The Effect of Sterically Active Ligand Substituents on Gas Adsorption within a Family of 3D Zn-Based Coordination Polymers.

An investigation of the adsorption properties of two structurally related, 3D coordination polymers of composition Zn(2-Mehba) and Zn(2,6-Me2hba) (2-Mehba = the dianion of 2-methyl-4-hydroxybenzoic acid and 2,6-Me2hba = the dianion of 2,6-dimethyl-4-hydroxybenzoic acid) is presented. A common feature of these structures are parallel channels that are able to accommodate appropriately sized guest molecules. The structures differ with respect to the steric congestion within the channels arising from methyl groups appended to the bridging ligands of the network. The host network, Zn(2-Mehba), is able to take up appreciable quantities of H2 (77 K) and CO2 and CH4 (298 K) in a reversible manner. In regard to the adsorption of N2 by Zn(2-Mehba), there appears to be an unusual temperature dependence for the uptake of the gas such that when the temperature is increased from 77 to 298 K the uptake of N2 increases. The relatively narrow channels of Zn(2,6-Me2hba) are too small to allow the uptake of N2 and CH4, but H2 molecules can be adsorbed. A pronounced step at elevated pressures in CO2 and N2O isotherms for Zn(2,6-Me2hba) is noted. Calculations indicate that rotation of phenolate rings leads to a change in the available intraframework space during CO2 dosing.

English semantic word-pair norms and a searchable Web portal for experimental stimulus creation.

As researchers explore the complexity of memory and language hierarchies, the need to expand normed stimulus databases is growing. Therefore, we present 1,808 words, paired with their features and concept-concept information, that were collected using previously established norming methods (McRae, Cree, Seidenberg, & McNorgan Behavior Research Methods 37:547-559, 2005). This database supplements existing stimuli and complements the Semantic Priming Project (Hutchison, Balota, Cortese, Neely, Niemeyer, Bengson, & Cohen-Shikora 2010). The data set includes many types of words (including nouns, verbs, adjectives, etc.), expanding on previous collections of nouns and verbs (Vinson & Vigliocco Journal of Neurolinguistics 15:317-351, 2008). We describe the relation between our and other semantic norms, as well as giving a short review of word-pair norms. The stimuli are provided in conjunction with a searchable Web portal that allows researchers to create a set of experimental stimuli without prior programming knowledge. When researchers use this new database in tandem with previous norming efforts, precise stimuli sets can be created for future research endeavors.

Self-assembly of a Si-based cage by the formation of 24 equivalent covalent bonds.

A robust, nano-sized covalent cage, of composition, [(PhSi)6(ctc)4]6- (H6ctc = cyclotricatechylene) has been prepared in a simple reaction in good yield. The tetrahedral anionic cage is stable in both the solid and solution state and exhibits an affinity for Cs+ ions which bind to the internal surface of the cage.

A highly symmetric diamond-like assembly of cyclotricatechylene-based tetrahedral cages.

The combination of six Cu(II) centres with four cyclotricatechylene (ctc(6-)) ligands generates large (Cu(6)ctc(4))(12-) cages with the topology of the tetrahedron. The anionic tetrahedral cages are cemented together, triangular face to triangular face, by Na(+) cations together with water molecules to generate a highly symmetric diamond-like assembly (space group Fd-3m, the same as that of diamond itself) whose adamantane-like units have an iodide ion at the centre of every cyclohexane-like face.