organic compounds
Tris{2-[(2-aminobenzylidene)amino]ethyl}amine
aLaboratorio de Química Industrial, CELAES, Facultad de Ciencias Químicas, UANL, Pedro de Alba s/n, 66451 San Nicolás de los Garza, NL, Mexico, and bDEP Facultad de Ciencias Químicas, UANL, Guerrero y Progreso S/N, Col. Treviño, 64570 Monterrey, NL, Mexico
*Correspondence e-mail: sylvain_bernes@hotmail.com
The title Schiff base, C27H33N7, is a tripodal amine displaying C3 symmetry, with the central tertiary N atom lying on the threefold crystallographic axis. The N—CH2—CH2—N conformation of the pendant arms is gauche [torsion angle = 76.1 (3)°], which results in a claw-like molecule, with the terminal aniline groups wrapped around the symmetry axis. The lone pair of the apical N atom is clearly oriented inwards towards the cavity, and should thus be chemically inactive. The amine NH2 substituents lie in the plane of the benzene ring to which they are bonded. With such an arrangement, one amine H atom forms an S(6) motif through a weak N—H⋯N hydrogen bond with the imine N atom, while the other is engaged in an intermolecular N—H⋯π contact involving the benzene ring of a neighbouring molecule related by inversion. The benzene rings also participate in an intramolecular C—H⋯π contact of similar strength. In the molecules are separated by empty voids (ca 5% of the crystal volume), although the crystal seems to be unsolvated.
Related literature
For applications of polyamines as metal extractants, see: Wenzel (2008); Bernier et al. (2009); Galbraith et al. (2006). For other applications, see: Zibaseresht & Hartshorn (2005); Mercs et al. (2008). For similar C3 tripodal structures, see: Weibel et al. (2002); Işıklan et al. (2010); McKee et al. (2006); Glidewell et al. (2005). The software used for analysis of the empty voids in the was SQUEEZE in PLATON (Spek, 2009).
Experimental
Crystal data
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Data collection
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Refinement
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Data collection: XSCANS (Siemens, 1996); cell XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: Mercury (Macrae et al., 2006); software used to prepare material for publication: SHELXL97.
Supporting information
https://doi.org/10.1107/S1600536810043783/bq2243sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536810043783/bq2243Isup2.hkl
To a dissolution of 2-nitrobenzaldehyde (0.020 mol) in ethanol (60 ml), were added 11.114 g (0.20 mol) of iron, 90 µl of hydrochloric acid and 15 ml of distilled water. Immediately the mixture was refluxed for 90 min. The mixture was filtered off using Hyfo νas and νs), 1635 (C═N δs), 1588 (NH δs), 749 cm-1 (NH δs). 1H NMR (200 MHz, CDCl3): δ, p.p.m.: 2.92 (6H, t, H2C—N), 3.69 (6H, t, H2C═N), 6.34 (6H, s, H2NAr), 6.62 (6H, c, Ar), 6.88 (3H, dd, Ar), 7.12 (3H, td, Ar), 8.17 (3H, s, Ar).
and the solvent was distilled, affording a yellow oil (Fig. 1, IL). In order to obtain the title molecule (I), a dissolution of 2.414 g of IL in 20 ml of methanol and 1060 µl of tris(2-aminoethyl)amine (TREN) were stirred at room temperature for 30 min, affording a yellow solid, (I), which was filtered off and recrystallized from acetonitrile. Suitable crystals were obtained as pale-yellow blocks by slow evaporation of an acetone solution at 298 K. m.p. 416–417 K; analysis found (calc. for C27H33N7): C 71.02 (71.18%), H 7.82 (7.30%), N 22.40 (21.52%); IR RTA: 3437, 3237 (NHAmine H atoms H12A and H12B were found in a difference map and refined with free coordinates. Other H atoms were placed in idealized positions and refined as riding to their parent C atoms, with bond lengths fixed to 0.97 (methylene) or 0.93 Å (aromatic). Isotropic displacement parameters for H atoms were calculated as Uiso(H) = 1.2Ueq(carrier atom). A set of 21 reflections with Fo << Fc (probably because of a diffractometer instability) were omitted in least-squares refinement.
Recently, the research line of receptors with the ability to extract metal salts has grown in relevance, because of the harmful effects that anions and cations have in health and the environment. A class of such receptors includes polyamines, in which cations and anions are found in separate sites in a zwitterionic form of the ligand. As a consequence, the efficiency for
of metal salts may be modulated trough pH adjustment (Wenzel, 2008). In these compounds, the metal ion coordinates in the deprotonated moiety, while the anion is associated to the protonated pendant groups (Bernier et al., 2009; Galbraith et al., 2006). The Schiff base condensation is a useful route to obtain polyamines including suitable structural characteristics in order to act as polytopic ligands. Some recent reports highlighted important applications of this type of compounds (Zibaseresht & Hartshorn, 2005; Mercs et al., 2008).We report herein on the synthesis (Fig. 1) and π contact, also of limited strength. The last significant contact is intramolecular: the C7—H7 aromatic group gives a C—H···π contact with the next arm in the molecule.
of a new Schiff base, which, we hope, will allow to bond both cations and anions, depending on the pH. The molecule (Fig. 2) is a tripodal tertiary amine NR3 where R contains imine functionality. The tripodal N atom is placed on a 3-fold axis in a trigonal cell (C3 point symmetry). The pendant arms R are gauche, as reflected by torsion angle N1—C2—C3—N4, 76.1 (3)°, and the lone pair on N1 is directed toward the cavity formed by the arms. Similar arrangements giving claw-like molecules were observed in related tertiary although in less symmetric Laue groups (e.g. Weibel et al., 2002; Işıklan et al., 2010). In some instances, closely related tripodal NR3 molecules approximate the C3 symmetry but with R arms lying in a plane rather than forming a closed cavity (McKee et al., 2006). Glidewell et al. (2005) showed that the for this class of is determined mainly by direction-specific intra- and intermolecular interactions. In the case of the title amine, NH2 groups in the aniline moieties are engaged in both intra and intermolecular interactions: H12A forms a weak hydrogen bond with the imine atom N4, while H12B affords an intermolecular N—H···As mentioned, all non bonding contacts are rather weak. As a consequence, molecules are not densely packed in the crystal, and voids of ca 60 Å3 are available for solvent insertion. However, attempts to include non-diffracting solvent in the structural model using SQUEEZE (Spek, 2009) were unsuccessful. The chemical formula was thus left as unsolvated.
For applications of polyamines as metal extractants, see: Wenzel (2008); Bernier et al. (2009); Galbraith et al. (2006). For other applications, see: Zibaseresht & Hartshorn (2005); Mercs et al. (2008). For similar C3 tripodal structures, see: Weibel et al. (2002); Işıklan et al. (2010); McKee et al. (2006); Glidewell et al. (2005). The software used for analysis of the empty voids in the
was SQUEEZE in PLATON (Spek, 2009).Data collection: XSCANS (Siemens, 1996); cell
XSCANS (Siemens, 1996); data reduction: XSCANS (Siemens, 1996); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: Mercury (Macrae et al., 2006); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).C27H33N7 | Dx = 1.174 Mg m−3 |
Mr = 455.60 | Melting point: 416 K |
Trigonal, R3 | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -R 3 | Cell parameters from 70 reflections |
a = 13.1075 (18) Å | θ = 4.8–12.3° |
c = 25.985 (6) Å | µ = 0.07 mm−1 |
V = 3866.3 (12) Å3 | T = 300 K |
Z = 6 | Prism, yellow |
F(000) = 1464 | 0.40 × 0.40 × 0.18 mm |
Siemens P4 diffractometer | Rint = 0.033 |
Radiation source: fine-focus sealed tube | θmax = 25.0°, θmin = 2.0° |
Graphite monochromator | h = −13→15 |
ω scans | k = −15→15 |
6668 measured reflections | l = −30→30 |
1507 independent reflections | 2 standard reflections every 98 reflections |
838 reflections with I > 2σ(I) | intensity decay: 2% |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.058 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.176 | w = 1/[σ2(Fo2) + (0.05P)2] where P = (Fo2 + 2Fc2)/3 |
S = 1.81 | (Δ/σ)max < 0.001 |
1507 reflections | Δρmax = 0.51 e Å−3 |
110 parameters | Δρmin = −0.21 e Å−3 |
0 restraints | Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
0 constraints | Extinction coefficient: 0.0057 (9) |
Primary atom site location: structure-invariant direct methods |
C27H33N7 | Z = 6 |
Mr = 455.60 | Mo Kα radiation |
Trigonal, R3 | µ = 0.07 mm−1 |
a = 13.1075 (18) Å | T = 300 K |
c = 25.985 (6) Å | 0.40 × 0.40 × 0.18 mm |
V = 3866.3 (12) Å3 |
Siemens P4 diffractometer | Rint = 0.033 |
6668 measured reflections | 2 standard reflections every 98 reflections |
1507 independent reflections | intensity decay: 2% |
838 reflections with I > 2σ(I) |
R[F2 > 2σ(F2)] = 0.058 | 0 restraints |
wR(F2) = 0.176 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.81 | Δρmax = 0.51 e Å−3 |
1507 reflections | Δρmin = −0.21 e Å−3 |
110 parameters |
x | y | z | Uiso*/Ueq | ||
N1 | 1.0000 | 1.0000 | 0.17108 (11) | 0.0773 (10) | |
C2 | 0.9753 (3) | 0.8840 (2) | 0.15415 (9) | 0.0952 (9) | |
H2A | 1.0068 | 0.8904 | 0.1198 | 0.114* | |
H2B | 0.8906 | 0.8322 | 0.1524 | 0.114* | |
C3 | 1.0266 (3) | 0.8305 (3) | 0.18909 (10) | 0.0990 (10) | |
H3A | 1.0287 | 0.7663 | 0.1714 | 0.119* | |
H3B | 1.1069 | 0.8892 | 0.1978 | 0.119* | |
N4 | 0.95737 (19) | 0.78635 (19) | 0.23590 (8) | 0.0821 (7) | |
C5 | 1.0077 (2) | 0.8295 (2) | 0.27831 (10) | 0.0741 (7) | |
H5A | 1.0862 | 0.8891 | 0.2776 | 0.089* | |
C6 | 0.9507 (2) | 0.79175 (19) | 0.32820 (9) | 0.0680 (7) | |
C7 | 1.0149 (2) | 0.8459 (2) | 0.37218 (10) | 0.0825 (8) | |
H7A | 1.0933 | 0.9045 | 0.3688 | 0.099* | |
C8 | 0.9669 (3) | 0.8163 (3) | 0.42032 (11) | 0.0985 (9) | |
H8A | 1.0120 | 0.8540 | 0.4492 | 0.118* | |
C9 | 0.8505 (3) | 0.7297 (3) | 0.42536 (10) | 0.0915 (9) | |
H9A | 0.8165 | 0.7096 | 0.4579 | 0.110* | |
C10 | 0.7853 (3) | 0.6738 (2) | 0.38354 (10) | 0.0820 (8) | |
H10A | 0.7073 | 0.6147 | 0.3879 | 0.098* | |
C11 | 0.8319 (2) | 0.7026 (2) | 0.33419 (9) | 0.0696 (7) | |
N12 | 0.7651 (2) | 0.6450 (2) | 0.29267 (9) | 0.0958 (8) | |
H12A | 0.792 (3) | 0.670 (3) | 0.2599 (10) | 0.115* | |
H12B | 0.692 (3) | 0.597 (3) | 0.2993 (11) | 0.115* |
U11 | U22 | U33 | U12 | U13 | U23 | |
N1 | 0.0863 (15) | 0.0863 (15) | 0.0592 (18) | 0.0432 (8) | 0.000 | 0.000 |
C2 | 0.116 (2) | 0.101 (2) | 0.0686 (14) | 0.0545 (18) | 0.0064 (14) | −0.0093 (14) |
C3 | 0.118 (2) | 0.098 (2) | 0.0928 (18) | 0.0631 (19) | 0.0324 (16) | 0.0059 (15) |
N4 | 0.0836 (15) | 0.0817 (14) | 0.0848 (14) | 0.0442 (12) | 0.0142 (12) | 0.0027 (11) |
C5 | 0.0668 (15) | 0.0620 (14) | 0.0941 (17) | 0.0327 (12) | 0.0095 (13) | 0.0063 (13) |
C6 | 0.0648 (15) | 0.0560 (13) | 0.0840 (16) | 0.0307 (12) | 0.0009 (12) | 0.0046 (11) |
C7 | 0.0821 (17) | 0.0684 (16) | 0.0913 (18) | 0.0333 (14) | −0.0097 (14) | 0.0050 (13) |
C8 | 0.121 (3) | 0.094 (2) | 0.0859 (18) | 0.058 (2) | −0.0204 (18) | −0.0012 (16) |
C9 | 0.112 (2) | 0.094 (2) | 0.0842 (18) | 0.063 (2) | 0.0122 (16) | 0.0217 (16) |
C10 | 0.0820 (17) | 0.0778 (17) | 0.0947 (18) | 0.0463 (14) | 0.0110 (15) | 0.0148 (14) |
C11 | 0.0679 (15) | 0.0647 (14) | 0.0832 (15) | 0.0384 (13) | 0.0025 (13) | −0.0001 (13) |
N12 | 0.0638 (14) | 0.1025 (18) | 0.1008 (16) | 0.0263 (13) | 0.0001 (13) | −0.0157 (14) |
N1—C2 | 1.455 (3) | C6—C11 | 1.413 (3) |
N1—C2i | 1.455 (3) | C7—C8 | 1.366 (4) |
N1—C2ii | 1.455 (3) | C7—H7A | 0.9300 |
C2—C3 | 1.498 (4) | C8—C9 | 1.379 (4) |
C2—H2A | 0.9700 | C8—H8A | 0.9300 |
C2—H2B | 0.9700 | C9—C10 | 1.350 (4) |
C3—N4 | 1.454 (3) | C9—H9A | 0.9300 |
C3—H3A | 0.9700 | C10—C11 | 1.389 (3) |
C3—H3B | 0.9700 | C10—H10A | 0.9300 |
N4—C5 | 1.264 (3) | C11—N12 | 1.356 (3) |
C5—C6 | 1.454 (3) | N12—H12A | 0.92 (3) |
C5—H5A | 0.9300 | N12—H12B | 0.86 (3) |
C6—C7 | 1.386 (3) | ||
C2—N1—C2i | 111.28 (14) | C7—C6—C5 | 119.0 (2) |
C2—N1—C2ii | 111.28 (14) | C11—C6—C5 | 123.1 (2) |
C2i—N1—C2ii | 111.28 (14) | C8—C7—C6 | 122.3 (3) |
N1—C2—C3 | 112.9 (2) | C8—C7—H7A | 118.8 |
N1—C2—H2A | 109.0 | C6—C7—H7A | 118.8 |
C3—C2—H2A | 109.0 | C7—C8—C9 | 118.9 (3) |
N1—C2—H2B | 109.0 | C7—C8—H8A | 120.5 |
C3—C2—H2B | 109.0 | C9—C8—H8A | 120.5 |
H2A—C2—H2B | 107.8 | C10—C9—C8 | 120.7 (3) |
N4—C3—C2 | 110.9 (2) | C10—C9—H9A | 119.7 |
N4—C3—H3A | 109.5 | C8—C9—H9A | 119.7 |
C2—C3—H3A | 109.5 | C9—C10—C11 | 121.5 (3) |
N4—C3—H3B | 109.5 | C9—C10—H10A | 119.2 |
C2—C3—H3B | 109.5 | C11—C10—H10A | 119.2 |
H3A—C3—H3B | 108.1 | N12—C11—C10 | 120.6 (2) |
C5—N4—C3 | 118.0 (2) | N12—C11—C6 | 120.7 (2) |
N4—C5—C6 | 124.1 (2) | C10—C11—C6 | 118.7 (2) |
N4—C5—H5A | 117.9 | C11—N12—H12A | 120.7 (19) |
C6—C5—H5A | 117.9 | C11—N12—H12B | 115 (2) |
C7—C6—C11 | 117.9 (2) | H12A—N12—H12B | 123 (3) |
C2i—N1—C2—C3 | 83.1 (3) | C6—C7—C8—C9 | −0.1 (4) |
C2ii—N1—C2—C3 | −152.1 (3) | C7—C8—C9—C10 | 0.9 (4) |
N1—C2—C3—N4 | 76.1 (3) | C8—C9—C10—C11 | −1.1 (4) |
C2—C3—N4—C5 | −119.7 (3) | C9—C10—C11—N12 | 179.7 (2) |
C3—N4—C5—C6 | −178.2 (2) | C9—C10—C11—C6 | 0.6 (3) |
N4—C5—C6—C7 | −179.8 (2) | C7—C6—C11—N12 | −178.9 (2) |
N4—C5—C6—C11 | −0.3 (4) | C5—C6—C11—N12 | 1.6 (3) |
C11—C6—C7—C8 | −0.3 (4) | C7—C6—C11—C10 | 0.1 (3) |
C5—C6—C7—C8 | 179.1 (2) | C5—C6—C11—C10 | −179.3 (2) |
Symmetry codes: (i) −y+2, x−y+1, z; (ii) −x+y+1, −x+2, z. |
D—H···A | D—H | H···A | D···A | D—H···A |
N12—H12A···N4 | 0.92 (3) | 2.02 (3) | 2.700 (3) | 129 (2) |
N12—H12B···Cgiii | 0.86 (3) | 2.70 (3) | 3.430 (2) | 143 (3) |
C7—H7A···Cgi | 0.93 | 2.71 | 3.494 (3) | 143 |
Symmetry codes: (i) −y+2, x−y+1, z; (iii) x−y+1/3, x−1/3, −z+2/3. |
Experimental details
Crystal data | |
Chemical formula | C27H33N7 |
Mr | 455.60 |
Crystal system, space group | Trigonal, R3 |
Temperature (K) | 300 |
a, c (Å) | 13.1075 (18), 25.985 (6) |
V (Å3) | 3866.3 (12) |
Z | 6 |
Radiation type | Mo Kα |
µ (mm−1) | 0.07 |
Crystal size (mm) | 0.40 × 0.40 × 0.18 |
Data collection | |
Diffractometer | Siemens P4 |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 6668, 1507, 838 |
Rint | 0.033 |
(sin θ/λ)max (Å−1) | 0.594 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.058, 0.176, 1.81 |
No. of reflections | 1507 |
No. of parameters | 110 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.51, −0.21 |
Computer programs: XSCANS (Siemens, 1996), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), Mercury (Macrae et al., 2006).
D—H···A | D—H | H···A | D···A | D—H···A |
N12—H12A···N4 | 0.92 (3) | 2.02 (3) | 2.700 (3) | 129 (2) |
N12—H12B···Cgi | 0.86 (3) | 2.70 (3) | 3.430 (2) | 143 (3) |
C7—H7A···Cgii | 0.93 | 2.71 | 3.494 (3) | 142.6 |
Symmetry codes: (i) x−y+1/3, x−1/3, −z+2/3; (ii) −y+2, x−y+1, z. |
Acknowledgements
The authors thank the Facultad de Ciencias Químicas (UANL, Mexico) and PAICyT (project number IT164–09) for financial support.
References
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Recently, the research line of receptors with the ability to extract metal salts has grown in relevance, because of the harmful effects that anions and cations have in health and the environment. A class of such receptors includes polyamines, in which cations and anions are found in separate sites in a zwitterionic form of the ligand. As a consequence, the efficiency for solvent extraction of metal salts may be modulated trough pH adjustment (Wenzel, 2008). In these compounds, the metal ion coordinates in the deprotonated moiety, while the anion is associated to the protonated pendant groups (Bernier et al., 2009; Galbraith et al., 2006). The Schiff base condensation is a useful route to obtain polyamines including suitable structural characteristics in order to act as polytopic ligands. Some recent reports highlighted important applications of this type of compounds (Zibaseresht & Hartshorn, 2005; Mercs et al., 2008).
We report herein on the synthesis (Fig. 1) and crystal structure of a new Schiff base, which, we hope, will allow to bond both cations and anions, depending on the pH. The molecule (Fig. 2) is a tripodal tertiary amine NR3 where R contains imine functionality. The tripodal N atom is placed on a 3-fold axis in a trigonal cell (C3 point symmetry). The pendant arms R are gauche, as reflected by torsion angle N1—C2—C3—N4, 76.1 (3)°, and the lone pair on N1 is directed toward the cavity formed by the arms. Similar arrangements giving claw-like molecules were observed in related tertiary amines, although in less symmetric Laue groups (e.g. Weibel et al., 2002; Işıklan et al., 2010). In some instances, closely related tripodal NR3 molecules approximate the C3 symmetry but with R arms lying in a plane rather than forming a closed cavity (McKee et al., 2006). Glidewell et al. (2005) showed that the molecular conformation for this class of amines is determined mainly by direction-specific intra- and intermolecular interactions. In the case of the title amine, NH2 groups in the aniline moieties are engaged in both intra and intermolecular interactions: H12A forms a weak hydrogen bond with the imine atom N4, while H12B affords an intermolecular N—H···π contact, also of limited strength. The last significant contact is intramolecular: the C7—H7 aromatic group gives a C—H···π contact with the next arm in the molecule.
As mentioned, all non bonding contacts are rather weak. As a consequence, molecules are not densely packed in the crystal, and voids of ca 60 Å3 are available for solvent insertion. However, attempts to include non-diffracting solvent in the structural model using SQUEEZE (Spek, 2009) were unsuccessful. The chemical formula was thus left as unsolvated.