Inclusion of a dithiadiazolyl radical in a seemingly non-porous solid

Inclusion of the dithiadiazolyl radical PhCNSSN• into the dynamically porous metallocycle [Cu2(L1)2Cl4], where L1 is the bidentate ligand 1,3-bis(imidazol-1-ylmethyl)-2,4,6- trimethylbenzene, has been achieved by gas phase diffusion. Single crystal X-ray diffraction, powder X-ray diffraction, UV-visible spectroscopy, EPR and SQUID magnetometry studies confirm inclusion of the radical into this seemingly non-porous material, and illustrate the presence of antiferromagnetic coupling between the paramagnetic host and guest species. The radical guest is readily released by heating or by the addition of solvent (CH2Cl2)

Intra-Genomic Ribosomal RNA Polymorphism and Morphological Variation in Elphidium macellum Suggests Inter-Specific Hybridization in Foraminifera

Elphidium macellum is a benthic foraminifer commonly found in the Patagonian fjords. To test whether its highly variable morphotypes are ecophenotypes or different genotypes, we analysed 70 sequences of the SSU rRNA gene from 25 specimens. Unexpectedly, we identified 11 distinct ribotypes, with up to 5 ribotypes co-occurring within the same specimen. The ribotypes differ by varying blocks of sequence located at the end of stem-loop motifs in the three expansion segments specific to foraminifera. These changes, distinct from typical SNPs and indels, directly affect the structure of the expansion segments. Their mosaic distribution suggests that ribotypes originated by recombination of two or more clusters of ribosomal genes. We propose that this expansion segment polymorphism (ESP) could originate from hybridization of morphologically different populations of Patagonian Elphidium. We speculate that the complex geological history of Patagonia enhanced divergence of coastal foraminiferal species and contributed to increasing genetic and morphological variation

Co-crystal formation with 1,2,3,5-dithiadiazolyl radicals

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Hydrate formation in pyridinium pamoate salts

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Lack of co-crystal formation with cyclotriphosphazenes : a cautionary tale

CITATION: Wahl, H., Haynes, D. A. & Le Roex, T. 2016. Lack of co-crystal formation with cyclotriphosphazenes : a cautionary tale. South African Journal of Chemistry, 69:35–43, doi:10.17159/0379-4350/2016/v69a5.The original publication is available at http://www.scielo.org.zaENGLISH ABSTRACT: The attempted formation of co-crystals with a series of cyclotriphosphazene derivatives has been investigated. Despite numerous attempts, only one co-crystal was obtained. The crystal structure of this material, [hexakis(4-pyridyloxy)-cyclotriphosphazene][ terephthalic acid]2.5, is presented here. The crystal structures of 2,2-bis(4-formylphenoxy)-4,4,6,6-bis[spiro(2’,2”-dioxy- 1’,1”-biphenylyl]cyclo-triphosphazene and hexakis(4-cyanophenoxy)cyclotriphosphazene are also reported for the first time. The extremely low rate of co-crystal occurrence in these materials cannot be explained, despite the consideration of several possibilities. This serves as a cautionary tale – co-crystal formation is not necessarily straightforward.http://www.scielo.org.za/scielo.php?script=sci_abstract&pid=S0379-43502016000100005&lng=en&nrm=iso&tlng=enPublisher's versio

A series of polymorphs of hexakis(4-fluorophenoxy)cyclotriphosphazene

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Crystallization of Organic Salts and Co-crystals by Sublimation: The Effect of Experimental Conditions

The selective growth of either organic salts or co-crystals from the gas phase has been achieved by varying specific conditions in a series of sublimation experiments. The effect of vacuum pressure, sublimation time, sublimation temperature and temperature gradient, physical separation of components, and mass scale on the sublimation of two acid/base systems, namely succinic acid/hexamethylenetetramine and oxalic acid/4,4′-bipyridine, was investigated. For both systems, salt formation was favored at lower pressures and higher temperatures, and correspondingly co-crystal was selectively formed at lower temperatures and higher pressures

Cyanocalix[4]arenes: synthesis, crystal structures and reactivity studies

<p>Herein, we describe an improved method to synthesise mono-, di- and tetra-cyanocalix[4]arene and report their crystal structure determinations. We also report our attempts to further functionalise the cyanocalix[4]arenes into dithiadiazolyl-calix[4]arenes, and propose a hypothesis as to why the cyano group on a calix[4]arene is an extremely challenging group to modify.</p

Guest Exchange in a Robust Hydrogen-Bonded Organic Framework: Single-Crystal to Single-Crystal Exchange and Kinetic Studies

The salt 3,4-lutidinium pamoate crystallizes as its hemihydrate, forming a hydrogen-bonded organic framework with tetrahydrofuran (THF) as a guest in channels in the structure (<b>1·THF</b>). Extensive investigation has shown this framework to be highly robust: the THF in the channels can be exchanged for 20 different compounds, with 13 of these exchanges occurring in a single-crystal to single-crystal manner. The THF can also be exchanged for the volatile solids pyrazine or iodine, both via single-crystal to single-crystal transformations. Stepwise exchange of solvents is also possible, with a sequence of five exchanges occurring before the crystals begin to deteriorate. Investigation of the kinetics of exchange in <b>1·THF</b> revealed that exchange occurs according to a deceleratory kinetic model for contracting volume