4-Amino­pyridinium 4-amino­benzoate di­hydrate and 4-amino­pyridinium nicotinate

In the title compounds, 4-amino­pyridinium 4-amino­benzoate dihydrate, C₇H₆NO₂^-·C₅H₇N₂⁺·2H₂O, (I), and 4-amino­pyridinium nicotinate, C₅H₇N₂⁺·C₆H₄NO₂^-, (II), the aromatic N atoms of the 4-amino­pyridinium cations are protonated. In (I), the asymmetric unit is composed of two 4-amino­pyridinium cations, two 4-amino­benzoate anions and four water mol­ecules, and the compound crystallizes in a noncentrosymmetric space group. The two sets of independent mol­ecules of (I) are related by a centre of symmetry which is not part of the space group. In (I), the protonated pyridinium ring H atoms are involved in bifurcated hydrogen bonding with carboxyl­ate O atoms to form an R₁²(4) ring motif. The water mol­ecules link the ions to form a two-dimensional network along the (10) plane. In (II), an intra­molecular bifurcated hydrogen bond generates an R₁²(4) ring motif and inter-ion hydrogen bonding generates an R₄²(16) ring motif. The packing of adduct (II) is consolidated via N-H...O and N-H...N hydrogen bonds to form a two-dimensional network along the (10) plane.

S1. Comment

4-aminopyridine (fampridine) is used clinically in Lambert-Eaton myasthenic syndrome and multiple sclerosis because by blocking potassium channels it prolongs action potentials, thereby increasing transmitter release at the neuromuscular junction (Judge & Bever, 2006; Schwid et al., 1997; Strupp et al., 2004). The structure of 4-aminopyridine was first reported by Chao & Schempp (1977) and a redetermination was reported by Anderson et al. (2005). 4-Aminobenzoic acid acts as a bacterial cofactor involved in the biosynthesis of folic acid, which is a constituent of the vitamin B complex and is found in animal and plant tissues (Robinson, 1966; Zoroddu et al., 1996). Two different polymorphs of 4-aminobenzoic acid have been re-investigated recently, the α-form (Athimoolam & Natarajan, 2007) and the β-form (Gracin & Fischer, 2005). We have already reported the crystal structure of the salt of 4-aminobenzoic acid-nicotinic acid (Jebas & Balasubramanian, 2006). Nicotinic acid (vitamin B3) is a 3-pyridine carboxylic acid, known as niacin. It is a lipid-lowering agent widely used to treat hypertriglyceridemia by the inhibition of lipolysis in adipose tissues (Athimoolam & Rajaram, 2005). The crystal structure of nicotinic acid was first determined by photographic methods (Wright & King, 1953), and a redetermination was reported by Kutoglu & Scheringer (1983). The crystal structures of isonicotinic acid (Takusagawa & Shimada, 1976), 2-aminonicotinic acid (Dobson & Gerkin, 1997), 6-aminonicotinic acid hydrochloride (Giantsidis & Turnbull, 2000) and 2-(methylsulfanyl)nicotinic acid (Basavoju et al., 2005) have been reported. The nicotinic acid complex 5-methylpyrazine-2-carboxylic acid 4-oxide is a commonly used drug for the treatment of hypercholesterolemia (Lorenzen et al., 2001). Coordination complexes of nicotinic acid with metals such as Sn possess antitumour activity greater than that of the well known cis-platin or doxorubicin (Gielen et al., 1992). The enzyme nicotinic acid mononucleotide adenyltransferase is essential for the synthesis of nicotinamide adenine dinucleotide in all living cells and is a potential target for antibiotics (Kim et al., 2004). As an extension of our systematic study of hydrogen-bonding patterns of 4-aminopyridine with carboxylic acids, the title compounds, (I) and (II), have been synthesized and their crystal structures are presented here.

The asymmetric unit of (I) (Fig. 1), consists of two 4-aminopyridinium cations protonated at atoms N4B and N4D, two 4-aminobenzoate anions with the carboxyl groups deprotonated, and four water molecules, while that of (II) contains one 4-aminopyridinium cation protonated at atom N1 and one nicotinic acetate anion with the carboxylate group deprotonated (Fig. 2). Compound (I) crystallizes in a noncentrosymmetric space group. The bond lengths and angles of the protonated 4-aminopyridinium in (I) and (II) are comparable with the values reported earlier for 4-aminopyridine in its protonated form (Fun et al., 2009a,b). There is a significant decrease in the length of the C1B—N7B bond, which is 1.315 (4) Å in (I) compared with 1.3597 (18) Å in the neutral 4-aminopyridine molecule (Anderson et al., 2005). The bond lengths and angles in 4-aminobenzoic acid and nicotinic acid are comparable with the values reported earlier (Gracin & Fischer, 2005; Jebas et al., 2006; Kutoglu & Scheringer, 1983; Jebas & Balasubramanian, 2006). As expected, all the aromatic rings in the asymmetric units of (I) and (II) are essentially planar, with the maximum deviations of the ring atoms from the least-squares plane being 0.018 (4) Å for atom C6A and 0.006 (4) Å for atom C3C in 4-aminobenzoate, and 0.010 (5) Å for atom C3B and 0.011 (4) Å for atoms C1D and C6D in 4-aminopyridine. In (II), the mean-plane deviation is 0.005 (3) Å for atom C2 and −0.008 Å for atom C8. 4-Aminopyridine is protonated in molecules (I) and (II) to form a salt, with the H atom from the carboxyl group of 4-aminobenzoic acid in (I) transferred to atoms N4B and N4D of the 4-aminopyridine in (I), and the H atom from the carboxyl group of nicotinic acid transferred to atom N1 of the 4-aminopyridine in (II). The protonation is evidenced by the widening of the internal angles (C3B—N4B—C5B and C3D—N4D—C5D) of the pyridine rings to 120.5 (4)° in molecule B and 120.4 (3)° in molecule D of (I), and of the C2—N1—C6 angle to 120.51° in molecule (II), compared with 115.25 (13)° in unprotonated 4-aminopyridine (Anderson et al., 2005; Chao & Schempp, 1977). Similar protonation is observed in various 4-aminopyridine–acid complexes, such as 4-aminopyridinium hydrogen succinate (Fun et al., 2009a) and bis(4-aminopyridinium)bis(hydrogen oxalate)monohydrate (Fun et al., 2009b).

In (I), the dihedral angles formed by the carboxylate groups (O8A—C7A—O9A—C4A and O8C—C7C—O9C—C4C) of the aminobenzoate anions with the attached benzene rings (C1A–C6A and C1C–C6C) are 8.21 (18) and 5.92 (18)°, respectively, indicating that they are twisted from the mean planes of the benzene rings. The two pyridinium rings (C1B–C3B/N4B/C5B/C6B and C1D–C3D/N4D/C5D/C6D) in (I) are twisted from away each other, forming a dihedral angle of 55.10 (17)°, and the two 4-aminobenzoate anions are twisted away from each other with a dihedral angle of 47.78 (18)°. Pyramidalization can be observed in the sums of the three angles at N of 356.78° in molecule B and 359.97° in molecule D of (I), and 358.62° in (II). The nicotinate and 4-aminopyridinium cations are oriented at an angle of 9.04 (7)° in (II).

The hydrogen-bonding pattern of (I) is shown in Fig. 3. Twenty intermolecular hydrogen bonds are observed in the structure of (I). The carboxylate O atoms of the 4-aminobenzoate anion act as acceptors of bifurcated N—H···O hydrogen bonds with the protonated 4-aminopyridinium cation (Table 2), forming a ring with the graph-set notation R₁²(4) (Bernstein et al., 1995). In addition to the bifurcated hydrogen bonding linking the cation with the anion, the water O atoms play a crucial role in linking the cations with the anions. In the crystal packing of (I) (Fig. 3), the molecules are linked by N—H···O and O—H···O hydrogen bonds to form a two-dimensional network along the (101) plane. In (II), the carboxylate O atoms of the nicotinate anion act as acceptors of bifurcated N—H···O hydrogen bonds with the protonated 4-aminopyridinium cation (Table 4), forming a ring with the graph-set notation R₁²(4). The amino H atoms are involved in forming N—H···N and N—H···O hydrogen bonds with the inversion-related molecules to complete a loop of graph-set motif R₄⁴(16) (Fig. 4). The packing of adduct (II) is consolidated via N—H···O and N—H···N hydrogen bonds to form a two-dimensional network along the (102) plane.

S2. Experimental

Compound (I) was prepared by dissolving 4-aminopyridine (0.094 g, 1 mmol) in water (10 ml) and 4-aminobenzoic acid (0.169 g, 1 mmol) in ethanol (10 ml). [The solutions were mixed and the mixture] was stirred well for 3 h. Colourless crystals of (I) were obtained by slow evaporation of the solution over a period of one month. Compound (II) was prepared by dissolving 4-aminopyridine (0.094 g, 1 mmol) in ethanol and nicotinic acid (0.123 g, 1 mmol) in water. The nicotinic acid solution was added dropwise to the 4-aminopyridine. The clear solution obtained was allowed to evaporate slowly. Colourless crystals of (II) suitable for X-ray diffraction were obtained after two weeks.

S3. Refinement

In (I) and (II), H atoms bonded to C and N atoms were positioned geometrically and treated as riding, with C—H = 0.95 Å and N—H = 0.88 Å, and with U_iso(H) = 1.2U_eq(C,N). H atoms bonded to water O atoms were located in a difference Fourier map and constraints were applied to refine them with U_iso(H) = 1.5U_eq(O). The number of Friedel pairs is 2236 in molecule (I).

Computing details

For both compounds, data collection: CAD-4 EXPRESS (Enraf–Nonius, 1994); cell refinement: CAD-4 EXPRESS (Enraf–Nonius, 1994); data reduction: CORINC (Draeger & Gattow, 1971); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).

Figures

	Fig. 1. The asymmetric unit of (I), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii.
	Fig. 2. The asymmetric unit of (II), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii. Bifurcated intramolecular hydrogen bonding with a ring of motif R1^2(4) is shown as dashed lines.
	Fig. 3. A view of the two-dimensional hydrogen-bonded network of (I), showing the aggregation of the R1^2(4) hydrogen-bonding motif. Hydrogen bonds are shown as dashed lines. [Symmetry codes: (i) x, 1 − y, −1/2 + z; (ii) −1/2 + x, −1/2 + y, z; (iii) 1/2 + x, −1/2 + y, z.]
	Fig. 4. A two-dimensional hydrogen-bonded view of (II), showing the R1^2(4) and R4^4(18) ring motifs. Hydrogen bonds are shown as dashed lines. [Symmetry codes: (i) 1 − x, 1/2 + y, 1/2 − z; (ii) 1 − x, −1/2 + y, 1/2 − z; (iii) −1 + x, 1/2 − y, −1/2 + z.]

(I) 4-aminopyridinium 4-aminobenzoate dihydrate

Crystal data

C5H7N2^+·C7H6NO2^−·2H2O	F(000) = 1136
Mr = 267.29	Dx = 1.321 Mg m^−3
Monoclinic, Cc	Cu Kα radiation, λ = 1.54178 Å
Hall symbol: C -2yc	Cell parameters from 25 reflections
a = 18.9692 (18) Å	θ = 60–69°
b = 7.8092 (4) Å	µ = 0.84 mm^−1
c = 19.5944 (19) Å	T = 193 K
β = 112.213 (4)°	Block, colourless
V = 2687.2 (4) Å^3	0.38 × 0.32 × 0.16 mm
Z = 8

Data collection

Enraf–Nonius CAD-4 diffractometer	2334 reflections with I > 2σ(I)
Radiation source: rotating anode	Rint = 0.045
Graphite monochromator	θmax = 70.0°, θmin = 4.9°
ω/2θ scans	h = −22→22
Absorption correction: ψ scan (CORINC; Draeger & Gattow, 1971)	k = 0→9
Tmin = 0.741, Tmax = 0.877	l = −23→23
4793 measured reflections	3 standard reflections every 60 min
2557 independent reflections	intensity decay: 2%

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)] = 0.055	H-atom parameters constrained
wR(F^2) = 0.156	w = 1/[σ^2(Fo^2) + (0.1162P)^2 + 0.3843P] where P = (Fo^2 + 2Fc^2)/3
S = 1.05	(Δ/σ)max < 0.002
2557 reflections	Δρmax = 0.28 e Å^−3
344 parameters	Δρmin = −0.37 e Å^−3
14 restraints	Absolute structure: Flack (1983), with 2236 Friedel pairs
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.2 (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
C1A	0.4483 (2)	0.0745 (5)	0.3941 (2)	0.0428 (8)
C2A	0.47909 (18)	0.0212 (5)	0.46685 (19)	0.0420 (8)
H2A	0.5292	−0.0244	0.4864	0.050*
C3A	0.43750 (19)	0.0338 (5)	0.51106 (19)	0.0412 (8)
H3A	0.4592	−0.0031	0.5609	0.049*
C4A	0.36214 (16)	0.1017 (4)	0.48236 (17)	0.0361 (7)
C5A	0.33385 (17)	0.1549 (5)	0.41012 (18)	0.0367 (7)
H5A	0.2834	0.1988	0.3900	0.044*
C6A	0.37500 (18)	0.1474 (5)	0.36545 (19)	0.0412 (8)
H6A	0.3544	0.1904	0.3165	0.049*
C7A	0.3182 (2)	0.1135 (4)	0.53087 (19)	0.0431 (7)
O8A	0.24875 (15)	0.1565 (3)	0.50276 (15)	0.0504 (6)
O9A	0.34981 (17)	0.0812 (3)	0.59912 (14)	0.0522 (7)
N10A	0.49082 (19)	0.0594 (6)	0.35071 (19)	0.0632 (11)
H10A	0.5371	0.0162	0.3693	0.076*
H10B	0.4717	0.0931	0.3044	0.076*
C1B	0.12976 (19)	0.8248 (4)	0.21892 (18)	0.0370 (7)
C2B	0.20204 (19)	0.9014 (5)	0.2432 (2)	0.0454 (9)
H2B	0.2238	0.9434	0.2922	0.054*
C3B	0.2416 (2)	0.9171 (6)	0.1987 (3)	0.0602 (12)
H3B	0.2897	0.9729	0.2160	0.072*
N4B	0.2116 (2)	0.8516 (4)	0.1285 (2)	0.0596 (9)
H4B	0.2376	0.8594	0.0997	0.072*
C5B	0.1452 (3)	0.7783 (5)	0.1042 (2)	0.0543 (10)
H5B	0.1260	0.7341	0.0554	0.065*
C6B	0.1025 (2)	0.7621 (5)	0.14495 (19)	0.0478 (9)
H6B	0.0540	0.7088	0.1246	0.057*
N7B	0.09003 (17)	0.8107 (4)	0.26088 (18)	0.0470 (7)
H7B	0.1085	0.8502	0.3063	0.056*
H7C	0.0449	0.7618	0.2436	0.056*
C1C	0.12642 (19)	0.3243 (4)	0.22138 (18)	0.0375 (7)
C2C	0.0975 (2)	0.2690 (5)	0.14609 (19)	0.0465 (9)
H2C	0.0479	0.2209	0.1251	0.056*
C3C	0.1404 (2)	0.2846 (5)	0.10423 (19)	0.0444 (9)
H3C	0.1191	0.2490	0.0542	0.053*
C4C	0.21200 (19)	0.3486 (4)	0.13078 (17)	0.0376 (7)
C5C	0.24278 (19)	0.4046 (5)	0.20511 (18)	0.0419 (8)
H5C	0.2927	0.4514	0.2251	0.050*
C6C	0.20032 (17)	0.3911 (5)	0.24801 (18)	0.0388 (8)
H6C	0.2219	0.4286	0.2978	0.047*
C7C	0.2584 (2)	0.3631 (4)	0.08407 (18)	0.0420 (6)
O8C	0.22755 (17)	0.3273 (3)	0.01618 (14)	0.0514 (7)
O9C	0.32715 (16)	0.4120 (3)	0.11228 (15)	0.0510 (6)
N10C	0.08559 (19)	0.3106 (5)	0.26362 (19)	0.0544 (9)
H10C	0.1050	0.3442	0.3099	0.065*
H10D	0.0392	0.2680	0.2452	0.065*
C1D	0.44629 (19)	0.5743 (5)	0.39756 (18)	0.0398 (8)
C2D	0.4741 (2)	0.5146 (5)	0.4696 (2)	0.0464 (9)
H2D	0.5230	0.4630	0.4898	0.056*
C3D	0.4310 (3)	0.5302 (6)	0.5113 (2)	0.0566 (11)
H3D	0.4496	0.4889	0.5606	0.068*
N4D	0.35979 (19)	0.6066 (5)	0.4815 (2)	0.0596 (9)
H4D	0.3317	0.6161	0.5083	0.072*
C5D	0.3342 (2)	0.6645 (5)	0.4139 (3)	0.0524 (10)
H5D	0.2851	0.7157	0.3952	0.063*
C6D	0.37390 (19)	0.6554 (5)	0.3690 (2)	0.0447 (8)
H6D	0.3541	0.7015	0.3206	0.054*
N7D	0.48796 (18)	0.5564 (5)	0.35534 (18)	0.0532 (8)
H7D	0.5329	0.5067	0.3735	0.064*
H7E	0.4702	0.5944	0.3097	0.064*
O1W	0.41925 (15)	0.6648 (4)	0.20049 (14)	0.0551 (8)
H1W	0.4027	0.7709	0.1742	0.083*
H2W	0.3819	0.5799	0.1750	0.083*
O2W	0.14559 (17)	0.9180 (4)	0.41753 (14)	0.0556 (7)
H3W	0.1832	1.0052	0.4424	0.083*
H4W	0.1605	0.8195	0.4502	0.083*
O3W	0.15272 (18)	0.4099 (4)	0.42329 (16)	0.0664 (9)
H5W	0.1731	0.5028	0.4574	0.100*
H6W	0.1831	0.3106	0.4442	0.100*
O4W	0.43348 (15)	0.1709 (4)	0.19169 (14)	0.0517 (7)
H7W	0.4061	0.2770	0.1736	0.078*
H8W	0.4037	0.0835	0.1587	0.078*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1A	0.0345 (17)	0.052 (2)	0.0415 (19)	−0.0015 (15)	0.0142 (14)	−0.0063 (16)
C2A	0.0282 (15)	0.0472 (18)	0.0452 (19)	0.0069 (13)	0.0080 (14)	−0.0021 (15)
C3A	0.0316 (16)	0.0497 (19)	0.0330 (16)	0.0020 (12)	0.0014 (13)	−0.0036 (14)
C4A	0.0236 (14)	0.0436 (17)	0.0336 (15)	0.0008 (12)	0.0023 (11)	−0.0064 (13)
C5A	0.0282 (16)	0.0391 (17)	0.0378 (16)	0.0002 (12)	0.0069 (12)	−0.0013 (13)
C6A	0.0356 (17)	0.049 (2)	0.0324 (16)	−0.0028 (13)	0.0058 (13)	0.0022 (14)
C7A	0.0469 (17)	0.0398 (15)	0.0404 (16)	−0.0023 (12)	0.0141 (13)	−0.0047 (11)
O8A	0.0442 (14)	0.0561 (14)	0.0487 (14)	0.0052 (10)	0.0149 (10)	−0.0009 (10)
O9A	0.0579 (16)	0.0574 (13)	0.0348 (12)	0.0053 (11)	0.0102 (10)	−0.0004 (9)
N10A	0.0445 (18)	0.101 (3)	0.0486 (18)	0.0131 (18)	0.0225 (15)	0.0039 (19)
C1B	0.0333 (16)	0.0335 (15)	0.0361 (17)	0.0024 (13)	0.0039 (13)	0.0000 (14)
C2B	0.0341 (18)	0.049 (2)	0.0421 (19)	−0.0025 (14)	0.0018 (15)	0.0001 (15)
C3B	0.041 (2)	0.056 (2)	0.078 (3)	−0.0020 (17)	0.0157 (19)	0.012 (2)
N4B	0.081 (3)	0.0481 (18)	0.064 (2)	0.0145 (18)	0.0434 (18)	0.0118 (16)
C5B	0.068 (3)	0.055 (2)	0.042 (2)	0.0009 (18)	0.0221 (19)	−0.0066 (17)
C6B	0.046 (2)	0.052 (2)	0.0365 (19)	−0.0047 (15)	0.0060 (15)	−0.0080 (15)
N7B	0.0402 (15)	0.0585 (19)	0.0409 (16)	−0.0105 (13)	0.0136 (13)	−0.0083 (14)
C1C	0.0352 (17)	0.0345 (15)	0.0348 (17)	0.0011 (13)	0.0040 (12)	−0.0005 (14)
C2C	0.0361 (17)	0.057 (2)	0.0355 (18)	−0.0100 (15)	0.0010 (14)	−0.0093 (15)
C3C	0.0426 (19)	0.053 (2)	0.0296 (16)	−0.0058 (14)	0.0040 (14)	−0.0110 (14)
C4C	0.0460 (19)	0.0314 (15)	0.0299 (15)	0.0051 (13)	0.0082 (13)	0.0011 (12)
C5C	0.0328 (17)	0.050 (2)	0.0307 (15)	−0.0029 (14)	−0.0016 (12)	0.0024 (14)
C6C	0.0341 (18)	0.0448 (18)	0.0279 (15)	−0.0039 (13)	0.0008 (13)	−0.0012 (13)
C7C	0.0444 (15)	0.0404 (14)	0.0368 (15)	0.0009 (11)	0.0105 (12)	0.0046 (11)
O8C	0.0610 (16)	0.0537 (13)	0.0355 (11)	−0.0012 (11)	0.0138 (10)	−0.0015 (9)
O9C	0.0448 (13)	0.0596 (14)	0.0463 (13)	−0.0057 (10)	0.0147 (10)	−0.0029 (10)
N10C	0.0454 (18)	0.075 (2)	0.0430 (17)	−0.0171 (16)	0.0166 (14)	−0.0126 (16)
C1D	0.0331 (16)	0.052 (2)	0.0349 (17)	−0.0042 (14)	0.0131 (13)	−0.0030 (15)
C2D	0.0453 (19)	0.0461 (18)	0.044 (2)	0.0025 (15)	0.0131 (16)	−0.0029 (15)
C3D	0.077 (3)	0.054 (2)	0.044 (2)	−0.0085 (18)	0.028 (2)	−0.0078 (17)
N4D	0.0560 (18)	0.065 (2)	0.075 (2)	−0.0101 (16)	0.0441 (16)	−0.0187 (18)
C5D	0.0384 (19)	0.046 (2)	0.077 (3)	−0.0056 (14)	0.0268 (18)	−0.0127 (18)
C6D	0.0361 (18)	0.0454 (19)	0.0454 (19)	−0.0038 (14)	0.0075 (15)	−0.0034 (15)
N7D	0.0407 (15)	0.078 (2)	0.0440 (17)	0.0000 (15)	0.0196 (13)	0.0059 (16)
O1W	0.0524 (16)	0.0566 (15)	0.0396 (13)	−0.0102 (11)	−0.0017 (10)	0.0056 (11)
O2W	0.0509 (14)	0.0623 (16)	0.0432 (14)	−0.0037 (12)	0.0059 (11)	0.0019 (12)
O3W	0.0573 (16)	0.0682 (18)	0.0502 (16)	0.0116 (13)	−0.0063 (12)	−0.0056 (13)
O4W	0.0390 (13)	0.0574 (14)	0.0456 (13)	−0.0033 (10)	0.0012 (10)	−0.0063 (12)

Geometric parameters (Å, º)

C1A—N10A	1.381 (5)	C2C—H2C	0.9500
C1A—C2A	1.384 (5)	C3C—C4C	1.353 (5)
C1A—C6A	1.409 (5)	C3C—H3C	0.9500
C2A—C3A	1.378 (5)	C4C—C5C	1.418 (5)
C2A—H2A	0.9500	C4C—C7C	1.495 (5)
C3A—C4A	1.426 (4)	C5C—C6C	1.371 (5)
C3A—H3A	0.9500	C5C—H5C	0.9500
C4A—C5A	1.375 (5)	C6C—H6C	0.9500
C4A—C7A	1.485 (5)	C7C—O8C	1.265 (4)
C5A—C6A	1.377 (5)	C7C—O9C	1.268 (4)
C5A—H5A	0.9500	N10C—H10C	0.8800
C6A—H6A	0.9500	N10C—H10D	0.8800
C7A—O8A	1.266 (4)	C1D—N7D	1.350 (4)
C7A—O9A	1.267 (4)	C1D—C2D	1.387 (5)
N10A—H10A	0.8800	C1D—C6D	1.421 (5)
N10A—H10B	0.8800	C2D—C3D	1.364 (5)
C1B—N7B	1.313 (5)	C2D—H2D	0.9500
C1B—C2B	1.404 (5)	C3D—N4D	1.387 (6)
C1B—C6B	1.429 (5)	C3D—H3D	0.9500
C2B—C3B	1.353 (7)	N4D—C5D	1.307 (6)
C2B—H2B	0.9500	N4D—H4D	0.8800
C3B—N4B	1.374 (6)	C5D—C6D	1.360 (6)
C3B—H3B	0.9500	C5D—H5D	0.9500
N4B—C5B	1.300 (6)	C6D—H6D	0.9500
N4B—H4B	0.8800	N7D—H7D	0.8800
C5B—C6B	1.341 (6)	N7D—H7E	0.8800
C5B—H5B	0.9500	O1W—H1W	0.9635
C6B—H6B	0.9500	O1W—H2W	0.9611
N7B—H7B	0.8800	O2W—H3W	0.9734
N7B—H7C	0.8800	O2W—H4W	0.9723
C1C—N10C	1.335 (5)	O3W—H5W	0.9623
C1C—C6C	1.399 (5)	O3W—H6W	0.9604
C1C—C2C	1.432 (5)	O4W—H7W	0.9715
C2C—C3C	1.361 (5)	O4W—H8W	0.9630
N10A—C1A—C2A	119.5 (3)	C6C—C1C—C2C	115.9 (3)
N10A—C1A—C6A	120.5 (4)	C3C—C2C—C1C	120.7 (3)
C2A—C1A—C6A	120.1 (3)	C3C—C2C—H2C	119.7
C3A—C2A—C1A	120.5 (3)	C1C—C2C—H2C	119.7
C3A—C2A—H2A	119.8	C4C—C3C—C2C	122.9 (3)
C1A—C2A—H2A	119.8	C4C—C3C—H3C	118.6
C2A—C3A—C4A	120.4 (3)	C2C—C3C—H3C	118.6
C2A—C3A—H3A	119.8	C3C—C4C—C5C	118.2 (3)
C4A—C3A—H3A	119.8	C3C—C4C—C7C	122.0 (3)
C5A—C4A—C3A	117.5 (3)	C5C—C4C—C7C	119.8 (3)
C5A—C4A—C7A	123.0 (3)	C6C—C5C—C4C	119.8 (3)
C3A—C4A—C7A	119.5 (3)	C6C—C5C—H5C	120.1
C4A—C5A—C6A	123.2 (3)	C4C—C5C—H5C	120.1
C4A—C5A—H5A	118.4	C5C—C6C—C1C	122.6 (3)
C6A—C5A—H5A	118.4	C5C—C6C—H6C	118.7
C5A—C6A—C1A	118.4 (3)	C1C—C6C—H6C	118.7
C5A—C6A—H6A	120.8	O8C—C7C—O9C	121.0 (3)
C1A—C6A—H6A	120.8	O8C—C7C—C4C	118.8 (3)
O8A—C7A—O9A	120.8 (3)	O9C—C7C—C4C	120.2 (3)
O8A—C7A—C4A	118.8 (3)	C1C—N10C—H10C	120.0
O9A—C7A—C4A	120.5 (3)	C1C—N10C—H10D	120.0
C1A—N10A—H10A	120.0	H10C—N10C—H10D	120.0
C1A—N10A—H10B	120.0	N7D—C1D—C2D	120.2 (4)
H10A—N10A—H10B	120.0	N7D—C1D—C6D	120.5 (4)
N7B—C1B—C2B	122.8 (3)	C2D—C1D—C6D	119.3 (3)
N7B—C1B—C6B	122.2 (3)	C3D—C2D—C1D	119.7 (4)
C2B—C1B—C6B	114.9 (3)	C3D—C2D—H2D	120.1
C3B—C2B—C1B	122.0 (4)	C1D—C2D—H2D	120.1
C3B—C2B—H2B	119.0	C2D—C3D—N4D	119.7 (4)
C1B—C2B—H2B	119.0	C2D—C3D—H3D	120.2
C2B—C3B—N4B	119.4 (4)	N4D—C3D—H3D	120.2
C2B—C3B—H3B	120.3	C5D—N4D—C3D	120.4 (3)
N4B—C3B—H3B	120.3	C5D—N4D—H4D	119.8
C5B—N4B—C3B	120.5 (4)	C3D—N4D—H4D	119.8
C5B—N4B—H4B	119.7	N4D—C5D—C6D	123.6 (4)
C3B—N4B—H4B	119.7	N4D—C5D—H5D	118.2
N4B—C5B—C6B	122.9 (4)	C6D—C5D—H5D	118.2
N4B—C5B—H5B	118.5	C5D—C6D—C1D	117.3 (4)
C6B—C5B—H5B	118.5	C5D—C6D—H6D	121.4
C5B—C6B—C1B	120.2 (4)	C1D—C6D—H6D	121.4
C5B—C6B—H6B	119.9	C1D—N7D—H7D	120.0
C1B—C6B—H6B	119.9	C1D—N7D—H7E	120.0
C1B—N7B—H7B	120.0	H7D—N7D—H7E	120.0
C1B—N7B—H7C	120.0	H1W—O1W—H2W	106.8
H7B—N7B—H7C	120.0	H3W—O2W—H4W	104.4
N10C—C1C—C6C	122.2 (3)	H5W—O3W—H6W	107.1
N10C—C1C—C2C	121.9 (3)	H7W—O4W—H8W	105.2
N10A—C1A—C2A—C3A	−179.5 (4)	N10C—C1C—C2C—C3C	179.9 (4)
C6A—C1A—C2A—C3A	2.1 (6)	C6C—C1C—C2C—C3C	−0.9 (6)
C1A—C2A—C3A—C4A	0.1 (6)	C1C—C2C—C3C—C4C	1.4 (6)
C2A—C3A—C4A—C5A	−0.7 (5)	C2C—C3C—C4C—C5C	−1.2 (6)
C2A—C3A—C4A—C7A	179.7 (3)	C2C—C3C—C4C—C7C	179.4 (4)
C3A—C4A—C5A—C6A	−0.9 (5)	C3C—C4C—C5C—C6C	0.7 (5)
C7A—C4A—C5A—C6A	178.6 (4)	C7C—C4C—C5C—C6C	−179.9 (3)
C4A—C5A—C6A—C1A	3.1 (6)	C4C—C5C—C6C—C1C	−0.4 (5)
N10A—C1A—C6A—C5A	178.0 (4)	N10C—C1C—C6C—C5C	179.6 (4)
C2A—C1A—C6A—C5A	−3.6 (6)	C2C—C1C—C6C—C5C	0.5 (5)
C5A—C4A—C7A—O8A	8.0 (5)	C3C—C4C—C7C—O8C	5.8 (5)
C3A—C4A—C7A—O8A	−172.5 (3)	C5C—C4C—C7C—O8C	−173.6 (3)
C5A—C4A—C7A—O9A	−171.9 (3)	C3C—C4C—C7C—O9C	−174.8 (3)
C3A—C4A—C7A—O9A	7.7 (5)	C5C—C4C—C7C—O9C	5.8 (4)
N7B—C1B—C2B—C3B	−179.0 (4)	N7D—C1D—C2D—C3D	−178.7 (4)
C6B—C1B—C2B—C3B	1.4 (5)	C6D—C1D—C2D—C3D	1.8 (6)
C1B—C2B—C3B—N4B	−2.1 (6)	C1D—C2D—C3D—N4D	−0.4 (6)
C2B—C3B—N4B—C5B	1.4 (6)	C2D—C3D—N4D—C5D	−0.4 (6)
C3B—N4B—C5B—C6B	0.1 (7)	C3D—N4D—C5D—C6D	−0.3 (6)
N4B—C5B—C6B—C1B	−0.8 (7)	N4D—C5D—C6D—C1D	1.6 (6)
N7B—C1B—C6B—C5B	−179.6 (4)	N7D—C1D—C6D—C5D	178.1 (4)
C2B—C1B—C6B—C5B	0.1 (6)	C2D—C1D—C6D—C5D	−2.4 (6)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1W—H1W···O9A^i	0.96	1.84	2.763 (4)	159
O1W—H2W···O9C	0.96	1.83	2.767 (4)	165
O2W—H3W···O8A^ii	0.97	1.80	2.760 (4)	170
N4B—H4B···O8A^i	0.88	1.99	2.808 (5)	153
N4B—H4B···O9A^i	0.88	2.18	2.936 (5)	143
N4D—H4D···O8C^iii	0.88	2.09	2.883 (5)	150
N4D—H4D···O9C^iii	0.88	2.08	2.859 (5)	146
O2W—H4W···O8C^iii	0.97	1.83	2.748 (4)	156
O3W—H5W···O8C^iii	0.96	1.80	2.754 (4)	169
O3W—H6W···O8A	0.96	1.80	2.741 (4)	166
N7B—H7B···O2W	0.88	2.09	2.965 (4)	173
N7B—H7C···O4W^iv	0.88	2.09	2.967 (5)	172
N7D—H7D···O2W^v	0.88	2.10	2.973 (5)	173
N7D—H7E···O1W	0.88	2.06	2.938 (4)	174
O4W—H7W···O9C	0.97	1.85	2.768 (4)	156
O4W—H8W···O9A^vi	0.96	1.78	2.740 (4)	179
N10A—H10A···O3W^v	0.88	2.21	3.085 (5)	176
N10A—H10B···O4W	0.88	2.14	3.015 (4)	176
N10C—H10C···O3W	0.88	2.12	3.000 (5)	177
N10C—H10D···O1W^vii	0.88	2.26	3.136 (5)	178

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

(II) 4-aminopyridinium nicotinate

Crystal data

C5H7N2^+·C6H4NO2^−	F(000) = 456
Mr = 217.23	Dx = 1.391 Mg m^−3
Monoclinic, P21/c	Cu Kα radiation, λ = 1.54178 Å
Hall symbol: -P 2ybc	Cell parameters from 25 reflections
a = 11.9645 (17) Å	θ = 65–69°
b = 8.2635 (5) Å	µ = 0.82 mm^−1
c = 11.305 (3) Å	T = 193 K
β = 111.854 (7)°	Block, colourless
V = 1037.4 (3) Å^3	0.26 × 0.19 × 0.13 mm
Z = 4

Data collection

Enraf–Nonius CAD-4 diffractometer	1837 reflections with I > 2σ(I)
Radiation source: rotating anode	Rint = 0.022
Graphite monochromator	θmax = 70.2°, θmin = 4.0°
ω/2θ scans	h = −14→13
Absorption correction: ψ scan (CORINC; Draeger & Gattow, 1971)	k = 0→10
Tmin = 0.815, Tmax = 0.901	l = 0→13
2068 measured reflections	3 standard reflections every 60 min
1960 independent reflections	intensity decay: 2%

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)] = 0.062	H-atom parameters constrained
wR(F^2) = 0.220	w = 1/[σ^2(Fo^2) + (0.1456P)^2 + 0.5559P] where P = (Fo^2 + 2Fc^2)/3
S = 1.13	(Δ/σ)max < 0.001
1960 reflections	Δρmax = 0.35 e Å^−3
146 parameters	Δρmin = −0.38 e Å^−3
0 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: 0.016 (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	0.45422 (16)	0.2987 (2)	0.44351 (18)	0.0329 (5)
H1	0.5078	0.2289	0.5008	0.039*
C2	0.47405 (19)	0.3494 (3)	0.3405 (2)	0.0331 (6)
H2	0.5457	0.3168	0.3295	0.040*
C3	0.39413 (18)	0.4466 (3)	0.2510 (2)	0.0306 (5)
H3	0.4094	0.4795	0.1779	0.037*
C4	0.28780 (17)	0.4982 (2)	0.2681 (2)	0.0285 (5)
C5	0.27057 (18)	0.4429 (3)	0.3777 (2)	0.0327 (6)
H5	0.2005	0.4739	0.3926	0.039*
C6	0.3541 (2)	0.3449 (3)	0.4629 (2)	0.0336 (6)
H6	0.3416	0.3088	0.5368	0.040*
N7	0.20697 (16)	0.5928 (2)	0.18238 (18)	0.0339 (5)
H7A	0.1417	0.6262	0.2090	0.051*
H7B	0.2280	0.6310	0.1203	0.051*
C8	0.79754 (17)	−0.0010 (2)	0.6998 (2)	0.0279 (5)
C9	0.89015 (19)	−0.0577 (3)	0.6641 (2)	0.0322 (5)
H9	0.8880	−0.0307	0.5816	0.039*
N10	0.98191 (16)	−0.1482 (2)	0.7393 (2)	0.0382 (6)
C11	0.9832 (2)	−0.1853 (3)	0.8545 (2)	0.0390 (6)
H11	1.0483	−0.2481	0.9095	0.047*
C12	0.8944 (2)	−0.1371 (3)	0.8982 (2)	0.0408 (6)
H12	0.8981	−0.1675	0.9806	0.049*
C13	0.7999 (2)	−0.0433 (3)	0.8188 (2)	0.0373 (6)
H13	0.7376	−0.0087	0.8460	0.045*
C14	0.69835 (18)	0.1037 (3)	0.60888 (19)	0.0285 (5)
O15	0.71755 (14)	0.1689 (2)	0.51889 (15)	0.0372 (5)
O16	0.60445 (13)	0.1179 (2)	0.63279 (16)	0.0386 (5)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0228 (9)	0.0315 (9)	0.0417 (10)	0.0024 (7)	0.0090 (8)	0.0014 (7)
C2	0.0213 (10)	0.0336 (11)	0.0461 (13)	0.0005 (8)	0.0143 (9)	−0.0030 (9)
C3	0.0247 (10)	0.0336 (11)	0.0359 (11)	−0.0019 (8)	0.0143 (8)	−0.0019 (8)
C4	0.0200 (10)	0.0271 (10)	0.0374 (11)	−0.0033 (7)	0.0093 (8)	−0.0044 (8)
C5	0.0232 (10)	0.0344 (11)	0.0440 (12)	0.0021 (8)	0.0166 (9)	0.0033 (9)
C6	0.0304 (11)	0.0354 (11)	0.0369 (11)	0.0005 (9)	0.0148 (9)	0.0002 (8)
N7	0.0236 (9)	0.0384 (11)	0.0408 (10)	0.0032 (7)	0.0132 (8)	0.0051 (8)
C8	0.0201 (10)	0.0259 (10)	0.0381 (11)	−0.0020 (8)	0.0115 (8)	−0.0011 (8)
C9	0.0251 (10)	0.0312 (11)	0.0432 (12)	0.0009 (8)	0.0161 (9)	0.0020 (9)
N10	0.0227 (10)	0.0340 (10)	0.0591 (13)	0.0046 (7)	0.0167 (9)	0.0038 (9)
C11	0.0279 (11)	0.0346 (12)	0.0509 (14)	0.0053 (9)	0.0105 (10)	0.0064 (9)
C12	0.0406 (13)	0.0444 (13)	0.0397 (13)	0.0090 (10)	0.0174 (10)	0.0097 (10)
C13	0.0299 (11)	0.0399 (13)	0.0472 (13)	0.0075 (9)	0.0202 (10)	0.0059 (10)
C14	0.0227 (10)	0.0291 (11)	0.0341 (11)	−0.0002 (8)	0.0110 (8)	−0.0040 (8)
O15	0.0327 (9)	0.0447 (10)	0.0374 (9)	0.0089 (7)	0.0165 (7)	0.0053 (7)
O16	0.0227 (8)	0.0474 (10)	0.0483 (10)	0.0083 (6)	0.0163 (7)	0.0093 (7)

Geometric parameters (Å, º)

N1—C2	1.339 (3)	C8—C13	1.380 (3)
N1—C6	1.350 (3)	C8—C9	1.394 (3)
N1—H1	0.9237	C8—C14	1.518 (3)
C2—C3	1.365 (3)	C9—N10	1.339 (3)
C2—H2	0.9500	C9—H9	0.9500
C3—C4	1.422 (3)	N10—C11	1.332 (3)
C3—H3	0.9500	C11—C12	1.387 (3)
C4—N7	1.337 (3)	C11—H11	0.9500
C4—C5	1.406 (3)	C12—C13	1.389 (3)
C5—C6	1.366 (3)	C12—H12	0.9500
C5—H5	0.9500	C13—H13	0.9500
C6—H6	0.9500	C14—O15	1.246 (3)
N7—H7A	0.9757	C14—O16	1.255 (2)
N7—H7B	0.8870
C2—N1—C6	120.52 (19)	H7A—N7—H7B	129.7
C2—N1—H1	120.2	C13—C8—C9	117.84 (19)
C6—N1—H1	119.2	C13—C8—C14	122.09 (18)
N1—C2—C3	121.79 (19)	C9—C8—C14	120.08 (19)
N1—C2—H2	119.1	N10—C9—C8	123.8 (2)
C3—C2—H2	119.1	N10—C9—H9	118.1
C2—C3—C4	119.4 (2)	C8—C9—H9	118.1
C2—C3—H3	120.3	C11—N10—C9	117.27 (19)
C4—C3—H3	120.3	N10—C11—C12	123.4 (2)
N7—C4—C5	121.67 (18)	N10—C11—H11	118.3
N7—C4—C3	121.27 (19)	C12—C11—H11	118.3
C5—C4—C3	117.05 (19)	C11—C12—C13	118.5 (2)
C6—C5—C4	120.34 (19)	C11—C12—H12	120.8
C6—C5—H5	119.8	C13—C12—H12	120.8
C4—C5—H5	119.8	C8—C13—C12	119.2 (2)
N1—C6—C5	120.9 (2)	C8—C13—H13	120.4
N1—C6—H6	119.5	C12—C13—H13	120.4
C5—C6—H6	119.5	O15—C14—O16	125.99 (19)
C4—N7—H7A	112.8	O15—C14—C8	117.64 (17)
C4—N7—H7B	116.1	O16—C14—C8	116.37 (18)
C6—N1—C2—C3	−1.0 (3)	C8—C9—N10—C11	0.2 (3)
N1—C2—C3—C4	1.1 (3)	C9—N10—C11—C12	0.9 (4)
C2—C3—C4—N7	−179.67 (19)	N10—C11—C12—C13	−0.9 (4)
C2—C3—C4—C5	−0.8 (3)	C9—C8—C13—C12	1.2 (3)
N7—C4—C5—C6	179.3 (2)	C14—C8—C13—C12	−178.9 (2)
C3—C4—C5—C6	0.4 (3)	C11—C12—C13—C8	−0.2 (4)
C2—N1—C6—C5	0.6 (3)	C13—C8—C14—O15	162.6 (2)
C4—C5—C6—N1	−0.3 (3)	C9—C8—C14—O15	−17.5 (3)
C13—C8—C9—N10	−1.2 (3)	C13—C8—C14—O16	−16.6 (3)
C14—C8—C9—N10	178.81 (19)	C9—C8—C14—O16	163.32 (19)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O16	0.92	1.77	2.680 (2)	169
N1—H1···O15	0.92	2.49	3.131 (2)	127
N7—H7A···N10^i	0.98	2.07	3.027 (3)	166
N7—H7B···O15^ii	0.89	1.94	2.814 (2)	168

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