Journal of inclusion phenomena

In this work, the electronic, structural, dynamic andthermodynamic properties of structure II, H and tetragonalAr clathrate hydrates have been calculated and the effectof multiple occupancy on their stability has been examinedusing first-principles and lattice dynamics calculations.The dynamic properties of these clathrates have beeninvestigated depending on the number of guest moleculesin a clathrate cage. It has been found that selectedhydrate structures are dynamically stable. The calculatedcell parameters are in agreement with experimental data.We also report the results of a systematic investigationof cage-like water structures using first-principles calculations. Ithas been observed that Ar clusters can be stabilized indifferent water cages and the stability is strongly dependenton the number of argon atoms inside the cages.

This current work has been conducted mainly to increase solubility and drug release properties for high hydrophobic Dentatin (DEN) by incorporation it into Hydroxypropyl-β-Cyclodextrin (HPβCD) cavity. To confirm that inclusion be succeeded, the produced complex were installed onto different machines. The latter includes: Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD), differential scanning calorimetry (DSC), and field emission-scanning electron microscopy (FE-SEM). The hydrodynamic diameter and zeta potential of DEN-HPβCD complex were 2.025 ± 0.39 nm and −33.6 mV, respectively. Ultra-violet spectroscopy was employed to further confirmation of complexation process as well as to determine drug release profile. The result showed an initial burst release (19.9% within first two minutes) and then a continuous release for an extended period of 41 h (100%). The solubility of DEN was enhanced by >300 fold following complexation when a compared to DEN alone. Moreover, MTT finding showed that this complexation did not reduce cytotoxicity of DEN after applying on prostate cancer (LNCaP), human adenocarcinoma breast cancer (MDA-MB-231) and human gastric adenocarcinoma cell line (HDT). However, further investigations are required to validate efficacy of our produced inclusion using molecular analysis and in vivo studies.

PM3 calculations in vacuum were performedon the inclusion complexation ofβ-cyclodextrin (β-CD),heptakis-(2-O-methyl)-β-cyclodextrin(2-Me-β-CD) and heptakis-(6-O-methyl)-β-cyclodextrin(6-Me-β-CD) withibuprofen (IB) enantiomers. Inclusion processpathways are described and the most probablestructure of the 1:1 complex are sought througha potential energy scan. The energy differencesbetween the inclusion complexes and the hosts(native and modified CDs) by calculation show thatmodified CDs have much more interaction sites withIB and enhance van der Waals interaction andhydrophobic interaction between them, form morestable complexes than native CD does.Stabilization energies of S-IB complexes arehigher than that of R-IB complexes both for nativeand modified CDs.

A pyrimidine based receptor (pyrimidine amine linked xylene spacer) has been synthesized for recognition of dicarboxylic acids. Binding studies have been performed by UV–vis method by varying the chain length of dicarboxylic acids. The downfield chemical shift of amine protons of receptor in presence of adipic acid or glutaric acid and the 1:1 dimeric crystal structure of the receptor and adipic acid reveal the strong binding interaction.

The stability constants of 1:1 (M:L) complexes of benzo-15-crown-5 (B15C5) with Li+, Na+, K+ and NH4 + cations, the Gibbs standard free energies ( $$ \Updelta {\text{G}}_{\text{c}}^{ \circ } $$ ), the standard enthalpy changes ( $$ \Updelta {\text{H}}_{\text{c}}^{ \circ } $$ ) and standard entropy changes ( $$ \Updelta {\text{S}}_{\text{c}}^{ \circ } $$ ) for formation of these complexes in acetonitrile–methanol (AN–MeOH) binary mixtures have been determined conductometrically. The conductance data show that the stoichiometry of the complexes formed between the macrocyclic ligand and the studied cations is 1:1 (M:L). In most cases, addition of B15C5 to solutions of these cations, causes a continuous increase in the molar conductivities which indicates that the mobility of complexed cations is more than the uncomplexed ones. The stability constants of the complexes were obtained from fitting of molar conductivity curves using a computer program, GENPLOT. The results show that the selectivity order of B15C5 for the metal cations changes with the nature and composition of the binary mixed solvent. The values of standard enthalpy changes ( $$ \Updelta {\text{H}}_{\text{c}}^{ \circ } $$ ) for complexation reactions were obtained from the slope of the van’t Hoff plots and the changes in standard entropy ( $$ \Updelta {\text{S}}_{\text{c}}^{ \circ } $$ ) were calculated from the relationship $$ \Updelta {\text{G}}_{{{\text{c}},298.15}}^{ \circ } = \Updelta {\text{H}}_{\text{c}}^{ \circ } - 298.15\Updelta {\text{S}}_{\text{c}}^{ \circ } $$ . A non-linear behavior was observed between the stability constants (log Kf) of the complexes and the composition of the acetonitrile–methanol (AN–MeOH) binary solution. The results obtained in this study, show that in most cases, the complexes formed between B15C5 and Li+, Na+, K+ and NH4 + cations are both enthalpy and entropy stabilized and the values of these thermodynamic quantities change with the composition of the binary solution.

Electron spin resonance (ESR) spectroscopy was used to study the photodecomposition of long-chain diacyl peroxides trapped in channels within zeolites (silicalite and ferrierite) and urea clathrates. ESR spectra of radical pairs in single crystals of the urea clathrates of diundecanoyl peroxide (UP), lauroyl peroxide (LP) andbis(6-bromohexanoyl) peroxide (6-BrHP) show that the alkyl radicals respond to the CO2 stress field by recoiling along the channel. In each clathrate, the inter-radical distance for the most relaxed pair is approx. 9.5 Å, suggesting nearly complete relaxation of stress from the CO2s. The rotational mobility and exceptional kinetic stability of the radicals is attributed to relaxation of stress and the lack of a convenient escape route for the CO2s. X-ray diffraction indicates one-dimensional ordering of guests in 6-BrHP/urea and 3-dimensional ordering of guests in UP/urea. Solid state NMR experiments on LP/urea suggest high guest mobility under ambient conditions. When UP and 6-BrHP were intercalated into silicalite, photolysis yielded isolated radicals, but no radical pairs, even as low as 20 K.

Nitropyridine substituted double-armed benzo 15-crown-5 compounds (1–4) were synthesized by the reactions of 4′,5′-bis(bromomethyl)benzo-15-crown-5 with hydroxypyridine derivatives. Na+ and K+ complexes (1a–4a, 1b–4b) of crown ether compounds (1–4) were prepared with sodium picrate and potassium picrate, respectively. Transition metal complexes (1c–4c) of the synthesized ligands (1–4) were prepared from Ag+ cation. In addition, nitro compounds (1, 2 and 4) were reduced by using Pd/C and hydrazine hydrate and new amine compounds (5, 6 and 8) were obtained. The structures of new double-armed crown ether compounds (2–4), their metal complexes (1a–4a, 1b–4b, 2c–4c) and amine compounds (5, 6 and 8) were elucidated by FTIR, HRMS, 1H–NMR, 13C–NMR spectroscopic methods. The thermal behaviors of these nitro group containing ligands (1–4) were compared with the resulting silver complexes (1c–4c) and amine compounds (5, 6 and 8). All synthesized compounds were examined for antibacterial activity against pathogenic strains Listeria monocytogenes, Salmonella typhi H, Bacillus cereus, Staphylococcus aureus, Staphylococcus epidermidis, Micrococcus luteus, Escherichia coli, Klebsiella pneumonia, Proteus vulgaris, Serratia marcescens, Shigella dysenteria and antifungal activity against Candida albicans.