits an inter­molecular hydrogen-bonding network with three-dimensional connectivity. Moreover, this fourth structure exhibits induction of supra­molecular chirality by the extended hydrogen bonding, leading to a helical arrangement of the inter­acting moieties around 2₁ screw axes. The significance of this study is that it presents the first crystallographic characterization of pure BFDC, and manifestation of its cocrystallization with a variety of weakly basic amine mol­ecules. It confirms the tendency of BFDC to preserve its intra­molecular hydrogen bond and to prefer a monoanionic form in supra­molecular association with other components. The aromaticity of the flat benzofuran residue plays an important role in directing either homo- or heteromolecular π–π stacking in the first three structures, while the occurrence of a chiral architecture directed by multiple hydrogen bonding is the dominant feature in the fourth.

S1. Comment

This study is part of an extended research project directed at the detailed evaluation of the structural features and functionality of the 1-benzofuran-2,3-dicarboxylic acid (BFDC) building block, along with the formulation of new supramolecular materials of this compound with a variety of transition metals and complimentary organic ligands. In recent publications (Koner & Goldberg, 2009a,b,c) we showed that BFDC can be readily deprotonated, singly or doubly, to the corresponding anions BFDC^- and BFDC^2- and form coordination compounds with 2+ and 3+ metal ions. The monoanions (obtained in weak basic conditions) engage in the formation of discrete complexes, while the dianions (available in higher pH environments) can afford extended coordination polymers. It also appeared that the first deprotonation of BFDC occurs favourably on the carboxylic acid group which is closer to the electron-withdrawing etheral site. In the resulting BFDC^- anion the H atom of the second carboxylic function is involved in an intramolecular hydrogen bond to the carboxylate group. The structure of free BFDC has not been reported before, and its supramolecular/coordination chemistry has not been studied prior to our work. Within the above context, this presentation describes the first crystallographic characterization of the pure BFDC moiety, (I). In addition, the structures of the 1:1 cocrystals of BFDC with pyridine, phenazine and 1,4-phenylenediamine, the formation of which is associated with H-atom transfer from the acidic BFDC to the corresponding Lewis base, are also described, (II), (III) and (IV). The four compounds crystallized by serendipity during our attemps to formulate coordination polymers of this ligand with various lanthanide metal ions.

Ellipsoid plots of compounds (I)–(IV) are shown in Fig. 1. The only conformational degrees of freedom in the BDFC framework involve free rotations of the carboxylic/carboxylate functions with respect to the rigid aromatic benzofuran residue. They are efficiently utilized for optimization of the intra- and intermolecular hydrogen bonding in (I)–(IV).

The observed structure of (I) involves the formation of an intramolecular hydrogen bond between the two ortho-substituted carboxylic acid functions (Fig. 1a). The more acidic of the two groups (C10/O11/O12) acts as an H-atom donor in this bond (O11—H11···O15; Table 1), with graph-set notation S(7) (Bernstein et al., 1995). The aromatic benzofuran fragment (O1/C2–C9) is essentially planar. The two carboxylic acid groups are slightly twisted with respect to this plane, with dihedral angles of 9.2 (2) and 5.8 (2)° for fragments C10/O11/O12 and C13/O14/O15, respectively. Additional H-atom donor (O14—H14) and acceptor (O12) sites diverge outward from the flat molecular structure and are accessible to intermolecular hydrogen bonding (Table 1). This gives rise to the formation of supramolecular hydrogen-bonded chains of BFDC, involving molecular units displaced along the c axis of the crystal structure [graph-set notation C(7)]. The chain assemblies are flat, lying parallel to the (100) plane of the crystal structure at approximately x = 1/4. Neighbouring symmetry-related hydrogen-bonded chains are centred at either x = 1/4 or x = 3/4 and are roughly parallel to one another, yielding a layered intermolecular arrangement (Fig. 2).

In addition to the common dispersion forces that stabilize the crystal packing in molecular crystals, the two following sets of van der Waals type interactions between adjacent chains in (I) deserve specific attention. Along the a axis of the crystal structure, the chain arrays related by the glide-plane symmetry are offset stacked on top of one other. The mean interplanar distance between the partly overlapping benzofuran residues (O1/C2–C9) at (x, y, z) and (x + 1/2, -y + 1/2, z + 1/2) is 3.27 (1) Å. More specifically, there is an apparent π–π interaction between both the furan and the benzene rings at (x, y, z) and the benzene ring at (x + 1/2, -y + 1/2, z + 1/2). The corresponding ring-centroid distances, the dihedral angles between the planes concerned and the interplanar spacings are 3.83 Å, 1.27° and 3.32 Å, and 3.86 Å, 0° and 3.52 Å, respectively. Along the b axis, the crystal packing is further stabilized by weak C—H···O interactions between molecules interrelated by the screw-axis symmetry (Table 1), which involve the aryl termini of one molecule and the carboxylic acid O atoms of an adjacent unit at the same z level but shifted along the b axis. The entire crystal packing is thus stabilized by O—H···O hydrogen bonding, π–π stacking and weak C—H···O interactions along the c, a and b axes, respectively.

Furan-dicarboxylic acids have been shown to be relatively strong acids (Xing & Glen, 2002; Ostrow & Mukerjee, 2007) with pK_a values below 3. The extended benzofuran aromatic framework provides an even higher stabilization of the negative charge after deprotonation, thus lowering this value even further. Not surprisingly, therefore, weakly basic environments are adequate to effect ionization of BFDC (Koner & Goldberg, 2009a). Cocrystallization of BFDC with pyridine was indeed associated with H-atom transfer from BFDC to the pyridine base, yielding the charge-assisted hydrogen-bonded heteromeric entity (II) of the two ions thus formed. This H-atom transfer occurred as expected from the more acidic carboxylic group C10/OH11/O12 to the N16 pyridine site (Fig. 1b). The molecular structure of the BFDC^- ion is further characterized by an intramolecular hydrogen bond from the second carboxylic acid group (C13/O14/O15) to the deprotonated carboxylate group (Table 2). The graph-set notations for the inter- and intramolecular hydrogen bonds of (II) are D(2) and S(7), respectively. The two interacting moieties are essentially planar, but they deviate slightly from coplanarity, the dihedral angle between the O1/C2–C9 and N16/C17–C21 planes being 13.13 (7)°. They are offset stacked in segregated columns along the a axis of the crystal structure of (II), as shown in Fig. 3. The interplanar distance between neighbouring pyridinium units (N16/C17–C21), with minor overlapping between them at (x, y, z) and (1 + x, y, z) along the stack, is 3.324 (7) Å, while that between the correspondingly better overlapping benzofuran rings (O1/C2–C9) is slightly larger at 3.393 (6) Å. In the latter case the specific interaction between the benzene ring at (x, y, z) and the furan ring at (x + 1, y, z) is characterized by a ring-centroid distance of 3.74 Å, a dihedral angle between the two planes of 0.3° and an interplanar spacing of 3.39 Å. A series of relatively short C—H···O approaches between neighbouring molecules of the two components (Table 2) contributes to the stabilization of the columnar crystal packing of (II).

The observed structure of (III) is also characterized by an intercomponent hydrogen bond (N28—H···O14; Table 3) associated with H-atom transfer from one of the carboxylic acid groups to the aromatic N-atom site (Fig. 1c). The molecular structure also accommodates an intramolecular O11—H···O15 hydrogen bond (Table 3). Somewhat surprisingly, the hydrogen bonding between the BFDC^- anion and the phenazine cation this time involves the apparently less acidic carboxylic group C13/O14/O15 (see below). A possible explanation for this deviation from the more commonly observed trend in earlier examples (Koner & Goldberg, 2009a,b,c), as well as in compounds (II) and (IV) of this work, relates to the comparable size and flat shape of the aromatic BFDC^- and phenazinium components (the two species are essentially planar). The individual moieties of the hydrogen-bonded pair are coplanar. In the crystal structure, the hydrogen-bonded dimers stack along [110] in an offset manner, and yet the preferred organization in this structure represents mixed stacking [rather than homomeric as in (II)] with alternating and partially overlapping BFDC^- and phenazinium units (Fig. 4). The mean interplanar separations from the electron-deficient phenazinium framework (C16–C20/N21/C22–C27/N28/C29) at (x, y, z) and the two adjacent electron-rich BFDC^- (O1/C2–C10/O11/O12/C13/O14/O15) planes at (x + 1, y + 1, z) and (x + 1, y, z) are 3.36 (3) and 3.43 (3) Å, respectively, indicative of a possible π–π charge-transfer interaction between the component species along the stack (Goldberg, 1975; Goldberg & Shmueli, 1973). Specific overlapping contacts occur between the central ring of the phenazinium ion (C20/N21/C22/C27/N28/C29) and the benzene ring of BFDC^- (C4–C9), and between the peripheral phenazinium (C22–C27) and furan (O1/C2–C4/C9) fragments. The corresponding ring-centroid distances, the dihedral angles between the planes concerned and the interplanar spacings are 3.86 Å, 1.58° and 3.37 Å, and 3.84 Å, 1.56° and 3.37 Å, respectively. Optimization of the stacking interactions may affect the utilization of the less expected mode of intermolecular hydrogen bonding in this structure. It is also noted that the second N-atom site of phenazine is involved in a weak C—H···N interaction (Table 3), which operates between units of neighbouring stacks along with the C—H···O contacts.

Structure (IV) also represents a hydrogen-bonded adduct of BFDC^- with a diamine, but here both N-atom sites are involved in conventional hydrogen bonds with neighbouring species, giving rise to the formation of an extended hydrogen-bonding pattern throughout the crystal structure. This is facilitated by the fact that the terminal amine groups of the 1-ammonium-4-amino-phenylene moiety act not only as H-atom acceptors from, but also as H-atom donors to, the surrounding molecules. As in (II), single H-atom transfer occurs from the more acidic function of the dicarboxylic acid to the N-ligand, while preserving the intramolecular hydrogen-bonding in the resulting BFDC^- ion (Fig. 1d); the respective graph-set descriptors are D(2) and S(7). The ion pair thus formed bears five H-atom donors (the H atoms on N16 and N23) and potentially five H-atom acceptors (O11, O12, O14, O15 and N23), facilitating the formation of an extended intermolecular hydrogen-bonding network between the two multidentate components in three dimensions (Table 4; the C—H···O contacts are of minor significance in this structure and have been omitted from this table). The various chain segments of this network in the different directions are denoted by C²₂(6), C²₂(7), C²₂(13) and C²₂(14) graph-set descriptors.

A partial illustration of the intermolecular networking is given in Fig. 5. While it is somewhat problematic to exhibit a three-dimensional connectivity scheme in a two-dimensional projection, we prefer to emphasize a different point in this figure. BFDC and 1,4-phenylenediamine are non-chiral species, and yet, upon ion-pair formation, they crystallize in a chiral architecture of space group symmetry P2₁, as a result of the extended supramolecular hydrogen bonding. This is an interesting manifestation of the induction of supramolecular chirality, occasionally observed in crystals of achiral salts (Goldberg, 2009; Tanaka et al., 2006). Fig. 5 shows that the two ionic components in (IV) are arranged along the hydrogen-bonded chains in an alternating manner, and that optimization of the hydrogen bonding imparts 2₁ helicity to the hydrogen-bonded arrays. No rigorous explanation of the occurrence of the supramolecular chirality phenomenon can be provided at this point, apart from indicating that in the earlier observed examples it was also induced by the presence of extended arrays of hydrogen bonds between the interacting components (Goldberg, 2008; Vinodu & Goldberg, 2005).

In summary, this study characterizes the molecular structure of pure benzofuran dicarboxylic acid. It confirms its tendency to deprotonate into a monoanionic form in mild basic environments, transferring the H atom to one of the N-atom sites of the Lewis base present in the reaction/crystallization mixture. The proximal positions of the two carboxylic acid functions promote the formation of an intramolecular hydrogen bond. Evidently, the BFDC^- entity is an excellent H-atom acceptor in hydrogen bonding, facilitating its supramolecular association with a variety of mono- or polydentate H-atom donors.

S2. Experimental

All the reactants and solvents were obtained commercially. Compounds (I)–(IV) were obtained unintentionally, while trying to prepare coordination polymers of BFDC with various oxophilic lanthanide ions in basic environments. Compounds (I)–(IV) thus represent byproducts of these efforts.

Compound (I) was obtained by dissolving a mixture of BFDC (0.1 mmol, 0.021 g) and gadolinium oxalate hydrate (0.1 mmol, 0.055 g) in water (5 ml) and HCl (32%, 2 drops). The resulting solution was sealed in a bath reactor for 3 d at 373 K. It was then left to evaporate slowly at room temperature, yielding crystals after 12 d.

For (II), BFDC (0.1 mmol, 0.021 g) was reacted with Tb(NO₃)₃.6H₂O (0.1 mmol, 0.055 g) in a 1:1 mixture of water and pyridine (5 ml), and sealed in a bath reactor at 373 K for 3 d. The product was filtered and left to evaporate slowly at room temperature, yielding BFDC–pyridine cocrystals after about one month.

For (III), a mixture of BFDC (0.4 mmol, 0.082 g), phenazine (0.4 mmol, 0.073 g) and PrCl₃.7H₂O (0.8 mmol, 0.198 g) was dissolved in a 1:1 mixture of methanol and tetrahydrofuran (20 ml). The resulting solution was refluxed for 3 h, filtered and left to evaporate slowly. Yellow–reddish [Yellow in CIF - please clarify] crystals appeared after two weeks.

Compound (IV) was obtained by mixing BFDC (0.4 mmol, 0.082 g), PrCl₃.7H₂O (0.8 mmol, 0.197 g) and 1,4-phenylenediamine (0.4 mmol, 0.042 g) in a 3:1 mixture of tetrahydrofuran and water (20 ml). The resulting solution was refluxed overnight and then filtered, and the liquid was left to evaporate slowly at room temperature. Crystals of (IV) suitable for X-ray diffraction studies were obtained after 4 d.

S3. Refinement

H atoms bound to C atoms were located in calculated positions and constrained to ride on their parent atoms, with C—H = 0.95 Å and with U_iso(H) = 1.2U_eq(C). H atoms bound to N and O atoms were located in difference Fourier maps and their coordinates were refined freely, with U_iso(H) = 1.2U_eq(N) or 1.5U_eq(O) [Please check rephrasing].

In all cases but one, the distribution of the C—O bond distances within the carboxylic/carboxylate groups was consistent with their being in either a protonated or a deprotonated delocalized state. The only exception is exhibited by the bonds C10—O11 = 1.290 (3) Å and C10—O12 = 1.216 (4) Å in (IV), which seem to better represent a carboxylic acid rather than a carboxylate functionality. However, a prominent residual electron-density peak was located near atom N16 rather than O11, and remained there after a few cycles of least-squares refinement of its coordinates (as an H atom), which thus suggests that proton transfer has occurred at least partially from atom O11 to N16.

Notably, the electron-deficient N—H bonds involved in hydrogen bonding to the anionic BFDC^- species in (II) and (III) were refined to be slightly longer than in neutral amines, as expected (Tables 2 and 3). As the absolute configuration could not be determined reliably in the noncentrosymmetric light-atom structures of (III) and (IV), the Friedel pairs were merged in the crystallographic refinements of the corresponding structural models using the MERG3 parameter in SHELXL97 (Sheldrick, 2008), while reducing the data-to-parameter ratio to about 8.

Computing details

For all compounds, data collection: COLLECT (Nonius, 1999); cell refinement: DENZO (Otwinowski & Minor, 1997); data reduction: DENZO (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR97 (Altomare et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEPIII (Burnett & Johnson, 1996) and Mercury (Macrae et al., 2006); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

	Fig. 1. The asymmetric units in (a) (I), (b) (II), (c) (III) and (d) (IV). Displacement ellipsoids are drawn at the 50% probability level at ca 110 K and H atoms are shown as small spheres of arbitrary radii. Intra- and intermolecular hydrogen bonds are indicated by dashed lines.
	Fig. 2. Ball-and-stick illustration of the crystal structure of (I). Note the partial overlap between BFDC molecules stacked along the a axis. Intra- and intermolecular hydrogen bonds in this layered structure are denoted by dashed lines.
	Fig. 3. Wireframe presentation of the crystal structure of (II), viewed approximately down the a axis, showing the segregated stacking of the BFBC^- and pyridinium components. Hydrogen bonds are indicated by dashed lines.
	Fig. 4. The crystal packing of (III) (wireframe). Note the arrangement of the BFDC^- and phenazinium units in an alternating manner in heteromeric stacks (along the b axis, as marked by the interplanar distances) with partial overlap between them. Neighbouring columns are related to one another by the glide symmetry. Hydrogen bonds are indicated by dashed lines.
	Fig. 5. Ball-and-stick illustration of the crystal structure of (IV), showing the helical arrangement of the alternating constituent moieties around the 21^b screw axis, and the extended intermolecular hydrogen bonding (dashed lines) along it. Additional hydrogen bonds which operate between neighbouring helices (Table 4) are not shown.

(I) 1-Benzofuran-2,3-dicarboxylic acid

Crystal data

C10H6O5	F(000) = 424
Mr = 206.15	Dx = 1.616 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 1888 reflections
a = 6.9614 (3) Å	θ = 3.3–27.9°
b = 18.2529 (7) Å	µ = 0.13 mm^−1
c = 7.4731 (3) Å	T = 110 K
β = 116.840 (2)°	Prism, colourless
V = 847.28 (6) Å^3	0.45 × 0.35 × 0.20 mm
Z = 4

Data collection

Nonius KappaCCD area-detector diffractometer	1517 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.035
Graphite monochromator	θmax = 27.9°, θmin = 3.3°
Detector resolution: 12.8 pixels mm^-1	h = 0→9
1 deg. ϕ and ω scans	k = 0→23
7021 measured reflections	l = −9→8
1982 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)] = 0.049	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.141	H atoms treated by a mixture of independent and constrained refinement
S = 1.07	w = 1/[σ^2(Fo^2) + (0.0934P)^2 + 0.0306P] where P = (Fo^2 + 2Fc^2)/3
1982 reflections	(Δ/σ)max = 0.001
142 parameters	Δρmax = 0.31 e Å^−3
0 restraints	Δρmin = −0.31 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
O1	0.24362 (17)	0.34674 (6)	0.67414 (16)	0.0258 (3)
C2	0.2572 (2)	0.40425 (9)	0.5639 (2)	0.0236 (4)
C3	0.2783 (2)	0.38137 (9)	0.3988 (2)	0.0236 (4)
C4	0.2819 (2)	0.30208 (9)	0.4067 (2)	0.0233 (4)
C5	0.3014 (3)	0.24582 (9)	0.2891 (3)	0.0283 (4)
H5	0.3187	0.2561	0.1726	0.034*
C6	0.2944 (3)	0.17430 (10)	0.3489 (3)	0.0325 (4)
H6	0.3105	0.1351	0.2731	0.039*
C7	0.2642 (2)	0.15829 (9)	0.5178 (3)	0.0322 (4)
H7	0.2567	0.1086	0.5516	0.039*
C8	0.2452 (2)	0.21307 (10)	0.6364 (3)	0.0308 (4)
H8	0.2251	0.2026	0.7514	0.037*
C9	0.2573 (2)	0.28443 (9)	0.5771 (2)	0.0249 (4)
C10	0.2505 (2)	0.47676 (9)	0.6501 (2)	0.0254 (4)
O11	0.23612 (18)	0.53520 (6)	0.54161 (17)	0.0293 (3)
H11	0.252 (3)	0.5254 (11)	0.419 (3)	0.035*
O12	0.25603 (19)	0.48259 (7)	0.81497 (18)	0.0327 (3)
C13	0.2827 (2)	0.42772 (9)	0.2395 (2)	0.0250 (4)
O14	0.30575 (19)	0.39071 (7)	0.10104 (18)	0.0308 (3)
H14	0.290 (3)	0.4214 (12)	−0.010 (3)	0.037*
O15	0.26407 (18)	0.49490 (7)	0.23463 (17)	0.0298 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0327 (6)	0.0201 (6)	0.0259 (6)	−0.0004 (4)	0.0144 (5)	0.0018 (4)
C2	0.0266 (7)	0.0194 (8)	0.0234 (7)	−0.0001 (6)	0.0101 (6)	0.0019 (6)
C3	0.0245 (7)	0.0205 (9)	0.0249 (8)	−0.0014 (6)	0.0103 (6)	0.0018 (6)
C4	0.0234 (7)	0.0195 (8)	0.0244 (7)	−0.0025 (5)	0.0083 (6)	−0.0026 (6)
C5	0.0303 (8)	0.0234 (9)	0.0281 (8)	−0.0014 (6)	0.0106 (7)	−0.0033 (6)
C6	0.0297 (8)	0.0240 (9)	0.0369 (9)	−0.0012 (6)	0.0091 (7)	−0.0033 (7)
C7	0.0279 (8)	0.0192 (8)	0.0409 (10)	−0.0020 (6)	0.0080 (7)	0.0036 (7)
C8	0.0273 (8)	0.0276 (10)	0.0336 (9)	−0.0022 (6)	0.0105 (7)	0.0076 (7)
C9	0.0246 (7)	0.0220 (9)	0.0258 (8)	−0.0018 (6)	0.0094 (6)	−0.0001 (6)
C10	0.0274 (8)	0.0233 (9)	0.0245 (8)	0.0007 (6)	0.0108 (6)	0.0014 (6)
O11	0.0395 (7)	0.0219 (7)	0.0279 (6)	0.0011 (4)	0.0165 (5)	0.0017 (4)
O12	0.0446 (7)	0.0293 (7)	0.0264 (6)	0.0010 (5)	0.0181 (5)	−0.0012 (5)
C13	0.0274 (7)	0.0223 (9)	0.0247 (8)	−0.0006 (6)	0.0113 (6)	−0.0012 (6)
O14	0.0425 (6)	0.0257 (7)	0.0274 (6)	−0.0005 (5)	0.0187 (5)	−0.0011 (5)
O15	0.0409 (7)	0.0210 (7)	0.0299 (6)	0.0013 (5)	0.0181 (5)	0.0029 (4)

Geometric parameters (Å, º)

O1—C2	1.3640 (19)	C6—H6	0.9500
O1—C9	1.3750 (19)	C7—C8	1.382 (3)
C2—C3	1.372 (2)	C7—H7	0.9500
C2—C10	1.482 (2)	C8—C9	1.391 (2)
C3—C4	1.448 (2)	C8—H8	0.9500
C3—C13	1.472 (2)	C10—O12	1.220 (2)
C4—C9	1.397 (2)	C10—O11	1.316 (2)
C4—C5	1.397 (2)	O11—H11	0.99 (2)
C5—C6	1.388 (2)	C13—O15	1.232 (2)
C5—H5	0.9500	C13—O14	1.305 (2)
C6—C7	1.401 (3)	O14—H14	0.96 (2)
C2—O1—C9	106.13 (12)	C8—C7—H7	119.2
O1—C2—C3	111.95 (13)	C6—C7—H7	119.2
O1—C2—C10	113.61 (13)	C7—C8—C9	115.87 (16)
C3—C2—C10	134.42 (15)	C7—C8—H8	122.1
C2—C3—C4	105.92 (13)	C9—C8—H8	122.1
C2—C3—C13	127.03 (15)	O1—C9—C8	125.32 (15)
C4—C3—C13	126.94 (14)	O1—C9—C4	110.86 (13)
C9—C4—C5	119.36 (15)	C8—C9—C4	123.81 (15)
C9—C4—C3	105.12 (13)	O12—C10—O11	120.69 (15)
C5—C4—C3	135.53 (15)	O12—C10—C2	121.61 (15)
C6—C5—C4	117.49 (16)	O11—C10—C2	117.70 (15)
C6—C5—H5	121.3	C10—O11—H11	114.5 (12)
C4—C5—H5	121.3	O15—C13—O14	122.77 (15)
C5—C6—C7	121.84 (16)	O15—C13—C3	123.73 (15)
C5—C6—H6	119.1	O14—C13—C3	113.50 (15)
C7—C6—H6	119.1	C13—O14—H14	111.9 (13)
C8—C7—C6	121.60 (16)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O11—H11···O15	0.99 (2)	1.52 (2)	2.4990 (16)	168.6 (19)
O14—H14···O12^i	0.96 (2)	1.66 (2)	2.6143 (17)	172.7 (19)
C7—H7···O12^ii	0.95	2.52	3.468 (2)	173

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

(II) Pyridinium 2-carboxylato-1-benzofuran-3-carboxylic acid

Crystal data

C5H6N^+·C10H5O5^−	F(000) = 592
Mr = 285.25	Dx = 1.528 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 2696 reflections
a = 3.7576 (1) Å	θ = 2.5–27.9°
b = 18.3933 (6) Å	µ = 0.12 mm^−1
c = 17.9788 (7) Å	T = 110 K
β = 93.5522 (11)°	Needle, colourless
V = 1240.21 (7) Å^3	0.50 × 0.10 × 0.10 mm
Z = 4

Data collection

Nonius KappaCCD area-detector diffractometer	1675 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.067
Graphite monochromator	θmax = 27.9°, θmin = 2.5°
Detector resolution: 12.8 pixels mm^-1	h = 0→4
1 deg. ϕ and ω scans	k = 0→24
10181 measured reflections	l = −23→23
2897 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)] = 0.052	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.139	H atoms treated by a mixture of independent and constrained refinement
S = 0.97	w = 1/[σ^2(Fo^2) + (0.073P)^2] where P = (Fo^2 + 2Fc^2)/3
2897 reflections	(Δ/σ)max < 0.001
196 parameters	Δρmax = 0.35 e Å^−3
0 restraints	Δρmin = −0.33 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
O1	0.3813 (3)	−0.03491 (8)	0.71947 (8)	0.0210 (4)
C2	0.3553 (5)	0.03917 (11)	0.72630 (11)	0.0189 (5)
C3	0.2207 (5)	0.05777 (11)	0.79301 (11)	0.0197 (5)
C4	0.1552 (5)	−0.00923 (12)	0.83098 (11)	0.0200 (5)
C5	0.0238 (5)	−0.02886 (13)	0.89954 (12)	0.0240 (5)
H5	−0.0491	0.0070	0.9334	0.029*
C6	0.0036 (5)	−0.10205 (12)	0.91624 (12)	0.0257 (5)
H6	−0.0819	−0.1164	0.9627	0.031*
C7	0.1060 (5)	−0.15561 (13)	0.86651 (12)	0.0254 (5)
H7	0.0853	−0.2054	0.8796	0.030*
C8	0.2367 (5)	−0.13754 (12)	0.79863 (12)	0.0231 (5)
H8	0.3071	−0.1734	0.7645	0.028*
C9	0.2583 (5)	−0.06430 (11)	0.78375 (11)	0.0199 (5)
C10	0.4765 (5)	0.08092 (12)	0.66180 (12)	0.0217 (5)
O11	0.5909 (4)	0.04490 (8)	0.60852 (8)	0.0270 (4)
O12	0.4586 (4)	0.14932 (8)	0.66389 (8)	0.0275 (4)
C13	0.1479 (5)	0.13089 (13)	0.82411 (12)	0.0240 (5)
O14	0.2145 (4)	0.18934 (8)	0.78447 (9)	0.0281 (4)
H14	0.306 (6)	0.1739 (13)	0.7370 (14)	0.034*
O15	0.0275 (4)	0.13638 (9)	0.88545 (9)	0.0312 (4)
N16	0.8733 (4)	0.12783 (10)	0.50874 (10)	0.0212 (4)
H16	0.759 (5)	0.0932 (12)	0.5495 (12)	0.025*
C17	0.9583 (5)	0.09473 (12)	0.44592 (12)	0.0225 (5)
H17	0.9110	0.0444	0.4390	0.027*
C18	1.1151 (5)	0.13408 (12)	0.39114 (12)	0.0236 (5)
H18	1.1818	0.1109	0.3469	0.028*
C19	1.1735 (5)	0.20767 (12)	0.40165 (12)	0.0247 (5)
H19	1.2777	0.2356	0.3642	0.030*
C20	1.0797 (5)	0.24058 (12)	0.46692 (12)	0.0240 (5)
H20	1.1166	0.2912	0.4745	0.029*
C21	0.9324 (5)	0.19892 (12)	0.52042 (12)	0.0240 (5)
H21	0.8722	0.2206	0.5659	0.029*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0235 (8)	0.0195 (9)	0.0206 (8)	−0.0002 (6)	0.0052 (6)	0.0013 (6)
C2	0.0154 (10)	0.0185 (12)	0.0229 (12)	0.0000 (8)	0.0011 (8)	−0.0006 (9)
C3	0.0145 (10)	0.0231 (12)	0.0215 (11)	0.0003 (8)	0.0011 (8)	−0.0015 (9)
C4	0.0162 (10)	0.0210 (12)	0.0227 (12)	0.0005 (8)	−0.0004 (8)	−0.0005 (9)
C5	0.0212 (11)	0.0292 (14)	0.0217 (12)	−0.0004 (9)	0.0033 (8)	−0.0026 (10)
C6	0.0206 (11)	0.0328 (14)	0.0242 (12)	−0.0010 (9)	0.0042 (8)	0.0060 (10)
C7	0.0209 (11)	0.0257 (13)	0.0296 (13)	−0.0010 (8)	0.0015 (9)	0.0046 (10)
C8	0.0200 (11)	0.0245 (13)	0.0245 (12)	0.0010 (8)	0.0007 (8)	0.0001 (9)
C9	0.0163 (10)	0.0237 (13)	0.0196 (11)	−0.0015 (8)	0.0015 (8)	0.0031 (9)
C10	0.0157 (10)	0.0234 (13)	0.0260 (12)	−0.0001 (8)	0.0011 (8)	0.0007 (10)
O11	0.0305 (8)	0.0268 (9)	0.0248 (9)	−0.0011 (6)	0.0103 (6)	0.0007 (7)
O12	0.0333 (9)	0.0211 (10)	0.0285 (9)	−0.0012 (6)	0.0059 (6)	0.0017 (7)
C13	0.0178 (10)	0.0265 (14)	0.0278 (13)	0.0007 (8)	0.0015 (9)	−0.0008 (10)
O14	0.0367 (9)	0.0204 (9)	0.0276 (9)	0.0013 (6)	0.0062 (7)	−0.0008 (7)
O15	0.0363 (9)	0.0298 (10)	0.0286 (10)	0.0051 (7)	0.0103 (7)	−0.0043 (7)
N16	0.0187 (9)	0.0232 (11)	0.0217 (10)	0.0005 (7)	0.0026 (7)	0.0028 (8)
C17	0.0210 (10)	0.0200 (12)	0.0263 (12)	−0.0003 (8)	0.0016 (8)	−0.0010 (9)
C18	0.0188 (10)	0.0304 (13)	0.0217 (12)	0.0000 (8)	0.0021 (8)	−0.0019 (9)
C19	0.0175 (10)	0.0307 (13)	0.0259 (12)	−0.0015 (9)	0.0014 (8)	0.0060 (10)
C20	0.0205 (11)	0.0186 (12)	0.0328 (13)	−0.0006 (8)	0.0020 (8)	0.0003 (10)
C21	0.0204 (10)	0.0275 (14)	0.0243 (12)	0.0020 (8)	0.0019 (8)	−0.0023 (10)

Geometric parameters (Å, º)

O1—C2	1.372 (2)	C10—O11	1.262 (3)
O1—C9	1.381 (2)	C13—O15	1.222 (3)
C2—C3	1.373 (3)	C13—O14	1.322 (3)
C2—C10	1.486 (3)	O14—H14	0.98 (2)
C3—C4	1.437 (3)	N16—C17	1.339 (3)
C3—C13	1.488 (3)	N16—C21	1.341 (3)
C4—C9	1.392 (3)	N16—H16	1.08 (2)
C4—C5	1.403 (3)	C17—C18	1.383 (3)
C5—C6	1.382 (3)	C17—H17	0.9500
C5—H5	0.9500	C18—C19	1.382 (3)
C6—C7	1.400 (3)	C18—H18	0.9500
C6—H6	0.9500	C19—C20	1.385 (3)
C7—C8	1.384 (3)	C19—H19	0.9500
C7—H7	0.9500	C20—C21	1.373 (3)
C8—C9	1.377 (3)	C20—H20	0.9500
C8—H8	0.9500	C21—H21	0.9500
C10—O12	1.260 (3)
C2—O1—C9	106.52 (15)	O12—C10—O11	124.60 (19)
O1—C2—C3	110.95 (17)	O12—C10—C2	118.25 (18)
O1—C2—C10	114.61 (17)	O11—C10—C2	117.2 (2)
C3—C2—C10	134.4 (2)	O15—C13—O14	120.8 (2)
C2—C3—C4	106.52 (18)	O15—C13—C3	120.0 (2)
C2—C3—C13	129.7 (2)	O14—C13—C3	119.14 (19)
C4—C3—C13	123.74 (19)	C13—O14—H14	108.8 (14)
C9—C4—C5	118.4 (2)	C17—N16—C21	121.98 (19)
C9—C4—C3	105.78 (18)	C17—N16—H16	115.4 (12)
C5—C4—C3	135.9 (2)	C21—N16—H16	122.6 (12)
C6—C5—C4	117.9 (2)	N16—C17—C18	119.8 (2)
C6—C5—H5	121.0	N16—C17—H17	120.1
C4—C5—H5	121.0	C18—C17—H17	120.1
C5—C6—C7	121.7 (2)	C17—C18—C19	119.1 (2)
C5—C6—H6	119.1	C17—C18—H18	120.5
C7—C6—H6	119.1	C19—C18—H18	120.5
C8—C7—C6	121.4 (2)	C18—C19—C20	119.8 (2)
C8—C7—H7	119.3	C18—C19—H19	120.1
C6—C7—H7	119.3	C20—C19—H19	120.1
C9—C8—C7	115.8 (2)	C21—C20—C19	119.0 (2)
C9—C8—H8	122.1	C21—C20—H20	120.5
C7—C8—H8	122.1	C19—C20—H20	120.5
C8—C9—O1	124.91 (19)	N16—C21—C20	120.3 (2)
C8—C9—C4	124.9 (2)	N16—C21—H21	119.8
O1—C9—C4	110.22 (18)	C20—C21—H21	119.8

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O14—H14···O12	0.98 (2)	1.53 (3)	2.516 (2)	178 (2)
N16—H16···O11	1.08 (2)	1.55 (2)	2.628 (2)	179 (2)
C17—H17···O11^i	0.95	2.60	3.400 (3)	142
C18—H18···O1^ii	0.95	2.51	3.366 (3)	150
C19—H19···O14^iii	0.95	2.64	3.562 (3)	165

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

(III) Phenazinium 3-carboxylato-1-benzofuran-2-carboxylic acid

Crystal data

C12H9N2^+·C10H5O5^−	F(000) = 400
Mr = 386.35	Dx = 1.534 Mg m^−3
Monoclinic, Pn	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P -2yac	Cell parameters from 2631 reflections
a = 5.3881 (2) Å	θ = 2.3–27.8°
b = 8.3227 (4) Å	µ = 0.11 mm^−1
c = 18.6514 (11) Å	T = 110 K
β = 90.3794 (18)°	Plate, yellow
V = 836.38 (7) Å^3	0.50 × 0.40 × 0.20 mm
Z = 2

Data collection

Nonius KappaCCD area-detector diffractometer	1352 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.044
Graphite monochromator	θmax = 27.8°, θmin = 3.3°
Detector resolution: 12.8 pixels mm^-1	h = −6→7
1 deg. ϕ and ω scans	k = −10→10
7323 measured reflections	l = −21→24
1970 independent reflections

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.045	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.105	w = 1/[σ^2(Fo^2) + (0.0543P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 1.02	(Δ/σ)max = 0.002
1970 reflections	Δρmax = 0.28 e Å^−3
269 parameters	Δρmin = −0.21 e Å^−3
2 restraints	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.014 (4)

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.

The Friedel pairs were merged as suggested by Checkcif. As a result, the data-to-parameters ratio is somewhat low.

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

	x	y	z	Uiso*/Ueq
O1	−0.0823 (4)	0.0534 (3)	0.33621 (13)	0.0288 (6)
C2	0.0873 (6)	0.1450 (4)	0.37378 (18)	0.0267 (8)
C3	0.2624 (6)	0.2099 (4)	0.32969 (19)	0.0255 (8)
C4	0.2029 (6)	0.1535 (4)	0.25793 (18)	0.0244 (8)
C5	0.3084 (6)	0.1660 (4)	0.18949 (18)	0.0272 (8)
H5	0.4541	0.2280	0.1821	0.033*
C6	0.1955 (6)	0.0862 (4)	0.13342 (19)	0.0291 (8)
H6	0.2662	0.0924	0.0870	0.035*
C7	−0.0216 (6)	−0.0040 (5)	0.14333 (18)	0.0323 (9)
H7	−0.0965	−0.0555	0.1032	0.039*
C8	−0.1290 (6)	−0.0196 (5)	0.21002 (18)	0.0287 (8)
H8	−0.2757	−0.0805	0.2174	0.034*
C9	−0.0080 (6)	0.0599 (4)	0.26538 (18)	0.0258 (8)
C10	0.0409 (7)	0.1437 (5)	0.45215 (19)	0.0306 (9)
O11	0.1996 (5)	0.2263 (3)	0.49206 (14)	0.0373 (7)
H11	0.312 (8)	0.288 (6)	0.461 (2)	0.045*
O12	−0.1297 (4)	0.0690 (3)	0.47726 (13)	0.0383 (7)
C13	0.4685 (6)	0.3198 (4)	0.3483 (2)	0.0290 (8)
O14	0.5928 (4)	0.3723 (3)	0.29539 (13)	0.0324 (6)
O15	0.5115 (4)	0.3595 (3)	0.41287 (13)	0.0351 (7)
C16	0.9288 (6)	0.4975 (5)	0.16645 (19)	0.0309 (9)
H16	0.7843	0.4349	0.1746	0.037*
C17	1.0186 (7)	0.5167 (5)	0.09880 (19)	0.0330 (9)
H17	0.9324	0.4690	0.0596	0.040*
C18	1.2367 (7)	0.6057 (5)	0.0857 (2)	0.0336 (9)
H18	1.2961	0.6159	0.0380	0.040*
C19	1.3626 (6)	0.6769 (4)	0.14050 (19)	0.0301 (8)
H19	1.5097	0.7360	0.1310	0.036*
C20	1.2749 (6)	0.6632 (4)	0.21200 (19)	0.0259 (8)
N21	1.3953 (5)	0.7381 (4)	0.26556 (16)	0.0277 (7)
C22	1.3032 (6)	0.7270 (4)	0.3321 (2)	0.0274 (8)
C23	1.4220 (6)	0.8082 (5)	0.38998 (19)	0.0290 (8)
H23	1.5665	0.8707	0.3818	0.035*
C24	1.3275 (6)	0.7959 (5)	0.4571 (2)	0.0325 (9)
H24	1.4084	0.8494	0.4957	0.039*
C25	1.1094 (7)	0.7041 (5)	0.4708 (2)	0.0329 (9)
H25	1.0456	0.6993	0.5181	0.039*
C26	0.9915 (6)	0.6236 (5)	0.41720 (19)	0.0295 (8)
H26	0.8491	0.5604	0.4271	0.035*
C27	1.0827 (6)	0.6349 (4)	0.34679 (19)	0.0260 (8)
N28	0.9682 (5)	0.5593 (4)	0.29184 (15)	0.0266 (7)
H28	0.815 (7)	0.492 (5)	0.3054 (19)	0.032*
C29	1.0546 (6)	0.5726 (4)	0.22423 (19)	0.0255 (8)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0291 (12)	0.0321 (15)	0.0254 (13)	−0.0022 (11)	0.0041 (10)	0.0000 (11)
C2	0.0262 (18)	0.026 (2)	0.028 (2)	0.0021 (14)	0.0001 (15)	0.0008 (15)
C3	0.0239 (17)	0.0255 (19)	0.0271 (19)	0.0053 (14)	0.0008 (14)	0.0036 (15)
C4	0.0245 (18)	0.026 (2)	0.0225 (18)	0.0053 (14)	0.0003 (14)	−0.0010 (15)
C5	0.0232 (17)	0.029 (2)	0.029 (2)	−0.0011 (14)	0.0014 (14)	0.0032 (16)
C6	0.034 (2)	0.032 (2)	0.0211 (19)	0.0011 (16)	0.0031 (14)	−0.0004 (15)
C7	0.032 (2)	0.035 (2)	0.030 (2)	0.0029 (16)	−0.0047 (16)	−0.0034 (18)
C8	0.0268 (17)	0.032 (2)	0.027 (2)	−0.0010 (15)	0.0032 (14)	0.0003 (16)
C9	0.0242 (17)	0.026 (2)	0.0268 (19)	0.0025 (14)	0.0037 (14)	0.0007 (15)
C10	0.034 (2)	0.033 (2)	0.0241 (19)	0.0070 (16)	0.0040 (15)	−0.0006 (17)
O11	0.0417 (15)	0.0456 (18)	0.0247 (14)	−0.0023 (13)	0.0058 (11)	−0.0005 (13)
O12	0.0410 (15)	0.0430 (17)	0.0312 (15)	−0.0055 (13)	0.0117 (12)	0.0030 (12)
C13	0.0259 (18)	0.028 (2)	0.033 (2)	0.0015 (14)	−0.0008 (15)	0.0004 (16)
O14	0.0298 (13)	0.0373 (15)	0.0303 (15)	−0.0072 (11)	0.0051 (10)	0.0029 (12)
O15	0.0365 (15)	0.0419 (16)	0.0270 (15)	−0.0064 (12)	−0.0035 (11)	−0.0028 (12)
C16	0.0259 (18)	0.032 (2)	0.035 (2)	−0.0004 (15)	0.0000 (16)	−0.0002 (17)
C17	0.034 (2)	0.035 (2)	0.030 (2)	−0.0023 (17)	−0.0026 (15)	−0.0004 (17)
C18	0.035 (2)	0.038 (2)	0.028 (2)	0.0030 (17)	0.0056 (15)	0.0030 (17)
C19	0.0249 (17)	0.033 (2)	0.033 (2)	0.0018 (16)	0.0023 (15)	0.0019 (17)
C20	0.0223 (17)	0.028 (2)	0.0274 (19)	0.0010 (14)	0.0015 (14)	0.0001 (16)
N21	0.0236 (15)	0.0295 (18)	0.0299 (18)	0.0006 (13)	0.0003 (12)	0.0012 (14)
C22	0.0256 (19)	0.027 (2)	0.029 (2)	0.0002 (15)	0.0008 (15)	0.0019 (16)
C23	0.0290 (18)	0.027 (2)	0.031 (2)	−0.0001 (15)	−0.0021 (15)	0.0016 (15)
C24	0.0309 (19)	0.034 (2)	0.033 (2)	0.0043 (16)	−0.0035 (16)	−0.0017 (17)
C25	0.036 (2)	0.034 (2)	0.028 (2)	0.0055 (17)	0.0000 (16)	0.0024 (18)
C26	0.0279 (18)	0.033 (2)	0.028 (2)	0.0015 (16)	0.0015 (15)	−0.0004 (17)
C27	0.0253 (18)	0.0241 (19)	0.028 (2)	0.0027 (15)	−0.0033 (14)	0.0013 (16)
N28	0.0251 (15)	0.0259 (18)	0.0288 (18)	−0.0004 (12)	−0.0003 (13)	0.0006 (13)
C29	0.0215 (17)	0.029 (2)	0.0256 (19)	0.0025 (14)	0.0011 (14)	0.0042 (16)

Geometric parameters (Å, º)

O1—C2	1.378 (4)	C16—H16	0.9500
O1—C9	1.384 (4)	C17—C18	1.412 (5)
C2—C3	1.367 (5)	C17—H17	0.9500
C2—C10	1.484 (5)	C18—C19	1.359 (5)
C3—C4	1.452 (5)	C18—H18	0.9500
C3—C13	1.478 (5)	C19—C20	1.422 (5)
C4—C9	1.385 (5)	C19—H19	0.9500
C4—C5	1.405 (5)	C20—N21	1.341 (4)
C5—C6	1.377 (5)	C20—C29	1.426 (5)
C5—H5	0.9500	N21—C22	1.343 (4)
C6—C7	1.403 (5)	C22—C23	1.422 (5)
C6—H6	0.9500	C22—C27	1.442 (5)
C7—C8	1.381 (5)	C23—C24	1.359 (5)
C7—H7	0.9500	C23—H23	0.9500
C8—C9	1.385 (5)	C24—C25	1.426 (6)
C8—H8	0.9500	C24—H24	0.9500
C10—O12	1.207 (4)	C25—C26	1.357 (5)
C10—O11	1.323 (4)	C25—H25	0.9500
O11—H11	0.99 (5)	C26—C27	1.408 (5)
C13—O15	1.269 (4)	C26—H26	0.9500
C13—O14	1.273 (4)	C27—N28	1.349 (4)
C16—C17	1.364 (5)	N28—C29	1.351 (4)
C16—C29	1.415 (5)	N28—H28	1.03 (4)
C2—O1—C9	105.6 (3)	C16—C17—H17	119.2
C3—C2—O1	111.8 (3)	C18—C17—H17	119.2
C3—C2—C10	135.8 (3)	C19—C18—C17	120.7 (3)
O1—C2—C10	112.4 (3)	C19—C18—H18	119.7
C2—C3—C4	106.1 (3)	C17—C18—H18	119.7
C2—C3—C13	128.6 (3)	C18—C19—C20	120.2 (3)
C4—C3—C13	125.2 (3)	C18—C19—H19	119.9
C9—C4—C5	118.0 (3)	C20—C19—H19	119.9
C9—C4—C3	105.4 (3)	N21—C20—C19	119.9 (3)
C5—C4—C3	136.5 (3)	N21—C20—C29	121.7 (3)
C6—C5—C4	118.3 (3)	C19—C20—C29	118.3 (3)
C6—C5—H5	120.8	C22—N21—C20	118.5 (3)
C4—C5—H5	120.8	N21—C22—C23	120.1 (3)
C5—C6—C7	121.5 (3)	N21—C22—C27	121.5 (3)
C5—C6—H6	119.2	C23—C22—C27	118.4 (3)
C7—C6—H6	119.2	C24—C23—C22	119.6 (3)
C8—C7—C6	121.6 (3)	C24—C23—H23	120.2
C8—C7—H7	119.2	C22—C23—H23	120.2
C6—C7—H7	119.2	C23—C24—C25	121.3 (4)
C7—C8—C9	115.4 (3)	C23—C24—H24	119.4
C7—C8—H8	122.3	C25—C24—H24	119.4
C9—C8—H8	122.3	C26—C25—C24	121.0 (4)
O1—C9—C8	123.7 (3)	C26—C25—H25	119.5
O1—C9—C4	111.1 (3)	C24—C25—H25	119.5
C8—C9—C4	125.2 (3)	C25—C26—C27	119.3 (3)
O12—C10—O11	122.7 (3)	C25—C26—H26	120.3
O12—C10—C2	121.3 (3)	C27—C26—H26	120.3
O11—C10—C2	116.0 (3)	N28—C27—C26	121.1 (3)
C10—O11—H11	110 (2)	N28—C27—C22	118.5 (3)
O15—C13—O14	123.6 (3)	C26—C27—C22	120.4 (3)
O15—C13—C3	121.0 (3)	C27—N28—C29	120.8 (3)
O14—C13—C3	115.4 (3)	C27—N28—H28	115 (2)
C17—C16—C29	118.8 (3)	C29—N28—H28	124 (2)
C17—C16—H16	120.6	N28—C29—C16	120.5 (3)
C29—C16—H16	120.6	N28—C29—C20	119.0 (3)
C16—C17—C18	121.5 (3)	C16—C29—C20	120.5 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O11—H11···O15	0.99 (5)	1.52 (5)	2.503 (3)	171 (4)
N28—H28···O14	1.03 (4)	1.57 (4)	2.553 (4)	158 (3)
C6—H6···O12^i	0.95	2.51	3.328 (4)	144
C8—H8···N21^ii	0.95	2.50	3.427 (4)	165
C26—H26···O15	0.95	2.48	3.395 (4)	161

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

(IV) 4-Aminoanilinium 2-carboxylato-1-benzofuran-3-carboxylic acid

Crystal data

C6H9N2^+·C10H5O5^−	F(000) = 328
Mr = 314.29	Dx = 1.472 Mg m^−3
Monoclinic, P21	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2yb	Cell parameters from 1601 reflections
a = 5.8427 (2) Å	θ = 2.3–27.8°
b = 17.5893 (7) Å	µ = 0.11 mm^−1
c = 7.1302 (3) Å	T = 110 K
β = 104.6337 (16)°	Plate, colourless
V = 708.99 (5) Å^3	0.50 × 0.50 × 0.10 mm
Z = 2

Data collection

Nonius KappaCCD area-detector diffractometer	1422 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.036
Graphite monochromator	θmax = 27.8°, θmin = 2.3°
Detector resolution: 12.8 pixels mm^-1	h = −7→7
1 deg. ϕ and ω scans	k = −20→22
5908 measured reflections	l = −9→9
1729 independent reflections

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.042	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.110	w = 1/[σ^2(Fo^2) + (0.0777P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 1.02	(Δ/σ)max < 0.001
1729 reflections	Δρmax = 0.27 e Å^−3
227 parameters	Δρmin = −0.22 e Å^−3
1 restraint	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.046 (10)

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.

Friedel pairs were merged as suggested by Checkcif. This results in a somewhat low data-to-parameters ratio.

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

	x	y	z	Uiso*/Ueq
O1	−0.1944 (3)	0.32257 (12)	1.0762 (3)	0.0291 (5)
C2	−0.0264 (5)	0.28504 (19)	1.0082 (4)	0.0277 (6)
C3	0.0331 (4)	0.21694 (18)	1.1014 (4)	0.0268 (6)
C4	−0.1035 (5)	0.21197 (18)	1.2452 (4)	0.0291 (6)
C5	−0.1210 (5)	0.16029 (18)	1.3889 (4)	0.0326 (7)
H5	−0.0289	0.1151	1.4099	0.039*
C6	−0.2773 (5)	0.1771 (2)	1.5001 (4)	0.0372 (7)
H6	−0.2906	0.1427	1.5996	0.045*
C7	−0.4161 (6)	0.2427 (2)	1.4713 (5)	0.0364 (7)
H7	−0.5229	0.2517	1.5495	0.044*
C8	−0.3994 (5)	0.29529 (19)	1.3283 (4)	0.0320 (7)
H8	−0.4924	0.3403	1.3057	0.038*
C9	−0.2383 (5)	0.27746 (18)	1.2220 (4)	0.0279 (6)
C10	0.0579 (5)	0.32876 (17)	0.8592 (4)	0.0273 (6)
O11	0.2357 (3)	0.29930 (13)	0.8088 (3)	0.0337 (5)
O12	−0.0338 (3)	0.38930 (13)	0.8012 (3)	0.0324 (5)
C13	0.1937 (5)	0.15629 (18)	1.0649 (4)	0.0292 (6)
O14	0.3351 (3)	0.17217 (13)	0.9513 (3)	0.0327 (5)
H14	0.295 (6)	0.217 (3)	0.870 (6)	0.049*
O15	0.1950 (3)	0.09354 (12)	1.1364 (3)	0.0336 (5)
N16	0.4894 (4)	0.42962 (15)	0.7505 (4)	0.0264 (5)
H16A	0.393 (6)	0.387 (2)	0.745 (5)	0.040*
H16B	0.645 (7)	0.424 (2)	0.804 (5)	0.040*
H16C	0.438 (6)	0.470 (2)	0.839 (5)	0.040*
C17	0.4405 (5)	0.45689 (17)	0.5500 (4)	0.0245 (6)
C18	0.2187 (5)	0.44712 (17)	0.4257 (4)	0.0261 (6)
H18	0.0972	0.4223	0.4692	0.031*
C19	0.1752 (5)	0.47390 (17)	0.2364 (4)	0.0265 (6)
H19	0.0234	0.4674	0.1501	0.032*
C20	0.3550 (5)	0.51046 (16)	0.1732 (4)	0.0241 (6)
N23	0.3133 (4)	0.53619 (15)	−0.0210 (3)	0.0270 (5)
H23A	0.401 (6)	0.573 (3)	−0.024 (5)	0.041*
H23B	0.155 (6)	0.544 (2)	−0.074 (5)	0.041*
C21	0.5767 (5)	0.51948 (17)	0.2998 (4)	0.0266 (6)
H21	0.6989	0.5442	0.2568	0.032*
C22	0.6210 (4)	0.49279 (17)	0.4883 (4)	0.0257 (6)
H22	0.7730	0.4989	0.5746	0.031*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0278 (10)	0.0289 (11)	0.0332 (11)	0.0025 (9)	0.0128 (8)	0.0015 (9)
C2	0.0218 (12)	0.0313 (16)	0.0313 (14)	0.0005 (11)	0.0088 (10)	−0.0041 (12)
C3	0.0222 (12)	0.0308 (16)	0.0276 (13)	−0.0045 (11)	0.0064 (9)	−0.0044 (12)
C4	0.0271 (13)	0.0303 (16)	0.0305 (15)	−0.0039 (12)	0.0083 (10)	−0.0048 (13)
C5	0.0351 (15)	0.0275 (16)	0.0353 (15)	−0.0010 (12)	0.0088 (11)	−0.0011 (13)
C6	0.0452 (17)	0.0362 (18)	0.0333 (16)	−0.0100 (14)	0.0154 (13)	−0.0005 (14)
C7	0.0379 (16)	0.0417 (19)	0.0339 (16)	−0.0059 (14)	0.0170 (12)	−0.0065 (14)
C8	0.0320 (13)	0.0287 (16)	0.0374 (16)	−0.0020 (12)	0.0129 (11)	−0.0082 (13)
C9	0.0284 (13)	0.0294 (16)	0.0269 (14)	−0.0055 (11)	0.0086 (10)	−0.0029 (12)
C10	0.0239 (13)	0.0309 (16)	0.0275 (14)	−0.0044 (11)	0.0072 (10)	−0.0032 (12)
O11	0.0282 (10)	0.0338 (13)	0.0430 (12)	0.0011 (9)	0.0164 (8)	0.0016 (10)
O12	0.0282 (10)	0.0348 (13)	0.0350 (11)	0.0012 (9)	0.0095 (8)	0.0018 (9)
C13	0.0231 (13)	0.0324 (17)	0.0299 (14)	−0.0036 (11)	0.0030 (10)	−0.0023 (13)
O14	0.0312 (11)	0.0296 (12)	0.0409 (12)	0.0038 (9)	0.0159 (9)	0.0013 (10)
O15	0.0308 (10)	0.0275 (12)	0.0415 (12)	0.0039 (9)	0.0072 (8)	0.0035 (10)
N16	0.0244 (12)	0.0299 (14)	0.0256 (13)	−0.0001 (10)	0.0075 (9)	0.0022 (11)
C17	0.0255 (13)	0.0248 (14)	0.0240 (14)	0.0038 (11)	0.0080 (10)	−0.0004 (11)
C18	0.0227 (12)	0.0282 (16)	0.0291 (15)	−0.0013 (11)	0.0100 (10)	−0.0003 (12)
C19	0.0206 (12)	0.0317 (17)	0.0280 (14)	0.0007 (11)	0.0074 (10)	−0.0021 (12)
C20	0.0247 (13)	0.0220 (14)	0.0274 (14)	0.0022 (10)	0.0100 (10)	−0.0012 (11)
N23	0.0256 (11)	0.0291 (13)	0.0261 (12)	−0.0006 (10)	0.0061 (9)	0.0021 (10)
C21	0.0253 (13)	0.0253 (15)	0.0299 (14)	−0.0005 (11)	0.0084 (10)	0.0004 (12)
C22	0.0232 (12)	0.0265 (15)	0.0265 (14)	−0.0013 (11)	0.0046 (10)	−0.0025 (11)

Geometric parameters (Å, º)

O1—C2	1.370 (3)	C13—O14	1.325 (4)
O1—C9	1.382 (4)	O14—H14	0.97 (5)
C2—C3	1.371 (5)	N16—C17	1.466 (4)
C2—C10	1.492 (4)	N16—H16A	0.93 (4)
C3—C4	1.452 (4)	N16—H16B	0.90 (4)
C3—C13	1.487 (4)	N16—H16C	1.05 (4)
C4—C9	1.382 (4)	C17—C18	1.383 (4)
C4—C5	1.393 (4)	C17—C22	1.393 (4)
C5—C6	1.384 (4)	C18—C19	1.391 (4)
C5—H5	0.9500	C18—H18	0.9500
C6—C7	1.395 (5)	C19—C20	1.400 (4)
C6—H6	0.9500	C19—H19	0.9500
C7—C8	1.398 (5)	C20—C21	1.388 (4)
C7—H7	0.9500	C20—N23	1.418 (4)
C8—C9	1.386 (4)	N23—H23A	0.83 (4)
C8—H8	0.9500	N23—H23B	0.92 (4)
C10—O12	1.216 (4)	C21—C22	1.385 (4)
C10—O11	1.290 (3)	C21—H21	0.9500
C13—O15	1.215 (4)	C22—H22	0.9500
C2—O1—C9	106.0 (2)	O14—C13—C3	118.3 (3)
O1—C2—C3	111.5 (3)	C13—O14—H14	116 (2)
O1—C2—C10	113.5 (3)	C17—N16—H16A	105 (2)
C3—C2—C10	134.9 (3)	C17—N16—H16B	112 (2)
C2—C3—C4	106.1 (3)	H16A—N16—H16B	117 (4)
C2—C3—C13	129.5 (3)	C17—N16—H16C	110 (2)
C4—C3—C13	124.3 (3)	H16A—N16—H16C	108 (3)
C9—C4—C5	119.1 (3)	H16B—N16—H16C	104 (3)
C9—C4—C3	105.3 (3)	C18—C17—C22	121.0 (3)
C5—C4—C3	135.6 (3)	C18—C17—N16	120.3 (2)
C6—C5—C4	117.6 (3)	C22—C17—N16	118.7 (2)
C6—C5—H5	121.2	C17—C18—C19	119.5 (2)
C4—C5—H5	121.2	C17—C18—H18	120.3
C5—C6—C7	122.4 (3)	C19—C18—H18	120.3
C5—C6—H6	118.8	C18—C19—C20	120.0 (3)
C7—C6—H6	118.8	C18—C19—H19	120.0
C6—C7—C8	120.7 (3)	C20—C19—H19	120.0
C6—C7—H7	119.7	C21—C20—C19	119.7 (3)
C8—C7—H7	119.7	C21—C20—N23	120.0 (2)
C9—C8—C7	115.5 (3)	C19—C20—N23	120.2 (2)
C9—C8—H8	122.2	C20—N23—H23A	109 (3)
C7—C8—H8	122.2	C20—N23—H23B	111 (2)
C4—C9—O1	111.1 (2)	H23A—N23—H23B	115 (3)
C4—C9—C8	124.7 (3)	C22—C21—C20	120.5 (3)
O1—C9—C8	124.2 (3)	C22—C21—H21	119.8
O12—C10—O11	125.0 (3)	C20—C21—H21	119.8
O12—C10—C2	119.8 (2)	C21—C22—C17	119.3 (2)
O11—C10—C2	115.1 (3)	C21—C22—H22	120.4
O15—C13—O14	120.6 (3)	C17—C22—H22	120.4
O15—C13—C3	121.0 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O14—H14···O11	0.97 (5)	1.53 (5)	2.464 (3)	160 (4)
N16—H16A···O11	0.93 (4)	1.91 (4)	2.817 (3)	164 (3)
N16—H16B···O12^i	0.90 (4)	1.98 (4)	2.808 (3)	153 (3)
N16—H16C···N23^ii	1.05 (4)	1.80 (4)	2.842 (4)	173 (3)
N23—H23A···O14^iii	0.83 (4)	2.30 (4)	3.110 (3)	166 (3)
N23—H23B···O15^iv	0.92 (4)	2.16 (4)	3.047 (3)	162 (3)

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