2-Amino­pyridin-1-ium triiodide

Reiss, G.J.; Leske, P.B.

doi:10.1107/S1600536813015389

organic compounds

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Volume 69| Part 7| July 2013| Pages o1060-o1061

https://doi.org/10.1107/S1600536813015389

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2-Aminopyridin-1-ium triiodide

Guido J. Reiss ^a ^* and Peer B. Leske ^a

^aInstitut für Anorganische Chemie und Strukturchemie, Lehrstuhl II: Material- und Strukturforschung, Heinrich-Heine-Universität Düsseldorf, Universitätsstrasse 1, D-40225 Düsseldorf, Germany
^*Correspondence e-mail: reissg@hhu.de

(Received 30 May 2013; accepted 3 June 2013; online 8 June 2013)

The asymmetric unit of the title compound, C₅H₇N₂^+.I₃⁻, consists of one 2-aminopyridin-1-ium cation (apyH⁺) and one triiodide anion, both located in general postions. The apyH⁺ cation is planar within the experimental uncertainties. The short N—C distance [1.328 (5) Å] of the exocyclic NH₂ group is typical for the imino-form of protonated 2-aminopyridines. Consequently, the bond lengths within the six-membered ring vary significantly. The geometric parameters of the triiodide anion are in the typical range, with bond lengths of 2.8966 (3) and 2.9389 (3) Å and a bond angle of 176.02 (1)°. In the crystal, N—H ⋯ I hydrogen bonds connect adjacent ions into screwed chains along the b-axis direction. These chains are twisted pairwise into rectangular rods. The pyridinium moieties of neighbouring rods are arranged parallel to each other with a plane-to-plane distance of 3.423 (5) Å.

Related literature

For the biological activity of aminopyridines, see: Bolliger et al. (2011 ); Muñoz-Caro & Niño (2002 ). For aminopyridinium salts with non-linear optical properties, see: Srinivasan & Priolkar (2013 ); Shkir et al. (2012 ); Periyasamy et al. (2007 ). For the spectroscopy of aminopyridinium salts, see: Çırak et al. (2011 ). For bond-order calculations, see: Brown (2009 ). For the protonation and electronic structure of 2 amiopyridin-1-ium cations, see: Chapkanov (2010 ); Chai et al. (2009 ); Testa & Wild (1981 ). For the spectroscopy of polyiodides, see: Deplano et al. (1999). For pyridine–pyridine interactions, see: Ninković et al. (2012 ); Berl et al. (2000 ); Janiak (2000 ). For related poliodides, see: van Megen & Reiss (2012 ); Reiss & van Megen (2012a ,b ); Meyer et al. (2010 ); Reiss & Engel (2002 , 2004 ). For the elemental analysis of polyiodides, see: Reiss & van Megen (2012b); Egli (1969 ).

Experimental

Crystal data

C₅H₇N₂⁺·I₃⁻
M_r = 475.83
Triclinic, $[P \overline 1]$
a = 8.0446 (4) Å
b = 8.9973 (5) Å
c = 9.1464 (4) Å
α = 117.805 (6)°
β = 90.939 (4)°
γ = 109.640 (5)°
V = 539.46 (6) Å³
Z = 2
Mo Kα radiation
μ = 8.64 mm⁻¹
T = 100 K
0.43 × 0.41 × 0.04 mm

Data collection

Oxford Diffraction Xcalibur Eos diffractometer
Absorption correction: analytical [CrysAlis PRO (Oxford Diffraction, 2009 $[Oxford Diffraction (2009). CrysAlis PRO. Oxford Diffraction Ltd, Yarnton, England.]$ ) based on expressions derived by Clark & Reid (1995 )] T_min = 0.083, T_max = 0.698
5668 measured reflections
2186 independent reflections
2078 reflections with I > 2σ(I)
R_int = 0.021

Refinement

R[F² > 2σ(F²)] = 0.018
wR(F²) = 0.041
S = 1.01
2186 reflections
117 parameters
2 restraints
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.99 e Å⁻³
Δρ_min = −0.59 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H11⋯I1	0.85 (1)	2.99 (3)	3.698 (3)	142 (4)
N1—H12⋯I3ⁱ	0.85 (1)	2.89 (2)	3.709 (3)	164 (4)
N2—H2⋯I1	0.83 (4)	2.97 (5)	3.702 (3)	147 (4)
Symmetry code: (i) x, y+1, z.

Data collection: CrysAlis PRO (Oxford Diffraction, 2009 $[Oxford Diffraction (2009). CrysAlis PRO. Oxford Diffraction Ltd, Yarnton, England.]$ ); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SHELXS2013 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL2013 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2012 ); software used to prepare material for publication: publCIF (Westrip, 2010 ).

Supporting information

Crystal structure: contains datablocks I, New_Global_Publ_Block. DOI: https://doi.org/10.1107/S1600536813015389/hg5319sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536813015389/hg5319Isup2.hkl

checkCIF report

Comment top

Aminopyridines are of general interest as they show biological activity (Bolliger et al., 2011). Especially the monoprotonated cations are able to inactivate K⁺ channels reversibly (Muñoz-Caro & Niño, 2002). Another field of research related to 2-aminopyridinium salts is focused on their nonlinear optical properties (Srinivasan & Priolkar, 2013; Shkir, et al., 2012; Periyasamy et al., 2007). There are more than one hundred mono-protonated 2-aminopyridin-1-ium cations (apyH⁺) listed in the Cambridge Structural Database. Common to all is the protonation at the ring-nitrogen atom. Moreover, a short exocyclic C—N bond is typically for this cation which represents the so-called imino-form (Scheme 1). The electronic consequences of the mono-protonation of 2-Aminopyridine (Chai et al., 2009; Testa & Wild, 1981) and the electronic structure of the resulting apyH⁺ monocation (Chapkanov, 2010) seem to be well understood. This contribution is part of our ongoing general interest in the hydrogen bonding of polyiodide salts (Reiss & Engel, 2002; Reiss & Engel, 2004; Meyer et al., 2010). This applies in particular to the structural chemistry of aromatic nitrogen-containing polyiodide salts (Reiss & van Megen, 2012a).

The asymmetric unit of the title structure consists of one 2-aminopyridin-1-ium cation and one I₃^- anion both located in general positions (Fig. 1). The geometric parameters of the apyH⁺ cation are in accord with the imino-form of a protonated 2-aminopyridine. The C–C and C–N bond lengths within the ring show C–N distances of 1.353 (5) and 1.354 (5) Å and C—C bond lengths ranging from 1.355 (5) to 1.411 (5) Å. The exocyclic C–N bond length is with 1.328 (5) Å very short, thus in the expected range for the imino-form of a protonated aminopyridine. Bond valence calculations for the apyH⁺ cation were performed using Brown's empirical method (Brown, 2009). The three different C–N bond lengths correspond to bond orders of 1.27 to 1.36, whereas the bond orders of the C–C bonds vary between 1.42 and 1.65 (Scheme 1). The geometric parameters of the triiodide anion are also in the typical range for a hydrogen bonded triiodide anion (e.g. van Megen & Reiss, 2012) with bond lengths of 2.8966 (3) and 2.9389 (3) Å and a bond angle of 176.02 (1)°. The Raman spectrum shows two intense signals at 126 and 115 cm^-1 and a medium strong signal at 73 cm^-1 which all are in excellent accord with the geometric parameters of the triiodide anion of the title structure and literature known examples (Deplano et al., 1999). The Raman and the infrared spectrum show a vast number of bands from 4000 to 400 cm^-1 which are in the expected ranges for the apyH⁺ monocation (Çırak, 2011; Fig. 2).

Cations and anions are connected by N–H ··· I hydrogen bonds. Each cation donates three un-bifurcated hydrogen bonds by the three hydrogen atoms attached to nitrogen atoms to two adjacent triiodide anions (Fig. 1). By these connections chains along the b direction are formed (Fig. 3). The hydrogen bonded chains are twisted pairwise to rectangular rods. These double chains (rods) (Fig. 3 and 4) are connected to adjacent ones by pyridine-pyridine interactions which are arranged in parallel with a plane to plane distance of 3.423 Å. This value is in excellent agreement with the results of ab initio calculations reported recently (Ninković et al., 2012). In general, π-π interactions of pyridine moieties may play an important role in the biological system (Berl et al., 2000) and are of significant interest in the structural chemistry of metal complexes with aromatic nitrogen-containing ligands (Janiak, 2000).

Related literature top

For the biological activity of aminopyridines, see: Bolliger et al. (2011); Muñoz-Caro & Niño (2002). For aminopyridinium salts with non-linear optical properties, see: Srinivasan & Priolkar (2013); Shkir et al. (2012); Periyasamy et al. (2007). For the spectroscopy of aminopyridinium salts, see: Çırak et al. (2011). For bond-order calculations, see: Brown (2009). For the protonation and electronic structure of 2 amiopyridin-1-ium cations, see: Chapkanov (2010); Chai et al. (2009); Testa & Wild (1981). For the spectroscopy of polyiodides, see: Deplano et al. (1999). For pyridine–pyridine interactions, see: Ninković et al. (2012); Berl et al. (2000); Janiak (2000). For related poliodides, see: van Megen & Reiss (2012); Reiss & van Megen (2012a,b); Meyer et al. (2010); Reiss & Engel (2002, 2004). For the elemental analysis of polyiodides, see: Reiss & van Megen (2012b\bbr9 021); Egli (1969).

Experimental top

2-Aminopyridine (0.16 g; 1.7 mmol) was dissolved in 10 ml concentrated hydroiodic acid yielding a brown mixture. This mixture was heated to 90 °C and then slowly cooled to room temperature. Within 12 h needle-shaped, orange crystals grew from this solution. Elemental analysis (C₅H₇N₂I₃): calcd., %: C, 12.62; H, 1.48; N, 5.89; I, 80.01. Found, %: C, 12.07; H, 1.45; N, 5.60; I, 79.44. For details on the elemental analytical methods used, see: Reiss & van Megen (2012b); Egli (1969).

Structure description top

For the biological activity of aminopyridines, see: Bolliger et al. (2011); Muñoz-Caro & Niño (2002). For aminopyridinium salts with non-linear optical properties, see: Srinivasan & Priolkar (2013); Shkir et al. (2012); Periyasamy et al. (2007). For the spectroscopy of aminopyridinium salts, see: Çırak et al. (2011). For bond-order calculations, see: Brown (2009). For the protonation and electronic structure of 2 amiopyridin-1-ium cations, see: Chapkanov (2010); Chai et al. (2009); Testa & Wild (1981). For the spectroscopy of polyiodides, see: Deplano et al. (1999). For pyridine–pyridine interactions, see: Ninković et al. (2012); Berl et al. (2000); Janiak (2000). For related poliodides, see: van Megen & Reiss (2012); Reiss & van Megen (2012a,b); Meyer et al. (2010); Reiss & Engel (2002, 2004). For the elemental analysis of polyiodides, see: Reiss & van Megen (2012b\bbr9 021); Egli (1969).

Computing details top

Data collection: CrysAlis PRO (Oxford Diffraction, 2009); cell refinement: CrysAlis PRO (Oxford Diffraction, 2009); data reduction: CrysAlis PRO (Oxford Diffraction, 2009); program(s) used to solve structure: SHELXS2013 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2013 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2012); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures top

	Fig. 1. Showing the asymmetric unit of the title structure (Displacement ellipsoids are drawn at the 50% probability level).
	Fig. 2. Shows the infrared spectrum (upper part) and Raman spectrum (lower part) of the title compound.
	Fig. 3. Pairwise twisted (green/violet and red/blue) hydrogen bonded chains run along [010].
	Fig. 4. Showing the packing of rectangular rods constructed by pairwise twisted chains. π-π interactions are visualized by black lines connecting the centres of neighbouring rings.

2-Aminopyridin-1-ium triiodide top

Crystal data top

C₅H₇N₂⁺·I₃⁻	Z = 2
M_r = 475.83	F(000) = 420
Triclinic, P1	D_x = 2.929 Mg m⁻³
a = 8.0446 (4) Å	Mo Kα radiation, λ = 0.71073 Å
b = 8.9973 (5) Å	Cell parameters from 6254 reflections
c = 9.1464 (4) Å	θ = 3.1–32.6°
α = 117.805 (6)°	µ = 8.64 mm⁻¹
β = 90.939 (4)°	T = 100 K
γ = 109.640 (5)°	Plate, orange
V = 539.46 (6) Å³	0.43 × 0.41 × 0.04 mm

Data collection top

Oxford Diffraction Xcalibur Eos diffractometer	2186 independent reflections
Radiation source: Sealed tube X-ray Source	2078 reflections with I > 2σ(I)
Equatorial mounted graphite monochromator	R_int = 0.021
Detector resolution: 16.2711 pixels mm^-1	θ_max = 26.3°, θ_min = 3.1°
ω scans	h = −10→9
Absorption correction: analytical [CrysAlis PRO (Oxford Diffraction, 2009) based on expressions derived by Clark & Reid (1995)]	k = −11→11
T_min = 0.083, T_max = 0.698	l = −11→11
5668 measured reflections

Refinement top

Refinement on F²	Hydrogen site location: difference Fourier map
Least-squares matrix: full	H atoms treated by a mixture of independent and constrained refinement
R[F² > 2σ(F²)] = 0.018	w = 1/[σ²(F_o²) + (0.015P)² + 1.5P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.041	(Δ/σ)_max = 0.001
S = 1.01	Δρ_max = 0.99 e Å⁻³
2186 reflections	Δρ_min = −0.59 e Å⁻³
117 parameters	Extinction correction: SHELXL, Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
2 restraints	Extinction coefficient: 0.0075 (2)

Crystal data top

C₅H₇N₂⁺·I₃⁻	γ = 109.640 (5)°
M_r = 475.83	V = 539.46 (6) Å³
Triclinic, P1	Z = 2
a = 8.0446 (4) Å	Mo Kα radiation
b = 8.9973 (5) Å	µ = 8.64 mm⁻¹
c = 9.1464 (4) Å	T = 100 K
α = 117.805 (6)°	0.43 × 0.41 × 0.04 mm
β = 90.939 (4)°

Data collection top

Oxford Diffraction Xcalibur Eos diffractometer	2186 independent reflections
Absorption correction: analytical [CrysAlis PRO (Oxford Diffraction, 2009) based on expressions derived by Clark & Reid (1995)]	2078 reflections with I > 2σ(I)
T_min = 0.083, T_max = 0.698	R_int = 0.021
5668 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.018	2 restraints
wR(F²) = 0.041	H atoms treated by a mixture of independent and constrained refinement
S = 1.01	Δρ_max = 0.99 e Å⁻³
2186 reflections	Δρ_min = −0.59 e Å⁻³
117 parameters

Special details top

Experimental. Analytical numeric absorption correction using a multifaceted crystal model based on expressions derived by Clark & Reid (1995).

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
I1	0.09076 (3)	0.38499 (3)	0.61148 (3)	0.01704 (8)
I2	0.19010 (3)	0.35305 (3)	0.90314 (3)	0.01422 (7)
I3	0.26150 (3)	0.30976 (3)	1.18942 (3)	0.01955 (8)
N1	0.2469 (4)	0.8865 (5)	0.8153 (4)	0.0250 (7)
H11	0.162 (4)	0.782 (3)	0.774 (5)	0.031 (12)*
H12	0.236 (6)	0.968 (5)	0.907 (3)	0.037 (13)*
N2	0.4056 (4)	0.7899 (4)	0.6047 (4)	0.0182 (6)
H2	0.325 (6)	0.686 (6)	0.561 (5)	0.026 (12)*
C1	0.3907 (4)	0.9236 (5)	0.7495 (4)	0.0166 (7)
C3	0.5493 (5)	0.8151 (5)	0.5310 (5)	0.0186 (7)
H3	0.547 (5)	0.712 (6)	0.435 (5)	0.022*
C4	0.6862 (5)	0.9812 (5)	0.5996 (5)	0.0217 (8)
H4	0.783 (6)	0.990 (6)	0.549 (5)	0.026*
C5	0.6744 (5)	1.1248 (5)	0.7472 (5)	0.0218 (8)
H5	0.763 (6)	1.249 (6)	0.799 (5)	0.026 (11)*
C6	0.5316 (5)	1.0977 (5)	0.8221 (5)	0.0192 (7)
H6	0.520 (5)	1.191 (6)	0.915 (5)	0.023*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
I1	0.01701 (12)	0.01880 (13)	0.01929 (13)	0.00609 (9)	0.00315 (8)	0.01316 (10)
I2	0.01360 (12)	0.01388 (12)	0.01490 (12)	0.00556 (9)	0.00260 (8)	0.00688 (9)
I3	0.02394 (13)	0.02233 (13)	0.01393 (12)	0.01008 (10)	0.00330 (9)	0.00953 (10)
N1	0.0238 (17)	0.0189 (17)	0.0238 (17)	0.0040 (14)	0.0102 (14)	0.0070 (15)
N2	0.0174 (14)	0.0122 (15)	0.0205 (15)	0.0032 (12)	0.0019 (12)	0.0068 (13)
C1	0.0165 (16)	0.0179 (18)	0.0177 (17)	0.0060 (14)	0.0010 (13)	0.0111 (15)
C3	0.0182 (17)	0.0172 (18)	0.0216 (18)	0.0094 (14)	0.0050 (14)	0.0090 (15)
C4	0.0165 (17)	0.0216 (19)	0.028 (2)	0.0087 (15)	0.0073 (15)	0.0126 (17)
C5	0.0162 (17)	0.0159 (18)	0.028 (2)	0.0045 (15)	0.0002 (14)	0.0084 (16)
C6	0.0181 (17)	0.0158 (18)	0.0185 (18)	0.0063 (14)	−0.0013 (14)	0.0051 (15)

Geometric parameters (Å, º) top

I1—I2	2.9389 (3)	C1—C6	1.411 (5)
I2—I3	2.8966 (3)	C3—C4	1.355 (5)
N1—C1	1.328 (5)	C3—H3	0.93 (4)
N1—H11	0.849 (10)	C4—C5	1.400 (5)
N1—H12	0.847 (10)	C4—H4	0.91 (4)
N2—C1	1.353 (5)	C5—C6	1.358 (5)
N2—C3	1.354 (5)	C5—H5	0.97 (4)
N2—H2	0.83 (4)	C6—H6	0.91 (4)

I3—I2—I1	176.017 (9)	N2—C3—H3	115 (3)
C1—N1—H11	125 (3)	C4—C3—H3	124 (3)
C1—N1—H12	121 (3)	C3—C4—C5	118.3 (3)
H11—N1—H12	114 (4)	C3—C4—H4	117 (3)
C1—N2—C3	123.2 (3)	C5—C4—H4	124 (3)
C1—N2—H2	118 (3)	C6—C5—C4	120.9 (3)
C3—N2—H2	118 (3)	C6—C5—H5	116 (2)
N1—C1—N2	119.4 (3)	C4—C5—H5	123 (3)
N1—C1—C6	123.5 (3)	C5—C6—C1	120.0 (3)
N2—C1—C6	117.1 (3)	C5—C6—H6	121 (3)
N2—C3—C4	120.4 (3)	C1—C6—H6	118 (3)

C3—N2—C1—N1	−178.6 (3)	C3—C4—C5—C6	1.5 (6)
C3—N2—C1—C6	1.7 (5)	C4—C5—C6—C1	−1.2 (6)
C1—N2—C3—C4	−1.4 (5)	N1—C1—C6—C5	179.9 (4)
N2—C3—C4—C5	−0.3 (6)	N2—C1—C6—C5	−0.4 (5)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H11···I1	0.85 (1)	2.99 (3)	3.698 (3)	142 (4)
N1—H12···I3ⁱ	0.85 (1)	2.89 (2)	3.709 (3)	164 (4)
N2—H2···I1	0.83 (4)	2.97 (5)	3.702 (3)	147 (4)

Symmetry code: (i) x, y+1, z.

Experimental details

Crystal data
Chemical formula	C₅H₇N₂⁺·I₃⁻
M_r	475.83
Crystal system, space group	Triclinic, P1
Temperature (K)	100
a, b, c (Å)	8.0446 (4), 8.9973 (5), 9.1464 (4)
α, β, γ (°)	117.805 (6), 90.939 (4), 109.640 (5)
V (Å³)	539.46 (6)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	8.64
Crystal size (mm)	0.43 × 0.41 × 0.04

Data collection
Diffractometer	Oxford Diffraction Xcalibur Eos
Absorption correction	Analytical [CrysAlis PRO (Oxford Diffraction, 2009) based on expressions derived by Clark & Reid (1995)]
T_min, T_max	0.083, 0.698
No. of measured, independent and observed [I > 2σ(I)] reflections	5668, 2186, 2078
R_int	0.021
(sin θ/λ)_max (Å⁻¹)	0.623

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.018, 0.041, 1.01
No. of reflections	2186
No. of parameters	117
No. of restraints	2
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.99, −0.59

Computer programs: CrysAlis PRO (Oxford Diffraction, 2009), SHELXS2013 (Sheldrick, 2008), SHELXL2013 (Sheldrick, 2008), DIAMOND (Brandenburg, 2012), publCIF (Westrip, 2010).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H11···I1	0.849 (10)	2.99 (3)	3.698 (3)	142 (4)
N1—H12···I3ⁱ	0.847 (10)	2.887 (17)	3.709 (3)	164 (4)
N2—H2···I1	0.83 (4)	2.97 (5)	3.702 (3)	147 (4)

Symmetry code: (i) x, y+1, z.

Acknowledgements

We thank E. Hammes and P. Roloff for technical support and V. Breuers for useful discussions. This publication was funded by the German Research Foundation (DFG) and the Heinrich-Heine-Universität Düsseldorf under the funding programme Open Access Publishing.

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