organic compounds
3-Fluorosalicylaldoxime at 6.5 GPa
aCambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, England, and bSchool of Chemistry, The University of Edinburgh, King's Buildings, West Mains Road, Edinburgh EH9 3JJ, Scotland
*Correspondence e-mail: wood@ccdc.cam.ac.uk
3-Fluorosalicylaldoxime, C7H6FNO2, unlike many salicylaldoxime derivatives, forms a containing hydrogen-bonded chains rather than centrosymmetric hydrogen-bonded ring motifs. Each chain interacts with two chains above and two chains below via π–π stacking contacts [shortest centroid–centroid distance = 3.295 (1) Å]. This structure at 6.5 GPa represents the final point in a single-crystal compression study.
Related literature
For salicylaldoximes with bulky side groups which more commonly form hydrogen-bonded chains, see: Koziol & Kosturkiewicz (1984); Maurin (1994). For salicylaldoximes without bulky side groups that form chains, see: Wood et al. (2007a,b); Wood, Forgan, Parsons et al. (2006). For high pressure studies on salicylaldoximes, see: Wood et al. (2008, 2009); Wood, Forgan, Henderson et al. (2006). For specialized equipment used in the high pressure study, see: Merrill & Bassett (1974); Piermarini et al. (1975).
Experimental
Crystal data
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Refinement
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Data collection: APEX2 (Bruker, 2004); cell SAINT (Bruker, 2004); data reduction: SAINT; method used to solve structure: model taken from ambient pressure structure (Wood et al., 2007b); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003); molecular graphics: Mercury (Macrae et al., 2008); software used to prepare material for publication: CRYSTALS.
Supporting information
10.1107/S1600536809029043/tk2511sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536809029043/tk2511Isup2.hkl
All solvents and reagents were used as received from Aldrich and Fisher. 1H and 13C NMR were obtained using a Bruker AC250 spectrometer at ambient temperature. Chemical shifts (δ) are reported in p.p.m. relative to internal standards. Fast atom bombardment (FABMS) was carried out using a Kratos MS50TC spectrometer with a thioglycerol matrix. Analytical data was obtained from the University of St Andrews Microanalytical Service.
KOH (0.674 g, 10.20 mmol) and NH2OH.HCl (0.709 g, 10.20 mmol) were dissolved in EtOH, mixed thoroughly and a white KCl precipitate removed by filtration. 3-Fluorosalicylaldehyde (1.000 g, 7.14 mmol) was added to the filtrate, and the mixture refluxed for 3 h. The solvent was removed in vacuo, the residue redissolved in CHCl3, washed with water three times, and dried over MgSO4. The solvent was removed in vacuo to yield the crude product as a white powder (0.980 g, 88.5%). A pale-yellow block suitable for X-ray diffraction was grown by slow evaporation of a hexane/chloroform solution. (Anal. Calc. for C7H6FNO2: C, 54.2; H, 3.9; N, 9.0. Found: C, 54.3; H, 3.5; N, 9.2%); 1H NMR (250 MHz, CDCl3): δ(H) (p.p.m.) 6.78 (dt, 1H, ArHb), 6.90 (dd, 1H, ArHa), 7.05 (m, 1H, ArHc), 8.16 (s, 1H, CHN); 13C NMR (63 MHz, CDCl3) δ(C) (p.p.m.) 118.0 (aromatic CH), 118.7 (aromatic C-CHN), 119.8 (aromatic CH), 126.0 (aromatic CH), 145.9 (aromatic C—F), 152.8 (ArCHN), 153.6 (aromatic C—OH); FABMS m/z 156 (MH)+, 70%.
The high-pressure experiments were carried out using a Merrill-Bassett diamond anvil cell (half-opening angle 40°), equipped with brilliant-cut diamonds with 600 µm culets and a tungsten gasket (Merrill & Bassett, 1974). A 1:1 mixture of n-pentane and isopentane was used as a hydrostatic medium. Due to the high volatility of the n-pentane/isopentane solution, the cell was cooled in dry-ice prior to loading. A small ruby chip was also loaded into the cell as the pressure calibrant, with the ruby fluorescence method being used to measure the pressure (Piermarini et al., 1975).
Following data collection, an absorption correction was applied using the program SADABS (Sheldrick, (2006). The Tmax/Tmin ratio is larger than calculated on the basis of the crystal dimensions. However, multi-scan procedures (such as SADABS used in the present study) correct for all systematic errors that lead to disparities in the intensities of equivalent data. It is likely that the larger than expected range of transmission is accounted for by crystal decay or absorption by the high pressure cell.
The hydrogen atoms were located in a Fourier difference map. The positional and isotropic displacement parameters were then refined subject to restraints [C—H = 0.93 (2) Å, O—H = 0.82 (2) Å and Uiso(H) = 1.5 Ueq(C or O)]. In subsequent cycles of least-squares
all the Uiso(H) values were fixed and the H-atoms attached to C were constrained to ride on their parent atoms. H1 and H5 were refined subject to distance restraints equal to 0.84 (5) Å.In the absence of significant
effects, 316 Friedel pairs were averaged in the final refinement.The crystal quality was beginning to deteriorate by this pressure and the number of reflections collected also dropped. In order to deal with this, global vibration and thermal similarity restraints were applied to the model.
Data collection: APEX2 (Bruker, 2004); cell
SAINT (Bruker, 2004); data reduction: SAINT (Bruker, 2004); program(s) used to solve structure: model taken from ambient pressure structure (Wood et al., 2007b); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003); molecular graphics: Mercury (Macrae et al., 2008); software used to prepare material for publication: CRYSTALS (Betteridge et al., 2003).C7H6FNO2 | F(000) = 320 |
Mr = 155.13 | Dx = 1.978 Mg m−3 |
Orthorhombic, Pna21 | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: P 2c -2n | Cell parameters from 779 reflections |
a = 6.156 (2) Å | θ = 3–24° |
b = 9.751 (3) Å | µ = 0.17 mm−1 |
c = 8.6764 (18) Å | T = 298 K |
V = 520.8 (3) Å3 | Block, pale-yellow |
Z = 4 | 0.15 × 0.12 × 0.10 mm |
Bruker APEXII diffractometer | 233 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.074 |
ω scans | θmax = 27.0°, θmin = 3.1° |
Absorption correction: multi-scan (SADABS; Sheldrick, 2006) | h = −6→6 |
Tmin = 0.39, Tmax = 0.98 | k = −10→10 |
2715 measured reflections | l = −10→10 |
333 independent reflections |
Refinement on F2 | Hydrogen site location: inferred from neighbouring sites |
Least-squares matrix: full | H atoms treated by a mixture of independent and constrained refinement |
R[F2 > 2σ(F2)] = 0.036 | Method, part 1, Chebychev polynomial, (Watkin, 1994, Prince, 1982) [weight] = 1.0/[A0*T0(x) + A1*T1(x) ··· + An-1]*Tn-1(x)] where Ai are the Chebychev coefficients listed below and x = F /Fmax Method = Robust Weighting (Prince, 1982) W = [weight] * [1-(deltaF/6*sigmaF)2]2 Ai are 12.4 13.8 4.45 -0.254 |
wR(F2) = 0.049 | (Δ/σ)max < 0.001 |
S = 0.94 | Δρmax = 0.16 e Å−3 |
305 reflections | Δρmin = −0.18 e Å−3 |
106 parameters | Extinction correction: Larson (1970), Equation 22 |
94 restraints | Extinction coefficient: 119.189 |
Primary atom site location: structure-invariant direct methods |
C7H6FNO2 | V = 520.8 (3) Å3 |
Mr = 155.13 | Z = 4 |
Orthorhombic, Pna21 | Mo Kα radiation |
a = 6.156 (2) Å | µ = 0.17 mm−1 |
b = 9.751 (3) Å | T = 298 K |
c = 8.6764 (18) Å | 0.15 × 0.12 × 0.10 mm |
Bruker APEXII diffractometer | 333 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 2006) | 233 reflections with I > 2σ(I) |
Tmin = 0.39, Tmax = 0.98 | Rint = 0.074 |
2715 measured reflections |
R[F2 > 2σ(F2)] = 0.036 | 94 restraints |
wR(F2) = 0.049 | H atoms treated by a mixture of independent and constrained refinement |
S = 0.94 | Δρmax = 0.16 e Å−3 |
305 reflections | Δρmin = −0.18 e Å−3 |
106 parameters |
x | y | z | Uiso*/Ueq | ||
O1 | 0.4779 (9) | 0.1918 (6) | 0.9058 (5) | 0.0268 | |
N2 | 0.4588 (11) | 0.1849 (7) | 0.7440 (5) | 0.0247 | |
C3 | 0.4049 (11) | 0.3001 (7) | 0.6852 (7) | 0.0191 | |
C4 | 0.3841 (12) | 0.3034 (7) | 0.5185 (6) | 0.0157 | |
C5 | 0.3721 (11) | 0.1828 (9) | 0.4328 (5) | 0.0143 | |
O5 | 0.3858 (9) | 0.0571 (5) | 0.4956 (5) | 0.0214 | |
C6 | 0.3455 (12) | 0.1950 (9) | 0.2755 (6) | 0.0201 | |
F6 | 0.3356 (7) | 0.0740 (5) | 0.1972 (4) | 0.0265 | |
C7 | 0.3246 (12) | 0.3167 (8) | 0.2001 (7) | 0.0185 | |
C8 | 0.3431 (12) | 0.4332 (8) | 0.2861 (6) | 0.0189 | |
C9 | 0.3738 (11) | 0.4309 (8) | 0.4436 (6) | 0.0183 | |
H3 | 0.3781 | 0.3782 | 0.7440 | 0.0230* | |
H7 | 0.3014 | 0.3204 | 0.0958 | 0.0219* | |
H8 | 0.3343 | 0.5184 | 0.2363 | 0.0227* | |
H9 | 0.3877 | 0.5129 | 0.4979 | 0.0218* | |
H5 | 0.392 (14) | 0.059 (7) | 0.594 (4) | 0.0321* | |
H1 | 0.546 (15) | 0.114 (6) | 0.929 (7) | 0.0400* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.037 (5) | 0.032 (5) | 0.0119 (13) | 0.002 (2) | 0.0009 (19) | 0.003 (2) |
N2 | 0.035 (6) | 0.028 (4) | 0.0109 (15) | −0.001 (3) | 0.001 (2) | 0.008 (3) |
C3 | 0.017 (5) | 0.022 (4) | 0.0176 (17) | 0.000 (3) | 0.001 (3) | 0.001 (2) |
C4 | 0.010 (4) | 0.020 (2) | 0.0176 (18) | 0.001 (2) | −0.002 (3) | 0.0018 (16) |
C5 | 0.004 (4) | 0.020 (2) | 0.0189 (19) | 0.000 (2) | 0.000 (3) | 0.0014 (16) |
O5 | 0.023 (4) | 0.022 (2) | 0.019 (2) | 0.0014 (19) | 0.003 (2) | 0.0014 (18) |
C6 | 0.022 (6) | 0.020 (2) | 0.019 (2) | 0.000 (3) | −0.001 (3) | −0.0035 (16) |
F6 | 0.035 (3) | 0.023 (2) | 0.0215 (17) | 0.0051 (16) | 0.001 (2) | −0.0071 (18) |
C7 | 0.017 (5) | 0.024 (3) | 0.015 (2) | 0.002 (2) | 0.002 (3) | −0.0008 (18) |
C8 | 0.022 (5) | 0.017 (3) | 0.018 (2) | 0.000 (2) | 0.001 (3) | 0.004 (2) |
C9 | 0.022 (5) | 0.016 (3) | 0.017 (2) | 0.005 (2) | 0.002 (3) | −0.003 (2) |
O1—N2 | 1.410 (6) | O5—H5 | 0.86 (4) |
O1—H1 | 0.89 (4) | C6—F6 | 1.363 (9) |
N2—C3 | 1.278 (9) | C6—C7 | 1.361 (9) |
C3—C4 | 1.452 (8) | C7—C8 | 1.365 (10) |
C3—H3 | 0.932 | C7—H7 | 0.917 |
C4—C5 | 1.394 (9) | C8—C9 | 1.380 (8) |
C4—C9 | 1.404 (10) | C8—H8 | 0.938 |
C5—O5 | 1.345 (9) | C9—H9 | 0.932 |
C5—C6 | 1.380 (7) | ||
N2—O1—H1 | 103 (4) | C5—C6—F6 | 115.1 (7) |
O1—N2—C3 | 112.2 (7) | C5—C6—C7 | 124.2 (7) |
N2—C3—C4 | 116.2 (7) | F6—C6—C7 | 120.8 (5) |
N2—C3—H3 | 123.1 | C6—C7—C8 | 117.1 (6) |
C4—C3—H3 | 120.8 | C6—C7—H7 | 121.6 |
C3—C4—C5 | 121.2 (6) | C8—C7—H7 | 121.3 |
C3—C4—C9 | 119.0 (6) | C7—C8—C9 | 122.6 (8) |
C5—C4—C9 | 119.8 (5) | C7—C8—H8 | 118.8 |
C4—C5—O5 | 123.3 (4) | C9—C8—H8 | 118.6 |
C4—C5—C6 | 117.5 (7) | C4—C9—C8 | 118.6 (7) |
O5—C5—C6 | 119.1 (7) | C4—C9—H9 | 121.4 |
C5—O5—H5 | 113 (5) | C8—C9—H9 | 119.9 |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···O5i | 0.89 (7) | 1.81 (6) | 2.684 (8) | 165 (7) |
O5—H5···N2 | 0.85 (4) | 1.84 (6) | 2.530 (7) | 137 (6) |
Symmetry code: (i) −x+1, −y, z+1/2. |
Experimental details
Crystal data | |
Chemical formula | C7H6FNO2 |
Mr | 155.13 |
Crystal system, space group | Orthorhombic, Pna21 |
Temperature (K) | 298 |
a, b, c (Å) | 6.156 (2), 9.751 (3), 8.6764 (18) |
V (Å3) | 520.8 (3) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.17 |
Crystal size (mm) | 0.15 × 0.12 × 0.10 |
Data collection | |
Diffractometer | Bruker APEXII diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 2006) |
Tmin, Tmax | 0.39, 0.98 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 2715, 333, 233 |
Rint | 0.074 |
(sin θ/λ)max (Å−1) | 0.639 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.036, 0.049, 0.94 |
No. of reflections | 305 |
No. of parameters | 106 |
No. of restraints | 94 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.16, −0.18 |
Computer programs: APEX2 (Bruker, 2004), SAINT (Bruker, 2004), model taken from ambient pressure structure (Wood et al., 2007b), CRYSTALS (Betteridge et al., 2003), Mercury (Macrae et al., 2008).
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···O5i | 0.89 (7) | 1.81 (6) | 2.684 (8) | 165 (7) |
O5—H5···N2 | 0.85 (4) | 1.84 (6) | 2.530 (7) | 137 (6) |
Symmetry code: (i) −x+1, −y, z+1/2. |
Acknowledgements
We thank the Cambridge Crystallographic Data Centre, the University of Edinburgh and the EPSRC for funding.
References
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Hydrogen-bonded chain formation is more common for salicylaldoximes with bulky side-groups, e.g. Koziol & Kosturkiewicz (1984) & Maurin (1994). The structure of the title compound, 3-fluorosalicylaldoxime, (I), which has been previously reported at ambient-pressure/150 K (Wood et al., 2007a) is one of the exceptions to this trend along with salicylaldoxime-III (Wood, Forgan, Parsons et al., 2006) and 3-hydroxysalicylaldoxime (Wood et al., 2007b). Salicylaldoxime-I (Wood, Forgan, Henderson et al., 2006) and four of its 3-substituted derivatives (Wood et al., 2008), all of which form hydrogen-bonded dimers, have been studied under compression using a diamond-anvil high-pressure cell. This paper details the results of the continuation of the series to (I). The highest pressure structure is reported here but the ambient-pressure/ambient-temperature structure and further high pressure structures in between have been submitted to the CCDC as a private communication (Wood et al., 2009).
Compound (I) crystallizes with one molecule in the asymmetric unit in the space group Pna21 (Fig. 1). The molecule forms an intramolecular phenolic OH···N hydrogen bond [O5···N2 = 2.530 (7) Å] and an intermolecular oximic OH···O hydrogen bond [O1···O5 = 2.684 (8) Å] with a neighbouring molecule related by the 21 screw axis. These two interactions taken together form a secondary level C(5) chain running parallel to the crystallographic c axis.
The compression of the 3-fluorosalicylaldoxime structure is anisotropic (Fig. 2). It can be seen that the c-axis is the least compressible (decreases by 4.9% up to 6.5 GPa) and this direction also corresponds to the direction of the hydrogen-bonded chains in the crystal structure. The next least compressible direction is that of the crystallographic b axis (decreases by 7.8%), where the main interactions are H···F and H···H contacts between the chains. Finally, the direction that compresses the most up to 6.5 GPa (14.4%) is along the a axis which corresponds to the π-π stacking direction; closest contact = Cg()···Cg()i = 3.295 (1) Å for i: 0.5+x, 0.5-y, z.
Fig. 3 shows the compression of the π-π stacking contact geometry in comparison with equivalent interactions in other salicylaldoximes and with general stacking contacts found in the CSD. It can be seen that the compression follows the trend of the earlier oxime pressure studies (Wood et al., 2008) in that the interaction compresses to the edge of what is seen at ambient conditions in the CSD. In this experiment the crystal disintegrated when the pressure was increased further and this may be indicative that a destructive phase transition occurred.