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organic compounds
The zwitterion of 4-nitro-2-{(E)-[2-(piperidin-1-yl)ethyl]iminomethyl}phenol
aFacultad de Ciencias Químicas, Universidad de Colima, Carretera Coquimatlán-Colima, Coquimatlán Colima, 28400, Mexico, and bUnidad Profesional Interdisciplinaria de Biotecnología, Instituto Politécnico Nacional, Avenida Acueducto s/n, Barrio La Laguna Ticomán, México DF 07340, Mexico
*Correspondence e-mail: fjmartin@ucol.mx
The title Schiff base compound, 4-nitro-1-oxo-2-{(E)-[2-(piperidin-1-yl)ethyl]iminiomethyl}cyclohexadienide, C14H19N3O3, exists as a zwitterion, with the H atom of the phenol group being transferred to the imine N atom. The C=O, CAr—CAr and C—N bond lengths are in agreement with the oxocyclohexadienide–iminium zwitterionic form. The iminium H atom is engaged in a strong intramolecular hydrogen bond with the O atom of the keto group (N+—H⋯O) to form an S(6) motif. Soft C—H⋯O interactions in the ac plane lead to the development of hydrogen-bonded tapes, which are π-stacked through the oxocyclohexadienide ring and iminium group. The significance of this study is in providing crystallographic evidence, supported by NMR and IR data, of the predominance of the oxocyclohexadienide–iminium zwitterion form over the noncharged in the title Schiff base.
Comment
Aromatic ; Sobczyk et al., 2005
). substituted in the aromatic ring have offered the opportunity to study the substituent effects in RAHBs. In this context, the molecular structure of the title compound, (I)
(Fig. 1
), is reported here.
The single-crystal structure of the title Schiff base compound is built up by discrete molecules in the monoclinic P2/c, with one molecule in the A summary of bond lengths and angles is presented in Table 1. The N8—C7 and O1—C1 bond lengths are in agreement with the double-bond character for the imine (ν at 1601 cm−1) and keto-carbonyl groups (ν at 1657 cm−1), respectively (Allen, 2002
). Moreover, the bond lengths in the C1–C6 ring show
![[link]](../../../../../../logos/arrows/c_arr.gif)
![Krygowski, T. M. & Stepien, B. T. (2005). Chem. Rev. 105, 3482-3512. [Krygowski, T. M. & Stepien, B. T. (2005). Chem. Rev. 105, 3482-3512.]](../../../../../../logos/arrows/c_arr.gif)
![Butt, G. L., Mackay, M. F. & Topsom, R. D. (1987). Acta Cryst. C43, 1092-1094. [Butt, G. L., Mackay, M. F. & Topsom, R. D. (1987). Acta Cryst. C43, 1092-1094.]](../../../../../../logos/arrows/c_arr.gif)
The iminium H atom (located in a difference map) is coplanar with the oxocyclohexadienide ring and on the same side of the molecule as the O atom of the keto group, allowing the formation of an intramolecular N—H⋯O hydrogen bond (Table 2) in an S(6) motif (Bernstein et al., 1995
), with dimensions in agreement with the usual values (Krygowski et al., 1997
; Steiner 1998
, 2002
). The N8⋯O1 distance has almost the same value as the RAHB of 2.607 (3) Å found in 3-{[(diphenoxythiophosphoryl)hydrazine]methylidene}-3,4-dihydro-2H-1-benzopyran-2,4-dione (Rybarczyk-Pirek et al., 2002
). The iminium H atom is also engaged in N—H⋯O hydrogen bonding with the O atom from the keto group of a neighbouring molecule, forming dimers with an almost square R22(4) motif (Fig. 2
).
The first dimension of the extended structure is built up by soft C—H⋯O interactions with the participation of one of the O atoms from the nitro group, in a monocoordinative fashion (Allen et al., 1997), as the acceptor of two hydrogen bonds (Table 2
) to form an R21(6) motif. The whole hydrogen-bonding scheme, makes up tapes propagating along the direction of the c axis. All C—H⋯ON and C⋯ON distances are shorter than the mean values of 2.7 (2) and 3.5 (2) Å, respectively, found in a study of nitrobenzenes (André et al., 1997
), although the C—H⋯ON angles are within the accepted range [C—H⋯O = 133 (20)°]. Even when C—H⋯O interactions involving an NO2 group as acceptor are half as strong as C—H⋯O interactions (Allen et al., 1997
) involving a CO group as the acceptor, they play a significant role in packing owing to their co-operative action.
The second dimension is ruled by the zwitterionic nature of (I). The anionic oxocyclohexadiene ring and the cationic iminium group from neighbouring tapes are overlapped. The iminium N and C atoms are 3.257 (3) and 3.462 (3) Å, respectively, from the centroid of the cyclohexadienide ring at (−x + 1, −y, −z). These short distances strongly suggest not only ion pairing but also a π-stacking interaction between the iminium group, as acceptor, and the oxocyclohexadiene ring, as the donor of electron density (Fig. 3
). These π-stacking interactions crosslink pairs of the hydrogen-bonded tapes described above to develop discrete centrosymmetric ribbons which propagate along the c axis.
![]() | Figure 1 The molecular structure of (I) ![]() |
![]() | Figure 2 Hydrogen-bonded tapes formed by N—H⋯O and C—H⋯O interactions along the c axis. H atoms not involved in the motifs shown have been omitted for clarity. [Symmetry codes: (i) −x + 1, y, −z + ![]() ![]() |
![]() | Figure 3 The centrosymmetric oxocyclohexadienide–iminium π-stacked pairs of compound (I) ![]() |
Experimental
Compound (I) was synthesized by amidation of ethyl 6-nitro-2-oxo-2H-chromene-3-carboxylate (0.5 g, 1.9 mmol), prepared according to Santos-Contreras et al. (2007
), with 1-(2-aminoethyl)piperidine (0.26 ml, 1.9 mmol) and two drops of piperidine as catalyst in refluxing ethanol (10 ml) for 24 h. The resulting orange solution was treated with and evaporated to give 0.3 g of an orange solid in 57% yield. Crystals suitable for X-ray analysis were obtained by slow evaporation from a saturated ethyl acetate solution (m.p. 413 K). IR (cm−1): ν (C=O) 1657, (C=N) 1601, (C—NO) 1535; 1H NMR (300 MHz, CDCl3): δ 6.90 (d, H6, 3J = 9.0 Hz), 8.16 (dd, H5, 3J = 9.0 and 4J = 3.0 Hz), 8.22 (d, H3, 3J = 9.0 Hz), 11.9 (b, NH), 8.31 (s, H7), 3.74 (t, 2H, 3J = 6.2 Hz, –+NHCH2–), 2.64 (t, 2H, 3J = 6.2 Hz, –CH2N), 2.46 [m, 4H, N—(CH2)2], 1.56 (m, 4H, –CH2–), 1.46 (m, 2H, –CH2–); 13C NMR: δ 173.1 (C1), 115.6 (C2), 129.7 (C3), 137.5 (C4), 129.0 (C5), 120.9 (C6), 165.3 (C7), 58.4 (C9), 53.2 (C10), 54.8 (C12), 26.2 (C13), 24.3 (C14).
Crystal data
|
Data collection
|
Refinement
|
|
|
The amino H atom was located in a difference Fourier map and refined with an N—H distance of 0.90 (2) Å. All other H atoms were positioned geometrically and refined using a riding model [C—H = 0.93 and 0.97 Å for aromatic and CH2 H atoms, respectively, and Uiso(H) = 1.2Ueq(C)].
Data collection: APEX2 (Bruker, 2004); cell SAINT (Bruker, 2004
); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008
); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008
); molecular graphics: SHELXTL (Sheldrick, 2008
) and Mercury (Macrae et al., 2006
); software used to prepare material for publication: SHELXL97 and WinGX2003 (Farrugia, 1999
).
Supporting information
10.1107/S0108270108040407/gd3261sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: 10.1107/S0108270108040407/gd3261Isup2.hkl
Compound (I) was synthesized by amidation of 0.5 g of ethyl-6-nitro-2-oxo-2H-chromene-3-carboxylate (1.9 mmol), prepared according with reported methodology (Santos-Contreras et al., 2007), with 0.26 ml of 1-(2-aminoethyl) piperidine (1.9 mmol) and two drops of piperidine as catalyst in 10 ml of refluxing ethanol for 24 h. The orange solution was treated with ν (C═O) 1657, 1601 (C═N), (C—NO) 1535; 1H NMR (300 MHz, CDCl3): δ 6.90 (d, H6, 3J = 9.0 Hz), 8.16 (dd, H5, 3J = 9.0 Hz and 4J = 3.0 Hz), 8.22 (d, H3, 3J = 9.0 Hz), 11.9 (b, NH), 8.31 (s, H7), 3.74 (t, 2H, 3J = 6.2 Hz, –+NHCH2–), 2.64 (t, 2H, 3J = 6.2 Hz, –CH2N), 2.46 (m, 4H, N—(CH2)2, 1.56 (m, 4H, –CH2–), 1.46 (m, 2H, –CH2–); 13C NMR: δ 173.1 (C1), 115.6 (C2), 129.7 (C3), 137.5 (C4), 129.0 (C5), 120.9 (C6), 165.3 (C7), 58.4 (C9), 53.2 (C10), 54.8 (C12), 26.2 (C13), 24.3 (C14).
and then evaporated to obtain 0.3 g of an orange solid in 57% yield. Crystals suitable for X-ray analysis were obtained by slow evaporation from saturated ethyl acetate solution (m.p. 413 K). IR (cm-1):The amino H atom was located in a difference Fourier map and was refined with an N—H distance restraint of 0.90 (2) Å [please check that this is the restraint; it appears to be the refined value]. All other H atoms were positioned geometrically and refined using a riding model [C—H = 0.93 and 0.97 Å for aromatic and CH2 H atoms, respectively, and Uiso(H) = 1.2Ueq(C)].
Data collection: APEX2 (Bruker, 2004); cell
SAINT (Bruker, 2004); data reduction: SAINT (Bruker, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008) and Mercury (Version 1.4.2; Macrae et al., 2006); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008) and WinGX2003 (Farrugia, 1999).C14H19N3O3 | F(000) = 592 |
Mr = 277.17 | Dx = 1.241 Mg m−3 |
Monoclinic, P2/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2yc | Cell parameters from 600 reflections |
a = 10.5688 (17) Å | θ = 20–25° |
b = 12.1887 (19) Å | µ = 0.09 mm−1 |
c = 12.6816 (15) Å | T = 293 K |
β = 114.696 (10)° | Block, colorless |
V = 1484.2 (4) Å3 | 0.20 × 0.17 × 0.12 mm |
Z = 4 |
Bruker APEXII area-detector diffractometer | Rint = 0.039 |
Graphite monochromator | θmax = 25.0°, θmin = 1.7° |
ϕ and ω scans | h = −12→12 |
13954 measured reflections | k = −14→14 |
2617 independent reflections | l = −15→15 |
2217 reflections with I > 2σ(I) |
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)] = 0.066 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.151 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.20 | w = 1/[σ2(Fo2) + (0.0545P)2 + 0.4948P] where P = (Fo2 + 2Fc2)/3 |
2617 reflections | (Δ/σ)max < 0.001 |
185 parameters | Δρmax = 0.21 e Å−3 |
0 restraints | Δρmin = −0.20 e Å−3 |
C14H19N3O3 | V = 1484.2 (4) Å3 |
Mr = 277.17 | Z = 4 |
Monoclinic, P2/c | Mo Kα radiation |
a = 10.5688 (17) Å | µ = 0.09 mm−1 |
b = 12.1887 (19) Å | T = 293 K |
c = 12.6816 (15) Å | 0.20 × 0.17 × 0.12 mm |
β = 114.696 (10)° |
Bruker APEXII area-detector diffractometer | 2217 reflections with I > 2σ(I) |
13954 measured reflections | Rint = 0.039 |
2617 independent reflections |
R[F2 > 2σ(F2)] = 0.066 | 0 restraints |
wR(F2) = 0.151 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.20 | Δρmax = 0.21 e Å−3 |
2617 reflections | Δρmin = −0.20 e Å−3 |
185 parameters |
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. |
x | y | z | Uiso*/Ueq | ||
O1 | 0.61744 (16) | 0.56198 (15) | 0.71035 (13) | 0.0554 (6) | |
O4A | 0.90206 (18) | 0.6309 (2) | 0.37604 (17) | 0.0822 (9) | |
O4B | 0.70959 (19) | 0.71709 (18) | 0.27970 (16) | 0.0702 (7) | |
N4 | 0.7876 (2) | 0.66443 (19) | 0.36479 (18) | 0.0561 (8) | |
N8 | 0.36262 (19) | 0.63064 (16) | 0.56787 (17) | 0.0424 (6) | |
N11 | 0.2518 (2) | 0.85530 (16) | 0.54095 (17) | 0.0527 (7) | |
C1 | 0.6566 (2) | 0.58808 (18) | 0.63278 (18) | 0.0427 (7) | |
C2 | 0.5618 (2) | 0.63386 (17) | 0.52278 (18) | 0.0391 (7) | |
C3 | 0.6069 (2) | 0.65830 (18) | 0.43661 (19) | 0.0421 (7) | |
C4 | 0.7429 (2) | 0.64084 (19) | 0.45537 (19) | 0.0446 (7) | |
C5 | 0.8388 (2) | 0.5980 (2) | 0.5617 (2) | 0.0528 (8) | |
C6 | 0.7975 (2) | 0.5734 (2) | 0.6469 (2) | 0.0528 (8) | |
C7 | 0.4195 (2) | 0.65234 (18) | 0.49839 (19) | 0.0426 (7) | |
C9 | 0.2183 (2) | 0.6557 (2) | 0.5425 (2) | 0.0508 (8) | |
C10 | 0.2061 (3) | 0.7661 (2) | 0.5922 (2) | 0.0552 (9) | |
C12 | 0.2898 (4) | 0.9518 (2) | 0.6147 (3) | 0.0803 (12) | |
C13 | 0.3521 (5) | 1.0384 (3) | 0.5668 (4) | 0.1090 (18) | |
C14 | 0.2542 (5) | 1.0705 (3) | 0.4457 (4) | 0.1172 (18) | |
C15 | 0.2066 (4) | 0.9692 (3) | 0.3707 (3) | 0.0911 (14) | |
C16 | 0.1493 (3) | 0.8843 (3) | 0.4255 (2) | 0.0727 (11) | |
H3 | 0.54440 | 0.68660 | 0.36590 | 0.0510* | |
H5 | 0.93080 | 0.58650 | 0.57370 | 0.0630* | |
H6 | 0.86280 | 0.54600 | 0.71690 | 0.0630* | |
H7 | 0.36320 | 0.68250 | 0.42660 | 0.0510* | |
H8 | 0.413 (3) | 0.601 (2) | 0.638 (2) | 0.062 (8)* | |
H9A | 0.18100 | 0.59910 | 0.57540 | 0.0610* | |
H9B | 0.16370 | 0.65620 | 0.45920 | 0.0610* | |
H10A | 0.10990 | 0.77830 | 0.57880 | 0.0660* | |
H10B | 0.26180 | 0.76560 | 0.67540 | 0.0660* | |
H12A | 0.35650 | 0.93140 | 0.69190 | 0.0970* | |
H12B | 0.20780 | 0.98100 | 0.62080 | 0.0970* | |
H13A | 0.43810 | 1.01100 | 0.56630 | 0.1310* | |
H13B | 0.37430 | 1.10250 | 0.61650 | 0.1310* | |
H14A | 0.30080 | 1.12000 | 0.41360 | 0.1410* | |
H14B | 0.17420 | 1.10830 | 0.44720 | 0.1410* | |
H15A | 0.13530 | 0.98920 | 0.29520 | 0.1090* | |
H15B | 0.28450 | 0.93820 | 0.35920 | 0.1090* | |
H16A | 0.06640 | 0.91280 | 0.43070 | 0.0870* | |
H16B | 0.12320 | 0.81910 | 0.37720 | 0.0870* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0454 (9) | 0.0826 (13) | 0.0419 (9) | 0.0051 (8) | 0.0218 (8) | 0.0039 (8) |
O4A | 0.0416 (11) | 0.143 (2) | 0.0713 (13) | −0.0046 (11) | 0.0327 (10) | −0.0041 (12) |
O4B | 0.0609 (12) | 0.0993 (15) | 0.0530 (11) | −0.0059 (10) | 0.0265 (10) | 0.0108 (10) |
N4 | 0.0403 (12) | 0.0829 (16) | 0.0478 (12) | −0.0133 (11) | 0.0210 (10) | −0.0081 (11) |
N8 | 0.0357 (10) | 0.0482 (11) | 0.0445 (11) | 0.0036 (8) | 0.0180 (9) | 0.0009 (9) |
N11 | 0.0543 (12) | 0.0550 (12) | 0.0524 (12) | 0.0070 (10) | 0.0258 (10) | −0.0019 (10) |
C1 | 0.0388 (12) | 0.0492 (13) | 0.0396 (12) | −0.0023 (10) | 0.0159 (10) | −0.0088 (10) |
C2 | 0.0341 (11) | 0.0422 (12) | 0.0416 (12) | −0.0015 (9) | 0.0163 (9) | −0.0057 (10) |
C3 | 0.0377 (12) | 0.0463 (13) | 0.0395 (12) | −0.0027 (10) | 0.0133 (10) | −0.0019 (10) |
C4 | 0.0375 (12) | 0.0538 (14) | 0.0434 (12) | −0.0087 (10) | 0.0179 (10) | −0.0088 (10) |
C5 | 0.0317 (12) | 0.0747 (17) | 0.0514 (14) | −0.0037 (11) | 0.0168 (11) | −0.0077 (12) |
C6 | 0.0332 (12) | 0.0758 (17) | 0.0423 (13) | 0.0021 (11) | 0.0087 (10) | −0.0005 (12) |
C7 | 0.0395 (12) | 0.0441 (13) | 0.0429 (12) | 0.0010 (10) | 0.0158 (10) | −0.0007 (10) |
C9 | 0.0360 (12) | 0.0589 (15) | 0.0606 (15) | 0.0030 (11) | 0.0233 (11) | 0.0053 (12) |
C10 | 0.0510 (14) | 0.0662 (16) | 0.0586 (15) | 0.0128 (12) | 0.0329 (13) | 0.0053 (13) |
C12 | 0.103 (2) | 0.068 (2) | 0.073 (2) | 0.0068 (17) | 0.0399 (18) | −0.0112 (16) |
C13 | 0.149 (4) | 0.067 (2) | 0.109 (3) | −0.030 (2) | 0.052 (3) | −0.020 (2) |
C14 | 0.168 (4) | 0.068 (2) | 0.123 (3) | −0.003 (3) | 0.068 (3) | 0.015 (2) |
C15 | 0.108 (3) | 0.087 (2) | 0.075 (2) | −0.002 (2) | 0.035 (2) | 0.0193 (18) |
C16 | 0.0649 (18) | 0.080 (2) | 0.0675 (18) | 0.0060 (15) | 0.0219 (15) | 0.0097 (16) |
O1—C1 | 1.257 (3) | C14—C15 | 1.511 (5) |
O4A—N4 | 1.227 (3) | C15—C16 | 1.507 (5) |
O4B—N4 | 1.230 (3) | C3—H3 | 0.9300 |
N4—C4 | 1.442 (3) | C5—H5 | 0.9300 |
N8—C7 | 1.285 (3) | C6—H6 | 0.9300 |
N8—C9 | 1.454 (3) | C7—H7 | 0.9300 |
N11—C10 | 1.449 (3) | C9—H9A | 0.9700 |
N11—C12 | 1.451 (3) | C9—H9B | 0.9700 |
N11—C16 | 1.455 (3) | C10—H10A | 0.9700 |
N8—H8 | 0.90 (2) | C10—H10B | 0.9700 |
C1—C2 | 1.447 (3) | C12—H12A | 0.9700 |
C1—C6 | 1.435 (3) | C12—H12B | 0.9700 |
C2—C7 | 1.421 (3) | C13—H13A | 0.9700 |
C2—C3 | 1.395 (3) | C13—H13B | 0.9700 |
C3—C4 | 1.372 (3) | C14—H14A | 0.9700 |
C4—C5 | 1.406 (3) | C14—H14B | 0.9700 |
C5—C6 | 1.357 (3) | C15—H15A | 0.9700 |
C9—C10 | 1.514 (3) | C15—H15B | 0.9700 |
C12—C13 | 1.500 (6) | C16—H16A | 0.9700 |
C13—C14 | 1.502 (7) | C16—H16B | 0.9700 |
O1···N8 | 2.674 (3) | C1···H10Bi | 3.1000 |
O1···C9i | 3.098 (3) | C3···H13Bv | 3.0200 |
O1···O1i | 3.043 (3) | C5···H9Avi | 2.9200 |
O1···N8i | 2.857 (3) | C9···H16B | 2.7600 |
O4A···C9ii | 3.134 (3) | C16···H9B | 2.8100 |
O4B···C3iii | 3.400 (3) | H3···O4B | 2.4400 |
O4B···C7iii | 3.302 (3) | H3···H7 | 2.3400 |
O1···H8i | 2.13 (3) | H3···O4Biii | 2.5700 |
O1···H8 | 2.02 (3) | H5···O4A | 2.4600 |
O1···H9Ai | 2.7000 | H6···O4Aviii | 2.8600 |
O1···H10Bi | 2.8900 | H7···H3 | 2.3400 |
O4A···H5 | 2.4600 | H7···H9B | 2.3300 |
O4A···H9Bii | 2.5300 | H7···O4Biii | 2.4400 |
O4A···H6iv | 2.8600 | H8···O1 | 2.02 (3) |
O4B···H3 | 2.4400 | H8···C1 | 2.61 (3) |
O4B···H3iii | 2.5700 | H8···O1i | 2.13 (3) |
O4B···H7iii | 2.4400 | H9A···O1i | 2.7000 |
O4B···H13Bv | 2.8900 | H9A···C5vi | 2.9200 |
N8···O1 | 2.674 (3) | H9B···O4Avii | 2.5300 |
N8···N11 | 2.942 (3) | H9B···C16 | 2.8100 |
N8···O1i | 2.857 (3) | H9B···H7 | 2.3300 |
N11···N8 | 2.942 (3) | H9B···H16B | 2.2000 |
N11···C7 | 3.217 (3) | H10A···H16A | 2.3900 |
C1···C7vi | 3.299 (3) | H10B···H12A | 2.2300 |
C1···C2vi | 3.568 (3) | H10B···O1i | 2.8900 |
C2···C1vi | 3.568 (3) | H10B···C1i | 3.1000 |
C2···C7vi | 3.511 (3) | H12A···H10B | 2.2300 |
C2···C2vi | 3.472 (3) | H12B···H14B | 2.5900 |
C3···O4Biii | 3.400 (3) | H12B···H16A | 2.3900 |
C5···C9vi | 3.318 (3) | H13A···H15B | 2.6000 |
C6···C7vi | 3.563 (3) | H13A···H13Av | 2.5400 |
C7···C6vi | 3.563 (3) | H13B···O4Bv | 2.8900 |
C7···C2vi | 3.511 (3) | H13B···C3v | 3.0200 |
C7···O4Biii | 3.302 (3) | H14B···H12B | 2.5900 |
C7···C1vi | 3.299 (3) | H15A···H15Aix | 2.6000 |
C7···N11 | 3.217 (3) | H15B···H13A | 2.6000 |
C9···O4Avii | 3.134 (3) | H16A···H10A | 2.3900 |
C9···C5vi | 3.318 (3) | H16A···H12B | 2.3900 |
C9···O1i | 3.098 (3) | H16B···C9 | 2.7600 |
C1···H8 | 2.61 (3) | H16B···H9B | 2.2000 |
O4A—N4—O4B | 122.9 (2) | C2—C7—H7 | 117.00 |
O4A—N4—C4 | 118.4 (2) | N8—C9—H9A | 109.00 |
O4B—N4—C4 | 118.7 (2) | N8—C9—H9B | 110.00 |
C7—N8—C9 | 123.6 (2) | C10—C9—H9A | 109.00 |
C10—N11—C12 | 111.9 (2) | C10—C9—H9B | 109.00 |
C10—N11—C16 | 112.7 (2) | H9A—C9—H9B | 108.00 |
C12—N11—C16 | 109.9 (2) | N11—C10—H10A | 109.00 |
C9—N8—H8 | 116 (2) | N11—C10—H10B | 109.00 |
C7—N8—H8 | 121 (2) | C9—C10—H10A | 109.00 |
O1—C1—C6 | 122.3 (2) | C9—C10—H10B | 109.00 |
O1—C1—C2 | 122.0 (2) | H10A—C10—H10B | 108.00 |
C2—C1—C6 | 115.7 (2) | N11—C12—H12A | 109.00 |
C1—C2—C7 | 121.0 (2) | N11—C12—H12B | 109.00 |
C1—C2—C3 | 120.8 (2) | C13—C12—H12A | 109.00 |
C3—C2—C7 | 118.2 (2) | C13—C12—H12B | 109.00 |
C2—C3—C4 | 120.5 (2) | H12A—C12—H12B | 108.00 |
N4—C4—C5 | 119.6 (2) | C12—C13—H13A | 109.00 |
C3—C4—C5 | 120.5 (2) | C12—C13—H13B | 109.00 |
N4—C4—C3 | 120.0 (2) | C14—C13—H13A | 109.00 |
C4—C5—C6 | 120.2 (2) | C14—C13—H13B | 109.00 |
C1—C6—C5 | 122.4 (2) | H13A—C13—H13B | 108.00 |
N8—C7—C2 | 125.0 (2) | C13—C14—H14A | 110.00 |
N8—C9—C10 | 111.0 (2) | C13—C14—H14B | 110.00 |
N11—C10—C9 | 112.2 (2) | C15—C14—H14A | 110.00 |
N11—C12—C13 | 111.1 (3) | C15—C14—H14B | 110.00 |
C12—C13—C14 | 111.5 (4) | H14A—C14—H14B | 108.00 |
C13—C14—C15 | 109.7 (3) | C14—C15—H15A | 109.00 |
C14—C15—C16 | 111.3 (3) | C14—C15—H15B | 109.00 |
N11—C16—C15 | 110.9 (3) | C16—C15—H15A | 109.00 |
C2—C3—H3 | 120.00 | C16—C15—H15B | 109.00 |
C4—C3—H3 | 120.00 | H15A—C15—H15B | 108.00 |
C4—C5—H5 | 120.00 | N11—C16—H16A | 109.00 |
C6—C5—H5 | 120.00 | N11—C16—H16B | 109.00 |
C1—C6—H6 | 119.00 | C15—C16—H16A | 109.00 |
C5—C6—H6 | 119.00 | C15—C16—H16B | 110.00 |
N8—C7—H7 | 117.00 | H16A—C16—H16B | 108.00 |
O4B—N4—C4—C5 | −169.0 (2) | C6—C1—C2—C3 | 1.8 (3) |
O4A—N4—C4—C5 | 11.1 (3) | O1—C1—C6—C5 | 177.7 (2) |
O4A—N4—C4—C3 | −167.7 (2) | C3—C2—C7—N8 | 177.8 (2) |
O4B—N4—C4—C3 | 12.3 (3) | C1—C2—C7—N8 | −0.5 (3) |
C9—N8—C7—C2 | 176.8 (2) | C1—C2—C3—C4 | −1.0 (3) |
C7—N8—C9—C10 | −93.7 (3) | C7—C2—C3—C4 | −179.3 (2) |
C10—N11—C12—C13 | 173.5 (3) | C2—C3—C4—N4 | 178.8 (2) |
C16—N11—C10—C9 | 77.0 (3) | C2—C3—C4—C5 | 0.0 (3) |
C12—N11—C16—C15 | 60.1 (4) | C3—C4—C5—C6 | 0.1 (4) |
C16—N11—C12—C13 | −60.5 (4) | N4—C4—C5—C6 | −178.7 (2) |
C12—N11—C10—C9 | −158.4 (3) | C4—C5—C6—C1 | 0.8 (4) |
C10—N11—C16—C15 | −174.3 (3) | N8—C9—C10—N11 | 62.9 (3) |
C6—C1—C2—C7 | −180.0 (2) | N11—C12—C13—C14 | 57.5 (5) |
C2—C1—C6—C5 | −1.7 (3) | C12—C13—C14—C15 | −52.8 (5) |
O1—C1—C2—C3 | −177.6 (2) | C13—C14—C15—C16 | 52.4 (5) |
O1—C1—C2—C7 | 0.7 (3) | C14—C15—C16—N11 | −56.8 (4) |
Symmetry codes: (i) −x+1, y, −z+3/2; (ii) x+1, y, z; (iii) −x+1, y, −z+1/2; (iv) x, −y+1, z−1/2; (v) −x+1, −y+2, −z+1; (vi) −x+1, −y+1, −z+1; (vii) x−1, y, z; (viii) x, −y+1, z+1/2; (ix) −x, y, −z+1/2. |
D—H···A | D—H | H···A | D···A | D—H···A |
N8—H8···O1 | 0.90 (2) | 2.02 (3) | 2.674 (3) | 129 (3) |
N8—H8···O1i | 0.90 (2) | 2.13 (3) | 2.857 (3) | 137 (3) |
C3—H3···O4Biii | 0.93 | 2.57 | 3.400 (3) | 149 |
C7—H7···O4Biii | 0.93 | 2.44 | 3.302 (3) | 155 |
C9—H9B···O4Avii | 0.97 | 2.53 | 3.134 (3) | 120 |
Symmetry codes: (i) −x+1, y, −z+3/2; (iii) −x+1, y, −z+1/2; (vii) x−1, y, z. |
Experimental details
Crystal data | |
Chemical formula | C14H19N3O3 |
Mr | 277.17 |
Crystal system, space group | Monoclinic, P2/c |
Temperature (K) | 293 |
a, b, c (Å) | 10.5688 (17), 12.1887 (19), 12.6816 (15) |
β (°) | 114.696 (10) |
V (Å3) | 1484.2 (4) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.09 |
Crystal size (mm) | 0.20 × 0.17 × 0.12 |
Data collection | |
Diffractometer | Bruker APEXII area-detector diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 13954, 2617, 2217 |
Rint | 0.039 |
(sin θ/λ)max (Å−1) | 0.594 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.066, 0.151, 1.20 |
No. of reflections | 2617 |
No. of parameters | 185 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.21, −0.20 |
Computer programs: APEX2 (Bruker, 2004), SAINT (Bruker, 2004), SHELXS97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008) and Mercury (Version 1.4.2; Macrae et al., 2006), SHELXL97 (Sheldrick, 2008) and WinGX2003 (Farrugia, 1999).
O1—C1 | 1.257 (3) | N11—C16 | 1.455 (3) |
O4A—N4 | 1.227 (3) | C1—C2 | 1.447 (3) |
O4B—N4 | 1.230 (3) | C1—C6 | 1.435 (3) |
N4—C4 | 1.442 (3) | C2—C3 | 1.395 (3) |
N8—C7 | 1.285 (3) | C3—C4 | 1.372 (3) |
N8—C9 | 1.454 (3) | C4—C5 | 1.406 (3) |
N11—C10 | 1.449 (3) | C5—C6 | 1.357 (3) |
N11—C12 | 1.451 (3) | C9—C10 | 1.514 (3) |
O4A—N4—O4B | 122.9 (2) | O1—C1—C2 | 122.0 (2) |
O4A—N4—C4 | 118.4 (2) | N4—C4—C5 | 119.6 (2) |
O4B—N4—C4 | 118.7 (2) | N4—C4—C3 | 120.0 (2) |
C7—N8—C9 | 123.6 (2) | N8—C7—C2 | 125.0 (2) |
C10—N11—C12 | 111.9 (2) | N8—C9—C10 | 111.0 (2) |
C10—N11—C16 | 112.7 (2) | N11—C10—C9 | 112.2 (2) |
C12—N11—C16 | 109.9 (2) | N11—C12—C13 | 111.1 (3) |
O1—C1—C6 | 122.3 (2) | N11—C16—C15 | 110.9 (3) |
D—H···A | D—H | H···A | D···A | D—H···A |
N8—H8···O1 | 0.90 (2) | 2.02 (3) | 2.674 (3) | 129 (3) |
N8—H8···O1i | 0.90 (2) | 2.13 (3) | 2.857 (3) | 137 (3) |
C3—H3···O4Bii | 0.93 | 2.57 | 3.400 (3) | 149 |
C7—H7···O4Bii | 0.93 | 2.44 | 3.302 (3) | 155 |
Symmetry codes: (i) −x+1, y, −z+3/2; (ii) −x+1, y, −z+1/2. |
Acknowledgements
This work was supported by CGIC–UC (Coordinación General de Investigación Científica de la Universidad de Colima) and SIP–IPN (Secretaria de Investigación y Postgrado del Instituto Politécnico Nacional).
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This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.
Aromatic imines and their derivatives, are an important group of molecules in organic chemistry, in particular those that have aryl groups bound to N or C atoms. They have been used successfully to study resonance-assisted hydrogen bonds (RAHBs; Krygowski & Stepien, 2005; Sobczyk et al., 2005). Imines substituted in the aromatic ring have offered the opportunity to study the substituent effects in RAHBs. In this context, the molecular structure of the title compound, (I) (Fig. 1), is reported here.
The single-crystal structure of the title Schiff base compound is built up by discrete C14H19N3O3 molecules in the monoclinic space group P2/c, with four molecules in the asymmetric unit. A summary of bond lengths and angles is listed in Table 1. The N8—C7 and O1—C9 (C1?) bond lengths are in agreement with the double-bond character for the imine (ν at 1601 cm-1) and keto-carbonyl groups (ν at 1657 cm-1), respectively (Allen, 2002). Moreover, the bond lengths in the ring (C1–C6) show clear alternation in the delocalized portion C2–C6. The nitro group is tilted out of the mean plane of the adjacent ring by -11.1 (3)°, whereas the C4—N4 distance is in the characteristic range, suggesting limited conjugation with the ring. Thus, the whole geometry is in agreement with the predominace of the ketodienide–iminium zwitterion bonding scheme (see scheme) (Krygowski & Stepien, 2005), in close agreement with p-nitrophenolates of alkali metal cations (Butt et al., 1987).
The iminium H atom (located in a difference map) is coplanar with the keto-cyclohexadienide ring and on the same side of the molecule as the O atom from the keto group, allowing the formation of an intramolecular N—H···O hydrogen bond (Table 2) in an S(6) motif (Bernstein et al., 1995), with dimensions in agreement with the accepted values (Krygowski et al., 1997; Steiner 1998, 2002). The N8···O1 distance has almost the same value as the RAHB of 2.607</span><span style=" font-weight:600;">(3) Å found in 3-{[(diphenoxy-thio-phosphoryl)hydrazine]methylidene}-3,4-dihydro-2H-1-benzopyran-2,4-dione (Rybarczyk-Pirek et al., 2002). The iminium H atom is also engaged in N···H···O hydrogen bonding with the O atom from the keto group of a neighbouring molecule, forming dimers with an almost square R22(4) motif (Fig. 2).
The first dimension is built up by soft C—H···O interactions with the participation of one of the O atoms from the nitro group, in monocoordinative fashion (Allen et al., 1997), as the acceptor of two H atoms (Table 2) to form an R12(6) motif. The whole hydrogen-bonding scheme, makes up tapes propagating along the direction of the c axis. All C—H···ON and C···ON distances are shorter than the mean values of 2.7 (2) and 3.5 (2) Å found in a study of nitrobenzenes (André et al., 1997), although the C—H···ON angles are within the accepted range [C—H···O = 133 (20)°]. Even when C—H···O interactions involving an NO2 group as the acceptor are half as strong as C—H···O interactions (Allen et al., 1997) involving a CO group as the acceptor, they play a significant role in packing owing to their cooperative action.
The second dimension is ruled by the switterionic nature of (I). The anionic keto-cyclohexadiene rin and the cationic iminium group from neighboring tapes are overlapped. The iminium N and C atoms are at 3.257 (3) and 3.462 (3) Å, respectively, from the centroid of the cyclohexadienide ring at (-x + 1, -y, -z). These short distances strongly suggest not only ion-pairing but also a π-stacking interaction between the iminium, as the acceptor, and keto-cyclohexadiene ring, as the donor of electronic density developing discrete centrosymmetric ribbons along the b axis (Fig. 3).