Tris[2-(2-thienyl­methyl­amino)­eth­yl]ammonium triiodide

Muhammet Işıklan; Frank R Fronczek; Md Alamgir Hossain

doi:10.1107/S1600536810039462

. 2010 Oct 9;66(Pt 11):o2755. doi: 10.1107/S1600536810039462

Tris[2-(2-thienylmethylamino)ethyl]ammonium triiodide

Muhammet Işıklan ^a, Frank R Fronczek ^b, Md Alamgir Hossain ^a,^*

PMCID: PMC3009322 PMID: 21588959

Abstract

In the title compound, C₂₁H₃₃N₄S₃ ³⁺·3I⁻, three secondary amines are protonated, while the central amine remains unprotonated. One thiophene is disordered with an occupancy ratio of 0.868 (6)/0.132 (6). Each protonated amine is involved in N—H⋯I hydrogen-bonding interactions with the iodide anions.

Related literature

For general background to anion hosts, see: Bianchi et al. (1997 ▶); Kang et al. (2005 ▶); Hossain (2008 ▶); For related structures, see: Bazzicalupi et al. (2009 ▶); Hossain et al. (2002 ▶, 2004 ▶); Burgess et al. (1991 ▶); Saeed et al. (2010 ▶).

Experimental

Crystal data

C₂₁H₃₃N₄S₃ ³⁺·3I⁻
M _r = 818.42
Orthorhombic,
a = 10.5433 (5) Å
b = 11.4203 (6) Å
c = 24.5107 (15) Å
V = 2951.3 (3) Å³
Z = 4
Mo Kα radiation
μ = 3.41 mm⁻¹
T = 90 K
0.20 × 0.17 × 0.15 mm

Data collection

Nonius KappaCCD diffractometer with Oxford Cryostream
Absorption correction: multi-scan (HKL SCALEPACK; Otwinowski & Minor, 1997 ▶) T _min = 0.549, T _max = 0.629
90447 measured reflections
10653 independent reflections
9446 reflections with I > 2σ(I)
R _int = 0.069

Refinement

R[F ² > 2σ(F ²)] = 0.038
wR(F ²) = 0.093
S = 1.04
10653 reflections
277 parameters
30 restraints
H-atom parameters constrained
Δρ_max = 2.96 e Å⁻³
Δρ_min = −2.18 e Å⁻³
Absolute structure: Flack (1983 ▶), 4708 Friedel pairs
Flack parameter: 0.02 (2)

Data collection: COLLECT (Nonius, 2000 ▶); cell refinement: DENZO and SCALEPACK (Otwinowski & Minor, 1997 ▶); data reduction: DENZO and SCALEPACK; program(s) used to solve structure: SIR97 (Altomare et al., 1999 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP–3 (Farrugia, 1997 ▶); software used to prepare material for publication: SHELXL97.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536810039462/rk2235sup1.cif

e-66-o2755-sup1.cif^{(25.3KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810039462/rk2235Isup2.hkl

e-66-o2755-Isup2.hkl^{(510.4KB, hkl)}

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
N2—H21N⋯I1ⁱ	0.92	2.79	3.557 (4)	142
N2—H22N⋯I2	0.92	2.67	3.543 (4)	160
N3—H31N⋯I1	0.92	2.78	3.547 (3)	142
N3—H32N⋯I3	0.92	2.59	3.460 (3)	158
N4—H41N⋯I1	0.92	2.73	3.553 (4)	150
N4—H42N⋯I2ⁱⁱ	0.92	2.57	3.479 (4)	172

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Symmetry codes: (i) Inline graphic ; (ii) .

Acknowledgments

This work was supported by the National Institutes of Health, Division of National Center for Research Resources, under grant No. G12RR013459. This material is based upon work supported by the National Science Foundation under CHE–0821357. Purchase of the diffractometer was made possible by grant No. LEQSF (1999–2000)–ENH–TR–13, administered by the Louisiana Board of Regents.

supplementary crystallographic information

Comment

Anions play a key role in many chemical and biological processes. In particular, structural characterization of an anion complex is important in achieving selective hosts for anions (Hossain, 2008, Saeed et al., 2010). Among the numerous systems, trigonal receptors are of interest because of their synthetic simplicity and capability for anion binding though hydrogen bonding interactions. Tris(aminoethyl)–amine is an excellent building block for synthesizing fuctionalized tripodal hosts for anion binding (Burgess et al., 1991; Hossain et al., 2004; Bazzicalupi, et al., 2009). These molecules have been shown to bind a variety of anion including nitrate, phosphate and sulfate (Bianchi et al., 1997; Kang et al., 2005). Herein, we report the molecular structure of the title compound in which three iodides are held by hydrogen bonding with protonated secondary amines.

Single crystal analysis of the title compound reveals that the molecule crystallizes in its orthorhombic space group forming a cavity. The tren unit is triply charged, where all three secondary N atoms are protonated. The central amine is not protonated. The three arms form a cavity, and one thiophene unit is disordered. In the complex, the protonated amines are involved in hydrogen bonding interactions with iodide anions having N···I distances 3.460 (3) to 3.553 (4)Å (Fig. 1 and Table 1). One iodide (I1) accepts two hydrogen bonds from two protonated amines (N3 and N4), while each of the other two iodides accepts one hydrogen bond from N2 and N3. Therefore, one secondary nitrogen (N3) donates two hydrogen bonds to two iodides (I1 and I3). The N···I distances are comparable with those observed in an iodide complex of an azacryptand (3.476 (4)Å and 3.632 (4)Å) reported earlier (Hossain et al., 2002).

The disorder of the thiophene ring containing S3 involves two conformations, differing by rotation about two different bonds. One is a twofold rotation about C17—C18, which swaps S3 and C19. Refinement of this type of model resulted in elongated ellipsoids in the plane of the ring for all atoms of the thiophene, as well as unacceptable residual densities. This was interpreted as a second conformational difference involving a difference in rotation about the N4—C17 bond, amounting to a torsional difference of 11.7°.

Experimental

To a solution of 2–thiophene aldehyde (4.60 g, 41 mmol) in diethylether (50 ml) was added tris(2–aminoethyl)amine (2.00 g, 13.7 mmol) in ethanol (50 ml). The mixture was stirred overnight at room temperature, and the solvent was evaporated. After diluting with methanol (100 ml), NaBH₄ (2.00 g) was added to convert the imine into the corresponding amine. The reaction mixture was stirred for 24 hrs at room temperature. After evaporation of the solvent, the residue was partitioned in water/CH₂Cl₂ (50/50 ml). The organic layers were collected and dried with MgSO₄ to give an oily product. Yield 4.38 g (74%). ¹H NMR (500 MHz, CDCl₃, TMS): δ 2.58 (t, 6H, NCH₂), 2.69 ((t, 6H, NCH₂CH₂), 3.95 (s, 6H, ArCH₂)), 6.89 (b, 3H, ArH), 6.93 (b, ArH), 7.18 (b, ArH). MS (ESI): m/z (+) 435 (M + H)⁺. The iodide salt was prepared from the reaction of the free amine (0.20 g, 0.47 mmol) with HI in ethanol. The white precipitate was obtained after evaporation of the solvent. The salt was redissolved in water and ethanol (1:2 v/v, 1 ml) and crystals suitable for X–ray analysis were grown from slow evaporation of the solvent at room temperature.