K. M. Beketov

Polymorphism of Crystalline Inclusion Complexes and Unsolvated Hosts. Part 8

Crystallization of cyclotriveratrylene (CTV) from solutions in acetone at 40°C gave a new 4 : 1 host-guest complex instead of the conventional 2 : 1 clathrate (β-phase) whose X-ray crystal structure was determined. Data for 2(C27H30O6) · 0.5(CO(CH3)2): monoclinic, P21/c, a = 18.942(4), b = 24.697(5), c = 10.508(2) Å, β = 91.10(2)°, V = 4915(2) Å3, Z = 8, Dx = 1.257 g/cm3, T = 293 K, R = 0.077 (for 2694 reflections). One of the two crystallographically independent CTV molecules (molecule A) is stacked into columns characteristic of the CTV α- or β-phase complexes. Molecules B face each other enclathrating inside around the inversion center disordered acetone molecules giving rise to the molecular capsule. The acetone molecule is H-bonded simultaneously to both host molecules by C(H2)--H ··· O type bonds forming centrosymmetric dimers. Dimers are incorporated together with two A molecules into centrosymmetric units also by C(H2)--H ··· O type H-bonds. Packing of these units gives rise to the crystal structure of the clathrate.

Polymorphism of Inclusion Complexes and Unsolvated Hosts. I. Trimorphism of the Host-Guest Complex of Gossypol with Dichloromethane. The Structure of the β-Phase

The formation of host-guest complexes of gossypol at different temperatures has been investigated for the same pressure and concentration. Gossypol forms three different clathrates with dichloromethane within the temperature interval of 22-36 °C. Single crystals of these three modifications (phases) were obtained and their crystallographic parameters measured. The structure of the α-phase has been determined previously and the γ-phase is isostructural to the inclusion complex of gossypol with benzene, while the structure of the β-phase has been solved during the present research. Crystals of C30H30O8·CH2Cl2 are triclinic, space group P1, a = 8.604(1), b = 11.858(2), c = 14.405(2) (Å), α = 84.60(1), β = 89.14(1), γ = 89.73(1)°, V = 1463(1) Å3, Z = 2, R = 0.089 for 2419 observed reflections.Under ambient conditions gossypol forms unstable tubulates of the α-phase; the γ-phase is a stable cage-type clathrate (cryptate) and the host-guest complex of the β-phase is a clathrate of intermediate tubulato-cryptate type.

X-ray and thermochemical studies of phase transitions in crystalline host–guest compounds of 1,1′–binaphthyl–2,2′–dicarboxylic acid with ethanol and acetone

Abstract The crystal structures of two 1:2 and 1:1 host–guest compounds between BNDA and acetone have been determined by single crystal X-ray diffraction and are comparatively discussed with reference to recently reported BNDA/ethanol clathrates of different composition. Simultaneous thermogravimetry and differential scanning calorimetry (TG–DSC) in combination with the X-ray powder diffraction (XRD) method reveal that the thermal degradation of the BNDA/ethanol 1:2 α–form clathrate takes place in two steps with the intermediate formation of the 2:1 β–form clathrate. On the other hand, desolvation of the BNDA/acetone 1:2 α–form clathrate gives no indication for the formation of any intermediate phase in the TG–DSC traces unlike the XRD studies showing the existence of the β–form during desolvation. A possible explanation of this latter property is the very similar thermal decomposition temperature of both phases. The TG–DSC results for the isothermal inclusion of vaporous ethanol and acetone indicate that this process takes place in a single step with the formation of the 1:2 BNDA/ethanol and 1:1 BNDA/acetone clathrates, respectively.

Disorder as adaptation of the crystal structure to increase the crystallization temperature. X‐ray crystal structure of the host–guest complexes between 1,1′‐binaphthyl‐2,2′‐dicarboxylic acid and dimethyl sulphoxide obtained at 50 and 60 °C

The complex formation of 1,1′-binaphthyl-2,2′-dicarboxylic acid (BNDA) with dimethyl sulphoxide (DMSO) at different temperatures was investigated. The crystal structures of the α- and β-form [triclinic, P1, a = 9.614(2), b = 11.743(2), c = 12.029(2) A, α = 99.35(3), β = 93.58(3), γ = 110.51(3)°, V = 1244.5(4) A3, Z = 2, R = 0.053 for 4879 reflections] host–guest complexes obtained at 50 and 60 °C, respectively, were determined by x-ray structure analysis (the crystal structure of the α-form obtained at room temperature was studied previously). There is disorder of the guest molecules characteristic of the α-form of the 1:1 BNDA·DMSO complex obtained at 50 °C and the host carboxylic groups in the β-form of the 1:2 BNDA·DMSO, considered a consequence of the changed conditions for crystal preparation. By disordering of the crystal structure the interaction of the solvent molecule with its environment, especially with nearest BNDA molecules, is improved. The new orientation leads to the formation of a more compact host–guest associate which resists the escape of the guest molecules from the growing crystal during crystallization and may exist even in the nucleation step. Thus disordering of the solvent molecules (α-form) and disordering of the carboxyl groups of the host molecules (β-form) are the two modes of operation in this system. Copyright

Polymorphism of Inclusion Complexes and Unsolvated Hosts. II. Structure of the β-Dimorph of the Host-Guest Complex of Dianilinegossypol with Ethylacetate

Depending on crystallization conditions, dianilinegossypol and ethylacetate form low (ambient temperature, α-phase) and high temperature (t = 35°C, β-phase) clathrate modifications. The structure of the α-phase has been discussed earlier [1]. Crystals of the 1 : 1 β-phase complex, C42H40O6N2·C4O2H8, are monoclinic, space group P21/c, a = 11.362(6), b = 19.479(9), c = 19.085(9) Å, β = 103.21(4)°, V = 4112(3)Å3, Z = 4, R = 0.084 for 3210 observed reflections.In these complexes centrosymmetric dimers of dianilinegossypol molecules formed via O(5)—H···O(3) hydrogen bonds are associated into columns by a weak O(8)—H···O(7) H-bond. A difference in the structure of these two phases is in the packing mode of the columns. The angle formed by intersecting host columns is about 126° for the α-phase and 104° for the β-modification. Guest molecules are hydrogen bonded to the host molecules via an O(1)—H···O(10) bond and are accommodated in channels in α-phase complex and in cavities in β-phase complex.

Polymorphism of Inclusion Complexes and Unsolvated Hosts. IV. Dimorphism of the Acetone Host–Guest Complex of Dianilinegossypol. Structures of the α- and β-Phase Complexes

Crystal structures of the α- and β-phase inclusion complexes of dianilinegossypol with acetone obtained at 20° and 30 °C, respectively, have been determined by X-ray structure analysis. Crystal data of the α-phase complex are: C42H40O6N2⋅2C3H6O, orthorhombic, space group Pccn, a = 29.501(9), b = 10.866(2), c = 13.756(3) Å, V = 4409(1) Å3, Z = 4, Dx = 1.18 g cm-3. The structure has been refined to a final R value of 0.117 for 1401 observed reflections. The host–guest ratio for the β-phase complex is the same (1 : 2) and the crystals are monoclinic, space group C2/c, a = 28.352(6), b = 11.836(2), c = 13.196(1) Å, β = 93.05(1)°, V = 4422(2) Å3, Z = 4, Dx =1.18 g cm-3. The structure has been refined to a final R value of 0.077 for 1414 observed reflections.In both phases molecules of dianilinegossypol form hydrogen-bondedribbons by O(4)–-H⋅O(3) H-bonds. Phases are determined by the same structural motif. In the β-phase complex the cages are in the form of prisms but in the α-phase clathrate they undergo a modification by shrinking in two directions and widening in one. Molecules of acetone are hydrogen bonded to the host molecules via aO(1)–-H⋅O(G) bond and are accommodated in cavities for both complexes, i.e. both phases are cryptate-type inclusion complexes.Supplementary data relevant to this publicationhave been deposited with the British Library,No. SUP 82227 (24 pages).

Polymorphism of Inclusion Complexes and Unsolvated Hosts. III. Dimorphism of the Alkaloid Colchicine Hydrate. The Structure of Colchicine Monohydrate

The alkaloid colchicine forms, in addition to the previously known dihydrate host–guest complex, a monohydrate complex. The crystal structure of the monohydrate was determined by direct methods and refined to a final R value of 0.046 for 1425 observed reflections. Crystal data are: orthorhombic, space group P2 12 12 1, a = 9.145(2) Å; b = 13.270(3) Å; c = 17.942(4) Å, V = 2177(1) Å3, Z= 4, Dx = 1.22 g cm-3, T = 293 K. The conformation of the molecule is practically identical with the conformation in the dihydrate inclusion complex. Water molecules show proton donor as well as proton acceptor properties and are hydrogen bonded with the three colchicine molecules giving rise to the three dimensional H-bonded network.

Temperature-controlled selectivity of isomeric guest inclusion: enclathration and release of xylenes by 1,1′-binaphthyl-2,2′-dicarboxylic acid

Selectivity of enclathration and desolvation of xylene isomers by a dicarboxylic host depends on temperature.

X-ray structural investigation of gossypol and its derivatives. XXVIII. Separation of the dilactol tautomeric form of gossypol hexamethyl ether into individual stereoisomers and evaluation of their clathrate-forming capacity

All three possible stereoisomers of gossypol hexamethyl ether in the dilactol tautomeric form have been separated with the aid of fractional crystallization and have been identified crystallographically. These stereoisomers have been subjected to x-ray stuctural investigation, and their configurations and clathrateforming properties have been determined.

Clathrates of dianilinegossypol with lower acetate ester homologues: Structure, isomorphism, and morphotropic transitions

The structure of dianilinegossypol clathrates is shown to be sensitive to size of the ester molecule included. The change in the guest component from methyl acetate to amyl acetate is accompanied by two morphotropic transitions in the acetic ester clathrate series and one transition into a nonsolvate dianilinegossypol form.