Enhancement of ordinal CoMFA by ridge logistic partial least squares

Conventional comparative molecular field analysis (CoMFA) requires at least 3 orders of experimental data, such as IC 50 and K i, to obtain a good model, although practically there are many screening assays where biological activity is measured only by rating scale. To improve three-dimensional quantitative structure-activity relationship (3D-QSAR) analysis, we developed in this study a modified ordinal classification-oriented CoMFA using partial-least-squares generalized linear regression and ridge estimation. The modified Logistic CoMFA was validated using a corticosteroid binding globulin receptor binding data set, a benchmark for 3D-QSAR, and an acetylcholine esterase inhibitor data set. Our results show that modification of Logistic CoMFA enhanced both prediction accuracy and 3D graphical analysis. In addition, the 3D graphical analysis of the modified Logistic CoMFA was much improved. This improvement resulted in more accurate information on the binding mode between proteins and ligands than in the case of conventional CoMFA.     

Conformational change of poly(methylphenylsilane) induced by the photoisomerization of pendant azobenzene moiety in the film state

Conformational change of the main chain of poly(methylphenylsilane) functionalized with pendant azobenzene has been studied in the solution and in the film state. The conformation of the main chain was found to depend on the molar ratio of the Si units with and without the pendant azobenzene moiety. The inflection region for the conformational change was 0.3–0.5 of the molar ratio. The conformation of the main chain changed by the photoisomerization of the pendant azobenzene moiety in the film state. The efficiency of the conformational change of the main chain increased with the decrease of the molar ratio, accompanied by the highest final value of degree of the conformational change at the molar ratio of 0.5. The reverse conformational change was induced by heating.     

Reactivity of niobium-carbon cluster ions with hydrogen molecules in relation to formation mechanism of Met-Car cluster ions

It is known that a niobium-carbon Met-Car cluster ion (Nb 8C 12 (+)) and its intermediates (Nb 4C 4 (+), Nb 6C 7 (+), etc.) are selectively formed by the aggregation of the Nb atoms in the presence of hydrocarbons. To elucidate the formation mechanism, we prepared Nb n C m (+) with every combination of n and m in the gas phase by the laser vaporization technique. The reactivity of Nb n C m (+) with H 2 was examined under the multiple collision condition, finding that Nb n C m (+) between Nb 2C 3 (+) and Nb 8C 12 (+) are not reactive with H 2. On the basis of the H 2 affinity of Nb n C m (+) experimentally obtained, we propose a dehydrogenation-controlled formation mechanism of niobium-carbon Met-Car cluster ions.     

Dense coordination network capable of selective CO2 capture from C1 and C2 hydrocarbons

We elucidated the specific adsorption property of CO(2) for a densely interpenetrated coordination polymer which was a nonporous structure and observed gas separation properties of CO(2) over CH(4), C(2)H(4), and C(2)H(6), studied under both equilibrium and kinetic conditions of gases at ambient temperature and pressure.     

Discotic ionic liquid crystals of triphenylene as dispersants for orienting single-walled carbon nanotubes

Orient and conduct: Triphenylene-based discotic ionic liquid crystals (ILCs) with six imidazolium ion pendants can disperse pristine single-walled carbon nanotubes (SWNTs). When the ILC is columnarly assembled, doping with SWNTs results in macroscopic homeotropic columnar orientation. Combination of shear and annealing treatments gives rise to three different orientation states, which determine the anisotropy of electrical conduction.     

Design of Flexible Lewis Acidic Sites in Porous Coordination Polymers by using the Viologen Moiety

Charged up: A novel porous coordination polymer with a charged organic surface (COS) comprising a zwitterionic organic linker, viologen, has been synthesized. The COS shows strong Lewis acidity accompanied with flexibility, and the isosteric heat of H(2) adsorption is 9.5?kJ?mol(-1) , which is comparable to that of open metal sites (OMSs).     

Stereodefined construction of trisubstituted alkenes by direct coupling reaction of allylating agents, alkynes, and organoboranes

Tandem reaction: The Pd-catalyzed three-component coupling reaction of an allylic alcohol, terminal alkyne, and organoborane to give (E)-1-substituted 2-alkyl-1,4-pentadienes, involving geminal allylation and alkylation at the acetylenic terminal carbon, is described. Bis-diene undergoes a similar multicomponent coupling reaction with acetylene and organoborane, involving cyclization of bis-π-allylpalladium, to form trans-allyl pentadienyl cyclic and heterocyclic compounds with excellent regio- and stereoselectivities (see scheme).     

A Soft Copper(II) Porous Coordination Polymer with Unprecedented Aqua Bridge and Selective Adsorption Properties

Herein, the synthesis, crystal structure, and full characterization of a new soft porous coordination polymer (PCP) of ([Cu₂(dmcapz)₂(OH₂)]DMF_1.5)_n ( 1 ) formulation, which is easily obtained in the reaction of CuX₂ (X=Cl, NO₃) salts with 3,5‐dimethyl‐4‐carboxypyrazole (H₂dmcapz) is present. Compound 1 shows a copper(II) dinuclear secondary building unit (SBU), which is supported by two pyrazolate bridges and an unprecedented H₂O bridge. The dinuclear SBUs are further bridged by the carboxylate ligands to build a diamondoid porous network. The structural transformations taking place in 1 framework upon guest removal/uptake has been studied in detail. Indeed, the removal of the bridging water molecules gives rise to a metastable evacuated phase ( 1 b ) that transforms into an extremely stable porous material ( 1 c ) after freezing at liquid‐nitrogen temperature. The soaking of 1 c into water allows the complete and instantaneous recover of the water‐exchanged material ( 1 a′ ). Remarkably, 1 b and 1 c materials possess structural bistability, which results in the switchable adsorptive functions. Therefore, the gas‐adsorption properties of both materials have been studied by means of single‐component gas adsorption isotherms as well as by variable‐temperature pulse‐gas chromatography. Both materials present permanent porosity and selective gas‐adsorption properties towards a variety of gases and vapors of environmental and industrial interest. Moreover, the flexible nature of the coordination network and the presence of highly active convergent open metal sites confer on these materials intriguing gas‐adsorption properties with guest‐triggered framework‐breathing phenomena being observed. The plasticity of Cu^II metal center and its ability to form stable complexes with different coordination numbers is at the origin of the structural transformations and the selective‐adsorption properties of the studied materials.