A metastable brominated nanodiamond surface enables room temperature and catalysis-free amine chemistry

Bromination of high-pressure high-temperature (HPHT) nanodiamond (ND) surfaces has not been explored and can open new avenues for increased chemical reactivity and diamond lattice covalent bond formation. The large bond dissociation energy of the diamond lattice-oxygen bond is a challenge that prevents new bonds from forming and most researchers simply use oxygen-terminated ND (alcohols and acids) as a reactive species. In this work, we transformed a tertiary alcohol-rich ND surface to an amine surface with 50% surface coverage and was limited by the initial rate of bromination. We observed that alkyl-bromide moieties are highly labile on NDs and are metastable as previously found using density functional theory. The instability of the bromine terminated ND is explained by steric hindrance and poor surface energy stabilization. The strong leaving group properties of the alkyl-bromide intermediate were found to form diamond-nitrogen bonds at room temperature and without catalysts. The chemical lability of the brominated ND surface led to efficient amination with NH3•THF at 298 K, and a catalyst-free Sonogashira-type reaction with an alkyne-amine produced an 11-fold increase in amination rate. Overlapping spectroscopies under inert, temperature-dependent and open-air conditions provided unambiguous chemical assignments. Amine-terminated NDs and folic acid were conjugated using sulfo-NHS/EDC coupling reagents to form amide bonds, confirming that standard amine chemistry remains viable. This work supports that a robust pathway exists to activate a chemically inert diamond surface at room temperature, which broadens the pathways of bond formation when a reactive alkyl-bromide surface is prepared. The unique surface properties of brominated and aminated nanodiamond reported here are impactful to researchers who wish to chemically tune diamond for quantum sensing applications or as an electron source for chemical transformations.

Synthesis, Characterization and Pharmacological Screening of Some Novel 2- substituted and 1(H)-substituted Benzimidazole Derivatives as potent Anti-cancer agents

The most of drugs containing Benzimidazole ring is a prominent structural motif found in numerous therapeutically active compounds. Benzimidazole and its synthetic analogues have been found to exhibit industrial, agricultural and biological application such as antitubercular, anti-inflammatory, analgesic, anticancer, anticoagulant, as well as good antifungal and anti microbial activity. Recent advances in technology considers microwave irradiation energy as the most efficient means of heating reactions for chemical transformations that can be accomplished in a minutes. Microwave irradiation assists organic synthesis (MAOS) not only helps in implementing green chemistry but also led to progress in organic synthesis. We report pharmacological screening of some novel 2 substituted and 1(h)-substituted Benzimidazole derivatives.

Nitrogen-neighboured single cobalt sites enable heterogeneous oxidase-type catalysis

Development of biomimetic catalytic systems that can imitate or even surpass natural enzymes remains an ongoing challenge 1–3. This is particularly true in the context of accessing non-natural reactions by bioinspired approaches, which offer intriguing possibilities for benign and affordable chemical synthesis 4. Exploiting the untapped potential of inorganic solids by translating complex knowledge in (bio)molecular-based systems may constitute a potentially useful strategy for such purpose 5, but efforts to capitalize on the minimum catalytic unit of a versatile solid matrix have been largely unsuccessful. Here, we show how an all-inorganic biomimetic system bearing robust nitrogen-neighboured single cobalt site/pyridinic-N site (Co-N4/Py-N) pairs can act cooperatively as an oxidase mimic, which renders an engaged coupling of oxygen (O2) reduction with synthetically beneficial chemical transformations. By developing this broadly applicable platform, the scalable synthesis of greater than 100 industrially and pharmaceutically appealing O-silylated compounds via the unprecedented aerobic oxidation of hydrosilane under ambient conditions is demonstrated. Moreover, this heterogeneous oxidase mimic also offers potential for expanding the catalytic scope of enzymatic synthesis. We anticipate that the strategy demonstrated here will pave a new avenue for understanding the underlying nature of redox enzymes and open up a new class of material systems for artificial biomimetics.

MOF-enabled confinement and related effects for chemical catalyst presentation and utilization

This review illustrates molecular-scale confinement, containment, isolation, and related concepts to present MOF-centric catalysts and to realize desired chemical transformations.

Synthesis and Antimicrobial Activity of (Z)-2-(4-((5-((1-Benzylpiperidin-4-yl)methylene)- 2,4-dioxothiazolidin-3-yl)methyl)-1H-1,2,3-triazol-1-yl)-N-phenylacetamides

In current times, researchers adopted the click chemistry approach for the synthesis of various druglike molecules by using a few reliable, feasible, practical and selective chemical transformations via click formation. In present work, we focussed on the most triazole clubbed thiazolidine-2,4-dione derivatives as the most promising motifs for broad biological application. A total of fifteen (CF-4a-o) derivatives were synthesized and well characterized with various analytical techniques.

Influence of electronic states of nanographs in carbon microcrystallines on surface chemistry of activated charcoal varieties

In this paper, the nature of the chemical activity of pyrolyzed nanostructured carbon materials (PNCM), in particular active carbon (AC), in reactions of electron transfer considered from a single position, reflecting the priority role of paramagnetic centers and edge defunctionaled carbon atoms of carbon microcristallites (CMC) due to pyrolysis of precursors. Clusters in the form of polycyclic aromatic hydrocarbons with open (OES) and closed (CES) electronic shells containing terminal hydrogen atoms (or their vacancies) and different terminal functional groups depending on specific model reactions of radical recombination, combination, replacement and elimination were used to model of nanographenes (NG) and CM. Quantum-chemical calculations of molecular models of NG and CMC and heat effects of model reactions were performed in frames of the density functional theory (DFT) using extended valence-splitted basis 6-31G(d) with full geometry optimization of concrete molecules, ions, radicals and NG models. The energies of boundary orbitals were calculated by means of the restricted Hartry-Fock method for objects with closed (RHF) and open (ROHF) electronic shells. The total energies of small negative ions (HOO-, HO-) and anion-radical О2•‾) were given as the sum of calculated total energies of these compounds and their experimental electron affinities. The estimation of probability of considered chemical transformations was carried out on the base on the well-known Bell-Evans-Polyani principle about the inverse correlation of the thermal effects of reactions and its activation energies. It is shown that the energy gap ΔЕ (energy difference of boundary orbitals levels) in simulated nanographens should depend on a number of factors: the periphery structure of models, its size and shape, the number and nature of various structural defects, electronic states of NG. When considering possible chemical transformations on the AC surface, rectangular models of NG were used, for which the simple classification by type and number of edge structural elements of the carbon lattice was proposed. Quantum chemical calculations of molecular models of NG and CNC and the energy of model reactions in frames of DTF showed that the chemisorption of free radicals (3O2 and N•O), as recombination at free radical centers (FRC), should occur with significant heat effects. Such calculations give reason to believe that FRC play an important role in formation of the functional cover on the periphery of NG in CMC of studied materials. On the base of of cluster models of active carbon with OES new ideas about possible reactions mechanisms of radical-anion О2•‾ formation and decomposition of hydrogen peroxide on the surface of active carbon are offered. Explanation of increased activity of AC reduced by hydrogen in H2O2 decomposition is given. It is shown that these PNCM models, as first of all AC, allow to adequately describe their semiconductor nature and acid-base properties of such materials.

NITRO CELLULOSE POWDER CHARGES OF LONG SERVICE LIFE: PROBLEMS AND THEIR POSSIBLE SOLUTIONS

One of the components of the problem of Ukraine's national security is the loading of warehouses with a variety of ammunition with an expired guaranteed storage period. The experience of storing ammunition shows that during long-term storage, propylene powder used in ammunition is capable of spontaneously undergoing various physical and chemical transformations, which negatively affects the ballistic characteristics of ammunition. The lack of ammunition production in Ukraine has led to the fact that ammunition is currently in operation, the storage time of which reaches 25-30 years or more. This article analyzes publications devoted to scientific research related to the problems of ballistic stability of propellants. A number of factors are presented that affect the physicochemical stability of powder charges during their long-term operation. The generalizing data on changes in the main ballistic characteristics of ammunition at different periods of their storage are presented. It is assumed that one of the ways to improve the ballistic and energy characteristics of ammunition with long service lives can be the regeneration of nitrocellulose powder charges. It is shown that at present there are no methods for the regeneration of propellant charges of long service life. However, there are encouraging data on the treatment of propellants with hydrogen peroxide, on the basis of which a technology can be developed for the complete or partial restoration of the ballistic and energy characteristics of the propellant charge. It is presented that the predictive assessment of changes in the characteristics of ammunition with long service lives does not correspond to their real indicators. It has been determined that the problem of nitrocellulose propellants of long service life is complex and, on the basis of its solution, theoretical and methodological foundations of the regeneration of nitrocellulose propellant charges can be developed to homologate the ballistic and energy characteristics of ammunition.