Synthesis,photophysical and electrochemical properties of bay-axial perylene diimide–subphthalocyanine dyads

Two novel perylene diimide–subphthalocyanine dyads in which the two macrocycles are linked together by a B–O bond have been synthesized. The electronic communication between the two chromophores was investigated by photophysical and electrochemical studies.     

Stochastic makespan minimization in structured set systems

Mathematical Programming - We study stochastic combinatorial optimization problems where the objective is to minimize the expected maximum load (a.k.a. the makespan). In this framework, we have a...     

Per-6-amino-beta-cyclodextrin as an efficient supramolecular ligand and host for Cu(I)-catalyzed N-arylation of imidazole with aryl bromides

Per-6-amino-beta-cyclodextrin (per-6-ABCD), acting simultaneously as a supramolecular ligand for CuI and host for aryl bromides, catalyzes N-arylation of imidazole with aryl bromides under mild conditions. This simple method proceeds with excellent yield for the coupling of imidazole with various substituted aryl bromides demonstrating good tolerance of other functionalities.     

Synthesis, structure and physical properties of the manganese(ii) selenide/selenolate cluster complexes [Mn(32)Se(14)(SePh)(36)(PnPr(3))(4)] and [Na(benzene-15-crown-5)(C(4)H(8)O)(2)](2)[Mn(8)Se(SePh)(16)

The synthesis, molecular structures, and magnetic and optical properties of [Mn(32)Se(14)(SePh)(36)(PnPr(3))(4)] and [Na(benzene-15-crown-5)(C(4)H(8)O)(2)](2)[Mn(8)Se(SePh)(16)] have been investigated which are the first examples of manganese chalcogenide cluster complexes, despite known manganese oxo compounds, which comprise more than four manganese atoms.     

Synthesis and characterization of nano silver ferrite composite

We report the synthesis of nano sized silver ferrite composite having the empirical formula AgFeO₂ by a co-precipitation method. The resulting powders are thin platelets, transparent and a rich ruby red in color in transmission. The X-ray diffraction (XRD) powder data consisted of only nine reflections, and the analysis showed the unit cell to be rhombohedral. The powders showed extensive XRD line broadening and the sizes of the crystals are calculated to be in the range 4-36.5 nm. The morphology of the silver ferrite composite studied using scanning electron microscope showed nano sized particles. The particle size is found to increase with increase in annealing temperature. The magnetic behavior, measured using a vibrating sample magnetometer, indicated a change from paramagnetic to ferromagnetic with increase in particle size.     

An Expeditious Synthesis of Flavonols Promoted by Montmorillonite KSF Clay and Assisted by Microwave Irradiation under Solvent‐Free Conditions

A simple, efficient, rapid, and ecofriendly synthesis of flavonols in >90% yield from 2′‐(mesyloxy)epoxychalcones (=2‐(3‐aryl‐2,3‐epoxypropanoyl)phenyl methanesulfonates) promoted by montmorillonite KSF clay and assisted by microwave irradiation has been described.     

Amino acid intercalated layered double hydroxide catalyzed chemoselective methylation of phenols and thiophenols with dimethyl carbonate

Sixteen different amino acids are intercalated into Mg–Al layered double hydroxides (LDHs) by the reconstruction method and are characterized by powder XRD and FT-IR. The intercalated amino acid–LDHs (AA-LDHs) are used as catalysts for chemoselective O-methylation of phenol and S-methylation of thiophenol with dimethyl carbonate (DMC) as a green methylating agent. The intercalation behavior of various amino acids is influenced by various structural features of amino acids, namely, carbon chain length, structure, and physicochemical properties. In particular, amino acids possessing a hydrophobic side-chain show higher catalytic activity. A suitable reaction mechanism is proposed. The catalyst can also be recycled.     

Studies on electron transfer reactions: reduction of heteropoly 11-tungstophosphovanadate(V) by <Emphasis Type="SmallCaps">l</Emphasis>-cysteine and thioglycolic acid in aqueous acid medium

The rates of the electron transfer reaction of l-cysteine and thioglycolic acid with the polyoxometalate, [PV^VW₁₁O₄₀]⁴⁻, have been measured spectrophotometrically in aqueous acid medium. The polyoxometalate oxidizes cysteine to cystine and thioglycolic acid to dithioglycolic acid and gets reduced to heteropoly blue, [PV^IVW₁₁O₄₀]⁵⁻. The order of the reaction with respect to oxidant is one, whereas the reaction shows second order dependence on the substrates. The rate–pH profile shows that both the unionized and ionized thiol groups of the substrates are active species involved in electron transfer. A suitable mechanism has been proposed for the title reaction based on the results of kinetic studies.     

MAP/(PH/PH)/c Queue with Self-Generation of Priorities and Non-Preemptive Service

Abstract

Customers arriving according to a Markovian arrival process are served at a c server facility. Waiting customers generate into priority while waiting in the system (self-generation of priorities), at a constant rate γ; such a customer is immediately taken for service, if at least one of the servers is free. Else it waits at a waiting space of capacity c exclusively for priority generated customers, provided there is vacancy. A customer in service is not preempted to accommodate a priority generated customer. The service times of ordinary and priority generated customers follow distinct PH-distributions. It is proved that the system is always stable. We provide a numerical procedure to compute the optimal number of servers to be employed to minimize the loss to the system. Several performance measures are evaluated.