Synthesis, functionalization and coordination chemistry of dibenzotetraaza[14]annulenes

This comprehensive review summarizes recent advances in the synthesis and coordination chemistry of dibenzotetraaza[14]annulenes (DBTAAs) reported between 2010 and 2021. Owing to the smaller N4 donor cavity compared to that of the porphyrin core, it is not surprising that DBTAA offers versatile and unique coordination modes towards metal ions. The structural modification of the DBTAA core allows for the fine-tuning of their spectroscopic properties. DBTAA and derivatives have been utilized across a wide range of research disciplines such as in electronic devices and biological assays. The feasible preparation of ligands and their metal complexes suggests DBTAAs as potential alternatives to porphyrins

Enzymatic hydrolysis for the removal of 3- monochloropropanediol esters in edible oils using Candida rugosa lipase in the presence of deep eutectic solvents and nanocellulose

3-monochloropropanediol ester (3-MCPDE) is identified as a food-borne contaminant in edible oils and are classified as a possible carcinogen. This study reports an efficient enzymatic technique for the removal of 3-MCPDE from extra virgin olive oil (EVO) using Candida rugosa lipase (CRL) as the biocatalyst in the presence of choline chloride and fructose-based natural deep eutectic solvent (NADES) and nanocellulose (NC) extracted from almond shells. The validity of the method was confirmed by gas chromatography mass spectrometry (GC-MS) showing adequate precision with relative standard deviation values ≤ 2.37%. The quantification and detection limit are within the permissible levels of 3-MCPD in edible oils. Under optimized conditions of 30 min at 90 °C with 60 µL of phenylboronic acid (PBA), the enzymatic hydrolysis resulted in the removal of 79.8% of spiked 3-MCPD in EVO. No adverse effects of the EVO were detected from this technique with respect to the oil quality testing. The application of DESs and NCs as the support material for the CRL biocatalyst for the removal of 3-MCPDE has yet to be explored. This could have a significant impact on the edible oil industry for producing oils of higher quality free from 3-MCPDE

A grand avenue to integrate deep eutectic solvents into biomass processing

Deep eutectic solvents (DESs) are green solvents that are developing rapidly, used in many types of applications as well as fundamental investigations. The physicochemical properties of DESs are one of the most important factors which led to their increased interest in science and technology. DESs are thermally and chemically stable, non-flammable and have a negligible vapor pressure. Furthermore, most of the newly formulated DESs are liquids at room temperature. DESs are more economical and less expensive compared to ionic liquids. DESs are frequently prepared from renewable and non-toxic precursors, in addition, there are wide selections of biocompatible and biodegradable DESs. Hence, DESs have been used in many applications and processes such as biorefinery, lignocellulose dissolution, bioactive compound extraction and electrochemical applications. In this review, an update of the application of DESs in biomass processing as renewable sources is presented. This review aims to cover as much as possible the ongoing research and applications of DES and invite opinions to broaden the applications of DESs, rather than concentrating on the physicochemical fundamentals of new DESs. The future of these solvents is bright but require further investigations and efforts for a better understanding and future for sustainable resources

Preparation, scratch adhesion and anti-corrosion performance of TiO2-MgO-BHA coating on Ti6Al4V implant by plasma electrolytic oxidation technique

Bovine hydroxyapatite (BHA) (from cortical bone), was selected as the main electrolyte for plasma electrolytic oxidation (PEO) on Ti6Al4V implant. The prepared PEO coatings were examined by X-ray diffraction, field emission scanning electron microscope and energy-dispersive X-ray spectroscopy. The surface roughness, adhesion strength, wettability, surface energy and corrosion behaviour of the film were also investigated. The results show that the oxide layer (26 μm) formation on the Ti6Al4V was rough and porous. The micro-pores were filled with anatase TiO2, cubic MgO and hexagonal BHA particles. The porous structures and the compound particles were mainly composed of Mg, O, Ca, P, Ti, Na and Al. Unlike previous coatings produced from calcium and phosphorus inorganic solutions, the coating formation from a newly developed bovine bone-derived HA electrolyte revealed an additional MgO phase in the coating layer. Moreover, higher amount of single phase hexagonal crystalline BHA phase with a Ca/P ratio of 1.1 was achieved with a single PEO process. A film-to-substrate adhesion strength of 1862.24 mN and scratch hardness of about 4.1 GPa was achieved from this method. The TiO2/MgO/BHA film exhibited better wettability, higher surface energy and superior corrosion resistance compared to the bare Ti6Al4V substrate

Indoleninyl-substituted pyrimido[1,2-b]indazoles via a facile condensation reaction

A new series of pyrimido[1,2-b]indazoles bearing indolenine moieties was synthesized through a simple condensation reaction with up to 94% yield. The present method features the versatile formation of a pyrimidine ring with a broad range of substrates, great functional group compatibility and facile synthetic operation. The work offers opportunities in drug development as well as in materials scienc

Supramolecular assembly and spectroscopic characterization of indolenine–barbituric acid zwitterions

A series of indolenine and barbituric acid zwitterion scaffolds were synthesized with a maximum yield of 98% via the formation of C–C single bond. The structures were unambiguously elucidated by various spectroscopic techniques such as 1H, 13C NMR (1D, 2D), FT-IR and high-resolution mass spectrometry (HRMS). Single crystal X-ray crystallography analysis on 22, as the 22.DMF 1:1 solvate, confirms the presence of wellseparated iminium and enolate centres, and also confirms that the BA ring is highly twisted with respect to the indolenine ring due to steric hindrance. The presence of N–H∙∙∙O and N–H∙∙∙O- groups favour a 1D-supramolecular assembly in the solid-state. The orange or yellow solutions of the zwitterion exhibit an intense molar absorption coefficient, ε ranging between 0.21 × 104 and 2.93 × 104 M-1 cm-1 in the UV-vis region. Furthermore, the Intramolecular Charge Transfer (ICT) peak of zwitterion displays a hypsochromic shift in absorption behavior when the polarity of the solvent increases. Moreover, treatment of small amount of trifluoroacetic acid (TFA) to the DMF solution of 19 resulted in the protonation of an enolate of BA ring. This fundamental work provides valuable structural design and information for the construction of supramolecular chemistry and synthetic dyes based on indolenine substituted BA derivatives

Nanocellulose and natural deep eutectic solvent as potential biocatalyst system toward enzyme immobilization

This study reports the immobilization of Candida Rugosa lipase (CRL) onto nanocellulose (NC) extracted from almond shells using p-toluenesulfonic acid (PTSA) and sulfuric acid (ASS) with sugar-based natural deep eutectic solvent (NADES1a) as a biocatalyst system. The properties of both immobilized lipases were studied and compared to the free enzyme counterpart. Under optimized conditions (2 h, 40 ºC and pH 7.0), the immobilized CRL-PTSA-NADES1a and CRL-ASS-NADES1a gave a maximum specific activity of 4.9 U mg−1 and 6.57 U mg−1, respectively, compared to the free CRL (4.52 U mg−1). Both immobilized CRL showed better thermal stability, high catalytic activity and reusability up to 7 consecutive cycles. The half- life of the immobilized lipase was 14 ∼ 16 days greater than free lipase (27 days). The Brunauer-Emmett-Teller (BET) surface area of NC-ASS (20.76 m2 g−1) is higher compared to NC-PTSA (4.81 m2 g−1). The functional groups and morphology of the free and immobilized CRL were further determined by Fourier transformed infrared (FTIR) and scanning electron microscopy (SEM). These findings revealed that the immobilized CRL onto NCs and NADES1a as green materials and solvent, respectively had higher lipase immobilization efficiency and stability for the treatment of food contaminants in oils in order to satisfy increasing commercial demands in the oil industry

3-Monochloropropane-1,2-diol (3-MCPD): a review on properties, occurrence, mechanism of formation, toxicity, analytical approach and mitigation strategy

3-Monochloropropane-1,2-diol (3-MCPD) is one of the most common food contaminants in processed oils which forms mostly during the deodorization step of edible oil refining process. It has been detected in many types of food products such as infant formula, margarine, bread and soy sauce, which could result in kidney and testicular damage. The presence of 3-MCPD contaminant have been occurring for more a decade, which warrants a maximum permissible amount of 2 µg/kg body weight in food products in national and international levels. The purpose of this review is to provide an overview in the past 12 years on its physicochemical properties, occurrence, potential precursors and formation mechanism of 3-MCPD in foodstuffs. The toxicity, its quantification methods and mitigation strategy are also reviewed with an emphasis on the applicability, efficiency and issues encountered during the analysis. This review provides an elucidation regarding 3-MCPDEs and their food safety implications

Ternary glycerol-based deep eutectic solvents: physicochemical properties and enzymatic activity

The present study investigates deep eutectic solvents (DESs) as potential media for enzymatic hydrolysis. A series of ternary ammonium and phosphonium-based DESs were prepared at different molar ratios by mixing with aqueous glycerol (85%). The physicochemical properties including surface tension, conductivity, density, and viscosity were measured at a temperature range of 298.15 K – 363.15 K. The eutectic points were highly influenced by the variation of temperature. The eutectic point of the choline chloride: glycerol: water (ratio of 1: 2.55: 2.28) and methyl triphenylphosphonium bromide:glycerol: water (ratio of 1: 4.25:3.75) is 213.4 K and 255.8 K, respectively. The stability of the lipase enzyme isolated from the porcine pancreas (PPL) and Rhizopus niveus (RNL) toward hydrolysis in ternary DESs medium was investigated. The PPL showed higher activity compared to the RNL in DESs. Molecular docking simulation of the selected DES with the substrate (p-nitrophenyl palmitate) towardPPL was also reported. It is worth noting that ternary DES systems would be viable lipaseactivators in hydrolysis reactions

Electrochemical and FTIR studies of mechanically alloyed Mg2Ni

Mechanically alloyed Mg2Ni powders are prepared by a ball milling process and show the presence of small amounts of Ni, Mg, Ni(OH)(2) and Mg(OH)(2) from the X-ray diffraction. Voltammetry of the Mg2Ni powders is performed in 6M potassium hydroxide, and the hydrogen absorbing ability and surface oxidation of the alloy can be clearly seen. Voltammetry confirms the presence of a passivation film, which later breaks down at more positive potentials. Fourier transform infrared spectroscopy shows the formation of the passive film as Mg(OH)(2) after potential steps in the KOH solution