Tris[2-(2-nitro­benzyl­ideneamino)eth­yl]amine

McKee, V.; Morgan, G.G.; Nelson, J.

doi:10.1107/S1600536806030492

organic compounds

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ISSN: 2056-9890

Volume 62| Part 9| September 2006| Pages o3747-o3749

https://doi.org/10.1107/S1600536806030492

Tris[2-(2-nitrobenzylideneamino)ethyl]amine

Vickie McKee,^a ^* Grace G, Morgan ^b and Jane Nelson ^a

^aChemistry Department, Loughborough University, Loughborough, Leics LE11 3TU, England, and ^bSchool of Chemistry, University College Dublin, Belfield, Dublin 4, Ireland
^*Correspondence e-mail: v.mckee@lboro.ac.uk

(Received 1 August 2006; accepted 3 August 2006; online 9 August 2006)

The title imine podand, C₂₇H₂₇N₇O₆, is approximately planar, with the amine N atom lying on a threefold axis. π–π Stacking of the nitrobenzene groups and significant C—H⋯O hydrogen bonds are present in the crystal structure.

Comment

Our long-standing interest in the chemistry of cryptands based on tris(aminoethyl)amine and related amines (see for example McKee et al., 2003 ; Nelson et al., 1998 ) has led us to synthesize a range of analogous podates in order to compare their properties with those of the related cryptand and cryptate systems.

In this paper we report the structure of tris[N-2-(nitrobenzylideneamino)ethyl]amine, (I), which was prepared by Schiff base condensation of 2-nitrobenzaldehyde with tris(aminoethyl)amine (tren). Compound (I) crystallizes in the trigonal space group R $[\overline{3}]$ and lies on a threefold axis (Fig. 1). The molecule overall is approximately planar [r.m.s. deviation of all non-H atoms from the mean plane is 0.264 (2) Å]. This arrangement allows the π systems to stack parallel to the c axis (Fig. 2). The benzene ring comprising C4–C9 is inclined at 7.69 (2)° to its equivalent by symmetry operation ( $[{2\over 3}]$ − y, − $[{2\over 3}]$ + x − y, $[{1\over 3}]$ + z) and the centroid of the ring is 3.432 (1) Å from the plane of the second ring; the ring centroids are 3.835 (2) Å apart. The plane of the nitro group is inclined at 22.75 (4)° to the mean plane of the benzene ring.

A search of the CSD (Version 5.27; Allen, 2002 ; Fletcher et al., 1996 ) shows that, although many tris(aminoethyl)amine/salicylate complexes have been investigated, few simple podands with other substituted benzaldehyde derivatives have been structurally characterized. The closest analogue in the literature is tris(N-4-nitrobenzylideneaminoethyl)amine (Glidewell et al., 2005 ). In that structure the three arms of the molecule are independent and each has a different conformation. The molecule has a more `closed' conformation, due to intramolecular π–π interactions between two of the rings. There are also intermolecular π–π interactions as well as one intramolecular, and one intermolecular, C—H⋯O hydrogen bond.

None of the podands reported previously have the planar geometry seen in the present compound. A likely reason for this unusual arrangement is that the position of the nitro group allows formation of a total of 12 intermolecular C—H⋯O hydrogen bonds per molecule which support the π stacking in the lattice (Table 1). Fig. 3 shows the C12—H12⋯O12ⁱⁱⁱ hydrogen bond along with the five symmetry-related interactions involving a single molecule of (I). The central molecule is linked into three R₂²(16) rings (Etter et al., 1990 ) and lies slightly below the mean plane of the other three molecules. Similarly, Fig. 4 shows the C18—H18⋯O11^iv hydrogen bond and symmetry-related interactions; in this case R₂²(34) rings result and the central molecule is above the plane of the three neighbours. The two arrays of molecules hydrogen bonded to the central molecule interact with each other by π–π stacking, as shown in Fig. 2.

Figure 1
Perspective view of the structure (I)

; displacement ellipsoids are drawn at the 50% probability level. [Symmetry codes (i) 1 − y, x − y − 1, z; (ii) 2 − x + y, 1 − x, z.]

Figure 2
Packing diagram viewed down the c axis and showing π–π stacking. H atoms have been omitted for clarity.

Figure 3
C12—H12⋯O12ⁱⁱⁱ and symmetry-related hydrogen-bonds (shown dashed). [Symmetry code: (iii) $[4\over3]$ − x, − $[{1\over 3}]$ − y, $[{2\over 3}]$ − z.]

Figure 4
C18—H18⋯O11^iv and symmetry-related hydrogen-bonds (shown dashed). [Symmetry code: (iv) x − y − $[{1\over 3}]$ , x − $[{2\over 3}]$ , $[{1\over 3}]$ − z.]

Experimental

Compound (I) was prepared by condensation of tris(2-aminoethyl)amine (1.04 g, 7.1 mmol) and 2-nitrobenzaldehyde (3.17 g, 20.0 mmol) in ethanol (50 ml). The solution was refluxed for 30 min and the product obtained as yellow crystals on reducing the volume (yield 3.73 g, 98%). Analysis calculated for C₂₇H₂₇N₇O₆: C 59.4, H 5.0, N 18.0%; found C 59.2, H 4.9, N 18.0%.

Crystal data

C₂₇H₂₇N₇O₆
M_r = 545.56
Trigonal, $[R \overline 3]$
a = 20.765 (1) Å
c = 10.453 (1) Å
V = 3903.3 (5) Å³
Z = 6
D_x = 1.393 Mg m⁻³
Mo Kα radiation
μ = 0.10 mm⁻¹
T = 123 (2) K
Block, yellow
0.55 × 0.40 × 0.30 mm

Data collection

Siemens P4 four-circle diffractometer
ω scans
Absorption correction: none
2518 measured reflections
1952 independent reflections
1425 reflections with I > 2σ(I)
R_int = 0.016
θ_max = 27.5°
3 standard reflections every 97 reflections intensity decay: none

Refinement

Refinement on F²
R[F² > 2σ(F²)] = 0.047
wR(F²) = 0.118
S = 1.03
1952 reflections
121 parameters
H-atom parameters constrained
w = 1/[σ²(F_o²) + (0.0491P)² + 5.6815P] where P = (F_o² + 2F_c²)/3
(Δ/σ)_max < 0.001
Δρ_max = 0.26 e Å⁻³
Δρ_min = −0.23 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C12—H12A⋯O12ⁱⁱⁱ	0.99	2.60	3.592 (2)	178
C18—H18⋯O11^iv	0.95	2.51	3.147 (2)	124
Symmetry codes: (iii) $[-x+{\script{4\over 3}}, -y-{\script{1\over 3}}, -z+{\script{2\over 3}}]$ ; (iv) $[x-y-{\script{1\over 3}}, x-{\script{2\over 3}}, -z+{\script{1\over 3}}]$ .

H atoms were placed at calculated positions and refined using a riding model. The constrained distances were 0.95 and 0.99 Å for aryl and methylene, respectively. They were refined with U_iso(H) = 1.2U_eq(C).

Data collection: XSCANS (Siemens, 1994 ); cell refinement: XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Sheldrick, 2001 ); software used to prepare material for publication: SHELXTL.

Supporting information

Crystal structure: contains datablocks I, global. DOI: https://doi.org/10.1107/S1600536806030492/sj2093sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536806030492/sj2093Isup2.hkl

Computing details top

Data collection: XSCANS (Siemens, 1994); cell refinement: XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Sheldrick, 2001); software used to prepare material for publication: SHELXTL.

Tris[N-2-(nitrobenzylideneamino)ethyl]amine top

Crystal data top

C₂₇H₂₇N₇O₆	D_x = 1.393 Mg m⁻³
M_r = 545.56	Mo Kα radiation, λ = 0.71073 Å
Trigonal, R3	Cell parameters from 31 reflections
Hall symbol: -R 3	θ = 5.0–12.5°
a = 20.765 (1) Å	µ = 0.10 mm⁻¹
c = 10.453 (1) Å	T = 123 K
V = 3903.3 (5) Å³	Block, yellow
Z = 6	0.55 × 0.40 × 0.30 mm
F(000) = 1716

Data collection top

Siemens P4 four-circle diffractometer	R_int = 0.016
Radiation source: normal-focus sealed tube	θ_max = 27.5°, θ_min = 2.3°
Graphite monochromator	h = −1→26
ω scans	k = −26→1
2518 measured reflections	l = −1→13
1952 independent reflections	3 standard reflections every 97 reflections
1425 reflections with I > 2σ(I)	intensity decay: none

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.047	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.118	H-atom parameters constrained
S = 1.03	w = 1/[σ²(F_o²) + (0.0491P)² + 5.6815P] where P = (F_o² + 2F_c²)/3
1952 reflections	(Δ/σ)_max < 0.001
121 parameters	Δρ_max = 0.26 e Å⁻³
0 restraints	Δρ_min = −0.23 e Å⁻³

Special details top

Experimental. NMR (CDCl₃, p.p.m., ¹H): 3.01(t, 6, CH₂), 3.80(t, 6, CH₂),), 8.64(s, 3, imine), 7.99(d, 3, aromatic), 7.97 (d, 3, aromatic), 7.49–7.61(m, 6, aromatic. Mass spectrum (FAB): m/e 546 (I+H⁺). IR (KBr, cm^-1) inter alia: 1629(m, imine), 1521(s, NO₂), 1342(m, NO₂).

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 (Å²) top

	x	y	z	U_iso*/U_eq
N1	1.0000	0.0000	0.2625 (3)	0.0251 (6)
C11	0.95311 (10)	0.03093 (10)	0.2257 (2)	0.0296 (4)
H11A	0.9301	0.0106	0.1414	0.036*
H11B	0.9842	0.0856	0.2173	0.036*
C12	0.89304 (10)	0.01266 (11)	0.3229 (2)	0.0301 (4)
H12A	0.8646	−0.0418	0.3366	0.036*
H12B	0.9159	0.0365	0.4054	0.036*
N11	0.84242 (8)	0.03839 (8)	0.28074 (16)	0.0297 (4)
C13	0.77375 (9)	−0.00662 (9)	0.29467 (16)	0.0220 (4)
H13	0.7572	−0.0561	0.3221	0.026*
C14	0.71876 (9)	0.01770 (9)	0.26824 (15)	0.0188 (3)
C15	0.74417 (10)	0.09390 (10)	0.26214 (17)	0.0238 (4)
H15	0.7961	0.1279	0.2661	0.029*
C16	0.69605 (11)	0.12121 (10)	0.25056 (18)	0.0286 (4)
H16	0.7152	0.1733	0.2450	0.034*
C17	0.61985 (11)	0.07295 (11)	0.24696 (18)	0.0290 (4)
H17	0.5868	0.0920	0.2406	0.035*
C18	0.59218 (9)	−0.00295 (10)	0.25268 (17)	0.0246 (4)
H18	0.5401	−0.0365	0.2511	0.029*
C19	0.64171 (9)	−0.02941 (9)	0.26073 (15)	0.0199 (3)
N12	0.60806 (8)	−0.11087 (8)	0.25530 (14)	0.0255 (3)
O11	0.64710 (8)	−0.13623 (7)	0.21889 (13)	0.0333 (3)
O12	0.54240 (8)	−0.14936 (8)	0.28380 (15)	0.0409 (4)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
N1	0.0137 (7)	0.0137 (7)	0.0479 (16)	0.0068 (4)	0.000	0.000
C11	0.0243 (9)	0.0224 (9)	0.0441 (11)	0.0131 (8)	0.0005 (8)	0.0056 (8)
C12	0.0230 (9)	0.0285 (10)	0.0436 (11)	0.0165 (8)	−0.0017 (8)	0.0024 (8)
N11	0.0218 (8)	0.0248 (8)	0.0461 (10)	0.0143 (7)	0.0010 (7)	0.0044 (7)
C13	0.0224 (9)	0.0213 (8)	0.0257 (8)	0.0135 (7)	−0.0002 (7)	0.0015 (7)
C14	0.0193 (8)	0.0207 (8)	0.0185 (8)	0.0116 (7)	0.0005 (6)	0.0008 (6)
C15	0.0208 (9)	0.0207 (8)	0.0284 (9)	0.0092 (7)	−0.0015 (7)	0.0018 (7)
C16	0.0366 (10)	0.0217 (9)	0.0325 (10)	0.0183 (8)	−0.0041 (8)	−0.0005 (7)
C17	0.0310 (10)	0.0372 (10)	0.0318 (9)	0.0268 (9)	−0.0025 (8)	−0.0012 (8)
C18	0.0179 (8)	0.0316 (10)	0.0251 (9)	0.0130 (8)	−0.0005 (7)	−0.0023 (7)
C19	0.0211 (8)	0.0192 (8)	0.0188 (8)	0.0098 (7)	−0.0001 (6)	−0.0008 (6)
N12	0.0269 (8)	0.0217 (8)	0.0233 (7)	0.0089 (6)	−0.0018 (6)	−0.0006 (6)
O11	0.0403 (8)	0.0253 (7)	0.0396 (8)	0.0204 (6)	−0.0052 (6)	−0.0055 (6)
O12	0.0273 (7)	0.0291 (8)	0.0475 (9)	0.0000 (6)	0.0042 (6)	−0.0008 (6)

Geometric parameters (Å, º) top

N1—C11ⁱ	1.4607 (19)	C14—C19	1.399 (2)
N1—C11ⁱⁱ	1.4607 (19)	C15—C16	1.379 (2)
N1—C11	1.4607 (19)	C15—H15	0.9500
C11—C12	1.503 (3)	C16—C17	1.387 (3)
C11—H11A	0.9900	C16—H16	0.9500
C11—H11B	0.9900	C17—C18	1.383 (3)
C12—N11	1.465 (2)	C17—H17	0.9500
C12—H12A	0.9900	C18—C19	1.390 (2)
C12—H12B	0.9900	C18—H18	0.9500
N11—C13	1.263 (2)	C19—N12	1.474 (2)
C13—C14	1.487 (2)	N12—O12	1.223 (2)
C13—H13	0.9500	N12—O11	1.2273 (19)
C14—C15	1.397 (2)

C11ⁱ—N1—C11ⁱⁱ	113.33 (11)	C15—C14—C13	118.28 (15)
C11ⁱ—N1—C11	113.33 (11)	C19—C14—C13	125.23 (15)
C11ⁱⁱ—N1—C11	113.33 (11)	C16—C15—C14	121.93 (16)
N1—C11—C12	111.25 (17)	C16—C15—H15	119.0
N1—C11—H11A	109.4	C14—C15—H15	119.0
C12—C11—H11A	109.4	C15—C16—C17	120.31 (17)
N1—C11—H11B	109.4	C15—C16—H16	119.8
C12—C11—H11B	109.4	C17—C16—H16	119.8
H11A—C11—H11B	108.0	C18—C17—C16	119.74 (16)
N11—C12—C11	111.16 (16)	C18—C17—H17	120.1
N11—C12—H12A	109.4	C16—C17—H17	120.1
C11—C12—H12A	109.4	C17—C18—C19	119.03 (16)
N11—C12—H12B	109.4	C17—C18—H18	120.5
C11—C12—H12B	109.4	C19—C18—H18	120.5
H12A—C12—H12B	108.0	C18—C19—C14	122.73 (15)
C13—N11—C12	116.49 (15)	C18—C19—N12	115.57 (15)
N11—C13—C14	120.12 (15)	C14—C19—N12	121.65 (15)
N11—C13—H13	119.9	O12—N12—O11	123.69 (15)
C14—C13—H13	119.9	O12—N12—C19	118.32 (15)
C15—C14—C19	116.20 (15)	O11—N12—C19	117.96 (14)

C11ⁱ—N1—C11—C12	83.6 (3)	C16—C17—C18—C19	−0.6 (3)
C11ⁱⁱ—N1—C11—C12	−145.41 (19)	C17—C18—C19—C14	2.5 (3)
N1—C11—C12—N11	−175.32 (15)	C17—C18—C19—N12	−174.98 (15)
C11—C12—N11—C13	135.09 (18)	C15—C14—C19—C18	−2.5 (2)
C12—N11—C13—C14	173.14 (16)	C13—C14—C19—C18	171.22 (16)
N11—C13—C14—C15	−17.0 (3)	C15—C14—C19—N12	174.88 (15)
N11—C13—C14—C19	169.45 (17)	C13—C14—C19—N12	−11.5 (2)
C19—C14—C15—C16	0.6 (3)	C18—C19—N12—O12	−22.2 (2)
C13—C14—C15—C16	−173.55 (16)	C14—C19—N12—O12	160.27 (16)
C14—C15—C16—C17	1.2 (3)	C18—C19—N12—O11	155.76 (15)
C15—C16—C17—C18	−1.2 (3)	C14—C19—N12—O11	−21.7 (2)

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

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C13—H13···O11	0.95	2.31	2.777 (2)	109
C12—H12A···O12ⁱⁱⁱ	0.99	2.60	3.592 (2)	178
C18—H18···O11^iv	0.95	2.51	3.147 (2)	124

Symmetry codes: (iii) −x+4/3, −y−1/3, −z+2/3; (iv) x−y−1/3, x−2/3, −z+1/3.

Acknowledgements

We thank the Leverhulme Foundation and Unilever R&D for support and acknowledge the use of the EPSRC's Chemical Database Service at Daresbury.

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