Guest Alcohols Research Articles

Werner clathrates with enhanced hydrogen bonding functionality

The role of hydrogen bonding to generate molecular frameworks for selective enclathration of selected, closely related alcohols, carbonyls and water by three Ni(II) isothiocyanate based Werner hosts was scrutinized and their generation of crystal structures elucidated.Structures of host:guest compounds of H1, Ni(NCS)2(nicotinamide)4, with five alcohols were compared with five guests with carbonyl functionalities. In both cases, host columns formed by interaction via hydrogen bonded amide tetramers. However, the hydrogen bond between the guest alcohol functional group and thiocyanato sulphur showed a more robust structure than those with intercalated carbonyl guests found in layers between sheets of host molecular bands. A predictable framework of H1 host led to architectures with analogous patterns. Physical properties differed according to their hydrogen bonding capabilities. Selectivity was achieved for the separation of a pair of alcohols (1-butanol and 2-pentanol) and a pair of carbonyls (3- and 4-methylcyclohexanone), both difficult to separate due to similar physical properties. The positive discrimination characteristics of host H1 towards one of a pair of alcohols and carbonyl isomers have given possibilities for future industrial prospects.Host H2, Ni(NCS)2(isonicotinamide)4, presented three different tubulate packing arrangements, with the guests (H2O, ethanol and self-included ligand isonicotinamide) occupying channels in the structure. Hydrogen bonding between host carbonyl oxygens and amides formed molecular frameworks into which the guest was included.Mixed-ligand host H3, Ni(NCS)2(nicotinamide)2(isonicotinamide)2 with inclusion of water and methanol, confirmed our findings of hydrogen bonded frameworks with the two different ligands in H1 and H2; nicotinamide ligands formed amide tetramers, whereas the isonicotinamide ligands formed a variety of discrete hydrogen bonds with neighbouring molecules.The host networks formed porous materials for inclusion, giving the advantage of ‘tunability’, and pores with different size and nature available to accommodate guest molecules and to separate isomers.

Precise control of chirality transfer by adjusting the alkyl substituents of guests

Chirality transfer has been investigated with an m-phthalic diamide-linked zinc bisporphyrinate as host and chiral monoalcohols with different alkyl substituents as guests. The substituent of the guest alcohol had a significant effect on chirality transfer. An increase in the number of carbon atoms from one to three resulted in circular dichroism (CD) sign inversion for the corresponding host-guest complexes. The crystal structures of these zinc bisporphyrinate-monoalcohol complexes revealed two types of orientation for the phenyl ring of the guests: one with the phenyl ring facing the porphyrin plane, and the other with the phenyl ring towards the linker. The chirality transfer mechanism was further studied by DFT and revealed that adjusting the chain length of the alkyl substituent could control the steric interaction between the alkyl group and the porphyrin plane, resulting in different chirality transfer outcomes.

Tunability of guest release properties and crystal structures in a supramolecular benzothiophene heterocyclic host complex

A supramolecular benzothiophene heterocyclic host complex was successfully prepared by combining benzo[b]thiophene-3-acetic acid and chiral (1R,2S)-2-amino-1,2-diphenylethanol. Four types of n-alkyl alcohols could be stored as guests in one-dimensional channel-like cavities composed of 21-helical columnar network structures. The release temperatures of the stored guest alcohols could be multiply tuned according to the type of the benzothiophene unit in the complex.

Preparation and Guest Release Properties of Supramolecular 3-Chlorobenzo[b]thiophene Heterocyclic Host Complex

Supramolecular 3-chlorobenzo[b]thiophene heterocyclic host complex composed of chiral (1R,2S)-2-amino-1,2-diphenylethanol was successfully prepared using 3-chlorobenzo[b]thiophene-2-carboxylic acid. Four types of guest n-alkyl alcohols could be stored in one-dimensional channel-like cavities composed of chiral 21-helical columnar network structures. The release properties of the guest alcohol changed depending on the length of the alkyl chain in the alcohol.

Design and Evaluation of Salts between N-Trityl Amino Acid and tert-Butylamine as Inclusion Crystals of Alcohols

Salts between N-trityl amino acids (Ala, Val, Leu, Ile, Phe, and phenylglycine) and tert-butylamine are examined in terms of inclusion ability for alcohols. An X-ray crystallographic study elucidated the column structures, hydrogen-bond network, and phenyl–phenyl interactions. It also found that tert-butylammonium N-trityl phenylalanate was superior to other salts of amino acids at including several alkyl alcohols. When the salt included 1-chloro-2-propanol as a guest alcohol, the enatioselectivity of inclusion reached up to 69% ee (S-form).

Control of release properties of guest molecules by the type of benzoheterocyclic ring in supramolecular host complexes

Three types of supramolecular benzoheterocyclic host complexes were successfully prepared using (1R,2S)-2-amino-1,2-diphenylethanol and three types of benzoheterocyclic (benzothiophene, benzofuran, and benzopyrrole) acid derivatives. The host complexes had one-dimensional (1D) channel-like cavities that were formed by the assembly of two-component 21-helical columnar network structures, which included guest alcohol molecules. The release behavior of the guest molecules could be tuned by the type of heterocyclic ring in the supramolecular host complex.

Preparation of a supramolecular heterocyclic host complex using chiral (1R,2S)-2-amino-1,2-diphenylethanol

Three types of supramolecular heterocyclic host complexes were successfully prepared using chiral (1R,2S)-2-amino-1,2-diphenylethanol and three basic types of heterocyclic (thiophene, furan, and pyrrole) acid derivatives. These host complexes are composed of a chiral 21-helical columnar network structure. It also contains channel-like cavities formed by the assembly of these chiral 21-helical columns, which include guest alcohol molecules.

Alcohol Adsorption onto Silicalite from Aqueous Solution

A methodology based on the combination of grand canonical Monte Carlo (GCMC) and expanded ensemble (EE) simulations has been used to study the adsorption of alcohols from dilute aqueous solution onto the silicalite zeolite. The chemical potential of the guest alcohol molecules in bulk aqueous solutions is calculated by the EE method, and the adsorption isotherms of the alcohols are calculated using GCMC simulations. This approach results in adsorption isotherms that relate the loadings to external concentrations without using an equation of state, experimental data, or performing computationally expensive simulations such as two-phase Gibbs ensemble Monte Carlo (GEMC). Also, the method is “force-field-consistent”, in that the same force field is used for the bulk fluid and the adsorption calculations, and the resulting isotherms can be directly compared with experimental data. We have established the validity of the method used by comparing the calculated adsorption isotherms with experimental data for me...

Inclusion of aliphatic alcohols in pockets of ( S)-threonyl-( S)-phenylglycine using grinding method

Inclusion compounds of a dipeptide, ( S)-threonyl-( S)-phenylglycine (Thr-Phg), with several aliphatic alcohols were easily prepared by grinding them in a mortar. Thr-Phg molecules arranged in antiparallel to construct a sheet, and guest alcohols were accommodated in a chiral pocket between the sheets. 3-Butyn-2-ol and 2-butanol were included with moderate enantioselectivity, 57% ee ( R) and 49% ee ( R), respectively. The role of the hydroxy group of Thr-Phg is not only to construct the unique pocket but also to capture guest alcohols by hydrogen bonding.

A charge-transfer host system composed of a chiral 1,1′-bi-2-naphthol cluster and benzylviologen

Chiral charge-transfer (CT) complexes composed of a chiral 1,1′-bi-2-naphthol cluster as the electron donor and 1,1′-dibenzyl-4,4′-bipyridinium dichloride as the electron acceptor serve as a host system for molecular recognition. CT complexes that include guest alcohols show different diffuse reflectance spectra (DRS) depending on the included guest.

Guest‐Induced Chirality in the Ferrimagnetic Nanoporous Diamond Framework Mn3(HCOO)6

AbstractChiral magnets are obtained by inclusion of chiral guest molecules into the channels of an achiral nanoporous ferrimagnet consisting of the Mn3(HCOO)6 (1) framework. Insertion of the R or the S enantiomer of 2‐chloropropan‐1‐ol (CH3C*HClCH2OH) in the chiral pores of the previously emptied framework (space group P21/c) results in the two corresponding chiral solids (1R and 1S, space group P21), while insertion of a racemic mixture of the two enantiomers retains the achirality of the host for the meso solid (1RS, space group P21/c). The R guest is ordered in the M channels while the S guest is ordered in the P channels. In contrast, the R guests in the P channels and the S guests in the M channels are disordered on two crystallographic orientations. For the racemic mixture of the two enantiomers in 1RS, random disorder of guests in both channels is observed. Thus, the localization of the guest molecule depends on the nature of the surface to recognize the guest of a particular chirality. The guest inclusion compounds are thermally stable. The 1R and 1S compounds are optically active. All the compounds adopt a ferrimagnetic ground state. Compared to the host framework of 1 without guest, the Curie temperature decreases for both 1R and 1S but increases for 1RS. The additional interactions between the framework and the inserted guest alcohols strengthen the lattice via hydrogen bonds and other electrostatic forces, and it might account for the significant lowering of the lattice contribution as well as the magnetic component to the specific heat capacity upon guest loading.

The Effect of a Host–Guest Hydrogen Bond on the Inclusion of Alcoholic Guests in the Host Cavities of Cholamide

AbstractFifty eight inclusion crystals of cholamide (CAM) with aliphatic alcohols have been systematically investigated by X‐ray crystallography. The host frameworks of the inclusion crystals can be categorized into three structural types: bilayer, herringbone, and crossing structures. Most of the guests are included in bilayer structures, which can be further divided into four sub‐types. The host frameworks isomerize depending on the size and shape of the guest molecules. This dependence is clearly evaluated by the relationship between the volume of the guest molecules and the packing coefficient of the void space in the host frameworks. Although the host frameworks with the cavities and the structural isomerization are very similar to those of the inclusion crystals of cholic acid (CA), the inclusion behavior of aliphatic alcohols in the two hosts is completely different: fifty four alcohols can be included in the bilayer‐type structures of CAM, but only two in those of CA. This is attributed to their different functional groups, which lead to different hydrogen‐bond networks with the guest alcohols. The result in the two hosts is a good example to understand the effect of host–guest hydrogen bonds on guest inclusion in cavities that are identical in size and shape. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Studies on molecular recognition in supramolecular systems. Part 31: Circular dichroism spectral studies of molecular and chiral recognition of aliphatic alcohols by 6-modified β-cyclodextrins

The stability constants ( K S) for the inclusion complexation of novel mono[6- O-(1- benzotriazole)]-β-cyclodextrin ( 2) and mono(6-benzylseleno-6-deoxy)-β-cyclodextrin ( 3) with a series of chiral and achiral (cyclo)alkanols have been determined at 25°C in aqueous phosphate buffer solution at pH 7.20 by circular dichroism spectral titration. It was revealed that 2 and 3 can fairly strictly recognize not only the size/shape but also the chirality of guest molecules. Thus, the log K S value, or the Gibbs free energy change (−Δ G 0), increases linearly with increasing number of carbon atoms ( N C) in cycloalkanol, affording comparable increments per methylene unit: −dΔ G 0/d N C=2.0 and 2.2 kJ mol −1 for 2 and 3, respectively. Furthermore, 2 and 3 displayed moderate to excellent isomer selectivities of up to 15.3 for the guest alcohols examined, while moderate enantioselectivities of 1.1–1.4 were obtained with chiral borneol and menthol guests upon complexation with 2 and 3. The present results obtained with 2 and 3 elucidate the effects of substituents on the complexation behavior as well as some of the factors governing size, shape, and chiral selectivities.

Molecular Recognition Study on Supramolecular Systems. 20. Molecular Recognition and Enantioselectivity of Aliphatic Alcohols by L-Tryptophan-Modified beta-Cyclodextrin.

L-Tryptophan-modified beta-cyclodextrin (L-Trp-beta-CD) has been synthesized and its molecular recognition behavior investigated through fluorescence and circular dichroism spectrometry, as well as fluorescence lifetime measurement in the presence and absence of various alcohols as guest molecules. Employing the indolyl group as a spectral probe, spectrofluorometric and spectropolarimetric titrations have been performed in aqueous phosphate buffer solution at pH 7.20 to calculate the complex stability constants for 1:1 inclusion complexation of L-Trp-beta-CD with several series of alcohols at 25 degrees C. The results obtained indicate that L-Trp-beta-CD can recognize not only size/shape and hydrophobicity but also the enantiomeric and geometrical isomers of the guest alcohols, showing a 230-fold molecular selectivity (13.5 kJ mol(-)(1)) for 2-adamantanol over cyclopentanol among the cyclic alcohols examined. Moderate enantiomeric selectivities of 1.2 and 1.9 for (-)-isomers of borneol and menthol, respectively, and geometrical selectivity of 2.0 for geraniol over nerol have also been observed.

Structures of three inclusion compounds of cholanamide with either (S)-enantiomer, (R)-enantiomer or an optically resolved mixture of butan-2-ol

The three types of inclusion compounds of cholanamide (CAM, 3α, 7α, 12α-trihydroxy-5β-cholan-24-amide) have been crystallized from the solutions of (S)-butan-2-ol (CAMSB), (R)-butan-2-ol (CAMRB) and racemic butan-2-ol (CAMSRB), respectively. The crystal structures have been determined. The three crystal structures are isomorphous to each other and revealed that the host CAM molecules form the same layered arrangements, providing channel spaces for the guest butan-2-ol molecules. As expected, the CAMSB and CAMRB crystals include the pure (S)- and (R)-enantiomers of butan-2-ol, whereas the (S)-enriched mixture of enantiomers is accommodated in CAMSRB with a molar ratio between the host CAM and guest butan-2-ol molecules of 1:1. The hydrogen-bond network is rigidly formed between the CAM molecules and also between CAM and butan-2-ol molecules. CAMSB and CAMRB have slightly different unit-cell dimensions: the channels in CAMRB have a larger section, resulting in a larger unit-cell volume. In CAMSRB, although both enantiomers of the guest alcohol are included, the (S)-enantiomer is more abundant, indicating that the optical resolution occurs during the crystallization step.

Structures of 1?1 inclusion complexes of cholic acid with fluoroethanols; Conformational analysis of fluoroethanols in the host cavity

The crystal structures of the inclusion complexes of cholic acid (CA) with 2-fluoroethanol (MFEtOH), 2,2-difluoroethanol (DFEtOH) and 2,2,2-trifluoroethanol (TFEtOH) have been determined by X-ray crystallography, which demonstrates that the guest alcohols are accommodated inside the cavity provided by CA molecules in a similar manner to that for the ethanol molecule in the CA-ethanol inclusion complex. As distinct from the ethanol molecule, the methylene C atoms of the fluoroethanols are not disordered; instead, the substituted F atoms are statistically disordered. All the alcohols are hydrogen-bonded to the OH groups of CA. The X-ray study showed that 46% of MFEtOH adopt thetrans-trans conformer, which is different from the exclusively predominant conformer in the gas and liquid phases, i.e.,thegauche-trans conformer. The study also showed that the F atoms of DFEtOH are statistically disordered, suggesting the possibility that three conformers exist inside the cavity. Such disorder presumably occurs in order to fill the vacant space around the CH2F and CHF2 groups inside the cavity. By contrast, we could not observe any disorder of the F atoms of TFEtOH.

Host-guest compounds. x-ray structure, differential scanning calorimetry, and thermogravimetry of methanol, ethanol, isopropanol, tert-butanol and dioxame Inclusion compounds in 7-benzoyl-6-phenyl-6,7-dihydro-1-methyl-3-methylthio-5[formula omitted]-1.2,4-triazolo[3.4-[formula omitted]][1,3,4]thiadiazinium bromide

The crystal structures of 1a, 1.MeOH, 1b, 1.EtOH, 1c, 1.iPrOH and 1d, 1.2-tBuOH, 1 being 7-benzoyl-6-phenyl-6,7-dihydro-1-methyl-3-methylthio-5H-1,2,4-triazolo[3,4-b][1,3,4]thiadiazinium bromide, have been studied by X-ray diffraction. They crystallize in the space groups P21/c, P21/c , C2/c and P1, respectively, the cell constants being: 11.8790(6), 15.1735(14), 12.6975(9) Å, 90, 98.036(4), 90° for 1a; 11.9894(2), 15.2223(4), 13.0151(3) Å, 90, 96.631(2), 90° for 1b; 20.1583(6), 12.2180(3), 20.8012(6) Å, 90, 105.017(2), 90° for 1c; 12.2747(4), 14.0487(5), 10.1274(3) Å, 94.861(2), 113.728(3), 90.087(3)° for 1d. The four cystals build up with units of “1. alcohol”, quite similar in the four compounds. The host-guest packing schemes are also analyzed. The geometries, including the conformation, of the guest alcohols are compared with experimental and theoretical data from the literature. Some discrepances are observed, but the X-ray analysis of structures containing inclusion compounds, which are liquids at room temperature, seems to be a useful approach, within some stated limits, for studying such compounds.