Metal-assisted red light-induced efficient DNA cleavage by dipyridoquinoxaline-copper(II) complex

Complete cleavage of double stranded pUC19 DNA by the complex [Cu(dpq)2(H2O)](ClO4)2 (dpq, dipyridoquinoxaline) has been observed on irradiation at 694 nm from a pulsed ruby laser, assisted by the metal d-band transition as well as the quinoxaline triplet states in the absence of any external additives.     

Visible-light-induced cyanation of aza-Baylis–Hillman adducts: a Michael type addition

Visible-light-induced aerobic oxidative cyanation of aza-Baylis–Hillman (aza-BH) adducts providing valuable allylic cyanides in good to excellent yields has been developed. The protocol involves in situ formation of 4π conjugated iminium ion intermediates, which undergo cyanation at the γ-position to afford Michael type adducts. This is the first example of visible-light-induced catalytic functionalization of aza-BH adducts using air (O₂) as an economical and ecosustainable oxidant and TMSCN as a convenient and readily available cyanide source.     

Iodide catalyzed synthesis of 2-aminobenzoxazoles via oxidative cyclodesulfurization of phenolic thioureas with hydrogen peroxide

A convenient and efficient oxidative cyclodesulfurization of o-phenolic thioureas to 2-aminobenzoxazoles employing TBAI (tetrabutylammonium iodide)/H₂O₂ catalyst/reagent system is reported. The protocol utilizes and offers a number of desired features such as metal-free, base-free, simple operation, room temperature, low cost catalyst/reagent, no need for anhydrous and inert conditions. The approach is also applicable to a one-pot synthesis of 2-aminobenzoxazoles in an excellent yield starting directly from o-aminophenols and aryl isothiocyanates.     

Influence of low concentration silver nanoparticles on the electrical and electro-optical parameters of nematic liquid crystals

Thermodynamical, optical, dielectric and electro-optical characterisation of nematic liquid crystals (LCs) and silver nanoparticle (NP) composites have been carried out. Transition temperatures of pure and composites systems have been measured. Thermodynamical studies suggest increase of clearing temperature of the composite material as compared to the pure material. Threshold voltage for switching from bright to dark state and splay elastic constant of the pure and composite materials have been determined. From frequency dependence of dielectric measurements, permittivity, loss, relaxation frequency and dielectric strength of flip-flop mechanism of LC molecules in the nematic phase have been calculated. Dielectric properties of composites have been explained in reference of Maier and Meier theory. The effects of doping of NPs on dielectric and electro-optic properties of LC-NP composites have been discussed.     

Mechanistic Studies on the Oxidation of Hydrazine by Tris(biguanide)manganese(IV) in Aqueous Acidic Media

The title Mn^IV complex, [Mn(LH₂)₃]⁴⁺ (LH₂ = biguanide = H₂NC(NH)NHC(NH)NH₂), an authentic two‐electron oxidant, quantitatively oxidizes hydrazine (H₂NNH₂) to dinitrogen in the pH interval 2.00–3.50. The net four‐electron oxidation of hydrazine is provided by two Mn^IV as established by stoichiometric studies. The overall reaction is composed of two parallel paths:     

Studien über Adsorption. VIII

Ohne Zusammenfassung Deutsch von Luise Pieper (Sobernheim, Rhl.)