Photoinduced electron-transfer reactions of platinum(II) terpyridyl acetylide complexes: reductive quenching in a hydrogen-generating system

The one-electron reduction of [(mpt)Pt(CCPhCl)] ClO4 [mpt = 4'-(4-methylphenyl)-2,2',6',2' '-terpyridyl; CCPhCl = chlorophenyl acetylide] by a series of amine donors was investigated in a CH3CN solution. The excited state has a lifetime of 550 ns in the absence of quencher in degassed CH3CN. Quenching rate constants were >10(8) M(-1) s(-1) even for trialkylamines. Transient absorption spectroscopy provided convincing evidence for the production of the one-electron-reduced Pt complex, even with quenchers that could potentially serve as H-atom donors. The transient spectrum obtained in the presence of triethylamine exhibits, in addition to bleaching of the Pt(II) complex absorption, a maximum at approximately 360 nm and broad absorption from 500 to 800 nm, indicating that the reduced complex has a complex electronic structure and is not easily assigned as a terpyridyl anion radical.     

Spectroscopical splitting of Cu ion energy levels in magnesium lead fluoro silicate glasses

Homogeneous 40.0 MgO-(10-x) PbF₂-50.0 SiO₂: x CuO glasses were prepared using melt-quenching technique under controlled conditions. Spectroscopic studies (UV-vis absorption, ESR, FT-IR) are carried out for these glasses. One broad characteristic visible absorption band is observed around 700-850 nm in these glasses, the optical band gap decreases as the content of the CuO increases in the glass network up to 0.7 mol % then reversal trend is observed. ESR spectra of all these glasses show resonance peaks characteristic of Cu²⁺ ions and hyperfine splitting is resolved with increasing the CuO content in the glass network. From the observed ESR spectra, the spin-Hamiltonian parameters have been evaluated and indicate that Cu²⁺ ions have octahedral coordination with a strong tetragonal distortion in these glasses. By correlating ESR and optical absorption data, the molecular orbital coefficients have been evaluated. FT-IR spectra give important information about the nature of bonds in the glass matrix. The density of the glasses is also measured and is found to decrease with the increase CuO contents in the glass matrix. The physical parameters along with spectroscopic parameters are measured.     

Plasma-Electrospinning Hybrid Process and Plasma Pretreatment to Improve Adhesive Properties of Nanofibers on Fabric Surface

Electrospun nanofiber mats are inherently weak, and hence they are often deposited on mechanically-strong substrates such as porous woven fabrics that can provide good structural support without altering the nanofiber characteristics. One major challenge of this approach is to ensure good adhesion of nanofiber mats onto the substrates and to achieve satisfactory durability of nanofiber mats against flexion and abrasion during practical use. In this work, Nylon 6 nanofibers were deposited on plasma-pretreated woven fabric substrates through a new plasma-electrospinning hybrid process with the objective of improving adhesion between nanofibers and fabric substrates. The as-prepared Nylon 6 nanofiber-deposited woven fabrics were evaluated for adhesion strength and durability of nanofiber mats by carrying out peel strength and flex resistance tests. The test results showed significant improvement in the adhesion of nanofiber mats on woven fabric substrates. The nanofiber-deposited woven fabrics also exhibited good resistance to damage under repetitive flexion. X-Ray photoelectron spectroscopy and water contact angle analyses were conducted to study the plasma effect on the nanofibers and substrate fabric, and the results suggested that both the plasma pretreatment and plasma-electrospinning hybrid process introduced radicals, increased oxygen contents, and led to the formation of active chemical sites on the nanofiber and substrate surfaces. These active sites helped in creating crosslinking bonds between substrate fabric and electrospun nanofibers, which in turn increased the adhesion properties. The work demonstrates that the plasma-electrospinning hybrid process of nanofiber mats is a promising method to prepare durable functional materials.     

Helical folding in heterogeneous foldamers without inter-residual backbone hydrogen-bonding

This communication describes a set of hybrid foldamers that do not feature inter-residual, but intra-residual backbone hydrogen-bonding, yet adopt a preferentially folded conformation displaying right-handed helical architecture. Conformational ordering is apparently due to the combined conformational restrictions imposed by the conformationally restricted individual amino acid residues with which the oligomers are made of.     

Pharmacoinformatics-based identification of transmembrane protease serine-2 inhibitors from Morus Alba as SARS-CoV-2 cell entry inhibitors

Molecular Diversity - Transmembrane protease serine-2 (TMPRSS2) is a cell-surface protein expressed by epithelial cells of specific tissues including those in the aerodigestive tract. It helps the...     

CFD modeling of pressure drop and drag coefficient in fixed beds: Wall effects

Simulations of fixed beds having column to particle diameter ratio (D/dp ) of 3, 5 and 10 were performed in the creeping, transition and turbulent flow regimes, where Reynolds number (dp VLL/L ) was varied from 0.1 to 10,000. The deviations from Ergun’s equation due to the wall effects, which are important in D/d p<15 beds were well explained by the CFD simulations. Thus, an increase in the pressure drop was observed due to the wall friction in the creeping flow, whereas, in turbulent regime a decrease in t...     

A new synthetic route for 1,2-diketo compounds using unexpected C-C bond cleavage by PCC

An efficient method has been established for the preparation of 1,2-diketones by unexpected C-C bond cleavage in 4-keto-2-hydroxy esters using pyridiniumchlorochromate (PCC).     

A new benzimidazolium incorporated chemodosimeter affording dual chromogenic and fluorescence switch-on signaling for the selective targeting of cyanide

We have designed and synthesized a new chemodosimeter, Benzolin-A, which selectively responds to toxic cyanide by dual colorimetric and fluorescence turn-on responses in buffered aqueous DMSO. In the presence of cyanide, we observe absorbance red shift of 108 nm (color changing from colorless to yellow) and fivefold fluorescence enhancement. The ¹H NMR studies confirm the nucleophilic addition mechanism, and consistent with the experimental findings, the computational work predicts the feasibility of photoelectron transfer or energy transfer process in the native probe, as well as enhanced internal charge transfer in the Benzolin-A-cyanide adduct. Noteworthily, several background anions, such as F^?, Cl^?, AcO^?, SCN^?, HSO₄ ^?, NO₃ ^?, Br^?, I^? and H₂PO₄ ^? exhibit none or insignificant optical perturbations.     

Photocyclisations of some 3‐alkoxy‐2‐thienylchromones

Photoreorganisations of some 3‐allyloxy‐2‐thienylchromones have been described. The photoreactions are initiated through the intramolecular H‐abstraction to provide angular tetracyclic compounds. These chromones yield good chemical efficiency due to the involvement of highly stabilized allylic 1,4‐biradicals.