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Intermolecular interactions in clathrates are compared to those in supramolecular complexes in solution, with an emphasis on van der Waals, or dispersive contributions. The identification of non-covalent interactions with clathrates is complicated by frequent instabilities of crystals and their dependence on the mode of preparation. Thermodynamic versus structural characterization of clathration is discussed with a variety of guest-host systems. The role of empty cavities in clathrates is compared to those in organic container host molecules, also with observation of varying filling factors of the cavities. Many clathrate complexes exhibit a similar negative cooperativity as do synthetic allosteric complexes, leading to a reduced, non-stoichiometric occupation of binding sites. In typical clathrate complexes containing aromatic moieties, stacking interactions based on dispersive forces dominate the interactions, observed in similar free energy values of desorption and corresponding sublimation heats. Effects of H/D isotopic substitution, as visible in particular in differences in the entropy of clathrate formation, are likely due to different dynamics of isotopomers inside the cavities. [ABSTRACT FROM AUTHOR]

Two new derivatives of calix[4]arene bearing on the upper rim 2-thiopenyl (Thicalix) or 2-pyridyl (Pycalix) Schiff-base substituents have been synthesised and characterised by IR, NMR, MS, and single crystal X-ray diffraction techniques. It was shown that the interaction of Thicalix with the copper(II) and palladium(II) ions is accompanied by hydrolysis of the azomethine bonds with subsequent oxidation of the aminophenolic fragment to diquinone Diquin, while the reaction of potassium tetrachloropalladate(II) with Pycalix results in the formation of metallocompex with 1:2 calix[4]arene/Pd(II) ratio. The single crystal X-ray diffraction analysis of Thicalix (1), the complex [(PdCl2)2(Pycalix)] (2) and Diquin (3) revealed that all compounds form molecular crystals as a result of numerous supramolecular interactions involving C − H···O, C − H···Cl, and C − H···π contacts. For 1 and 3 such interactions result in formation of dimers, while in 2 the dodecanuclear palladium aggregates composed of six calix[4]arene moieties are formed. [ABSTRACT FROM AUTHOR]

A novel system of clathrate notation is proposed for use in all types of clathrate-like inclusion compounds, ranging from van der Waals to metallic and from cage to layered and zeolite type topologies. [ABSTRACT FROM AUTHOR]

Six secondary amine palladacycles bearing monodentate ligands (1a,2a), 1,2-bis(diphenylphosphino)ethane (dppe) and 1,3-bis(diphenylphosphino)propane (dppp) containing bridging and bidentate ligands (1b,2b–d), and fourC,C-type phosphorus ylide complexes containing thiourea (tu) (3a), phenyl isothiocyanate (4a), and bridging and terminal azide groups (5and5a) have been synthesized. Resulting complexes have been characterized by elemental analyses, IR,1H-,13C{1H}-, and31P{1H}-NMR spectroscopy with single crystal X-ray structure determination of1aand2a. The Pd in1aand2aoccupies the center of a slightly distorted square planar environment formed byCaryl,Namine,Npyridine, and Cl. The catalytic efficiency of complexes showed that in most cases, amine palladacycles display better catalytic activities than the phosphorus ylide Pd(II) complexes. Comparison between bidentate and bridging dppe complexes showed that dppe-bridged dimer2dhas higher catalytic activity than dppe bidentate complex. [ABSTRACT FROM AUTHOR]

Two rhenium(I) complexes, [Re(CO)3Br(Ln)] (n = 1, 2), (L1= N,N'-bis[1-(4-chlorophenyl)ethylidene]ethane-1,2-diamine and L2 = N,N'-bis[1-(4-nitrophenyl)ethylidene]ethane-1,2-diamine) have been synthesized and characterized by CHN analyses, 1H NMR, IR, and UV-Vis spectroscopy. The molecular structure of [Re(CO)3Br(L1)] is a distorted octahedron around rhenium with one Br, facial arrangement of three CO's, and one diimine. The UV-Vis spectra of the complexes have metal-to-ligand charge transfer bands increasing in wavelength when the L2 ligand is replaced by L1, in agreement with the oxidation potential of the complexes. [ABSTRACT FROM AUTHOR]