organic compounds
3,3′-[(Cyclohexane-1,4-diyl)bis(azanediyl)]bis(cyclohex-2-en-1-one)
aChemistry and Environmental Division, Manchester Metropolitan University, Manchester M1 5GD, England, and bDepartment of Chemistry, University of Otago, PO Box 56, Dunedin, New Zealand
*Correspondence e-mail: jsimpson@alkali.otago.ac.nz
The title compound, C18H26N2O2, crystallizes with two half-molecules in the both lying about inversion centres situated at the centers of the cyclohexane rings. In the crystal, the two molecules are linked by a pair of N—H⋯O hydrogen bonds, forming an inversion dimer with an R22(18) ring motif; the dimers are linked by a second pair of N—H⋯O hydrogen bonds, enclosing an R22(18) ring motif, forming chains along [1-10] which are linked by bifurcated C—H⋯(O,O) hydrogen bonds, forming slabs parallel to the ab plane.
Keywords: crystal structure; cyclohexane-1,4-diamine; cyclohexane-1,3-dione; acetamide; hydrogen bonding; inversion dimers.
CCDC reference: 1440892
Structure description
The title compound, C18H26N2O2, was prepared by a direct condensation reaction between cyclohexane-1,4-diamine and cyclohexane-1,3-dione to afford the corresponding symmetrical diamine. It crystallizes with two half-molecules in the both lying about inversion centres situated at the centers of the cyclohexane rings. In the two molecules (1 and 2; Fig. 1) the central cyclohexane rings adopt chair conformations and are linked by NH bridges to two cyclohexenone rings. The latter each display envelope conformations with the central methylene C atoms of the CH2–CH2–CH2 segment as the flaps. The adjacent C=C and C—N bond distances of 1.3771 (16) and 1.3394 (15) Å, respectively, for molecule 1, and 1.3803 (15) and 1.3375 (14) Å, respectively, for molecule 2, indicate a considerable degree of delocalization across the C—N bonds. In the crystal, the two molecules are linked by a pair of N—H⋯O hydrogen bonds, forming an inversion dimer with an R22(18) ring motif (Table 1 and Fig. 2). These dimers are linked by a second pair of N—H⋯O hydrogen bonds, enclosing an R22(18) ring motif, forming chains along [10]; Table 1 and Fig. 2. The chains are linked by bifurcated C—H⋯(O,O) hydrogen bonds, forming slabs parallel to the ab plane (Table 1 and Fig. 3).
No structures of derivatives of cyclohexane-1,4-diamine with either cyclohexene or cyclohexane substituents on the N atoms appear in the literature. The closest relatives of the title compound in the Cambridge Structural Database (Groom & Allen, 2014) are found as Ru complexes of ligands that have either a phenyl ring on one N atom of the central cyclohexane-1,4-diamine unit and a benzyl substituent on the other (Samec et al., 2006) or alternatively benzyl substituents on both N atoms (Casey et al., 2007).
Synthesis and crystallization
A mixture of 114 mg (0.1 mmol) of cyclohexane-1,4-diamine and 112 mg (0.1 mmol) of cyclohexane-1,3-dione was refluxed at 352 K in 30 ml ethanol. The reaction was monitored by TLC, was complete after 5 h and left to cool to room temperature. The excess solvent was evaporated under vacuum and the resulting solid filtered off, dried and recrystallized from acetic acid (m.p. 593 K). Crystals suitable for X-ray data collection were grown by slow evaporation of a solution of acetic acid over four days at ambient temperature.
Refinement
Crystal data, data collection and structure .
details are summarized in Table 2
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Structural data
CCDC reference: 1440892
https://doi.org/10.1107/S2414314615021756/su4002sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314615021756/su4002Isup2.hkl
Supporting information file. DOI: https://doi.org/10.1107/S2414314615021756/su4002Isup3.cml
Data collection: CrysAlis PRO, Agilent (2013); cell
CrysAlis PRO, Agilent (2013); data reduction: CrysAlis PRO, Agilent (2013); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2014/7 (Sheldrick, 2015b) and TITAN2000 (Hunter & Simpson, 1999); molecular graphics: Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXL2014/7 (Sheldrick, 2015b), enCIFer (Allen et al., 2004), PLATON (Spek, 2009), publCIF (Westrip 2010), WinGX (Farrugia 2012).C18H26N2O2 | Z = 2 |
Mr = 302.41 | F(000) = 328 |
Triclinic, P1 | Dx = 1.216 Mg m−3 |
a = 8.1839 (2) Å | Cu Kα radiation, λ = 1.54184 Å |
b = 9.1461 (3) Å | Cell parameters from 9205 reflections |
c = 11.7669 (4) Å | θ = 4.0–74.1° |
α = 106.557 (3)° | µ = 0.63 mm−1 |
β = 97.687 (2)° | T = 100 K |
γ = 96.630 (2)° | Plate, orange |
V = 825.65 (5) Å3 | 0.54 × 0.35 × 0.07 mm |
Agilent SuperNova, Dual, Cu at zero, Atlas diffractometer | 3272 independent reflections |
Mirror monochromator | 3002 reflections with I > 2σ(I) |
Detector resolution: 5.1725 pixels mm-1 | Rint = 0.037 |
ω scans | θmax = 74.1°, θmin = 4.0° |
Absorption correction: multi-scan (CrysAlisPro; Agilent, 2013) | h = −9→10 |
Tmin = 0.845, Tmax = 1.000 | k = −11→11 |
12078 measured reflections | l = −14→14 |
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)] = 0.039 | Hydrogen site location: mixed |
wR(F2) = 0.103 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.10 | w = 1/[σ2(Fo2) + (0.0523P)2 + 0.2392P] where P = (Fo2 + 2Fc2)/3 |
3272 reflections | (Δ/σ)max < 0.001 |
219 parameters | Δρmax = 0.21 e Å−3 |
0 restraints | Δρmin = −0.30 e Å−3 |
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. |
x | y | z | Uiso*/Ueq | ||
O11' | 0.17860 (10) | 0.83044 (9) | 0.13490 (7) | 0.0202 (2) | |
C11' | 0.32063 (14) | 0.79299 (12) | 0.14231 (9) | 0.0170 (2) | |
C12' | 0.38277 (14) | 0.72110 (13) | 0.22838 (10) | 0.0177 (2) | |
H12' | 0.3140 | 0.7018 | 0.2832 | 0.021* | |
C13' | 0.53902 (14) | 0.67872 (12) | 0.23469 (9) | 0.0162 (2) | |
N11 | 0.59935 (12) | 0.60257 (11) | 0.30855 (9) | 0.0184 (2) | |
H11N | 0.708 (2) | 0.5950 (16) | 0.3150 (13) | 0.022* | |
C11 | 0.50682 (13) | 0.54283 (13) | 0.38859 (10) | 0.0165 (2) | |
H11 | 0.3873 | 0.5081 | 0.3483 | 0.020* | |
C12 | 0.57883 (15) | 0.40283 (13) | 0.40741 (10) | 0.0187 (2) | |
H12A | 0.6989 | 0.4342 | 0.4432 | 0.022* | |
H12B | 0.5690 | 0.3230 | 0.3286 | 0.022* | |
C16 | 0.51340 (15) | 0.66504 (13) | 0.50964 (10) | 0.0181 (2) | |
H161 | 0.6304 (17) | 0.7022 (15) | 0.5469 (12) | 0.016 (3)* | |
H162 | 0.4644 (18) | 0.7539 (16) | 0.4973 (13) | 0.022 (3)* | |
C14' | 0.65503 (14) | 0.71158 (13) | 0.15190 (10) | 0.0180 (2) | |
H14A | 0.6440 | 0.6187 | 0.0813 | 0.022* | |
H14B | 0.7719 | 0.7339 | 0.1950 | 0.022* | |
C15' | 0.61656 (15) | 0.84812 (14) | 0.10889 (10) | 0.0208 (3) | |
H15A | 0.6848 | 0.8584 | 0.0474 | 0.025* | |
H15B | 0.6452 | 0.9446 | 0.1774 | 0.025* | |
C16' | 0.43164 (15) | 0.82319 (14) | 0.05536 (11) | 0.0224 (3) | |
H16C | 0.4059 | 0.9159 | 0.0335 | 0.027* | |
H16D | 0.4072 | 0.7342 | −0.0192 | 0.027* | |
O21' | 0.94724 (10) | 0.59292 (9) | 0.34302 (7) | 0.01825 (19) | |
C21' | 0.98783 (13) | 0.47129 (12) | 0.28124 (9) | 0.0147 (2) | |
C22' | 1.01924 (13) | 0.34896 (12) | 0.32908 (9) | 0.0154 (2) | |
H22' | 1.0180 | 0.3630 | 0.4121 | 0.018* | |
C23' | 1.05146 (13) | 0.21036 (12) | 0.25822 (9) | 0.0148 (2) | |
N21 | 1.07308 (12) | 0.08956 (11) | 0.29800 (8) | 0.0164 (2) | |
H21N | 1.0982 (17) | 0.0065 (17) | 0.2477 (13) | 0.020* | |
C21 | 1.05449 (14) | 0.08363 (12) | 0.41861 (9) | 0.0149 (2) | |
H21 | 1.1054 | 0.1860 | 0.4782 | 0.018* | |
C22 | 1.14853 (14) | −0.03970 (12) | 0.44659 (9) | 0.0162 (2) | |
H22A | 1.2683 | −0.0137 | 0.4433 | 0.019* | |
H22B | 1.1038 | −0.1409 | 0.3854 | 0.019* | |
C26 | 0.86983 (14) | 0.05044 (13) | 0.42843 (10) | 0.0165 (2) | |
H261 | 0.8108 (17) | 0.1327 (16) | 0.4127 (13) | 0.020* | |
H262 | 0.8183 (17) | −0.0501 (16) | 0.3656 (13) | 0.020* | |
C24' | 1.06061 (15) | 0.18458 (12) | 0.12708 (9) | 0.0173 (2) | |
H24A | 0.9503 | 0.1330 | 0.0778 | 0.021* | |
H24B | 1.1429 | 0.1152 | 0.1038 | 0.021* | |
C25' | 1.11107 (14) | 0.33592 (13) | 0.10069 (9) | 0.0175 (2) | |
H25A | 1.2290 | 0.3788 | 0.1382 | 0.021* | |
H25B | 1.1011 | 0.3163 | 0.0127 | 0.021* | |
C26' | 0.99899 (14) | 0.45218 (12) | 0.15038 (10) | 0.0174 (2) | |
H26A | 1.0428 | 0.5537 | 0.1425 | 0.021* | |
H26B | 0.8854 | 0.4178 | 0.1015 | 0.021* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O11' | 0.0246 (4) | 0.0202 (4) | 0.0159 (4) | 0.0097 (3) | 0.0022 (3) | 0.0037 (3) |
C11' | 0.0223 (5) | 0.0138 (5) | 0.0131 (5) | 0.0037 (4) | 0.0020 (4) | 0.0016 (4) |
C12' | 0.0214 (5) | 0.0193 (6) | 0.0148 (5) | 0.0051 (4) | 0.0056 (4) | 0.0073 (4) |
C13' | 0.0218 (5) | 0.0148 (5) | 0.0130 (5) | 0.0031 (4) | 0.0046 (4) | 0.0050 (4) |
N11 | 0.0185 (5) | 0.0239 (5) | 0.0185 (5) | 0.0067 (4) | 0.0064 (4) | 0.0126 (4) |
C11 | 0.0173 (5) | 0.0198 (6) | 0.0160 (5) | 0.0034 (4) | 0.0043 (4) | 0.0103 (4) |
C12 | 0.0237 (6) | 0.0194 (6) | 0.0167 (5) | 0.0068 (4) | 0.0075 (4) | 0.0085 (4) |
C16 | 0.0223 (6) | 0.0173 (5) | 0.0180 (5) | 0.0045 (4) | 0.0051 (4) | 0.0091 (4) |
C14' | 0.0218 (5) | 0.0198 (6) | 0.0159 (5) | 0.0059 (4) | 0.0074 (4) | 0.0081 (4) |
C15' | 0.0239 (6) | 0.0225 (6) | 0.0208 (5) | 0.0049 (5) | 0.0069 (4) | 0.0123 (5) |
C16' | 0.0266 (6) | 0.0264 (6) | 0.0189 (5) | 0.0062 (5) | 0.0046 (5) | 0.0133 (5) |
O21' | 0.0216 (4) | 0.0141 (4) | 0.0189 (4) | 0.0054 (3) | 0.0055 (3) | 0.0029 (3) |
C21' | 0.0141 (5) | 0.0138 (5) | 0.0149 (5) | 0.0012 (4) | 0.0023 (4) | 0.0028 (4) |
C22' | 0.0197 (5) | 0.0156 (5) | 0.0115 (5) | 0.0036 (4) | 0.0047 (4) | 0.0039 (4) |
C23' | 0.0173 (5) | 0.0145 (5) | 0.0125 (5) | 0.0023 (4) | 0.0034 (4) | 0.0038 (4) |
N21 | 0.0267 (5) | 0.0130 (5) | 0.0108 (4) | 0.0062 (4) | 0.0066 (4) | 0.0031 (4) |
C21 | 0.0211 (5) | 0.0133 (5) | 0.0109 (5) | 0.0034 (4) | 0.0043 (4) | 0.0038 (4) |
C22 | 0.0197 (5) | 0.0160 (5) | 0.0150 (5) | 0.0046 (4) | 0.0056 (4) | 0.0062 (4) |
C26 | 0.0192 (5) | 0.0169 (5) | 0.0147 (5) | 0.0041 (4) | 0.0027 (4) | 0.0066 (4) |
C24' | 0.0263 (6) | 0.0153 (5) | 0.0108 (5) | 0.0063 (4) | 0.0054 (4) | 0.0028 (4) |
C25' | 0.0248 (6) | 0.0181 (5) | 0.0119 (5) | 0.0056 (4) | 0.0062 (4) | 0.0057 (4) |
C26' | 0.0229 (6) | 0.0157 (5) | 0.0144 (5) | 0.0047 (4) | 0.0024 (4) | 0.0057 (4) |
O11'—C11' | 1.2481 (14) | O21'—C21' | 1.2512 (13) |
C11'—C12' | 1.4267 (15) | C21'—C22' | 1.4217 (15) |
C11'—C16' | 1.5167 (15) | C21'—C26' | 1.5159 (14) |
C12'—C13' | 1.3771 (16) | C22'—C23' | 1.3803 (15) |
C12'—H12' | 0.9500 | C22'—H22' | 0.9500 |
C13'—N11 | 1.3394 (15) | C23'—N21 | 1.3375 (14) |
C13'—C14' | 1.5131 (15) | C23'—C24' | 1.5067 (14) |
N11—C11 | 1.4654 (13) | N21—C21 | 1.4629 (13) |
N11—H11N | 0.896 (16) | N21—H21N | 0.884 (15) |
C11—C12 | 1.5287 (15) | C21—C22 | 1.5223 (15) |
C11—C16 | 1.5295 (16) | C21—C26 | 1.5330 (15) |
C11—H11 | 1.0000 | C21—H21 | 1.0000 |
C12—C16i | 1.5303 (14) | C22—C26ii | 1.5274 (14) |
C12—H12A | 0.9900 | C22—H22A | 0.9900 |
C12—H12B | 0.9900 | C22—H22B | 0.9900 |
C16—C12i | 1.5303 (14) | C26—C22ii | 1.5274 (14) |
C16—H161 | 0.976 (14) | C26—H261 | 0.987 (15) |
C16—H162 | 0.984 (15) | C26—H262 | 1.005 (14) |
C14'—C15' | 1.5241 (15) | C24'—C25' | 1.5264 (15) |
C14'—H14A | 0.9900 | C24'—H24A | 0.9900 |
C14'—H14B | 0.9900 | C24'—H24B | 0.9900 |
C15'—C16' | 1.5240 (17) | C25'—C26' | 1.5259 (15) |
C15'—H15A | 0.9900 | C25'—H25A | 0.9900 |
C15'—H15B | 0.9900 | C25'—H25B | 0.9900 |
C16'—H16C | 0.9900 | C26'—H26A | 0.9900 |
C16'—H16D | 0.9900 | C26'—H26B | 0.9900 |
O11'—C11'—C12' | 122.81 (10) | O21'—C21'—C22' | 122.03 (10) |
O11'—C11'—C16' | 118.83 (10) | O21'—C21'—C26' | 118.86 (9) |
C12'—C11'—C16' | 118.36 (10) | C22'—C21'—C26' | 119.09 (9) |
C13'—C12'—C11' | 122.23 (10) | C23'—C22'—C21' | 121.82 (10) |
C13'—C12'—H12' | 118.9 | C23'—C22'—H22' | 119.1 |
C11'—C12'—H12' | 118.9 | C21'—C22'—H22' | 119.1 |
N11—C13'—C12' | 124.62 (10) | N21—C23'—C22' | 123.77 (10) |
N11—C13'—C14' | 114.55 (10) | N21—C23'—C24' | 115.16 (9) |
C12'—C13'—C14' | 120.79 (10) | C22'—C23'—C24' | 121.05 (10) |
C13'—N11—C11 | 125.64 (10) | C23'—N21—C21 | 124.53 (9) |
C13'—N11—H11N | 117.4 (9) | C23'—N21—H21N | 118.1 (9) |
C11—N11—H11N | 116.7 (9) | C21—N21—H21N | 117.4 (9) |
N11—C11—C12 | 108.57 (9) | N21—C21—C22 | 108.82 (9) |
N11—C11—C16 | 112.30 (9) | N21—C21—C26 | 111.15 (9) |
C12—C11—C16 | 110.44 (9) | C22—C21—C26 | 110.89 (9) |
N11—C11—H11 | 108.5 | N21—C21—H21 | 108.6 |
C12—C11—H11 | 108.5 | C22—C21—H21 | 108.6 |
C16—C11—H11 | 108.5 | C26—C21—H21 | 108.6 |
C11—C12—C16i | 110.98 (9) | C21—C22—C26ii | 110.27 (9) |
C11—C12—H12A | 109.4 | C21—C22—H22A | 109.6 |
C16i—C12—H12A | 109.4 | C26ii—C22—H22A | 109.6 |
C11—C12—H12B | 109.4 | C21—C22—H22B | 109.6 |
C16i—C12—H12B | 109.4 | C26ii—C22—H22B | 109.6 |
H12A—C12—H12B | 108.0 | H22A—C22—H22B | 108.1 |
C11—C16—C12i | 110.90 (9) | C22ii—C26—C21 | 110.87 (9) |
C11—C16—H161 | 108.2 (8) | C22ii—C26—H261 | 109.2 (8) |
C12i—C16—H161 | 109.8 (8) | C21—C26—H261 | 110.3 (8) |
C11—C16—H162 | 110.2 (8) | C22ii—C26—H262 | 109.8 (8) |
C12i—C16—H162 | 110.0 (8) | C21—C26—H262 | 108.1 (8) |
H161—C16—H162 | 107.6 (11) | H261—C26—H262 | 108.5 (11) |
C13'—C14'—C15' | 111.81 (9) | C23'—C24'—C25' | 111.93 (9) |
C13'—C14'—H14A | 109.3 | C23'—C24'—H24A | 109.2 |
C15'—C14'—H14A | 109.3 | C25'—C24'—H24A | 109.2 |
C13'—C14'—H14B | 109.3 | C23'—C24'—H24B | 109.2 |
C15'—C14'—H14B | 109.3 | C25'—C24'—H24B | 109.2 |
H14A—C14'—H14B | 107.9 | H24A—C24'—H24B | 107.9 |
C14'—C15'—C16' | 109.70 (9) | C26'—C25'—C24' | 110.10 (9) |
C14'—C15'—H15A | 109.7 | C26'—C25'—H25A | 109.6 |
C16'—C15'—H15A | 109.7 | C24'—C25'—H25A | 109.6 |
C14'—C15'—H15B | 109.7 | C26'—C25'—H25B | 109.6 |
C16'—C15'—H15B | 109.7 | C24'—C25'—H25B | 109.6 |
H15A—C15'—H15B | 108.2 | H25A—C25'—H25B | 108.2 |
C11'—C16'—C15' | 112.08 (9) | C21'—C26'—C25' | 112.89 (9) |
C11'—C16'—H16C | 109.2 | C21'—C26'—H26A | 109.0 |
C15'—C16'—H16C | 109.2 | C25'—C26'—H26A | 109.0 |
C11'—C16'—H16D | 109.2 | C21'—C26'—H26B | 109.0 |
C15'—C16'—H16D | 109.2 | C25'—C26'—H26B | 109.0 |
H16C—C16'—H16D | 107.9 | H26A—C26'—H26B | 107.8 |
O11'—C11'—C12'—C13' | 179.23 (10) | O21'—C21'—C22'—C23' | 174.96 (10) |
C16'—C11'—C12'—C13' | −0.02 (16) | C26'—C21'—C22'—C23' | −3.27 (16) |
C11'—C12'—C13'—N11 | −175.70 (10) | C21'—C22'—C23'—N21 | −176.41 (10) |
C11'—C12'—C13'—C14' | 1.92 (17) | C21'—C22'—C23'—C24' | 2.13 (16) |
C12'—C13'—N11—C11 | 4.30 (18) | C22'—C23'—N21—C21 | 4.36 (17) |
C14'—C13'—N11—C11 | −173.45 (10) | C24'—C23'—N21—C21 | −174.25 (9) |
C13'—N11—C11—C12 | 152.07 (11) | C23'—N21—C21—C22 | −159.15 (10) |
C13'—N11—C11—C16 | −85.51 (13) | C23'—N21—C21—C26 | 78.46 (13) |
N11—C11—C12—C16i | −179.88 (9) | N21—C21—C22—C26ii | −179.35 (8) |
C16—C11—C12—C16i | 56.59 (13) | C26—C21—C22—C26ii | −56.80 (12) |
N11—C11—C16—C12i | −177.89 (9) | N21—C21—C26—C22ii | 178.33 (9) |
C12—C11—C16—C12i | −56.54 (13) | C22—C21—C26—C22ii | 57.15 (12) |
N11—C13'—C14'—C15' | −156.94 (10) | N21—C23'—C24'—C25' | −155.02 (10) |
C12'—C13'—C14'—C15' | 25.22 (14) | C22'—C23'—C24'—C25' | 26.32 (14) |
C13'—C14'—C15'—C16' | −52.41 (13) | C23'—C24'—C25'—C26' | −51.78 (12) |
O11'—C11'—C16'—C15' | 151.78 (10) | O21'—C21'—C26'—C25' | 157.43 (10) |
C12'—C11'—C16'—C15' | −28.93 (14) | C22'—C21'—C26'—C25' | −24.28 (14) |
C14'—C15'—C16'—C11' | 54.51 (13) | C24'—C25'—C26'—C21' | 51.07 (12) |
Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) −x+2, −y, −z+1. |
D—H···A | D—H | H···A | D···A | D—H···A |
N11—H11N···O21′ | 0.896 (16) | 1.944 (16) | 2.8369 (13) | 174.8 (14) |
N21—H21N···O11′iii | 0.884 (15) | 2.012 (15) | 2.8930 (13) | 174.1 (13) |
C21—H21···O21′iv | 1.00 | 2.59 | 3.4511 (13) | 144 |
C22—H22B···O21′v | 0.99 | 2.50 | 3.3675 (14) | 147 |
Symmetry codes: (iii) x+1, y−1, z; (iv) −x+2, −y+1, −z+1; (v) x, y−1, z. |
Acknowledgements
We thank the University of Otago for the purchase of the diffractometer and the Chemistry Department, University of Otago, for support of the work of JS. SKM thanks Dr Alaa F. Mohamed, National Organization for Drug Control and Research (NODCAR), Egypt, for providing the necessary chemicals.
References
Agilent (2013). CrysAlis PRO. Agilent Technologies, Yarnton, England. Google Scholar
Allen, F. H., Johnson, O., Shields, G. P., Smith, B. R. & Towler, M. (2004). J. Appl. Cryst. 37, 335–338. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
Casey, C. P., Clark, T. B. & Guzei, I. A. (2007). J. Am. Chem. Soc. 129, 11821–11827. Web of Science CSD CrossRef PubMed CAS Google Scholar
Farrugia, L. J. (2012). J. Appl. Cryst. 45, 849–854. Web of Science CrossRef CAS IUCr Journals Google Scholar
Groom, C. R. & Allen, F. H. (2014). Angew. Chem. Int. Ed. 53, 662–671. Web of Science CSD CrossRef CAS Google Scholar
Hunter, K. A. & Simpson, J. (1999). TITAN2000. University of Otago, New Zealand. Google Scholar
Macrae, C. F., Bruno, I. J., Chisholm, J. A., Edgington, P. R., McCabe, P., Pidcock, E., Rodriguez-Monge, L., Taylor, R., van de Streek, J. & Wood, P. A. (2008). J. Appl. Cryst. 41, 466–470. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
Samec, J. S. M., Éll, A. H., Åberg, J. B., Privalov, T., Eriksson, L. & Bäckvall, J.-E. (2006). J. Am. Chem. Soc. 128, 14293–14305. Web of Science CSD CrossRef PubMed CAS Google Scholar
Sheldrick, G. M. (2015a). Acta Cryst. A71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Sheldrick, G. M. (2015b). Acta Cryst. C71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Spek, A. L. (2009). Acta Cryst. D65, 148–155. Web of Science CrossRef CAS IUCr Journals Google Scholar
Westrip, S. P. (2010). J. Appl. Cryst. 43, 920–925. Web of Science CrossRef CAS IUCr Journals Google Scholar
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