Relative thermodynamic stabilities of 2-substituted 4-methylene-1,3-dioxolanes and 4-methyl-1,3-dioxoles

The relative thermodynamic stabilities of 24 pairs of carbon-carbon double-bondexo-endo isomeric 2-substituted 4-methylene-1,3-dioxolanes (a) and 4-methyl-1,3-dioxoles (b) have been determined by base-catalyzed chemical equilibration in DMSO solution. In all cases, theendo isomer (b) is the favored species at thermodynamic equilibrium. A single alkyl substitutent on C-2 gives only a negligible contribution to the relative stability of the isomeric forms, but the presence of two alkyl groups on C-2 increases the relative stability of theendo isomer by 2–3 kL mol^–1. A still higher effect in favor of theendo isomer is produced by introduction of a single alkoxy group on C-2; this effect is further slightly accentuated by 2,2-dialkoxy substitution at C-2. The origin of the favorable effect of 2-alkoxy substitution on the relative stability of theendo isomer is not clear, but it seems to arise from an unexpected stability of theendo isomer rather than from an enhanced destabilization of theexo form.     

Hydrogen-bonding effects in calix

The synthesis and spectroscopic characterization of self-assembling calix[4]arene based capsules 1a.1a and 1b.1b are described. These compounds feature four urea substituents at the upper rims and four secondary amide fragments at the lower rims that can participate in inter- and intramolecular hydrogen bonding in apolar solution. Communication between the calixarene rims in 1a, b influences the self-assembled cavity's size and shape. Specifically. dimerization results in a perfect cone conformation of the calixarene skeleton in 1a, b and stabilizes a seam of intramolecular amide C=O...H-N hydrogen bonds at the lower rim. This seam is cycloenantiomeric, with either clockwise or counterclockwise arrangements of the head-to-tail amides. Complexation of Na+-cation breaks hydrogen bonds at the lower rim but maintains the capsular assembly. Encapsulation properties of 1a.1a and 1b.1b were studied in nonpolar solvents and their binary mixtures as well as through heterodimerization experiments. The presence of amide groups at the lower rim causes notable differences in the capsule's binding affinities when compared to the corresponding tetraester capsules 1c.1c and 1d.1d. In the monomeric state calixarenes 1a, b are in a pinched cone conformation. The solid state X-ray crystallographic studies with monomeric 1a reveal only two intramolecular C=O...H-N hydrogen bonds between the adjacent amides at the lower rim, and an extensive network of intermolecular hydrogen bonds between urea groups at the upper rim.     

Synthesis, characterization and thermal properties of small R2R2NX-type quaternary ammonium halides

Twenty-one R₂R^′₂N⁺X⁻ -type (R=methyl or ethyl, R^′=alkyl, X=Br or I) quaternary ammonium (QA) halides have been prepared by using a novel one-pot synthetic route in which a formamide (dimethyl-, diethylformamide, etc.) is treated with alkyl halide in the presence of sodium or potassium carbonate. The formation of QA halides was verified with ¹H-NMR, ¹³C-NMR, MS and elemental analysis. The crystal structures of four QA halides (two bromide and two iodide) were determined using X-ray single crystal diffraction, and the powder diffraction method was used to study the structural similarities between the single crystal and microcrystalline bulk material. The thermal properties of all compounds were studied using TG/DTA and DSC methods. The smallest compounds decomposed during or before melting. The decreasing trend of melting points was observed when the alkyl chain length was increased. The liquid ranges of 120-180 °C were observed for compounds with 5-6 carbon atoms in the alkyl chain. The low melting points and wide liquid ranges suggest potential applicability of these compounds for example as ionic liquids precursors.     

Can a linear value function explain choices? An experimental study

We investigate in a simple bi-criteria experimental study, whether subjects are consistent with a linear value function while making binary choices. Many inconsistencies appeared in our experiment. However, the impact of inconsistencies on the linearity vs. non-linearity of the value function was minor. Moreover, a linear value function seems to predict choices for bi-criteria problems quite well. This ability to predict is independent of whether the value function is diagnosed linear or not. Inconsistencies in responses did not necessarily change the original diagnosis of the form of the value function. Our findings have implications for the design and development of decision support tools for Multiple Criteria Decision Making problems.     

Bifunctional coordination polymers as efficient catalysts for carbon dioxide conversion

The multidentate ligand H₂ L upon complexation with Zn (II) and Cd (II) provide a one‐dimensional polymeric networks. These coordination polymers (CPs) CP‐1 and CP‐2 containing Zn (II) and Cd (II) metals respectively are well characterized. The single crystal structural analysis confirms the formation of one‐dimensional coordination polymer with zigzag fashion in CP‐1 and ladder chain CP‐2 . Both the CPs are applied as catalysts to synthesize various cyclic carbonates from epoxides and carbon dioxide. The catalysts are giving better conversion under solvent‐free and additive‐free condition using 10 bar CO₂ and 100 °C as optimized pressure and temperature. The detailed kinetic experiments suggesting the first order kinetics, the energy of activation (Ea) is calculated for this catalytic conversion.     

Luminescent PtII and PtIV Platinacycles with Anticancer Activity Against Multiplatinum-Resistant Metastatic CRC and CRPC Cell Models

Platinum-based chemotherapy persists to be the only effective therapeutic option against a wide variety of tumours. Nevertheless, the acquisition of platinum resistance is utterly common, ultimately cornering conventional platinum drugs to only palliative in many patients. Thus, encountering alternatives that are both effective and non-cross-resistant is urgent. In this work, we report the synthesis, reduction studies, and luminescent properties of a series of cyclometallated (C,N,N′)Pt^IV compounds derived from amine–imine ligands, and their remarkable efficacy at the high nanomolar range and complete lack of cross-resistance, as an intrinsic property of the platinacycle, against multiplatinum-resistant colorectal cancer (CRC) and castration-resistant prostate cancer (CRPC) metastatic cell lines generated for this work. We have also determined that the compounds are effective and selective for a broader cancer panel, including breast and lung cancer. Additionally, selected compounds have been further evaluated, finding a shift in their antiproliferative mechanism towards more cytotoxic and less cytostatic than cisplatin against cancer cells, being also able to oxidize cysteine residues and inhibit topoisomerase II, thereby holding great promise as future improved alternatives to conventional platinum drugs.     

A Supramolecular Chiral Auxiliary Approach: “Remote Control” of Stereochemistry at a Hierarchically Assembled Dimeric Helicate

Dimeric hierarchically‐assembled titanium(IV) helicates are in solvent‐dependent equilibrium with the corresponding monomers. Statistically formed mixtures of such complexes bearing chiral stereocontrolling ligands and achiral diene‐substituted ligands show high diastereoselectivity and reasonable enantioselectivity in the Diels–Alder reaction with maleimides if the reaction proceeds with the dimer but not with the monomer. Thus, solvent dependent switching between the monomer and dimer enables on/off switching of the enantioselectivity.     

Optical sensing of parameters crucial for Japanese woodblock print making

Traditional Japanese woodblock printing is a centuries old art form. This time-honoured form of art is at risk of extinction as a consequence of the increasing lack of availability of wild cherry trees, which are a traditionally used woodblock material. Solutions for this material problem have been investigated for several years, but none of the tested materials has been sufficient when compared with the watercolour print quality imprinted by wild cherry woodblocks. To contribute to overcoming this material problem, we have investigated the physical properties of heat-treated woodblock materials made from different wood species. The International Commission on Illumination (CIE) tristimulus values, the CIELAB coordinates, the total reflectance, and the gloss, as well as, the water contact angle from the woodblock surface is observed to have a strong relation to the surface treatment of a woodblock. The surface treatment of a woodblock, in turn, relates to its water delivery, which is the basis for watercolour printing.