research communications
and Hirshfeld surface analysis of 1,3-diethynyladamantane
aInorganic Chemistry Department, National Taras Shevchenko University of Kyiv, Volodymyrska Str. 64/13, 01601 Kyiv, Ukraine
*Correspondence e-mail: dk@univ.kiev.ua
The title compound, C14H16, exhibits exceptionally weak intermolecular C—H⋯π hydrogen bonding of the ethynyl groups, with the corresponding H⋯π separations [2.91 (2) and 3.12 (2) Å] exceeding normal vdW distances. This bonding complements distal contacts of the CH (aliphatic)⋯π type [H⋯π = 3.12 (2)–3.14 (2) Å] to sustain supramolecular layers. Hirshfeld surface analysis of the title compound suggests a relatively limited significance of the C⋯H/H⋯C contacts to the crystal packing (24.6%) and a major contribution from H⋯H contacts accounting 74.9% to the entire surface.
Keywords: crystal structure; C—H⋯π hydrogen bond; Hirschfeld surface analysis; adamantane; terminal alkyne.
CCDC reference: 2000259
1. Chemical context
Terminal π interactions (Nishio, 2004). The latter dominate the of acetylene (McMullan et al., 1992). In the case of polyfunctional species, the significance of such C—H⋯π interactions is rather low, since only 13.3% of related structures exhibit this kind of bonding (Allen et al., 2013). This may be associated with the specific geometry demands that concern an orthogonal orientation of the donor and acceptor alkyne groups. It is not surprising that examples for C—H⋯π-driven self-assembly of terminal diynes are particularly rare. These examples are restricted to a few structures of hydrocarbons lacking stronger supramolecular interactions. Most of the literature precedents, such as 1,4-diethynylbenzene (Weiss et al., 1997), 1,4-diethynylcubane (Eaton et al., 1994) and α,ω-octa- and decadiynes (Bond, 2002) feature collinear orientations of the ethynyl groups within the molecules, which are beneficial for the generation of the simplest of supramolecular patterns. In the case of angular diynes, the demands of dense molecular packing may be less compatible with highly directional orthogonal interactions of C≡CH (donor) and C≡CH (acceptor) groups. One can anticipate the essential distortion and weakening (if not elimination at all) of the C—H⋯π bonding.
provide self-complementary hydrogen-bond donor and acceptor functionality to sustain weak C—H⋯In this context, we have examined the angular compound 1,3-diethynyladamantane and report its et al., 2020).
herein. The crystal packing of 1,3-disubstituted adamantanes also recently attracted attention in the context of and the formation of plastic phases (Negrier2. Structural commentary
The molecular structure of the title compound is shown in Fig. 1. The bonds lengths in the carbocyclic framework [1.5213 (19)–1.5418 (15) Å; mean C—C = 1.532 (2) Å] are typical for adamantane derivatives, for example 1,3-diphenyladamantane with mean C—C = 1.530 (6) Å (Tukada & Mochizuki, 2003). At the same time, these bonds are slightly shorter than those observed for an adamantane-1,3-diyl core bearing two electron-donor groups, such as 1,3-dimethyl- [mean C—C = 1.562 (6) Å] and 1,3-dihydroxyadamantanes [mean C—C = 1.563 (2) Å] (Negrier et al., 2020). The alkyne fragments C5—C1≡C2 and C7—C3≡C4 are linear, with the corresponding bond angles being 177.47 (13) and 178.31 (12)°, respectively. The geometries of these fragments [C1≡C2 = 1.1763 (17); C3≡C4 = 1.1812 (19) Å and C1—C5 = 1.4708 (15), C3—C7 = 1.4673 (16) Å] are consistent with the data for non-conjugated terminal for example 1,7-octadiyne [1.186 (2) and 1.464 (2) Å, respectively; Bond, 2002].
3. Supramolecular features
Hydrogen-bond interactions of the alkyne groups are exceptionally weak and there are no H⋯π separations (π is defined as a centroid of the triple-bonded atoms) falling into the interval of 2.39–2.90 Å suggested by Allen et al. (2013). Even the shortest related contact [C1C2H⋯C4i = 2.905 (18) Å; symmetry code: (i) x, − − y, + z], is longer than the normal vdW separation of 2.87 Å (Zefirov, 1997). In particular, the distal interactions of the C3≡C4H donors [H⋯π = 3.12 (2) Å] do not differ in geometry from a set of H⋯π contacts established by the methylene (C6 and C10) and methyne (C12) groups (Table 1). Both ethynyl groups are donors of such CH⋯π bonding, whereas their acceptor functions are not uniform. The C3≡C4H groups accept two C≡CH⋯π bonds and establish an additional comparable contact with an aliphatic donor, while the C1≡C2H groups maintain only two distal contacts with the aliphatic CH portion. Mutual bonding of C3≡C4H groups [H⋯π = 3.12 (2) Å; symmetry code: (ii) −x, − + y, − − z] as well as contacts with the methyne groups C12H⋯Cg(C1C2)v [H⋯π = 3.14 (2) Å; Cg is a group centroid; symmetry code: (v) x, 1 + y, z] link the molecules into zigzag chains along the b-axis direction (Fig. 2). These aggregate into layers, which are parallel to the bc plane with a set of the above bonds involving C1≡C2H donors and C3≡C4H (x, − − y, + z) acceptors. The shortest contacts between successive layers concern interactions involving the methylene groups C10H⋯Cg(C1C2)iv [H⋯π = 3.14 (2) Å; symmetry code: (iv) 1 − x, + y, − z; Fig. 3].
The C≡CH⋯π geometries reported here are only approximately comparable with the parameters of much stronger and more directional supramolecular bonding in 1,4-diethynylbenzene [H⋯π = 2.72 Å; C—H⋯π = 175°] (Weiss et al., 1997). More important is that even very weak and bifurcated C—H⋯π bonds in α,ω-octa- and decadiynes [H⋯π = 2.99–3.03 Å; Bond, 2002] are superior to those reported here based upon single and well-defined acceptors. The weakness of the C≡CH⋯π bonds in the title structure and their limited significance are best illustrated by their peer interplay and competition with aliphatic C–H⋯π contacts, with the corresponding interatomic separations exceeding the sum of vdW radii.
4. Hirshfeld analysis
The supramolecular interactions in the title structure have been further investigated and visualized by Hirshfeld surface analysis (Spackman & Byrom, 1997; McKinnon et al., 2004; Hirshfeld, 1977) performed with CrystalExplorer17 (Turner et al., 2017). The Hirshfeld surface of the molecule, mapped over dnorm in the color range 0.0957 to 1.3378 a.u., indicates only a set of normal vdW contacts (white regions) corresponding to the closest interactions (Fig. 4). The two-dimensional fingerprint plot is appreciably reminiscent of the one for adamantane itself (Spackman & McKinnon, 2002), but accompanied by two additional diffuse features appearing as wings at the top left and bottom right of the plot (Fig. 5). These wings correspond to a series of C⋯H/H⋯C contacts. Nevertheless, H⋯H contacts (the shortest ones are at the de = di = 1.2 Å level) are by far the major contributors (74.9%) to the entire surface, while the fraction of C⋯H/H⋯C contacts accounts for only 24.6%. The latter value may be compared with contributions of 40.0 and 32.4% calculated for α,ω-octa- and decadiynes (Bond, 2002) and this significant suppression of the C⋯H/H⋯C contacts is in line with the very weak C—H⋯π bonding in the title structure, as described above. There are no stacking interactions of the ethynyl groups: the contribution of the C⋯C contacts to the entire surface does not exceed 0.5%.
5. Synthesis and crystallization
The title compound was synthesized in a three-step reaction sequence starting with selective dibromination of adamantane (Degtyarenko et al., 2014). The reaction product was crystallized from methanol.
6. Refinement
Crystal data, data collection and structure . The non-H atoms were refined with anisotropic displacement parameters. All hydrogen atoms were located in a difference maps and then freely refined with isotropic displacement parameters [C—H (ethynyl) = 0.927 (19) and 0.96 (2) Å; C—H (methyne) = 0.967 (16) and 0.971 (16) Å; C—H (methylene) = 0.952 (14)–1.013 (19) Å].
details are summarized in Table 2
|
Supporting information
CCDC reference: 2000259
https://doi.org/10.1107/S2056989020005964/lh5958sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989020005964/lh5958Isup2.hkl
Supporting information file. DOI: https://doi.org/10.1107/S2056989020005964/lh5958Isup3.cml
Data collection: IPDS Software (Stoe & Cie, 2000); cell
IPDS Software (Stoe & Cie, 2000); data reduction: IPDS Software (Stoe & Cie, 2000); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2018/1 (Sheldrick, 2015); molecular graphics: DIAMOND (Brandenburg, 1999); software used to prepare material for publication: WinGX (Farrugia, 2012).C14H16 | F(000) = 400 |
Mr = 184.27 | Dx = 1.123 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
a = 11.3214 (9) Å | Cell parameters from 8000 reflections |
b = 6.7426 (6) Å | θ = 3.3–28.0° |
c = 14.9478 (12) Å | µ = 0.06 mm−1 |
β = 107.234 (9)° | T = 213 K |
V = 1089.82 (16) Å3 | Prism, colorless |
Z = 4 | 0.26 × 0.23 × 0.20 mm |
Stoe IPDS diffractometer | Rint = 0.039 |
Radiation source: fine-focus sealed tube | θmax = 28.0°, θmin = 3.3° |
φ oscillation scans | h = −14→14 |
9458 measured reflections | k = −8→8 |
2593 independent reflections | l = −19→19 |
1885 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)] = 0.044 | Hydrogen site location: difference Fourier map |
wR(F2) = 0.124 | All H-atom parameters refined |
S = 0.99 | w = 1/[σ2(Fo2) + (0.086P)2] where P = (Fo2 + 2Fc2)/3 |
2593 reflections | (Δ/σ)max < 0.001 |
191 parameters | Δρmax = 0.29 e Å−3 |
0 restraints | Δρmin = −0.17 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 | ||
C1 | 0.28206 (10) | −0.04337 (17) | 0.21845 (8) | 0.0389 (3) | |
C2 | 0.27667 (12) | −0.1572 (2) | 0.27676 (9) | 0.0504 (3) | |
C3 | 0.11946 (10) | 0.07256 (18) | −0.11933 (8) | 0.0398 (3) | |
C4 | 0.05502 (13) | 0.0009 (2) | −0.18880 (10) | 0.0543 (4) | |
C5 | 0.28328 (9) | 0.09619 (15) | 0.14311 (7) | 0.0322 (2) | |
C6 | 0.20113 (9) | 0.01414 (14) | 0.04951 (7) | 0.0303 (2) | |
C7 | 0.19844 (9) | 0.15694 (15) | −0.03144 (7) | 0.0314 (2) | |
C8 | 0.33158 (10) | 0.18505 (18) | −0.03602 (9) | 0.0396 (3) | |
C9 | 0.41216 (11) | 0.2689 (2) | 0.05677 (9) | 0.0456 (3) | |
C10 | 0.41510 (10) | 0.1250 (2) | 0.13649 (9) | 0.0435 (3) | |
C11 | 0.23145 (13) | 0.29881 (17) | 0.16114 (9) | 0.0421 (3) | |
C12 | 0.22953 (13) | 0.44094 (16) | 0.08120 (9) | 0.0457 (3) | |
C13 | 0.14768 (11) | 0.35843 (16) | −0.01119 (9) | 0.0406 (3) | |
C14 | 0.36049 (14) | 0.46899 (19) | 0.07563 (11) | 0.0548 (4) | |
H2 | 0.2661 (16) | −0.248 (3) | 0.3202 (13) | 0.077 (5)* | |
H4 | 0.0043 (17) | −0.063 (3) | −0.2445 (14) | 0.072 (5)* | |
H6A | 0.2336 (11) | −0.1137 (19) | 0.0358 (9) | 0.036 (3)* | |
H6B | 0.1179 (12) | −0.0042 (17) | 0.0536 (9) | 0.036 (3)* | |
H8A | 0.3640 (14) | 0.055 (2) | −0.0489 (10) | 0.049 (4)* | |
H8B | 0.3328 (12) | 0.269 (2) | −0.0870 (10) | 0.042 (3)* | |
H9 | 0.4956 (14) | 0.283 (2) | 0.0525 (11) | 0.057 (4)* | |
H10A | 0.4668 (14) | 0.175 (2) | 0.1950 (11) | 0.053 (4)* | |
H10B | 0.4484 (14) | −0.008 (2) | 0.1243 (11) | 0.052 (4)* | |
H11A | 0.1490 (15) | 0.280 (2) | 0.1688 (11) | 0.058 (4)* | |
H11B | 0.2825 (14) | 0.356 (2) | 0.2211 (11) | 0.052 (4)* | |
H12 | 0.1974 (14) | 0.567 (2) | 0.0945 (11) | 0.056 (4)* | |
H13A | 0.1440 (14) | 0.445 (2) | −0.0645 (11) | 0.055 (4)* | |
H13B | 0.0615 (15) | 0.340 (2) | −0.0080 (11) | 0.055 (4)* | |
H14A | 0.3613 (15) | 0.561 (2) | 0.0255 (12) | 0.061 (4)* | |
H14B | 0.4157 (17) | 0.527 (3) | 0.1360 (14) | 0.074 (5)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0379 (5) | 0.0402 (6) | 0.0369 (6) | −0.0020 (4) | 0.0086 (5) | 0.0026 (5) |
C2 | 0.0523 (7) | 0.0520 (7) | 0.0450 (7) | −0.0029 (6) | 0.0112 (6) | 0.0153 (6) |
C3 | 0.0396 (6) | 0.0448 (6) | 0.0369 (6) | 0.0016 (5) | 0.0142 (5) | 0.0037 (5) |
C4 | 0.0516 (7) | 0.0702 (9) | 0.0391 (7) | −0.0116 (6) | 0.0102 (6) | −0.0021 (6) |
C5 | 0.0346 (5) | 0.0304 (5) | 0.0328 (6) | −0.0021 (4) | 0.0120 (4) | 0.0029 (4) |
C6 | 0.0315 (5) | 0.0256 (5) | 0.0353 (6) | 0.0008 (4) | 0.0122 (4) | 0.0014 (4) |
C7 | 0.0329 (5) | 0.0306 (5) | 0.0327 (5) | 0.0022 (4) | 0.0127 (4) | 0.0018 (4) |
C8 | 0.0381 (6) | 0.0458 (6) | 0.0404 (7) | −0.0007 (5) | 0.0202 (5) | 0.0029 (5) |
C9 | 0.0362 (6) | 0.0577 (7) | 0.0459 (7) | −0.0133 (5) | 0.0166 (5) | 0.0038 (6) |
C10 | 0.0323 (5) | 0.0549 (7) | 0.0413 (7) | −0.0056 (5) | 0.0079 (5) | 0.0046 (5) |
C11 | 0.0579 (7) | 0.0335 (6) | 0.0404 (7) | −0.0029 (5) | 0.0232 (6) | −0.0043 (5) |
C12 | 0.0689 (8) | 0.0238 (5) | 0.0505 (7) | 0.0003 (5) | 0.0271 (6) | −0.0015 (5) |
C13 | 0.0486 (6) | 0.0308 (5) | 0.0461 (7) | 0.0097 (5) | 0.0197 (5) | 0.0088 (5) |
C14 | 0.0748 (9) | 0.0412 (7) | 0.0505 (8) | −0.0249 (6) | 0.0218 (7) | −0.0010 (6) |
C1—C2 | 1.1763 (17) | C8—H8B | 0.952 (14) |
C1—C5 | 1.4708 (15) | C9—C10 | 1.5293 (18) |
C2—H2 | 0.927 (19) | C9—C14 | 1.530 (2) |
C3—C4 | 1.1812 (19) | C9—H9 | 0.971 (16) |
C3—C7 | 1.4673 (16) | C10—H10A | 0.957 (16) |
C4—H4 | 0.96 (2) | C10—H10B | 1.012 (15) |
C5—C6 | 1.5354 (15) | C11—C12 | 1.5269 (16) |
C5—C10 | 1.5370 (14) | C11—H11A | 0.982 (15) |
C5—C11 | 1.5418 (15) | C11—H11B | 0.988 (16) |
C6—C7 | 1.5396 (14) | C12—C14 | 1.5213 (19) |
C6—H6A | 0.982 (13) | C12—C13 | 1.5222 (19) |
C6—H6B | 0.970 (13) | C12—H12 | 0.967 (16) |
C7—C13 | 1.5396 (14) | C13—H13A | 0.980 (16) |
C7—C8 | 1.5408 (13) | C13—H13B | 0.999 (16) |
C8—C9 | 1.5250 (18) | C14—H14A | 0.976 (17) |
C8—H8A | 0.993 (14) | C14—H14B | 1.013 (19) |
C2—C1—C5 | 177.47 (13) | C10—C9—H9 | 108.6 (9) |
C1—C2—H2 | 175.6 (11) | C14—C9—H9 | 110.9 (9) |
C4—C3—C7 | 178.31 (12) | C9—C10—C5 | 109.45 (10) |
C3—C4—H4 | 177.5 (11) | C9—C10—H10A | 110.9 (9) |
C1—C5—C6 | 109.07 (8) | C5—C10—H10A | 109.2 (8) |
C1—C5—C10 | 111.08 (9) | C9—C10—H10B | 110.3 (9) |
C6—C5—C10 | 108.93 (9) | C5—C10—H10B | 108.7 (8) |
C1—C5—C11 | 110.04 (9) | H10A—C10—H10B | 108.3 (12) |
C6—C5—C11 | 108.63 (9) | C12—C11—C5 | 109.71 (9) |
C10—C5—C11 | 109.04 (9) | C12—C11—H11A | 112.4 (9) |
C5—C6—C7 | 110.88 (8) | C5—C11—H11A | 109.1 (9) |
C5—C6—H6A | 110.0 (7) | C12—C11—H11B | 109.6 (8) |
C7—C6—H6A | 107.8 (7) | C5—C11—H11B | 110.6 (9) |
C5—C6—H6B | 109.0 (7) | H11A—C11—H11B | 105.4 (12) |
C7—C6—H6B | 109.6 (7) | C14—C12—C13 | 109.69 (10) |
H6A—C6—H6B | 109.4 (10) | C14—C12—C11 | 109.43 (11) |
C3—C7—C6 | 109.04 (9) | C13—C12—C11 | 110.14 (10) |
C3—C7—C13 | 110.74 (9) | C14—C12—H12 | 109.6 (9) |
C6—C7—C13 | 108.60 (8) | C13—C12—H12 | 110.0 (10) |
C3—C7—C8 | 110.64 (8) | C11—C12—H12 | 108.0 (9) |
C6—C7—C8 | 108.67 (9) | C12—C13—C7 | 109.79 (10) |
C13—C7—C8 | 109.10 (9) | C12—C13—H13A | 112.7 (9) |
C9—C8—C7 | 109.55 (9) | C7—C13—H13A | 107.3 (9) |
C9—C8—H8A | 110.4 (9) | C12—C13—H13B | 110.1 (9) |
C7—C8—H8A | 108.9 (8) | C7—C13—H13B | 108.9 (9) |
C9—C8—H8B | 111.2 (8) | H13A—C13—H13B | 107.9 (13) |
C7—C8—H8B | 110.8 (8) | C12—C14—C9 | 109.43 (9) |
H8A—C8—H8B | 106.0 (11) | C12—C14—H14A | 110.6 (10) |
C8—C9—C10 | 110.04 (10) | C9—C14—H14A | 109.3 (9) |
C8—C9—C14 | 109.64 (11) | C12—C14—H14B | 110.7 (10) |
C10—C9—C14 | 109.70 (10) | C9—C14—H14B | 109.7 (10) |
C8—C9—H9 | 108.0 (9) | H14A—C14—H14B | 107.1 (13) |
C1—C5—C6—C7 | 179.35 (8) | C11—C5—C10—C9 | −59.23 (13) |
C10—C5—C6—C7 | −59.25 (11) | C1—C5—C11—C12 | −178.36 (10) |
C11—C5—C6—C7 | 59.41 (10) | C6—C5—C11—C12 | −59.03 (12) |
C5—C6—C7—C3 | 179.79 (8) | C10—C5—C11—C12 | 59.57 (13) |
C5—C6—C7—C13 | −59.44 (11) | C5—C11—C12—C14 | −60.35 (13) |
C5—C6—C7—C8 | 59.12 (10) | C5—C11—C12—C13 | 60.31 (13) |
C3—C7—C8—C9 | −178.86 (10) | C14—C12—C13—C7 | 60.10 (12) |
C6—C7—C8—C9 | −59.18 (12) | C11—C12—C13—C7 | −60.41 (12) |
C13—C7—C8—C9 | 59.07 (12) | C3—C7—C13—C12 | 178.84 (9) |
C7—C8—C9—C10 | 60.81 (13) | C6—C7—C13—C12 | 59.14 (11) |
C7—C8—C9—C14 | −59.92 (12) | C8—C7—C13—C12 | −59.15 (11) |
C8—C9—C10—C5 | −60.73 (13) | C13—C12—C14—C9 | −60.41 (14) |
C14—C9—C10—C5 | 59.97 (14) | C11—C12—C14—C9 | 60.52 (14) |
C1—C5—C10—C9 | 179.33 (10) | C8—C9—C14—C12 | 60.44 (13) |
C6—C5—C10—C9 | 59.17 (13) | C10—C9—C14—C12 | −60.51 (14) |
Cg is a group centroid. |
D—H···π | D—H | H···π | D···A | D—H···π |
Contacts with ethyne CH donors | ||||
C2—H2···Cg(C3C4)i | 0.927 (19) | 2.91 (2) | 3.679 (2) | 140.7 (14) |
C4—H4···Cg(C3C4)ii | 0.96 (2) | 3.12 (2) | 3.958 (2) | 146.5 (14) |
Contacts with aliphatic CH donors | ||||
C6—H6B···Cg(C3C4)iii | 0.970 (13) | 3.12 (2) | 4.030 (2) | 155.9 (10) |
C10—H10A···Cg(C1C2)iv | 0.957 (16) | 3.14 (2) | 3.853 (2) | 133.0 (10) |
C12—H12···Cg(C1C2)v | 0.967 (16) | 3.14 (2) | 3.904 (2) | 136.7 (12) |
Symmetry codes: (i) x, -1/2 - y, 1/2 + z; (ii) -x, -1/2 + y, -1/2 - z; (iii) -x, -y, -z; (iv) 1 - x, 1/2 + y, 1/2 - z; (v) x, 1 + y, z. |
Funding information
This work was supported by the Ministry of Education and Science of Ukraine (project No. 19BF037–05).
References
Allen, F. H., Wood, P. A. & Galek, P. T. A. (2013). Acta Cryst. B69, 281–287. Web of Science CrossRef IUCr Journals Google Scholar
Bond, A. D. (2002). Chem. Commun. pp. 1664–1665. Web of Science CSD CrossRef Google Scholar
Brandenburg, K. (1999). DIAMOND. Crystal Impact GbR, Bonn, Germany. Google Scholar
Degtyarenko, A. S., Handke, M., Krämer, K. W., Liu, S.-X., Decurtins, S., Rusanov, E. B., Thompson, L. K., Krautscheid, H. & Domasevitch, K. V. (2014). Dalton Trans. 43, 8530–8542. Web of Science CSD CrossRef CAS PubMed Google Scholar
Eaton, P. E., Galoppini, E. & Gilardi, R. (1994). J. Am. Chem. Soc. 116, 7588–7596. CSD CrossRef CAS Web of Science Google Scholar
Farrugia, L. J. (2012). J. Appl. Cryst. 45, 849–854. Web of Science CrossRef CAS IUCr Journals Google Scholar
Hirshfeld, F. L. (1977). Theor. Chim. Acta, 44, 129–138. CrossRef CAS Web of Science Google Scholar
McKinnon, J. J., Spackman, M. A. & Mitchell, A. S. (2004). Acta Cryst. B60, 627–668. Web of Science CrossRef CAS IUCr Journals Google Scholar
McMullan, R. K., Kvick, Å. & Popelier, P. (1992). Acta Cryst. B48, 726–731. CSD CrossRef CAS Web of Science IUCr Journals Google Scholar
Negrier, P., Ben Hassine, B., Barrio, M., Romanini, M., Mondieig, D. & Tamarit, J.-L. (2020). CrystEngComm, 22, 1230–1238. Web of Science CSD CrossRef CAS Google Scholar
Nishio, M. (2004). CrystEngComm, 6, 130–158. Web of Science CrossRef CAS Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Sheldrick, G. M. (2015). Acta Cryst. C71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Spackman, M. A. & Byrom, P. G. A. (1997). Chem. Phys. Lett. 267, 215–220. CrossRef CAS Web of Science Google Scholar
Spackman, M. A. & McKinnon, J. J. (2002). CrystEngComm, 4, 378–392. Web of Science CrossRef CAS Google Scholar
Stoe & Cie (2000). IPDS Software. Stoe & Cie GmbH, Darmstadt, Germany. Google Scholar
Tukada, H. & Mochizuki, K. (2003). J. Mol. Struct. 655, 473–478. Web of Science CSD CrossRef CAS Google Scholar
Weiss, H.-C., Bläser, D., Boese, R., Doughan, B. M. & Haley, M. M. (1997). Chem. Commun. pp. 1703–1704. CSD CrossRef Web of Science Google Scholar
Zefirov, Y. V. (1997). Crystallogr. Rep. 42, 865–886. Google Scholar
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