Chemistry of Materials
DOI: 10.1021/acs.chemmater.3c02088
Photoinduced 1,3‐Dipolar Cycloadditions of Cyclic Enones and 2,5‐Disubstituted Tetrazoles: An Unprecedented Pathway to Polysubstituted Pyrazolines and Pyrazoles.
We report herein the syntheses of original pyrazolines and pyrazoles through 1,3-dipolar cycloaddition of cyclic enones with 2,5-disubstituted nitrile imines achieved via photochemical activation of 2,5-diaryl substituted tetrazoles. Monitoring of the reactions, similar to nitrile imine-mediated tetrazole-ene cycloadditions (NITEC), could be performed by means of UV-vis absorption and emission measurements. The presence or absence of substituents in the alpha position of the ketone function makes it possible to direct these reactions towards the selective formation of pyrazoles or pyrazolines. The choice of the cyclic enones and 2,5-disubstituted tetrazoles proved crucial for the fluorescence properties of the polycyclic derivatives obtained.
The Moon‐Forming Impact and the Autotrophic Origin of Life
The Moon-forming impact vaporized part of Earth’s mantle, and turned the rest into a magma ocean, from which carbon dioxide degassed into the atmosphere, where it stayed until water rained out to form the oceans. The rain dissolved CO2 and made it available to react with transition metal catalysts in the Earth's crust so as to ultimately generate the organic compounds that form the backbone of microbial metabolism. The Moon-forming impact was key in building a planet with the capacity to generate life in that it converted carbon on Earth into a homogeneous and accessible substrate for organic synthesis. Today all ecosystems, without exception, depend upon primary producers, organisms that fix CO2. According to theories of autotrophic origin, it has always been that way, because autotrophic theories posit that the first forms of life generated all the molecules needed to build a cell from CO2, forging a direct line of continuity between Earth's initial CO2-rich atmosphere and the first microorganisms. By modern accounts these were chemolithoautotrophic archaea and bacteria that initially colonized the crust and still inhabit that environment today.
Valkyrie Probes: A Novel Class of Enzyme‐Activatable Photosensitizers based on Sulfur‐ and Seleno‐Rosamines with Pyridinium Unit
The rational design of activatable photosensitizers (aPSs) uncaged by specific disease biomarkers is currently booming due to their positive attributes to achieve targeted photodynamic therapy (PDT). In this context, we present here the synthesis and detailed photophysical characterization of a novel class of hetero-rosamine dyes bearing sulfur or selenium as bridging heavy atom and 4-pyridyl meso-substituent as optically tunable group. The main feature of such photoactive platforms is the spectacular change of their spectral properties depending on the caging/decaging status of their 4-pyridyl moiety (cationic pyridinium vs. neutral pyridine). The preparation of two alkaline phosphatase (ALP)-responsive probes (named Valkyrie probes) was achieved through formal N-quaternarization with 4-phosphoryloxybenzyl, the traditional recognition moiety for this important diagnostic enzyme. Bio-analytical validations including fluorescence/singlet oxygen phosphorescence enzyme assays and RP-HPLC-fluorescence/-MS analyses have enabled us to demonstrate the viability and effectiveness of this novel photosensitizer activation strategy. Since sulfur-containing Valkyrie probe also retains high fluorogenicity in the orange-red spectral range, this study highlights meso-pyridyl-substituted S-pyronin scaffolds as valuable candidates for the rapid construction of molecular phototheranostic platforms suitable for combined fluorescence diagnosis and PDT.
Revealing the unique role of water in the formation of benzothiazoles: an experimental and computational study
We present here a joint experimental and computational study on the formation of benzothiazoles. Our investigation reveals a green protocol for accessing benzothiazoles from acyl chlorides using either water alongside a reducing agent as the reaction medium or in combination with stoichiometric amounts of a weak acid, instead of the harsh conditions and catalysts previously reported. Specifically, we show that a protic solvent, particularly water, enables the formation of 2-substituted benzothiazoles from N-acyl 1,2-aminothiophenols already at room temperature, without the need for strong acids or metal catalysts. DFT Molecular Dynamics simulations coupled with advanced enhanced sampling techniques provide a clear understanding of the catalytic role of water. We demonstrate how bulk water – due to its extended network of hydrogen bonds and an efficient Grotthus mechanism – provides a reaction path that strongly reduces the reaction barriers compared to aprotic environments, namely more than 80 kJ/mol for the first reaction step and 250 kJ/mol for the second. Finally, we discuss the influence of different aliphatic and aromatic substituents with varying electronic properties on chemical reactivity. Besides providing in-depth mechanistic insights, we believe that our findings pave the way for a greener route toward an important class of bioactive molecules.
Co(II) acetate assisted direct synthesis of acyl hydrazones from acyl hydrazides under mild condition
Acyl hydrazones are a class of synthetically important organic compounds that are recurrently in high demand for synthesis and use in various fields of chemistry and biology. We report the first Co(II) catalyzed one-component one-pot sustainable synthesis of acyl hydrazones only from acyl hydrazides under mild reaction conditions. Traditional and contemporary methodologies use two components (usually acyl hydrazides and aldehydes/ketones/alcohols/styrene) as the coupling partners. Our protocol, on the other hand, involves the in situ generation of aldehyde intermediate (detected by gas chromatography) from the acyl hydrazide, which then undergoes condensation with another molecule of the same acyl hydrazide in the same pot to yield acyl hydrazones in presence of mild base K2CO3 and low-cost Co(OAc)2·4H2O as catalyst. This method shows good functional group tolerance with good to excellent yield of products. Furthermore, some of the resulting acyl hydrazones have been used as synthetic precursors and explored in various post-synthetic modifications to afford N-heterocyclic compounds. Furthermore, photoswitchable properties of few synthesized acyl hydrazones are also explored using their E/Z isomerization around the C=N bond, as realized by high-pressure liquid chromatography (HPLC) and UV-vis spectroscopic studies.
[ASAP] Multiplex Quantification of Exosomes via Multiple Types of Nanobeads Labeling Combined with Laser Scanning Detection
Analytical Chemistry
DOI: 10.1021/acs.analchem.3c02374
[ASAP] Elucidating Structural Transition Dynamics in the Magnesium Cathode MgCr2O4
Chemistry of Materials
DOI: 10.1021/acs.chemmater.3c01219
Ab Initio Molecular Dynamics Study of H2 Dissociation Mechanisms on Cu13 and Defective Graphene‐supported Cu13 Clusters: Active Sites, Energy Barriers and Adsorption States
The preferred reaction mechanisms of H2 dissociation on Cu13 and defective graphene-supported Cu13 clusters are presented. The dissociation energy barrier, −0.31 eV, on the defective graphene-supported Cu13 cluster is substantially lowered compared to that on the pure Cu13 cluster at 0.30 eV, and the dissociated chemisorption strength on the defective graphene-supported Cu13 cluster is also enhanced compared to the pure Cu13 cluster.
Abstract
Ab initio molecular dynamics calculations were performed to study H2 dissociation mechanisms on Cu13 and defective graphene-supported Cu13 clusters. The study reveals that seven types of corresponding dissociation processes are found on the two clusters. The average dissociation energy barriers are 0.51 eV on the Cu13 cluster and 0.12 eV on the defective graphene-supported Cu13 cluster, which are lowered by ~19 % and ~81 % compared with the pristine Cu(111) surface, respectively. Furthermore, compared with the pure Cu13 cluster, the average dissociation energy barrier on the defective graphene-supported Cu13 cluster is substantially reduced by about 76 %. The preferred dissociation mechanisms on the two clusters are H2 located at a top-bridge site with the barrier heights of 0.30 eV on the Cu13 cluster and −0.31 eV on the defective graphene-supported Cu13 cluster. Analysis of the H−Cu bond interactions in the transition states shows that the antibonding-orbital center shifts upward on the defective graphene-supported Cu13 cluster compared with the one on the Cu13 cluster, which explains the reduction of the dissociation energy barrier. The average adsorption energy of dissociated H atoms is also greatly enhanced on the defective graphene-supported Cu13 cluster, about twice that on the Cu13 cluster.
Water Induced Alterations in Self‐Assembly of a Bio‐Surfactant in Deep Eutectic Solvent for Enhanced Enzyme Activity
Presence of water in deep eutectic solvent (DES) alters the inherent structure of DES, and hence promotes surfactant aggregation. The colloidal solution having aggregated structures of sodium N-lauroyl sarcosinate in water-diluted DES (Choline chloride :Glycerol=1: 2) acts as an ideal media to provide structural stability to Cytochrome-c, which shows enhanced enzymatic activity.
Abstract
Deep eutectic solvents (DESs) meet important requirements for green solvent technology, including non-toxicity, biodegradability, sustainability, and affordability. Despite possessing low cohesive energy density than water, DESs have been found to support the self-assembly of amphiphiles. It is very much pertinent to examine the effect of water on self-assembly of surfactants in DESs as the presence of water alters the inherent structure of DES, which is expected to affect the characteristic properties of self-assembly. Following this, we have investigated the self-assembly of amino-acid based surfactant, Sodium N-lauroyl sarcosinate (SLS), in DES-water mixtures (10, 30 and 50 w/w% of water) and explored the catalytic activity of Cytochrome-c (Cyt-c) in the formed colloidal systems. Investigations using surface tension, fluorescence, dynamic light scattering (DLS), and isothermal titration calorimetry (ITC) have shown that DES-water mixtures promote the aggregation of SLS, resulting in the lower critical aggregation concentration (cac ∼1.5–6-fold) of the surfactant as compared to water. The nanoclustering of DES at low water content and it's complete de-structuring at high water content affects the self-assembly in a contrasting manner governed by different set of interactions. Further, Cyt-c dispersed in DES-water colloidal solutions demonstrated 5-fold higher peroxidase activity than that observed in phosphate buffer.