Lattice dynamical simulations of noble gas hydrate structuresⅠandⅡhave been performed. Potential energies were investigated to study the influence of guest species on the stability of the hydrate structure.Results show that when the diameter of inclusion molecules is between 3(?)and 4.2(?),such as Ar and Kr,the critical role of the 5~(12)cage in the stabilization of hydrates becomes effective.For Xe hydrates SⅠand SⅡ,with the help of lattice dynamical calcnlations,the modes attributions are identified directly.We proposed the resonant effect of the fingerprint frequency at about 7 meV and 10 meV which arise from the coupling of Xe molecules in the 5~(12)cage with the host lattice. 相似文献
Hydrophobic host–guest complexes of some water soluble stable free radicals – potassium nitrosodisulfonate (Fremy's salt), 2-$p$-phenylsulphonic acid-2-phenyl-1-picrylhydrazyl (KSO3-DPPH.) and 2,2-p-phenylsulphonic acid-1-picrylhydrazyl ((KSO3)2DPPH.), both of them as potassium salts, with 18-C-6, B18-C-6 and DB18-C-6 crown ethers, were obtained and characterised by elemental analysis, IR, ESR and UV-Vis. 相似文献
Cellulose nanocrystals (CNCs) spontaneously assemble into gels when mixed with a polyionic organic or inorganic salt. Here, we have used this ion-induced gelation strategy to create functional CNC gels with a rigid tetracationic macrocycle, cyclobis(paraquat-p-phenylene) ( CBPQT 4+). Addition of [ CBPQT ]Cl4 to CNCs causes gelation and embeds an active host inside the material. The fabricated CNC gels can reversibly absorb guest molecules from solution then undergo molecular recognition processes that create colorful host–guest complexes. These materials have been implemented in gel chromatography (for guest exchange and separation), and as elements to encode 2- and 3-dimensional patterns. We anticipate that this concept might be extended to design a set of responsive and selective gel-like materials functioning as, for instance, water-pollutant scavengers, substrates for chiral separations, or molecular flasks. 相似文献
Rhodamine B-ethylenediamine--cyclodextrins (RhB--CDen) and rhodamine B--cyclodextrins (RhB--CD) can form inclusive complexes with many guest molecules, a reaction which can be used as a nucleic acid probe. In this paper, the most stable conformations of RhB--CDen and RhB--CD have been determined by fluorescence experiments and analyzed by molecular modeling simulation. The interaction between RhB--CDen and two guest molecules, 1-borneol and cyclohexanol, has also been investigated. The results showed that RhB--CDen has a stronger interaction with 1-borneol than with cyclohexanol. Borneol could push the three aromatic-rings of rhodamine B out of the CD cavity, while the cyclohexanol could not. The interactive sites of host and guest are also presented. 相似文献
A computer program is presented for the computation of association constants for host/guest compounds based on experimental data obtained from the NMR spectra of samples with different host/guest ratios of known concentration. 相似文献
Dianin's compound(4-p-hydroxyphenyl-2,2,4-trimethyl chroman) forms isostructural clathrates and a clathrand which can be systematically studied to determine the microscopic origins of bulk physical properties. Due to the large number of guests that can be enclathrated in the Dianin's system, experiments in which systematic changes of guest size and functionality can be used to probe guest–host interactions. Herein we report the structures for the1,6-hexanediol, 1,5-pentanediol, and 1-heptanol Dianin's clathrates deduced by X-ray crystallography. In the hexanediol, pentanediol, and heptanol clathrates, the guests' hydroxyl groups hydrogen bond with the host cage's hydrogen-bonded hexamer ring.The two terminal alcohol groups in the diols have different spatial orientations within the cage that result from gauche bonds between atoms in the guest's backbone. 相似文献
Contemporary progress regarding guest/host types of excited‐state double proton transfer has been reviewed, among which are the biprotonic transfer within doubly H‐bonded host/guest complexes, the transfer through a solvent bridge relay, the intramolecular double proton transfer and solvation dynamics coupled proton transfer. Of particular emphases are the photophysical and photochemical properties of excited‐state double proton transfer (ESDPT) in 7‐azaindole and its corresponding analogues. From the chemical aspect, two types of ESDPT reaction, namely the catalytic and non‐catalytic types of ESDPT, have been classified and reviewed separately. For the case of static host/guest hydrogen‐bonded complexes both hydrogen‐bonding strength and configuration (i.e. geometry) play key roles in accounting for the reaction dynamics. In addition to the dynamical concern, excited‐state thermodynamics are of importance to fine‐tune the proton transfer reaction in the non‐catalytic host/guest type of ESDPT. The mechanisms of protic solvent assisted ESDPT, depending on host molecules and proton‐transfer models, have been reviewed where the plausible resolution is deduced. Particular attention has been given to the excited‐state proton transfer dynamics in pure water, aiming at its future perspective in biological applications. Finally, the differentiation in mechanism between solvent diffusive reorganization and solvent relaxation to affect the host/guest ESPT dynamics is made and discussed in de tail. 相似文献
Easy come, easy go? Transport resistances on particle surfaces are important for mass transfer in nanoporous materials and bulk diffusion in crystals. Interference microscopy and IR micro‐imaging are shown to be excellent tools for determining such transport resistances. By studying short‐chain‐length alkane guest molecules in crystals of the metal–organic framework compound Zn(tbip) a data collection of surface permeabilities is established.
