Guest Ratio Research Articles

Selectivity Profiles of 5-(4-Methoxyphenyl)-5H-di benzo[a,d]cyclohepten-5-ol with Aromatic Solvents and Conformational Polymorphism of 10,11-Dihydro-5-(4-methoxyphenyl)-5H-dibenzo[a,d]cyclohepten-5-ol

The structures of the host 5-(4-methoxyphenyl)-5H-dibenzo[a,d]cyclohepten-5-ol, H1, and its inclusion compounds with benzene, bromobenzene, and p-xylene (H:G = 1:0.5) and with pyridine (H:G = 1:1) have been elucidated. The selectivity profiles of H1 with the guests that had the same host:guest ratios were determined for all combination of guests. The structure of the compound 10,11-dihydro-5-(4-methoxyphenyl)-5H-dibenzo[a,d]cyclohepten-5-ol, H2, suffers a phase transformation at 181 K. We compared the polymorphs and concluded that we have obtained a subtle case of conformational polymorphism.

Cucurbit[n]urils (n=7, 8) binding of camptothecin and the effects on solubility and reactivity of the anticancer drug

The interaction between cucurbit[n]uril (n = 7, 8)(Q[n]) with two forms namely lactone modality and carboxylate modality of anticancer drug camptothecin (CPT) was studied. The results revealed that the combination of Q[n] with the lactone form of CPT was observed by electronic absorption spectroscopy, fluorescence spectroscopy and 1H NMR technique in the acid solution (pH 2) and the total stability constants β were also obtained by Job plot with a host:guest ratio of 2:1; while in the phosphate buffer solution (pH 7.4), only Q[8] bound the carboxylate form of CPT in ratio 1:1, but no obvious interaction between Q[7] and the carboxylate form of CPT was observed. The solubility of CPT was enhanced up to about 70 and 8 times at pH 2 due to the formation of interaction complexes with Q[7] and Q[8], respectively, by using phase solubility method. The cytotoxicity tests revealed that compared with the free CPT, the complexes of Q[n] and CPT had the same cytotoxic activity on the human lung cancer cell line A549 and murine macrophage cell line P388D1 and the moderate depressed activity on human leukaemia cell line K562.

Determination of Branched β-Cyclodextrin–Prostaglandin Complexes Using Electrospray Ionization Mass Spectrometry

Mass spectral measurements by electrospray ionization mass spectrometry (ESI-MS) detected the ions of beta-cyclodextrin (betaCD) or branched betaCDs (glucosyl-, galactosyl-, mannosyl- and maltosyl-betaCD)-prostaglandins (PGs: PGA(2), PGD(2), PGE(1), PGE(2), PGF(2alpha) and PGJ(2)) complexes, i.e., betaCD-PG complexes, with a host:guest ratio of 1:1 in the negative ion mode. This is the first study to report the ions of branched betaCD-PG complexes using ESI-MS. The inclusion complexes were determined by a flow injection analysis using acetonitrile/water. We could confirm by this method the presence of a betaCD-PGE(2) complex with a host:guest ratio of 1:1 in a solution-dissolved pharmaceutical formulation consisting of betaCD-PGE(2) (Prostarmon E tablet).

Host–guest Complex of a Water-soluble Cucurbit[6]uril Derivative with the Hydrochloride Salt of 3-amino-5-phenylpyrazole

Interaction between tetramethylcucurbit[6]uril and 3-amino-5-phenylpyrazole hydrochloride in aqueous solution has been investigated by using 1H NMR spectroscopy, electronic absorption spectroscopy and fluorescence spectroscopy, as well as by a single crystal X-ray diffraction determination. The 1H NMR spectra analysis established a basic interaction model in which an inclusion complex with a host:guest ratio of 1:1 forms, in which the host selectively binds the phenyl moiety of the guest. Absorption spectrophotometric and fluorescence spectroscopic analysis in aqueous solution defined the stability of the host–guest inclusion complexes quantitatively as 6.8 × 105 mol− 1 L at pH 2.6; the interaction is pH dependent, decreasing as pH rises. The single crystal X-ray structure of the isolated inclusion complex shows the phenyl moiety of the guest inserted into the host cavity, which supports particularly the 1H NMR spectroscopic study in solution. In the crystal structure of the inclusion complex, the host–guest interaction involves both inter- and intra-complex hydrogen bonding, forming 2:2 dimers that stack in one dimension as supramolecular tubes.

Inclusion Compounds of Dehydrocholic Acid with Solvents

The host-guest inclusion of various organic solvents within dehydrocholic acid has been studied and the selectivity of enclathration determined by competition experiments.

Interaction between Tetramethylcucurbit[6]uril and Some Pyridine Derivates

Interaction between tetramethylcucurbit[6]uril (TMeQ[6], host) with hydrochloride salts of 2-phenylpridine (G1), 2-benzylpyridine (G2), and 4-benzylpyridine (G3) (guests) have been investigated by using 1H NMR spectroscopy and electronic absorption spectroscopy and theoretical calculations. The 1H NMR spectra analysis established an interaction model in which the host selectively included the phenyl moiety of the HCl salt of the above three guests, and formed inclusion complexes with a host-guest ratio of 1:1. Absorption spectrophotometric analysis allowed quantitative measurement of the stability of these host-guest inclusion complexes. Particularly, we have established a competitive interaction in which one host-guest inclusion complex pair is much more stable than another host-guest inclusion complex pair. The stability constants for the three host-guest inclusion complexes of TMeQ[6]-G1, TMeQ[6]-G2, and TMeQ[6]-G3 are approximately 2x10(6), 60.7, and 19.9 mol-1.L, respectively. To understand how subtle differences in the structure of the title guests lead to a significant difference in the stability of the corresponding host-guest inclusion complexes with the TMeQ[6], ab initio theoretical calculations have been performed, not only for the gas phase but also the solution phase (water as solvent) in all cases. The calculation results revealed that when the phenyl moiety of the three pyridine derivate guests was included, the host-guest complexation reached the minimum, and the corresponding energy differences for the formation of the title host-guest inclusion complexes are qualitatively consistent with the experimental results.

Cholic acid as host for long linear molecules: a series of co-crystals with n-alkylammonia

Co-crystals of cholic acid (CA) with n-alkylammonia (n = 10, 12, 14, 16) represent the first examples of CA's co-crystals with molecules of comparable size. In one of the compounds a completely new type of bilayer arrangement was found. The host–guest ratio in crystals was found to be 1 : 1 in three cases and 2 : 1 in one case. In 1 : 1 complexes CA molecules are assembled in bilayers and n-alkylammonia guests are included in the hydrophobic zones between those layers in a kind of sandwich-type structure. In the 2 : 1 complex the CA molecules include guest molecules in a different way: bilayers are not parallel but instead they cross and form one-dimensional hydrophobic channels into which guest molecules are included. In the case of 1 : 1 co-crystals the bilayers of CA are separated much more than in previously reported structures in order to accommodate large n-alkylammonia molecules. In spite of the different bilayer arrangements the characteristic spacing in the plane of CA bilayers is remarkably similar to the majority of other CA crystal structures known to date.

Separation by Inclusion: Selectivity by Tetraphenylethanediol of Toluene and Mono-halo Substituted Benzenes

The host 1,1,2,2-tetraphenyl-1,2-ethane diol was found to form inclusion compounds with the guest toluene and three mono-halo substituted benzenes; chloro-, bromo-, and iodo-benzene. These compounds were characterised by thermal analysis, which showed host:guest ratios of 1:1/2, and their structures were elucidated and compared. Two-, three- and four-component competition experiments were conducted to investigate the selectivity of the host for the respective guests and to determine the separation capabilities of this system.

Formation of supramolecular permethrin/β-cyclodextrin nanorods

Molecular dynamics simulations along with scanning tunneling microscopy (STM) imaging demonstrate the formation of a novel type of nanorods, with a stable [permethrin(beta-CD)(2)](n) structure in which the host:guest ratio is 2:1 and n=21-27 giving a length of approximately 30.0-38.5 nm and an average diameter of approximately 1.5 nm, self-assembled from an inclusion complex composed of permethrin and biocompatible beta-cyclodextrin.

Dianin's compound trichloroacetonitrile clathrate

The the title compound [systematic name: 4-(2,2,4-trimethyl­chroman-4-yl)phenol–trichloro­acetonitrile (6/1)], 6C18H20O2·C2Cl3N, the usual trigonal packing of the Dianin's compound host structure occurs. The guest is found in a host–guest ratio of 6:1. Cl⋯π inter­actions serve to order the guest, thus facilitating its structural characterization.

Inclusion properties of quinolines by a diol host compound

1,4-bis(9-hydroxyfluoren-9-yl)benzene (H) is a versatile host compound which conforms to EdwinWeber’s host design specifications in that the molecule is rigid and bulky and contains hydroxyl moieties, which are good hydrogen-bond donors. In literature, this compound has been employed for the separation of the isomers of lutidine [1] and for the guest exchange between acetone and DMSO . The guest selectivity between aniline and benzylamine by this host has been studied and was found changed dramatically by controlling PH . In this study we investigate the inclusion properties of the host compound towards quinoline(Q), 2-methylquinoline (2MeQ), 6-methylquinoline (6MeQ) and 8-methylquinoline (8MeQ) ( see Scheme). All the guests formed inclusion compounds with the same host:guest ratio. Single x-ray crystal structures of the inclusion compounds have been elucidated and are all stabilised by (host)O-HcccN(guest) hydrogen bonds. Thermal stabilities were studied by Thermogravimetry (TG). Competition experiments were carried out to study the guest selectivity.

Further development of the general rule on correlation between host–guest ratio and topology of polymorphic inclusion compounds and their crystallization temperatures

Further development of the general rule on correlation between host–guest ratio and topology of polymorphic inclusion compounds and their crystallization temperatures

Inclusion of volatile guests by a tetrapedal host: structure and kinetics

The host compound tetra(3-hydroxy-3,3-diphenyl-2-propynyl)ethene, TET, forms inclusion compounds with acetone, dimethyl sulfoxide, dioxane and pyridine. All the structures were successfully solved in the triclinic space group P1[combining macron]. We found variable host : guest ratios for the acetone (TET.ACE, H : G = 1 : 4), dimethyl sulfoxide (TET.DMSO, H : G = 1 : 4) and pyridine compounds (TET.PYR, H : G = 1 : 5). Solutions of the host compound and dioxane formed TET.2DIOX, H : G = 1 : 2 when left to crystallise at room temperature, whereas TET.4DIOX, H : G = 1 : 4 was formed during crystal growth at low temperature. We have correlated the structures with their thermal stabilities and kinetics of desolvation.

Luminescent host–guest complexes involving molecular clips and tweezers and tetracyanobenzene

The molecular tweezer 1 and the clips 2 and 3, containing naphthalene or anthracene in the sidewalls, form host–guest complexes in CHCl3 solution with the guest TCNB (1,2,4,5-tetracyanobenzene). The interaction leading to formation of the adduct is essentially of CT (charge-transfer) nature. A luminescence emission of CT origin is observed from the host–guest complexes both in fluid solution at 298 K and in rigid matrix at 77 K; to our knowledge, this is the first case of CT luminescence from a host–guest complex. At room temperature, the luminescence maxima are observed at 570, 614, and 668 nm, respectively, for the complexes based on the hosts 1, 2, and 3. Spectrophotometric and spectrofluorimetric titrations were performed to investigate the association processes. In all cases 1∶1 complexes are formed, with association constants 7.3 × 105, 5.4 × 106, and 1.24 × 104 L mol−1, respectively, for the receptors 1, 2, and 3. In the case of 2, a species with a 2∶1 host∶guest ratio is also formed. The system 1+TCNB was further investigated by cyclic and differential pulse voltammetry, giving the rate constants for adduct formation (1.9 × 108 L mol−1 s−1) and disassembling (2.0 × 102 s−1). The association/dissociation dynamics between the receptors 1 and 2 and the guest TCNB is discussed in relation to the receptor topology.

Drastic Increase in the Flexibility of Open Host Frameworks of a Steroidal Host Compound upon Shortening Its Spacer

AbstractNordeoxycholic acid (NDCA), which has a shorter side chain than the steroidal host compound, deoxycholic acid (DCA), forms inclusion crystals with various organic substances at 1:1 or 2:1 host−guest ratios. X‐ray crystallographic studies reveal that four types of host frameworks (bilayer, monolayer, tape, and hexagonal) are generated by NDCA, in stark contrast to the robust and dominant bilayer frameworks formed from DCA, although they have the same functional groups capable of hydrogen bonding. The first three host frameworks are further divided into three, two, and four sub‐types by arrangements of the hydrogen‐bonded host columns, tapes, or layers, respectively. A total of nine types of open host frameworks are observed depending on the nature of the guest compounds. The sizes of the guest compounds induce isomerization of these host frameworks having molecular cavities, which is rationalized by the range of values of PCcavity, which are ratios of the volumes between the guest compound and the host cavities. Such a drastic increase of flexibility of the open host framework by the slight chemical modification from DCA to NDCA deserves attention with respect to crystal engineering. Unique 21 helical assemblies of DCA are linked by the carboxyl group at the side chain to form a robust sheet‐like structural motif. In NDCA, on the other hand, the linkage between the helices becomes impossible because of the shortening of the side chain’s length, which results in destruction of the sheet‐like motif to yield renewed molecular voids among the unique 21 helical assemblies. These remarkable differences in the flexibility of the open host frameworks provide us with a possible strategy for designing of new host compounds. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

PH control of guest selectivity by inclusion

The structures of the inclusion compounds formed by a diol host with aniline and benzylamine have different host ∶ guest ratios and topologies. Competition experiments show that guest selectivity is dramatically changed by pH control.

Inclusion Properties and Solid‐State Behavior of Thiophene‐Condensed Host Compounds.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Inclusion Properties and Solid-State Behavior of Thiophene-Condensed Host Compounds

Abstract A series of new clathrate host molecules, each containing thiophene rings as a rigid and bulky substituent, has been synthesized based on the “wheel and axle”-type of host design. The interest in these hosts is focused on the continuous change in the length of the “axle” part together with their electron-donating ability. Moreover, the tertiary alcohol moiety in the “wheel” part can undergo the substitution reactions in the solid state. Thus, the host : guest ratio and the conformation of the host molecules exhibit novel dependences on the number of the condensed thiophene rings. Guest exchange via gas solid contact has been achieved in the clathrates which provide a channel-type inclusion void. Isostructural and polymorphic transformation of the host lattices has been found upon gas-solid contact. Pseudo-polymorphic change was also observed in guest release. Ternary crystals exhibited novel site-selectivity for random inclusion of two alcohol guests. The donor character of the hosts can afford three-component charge-transfer complexes enclathrating solvent molecules. Cogrinding the host and the acceptor enhanced the solid-state charge transfer interactions, which have been associated with the nucleophilic substitution in the solid state induced by gas-solid contact. These results indicate one future direction for research on crystalline inclusion complexes.

THE CRYSTAL STRUCTURE OF 1:2 MOLECULAR COMPLEX OF OCTYLTRIMETHYLAMMONIUM BROMIDE WITH R-(+)-1,1′-BI-2-NAPHTHOL

The complex formed between octyltrimethylammonium bromide (8TAB) and (R)-(+)-1,1'-bi-2-naphthol (RBNP) crystallizes in the monoclinic space group P2 1 with one crystallographically independent 8TAB molecule and two crystallographically independent RBNP molecules in the asymmetric unit. The crystal structure demonstrates that the nonplanar shape of the RBNP molecule affects the packing mode of the alkyl chains. The host:guest ratio as well as the length of the alkyl chain play significant roles in the packing structure of the complex. The alkyl chain does not have an all-trans fully extended conformation but one which is bent. The hydrogen bonds and C-H… ~ interactions stabilize the crystal structure of the complex.

Inclusion compounds of binaphthol with volatile guests: structures, selectivity and kinetics of desolvation

Binaphthol forms inclusion compounds with 1,4-dioxane, morpholine, dimethylsulfoxide, acetone and tetrahydrofuran. The host∶guest ratios of some of these compounds depend on the crystallisation temperature. Competition experiments between pairs of selected guests reveal different kinds of selectivity. Desolvation kinetics for these compounds yield similar activation energies of approximately 80 kJ mol−1.