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Acta Cryst. (2010). E66, o392    [ doi:10.1107/S1600536809054701 ]

2,2'-(Propane-2,2-diyl)bis(1H-pyrrole)

G. Journot, R. Neier and H. Stoeckli-Evans

Abstract top

The title compound, C11H14N2, crystallized with two independent molecules (A and B) in the asymmetric unit. The two molecules differ only slightly, with the pyrrole rings being inclined to one another at a dihedral angle of 87.67 (8)° in molecule A and 88.09 (7)° in molecule B. In the crystal, there are no classical hydrogen bonds, but the two pyrrole NH groups of one molecule are involved in N-H...[pi] interactions with the pyrrole rings of the other molecule. In this manner, a compact box-like arrangement of the two independent molecules is formed.

Comment top

The title compound was prepared as a building block for the formation of substituted calix[4]pyrroles. The latter have been shown to form extremely interesting host–guest complexes with various anions (Gale et al., 1998; Sessler & Davis, 2001; Sessler et al., 2003).

The structure of the title compound is shown in Fig. 1, and the geometrical parameters are given in the Supplementary Information and the archived CIF. The compound crystallized in the centrosymmetric triclinic space group P1 with two independent molecules (A and B) in the asymmetric unit. The bond lengths and angles are similar to those observed in the diethyl analogue (Sobral et al., 2003), which also crystallized with two independent molecules, but in the non-centrosymetric monoclinic space group C2.

In the title compound the quateranry centers, C9 in A and C29 in B, impose a twist to the molecules with the pyrrole ring mean-planes being almost perpendicular to one another; 87.67 (8) ° in molecule A and 88.09 (7)° in molecule B. This is similar to the situation in the diethyl analogue where the two dihedral angles are 86.5 (2) and 86.7 (2) °.

N—H···π interactions are extremely important in biological systems and this aspect as been reviewed by (Meyer et al., 2003). The spectroscopic aspects of the N—H···π interactions of the pyrrole dimer have also been studied recently by (Dauster et al., 2008). In the crystal of the title compound the two independent molecules are linked by N—H···π interactions involving the pyrrole NH H-atoms of molecule A with the pyrrole rings of molecule B, and visa-versa (Table 1). This leads to the formation of a compact box-like arrangement of the two molecules, as shown in Fig. 2. Again this arrangement is similar to that observed in the crystal of the diethyl analogue.

Related literature top

For substituted calix[4]pyrroles, see: Gale et al. (1998); Sessler & Davis (2001); Sessler et al. (2003). For the synthesis and crystal structure of meso-diethyl-bis(2-pyrrolyl)methane, see: Sobral et al. (2003). For intermolecular interactions involving aromatic rings in biological systems, see: Meyer et al. (2003). For a spectroscopic analysis of N—H···π interactions in pyrroles, see: Dauster et al. (2008).

Experimental top

A mixture of acetone (4.21 ml, 57.4 mmol) and pyrrole (31.72 ml, 0.459 mol, 8 equiv.) were stirred for 5 min and then trifluoroactetic acid (TFA: 0.44 ml, 2.53 mmol, 0.1 equiv) was added. The mixture stirred for an additional 5 min and then quenched with aqueous NaOH (0.1 N, 30 ml). It was then extracted with CH2Cl2 (50 ml × 2) and the organic layer dried (Na2SO4). The solvent was removed in vacuo and the remaining oil (82% pure in GC) was purified by flash chromatography on silica (eluent: cyclohexane/ethyl acetate; v:v = 4:1) to give colourless block-like crystals of the title compound (yield 6.8 g, 68%). 1H NMR (CDCl3): δ 7.72 (bs, 2H, N—H), 6.62–6.60 (m, 2H, pyrrolic-H1), 6.15–6.13 (m, 2H, pyrrolic-H2), 6.11–6.09 (m, 2H, pyrrolic-H3), 1.59 (s, 6H, –CH3); 13CNMR (CDCl3): δ 139.24 (C4), 117.19 (C1), 107.91 (C2), 103.87 (C3), 35.52(C5), 29.46 (C6).

Refinement top

The NH H-atoms were located in a difference electron-density map and were freely refined: N—H = 0.86 (2)–0.88 (2) Å. The C-bound H-atoms were included in calculated positions and treated as riding atoms: C—H = 0.95 and 0.99 Å for CH and CH3 H-atoms, respectively, with Uiso(H) = k × Ueq(C), where k = 1.2 for CH H-atoms, and 1.5 for CH3 H-atoms.

Computing details top

Data collection: X-AREA (Stoe & Cie, 2009); cell refinement: X-AREA (Stoe & Cie, 2009); data reduction: X-RED32 (Stoe & Cie, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997) and Mercury (Macrae et al., 2006); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008) and PLATON (Spek, 2009).

Figures top
[Figure 1] Fig. 1. A view of the molecular structure of the two independent molecules (A and B) of the title compound, with the displacement ellipsoids drawn at the 50% probability level.
[Figure 2] Fig. 2. A view, along the a axis, of the crystal packing of the title compound. The N—H···π interactions are shown as dotted black lines for one of the box-like arrangements of the two independent molecules (see Table 1 for details; C-bound H-atoms have been omitted for clarity).
2,2'-(propane-2,2-diyl)bis(1H-pyrrole) top
Crystal data top
C11H14N2Z = 4
Mr = 174.24F(000) = 376
Triclinic, P1Dx = 1.159 Mg m−3
Hall symbol: -P 1Mo Kα radiation, λ = 0.71073 Å
a = 8.4554 (8) ÅCell parameters from 10442 reflections
b = 9.2001 (8) Åθ = 1.6–29.5°
c = 13.2274 (11) ŵ = 0.07 mm−1
α = 99.802 (7)°T = 173 K
β = 95.321 (7)°Block, colourless
γ = 97.328 (7)°0.40 × 0.34 × 0.28 mm
V = 998.74 (15) Å3
Data collection top
Stoe IPDS-2
diffractometer		3816 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.046
graphiteθmax = 29.2°, θmin = 1.6°
φ and ω scansh = −11→11
15270 measured reflectionsk = −12→12
5385 independent reflectionsl = −18→18
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.045Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.106H atoms treated by a mixture of independent and constrained refinement
S = 1.02 w = 1/[σ2(Fo2) + (0.0549P)2 + 0.0012P]
where P = (Fo2 + 2Fc2)/3
5385 reflections(Δ/σ)max < 0.001
255 parametersΔρmax = 0.25 e Å−3
0 restraintsΔρmin = −0.21 e Å−3
Crystal data top
C11H14N2γ = 97.328 (7)°
Mr = 174.24V = 998.74 (15) Å3
Triclinic, P1Z = 4
a = 8.4554 (8) ÅMo Kα radiation
b = 9.2001 (8) ŵ = 0.07 mm−1
c = 13.2274 (11) ÅT = 173 K
α = 99.802 (7)°0.40 × 0.34 × 0.28 mm
β = 95.321 (7)°
Data collection top
Stoe IPDS-2
diffractometer		3816 reflections with I > 2σ(I)
15270 measured reflectionsRint = 0.046
5385 independent reflectionsθmax = 29.2°
Refinement top
R[F2 > 2σ(F2)] = 0.045H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.106Δρmax = 0.25 e Å−3
S = 1.02Δρmin = −0.21 e Å−3
5385 reflectionsAbsolute structure: ?
255 parametersFlack parameter: ?
0 restraintsRogers parameter: ?
Special details top

Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles

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 (Å2) top
xyzUiso*/Ueq
N10.12135 (12)0.25140 (11)0.31284 (8)0.0249 (3)
N20.40689 (12)0.01811 (11)0.24234 (8)0.0252 (3)
C10.13663 (14)0.38021 (14)0.38492 (10)0.0312 (4)
C20.17507 (15)0.34619 (16)0.47962 (10)0.0348 (4)
C30.18351 (15)0.19174 (16)0.46471 (9)0.0311 (4)
C40.14934 (13)0.13454 (13)0.36055 (9)0.0234 (3)
C50.24635 (14)−0.03734 (12)0.22005 (9)0.0226 (3)
C60.22365 (16)−0.10944 (14)0.11865 (9)0.0305 (4)
C70.37369 (18)−0.09563 (15)0.07953 (10)0.0358 (4)
C80.48462 (16)−0.01599 (14)0.15732 (10)0.0314 (4)
C90.13255 (15)−0.02364 (14)0.30167 (9)0.0277 (3)
C10−0.04155 (17)−0.07156 (17)0.24923 (13)0.0470 (5)
C110.1699 (2)−0.12827 (17)0.37732 (13)0.0479 (5)
N210.51399 (12)0.37264 (11)0.36601 (7)0.0232 (3)
N220.32603 (13)0.28069 (11)0.11006 (7)0.0253 (3)
C210.59997 (14)0.28840 (14)0.42014 (9)0.0264 (3)
C220.73108 (15)0.26137 (15)0.37047 (10)0.0308 (4)
C230.72320 (14)0.33192 (14)0.28313 (9)0.0281 (4)
C240.58798 (13)0.40056 (13)0.28184 (8)0.0225 (3)
C250.35755 (14)0.42785 (13)0.15697 (8)0.0229 (3)
C260.21946 (16)0.48825 (14)0.13876 (9)0.0298 (4)
C270.10133 (16)0.37382 (15)0.07998 (10)0.0340 (4)
C280.17016 (15)0.24721 (14)0.06366 (9)0.0307 (3)
C290.52308 (14)0.49773 (13)0.21071 (9)0.0251 (3)
C300.51173 (19)0.65164 (14)0.27414 (11)0.0381 (4)
C310.63878 (17)0.51784 (17)0.12898 (10)0.0381 (4)
H1N0.1032 (19)0.2477 (18)0.2475 (13)0.040 (4)*
H2N0.4531 (19)0.0726 (18)0.2990 (12)0.040 (4)*
H10.122800.476200.371200.0370*
H20.192900.413800.543800.0420*
H30.208400.136900.517300.0370*
H60.12470−0.159600.081500.0370*
H70.39370−0.134700.011400.0430*
H80.595800.010800.153100.0380*
H10A−0.11590−0.063400.301800.0710*
H10B−0.05400−0.175100.212600.0710*
H10C−0.06530−0.006600.200000.0710*
H11A0.09550−0.121800.430000.0720*
H11B0.28040−0.098500.410700.0720*
H11C0.15750−0.231000.339400.0720*
H21N0.4231 (19)0.4002 (16)0.3827 (11)0.031 (4)*
H22N0.3894 (19)0.2146 (18)0.1123 (11)0.039 (4)*
H210.573300.254700.481300.0320*
H220.812100.205900.390700.0370*
H230.798400.331800.234000.0340*
H260.205400.588900.161500.0360*
H27−0.005700.383800.056500.0410*
H280.119500.152500.026700.0370*
H30A0.471700.715200.228100.0570*
H30B0.618300.697700.308700.0570*
H30C0.437900.640100.326100.0570*
H31A0.643700.420700.086400.0570*
H31B0.746200.560900.163600.0570*
H31C0.600000.584700.085100.0570*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0216 (5)0.0271 (5)0.0262 (5)0.0050 (4)0.0023 (4)0.0045 (4)
N20.0249 (5)0.0242 (5)0.0266 (5)0.0033 (4)0.0039 (4)0.0051 (4)
C10.0204 (6)0.0265 (6)0.0442 (7)0.0037 (5)0.0068 (5)−0.0019 (5)
C20.0263 (6)0.0400 (7)0.0321 (6)−0.0005 (5)0.0080 (5)−0.0090 (5)
C30.0269 (6)0.0430 (8)0.0231 (6)0.0032 (5)0.0050 (4)0.0058 (5)
C40.0187 (5)0.0285 (6)0.0244 (5)0.0045 (4)0.0055 (4)0.0068 (4)
C50.0244 (5)0.0184 (5)0.0258 (5)0.0029 (4)0.0035 (4)0.0059 (4)
C60.0395 (7)0.0234 (6)0.0267 (6)0.0030 (5)0.0002 (5)0.0024 (5)
C70.0553 (9)0.0276 (7)0.0283 (6)0.0115 (6)0.0169 (6)0.0051 (5)
C80.0332 (7)0.0269 (6)0.0402 (7)0.0104 (5)0.0174 (5)0.0116 (5)
C90.0270 (6)0.0264 (6)0.0312 (6)0.0027 (5)0.0094 (5)0.0071 (5)
C100.0282 (7)0.0395 (8)0.0639 (10)−0.0074 (6)0.0111 (6)−0.0107 (7)
C110.0672 (11)0.0390 (8)0.0518 (9)0.0195 (7)0.0325 (8)0.0256 (7)
N210.0186 (5)0.0288 (5)0.0227 (5)0.0038 (4)0.0016 (4)0.0060 (4)
N220.0289 (5)0.0225 (5)0.0239 (5)0.0058 (4)−0.0029 (4)0.0043 (4)
C210.0248 (6)0.0302 (6)0.0236 (5)0.0013 (5)−0.0040 (4)0.0087 (5)
C220.0238 (6)0.0332 (7)0.0360 (7)0.0079 (5)−0.0029 (5)0.0085 (5)
C230.0211 (6)0.0336 (7)0.0292 (6)0.0037 (5)0.0037 (4)0.0047 (5)
C240.0211 (5)0.0237 (6)0.0209 (5)0.0000 (4)−0.0003 (4)0.0034 (4)
C250.0283 (6)0.0221 (6)0.0186 (5)0.0039 (4)0.0003 (4)0.0055 (4)
C260.0349 (7)0.0250 (6)0.0308 (6)0.0094 (5)−0.0012 (5)0.0074 (5)
C270.0289 (6)0.0382 (7)0.0347 (7)0.0056 (5)−0.0074 (5)0.0115 (6)
C280.0317 (6)0.0303 (6)0.0267 (6)−0.0010 (5)−0.0080 (5)0.0063 (5)
C290.0275 (6)0.0242 (6)0.0223 (5)0.0002 (4)−0.0014 (4)0.0057 (4)
C300.0508 (8)0.0234 (6)0.0354 (7)0.0030 (6)−0.0115 (6)0.0029 (5)
C310.0351 (7)0.0476 (8)0.0315 (6)−0.0054 (6)0.0023 (5)0.0163 (6)
Geometric parameters (Å, °) top
N1—C11.3724 (17)C10—H10C0.9800
N1—C41.3705 (16)C10—H10B0.9800
N2—C51.3739 (16)C10—H10A0.9800
N2—C81.3655 (17)C11—H11B0.9800
N1—H1N0.858 (17)C11—H11A0.9800
N2—H2N0.856 (16)C11—H11C0.9800
N21—C211.3704 (16)C21—C221.3683 (18)
N21—C241.3720 (14)C22—C231.4186 (18)
N22—C251.3712 (15)C23—C241.3750 (17)
N22—C281.3750 (17)C24—C291.5170 (16)
N21—H21N0.875 (16)C25—C291.5192 (17)
N22—H22N0.863 (16)C25—C261.3744 (18)
C1—C21.3626 (19)C26—C271.4211 (19)
C2—C31.413 (2)C27—C281.3612 (19)
C3—C41.3781 (17)C29—C311.5421 (18)
C4—C91.5118 (17)C29—C301.5373 (18)
C5—C61.3757 (17)C21—H210.9500
C5—C91.5115 (17)C22—H220.9500
C6—C71.413 (2)C23—H230.9500
C7—C81.3654 (19)C26—H260.9500
C9—C111.541 (2)C27—H270.9500
C9—C101.544 (2)C28—H280.9500
C1—H10.9500C30—H30A0.9800
C2—H20.9500C30—H30B0.9800
C3—H30.9500C30—H30C0.9800
C6—H60.9500C31—H31A0.9800
C7—H70.9500C31—H31B0.9800
C8—H80.9500C31—H31C0.9800
C1—N1—C4109.93 (10)C9—C11—H11C109.00
C5—N2—C8110.24 (10)H11A—C11—H11B109.00
C1—N1—H1N123.9 (11)H11A—C11—H11C109.00
C4—N1—H1N126.1 (11)H11B—C11—H11C109.00
C5—N2—H2N126.5 (11)C9—C11—H11B109.00
C8—N2—H2N123.1 (11)C9—C11—H11A109.00
C21—N21—C24110.16 (10)N21—C21—C22107.86 (11)
C25—N22—C28110.04 (10)C21—C22—C23107.02 (11)
C21—N21—H21N123.5 (9)C22—C23—C24108.20 (11)
C24—N21—H21N126.3 (9)C23—C24—C29131.63 (10)
C28—N22—H22N123.0 (11)N21—C24—C23106.75 (10)
C25—N22—H22N126.8 (11)N21—C24—C29121.55 (10)
N1—C1—C2107.93 (12)N22—C25—C29121.59 (11)
C1—C2—C3107.31 (12)C26—C25—C29131.53 (11)
C2—C3—C4108.08 (11)N22—C25—C26106.79 (10)
C3—C4—C9130.99 (12)C25—C26—C27108.09 (11)
N1—C4—C9122.17 (10)C26—C27—C28107.19 (12)
N1—C4—C3106.75 (11)N22—C28—C27107.89 (11)
N2—C5—C6106.70 (11)C25—C29—C31109.40 (10)
C6—C5—C9131.40 (11)C30—C29—C31108.82 (11)
N2—C5—C9121.74 (10)C25—C29—C30109.04 (10)
C5—C6—C7107.85 (11)C24—C29—C25110.94 (10)
C6—C7—C8107.59 (12)C24—C29—C30109.35 (10)
N2—C8—C7107.61 (12)C24—C29—C31109.26 (10)
C4—C9—C5111.44 (10)N21—C21—H21126.00
C10—C9—C11109.12 (12)C22—C21—H21126.00
C5—C9—C10109.09 (10)C21—C22—H22126.00
C5—C9—C11108.66 (11)C23—C22—H22127.00
C4—C9—C10109.10 (11)C22—C23—H23126.00
C4—C9—C11109.41 (10)C24—C23—H23126.00
N1—C1—H1126.00C25—C26—H26126.00
C2—C1—H1126.00C27—C26—H26126.00
C3—C2—H2126.00C26—C27—H27126.00
C1—C2—H2126.00C28—C27—H27126.00
C4—C3—H3126.00N22—C28—H28126.00
C2—C3—H3126.00C27—C28—H28126.00
C7—C6—H6126.00C29—C30—H30A109.00
C5—C6—H6126.00C29—C30—H30B109.00
C6—C7—H7126.00C29—C30—H30C109.00
C8—C7—H7126.00H30A—C30—H30B110.00
N2—C8—H8126.00H30A—C30—H30C109.00
C7—C8—H8126.00H30B—C30—H30C109.00
C9—C10—H10A109.00C29—C31—H31A109.00
C9—C10—H10B109.00C29—C31—H31B109.00
C9—C10—H10C109.00C29—C31—H31C109.00
H10B—C10—H10C110.00H31A—C31—H31B109.00
H10A—C10—H10C109.00H31A—C31—H31C110.00
H10A—C10—H10B109.00H31B—C31—H31C109.00
C4—N1—C1—C20.14 (14)N2—C5—C9—C10170.37 (11)
C1—N1—C4—C3−0.25 (13)N2—C5—C9—C11−70.77 (14)
C1—N1—C4—C9176.69 (11)C6—C5—C9—C10−14.94 (19)
C8—N2—C5—C60.67 (14)C6—C5—C9—C11103.92 (15)
C8—N2—C5—C9176.51 (11)C5—C6—C7—C80.07 (16)
C5—N2—C8—C7−0.63 (14)C6—C7—C8—N20.34 (15)
C21—N21—C24—C29−177.09 (10)N21—C21—C22—C23−0.10 (15)
C24—N21—C21—C22−0.03 (13)C21—C22—C23—C240.19 (15)
C21—N21—C24—C230.15 (13)C22—C23—C24—N21−0.21 (14)
C28—N22—C25—C26−0.63 (13)C22—C23—C24—C29176.64 (12)
C28—N22—C25—C29−177.43 (10)N21—C24—C29—C25−63.67 (14)
C25—N22—C28—C270.54 (14)N21—C24—C29—C3056.63 (15)
N1—C1—C2—C30.02 (14)N21—C24—C29—C31175.64 (11)
C1—C2—C3—C4−0.17 (15)C23—C24—C29—C25119.88 (14)
C2—C3—C4—C9−176.31 (12)C23—C24—C29—C30−119.82 (14)
C2—C3—C4—N10.25 (14)C23—C24—C29—C31−0.82 (18)
N1—C4—C9—C560.57 (15)N22—C25—C26—C270.48 (13)
N1—C4—C9—C11−179.26 (11)C29—C25—C26—C27176.83 (12)
C3—C4—C9—C5−123.33 (14)N22—C25—C29—C24−47.82 (14)
N1—C4—C9—C10−59.95 (15)N22—C25—C29—C30−168.30 (10)
C3—C4—C9—C11−3.15 (19)N22—C25—C29—C3172.79 (14)
C3—C4—C9—C10116.16 (15)C26—C25—C29—C24136.28 (13)
N2—C5—C9—C449.85 (15)C26—C25—C29—C3015.80 (17)
C9—C5—C6—C7−175.73 (12)C26—C25—C29—C31−103.11 (15)
N2—C5—C6—C7−0.44 (14)C25—C26—C27—C28−0.16 (14)
C6—C5—C9—C4−135.46 (13)C26—C27—C28—N22−0.23 (14)
Table 1
Geometry of N—H···π interactions (Å, °) top
DHCentroidN—HH···CgD···CgN—H···Cg
N1H1NCg40.86 (2)2.534 (17)3.2190 (12)137.4 (14)
N2H2NCg30.86 (2)2.591 (17)3.2425 (12)133.7 (13)
N21H21NCg10.88 (2)2.523 (16)3.1925 (12)133.9 (12)
N22H22NCg20.86 (2)2.610 (17)3.2440 (12)131.3 (13)
Cg1, Cg2, Cg3 and Cg4 are the centroids of the N1/C1–C4, N2/C5–C8, N21/C21-C24 and N22/C25–C28 rings, respectively.
Acknowledgements top

HSE is grateful to the XRD Application LAB, Microsystems Technology Division, Swiss Center for Electronics and Microtechnology, Neuchâtel, for access to the X-ray diffraction equipment.

references
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