Crystalline Inclusion Compounds Research Articles

Novel Inclusion Compounds of Urea with Tetraalkylammonium Pentaborates

New crystalline inclusion compounds (n-C3H7)4N+[B5O6(OH)4]−·4(NH2)2CO·H2O (1) and (n-C4H9)4N+[B5O6(OH)4]−·2(NH2)2CO·B(OH)3 (2) have been prepared and characterized by X-ray crystallography. Crystal data, MoKα radiation: 1, space group P21, Z = 2, a = 8.343(2), b = 16.037(3), c = 13.343(3) Å, β = 104.75(3)°, RF = 0.079 for 1820 observed data; 2, space group P21/n, Z = 4, a = 11.582(3), b = 17.270(4), c = 17.819(5) Å, β = 96.85(3)°, and RF = 0.056 for 2291 observed data. Compound 1 has a channel-like host lattice built of urea molecules, pentaborate ions and water molecules, and the (n-C3H7)4N+ cations are arranged in a zigzag column within each channel. In compound 2 the host lattice comprises a stack of two-dimensional infinite layers of inter-connected urea molecules, pentaborate ions, and neutral B(OH)3 molecules. The (n-C4H9)4N+ cations are sandwiched between adjacent layers, while another most unusual guest component, namely a hydrogen-bonded planar ribbon formed by B3O3(OH)2 fragments belonging to different pentaborate ions, threads the central holes of macrocycles within the stacked layers.

Structural chemistry and guest inclusion of a new supramolecular material showing sensitivity to organic solvent vapors

Clathrate formation—the formation of crystalline inclusion compounds—is one approach to chemical sensing of vapors and gases. The synthesis of a new diol host compound is described and absorptive clathrate formation and thermal clathrate decomposition are reported for acetone as the guest. It is shown that the sorptive uptake of a guest vapor by the crystalline host compound is not merely surface adsorption but true clathrate formation, involving a solid‐state transformation. It is suggested that the use of the host as a chemical sensor is not far off.

Kinetics of desolvation from crystalline inclusion compounds of a diol host with methanol and ethanol

The crystal structures of the inclusion compounds of (4R,5R)-4,5-bis(hydroxydiphenylmethyl)-2,2-dimethyl-1 ,3-dioxolane with methanol and ethanol have been elucidated. Their isothermal kinetics of desolvation have been studied. Both lose the guest in a single deceleratory step, and a kinetic model based on a diffusion mechanism was found to be the best description for this process.

Heterocalixarenes featuring the benzimidazol-2-one subunit. Synthesis and X-ray structural studies of solvent inclusions

The heterocalixarenes 4a,b and 5a–f have been synthesized. Compounds 4a,b and 5a–d were obtained by two-step fragment condensation from benzimidazol-2-one and 1,3-bis(bromornethyl)benzene building elements using blocking/deblocking, high dilution and template (Cs2CO3) techniques to give 4a/5a and 4b/5b in an approximate 1 : 2 or 1 : 3 ratio of the cyclo oligomers. The cleavage of the methyl ether groups of 5a and 5b yielded the tetraphenols 5e and 5f, respectively. The calix hosts 4a, 5a–c and 5f form crystalline inclusion compounds with organic solvent molecules. X-Ray crystal structures of the solvent inclusions 5a·methylene chloride (1 : 1), 5b·toluene·water (1 : 2 : l), Sc·acetone·methylene chloride (1 : 1 : 1) and 5f·toluene (1 : 3) have been studied. The molecular structures show a general trend of having enhanced calix-forming ability compared with conventional calix[8]arenes of the same ring size. The shape of the host molecules appear to be determined by the packing of the symmetry centres of related host molecules on either one of the benzimidazolone rings yielding basket-like hosts (5a–c) or on one of the phenol rings resulting in a chair-like host shape (5f), always exhibiting base-stacking characteristics between the aromatic planes concerned.

Crystalline inclusion compounds of 1-(9-anthryloxy)anthraquinone as a host compound: X-ray structural characterization and π–π interaction modes in the crystal enclathrating benzene as a guest

Inclusion properties of the clathrate crystals, (1)(C6H6) and (1)2(hydroquinone)(C6H6), derived from a conformationally flexible host compound 1-(9-anthryloxy)anthraquinone (1), have been investigated by means of X-ray crystallography, DSC analysis and 2H NMR spectroscopy. Complex (1)(C6H6) is a true clathrate: benzene is embedded in a host lattice constituted of the intermolecular face-to-face π–π overlap (π–π; 3.54 A) of the anthraquinone rings of 1. Crystal data: P21/c, a= 16.882(2), b= 8.970(1), c= 16.405(2)A, β= 91.53(2)°, Z= 4, Dc= 1.280 g cm–3. The crystal structure of a three-component clathrate (1)2(hydroquinone)(C6H6) shows the rigid two-component host lattice composed of 1 and hydroquinone. Crystal data: Pl, a= 11.779(3), b= 12.747(2), c= 8.818(1)A, α= 107.14(1), β= 92.59(3), γ= 101.86(3)°, Z= l, Dc= 1.335 g cm–3. The two host components are linked by the hydrogen bonds (O–O; 2.908, 2.912 A) as well as the unique orthogonal C–H–π–H–C (C–π; 3.2 A) and face-to-face π–π interactions (π–π; 3.43 A). Benzene is retained within the host lattice up to 173 °C. The crystal structure of guest-free host 1 has also been determined. Crystal data: P1, a= 15.566(5), b= 15.625(5), c= 11.571(2)A, α= 98.21(2), β= 94.20(2), γ= 132.74(2)°, Z= 4, Dc= 1.337 g cm –3. 2H NMR spectroscopy has been used to study the molecular motion of [2H6]benzene in the clathrates. Quadrapole echo line shapes, measured as a function of temperature, could be accounted for in terms of an in-plane 60° jump about the major symmetry axis. The activation parameters for a 60° jump are 9.4 and 19 kJ mol–1 for (1)(C6D6) and (1)2(hydroquinone)(C6D6), respectively.

A Tetrachloro Guest in a Molecular Box

The new lattice inclusion host exo-7,exo-15-dibromo-6,7,14,15-tetrahydro-6,14-methanocycloocta[1,2-b:5,6-b'] diquinoxaline (6) has been synthesized in three steps from bicyclo [3.3.1]nonane-2,6-dione and benzofurazan oxide. It preferentially forms crystalline inclusion compounds with small polyhaloalkane guest molecules, and the crystal structure of the 1,1,2,2-tetrachloroethane compound [(C21H14N4Br2)2.C2H2Cl4, Pbcn , a 11.663(2), b 13.195(3), c 27.444(5) Ǻ, Z 4, R 0.041] is described. The key characteristic of this compound is a series of molecular boxes in which the guest molecules reside. Construction of the six surrounding walls is achieved with the aromatic rings of just four host molecules, and the guest molecule occupies a fixed position within the box. The intermolecular forces resulting in formation of this novel inclusion structure are analysed in detail.

Roof-shaped hydroxy hosts: synthesis, complex formation and X-ray crystal structures of inclusion compounds with EtOH, nitroethane and benzene

A series of crystalline host molecules 1 and 2a–e, based on a characteristic 9,10-dihydro-9,10-ethanoanthracene rigid framework and appended diarylmethanol clathratogenic groups, has been synthesized and studied with regard to their inclusion behaviour. These hosts form crystalline inclusion compounds with a variety of uncharged organic molecules, ranging from protic dipolar to apolar compounds (183 different species), but show a preference for amines and aromatic hydrocarbons. The bis-methanols are largely superior to the mono-methanols, except for the 4-chlorophenyl substituted methanol, which has proved to have equal efficiency.The building principles and the mode of complexation of the host compound 2a(trans-α,α,α′,α′-tetraphenyl-9,10-dihydro-9,10-ethanoanthracene-11,12-dimethanol) with ethanol (protic), nitroethane (aprotic polar) and benzene (aprotic apolar) as guests have been investigated by single crystal X-ray diffraction. The conformation of the host molecule observed in the 1 : 2 (host: guest) EtOH complex is different from that in the nitroethane (1 : 1) or benzene (2 : 1) inclusions. The host–guest contact pattern in 2a·EtOH (1 : 2) features a huge 16-membered loop of H-bonds involving four functional OH groups of both host and guest, with one intra-host H-bond for each of the two host molecules of the 2 : 4 (host:guest) aggregate. On the other hand, in the compounds of 2a with the aprotic guest species nitroethane and benzene the host hydroxys are involved in specific intramolecular OH ⋯π-aryl contact, thus yielding true lattice-type inclusions, although with different organizations. Accordingly, in 2a·nitroethane (1 : 1) the polar guest units fill up the voids between the bulky host molecules, while in 2a·benzene (2 : 1) the host molecules are arranged so as to form tunnels in the crystallographic c direction, where the guests are located.

Crystal and molecular structure of the inclusion compound between 1,1′-binaphthyl-2,2′-dicarboxylic acid and acetylacetone (1∶1)

The lattice type crystalline inclusion compound of 1,1′-binaphthyl-2,2′-dicarboxylic acid (BNDA) with acetylacetone (AcAc) 1∶1 has been investigated by single crystal X-ray diffraction. AcAc is present as the enolic tautomer, stabilized by a notably short intramolecular hydrogen bond. This H-bond closes a six-membered ring with delocalization of the system of conjugated double bonds. In the crystal the AcAc molecules are incorporated into channels, delimited by bulky binaphyl moieties, in a hydrogen-bonded framework of BNDA, and they do not show any disorder. The strictly stoichiometric host:guest ratio seems to be enforced by packing forces only.

TheO, O′-dibenzoyl derivative of (R, R)-tartaric acid as a host compound for simple organic ethers

TheO, O′-dibenzoyl derivative of (R, R)-tartaric acid shows a good inclusion ability for diethyl and di-n-propol ethers. The two crystalline inclusion compounds have 1:1 stoichiometry and reveal isomorphous structures. Hydrogen bonded host molecules form chains running along thez axis of the unit cell and guest molecules join to these chains by short O−H...O hydrogen bonds. Hydrogen bonding in the crystals is characterized by a C(7)D first-order network. The ether molecules are in a fully extended conformation. They are accommodated in channel-like voids running along thex axis. Atomic displacement parameters are significantly larger for diethyl ether than for the di-n-propyl ether molecule reflecting less dense packing for this inclusion compound.

A Crystalline Inclusion Compound and Two Host Structures Containing Chiral Molecules Derived from Lactic Acid

The X-ray crystal structures of an inclusion compound with 3-picoline and two free host structures, all based on lactic acid but having different aryl substitution and optical resolution states (S or RS), are reported. They are the 2 :1 complex of (S)-1,1-bis(p-tert-butylphenyl)-1,2-propanediol with 3-picoline, (5) [(S)-1,1-bis(p-tert-butylphenyl)-1,2-propanediol-3-methylpyridine (2/1), 2C 23 H 32 O 2 .C 6 H 7 N], (S)-1,1-bis(p-methylphenyl)-1,2-propanediol, (6), C 17 H 20 O 2 , and (RS)-1,1-bis(1-naphthyl)-1,2-propanediol, (7), C 23 H 20 O 2 . The main structural differences between the host molecules in the three compounds are in the conformation of the phenyl or naphthyl rings. The influence of these rings is reflected in the elongation of the C(1)-C(2) bond in the propanediol moiety [up to 1.560 (5) A] and in the angular distortion of the tetrahedral angles around C(2). The hydroxyl groups play an important role in the crystal packing in all three. Significant differences between these structures and those of the corresponding unsubstituted phenyl host and inclusion compounds are observed.

Structure, conformation, and motions of polytetrahydrofuran (PTHF) in the hexagonal form of the PTHF‐urea inclusion compound

AbstractCombination of differential scanning calorimetry, x‐ray diffraction, Fourier transform infrared, and C‐13 nuclear magnetic resonance observations made on the crystalline inclusion compound (IC) formed between polytetrahydrofuran (PTHF) and urea (U), together with their comparison to identical observations performed on bulk semicrystalline samples of PTHF, have permitted an analysis of the conformations, motions, and environments available to PTHF chains in both solid‐state phases. The isolated PTHF chains occupying the narrow channels of the PTHF‐U‐IC are highly extended, though small rotational deviations averaging 24° from the nearly all trans, planar zig zag conformation of bulk crystalline PTHF chains produce some significant differences in their behaviors. PTHF chains in PTHF‐U‐IC possess much greater mobility than bulk crystalline PTHF chains as evidenced by C‐13 spin lattice relaxation times, T1, 50 times shorter (1.5 s) than observed for bulk crystalline PTHF chains (75 s). FTIR observations are consistent with very little specific interaction between guest PTHF chains and host urea matrix molecules and result in similar spectra for bulk and IC PTHF, except for the presence of the CH2 rocking vibration band at 745 cm−1 observed for bulk PTHF. The absence of this band in the IC PTHF can be understood by considering the symmetry of the all trans, planar zig zag conformation of bulk crystalline PTHF chains, which prevents the CH2 rocking mode from coupling with skeletal stretching and bending modes as occurs in the nonplanar, helical PTHF chains in PTHF‐U‐IC. © 1995 John Wiley & Sons, Inc.

NMR observations of isolated and stretched polymer chains in their crystalline inclusion compounds formed with small‐molecule host clathrates

AbstractSeveral small‐molecule hosts form clathrates or inclusion compounds (ICs) with polymers. In these polymer‐ICs the guest polymer chains are confined to occupy narrow channels in the crystalline matrix formed by the host. The walls of the IC channels are formed entirely from the molecules of the host, and they serve to create a unique solid‐state environment for the included polymer chains. Each polymer chain included in the narrow, cylindrical IC channels (ca 5.5 Å in diameter) is highly extended and also separated by the host matrix channel walls from neighboring polymer chains. The net result is a solid‐state environment where extended, stretched (as a consequence of being squeezed) polymer chains reside in isolation from their neighbors inside the narrow channels of the crystalline matrix provided by the small‐molecule host. Comparison of the behavior of isolated, stretched polymer chains in their crystalline ICs with observations made on ordered, bulk samples of the same polymer are beginning to provide some measure of the contributions made by the intrinsic nature of a confined polymer chain and the pervasive, cooperative, interchain interactions which can complicate the behavior of bulk polymer samples. Just as dilute polymer solutions at the θ temperature have been effectively used to model disordered, bulk polymer phases (both glasses and melts), polymer‐ICs may be utilized to increase our understanding of the behavior of polymer chains in their ordered, bulk phases as found in crystalline and liquid‐crystalline samples. Solid‐state NMR observations of polymer‐ICs can provide detailed conformational and motional information concerning the included, stretched and isolated polymer chains.

Inclusion chemistry of cyclotetraveratrylene

Abstract The structures of four crystalline inclusion compounds of cyclotetraveratrylene (2) (CTTV) containing either chloroform or methylene chloride have been determined by X-ray crystallography. The structures are of the channel inclusion type with solvent molecules ordering to maximize weak host-guest interactions involving the methoxy oxygen atoms of the CTTV hosts.

ChemInform Abstract: Crystalline Inclusion Compounds of Substituted 2,2′‐Bis(9‐ hydroxyfluoren‐9‐yl)biphenyls: Synthesis, X‐Ray Crystal Structures and Thermal Analysis Study of Inclusion Compounds with Butyronitrile, Cyclohexanone, Cyclopentanol and Dimethylformamide.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Conformational and Motional Characterization of Isolated Poly(.epsilon.-caprolactone) Chains in Their Inclusion Compound Formed with Urea

The behavior of isolate poly(E-capro actone) (PEC) chains confined to the narrow channe l of their crystalline inclusion compound (IC) with urea is contrasted with the behavior of PEC chains observed in but, semicrystalline samples. DSC observations of bulk and IC-recovered PEC samples revealed that PEC recovered from PEC-U-IC via extraction with a nonsolvent for PEC produces crystals that melt 6°C higher than PEC samples recrystallized from solution or the melt. Presumably an extended chain morphology results when PEC crystals are obtained from the collapse of PEC-U-IC

Interpretation of Variable Inclusion Abilities of Cholic Acid and Its Derivatives on the Basis of the Crystal Structure of 5β-Petromyzonol

Abstract 5β-Petromyzonol does not form crystalline inclusion compounds with organic substances in contrast to cholic acid, cholanamide and methyl cholate. The crystal structures of these hosts give direct evidence for such an inclusion feature. 5β-Petromyzonol forms greatly different bilayered crystals from other hosts with respect to the hydrogen bonding networks, molecular arrangements, and stacking modes.

Crystalline polymer inclusion compounds: potential models for the behaviour of polymer chains in their bulk, ordered phases

Several small-molecule hosts form clathrates or inclusion compounds (ICs) with polymers. In these polymer ICs the guest polymer chains are confined to occupy narrow channels in the crystalline matrix formed by the host. The walls of the IC channels are formed entirely from the molecules of the host, and they serve to create a unique solid-state environment for the included polymer chains. Each polymer chain included in the narrow, cylindrical IC channels (ca. 5.5 Å in diameter) is highly extended and also separated from neighbouring polymer chains by the host matrix channel walls. The net result is a solid-state environment where extended, stretched (as a consequence of being squeezed) polymer chains reside in isolation from their neighbours inside the narrow channels of the crystalline matrix provided by the small-molecule host. Comparison of the behaviour of isolated, stretched polymer chains in their crystalline ICs with observations made on ordered, bulk samples of the same polymer are beginning to provide some measure of the contributions made by the intrinsic nature of a confined polymer chain and the pervasive, cooperative, interchain interactions which can complicate the behaviour of bulk polymer samples. In the same way that dilute polymer solutions at the Θ temperature have been effectively used to model disordered, bulk polymer phases (both glasses and melts), polymer ICs may be utilized to increase our understanding of the behaviour of polymer chains in their ordered, bulk phases, such as those found in crystalline and liquid-crystalline samples.

Crystalline inclusion compounds of tetrabenzo-18-crown-6 with uncharged organic molecules. Solid-state structure of the nitroethane complex

Tetrabenzo-18-crown-6 (1) shows distinct solid-state inclusion properties towards a number of OH-acidic, CH-acidic and low-polar uncharged organic molecules. The single crystal X-ray analysis of the inclusion complex between1 and EtNO2 (1∶1) is reported. Crystals are monoclinic,P21/c, witha=12.887(1),b=19.365(2),c=10.776(1) A, β=96.33(2)o,Dc=1.321g cm−1,Z=4. The host macroring has a conformation similar to a ‘dentist's-chair’. The complex is stabilized mainly by C−H...O type interactions involving the methyl group of the EtNO2 guest molecule which is highly disordered. The nitroethane guests are trapped in channels formed by the host macrocycles.

Inclusion Compounds of Cholic Acid with Various Hydrocarbons and the Crystal Structure of a 1 : 1 Complex of Cholic Acid and Benzene

Abstract Cholic acid was found to form crystalline inclusion compounds with various hydrocarbons and related compounds. Some alcohols do not form inclusion crystals at all, but serve as solvents. The crystal structure of a 1 : 1 inclusion compound of cholic acid with benzene was determined. Comparative studies on inclusion behaviors of cholic acid and deoxycholic acid are now possible.

Alanine-derived hosts comprising a roof-shaped carbonimide framework. Synthesis, inclusion formation and X-ray crystal structures of racemic and optically resolved free hosts, and their crystalline complexes with 3-methylcyclohexanone

A chiral crystalline host molecule derived from the amino acid alanine comprising a characteristic 9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboximide framework as an inclusion-promoting group has been synthesized in optically resolved and racemic forms and studied with regard to their inclusion behaviour. Dependent on the optical resolution state, this host forms crystalline inclusion compounds with a great variety of uncharged organic molecules ranging from protic dipolar to rather apolar compounds (78 different inclusion species) with the racemic host being more efficient. X-Ray crystal structures of the optically resolved and racemic uncomplexed host species and of their 1:1 inclusion complexes with 3-methylcyclohexanone are reported. The host hydroxy groups are always involved in O–H ⋯ OC intramolecular hydrogen bonds. The crystal packings of both complexes are analogous, showing similar cell dimensions and space groups P21 and P21/a. Moreover, the two independent molecules in the resolved complex are almost related by a pseudo centre of symmetry.