Ion association in solutions of dimethylthallium(III) hydroxide

From studies of the specific hydroxide ion catalyzed decomposition of diacetone alcohol by dimethylthallium(III) hydroxide at 25°C, it is concluded that both ion pairs (dissociation constantK=0.090 mole-dm^–3) and dimers (dimerization constantK _d=1.5 dm³-mole^–1) exist in aqueous solution.Request for reprints should be addressed to: Dr. A. D. Pethybridge, Department of Chemistry, The University, Whiteknights Park, Reading, Berkshire, England.Deceased October 16, 1972.     

Metathesis cyclopolymerization of substituted 1,6‐heptadiyne and dual conductivity of doped polyacetylene bearing branched triazole pendants

The branched triazole group is synthesized by click chemistry via a controlled approach of slow addition of AB₂ compound to a B₂ core, and used as the substituent for 1,6‐heptadiyne monomer. Metathesis cyclopolymerization of monomer is performed well in dichloromethane without the weakly coordinating additive, indicating that the branched triazole itself can stabilize the living propagating chain, to generate branched triazole pendant‐contained polyacetylene with trans‐double bonds and five‐membered ring repeating units along the conjugated backbone. The LiTFSI doped polyacetylenes display ionic conductivities of 2.5–1.8 × 10^?6 S cm^?1; by further doping with iodine, polyacetylenes show the improved ionic and electronic conductivities of 1.3 × 10^?5 and 2.1 × 10^?7 S cm^?1 at 30 °C, respectively. Therefore, these doped polyacetylenes may act as the new electrolyte materials. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 485–494     

Toward a Better Determination of Infrared Molar Absorptivities and Dimer Formation Constants in Self‐association Through Hydrogen Bonding: 3‐Ethyl‐2‐methyl‐3‐pentanol in Tetrachloroethylene as an Example

The monomer–dimer self‐association of the dilute 3‐ethyl‐2‐methyl‐3‐pentanol in tetrachloroethylene in the very dilute state was studied by infrared spectroscopy at several temperatures. The solute was deliberately chosen so that higher oligomers were suppressed by the steric hindrance arising from bulky groups on both sides of hydroxyl group. Two linear utility equations were derived to treat, respectively, the integrated absorbance of the monomer band, A _m, and of the dimer band, A _d, as functions of the initially prepared solute concentration, [B ]₀. The respective molar absorptivities were obtained by fitting these equations to the data. Unlike previous methods, the dimerization constant (K ) can be obtained from either A _m or A _d. Any discrepancy between these two values of K serves as a measure of the quality of the data. The values of K at different temperatures were employed to calculate the standard enthalpy and entropy of dimerization by using a van't Hoff plot. The dimer is predominantly in the cyclic form where both hydroxyl protons are hydrogen‐bonded. This is inferred from the following observations: (1) the spectrum displays only two bands between 3300 and 3750 cm⁻¹; (2) the constancy of as a function of [B ]₀ ; and (3) the linearity of both plots [B ]₀/A _m vs. A _m , and [B ]₀/A _d vs. .     

Coordination‐Driven Dimerization of Zinc Chlorophyll Derivatives Possessing a Dialkylamino Group

Zinc chlorophyll derivatives Zn‐1 – 3 possessing a tertiary amino group at the C3¹ position have been synthesized through reductive amination of methyl pyropheophorbide‐d obtained from naturally occurring chlorophyll‐a . In a dilute CH₂Cl₂ solution as well as in a dilute 10 %(v/v) CH₂Cl₂/hexane solution, Zn‐1 possessing a dimethylamino group at the C3¹ position showed red‐shifted UV/Vis absorption and intensified exciton‐coupling circular dichroism (CD) spectra at room temperature owing to its dimer formation via coordination to the central zinc by the 3¹‐N atom of the dimethylamino group. However, Zn‐2/3 bearing 3¹‐ethylmethylamino/diethylamino groups did not. The difference was dependent on the steric factor of the substituents in the tertiary amino group, where an increase of the carbon numbers on the N atom reduced the intermolecular N⋅⋅⋅Zn coordination. UV/Vis, CD, and ¹H NMR spectroscopic analyses including DOSY measurements revealed that Zn‐1 formed closed‐type dimers via an opened dimer by single‐to‐double axial coordination with an increase in concentration and a temperature decrease in CH₂Cl₂, while Zn‐2/3 gave open and flexible dimers in a concentrated CH₂Cl₂ solution at low temperature. The supramolecular closed dimer structures of Zn‐1 were estimated by molecular modelling calculations, which showed these structures were promising models for the chlorophyll dimer in a photosynthetic reaction center.     

Programming Rapid Functional Group Diversification into a Solid-State Reaction: Aryl Nitriles for Self-Assembly,Click Reactivity,and Discovery of Coexisting Supramolecular Synthons

A method to rapidly diversify the molecules formed in organic crystals is introduced, with aryl nitriles playing a novel dual role as both hydrogen-bond acceptors and modifiable organic groups. The discovery of coexisting supramolecular synthons in the same crystal is also described. The general concept is demonstrated by using a bis(aryl nitrile) alkene that undergoes a hydrogen-bond-directed intermolecular [2+2] photodimerization to form a tetra(aryl nitrile)cyclobutane. The product is readily converted by click reactivity to a tetra(aryl tetrazole) and by hydrolysis to a tetra(aryl carboxylic acid). The integration of aryl nitriles into solid-state reactions opens broad avenues to post-modify products formed in crystalline solids for rapid diversification.