Computational Study of Cage Like (ZnO)12 Cluster Using Hybrid and Hybrid Meta Functionals

Density Functional Theory employing hybrid and M06 functionals in combination with three different basis sets is used to calculate the ground state of a cage like (ZnO)₁₂ nanocluster which has been consistently reported as the more stable cluster for its particular size. B3LYP and B3PW91 hybrid functionals combined with 6‐31+G*, Lanl2dz and SDD basis sets are employed to treat the ZnO molecular system. Alternatively, three M06 functionals in combination with three basis sets are employed in the nanostructure calculations. Results obtained by treating ZnO sodalite cage nanocluster with M06 functionals demonstrated comparable quality to results obtained with hybrid functionals. Within this study, efficient theoretical DFT methods with the widely known hybrid and the recently created M06 meta‐hybrid functionals are employed to study nanostructured ZnO. Our resulting parameters provide a fresh approach performance wise on the different theoretical methods to treat transition metal nanostructures, particularly, ZnO nanoclusters geometry and electronic structure.     

Simple Reduction of Heteroaromatic Esters to Alcohols Using a Sodium Borohydride–Methanol System

Some heteroaromatic esters were reduced to the corresponding alcohols by using a sodium borohydride–methanol system. The reduction was completed within 0.15–2.0 h in refluxing THF. The alcohol products were isolated after aqueous workup in moderate to excellent yield (48–97%).     

Selective Sulfenylative Desulfonylation or Decarbalkoxylation of α-Sulfonyl Malonates with DABCO or Bu3N: Reactivity and Conformational Analysis

The study on reactivity of several α-substituted α-sulfonyl malonates toward 1,4-diazabicyclo[2.2.2]octane (DABCO) and Bu₃N is described. The reactivity with DABCO revealed the possible competition between decarbalkoxylation and unexpected desulfonylation, depending on the α-substituent, because of sterical hindrance around the electrophilic centers (SO₂ and CO₂R). The derivatives with crowded α-substituents suffer selective desulfonylation, and a novel and efficient desulfonylation method can be proposed. The dependence of the reactivity of α-sulfonyl malonates on the sterical hindrance around the electrophilic centers is confirmed by conformational analysis (Macromodel/MM2? and Mopac/MP3). The carbanionic mechanism is proved because the corresponding protonated, deuterated, and sulfenylated products were obtained by addition of the corresponding electrophilic agents. Bu₃N showed itself to be a novel selective decarbalkoxylation agent for any α-substituted α-sulfonyl malonate.     

A Convenient Method for the Preparation of 6,7-Methyl-Enedioxy-3-Alkyl-2-Hydroxy-1,4-Naphthoquinones from Natural Safrole and Carboxylic Acids

As part of our program to prepare substituted rtaphthoquinones with potential biological activity¹ we have synthetized 6, 7-methyleriedioxy-3-alky 1 lawsones (5a-g) from natural safrole (1) and carboxylic' acids (～50% overall yield).     

One-Step Protection-Free Synthesis of 3-Aryl-5-hydroxyalkyl-1,2,4-oxadiazoles as Building Blocks

A simple and straightforward synthesis of 3-aryl-5-hydroxyalkyl-1,2,4-oxadiazoles is described. The reaction among arylamidoximes, ethyl glycolate or ethyl lactate, and potassium carbonate in refluxing toluene afforded the desired 1,2,4-oxadiazoles in moderate to good yields. The synthesis has been accomplished in a single step, avoiding protection–deprotection protocols.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

Cleansing contaminated seawaters using marine cyanobacteria: evaluation of trace metal removal from the medium

The use of microbial biomass in biosorption is already being studied as a potential alternative to (or combined with) conventional processes, where several algae and microorganisms have already shown promising ability to uptake metals. Cyanobacteria (blue-green algae) are widespread organisms, with specific properties, such as high nutrient removal capacity and tolerance to highly variable conditions which make them well-suited for wastewater and remediation purposes. The main aim of this work was to evaluate the use of a marine cyanobacterium LEANCYA 21 (Synechocystis sp.), collected from the Portuguese southern border, for the removal of selected trace metals when in natural seawater culture medium. It was observed, for the first time, that this particular strain is capable of uptaking Pb, Ni and Zn (at nM levels) from seawater solutions using small amounts of biomass. Uptake values for Pb were up to 90% (0.75 mg g^?1 biomass) in 6 h. The specific biosorption curves of Ni and Zn showed that these metals follow a first order kinetics biosorption in batch conditions. Solutions containing multimetals have revealed that Ni uptake is affected by the presence of Pb and Zn. The calculated specific absorption values were high enough to predict a possible application in aquaculture where such low levels of metals may inhibit microalgae growth.     

1,1′,1′′-(2,4,6-Trihydroxybenzene-1,3,5-triyl)triethanone tautomerism revisited

It has recently been suggested that 1,1′,1′′-(2,4,6-trihydroxybenzene-1,3,5-triyl)triethanone may be tautomeric. Using ¹³C NMR chemical shifts and deuterium isotope effects on ¹³C chemical shifts, it is demonstrated that this is not the case. This compound occurs as a strongly hydrogen bonded benzene structure with hydrogen bonds between OH groups and the acetyl groups in both non-polar and hydrogen donating solvents. Quantum-chemical calculations using MP2 and M06-2X methods show substantial preference for the phenol structure in both the gas phase, and in cyclohexane and methanol. In addition, conventional UV–vis spectroscopy data suggest not tautomeric, but aggregation behaviour of the molecule in methanol and acetonitrile.     

Ionic liquid 1-ethyl-3-methylimidazolium acetate: an attractive solvent for native chemical ligation of peptides

The ionic liquid 1-ethyl-3-methylimidazolium acetate ([C₂mim][OAc]) was successfully used as alternative solvent for native chemical ligation of peptide fragments to produce model peptide LYRAXCRANK (X = G, A, L, N, Q, K, and F). The commonly used buffer system including thiol additives such as thiophenol and benzyl mercaptan can be replaced by the nontoxic ionic liquid [C₂mim][OAc]. In addition to improving the solubility of the peptides in [C₂mim][OAc], yields and rates of the ligation reactions were found to be efficiently enhanced.     

Electrochemical derivatization‐capillary electrophoresis‐contactless conductivity detection: A versatile strategy for simultaneous determination of cationic,anionic, and neutral analytes

The simultaneous determination of cationic, anionic, and neutral analytes in a real sample was demonstrated by coupling electrochemical (EC) derivatization with counter‐EOF CE‐C⁴D. An EC flow cell was used to oxidize alcohols from an antiseptic mouthwash sample into carboxylic acids at a platinum electrode in acid medium. The carboxylates formed in the derivatization process and other sample ingredients, such as benzoate, saccharinate, and sodium ions, were separated in counter‐flow mode and detected in one run in Tris‐HCl buffer, pH 8.6. Fewer than 5 min were needed to complete each analysis with the automated flow system comprising solenoid pumps for the management of solutions. Insights into the electrochemistry of benzoic acid, present in the sample matrix, were also gained by EC‐CE‐C⁴D; more specifically, by applying potentials higher than 1.47 V to the platinum electrode, some formiate and minute amounts of salicylate were detected.