Werner clathrates

Analytically, the inclusion phenomenon has been used in chromatography both for the separation of ions and molecules, in Hquid and gas phase (1,79,170,171). Peralkylated cyclodextrins enjoy high popularity as the active component of hplc and gc stationary phases efficient in the optical separation of chiral compounds (57,172). Chromatographic isotope separations have also been shown to occur with the help of Werner clathrates and crown complexes (79,173). 

In the Beginning Hoffman Inclusion Compounds and Werner Clathrates... 

Closely related to DSC is the much older technique of differential thermal analysis (DTA). DTA works on the simpler principle of measurement (via thermocouple) of temperature difference between a sample and reference as the same heating power is supplied to both. The DTA trace therefore represents a temperature effect, which is related only semiquantitatively to AH. A combined DTA-TGA trace for the Werner clathrate (Section 9.4) [Ni(NCS)2(4-phenylpyridine)4] CgHg is shown in Figure 9.22. The DTA trace shows that all three thermal events observed are endothermic. The first is associated with loss of the benzene guest, while the second and third relate to loss of the coordinated 4-Phpy ligands. Note the high temperature (about 350 °C) required to remove the enclathrated benzene. This is a clear indication of the thermal stability of the Werner clathrate family.18... 

Prussian blue was the first coordination polymer and has found extensive applications as a dye and ink. It has inspired the related Hoffman clathrates which are also CN bridged coordination polymers. In contrast Werner clathrates are based on discrete coordination complexes as the host but they do display some of the robustness of coordination polymers. 

Lavelle, L., Nassimbeni, L. R., Niven, M. L., Taylor, M. W., Studies in Werner Clathrates. 2. Structure and thermal-analysis of bis(isothiocyanato)tetrakis(4-phenylpyridine)nickel(n) benzene clathrate (1-4). Acta Crystallogr. Sect. C-Cryst. Struct. Commun. 1989, 45, 591-595. 

Ishida, K. Matsuo, T. Suga, H. Zielenkiewicz, W. Lipkowski, J. Low temperature properties of the Werner clathrate inclusion compounds. Isotopic p-xylenes in tetrakis (4-methylp3nidine) nickelfll) thiocyanate. J. Chem. Thermodyn. 1998, 30, 1289. 

So-called Werner clathrates are another prominent series of clathrate compounds formed between a metal complex host and an aromatic guest molecule. The name Werner originates from A. Werner, who established the coordination theory of metal complex compounds. The host of the series has a general formula [M(NCS)2(4-Mepy)4], and in fact, the series is obtained conceptually by replacement of C N and NH3 in the Hofmann-type host by SCN and 4-Mepy (4-methylpyridine), respectively. This was done in order to increase the inclusion capability for bulkier substituted aromatic molecules, in particular, those related to the petroleum industry. 

Hofmann-type clathrates Werner clathrates clathrate hydrates inclusion compounds of urea, thiourea, and selenourea cyclodextrins calixarenes gossypol hexa-hosts hydroquinone phenol and Dianin s compounds graphite intercalates natural and pillared clays and others. Such studies contributed to the birth of supramolecular chemistry, with relevance to a new understanding of the world of materials that was emphasized with a Nobel Prize. 

Lipkowski, in his analysis of the energetics of formation of Werner clathrates, adds an enthalpic term for the dilation of the yd-lattice when it accommodates the guest. This term is dependent on the size of the guest as well as the... 

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