Effect of the substituents on the spin coupling between iminosemiquinone pi-radicals mediated by diamagnetic metal ions: l.s. Co(III) vs Ga(III)

Exchange coupling between the radical iminosemiquinone ligands changes from ferromagnetic to antiferromagnetic in l.s. Co(III) complexes, whereas the same coupling in Ga(III) complexes is always antiferromagnetic.     

Polymorphism in [Co(SCN)4(ppz-H)2] (ppz,piperazine)

A one-pot reaction of [Co(NO₃)₂ · 6H₂O and piperazine] with NH₄SCN/NaSCN in water–methanol (1:1) solvent leads to two polymorphs of [Co(SCN)₄(ppz-H)₂] (ppz, piperazine) (I and II). X-ray crystal structure reveals both have same space group but the differences in the alignment of pendant SCN⁻ leads to two polymorphs. In I, trifurcated N–H?S hydrogen bonding plays a prominent role in crystal packing leading to S?S interactions between SCN fragments but in II, no such trifurcation arises and thereby the crystal packing occurs through hydrogen bonding interactions only leading to a distinctly different network topology. TG/DSC and FT-IR study reveal they are enantiotropically related.     

An intramolecular passerini reaction: Synthesis of hydrastine.

An intramolecular Passerini reaction between 3,4-methylenedioxyphenethylisocyanide and opianic acid is applied in a total synthesis of hydrastine, a phthalideisoquinoline alkaloid.     

Mild Friedel–Crafts Reactions inside a Hexameric Resorcinarene Capsule: C−Cl Bond Activation through Hydrogen Bonding to Bridging Water Molecules

A novel catalytic feature of a hexameric resorcinarene capsule is highlighted. The self‐assembled cage was exploited to promote the Friedel–Crafts benzylation of several arenes and heteroarenes with benzyl chloride under mild conditions. Calculations showed that there are catalytically relevant hydrogen‐bonding interactions between the bridging water molecules of the capsule and benzyl chloride, which is fundamental for the activation of the C?Cl bond. The capsule controls the reaction outcome. Inside the inner cavity of the capsule, N‐methylpyrrole is preferentially benzylated in the unusual β‐position while mesitylene reacts faster than 1,3‐dimethoxybenzene despite the greater π‐nucleophilicity of the latter compound.     

Poly(3‐hexyl thiophene)‐b‐poly(N‐isopropyl acrylamide): Synthesis and its composition dependent structural,solubility, thermoresponsive,electrochemical, and electronic properties

Conjugated block copolymers consisting of poly(3‐hexyl thiophene) (P3HT) and a thermoresponsive polymer poly(N‐isopropyl acrylamide) (PNIPAM) with varying composition have been synthesized by facile click reaction between alkyne terminated P3HT and azide terminated PNIPAM. The composition‐dependent solubility, thermoresponsive property in water, phase behavior, electrochemical, optical, and electronic properties of the block copolymers were systematically investigated. The block copolymers with higher volume fraction of PNIPAM form thermoresponsive spherical micelles with P3HT‐rich crystalline cores and PNIPAM coronas. Both X‐ray and atomic force microscopic studies indicated that the blocks copolymers showed well‐defined microphase separated nanostructures and the structure depended on the composition of the blocks. The electrochemical study of the block copolymers clearly demonstrated that the extent of charge transport through the block copolymer thin film was similar to P3HT homopolymer without any significant change in the band gap. The block copolymers showed improved or similar charge carrier mobility compared with the pure P3HT depending on the composition of the block copolymer. These P3HT‐b‐PNIPAM copolymers were interesting for fabrication of optoelectronic devices capable of thermal and moisture sensing as well as for studying the thermoresponsive colloidal structures of semiconductor amphiphilic systems. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1785–1794     

Physical and electronic properties in multiwalled carbon nanotube–poly(3‐dodecylthiophene) nanocomposites

The properties of nanocomposites of dodecyl ester functionalized multiwalled carbon nanotube (FMWNT) and four poly(3‐dodecyl thiophene) (P3DDT) samples with different molecular weight and chain regioregularity are reported here. Uniform dispersion of FMWNT in the composites is evident from TEM study. π–π and CH–π interactions are evident from FTIR spectra in the low molecular weight (M_w = 8 × 10⁴) and high regiorandom (head‐tail = 69 mol %) P3DDT (ILM) composites; however, such interactions are not so prominent for other P3DDTs. Wide‐angle X‐ray scattering patterns indicate intact interchain lamellar structure of P3DDT in the composites. DSC study shows decrease of main chain melting peak of P3DDT (ILM) with increasing F‐MWNT content but the decrease is lower with higher molecular weight and higher regioregular samples. Dynamic mechanical analyzer study indicates that there is no significant change in the T_g, T_β, and T_γ transition temperature with FMWNT concentration indicating almost ideal mixing of the components. The percent increase of G′ increases with increasing FMWNT loading and also with temperature showing an 84% increase in storage modulus at –20 °C for ILM12 samples. The UV–vis spectrum indicates a decrease in band gap with FMWNT concentration for ILM composites, however, it is negligible with other P3DDTs. Photoluminescence quenching and multiple emission peaks occur in the composites. dc‐Conductivity of the composites increases by two orders and current‐voltage (I–V) curves show memory effect only in ILM‐MWNT composites. The I–V curves of other P3DDT nanocomposites exhibit rectification property. Quantitative explanation of electronic properties has been afforded from the band energy and work function values. So, the electronic properties of the nanocomposite can be tuned by changing the molecular weight, regioregularity, and concentration of FMWNT. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1412–1425, 2009     

Controlled Orientation in a Bio‐Inspired Assembly of Ag/AgCl/ZnO Nanostructures Enables Enhancement in Visible‐Light‐Induced Photocatalytic Performance

In a bio‐inspired approach, polyamine‐mediated mineralization of ZnO was explored to develop an environmentally benign methodology for synthesizing Ag/AgCl/ZnO nanostructures. The assembling properties displayed by the polyamines to create composite structures was utilized to have the nanocomponents effectively interact with each other in a way that is desirable for the application envisaged. The polyamines, which act as a mineralizing agent for ZnO nanoparticles, also facilitate the formation of Ag/AgCl within ZnO under ambient conditions. Thus synthesized Ag/AgCl/ZnO nanostructures represent a multi‐heterojunction system in which the nanocomponents lead in a synergistic way to enhancement in the photocatalytic activity under visible‐light irradiation.     

Composite materials for medical purposes based on polyvinylpyrrolidone modified with ketoprofen and silver nanoparticles

A method for obtaining composite medical materials based on polyvinylpyrrolidone (PVP K15) modified with ketoprofen in a medium of supercritical carbon dioxide and with Ag nanoparticles prepared by metal vapor synthesis is developed. A system in which ketoprofen and Ag nanoparticles with an average size of ∼16 nm are uniformly distributed over the bulk of PVP is obtained. It is found that the yield of ketoprofen from the composite in the physiological solution is higher than that for an analogous system obtained by mechanical mixing of the components.