research communications
A 2:1
of 3,5-dibromo-4-cyanobenzoic acid and anthraceneaDepartment of Chemistry, University of Minnesota, 207 Pleasant St SE, Minneapolis, MN 55455, USA
*Correspondence e-mail: nolan001@umn.edu
The title 8H3Br2NO2·0.5C14H10, was self-assembled from a 2:1 mixture of the components in slowly evaporating dichloromethane. The molecules adopt a sheet structure parallel to (1-12) in which carboxy hydrogen-bonded dimers and anthracene molecules stagger in both dimensions. Within the sheets, six individual cyano acid molecules surround each anthracene molecule. Cyano acid molecules form one of the two possible R22(10) rings between neighboring cyano and bromo groups. Compared to the dichloro analog [Britton (2012). J. Chem. Crystallogr. 42, 851–855], the dihedral angle between the best-fit planes of acid and anthracene molecules has decreased from 7.1 to 0.9 (2)°.
CKeywords: crystal structure; co-crystal; carboxylic acid; N⋯Br contacts.
CCDC reference: 1525811
1. Chemical context
Doyle Britton (1930–2015) published roughly 30 crystallographic articles on solid-phase cyano–halo interactions from variously substituted halobenzonitriles and a) via a combination of carboxy hydrogen-bond dimerization and CN⋯Cl short contacts. In 2012, he found that the cyano acid molecules alone do not pack in this way, but slow evaporation of mixtures containing naphthalene or anthracene afforded 2:1 acid:hydrocarbon co-crystals roughly matching his proposed structure (Britton, 2012). However, no CN⋯Cl contacts were observed (Fig. 1b). Anthracene was the better fit, although it was too large to allow the ideal molecular arrangement. There is no obvious substitute for anthracene or naphthalene. Thus, we have prepared anthracene co-crystals with the dibromo analog in hopes that the larger Br bond and contact radii might close the CN⋯X gaps observed with Cl.
Britton postulated that 3,5-dichloro-4-cyanobenzoic acid might assemble into a honeycomb-like sheet structure (Fig. 12. Structural commentary
The benzene (C2–C5/C7/C8) and anthracene (C9–C15 and symmetry equivalents, Fig. 2) ring systems are nearly planar. The mean deviation of atoms from the planes of best fit are 0.0074 (17) Å and 0.0041 (14) Å, respectively, both of which are comparable to the corresponding values in the dichloro crystal. However, the dihedral angle between the carboxy group (O1–C1–O2) and the benzene ring is 3.2 (4)°, compared with 7.2° in the dichloro analog.
3. Supramolecular features
The dihedral angle between the benzene and anthracene planes is 0.9 (2)°, which is much lower than 7.1° of the dichloro analog. As expected, (8) carboxy hydrogen-bonded dimers are observed (Table 1); these are located on an inversion center. (10) rings form about another inversion center based on C6≡N1⋯Br2 contacts (Table 2); however, the corresponding N1⋯Br1 contacts are not observed (Fig. 3). Instead, 3.5534 (5) Å Br1⋯Br1 contacts form, slightly closer than the 3.70 Å non-bonded contact diameter of Br (Rowland & Taylor, 1996). In the title two corners of the anthracene molecule contact the cyano acid network (Fig. 3), whereas all four corners made contact in the Cl analog (Fig. 1b). Overall, substitution of Cl atoms with Br atoms has facilitated the formation of half of the envisioned CN⋯X short contacts and also improved the coplanarity of the acid and hydrocarbon molecules, but anthracene is slightly too large to allow the ideal arrangement of cyano acid molecules. It is possible that upon substitution of Br atoms with I atoms, the improvements would continue and the envisioned sheet structure might occur. This possibility is currently being studied in our laboratory.
4. Database survey
A search of the Cambridge Structural Database (Version 5.38, update May 2017; Groom et al., 2016) found no 4-cyano-3-halobenzoic acids other than the six structures reported by Britton (2012). Among 3-halobenzoic acids, no entries were found in which carboxy dimers formed and assembled into a honeycomb-like sheet, with or without a co-former. Of the 40 entries for 3,5-dihalo-2,6-unsubstituted benzoic acids, 11 of them are co-crystals with carboxy monomers hydrogen-bonded to an O or N atom in the co-former (i.e., Dubey & Desiraju, 2014; Back et al., 2012). Hydroxy acid (I) (Prout et al., 1988; Fig. 4) and amino acids (II) (Pant, 1965; Ueda et al., 2014) form interlocking ribbons in which adjacent carboxy dimers are connected by I⋯I contacts, or amino-carboxy hydrogen-bonds, respectively. 4-Cyanobenzoic acid (III) forms a sheet structure in which carboxy dimers are connected lengthwise by (10) rings formed by CN⋯H contacts, and laterally by R33(7) rings formed by weak C—H⋯O bonds flanking each pair of carboxy groups (Higashi & Osaki, 1981).
5. Synthesis and crystallization
Methyl 4-amino-3,5-dibromobenzoate (V): Bromine (3.9 mL) and then pyridine (5.7 mL) were added dropwise to ice-cold methanol (35 mL). This mixture was added dropwise to a solution of methyl 4-aminobenzoate [(IV), commercially available, Fig. 5] in methanol (50 mL). The resulting mixture was refluxed for 4 h and then cooled to room temperature. The methanol was removed on a rotary evaporator. Dichloromethane (50 mL) and water (50 mL) were added. Aliquots (5 mL) of Na2CO3 solution (aq., sat.) were added until the aqueous phase remained slightly alkaline after 10 min. The organic phase was separated and then washed with Na2S2O3 solution (aq., sat., 25 mL), water (25 mL), brine (25 mL), and was then concentrated on a rotary evaporator. The resulting brown residue was recrystallized from ethyl acetate, giving colorless needles (18.1 g, 93%). M.p. 406–408 K (lit. 404–406 K; Otto & Juppe, 1965); 1H NMR (300 MHz, CDCl3) δ 8.063 (s, 2H), 4.996 (s, 2H), 3.866 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 165.1 (1C), 145.9 (1C), 133.5 (2C), 121.0 (1C), 107.5 (2C), 52.3 (1C); IR (NaCl, cm−1) 3321, 3076, 2958, 1723, 1713, 1610, 1432, 1303, 1268, 975, 855, 761; MS (ESI, m/z) [M+Na]+ calculated for C8H7Br2NO2 331.8715, found 331.8709.
Methyl 3,5-dibromo-4-cyanobenzoate (VI), adapted from the work of Toya et al. (1992): Cyanide suspension: NaCN (680 mg) and CuCN (480 mg) and water (40 mL) were combined in a 400 mL beaker. After the solids dissolved, NaHCO3 (6.5 g) was added. The resulting suspension was cooled in an ice bath. Diazotization: Dibromo ester [(V), 720 mg] was ground in a mortar and then combined with acetic acid (2.6 mL) in a round-bottomed flask. H2SO4 (0.6 mL) was added dropwise over 1 min, followed by a solution of NaNO2 (313 mg) in water (1.5 mL) over 30 min.. During the course of the additions, the reaction mixture was gradually warmed in an oil bath to 315 K. Cyanation: When no more starting material remained, as indicated by TLC, the diazotization mixture was removed from the heat and then added dropwise to the cyanide suspension. The ice bath was removed. The cyanation mixture was stirred overnight and then extracted with dichloromethane (3 × 20 mL). The combined organic portions were washed with water (20 mL), brine (20 mL), dried with Na2SO4, filtered, and then concentrated on a rotary evaporator. The resulting brown residue was separated by The desired fraction (Rf = 0.34 in 3:1 hexane:ethyl acetate on SiO2) was concentrated on a rotary evaporator, giving a tan powder (681 mg, 92%). M.p. 410–411 K; 1H NMR (500 MHz, CDCl3) δ 8.264 (s, 2H), 3.974 (s, 3H); 13C NMR (126 MHz, CDCl3) δ 163.4 (1C), 135.5 (1C), 132.6 (2C), 127.1 (2C), 122.5 (1C), 115.5 (1C), 53.5 (1C); IR (KBr, cm−1) 3076, 2955, 2229, 1732, 1429, 1263, 1124, 971, 748; MS (ESI, m/z) [M+Na]+ calculated for C9H5Br2NO2 341.8559, found 341.8547.
3,5-Dibromo-4-cyanobenzoic acid (VII), adapted from the work of Lepage et al. (2004; especially compound 24): Cyano ester [(VI), 231 mg], lithium iodide (128 mg), and pyridine (10 mL) were combined in a round-bottomed flask. The resulting mixture was refluxed for 24 h and then cooled to room temperature. Chloroform (25 mL), water (25 mL), and hydrochloric acid (12 M, 25 mL) were added. After being stirred for 10 min, the resulting mixture was separated by suction filtration, giving a light-brown powder (217 mg, 99%). M.p. 423–425 K; 1H NMR (500 MHz, (CD3)2SO) δ 14.120 (s, H1A), 8.232 (s, H3A, H8A); 13C NMR (126 MHz, (CD3)2SO) δ 163.9 (C1), 137.0 (C2), 132.1 (C3, C8), 126.7 (C4, C7), 120.6 (C5), 115.9 (C6); IR (KBr, cm−1) 3421, 3077, 2128, 1811, 1662, 1537, 1371, 1296, 1025, 825, 770, 748; MS (ESI, m/z) [M–H]− calculated for C8H3Br2NO2 303.8437, found 303.8443.
Crystallization: 3,5-Dibromo-4-cyanobenzoic acid (100 mg) and anthracene (29 mg) were dissolved in dichloromethane (25 mL) in a loosely covered beaker. Most of the solvent was allowed to evaporate gradually over 3 d. The resulting colorless or pale-orange plate-shaped crystals were collected after decantation and then washed with several drops of ice-cold 1:3 dichloromethane:pentane.
6. Refinement
Crystal data, data collection and structure . A direct-methods solution was calculated, followed by full-matrix least squares/difference-Fourier cycles. All H atoms were placed in calculated positions (C—H = 0.95 Å, O—H = 0.84 Å) and refined as riding atoms with Uiso(H) set to 1.2Ueq(C) and 1.5Ueq(O).
details are summarized in Table 3Supporting information
CCDC reference: 1525811
https://doi.org/10.1107/S2056989017014815/lh5854sup1.cif
contains datablock I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989017014815/lh5854Isup2.hkl
Supporting information file. DOI: https://doi.org/10.1107/S2056989017014815/lh5854Isup3.cml
Data collection: APEX2 (Bruker, 2012); cell
SAINT (Bruker, 2012); data reduction: SAINT (Bruker, 2012); program(s) used to solve structure: SHELXS97 (Sheldrick 2015a); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015b); molecular graphics: Mercury (Macrae et al., 2008); software used to prepare material for publication: publCIF (Westrip, 2010).C8H3Br2NO2·0.5C14H10 | Z = 2 |
Mr = 394.04 | F(000) = 382 |
Triclinic, P1 | Dx = 1.924 Mg m−3 |
a = 8.8963 (8) Å | Cu Kα radiation, λ = 1.54178 Å |
b = 9.4701 (9) Å | Cell parameters from 2967 reflections |
c = 9.5839 (9) Å | θ = 5.3–74.6° |
α = 115.356 (3)° | µ = 7.57 mm−1 |
β = 106.876 (3)° | T = 123 K |
γ = 94.119 (3)° | Plate, pale orange |
V = 680.03 (11) Å3 | 0.18 × 0.09 × 0.03 mm |
Bruker VENTURE PHOTON-1000 diffractometer | 2607 reflections with I > 2σ(I) |
φ and ω scans | Rint = 0.035 |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | θmax = 74.6°, θmin = 5.3° |
Tmin = 0.509, Tmax = 0.754 | h = −11→11 |
9139 measured reflections | k = −11→11 |
2745 independent reflections | l = −11→11 |
Refinement on F2 | 0 restraints |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.026 | H-atom parameters constrained |
wR(F2) = 0.068 | w = 1/[σ2(Fo2) + (0.0369P)2 + 0.5603P] where P = (Fo2 + 2Fc2)/3 |
S = 1.06 | (Δ/σ)max = 0.001 |
2745 reflections | Δρmax = 0.40 e Å−3 |
182 parameters | Δρmin = −0.53 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 | ||
Br1 | 0.38562 (3) | 0.12356 (3) | 0.93908 (3) | 0.01483 (9) | |
Br2 | 0.81803 (2) | 0.51847 (3) | 0.84679 (3) | 0.01686 (9) | |
O1 | 0.21809 (18) | 0.54610 (19) | 0.5615 (2) | 0.0154 (3) | |
H1A | 0.1338 | 0.5671 | 0.5146 | 0.023* | |
O2 | 0.04198 (18) | 0.38413 (18) | 0.5858 (2) | 0.0139 (3) | |
N1 | 0.8230 (2) | 0.2641 (3) | 1.0526 (3) | 0.0211 (4) | |
C1 | 0.1800 (3) | 0.4429 (2) | 0.6097 (3) | 0.0102 (4) | |
C2 | 0.3217 (2) | 0.4018 (2) | 0.7011 (2) | 0.0092 (4) | |
C3 | 0.2929 (2) | 0.2999 (2) | 0.7650 (2) | 0.0096 (4) | |
H3A | 0.1859 | 0.2573 | 0.7495 | 0.011* | |
C4 | 0.4229 (3) | 0.2615 (2) | 0.8516 (2) | 0.0100 (4) | |
C5 | 0.5815 (2) | 0.3249 (2) | 0.8767 (2) | 0.0102 (4) | |
C6 | 0.7162 (3) | 0.2888 (3) | 0.9728 (3) | 0.0135 (4) | |
C7 | 0.6057 (3) | 0.4265 (3) | 0.8107 (3) | 0.0116 (4) | |
C8 | 0.4777 (3) | 0.4647 (2) | 0.7223 (2) | 0.0103 (4) | |
H8A | 0.4958 | 0.5328 | 0.6766 | 0.012* | |
C9 | 0.4142 (3) | 0.8993 (2) | 0.5372 (3) | 0.0131 (4) | |
H9A | 0.3562 | 0.8307 | 0.5622 | 0.016* | |
C10 | 0.5827 (3) | 0.9268 (2) | 0.5908 (3) | 0.0126 (4) | |
C11 | 0.6714 (3) | 0.8552 (3) | 0.6831 (3) | 0.0179 (5) | |
H11A | 0.6149 | 0.7875 | 0.7102 | 0.022* | |
C12 | 0.8344 (3) | 0.8823 (3) | 0.7326 (3) | 0.0230 (5) | |
H12A | 0.8912 | 0.8345 | 0.7947 | 0.028* | |
C13 | 0.9206 (3) | 0.9822 (3) | 0.6915 (3) | 0.0247 (5) | |
H13A | 1.0347 | 0.9989 | 0.7249 | 0.030* | |
C14 | 0.8420 (3) | 1.0540 (3) | 0.6055 (3) | 0.0198 (5) | |
H14A | 0.9019 | 1.1211 | 0.5803 | 0.024* | |
C15 | 0.6700 (3) | 1.0296 (2) | 0.5522 (3) | 0.0121 (4) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Br1 | 0.01625 (14) | 0.01597 (13) | 0.01776 (14) | 0.00482 (9) | 0.00336 (10) | 0.01426 (10) |
Br2 | 0.00653 (13) | 0.02493 (15) | 0.02190 (14) | 0.00266 (9) | 0.00341 (10) | 0.01464 (11) |
O1 | 0.0098 (7) | 0.0197 (8) | 0.0244 (8) | 0.0037 (6) | 0.0021 (6) | 0.0196 (7) |
O2 | 0.0079 (7) | 0.0163 (7) | 0.0211 (8) | 0.0027 (6) | 0.0017 (6) | 0.0141 (6) |
N1 | 0.0163 (10) | 0.0255 (10) | 0.0221 (10) | 0.0110 (8) | 0.0021 (8) | 0.0136 (9) |
C1 | 0.0104 (10) | 0.0099 (9) | 0.0095 (9) | 0.0028 (7) | 0.0010 (7) | 0.0053 (7) |
C2 | 0.0092 (9) | 0.0086 (9) | 0.0081 (9) | 0.0037 (7) | −0.0007 (7) | 0.0046 (7) |
C3 | 0.0084 (9) | 0.0091 (9) | 0.0107 (9) | 0.0020 (7) | 0.0014 (7) | 0.0054 (7) |
C4 | 0.0115 (10) | 0.0100 (9) | 0.0090 (9) | 0.0045 (7) | 0.0011 (8) | 0.0062 (8) |
C5 | 0.0080 (9) | 0.0111 (9) | 0.0082 (9) | 0.0045 (7) | −0.0005 (7) | 0.0035 (8) |
C6 | 0.0117 (10) | 0.0140 (10) | 0.0131 (10) | 0.0048 (8) | 0.0025 (8) | 0.0059 (8) |
C7 | 0.0088 (9) | 0.0128 (9) | 0.0112 (9) | 0.0016 (7) | 0.0028 (8) | 0.0044 (8) |
C8 | 0.0113 (9) | 0.0095 (9) | 0.0108 (9) | 0.0021 (7) | 0.0025 (8) | 0.0063 (8) |
C9 | 0.0162 (10) | 0.0082 (9) | 0.0148 (10) | 0.0001 (8) | 0.0070 (8) | 0.0047 (8) |
C10 | 0.0172 (11) | 0.0081 (9) | 0.0113 (9) | 0.0016 (8) | 0.0056 (8) | 0.0033 (8) |
C11 | 0.0245 (12) | 0.0125 (10) | 0.0156 (10) | 0.0033 (9) | 0.0049 (9) | 0.0069 (9) |
C12 | 0.0257 (13) | 0.0167 (11) | 0.0196 (11) | 0.0055 (9) | −0.0010 (10) | 0.0082 (9) |
C13 | 0.0135 (11) | 0.0222 (12) | 0.0276 (13) | 0.0018 (9) | 0.0007 (9) | 0.0071 (10) |
C14 | 0.0131 (11) | 0.0152 (11) | 0.0261 (12) | −0.0012 (8) | 0.0052 (9) | 0.0072 (9) |
C15 | 0.0138 (10) | 0.0073 (9) | 0.0131 (9) | 0.0000 (7) | 0.0057 (8) | 0.0027 (8) |
Br1—C4 | 1.886 (2) | C8—H8A | 0.9500 |
Br2—C7 | 1.890 (2) | C9—C15i | 1.394 (3) |
O1—C1 | 1.309 (3) | C9—C10 | 1.400 (3) |
O1—H1A | 0.8400 | C9—H9A | 0.9500 |
O2—C1 | 1.224 (3) | C10—C11 | 1.432 (3) |
N1—C6 | 1.142 (3) | C10—C15 | 1.432 (3) |
C1—C2 | 1.493 (3) | C11—C12 | 1.356 (4) |
C2—C3 | 1.390 (3) | C11—H11A | 0.9500 |
C2—C8 | 1.391 (3) | C12—C13 | 1.423 (4) |
C3—C4 | 1.386 (3) | C12—H12A | 0.9500 |
C3—H3A | 0.9500 | C13—C14 | 1.359 (4) |
C4—C5 | 1.402 (3) | C13—H13A | 0.9500 |
C5—C7 | 1.394 (3) | C14—C15 | 1.433 (3) |
C5—C6 | 1.446 (3) | C14—H14A | 0.9500 |
C7—C8 | 1.381 (3) | C15—C9i | 1.394 (3) |
C1—O1—H1A | 109.5 | C2—C8—H8A | 120.5 |
O2—C1—O1 | 124.6 (2) | C15i—C9—C10 | 121.3 (2) |
O2—C1—C2 | 121.29 (19) | C15i—C9—H9A | 119.4 |
O1—C1—C2 | 114.08 (18) | C10—C9—H9A | 119.4 |
C3—C2—C8 | 121.22 (19) | C9—C10—C11 | 122.1 (2) |
C3—C2—C1 | 117.98 (18) | C9—C10—C15 | 119.3 (2) |
C8—C2—C1 | 120.80 (19) | C11—C10—C15 | 118.6 (2) |
C4—C3—C2 | 118.88 (19) | C12—C11—C10 | 121.2 (2) |
C4—C3—H3A | 120.6 | C12—C11—H11A | 119.4 |
C2—C3—H3A | 120.6 | C10—C11—H11A | 119.4 |
C3—C4—C5 | 121.09 (19) | C11—C12—C13 | 120.0 (2) |
C3—C4—Br1 | 119.34 (16) | C11—C12—H12A | 120.0 |
C5—C4—Br1 | 119.57 (15) | C13—C12—H12A | 120.0 |
C7—C5—C4 | 118.42 (19) | C14—C13—C12 | 121.0 (2) |
C7—C5—C6 | 121.09 (19) | C14—C13—H13A | 119.5 |
C4—C5—C6 | 120.47 (19) | C12—C13—H13A | 119.5 |
N1—C6—C5 | 178.1 (2) | C13—C14—C15 | 120.7 (2) |
C8—C7—C5 | 121.37 (19) | C13—C14—H14A | 119.7 |
C8—C7—Br2 | 119.04 (16) | C15—C14—H14A | 119.7 |
C5—C7—Br2 | 119.57 (16) | C9i—C15—C10 | 119.5 (2) |
C7—C8—C2 | 119.02 (19) | C9i—C15—C14 | 122.1 (2) |
C7—C8—H8A | 120.5 | C10—C15—C14 | 118.5 (2) |
O2—C1—C2—C3 | −2.9 (3) | Br2—C7—C8—C2 | −177.60 (15) |
O1—C1—C2—C3 | 176.48 (18) | C3—C2—C8—C7 | −1.0 (3) |
O2—C1—C2—C8 | 177.60 (19) | C1—C2—C8—C7 | 178.55 (18) |
O1—C1—C2—C8 | −3.1 (3) | C15i—C9—C10—C11 | 179.81 (19) |
C8—C2—C3—C4 | 0.2 (3) | C15i—C9—C10—C15 | −0.3 (3) |
C1—C2—C3—C4 | −179.35 (18) | C9—C10—C11—C12 | 179.4 (2) |
C2—C3—C4—C5 | 0.6 (3) | C15—C10—C11—C12 | −0.5 (3) |
C2—C3—C4—Br1 | 179.97 (14) | C10—C11—C12—C13 | −0.6 (4) |
C3—C4—C5—C7 | −0.7 (3) | C11—C12—C13—C14 | 1.2 (4) |
Br1—C4—C5—C7 | 180.00 (14) | C12—C13—C14—C15 | −0.7 (4) |
C3—C4—C5—C6 | 177.55 (18) | C9—C10—C15—C9i | 0.3 (3) |
Br1—C4—C5—C6 | −1.8 (3) | C11—C10—C15—C9i | −179.81 (19) |
C4—C5—C7—C8 | −0.1 (3) | C9—C10—C15—C14 | −178.88 (19) |
C6—C5—C7—C8 | −178.35 (19) | C11—C10—C15—C14 | 1.0 (3) |
C4—C5—C7—Br2 | 178.40 (14) | C13—C14—C15—C9i | −179.6 (2) |
C6—C5—C7—Br2 | 0.2 (3) | C13—C14—C15—C10 | −0.4 (3) |
C5—C7—C8—C2 | 1.0 (3) |
Symmetry code: (i) −x+1, −y+2, −z+1. |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1A···O2ii | 0.84 | 1.79 | 2.627 (2) | 178 |
Symmetry code: (ii) −x, −y+1, −z+1. |
C—X···Br | C—X | X···Br | C—X···Br |
C6≡N1···Br2ii | 1.143 (4) | 3.307 (2) | 115.9 (2) |
C4—Br1···Br1iii | 1.886 (2) | 3.5534 (5) | 133.43 (7) |
Symmetry codes: (ii) -x + 2, -y + 1, -z + 2; (iii) -x + 1, -y, -z + 2. |
Acknowledgements
The authors thank Victor G. Young, Jr. (X-Ray Crystallographic Laboratory, University of Minnesota) for assistance with the crystallographic determination, the Wayland E. Noland Research Fellowship Fund at the University of Minnesota Foundation for generous financial support of this project, and Doyle Britton (deceased July 7, 2015) for providing the basis of this project. This work was taken in large part from the PhD thesis of KJT (Tritch, 2017).
References
Back, K. R., Davey, R. J., Grecu, T., Hunter, C. A. & Taylor, L. S. (2012). Cryst. Growth Des. 12, 6110–6117. Web of Science CSD CrossRef CAS
Britton, D. (2012). J. Chem. Crystallogr. 42, 851–855. CAS
Bruker (2012). APEX2 and SAINT. Bruker AXS, Inc., Madison, WI, USA.
Dubey, R. & Desiraju, G. R. (2014). Chem. Commun. 50, 1181–1184. Web of Science CSD CrossRef CAS
Groom, C. R., Bruno, I. J., Lightfoot, M. P. & Ward, S. C. (2016). Acta Cryst. B72, 171–179. Web of Science CSD CrossRef IUCr Journals
Higashi, T. & Osaki, K. (1981). Acta Cryst. B37, 777–779. CSD CrossRef CAS Web of Science IUCr Journals
Lepage, O., Kattnig, E. & Fürstner, A. (2004). J. Am. Chem. Soc. 126, 15970–15971. PubMed CAS
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
Otto, P. Ph. H. L. & Juppe, G. (1965). J. Labelled Cmpd, 1, 115–127. CAS
Pant, A. K. (1965). Acta Cryst. 19, 440–448. CSD CrossRef IUCr Journals Web of Science
Prout, K., Fail, J., Jones, R. M., Warner, R. E. & Emmett, J. C. (1988). J. Chem. Soc. Perkin Trans. 2, pp. 265–284. CSD CrossRef Web of Science
Rowland, R. S. & Taylor, R. (1996). J. Phys. Chem. 100, 7384–7391. CSD CrossRef CAS Web of Science
Sheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.
Sheldrick, G. M. (2015a). Acta Cryst. A71, 3–8. Web of Science CrossRef IUCr Journals
Sheldrick, G. M. (2015b). Acta Cryst. C71, 3–8. Web of Science CrossRef IUCr Journals
Toya, Y., Takagi, M., Nakata, H., Suzuki, N., Isobe, M. & Goto, T. (1992). Bull. Chem. Soc. Jpn, 65, 392–395. CrossRef CAS Web of Science
Tritch, K. J. (2017). PhD thesis, University of Minnesota, Minneapolis, MN, USA.
Ueda, K., Oguni, M. & Asaji, T. (2014). Cryst. Growth Des. 14, 6189–6196. Web of Science CSD CrossRef CAS
Westrip, S. P. (2010). J. Appl. Cryst. 43, 920–925. Web of Science CrossRef CAS IUCr Journals
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.