Alcohol Guests Research Articles

Role of Rim Functions in Recognition and Selectivity of Small-Molecule Guests in Water-Soluble Cavitand Hosts.

Groups on the upper rim of cavitands can play major roles in the recognition of small molecules. Water-soluble deep cavitands 1, 2 or 3 bearing the walls upper rim of imidazole, urea, and methyl urea, respectively, were synthesized and characterized as hosts of small-molecule guests. The vase forms of 1 or 2 are stabilized through H-bonding to solvent water molecules between adjacent walls. Various small alkyl organic molecules - alcohols, halides, cycloalkane derivatives and heterocycles - are efficiently bound in 1. For n-alcohols (C5 to C12), the -OH end is fixed at the upper rim and the alkyl parts are in the hydrophobic cavity. The longer alcohol guests (C7-C12) show coiling. Cycloalkane guests rotate rapidly on all 3 axes within the host cavity, while heterocycles show orientations placing their heteroatoms near the cavitand rim. Competition studies between alkyl chlorides, bromides and iodides showed preference for binding of iodides in 1. Competition between cavitands for hexyl halide guests halide showed the order 2>1>3.

Enantioselective Recognition of Racemic Amino Alcohols in Aqueous Solution by Chiral Metal-Oxide Keplerate {Mo132 } Cluster Capsules.

Determining the relative configuration or enantiomeric excess of a substance may be achieved using NMR spectroscopy by employing chiral shift reagents (CSRs). Such reagents interact noncovalently with the chiral solute, resulting in each chiral form experiencing different magnetic anisotropy; this is then reflected in their NMR spectra. The Keplerate polyoxometalate (POM) is a molybdenum‐based, water‐soluble, discrete inorganic structure with a pore‐accessible inner cavity, decorated by differentiable ligands. Through ligand exchange from the self‐assembled nanostructure, a set of chiral Keplerate host molecules has been synthesised. By exploiting the interactions of analyte molecules at the surface pores, the relative configuration of chiral amino alcohol guests (phenylalaninol and 2‐amino‐1‐phenylethanol) in aqueous solvent was establish and their enantiomeric excess was determined by 1H NMR using shifts of ΔΔδ=0.06 ppm. The use of POMs as chiral shift reagents represents an application of a class that is yet to be well established and opens avenues into aqueous host‐guest chemistry with self‐assembled recognition agents.

DFT study of guest-responsive cooperative effects: Inclusion complexation of alcohols with calix[4]pyrrole

Herein, we report guest-responsive structural changes and cooperative effects in inclusion complexes of meso-octamethylcalix[4]pyrrole. A series of lower alcohol guests were modeled using the density functional theory at B97D/6-311 + G* and ωB97D/6-311 + G* level of approximation to study their thermochemical properties and complexation geometries. Results of binding energies of CP:1-alcohol and CP:2-alcohol complexes indicated that the methylene glycol exhibited strongest binding, whereas ethane-1,2-diol has the highest cooperative effects. Attempts were also made to address the cooperative effects by correlating them with the partial charges (Hirshfeld, Atomic Dipole Corrected Hirshfeld) and the second-order energy interactions.

Unidirectional complexation of pillar[4]arene[1]benzoquinoneoxime with alkyl alcohols.

Despite progress in the unidirectional complexation of cyclodextrins and calixarenes with nonsymmetric guests, unidirectional complexation using pillararenes as hosts remains scarcely explored. In this report, we describe the formation of unidirectional [2]pseudorotaxane-like complexes which were realized using n-alkyl alcohol guests and pillar[4]arene[1]benzoquinoneoxime made from pillar[4]arene[1]quinone in a selective monofunctionalizing manner.

Synthesis and structures of crystalline solvates formed of pyridinium N-phenoxide (Reichardt's-type) betaine dyes and alcohols

Four new betaine dyes of the Reichardt's type featuring two tolyl substituents in different attachment (2–4) or being an analogous 1-naphthyl derivative (5) have been synthesized and described with reference to their negative solvatochromism. The dinaphthyl derivative 5 and also a corresponding intermediate nitrophenol 9d were shown with variable-temperature NMR spectroscopy to form conformational atropisomers in solution. Crystal structures of seven alcoholic solvent complexes including the unsubstituted parent compound (1) and different alcohols [1·EtOH (1 : 1), 1·i-PrOH (1 : 1), 2·MeOH (1 : 2), 3·i-PrOH (1 : 1), 3·n-BuOH (1 : 1), 4·EtOH (1 : 2) and 5·MeOH (1 : 3)] have been studied using X-ray diffraction methods. The betaine dyes exist as genuine zwitterion ground state structures in the solid state with twisted conformation between the phenoxide and pyridinium rings. With the exception of 3a [3·i-PrOH (1 : 1)], the alcohol guests in the complexes are hydrogen bonded to the oxygen atom of the phenoxide units, whereas in the i-PrOH complex of 3, the alcohol forms trimeric clusters without specific interaction with the betaine framework. From the packing modes in the crystals, the solvated betaines may be classified either as co-ordination type inclusion compounds with pocket-like host arrangements [1·EtOH (1 : 1), 1·i-PrOH (1 : 1), 2·MeOH (1 : 2), 3·n-BuOH (1 : 1), 4·EtOH (1 : 2) and 5·MeOH (1 : 3)], or a true clathrate with channel-type topology [3·i-PrOH (1 : 1)].

Preparation and Crystal Structure of Guest-Dependent Charge-Transfer Host System Using 1,1′-Bi-2-naphthol and 2-Chloro-5-methyl-benzoquinone

A guest-dependent charge-transfer (CT) host system was found that was composed of racemic (rac)-1,1′-bi-2-naphthol as an electron donor and 2-chloro-5-methyl-benzoquinone as an electron acceptor; in this complex, aromatic guests (benzene/toluene), electron-acceptor guests (tetrafluoro-1,4-benzoquinone (TF-BQ)), or alcohol guests (ethanol) can variously be included by changing the packing of electron-donor and -acceptor molecules. When ethanol was used as a guest, a chiral CT complex including ethanol was obtained.

Fluorescent Detection for Cyclic and Acyclic Alcohol Guests by Naphthalene-Appended Amino-β-cyclodextrins

Spectroscopic and thermodynamic investigations on complexation of naphthalene-appended amino-beta-cyclodextrins 1 and 2 with cyclic alcohols (cyclohexanol and cycloheptanol) and acyclic alcohols (1-pentanol, 2-pentanol, 1-hexanol, and 1-heptanol) have been carried out. Host 1 exhibits a drastic fluorescent enhanced-signal change in the presence of alcohol guests in aqueous solution. [structure: see text]

Enthalpy-entropy compensation upon syn-anti conformational switching of bis-porphyrins by amines and alcohols

Upon interaction with amine and alcohol guests, Zn - Zn and Zn -2 H ethane-bridged bis-porphyrin hosts undergo dramatic conformational switching from a syn to an anti form. The thermodynamic parameters obtained exhibit excellent linear enthalpy-entropy correlations, which are distinctly different for amines and alcohols but essentially independent of the host structure. Analyses of the compensation plots reveal a more rigid complex structure and more extensive desolvation upon complexation with amines than for alcohols, which may be ascribed to the different nucleophilicity, binding strength, solvation and geometry.

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.

An exceptionally stable peptide nanotube system with flexible pores.

The hydrophobic channels in the structure of the dipeptide L-alanyl-L-valine act as supramolecular hosts for organic solvent molecules. In a series of data collections, it is demonstrated that small molecules like acetonitrile, methanol and acetone can be removed from the channels by drying without impairing the structure of the hydrogen-bonded peptide host structure. The title compound is one of the very first organic molecules to be found to have this property. Alcohol guests larger than methanol are also absorbed, but they induce a doubling of two axes and a change in the shape and size of the pores. The observed structural modifications explain why these solvent molecules are more or less irreversibly trapped inside the channels.

On the balance of interaction modes in supramolecular complexes of a carboxylic acid host and alcohol guests. X-ray crystal structures of inclusion compounds with MeOH and EtOH

Remarkable differences have been observed between the host–guest interaction modes in two closely related crystalline inclusion compounds [ 1·MeOH (1:1) and 1·EtOH(1:1)] of the same carboxylic host ( 1). The minor modification of the guest structure crucially affected the hydrogen bonding recognition pattern between given complementary groups, which demonstrates the sensitive balance of intermolecular interaction modes that must be controlled for successful crystal engineering and design of supramolecular compounds.

Clathrate and Inclusion Compounds. Part 12. Vibrational and NMR Spectroscopic Studies of Carboxylic Acid Guests in Dianin's Compound

Infrared, Raman and solid state 13C-NMR spectra have been recorded for a range of clathrates of Dianin's compound containing straight chain aliphatic carboxylic acids (formic - octanoic) as guests. The IR, Raman and NMR spectra can be satisfactorily interpreted in terms of dimer (formic and acetic) and monomer (propionic - octanoic) occupation of the cavities. The clathrates containing straight chain alcohol guests (methanol - octanol) have also been prepared to aid in the interpretation of the NMR data.

ChemInform Abstract: New Crystalline Hosts Based on Tartaric Acid. Synthesis, Inclusion Properties, and X‐Ray Structural Characterization of Interaction Modes with Alcohol Guests.

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.

New crystalline hosts based on tartaric acid. Synthesis, inclusion properties, and x-ray structural characterization of interaction modes with alcohol guests

A series of host molecules derived from tartaric acid have been synthesized in optically resolved and racemic forms. Apart from two endo hydroxyl functions and four bulky aromatic groups (TADDOL-type=α,α,α',α'-tetraphenyl-1,3-dioxolane-4,5-dimethanols), they have specific polar and apolar substituents of different size, in different number, and in different positions laterally attached to the molecular framework as the characteristic features