Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270107037900/sq3092sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270107037900/sq3092Isup2.hkl |
CCDC reference: 661821
For related literature, see: Bresciani Pahor, Calligaris, Nardin & Randaccio (1978); Elderman et al. (1991); Etemadi et al. (2004); Karigiannis & Papaioannou (2000); Kennedy & Reglinski (2001); Novitchi et al. (2002); Sheikhshoaie & Sharif (2006); Silvestri et al. (2007); Yu (2006).
To a solution of salicylaldehyde (0.4 mmol) in ethanol (30 ml), cadaverine (0.1 mmol) in methanol (30 ml) was added dropwise over a period of 30 min with stirring. The reaction was carried out for 72 h under an argon atmosphere. The solution volume was then reduced to 5 ml by rotary evaporation and the remaining solution was left to stand in the freezer. After 7 d, yellow crystals of (I) suitable for X-ray diffraction analysis were isolated.
The H atoms of the hydroxy groups were found in a difference Fourier map (cf. Fig. 3) and their positional and isotropic displacement parameters were refined [O—H = 1.00 (7) Å Please check added text]. The other H atoms were placed in idealized positions and refined as riding, with C—H = 0.95–0.99 Å [Please check added text] and with Uiso(H) = 1.2Ueq(C). Since the molecule is not chiral and lacks any heavy atoms, Friedel pairs were merged before the refinement.
Data collection: CrysAlis CCD (Oxford Diffraction, 2006); cell refinement: CrysAlis RED (Oxford Diffraction, 2006); data reduction: CrysAlis RED; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: Stereochemical Workstation Operation Manual (Siemens, 1989) and ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXL97.
C19H22N2O2 | F(000) = 332 |
Mr = 310.39 | Dx = 1.248 Mg m−3 |
Monoclinic, Pc | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: P -2yc | Cell parameters from 5004 reflections |
a = 16.3631 (18) Å | θ = 2.3–24.0° |
b = 5.6428 (5) Å | µ = 0.08 mm−1 |
c = 9.1251 (8) Å | T = 100 K |
β = 101.418 (10)° | Block, colourless |
V = 825.88 (14) Å3 | 0.45 × 0.3 × 0.2 mm |
Z = 2 |
Kuma KM4 CCD four-circle diffractometer | 1484 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.033 |
Graphite monochromator | θmax = 28.2°, θmin = 3.6° |
Detector resolution: 8.1929 pixels mm-1 | h = −21→20 |
ω scans | k = −7→7 |
8735 measured reflections | l = −12→12 |
1868 independent reflections |
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)] = 0.063 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.113 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.15 | w = 1/[σ2(Fo2) + (0.01P)2 + 0.9022P] where P = (Fo2 + 2Fc2)/3 |
1868 reflections | (Δ/σ)max = 0.001 |
216 parameters | Δρmax = 0.36 e Å−3 |
2 restraints | Δρmin = −0.25 e Å−3 |
C19H22N2O2 | V = 825.88 (14) Å3 |
Mr = 310.39 | Z = 2 |
Monoclinic, Pc | Mo Kα radiation |
a = 16.3631 (18) Å | µ = 0.08 mm−1 |
b = 5.6428 (5) Å | T = 100 K |
c = 9.1251 (8) Å | 0.45 × 0.3 × 0.2 mm |
β = 101.418 (10)° |
Kuma KM4 CCD four-circle diffractometer | 1484 reflections with I > 2σ(I) |
8735 measured reflections | Rint = 0.033 |
1868 independent reflections |
R[F2 > 2σ(F2)] = 0.063 | 2 restraints |
wR(F2) = 0.113 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.15 | Δρmax = 0.36 e Å−3 |
1868 reflections | Δρmin = −0.25 e Å−3 |
216 parameters |
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. |
x | y | z | Uiso*/Ueq | ||
C1 | 0.6136 (3) | −0.3963 (8) | 1.0580 (5) | 0.0284 (10) | |
O1 | 0.5394 (2) | −0.4934 (6) | 0.9954 (4) | 0.0374 (8) | |
H1 | 0.509 (4) | −0.370 (13) | 0.926 (8) | 0.08 (2)* | |
C2 | 0.6654 (3) | −0.5159 (8) | 1.1735 (5) | 0.0331 (11) | |
H2 | 0.6486 | −0.6640 | 1.2072 | 0.040* | |
C3 | 0.7412 (3) | −0.4194 (9) | 1.2391 (5) | 0.0373 (11) | |
H3 | 0.7758 | −0.5008 | 1.3192 | 0.045* | |
C4 | 0.7677 (3) | −0.2056 (10) | 1.1901 (5) | 0.0387 (11) | |
H4 | 0.8205 | −0.1423 | 1.2350 | 0.046* | |
C5 | 0.7167 (3) | −0.0856 (8) | 1.0758 (5) | 0.0332 (10) | |
H5 | 0.7345 | 0.0615 | 1.0424 | 0.040* | |
C6 | 0.6386 (3) | −0.1786 (8) | 1.0082 (5) | 0.0268 (9) | |
C7 | 0.5854 (3) | −0.0465 (9) | 0.8896 (5) | 0.0311 (10) | |
H7 | 0.6039 | 0.1009 | 0.8577 | 0.037* | |
N8 | 0.5136 (2) | −0.1280 (8) | 0.8277 (4) | 0.0365 (10) | |
C9 | 0.4629 (3) | 0.0083 (11) | 0.7050 (6) | 0.0457 (14) | |
H9A | 0.4404 | −0.1003 | 0.6216 | 0.055* | |
H9B | 0.4988 | 0.1262 | 0.6678 | 0.055* | |
C10 | 0.3923 (3) | 0.1336 (8) | 0.7537 (5) | 0.0327 (9) | |
H10A | 0.4146 | 0.2360 | 0.8405 | 0.039* | |
H10B | 0.3548 | 0.0152 | 0.7860 | 0.039* | |
C11 | 0.3429 (3) | 0.2840 (8) | 0.6292 (5) | 0.0353 (9) | |
H11A | 0.3818 | 0.3880 | 0.5886 | 0.042* | |
H11B | 0.3152 | 0.1788 | 0.5475 | 0.042* | |
C12 | 0.2775 (3) | 0.4361 (8) | 0.6801 (5) | 0.0338 (9) | |
H12A | 0.2399 | 0.3322 | 0.7241 | 0.041* | |
H12B | 0.3055 | 0.5445 | 0.7596 | 0.041* | |
C13 | 0.2258 (3) | 0.5808 (8) | 0.5570 (5) | 0.0336 (10) | |
H13A | 0.1907 | 0.6941 | 0.6000 | 0.040* | |
H13B | 0.2627 | 0.6723 | 0.5042 | 0.040* | |
N14 | 0.1725 (2) | 0.4217 (7) | 0.4515 (4) | 0.0296 (8) | |
C15 | 0.0976 (3) | 0.4839 (8) | 0.3955 (4) | 0.0278 (9) | |
H15 | 0.0761 | 0.6274 | 0.4270 | 0.033* | |
C16 | 0.0450 (3) | 0.3362 (8) | 0.2837 (5) | 0.0254 (9) | |
C17 | 0.0739 (3) | 0.1168 (8) | 0.2413 (4) | 0.0267 (9) | |
O17 | 0.1500 (2) | 0.0338 (6) | 0.3046 (3) | 0.0335 (7) | |
H17 | 0.186 (4) | 0.165 (11) | 0.400 (7) | 0.067 (19)* | |
C18 | 0.0243 (3) | −0.0141 (8) | 0.1298 (5) | 0.0313 (10) | |
H18 | 0.0443 | −0.1598 | 0.0985 | 0.038* | |
C19 | −0.0544 (3) | 0.0656 (10) | 0.0634 (5) | 0.0386 (12) | |
H19 | −0.0881 | −0.0265 | −0.0126 | 0.046* | |
C20 | −0.0842 (3) | 0.2768 (9) | 0.1066 (6) | 0.0386 (11) | |
H20 | −0.1384 | 0.3303 | 0.0612 | 0.046* | |
C21 | −0.0346 (3) | 0.4115 (8) | 0.2171 (5) | 0.0306 (10) | |
H21 | −0.0553 | 0.5569 | 0.2476 | 0.037* |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.025 (2) | 0.029 (2) | 0.031 (2) | −0.0022 (19) | 0.0072 (18) | −0.0018 (17) |
O1 | 0.0334 (19) | 0.0325 (17) | 0.0444 (19) | −0.0096 (15) | 0.0029 (15) | 0.0004 (15) |
C2 | 0.035 (3) | 0.031 (2) | 0.034 (2) | 0.002 (2) | 0.010 (2) | 0.0076 (19) |
C3 | 0.035 (3) | 0.044 (3) | 0.032 (2) | 0.009 (2) | 0.003 (2) | 0.005 (2) |
C4 | 0.028 (2) | 0.044 (3) | 0.041 (3) | −0.004 (2) | 0.001 (2) | −0.007 (2) |
C5 | 0.028 (3) | 0.029 (2) | 0.043 (3) | −0.001 (2) | 0.0082 (19) | −0.003 (2) |
C6 | 0.025 (2) | 0.027 (2) | 0.029 (2) | −0.0001 (18) | 0.0081 (17) | −0.0011 (18) |
C7 | 0.027 (2) | 0.035 (2) | 0.033 (2) | 0.0039 (19) | 0.0115 (18) | 0.0086 (19) |
N8 | 0.031 (2) | 0.048 (2) | 0.030 (2) | 0.0078 (18) | 0.0059 (16) | 0.0085 (17) |
C9 | 0.032 (3) | 0.065 (4) | 0.040 (3) | 0.013 (2) | 0.008 (2) | 0.017 (2) |
C10 | 0.031 (2) | 0.036 (2) | 0.0306 (19) | 0.0002 (18) | 0.0045 (16) | −0.0007 (17) |
C11 | 0.031 (2) | 0.041 (2) | 0.033 (2) | 0.005 (2) | 0.0065 (17) | −0.0018 (18) |
C12 | 0.032 (2) | 0.037 (2) | 0.031 (2) | 0.0013 (19) | 0.0015 (17) | −0.0014 (18) |
C13 | 0.032 (2) | 0.034 (2) | 0.032 (2) | 0.000 (2) | 0.0022 (17) | −0.0079 (19) |
N14 | 0.026 (2) | 0.034 (2) | 0.0288 (18) | 0.0003 (16) | 0.0040 (14) | −0.0056 (15) |
C15 | 0.030 (2) | 0.029 (2) | 0.026 (2) | −0.0024 (18) | 0.0091 (17) | −0.0027 (17) |
C16 | 0.025 (2) | 0.023 (2) | 0.028 (2) | −0.0023 (18) | 0.0053 (17) | 0.0022 (17) |
C17 | 0.030 (2) | 0.024 (2) | 0.027 (2) | −0.0011 (18) | 0.0066 (18) | 0.0030 (16) |
O17 | 0.0319 (18) | 0.0338 (17) | 0.0340 (16) | 0.0085 (14) | 0.0046 (14) | −0.0012 (14) |
C18 | 0.038 (3) | 0.028 (2) | 0.029 (2) | −0.005 (2) | 0.0080 (19) | −0.0021 (18) |
C19 | 0.036 (3) | 0.042 (3) | 0.036 (2) | −0.010 (2) | 0.002 (2) | 0.001 (2) |
C20 | 0.026 (2) | 0.040 (3) | 0.046 (3) | −0.005 (2) | −0.002 (2) | 0.007 (2) |
C21 | 0.027 (3) | 0.026 (2) | 0.039 (3) | 0.0031 (19) | 0.0067 (19) | 0.0048 (19) |
C1—O1 | 1.351 (5) | C11—H11A | 0.9900 |
C1—C2 | 1.389 (6) | C11—H11B | 0.9900 |
C1—C6 | 1.398 (6) | C12—C13 | 1.506 (6) |
O1—H1 | 1.00 (7) | C12—H12A | 0.9900 |
C2—C3 | 1.378 (7) | C12—H12B | 0.9900 |
C2—H2 | 0.9500 | C13—N14 | 1.470 (5) |
C3—C4 | 1.386 (7) | C13—H13A | 0.9900 |
C3—H3 | 0.9500 | C13—H13B | 0.9900 |
C4—C5 | 1.378 (7) | N14—C15 | 1.279 (6) |
C4—H4 | 0.9500 | C15—C16 | 1.459 (6) |
C5—C6 | 1.406 (6) | C15—H15 | 0.9500 |
C5—H5 | 0.9500 | C16—C21 | 1.389 (6) |
C6—C7 | 1.454 (6) | C16—C17 | 1.407 (6) |
C7—N8 | 1.285 (6) | C17—O17 | 1.349 (5) |
C7—H7 | 0.9500 | C17—C18 | 1.383 (6) |
N8—C9 | 1.471 (6) | O17—H17 | 1.20 (6) |
C9—C10 | 1.495 (6) | C18—C19 | 1.385 (7) |
C9—H9A | 0.9900 | C18—H18 | 0.9500 |
C9—H9B | 0.9900 | C19—C20 | 1.375 (8) |
C10—C11 | 1.517 (5) | C19—H19 | 0.9500 |
C10—H10A | 0.9900 | C20—C21 | 1.389 (7) |
C10—H10B | 0.9900 | C20—H20 | 0.9500 |
C11—C12 | 1.514 (6) | C21—H21 | 0.9500 |
O1—C1—C2 | 119.0 (4) | C12—C11—H11B | 109.0 |
O1—C1—C6 | 121.0 (4) | C10—C11—H11B | 109.0 |
C2—C1—C6 | 120.0 (4) | H11A—C11—H11B | 107.8 |
C1—O1—H1 | 106 (4) | C13—C12—C11 | 113.9 (3) |
C3—C2—C1 | 119.9 (4) | C13—C12—H12A | 108.8 |
C3—C2—H2 | 120.1 | C11—C12—H12A | 108.8 |
C1—C2—H2 | 120.1 | C13—C12—H12B | 108.8 |
C2—C3—C4 | 121.1 (4) | C11—C12—H12B | 108.8 |
C2—C3—H3 | 119.5 | H12A—C12—H12B | 107.7 |
C4—C3—H3 | 119.5 | N14—C13—C12 | 109.3 (3) |
C5—C4—C3 | 119.4 (5) | N14—C13—H13A | 109.8 |
C5—C4—H4 | 120.3 | C12—C13—H13A | 109.8 |
C3—C4—H4 | 120.3 | N14—C13—H13B | 109.8 |
C4—C5—C6 | 120.7 (4) | C12—C13—H13B | 109.8 |
C4—C5—H5 | 119.7 | H13A—C13—H13B | 108.3 |
C6—C5—H5 | 119.7 | C15—N14—C13 | 119.4 (4) |
C1—C6—C5 | 119.0 (4) | N14—C15—C16 | 120.6 (4) |
C1—C6—C7 | 121.5 (4) | N14—C15—H15 | 119.7 |
C5—C6—C7 | 119.6 (4) | C16—C15—H15 | 119.7 |
N8—C7—C6 | 120.3 (4) | C21—C16—C17 | 119.0 (4) |
N8—C7—H7 | 119.8 | C21—C16—C15 | 120.2 (4) |
C6—C7—H7 | 119.8 | C17—C16—C15 | 120.7 (4) |
C7—N8—C9 | 118.4 (4) | O17—C17—C18 | 119.2 (4) |
N8—C9—C10 | 111.9 (4) | O17—C17—C16 | 121.3 (4) |
N8—C9—H9A | 109.2 | C18—C17—C16 | 119.5 (4) |
C10—C9—H9A | 109.2 | C17—O17—H17 | 112 (3) |
N8—C9—H9B | 109.2 | C17—C18—C19 | 120.5 (5) |
C10—C9—H9B | 109.2 | C17—C18—H18 | 119.7 |
H9A—C9—H9B | 107.9 | C19—C18—H18 | 119.7 |
C9—C10—C11 | 111.8 (3) | C20—C19—C18 | 120.5 (5) |
C9—C10—H10A | 109.3 | C20—C19—H19 | 119.7 |
C11—C10—H10A | 109.3 | C18—C19—H19 | 119.7 |
C9—C10—H10B | 109.3 | C19—C20—C21 | 119.5 (5) |
C11—C10—H10B | 109.3 | C19—C20—H20 | 120.2 |
H10A—C10—H10B | 107.9 | C21—C20—H20 | 120.2 |
C12—C11—C10 | 113.1 (3) | C20—C21—C16 | 120.9 (4) |
C12—C11—H11A | 109.0 | C20—C21—H21 | 119.6 |
C10—C11—H11A | 109.0 | C16—C21—H21 | 119.6 |
O1—C1—C2—C3 | −179.8 (4) | C10—C11—C12—C13 | −178.1 (4) |
C6—C1—C2—C3 | 0.2 (7) | C11—C12—C13—N14 | 68.4 (5) |
C1—C2—C3—C4 | −1.1 (8) | C12—C13—N14—C15 | 140.7 (4) |
C2—C3—C4—C5 | 1.2 (8) | C13—N14—C15—C16 | 176.3 (4) |
C3—C4—C5—C6 | −0.4 (8) | N14—C15—C16—C21 | −176.3 (4) |
O1—C1—C6—C5 | −179.4 (4) | N14—C15—C16—C17 | 3.5 (6) |
C2—C1—C6—C5 | 0.6 (6) | C21—C16—C17—O17 | −178.7 (4) |
O1—C1—C6—C7 | 1.2 (7) | C15—C16—C17—O17 | 1.5 (6) |
C2—C1—C6—C7 | −178.8 (4) | C21—C16—C17—C18 | 3.0 (6) |
C4—C5—C6—C1 | −0.5 (7) | C15—C16—C17—C18 | −176.8 (4) |
C4—C5—C6—C7 | 178.9 (4) | O17—C17—C18—C19 | 179.5 (4) |
C1—C6—C7—N8 | 0.1 (7) | C16—C17—C18—C19 | −2.1 (7) |
C5—C6—C7—N8 | −179.3 (4) | C17—C18—C19—C20 | 0.5 (7) |
C6—C7—N8—C9 | −178.2 (4) | C18—C19—C20—C21 | 0.4 (8) |
C7—N8—C9—C10 | −105.4 (5) | C19—C20—C21—C16 | 0.5 (8) |
N8—C9—C10—C11 | 177.1 (4) | C17—C16—C21—C20 | −2.2 (7) |
C9—C10—C11—C12 | −173.1 (4) | C15—C16—C21—C20 | 177.7 (4) |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···N8 | 1.00 (7) | 1.64 (7) | 2.552 (5) | 148 (6) |
O17—H17···N14 | 1.20 (6) | 1.55 (6) | 2.555 (5) | 136 (5) |
C13—H13A···O17i | 0.99 | 2.60 | 3.533 (6) | 156 |
Symmetry code: (i) x, −y+1, z+1/2. |
Experimental details
Crystal data | |
Chemical formula | C19H22N2O2 |
Mr | 310.39 |
Crystal system, space group | Monoclinic, Pc |
Temperature (K) | 100 |
a, b, c (Å) | 16.3631 (18), 5.6428 (5), 9.1251 (8) |
β (°) | 101.418 (10) |
V (Å3) | 825.88 (14) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 0.08 |
Crystal size (mm) | 0.45 × 0.3 × 0.2 |
Data collection | |
Diffractometer | Kuma KM4 CCD four-circle diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 8735, 1868, 1484 |
Rint | 0.033 |
(sin θ/λ)max (Å−1) | 0.664 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.063, 0.113, 1.15 |
No. of reflections | 1868 |
No. of parameters | 216 |
No. of restraints | 2 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.36, −0.25 |
Computer programs: CrysAlis CCD (Oxford Diffraction, 2006), CrysAlis RED (Oxford Diffraction, 2006), CrysAlis RED, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), Stereochemical Workstation Operation Manual (Siemens, 1989) and ORTEP-3 (Farrugia, 1997), SHELXL97.
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···N8 | 1.00 (7) | 1.64 (7) | 2.552 (5) | 148 (6) |
O17—H17···N14 | 1.20 (6) | 1.55 (6) | 2.555 (5) | 136 (5) |
C13—H13A···O17i | 0.99 | 2.60 | 3.533 (6) | 156.2 |
Symmetry code: (i) x, −y+1, z+1/2. |
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Much effort has been devoted in recent years to the design and synthesis of salicylaldimines and their metal complexes displaying binding properties toward deoxyribonucleic acid (DNA), with the aim of developing novel therapeutic agents which prevent the growth and replication of cancerous cells (Silvestri et al., 2007). Among the chemical moieties which have been used as part of chemotherapeutic agents are biogenic polyamines (Karigiannis & Papaioannou, 2000). The incorporation of biogenic polyamine fragments with flexibility and strong affinity for nucleic acids can prompt the emergence of new architectures with novel physicochemical properties and potential applications in technology and pharmaceutics. It seemed, therefore, to be of interest for us to synthesize the new salicylaldimine system derived from cadaverine, a biogenic amine.
The conformation of the title compound, (I), and its analogues can be described by the mutual orientation of three approximately planar fragments, A, B and C (Fig. 1): two salicylidene groups, for which the maximum deviations from the least-squares plane through nine atoms are 0.018 (3) Å for fragment A and 0.067 (3) Å for fragment B, and the central pentane chain (C), which adopts the exended conformation and is planar to within 0.044 (2) Å. The corresponding dihedral angles are: A/C 78.4 (2), B/C 62.0 (3) and A/B 55.4 (1)°. It should be noted that the conformation is not symmetrical. For fragment A, atom N8 is almost coplanar with the plane of the pentane chain [N8—C9—C10—C11 torsion angle 177.1 (3)°], while atom N14 is displaced by almost 1.5 Å [N14—C13—C12—C11 = 68.0 (4)°] from this plane.
In the analogues of (I) with different aliphatic chain lengths, two conformations are observed, depending on the even or odd number of atoms in the chain. This is related to the symmetry of the molecule, which is also a function of the number of atoms in the aliphatic chain. For the even-numbered aliphatic chains, the molecule can be centrosymmetric, with the centre of symmetry situated at the middle of the central C—C bond. In this case, due to the symmetry, the terminal ring planes have to be exactly parallel. This symmetry is realised in the analogues of (I) with n = 2 (Bresciani Pahor et al., 1978; in this case the symmetry is only approximate), n = 4 (Kennedy & Reglinski, 2001), n = 6 (Sheikhshoaie & Sharif, 2006) and n = 10 (Yu, 2006). The same symmetry is also observed for a dioxo-derivative of the n = 8 compound, 2,2-[3,6-dioxa-1,8-octanediylbis(nitrilomethylidene)]bisphenol (Etemadi et al., 2004).
When the number of C atoms in the chain is odd, the molecule cannot be centrosymmetric, and this is the case for (I), as well as for the molecule with n = 1, which lies on a twofold axis (Novitchi et al., 2002), and n = 3 (Elderman et al., 1991), with the molecule on a general position.
Interestingly, despite the different conformations, in three `intermediate-length' cases (n = 4, 5 and 6), the shape of the unit cell is similar. In particular, the b axes, which are parallel to the twofold screw axes for n = 4 and n = 6, are almost equal (ca 5.7 Å). In the case of (I), a pseudo 21 axis can be found along b (Fig. 2).
Short intramolecular O—H···N hydrogen bonds serve to close the almost planar six-membered rings [maximum deviations of 0.03 (3) and 0.06 (3) Å for fragments A and B, respectively]. The H atoms involved in these bonds (H1 and H17) are significantly displaced towards acceptor N atoms; the refined O—H distances are long in comparison with typical values. The reliability of these results is demonstrated by the difference Fourier maps (Fig. 3) calculated for a model without these H atoms.