7-Amino­heptyl­aza­nium iodide

Abstract

The absolute structure of the title compound, [H₃N-(CH₂)₇-NH₂]I, has been determined from the diffraction experiment, the Flack parameter refining to −0.02 (2). In the crystal, adjacent symmetry-related cations are connected by head-to-tail R′H₂N⁺—H⋯NH₂ R hydrogen bonds, forming chains along [010]. The remaining four H atoms attached to the amino and the aza­nium group form weak hydrogen bonds to neighbouring iodide anions, producing a three-dimensional hydrogen-bonded network. The amino group and the aliphatic chain of the 7-amino­heptyl­aza­nium cation show an exact all-trans conformation, within experimental uncertainties. The aza­nium group, to fulfill the needs of hydrogen bonding, is twisted out of the plane defined by the C atoms of the aliphatic chain, the C—C—C—N torsion angle being −65.4 (4)°.

Related literature

For the crystal structures of α-aza­niumyl-ω-amino­alkanes, see: Luciawati et al. (2011 ▶); Pienack et al. (2007 ▶); Natarajan et al. (1996 ▶); Qian et al. (2007 ▶). For α,ω-diaza­niumylalkane-containing compounds, see: Frank & Graf (2004 ▶); Jiang et al. (2010 ▶); Reiss (2010 ▶); Reiss & Engel (2002 ▶); Reiss & Engel (2004 ▶); Seidlhofer et al. (2010 ▶); Takeoka et al. (2005 ▶); Vizi et al. (2006 ▶). For dye-sensitized solar cells, see: Yang et al. (2011 ▶); Gorlov & Kloo (2008 ▶); Grätzel (2004 ▶). For graph-set analysis, see: Etter et al. (1990 ▶). For the profile fit on the powder diffraction data, see: Kraus & Nolze (2000 ▶). For background to hydrogen bonds, see: Steiner (2002 ▶).

Experimental

Crystal data

• C₇H₁₉N₂ ⁺·I⁻

• M _r = 258.14

• Monoclinic,

• a = 5.53418 (8) Å

• b = 18.7308 (3) Å

• c = 5.51570 (8) Å

• β = 95.2195 (14)°

• V = 569.39 (2) ų

• Z = 2

• Mo Kα radiation

• μ = 2.76 mm⁻¹

• T = 290 K

• 0.77 × 0.41 × 0.24 mm

Data collection

• Oxford Diffraction Xcalibur Eos diffractometer

• Absorption correction: analytical [CrysAlis PRO (Oxford Diffraction, 2009 ▶); analytical numeric absorption correction using a multifaceted crystal model based on expressions derived by Clark & Reid (1995 ▶)] T _min = 0.227, T _max = 0.543

• 31566 measured reflections

• 2331 independent reflections

• 2325 reflections with I > 2σ(I)

• R _int = 0.028

Refinement

• R[F ² > 2σ(F ²)] = 0.017

• wR(F ²) = 0.039

• S = 1.03

• 2331 reflections

• 112 parameters

• 6 restraints

• H atoms treated by a mixture of independent and constrained refinement

• Δρ_max = 0.33 e Å⁻³

• Δρ_min = −0.48 e Å⁻³

• Absolute structure: Flack (1983 ▶), 1130 Friedel pairs

• Flack parameter: −0.02 (2)

Data collection: CrysAlis PRO (Oxford Diffraction, 2009 ▶); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: DIAMOND (Brandenburg, 2010 ▶); software used to prepare material for publication: publCIF (Westrip, 2010 ▶).

Supplementary Material

Supplementary material file. DOI: 10.1107/S1600536811037329/wn2452Isup3.mol

Supplementary material file. DOI: 10.1107/S1600536811037329/wn2452Isup4.cml

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H11⋯I1	0.88 (2)	2.98 (4)	3.738 (4)	145 (5)
N1—H12⋯I1i	0.90 (2)	2.88 (3)	3.706 (3)	153 (3)
N2—H21⋯N1ii	0.90 (2)	1.87 (3)	2.740 (4)	164 (5)
N2—H22⋯I1iii	0.87 (2)	2.72 (2)	3.579 (3)	170 (3)
N2—H23⋯I1iv	0.90 (2)	2.83 (2)	3.646 (3)	152 (2)

Symmetry codes: (i) ; (ii) ; (iii) ; (iv) .

supplementary crystallographic information

Comment

There is general interest in diazanium iodides because it is well documented that they have a significant influence on the I₃^-/I^- redox system in binary ionic liquids, which are used as electrolytes for dye-sensitized solar cells (Yang et al., 2011; Gorlov & Kloo, 2008; Grätzel, 2004). Most structures reported in the α,ω-diaminoalkane/HX system are composed of α,ω-diazaniumylalkane dications and complex counteranions. Salts of α,ω-diazaniumylalkanes represent an interesting class of organic-inorganic hybride materials, with a number of different structure design examples: hydrogen-bonded frameworks as host systems for unusual species (Frank & Graf); layered materials (Takeoka et al., 2005), large-pore zeolites (Jiang et al., 2010); non-metal frameworks (e.g. Vizi et al., 2006) and metal-frameworks (Seidlhofer et al., 2010).

Our longstanding interest in the structural chemistry of α,ω-diazaniumylalkanes is focused on their versatility as templates for the synthesis of new polyiodides (Reiss & Engel, 2002; Reiss & Engel, 2004; Reiss, 2010). However, only a limited number of high-quality crystal structure determinations on α-azaniumyl-ω-aminoalkane salts have been described (Luciawati et al., 2011; Pienack et al., 2007). Furthermore, the positions of the hydrogen atoms of the hydrogen bond donating groups are not well resolved in all cases (Natarajan et al., 1996, Qian et al., 2007).

This contribution presents a rare example of a crystal structure of an α-azaniumyl-ω-aminoalkane without any disorder. The asymmetric unit of the title compound consists of one 7-aminoheptylazanium cation and one iodide anion. The bond lengths and angles within the organic cation are, with C—C bond lengths between 1.497 (5) Å to 1.517 (4) Å and slightly shorter C—N distances, 1.462 (4) Å and 1.481 (4) Å, as expected. The azanium group, to fulfill the needs of hydrogen bonding, is twisted out of the plane defined by the carbon atoms of the all-trans conformation aliphatic chain, the C5—C6—C7—N2 torsion angle being -65.4 (4)° (Fig.1 and Fig. 3)

Cations are connected to symmetry-related units by head-to-tail R'H₂N⁺—H···NH₂R hydrogen bonds. As a result of this primary connection, one-dimensional zigzag chains along [010] are formed (Fig. 1). According to a generally accepted classification (Steiner, 2002), these N⁺—H···N hydrogen bonds can be described as medium strong. Both hydrogen atoms of the amino group and two of the three hydrogen atoms of the azaniumyl group form hydrogen bonds with neighbouring iodide anions. These weak N—H···I hydrogen bonds (Table 1) connect the above-mentioned chains into a three-dimensional framework (Fig. 2 and 3). This framework can be classified by graph sets (Etter et al. 1990) as built of two smaller ring motifs [R²₄(8) and R⁴₆(12); (Fig. 2)] in the hydrophilic region of the structure and a ring motif R²₄(24) that includes the alkyl chains (Fig. 3).

Experimental

7-Aminoheptylazanium iodide, (H₃N-(CH₂)₇-NH₂)I was prepared by dissolving 1.77 mmol (0.23 mL) 1,7-diaminoheptane in 1 ml concentrated (57%) hydroiodic acid at room temperature. From this solution crystalline raw material was obtained by evaporation within a few days at room temperature. Recrystallization from fresh hydroiodic acid (57%) yielded block-shaped, almost colourless crystals.

Depending on the reaction conditions, the title compound is sometimes contaminated with a small amount of the dark-coloured α,ω-diazaniumylheptane tetraiodide, (H₃N-(CH₂)₇-NH₃)I₄ (Reiss, 2010). To verify the purity of the synthesized material, powder diffraction data of a representive part of the bulk phase were collected on a Huber G600 diffractometer (transmission, Cu Kα1, step width: 0.03°, 20 sec./step). A profile fit (Kraus & Nolze, 2000) on the powder diffraction data based on the structure model obtained from the single-crystal experiment proved the identity of the bulk phase with the investigated single-crystal (Fig. 4). This finding is supported by the Raman spectrum collected which does not show the I₄^2--specific absorption band at 175 cm^-1.

Refinement

All hydrogen atoms were located from a difference Fourier synthesis. The positional parameters of hydrogen atoms of the NH₂ and the NH₃ group were refined with soft N—H distance restraints; the final range of N—H distances is 0.87 (2) - 0.90 (2) Å. All hydrogen atoms of the CH₂ groups were refined using a riding model; C—H = 0.97 Å and U_iso(H) = 1.2U_eq(C). Anisotropic displacement parameters of all non-hydrogen atoms and individual isotropic displacement parameters for all hydrogen atoms involved in the hydrogen bonds were refined unrestrictedly. The Flack parameter refined to -0.02 (2).

Figures

Fig. 1.

The structure of the asymmetric unit, showing 50% probability displacement ellipsoids. Hydrogen atoms are shown as spheres of arbitrary radius. Symmetry-related neighbouring atoms are drawn with arbitrary radius and dashed lines indicate hydrogen bonds. Symmetry codes : ' = 2 - x, 1/2 + y, 1 - z, '' = 2 - x, 1/2 + y, 1 - z.

Fig. 2.

Hydrogen bonding ring motifs. Graph-sets: R24(8) and R46(12)) of the hydrophilic part of the structure are shown. Symmetry codes: ' = 1 - x, 1/2 + y, -z, '' = 1 - x, 1/2 + y, 1 - z.

Fig. 3.

Hydrogen bonding motif of neighboring 7-aminoheptylazanium connected by iodide anions, graph set R24(24). Symmetry codes: ' = 1 - x, 1/2 + y, 2 - z, '' = x, 1 + y, 1 + z.

Fig. 4.

Powder diffraction diagram of the title compound (black line: experimental; red line: profile fit).

Crystal data

C7H19N2+·I−	F(000) = 256
Mr = 258.14	Dx = 1.506 Mg m−3
Monoclinic, P21	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2yb	Cell parameters from 29947 reflections
a = 5.53418 (8) Å	θ = 3.3–32.6°
b = 18.7308 (3) Å	µ = 2.76 mm−1
c = 5.51570 (8) Å	T = 290 K
β = 95.2195 (14)°	Block, colourless
V = 569.39 (2) Å3	0.77 × 0.41 × 0.24 mm
Z = 2

Data collection

Oxford Diffraction Xcalibur Eos diffractometer	2331 independent reflections
Radiation source: fine-focus sealed tube	2325 reflections with I > 2σ(I)
Equatorial mounted graphite monochromator	Rint = 0.028
Detector resolution: 16.2711 pixels mm-1	θmax = 26.5°, θmin = 4.9°
ω scans	h = −6→6
Absorption correction: analytical [CrysAlis PRO (Oxford Diffraction, 2009); analytical numeric absorption correction using a multifaceted crystal model based on expressions derived by Clark & Reid (1995)]	k = −23→23
Tmin = 0.227, Tmax = 0.543	l = −6→6
31566 measured reflections

Refinement

Refinement on F2	Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full	H atoms treated by a mixture of independent and constrained refinement
R[F2 > 2σ(F2)] = 0.017	w = 1/[σ2(Fo2) + (0.010P)2 + 0.450P] where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.039	(Δ/σ)max = 0.001
S = 1.03	Δρmax = 0.33 e Å−3
2331 reflections	Δρmin = −0.48 e Å−3
112 parameters	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
6 restraints	Extinction coefficient: 0.0965 (15)
Primary atom site location: structure-invariant direct methods	Absolute structure: Flack (1983), 1130 Friedel pairs
Secondary atom site location: difference Fourier map	Flack parameter: −0.02 (2)

Special details

Experimental. The Raman spectrum was measured using a Bruker MULTIRAM spectrometer (Nd:YAG-Laser at 1064 nm; RT-InGaAs-detector); 4000–70 cm-1: 3326(w), 3259(w), 2958(m), 2896(s), 2882(s), 2850(s), 2761(w), 1590(w), 1542(w), 1479(m), 1466(m), 1445(s), 1347(w), 1304(m), 1067(m), 1039(m), 961(w), 913(w), 858(w), 838(w), 340(w), 286(w), 253(w), 109(s). IR spectroscopic data were collected on a Digilab FT3400 spectrometer using a MIRacle ATR unit (Pike Technologies); 4000–560 cm-1: 3321(m), 3258(m), 3021(m, br), 2923(s), 2853(s), 1645(m, sh), 1568(m, br), 1487(m), 1465(m), 1384(m), 1359(w), 1334(m, sh), 1302(m), 1244(w), 1156(w), 929(w, br), 817(w), 723(w).

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
I1	0.09785 (3)	0.252871 (19)	0.24986 (3)	0.06035 (9)
N1	0.4322 (6)	0.34300 (16)	0.7843 (6)	0.0548 (7)
H11	0.330 (8)	0.342 (3)	0.653 (6)	0.108 (19)*
H12	0.335 (7)	0.337 (2)	0.905 (6)	0.075 (12)*
C1	0.5909 (7)	0.40516 (19)	0.8220 (7)	0.0524 (8)
H1A	0.7136	0.3956	0.9550	0.063*
H1B	0.4962	0.4458	0.8673	0.063*
C2	0.7123 (7)	0.42306 (16)	0.5974 (7)	0.0486 (7)
H2A	0.5885	0.4340	0.4667	0.058*
H2B	0.8003	0.3814	0.5490	0.058*
C3	0.8869 (7)	0.48553 (17)	0.6285 (7)	0.0515 (8)
H3A	0.7997	0.5269	0.6806	0.062*
H3B	1.0128	0.4742	0.7567	0.062*
C4	1.0042 (7)	0.50457 (18)	0.4032 (7)	0.0527 (8)
H4A	0.8785	0.5151	0.2739	0.063*
H4B	1.0945	0.4636	0.3528	0.063*
C5	1.1744 (6)	0.56805 (17)	0.4352 (7)	0.0488 (7)
H5A	1.0862	0.6083	0.4939	0.059*
H5B	1.3049	0.5565	0.5586	0.059*
C6	1.2828 (7)	0.58973 (17)	0.2052 (7)	0.0533 (8)
H6A	1.1515	0.5989	0.0803	0.064*
H6B	1.3756	0.5498	0.1506	0.064*
C7	1.4460 (7)	0.65486 (18)	0.2270 (7)	0.0517 (8)
H7A	1.5742	0.6471	0.3563	0.062*
H7B	1.5210	0.6612	0.0763	0.062*
N2	1.3108 (5)	0.72044 (13)	0.2795 (5)	0.0463 (6)
H21	1.416 (6)	0.755 (2)	0.249 (6)	0.087 (12)*
H22	1.196 (5)	0.7290 (18)	0.164 (5)	0.066 (12)*
H23	1.253 (5)	0.7189 (16)	0.427 (4)	0.047 (8)*

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
I1	0.06054 (12)	0.07533 (14)	0.04638 (11)	−0.01293 (14)	0.01147 (7)	0.00061 (17)
N1	0.0556 (17)	0.0441 (14)	0.067 (2)	−0.0089 (14)	0.0171 (17)	0.0002 (13)
C1	0.061 (2)	0.0411 (17)	0.0565 (19)	−0.0083 (15)	0.0117 (17)	−0.0083 (14)
C2	0.0564 (19)	0.0362 (15)	0.055 (2)	−0.0084 (13)	0.0130 (16)	−0.0013 (13)
C3	0.057 (2)	0.0381 (16)	0.060 (2)	−0.0103 (14)	0.0082 (17)	−0.0036 (14)
C4	0.0567 (19)	0.0385 (15)	0.064 (2)	−0.0104 (14)	0.0097 (19)	−0.0037 (16)
C5	0.0537 (19)	0.0380 (16)	0.0556 (19)	−0.0085 (13)	0.0102 (16)	−0.0005 (13)
C6	0.062 (2)	0.0372 (16)	0.063 (2)	−0.0075 (15)	0.0138 (18)	−0.0065 (14)
C7	0.0499 (18)	0.0391 (16)	0.068 (2)	−0.0047 (14)	0.0155 (17)	−0.0021 (14)
N2	0.0582 (16)	0.0370 (11)	0.0448 (14)	0.0007 (12)	0.0106 (12)	0.0018 (10)

Geometric parameters (Å, °)

N1—C1	1.462 (4)	C4—H4B	0.9700
N1—H11	0.877 (19)	C5—C6	1.508 (5)
N1—H12	0.898 (19)	C5—H5A	0.9700
C1—C2	1.500 (5)	C5—H5B	0.9700
C1—H1A	0.9700	C6—C7	1.516 (5)
C1—H1B	0.9700	C6—H6A	0.9700
C2—C3	1.517 (4)	C6—H6B	0.9700
C2—H2A	0.9700	C7—N2	1.481 (4)
C2—H2B	0.9700	C7—H7A	0.9700
C3—C4	1.496 (5)	C7—H7B	0.9700
C3—H3A	0.9700	N2—H21	0.90 (2)
C3—H3B	0.9700	N2—H22	0.871 (18)
C4—C5	1.517 (4)	N2—H23	0.901 (18)
C4—H4A	0.9700
C1—N1—H11	118 (4)	H4A—C4—H4B	107.7
C1—N1—H12	112 (3)	C6—C5—C4	113.8 (3)
H11—N1—H12	103 (4)	C6—C5—H5A	108.8
N1—C1—C2	111.6 (3)	C4—C5—H5A	108.8
N1—C1—H1A	109.3	C6—C5—H5B	108.8
C2—C1—H1A	109.3	C4—C5—H5B	108.8
N1—C1—H1B	109.3	H5A—C5—H5B	107.7
C2—C1—H1B	109.3	C5—C6—C7	115.4 (3)
H1A—C1—H1B	108.0	C5—C6—H6A	108.4
C1—C2—C3	114.1 (3)	C7—C6—H6A	108.4
C1—C2—H2A	108.7	C5—C6—H6B	108.4
C3—C2—H2A	108.7	C7—C6—H6B	108.4
C1—C2—H2B	108.7	H6A—C6—H6B	107.5
C3—C2—H2B	108.7	N2—C7—C6	112.0 (3)
H2A—C2—H2B	107.6	N2—C7—H7A	109.2
C4—C3—C2	114.2 (3)	C6—C7—H7A	109.2
C4—C3—H3A	108.7	N2—C7—H7B	109.2
C2—C3—H3A	108.7	C6—C7—H7B	109.2
C4—C3—H3B	108.7	H7A—C7—H7B	107.9
C2—C3—H3B	108.7	C7—N2—H21	102 (3)
H3A—C3—H3B	107.6	C7—N2—H22	111 (2)
C3—C4—C5	113.7 (3)	H21—N2—H22	100 (3)
C3—C4—H4A	108.8	C7—N2—H23	112.1 (19)
C5—C4—H4A	108.8	H21—N2—H23	119 (3)
C3—C4—H4B	108.8	H22—N2—H23	112 (3)
C5—C4—H4B	108.8
N1—C1—C2—C3	−177.8 (3)	C3—C4—C5—C6	−177.0 (3)
C1—C2—C3—C4	−178.7 (3)	C4—C5—C6—C7	177.6 (3)
C2—C3—C4—C5	178.8 (3)	C5—C6—C7—N2	−65.4 (4)

Hydrogen-bond geometry (Å, °)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H11···I1	0.88 (2)	2.98 (4)	3.738 (4)	145 (5)
N1—H12···I1i	0.90 (2)	2.88 (3)	3.706 (3)	153 (3)
N2—H21···N1ii	0.90 (2)	1.87 (3)	2.740 (4)	164 (5)
N2—H22···I1iii	0.87 (2)	2.72 (2)	3.579 (3)	170 (3)
N2—H23···I1iv	0.90 (2)	2.83 (2)	3.646 (3)	152 (2)

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