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Alpha-lactalbumin (α-LA) and binding of zinc cations to protein were studied. Molecular characteristics of protein was determined by MALDI-TOF/MS and electrophoresis SDS-PAGE, and also, for complexes, it was determined by spectroscopic techniques (ATR-FT-IR and Raman) and microscopic techniques (SEM along with an EDX detector and also TEM). The pH dependence of zeta potential of α-LA was determined in saline solution. The zinc binding to the protein mechanism was investigated; zinc binding to protein kinetics, the molecular modeling by the DFT method, and electron microscopy (SEM and TEM) for microstructure observation were performed. The experiments performed indicate a quick binding process (equilibrium takes place after 2 min of incubation) which occurs onto the surface of α-LA. Zinc cations change the conformation of the protein and create spherical particles from the morphological point of view. DFT studies indicate the participation of acidic functional groups of the protein (aspartic acid and glutamic acid residues), and these have a decisive influence on the interaction with zinc cations. Application studies of general toxicity and cytotoxicity and bioavailability were conducted.

A computational DFT-D3 study revealed a new polymerization-like mechanism comprising alternate epoxide and CO2 activation steps and a nested CO2 activation pathway for CO2 fixation of epoxides catalyzed by multifunctional non-halide organocatalysts.

Rechargeable aqueous Zn/S batteries exhibit high capacity and energy density. However, the long-term battery performance is bottlenecked by the sulfur side reactions and serious Zn anode dendritic growth in the aqueous electrolyte medium. This work addresses the problem of sulfur side reactions and zinc dendrite growth simultaneously by developing a unique hybrid aqueous electrolyte using ethylene glycol as a co-solvent. The designed hybrid electrolyte enables the fabricated Zn/S battery to deliver an unprecedented capacity of 1435 mAh g-1 and an excellent energy density of 730 Wh kg-1 at 0.1 Ag-1 . In addition, the battery exhibits capacity retention of 70% after 250 cycles even at 3 Ag-1 . Moreover, the cathode charge-discharge mechanism studies demonstrate a multi-step conversion reaction. During discharge, the elemental sulfur is sequentially reduced by Zn to S2- ( S8→Sx2-→S22-+S2-)${{\rm{S}}_8}{\bm{ \to }}{\rm{S}}_{\rm{x}}^{2{\bm{ - }}}{\bm{ \to }}{\rm{S}}_2^{2{\bm{ - }}}{\bm{ + }}{{\rm{S}}^{2{\bm{ - }}}})$ , forming ZnS. On charging, the ZnS and short-chain polysulfides will oxidize back to elemental sulfur. This electrolyte design strategy and unique multi-step electrochemistry of the Zn/S system provide a new pathway in tackling both key issues of Zn dendritic growth and sulfur side reactions, and also in designing better Zn/S batteries in the future. Agency for Science, Technology and Research (A*STAR) National Research Foundation (NRF) The authors acknowledge the grant from the National Research Foundation of Singapore (NRF) Investigatorship Award NRFI2017-08/NRF2016NRF-NRFI001-22 and A*STAR under the Advanced Manufacturing and Engineering (AME) programmatic fund number A20H3g2140.

Flavonoids, a class of polyphenolic substances widely present in the plant realm, are considered as ideal hypochlorite scavengers. However, to our knowledge, little study has focused on the structure-activity relationship between flavonoids and hypochlorite scavenging capacity. Herein, we report for the first time the three-dimensional quantitative structure and activity relationship (3D-QSAR) combined with comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA). Four models derived from CoMFA and CoMSIA with different combinations of descriptors were built and compared; the CoMFA model, which included both steric and electrostatic fields, showed great potential (

The nucleophilic substitution mechanism of enantioselective allylation of α-chloro glycinate catalyzed by squaramide organocatalysts was studied using density functional theory. Based on a comprehensive study of SN1 and SN2 pathways of a catalyst-free reaction, we found that the catalytic reaction slightly favors the SN1 mechanism, instead of the previously proposed SN2 mechanism. Further investigation of different leaving groups and nucleophiles revealed that this is not limited to the present reaction, and the SN1 mechanism might have been generally overlooked. For the squaramide-catalyzed reactions, the SN1 mechanism was predicted to be preferred. However, the rate-determining step of the SN1 pathway has changed from the chloride-leaving step to the C-C bond-formation step. Therefore, a first-order dependence on both substrates was predicted, in agreement with the observed second-order kinetics. Intriguingly, the lowest-energy enantioselective transition states (TSs) originate from different pathways; R-inducing TS corresponds to the SN1 pathway, while S-inducing TS corresponds to SN2. The calculated enantiomeric excesses of two squaramide catalysts agree well with the experimental values. Given the ubiquity of nucleophilic substitution reactions in chemistry and biology, we believe that our finding will inspire more studies that will lead to an improved mechanistic understanding of important chemical reactions, and it may even lead to better catalysts.

Controllable fabrication of enantiospecific molecular superlattices is a matter of imminent scientific and technological interest. Herein, we demonstrate that long-range superlattice chirality in molecular self-assemblies can be tailored by tuning the interplay of weak intermolecular non-covalent interactions between hexaphenylbenzene-based enantiomers. By means of high-resolution scanning tunneling microscopy measurements, we demonstrate that the functionalization of a hexaphenylbenzene-based molecule with fluorine (F) atoms leads to the formation of molecular self-assemblies with distinct long-range chiral recognition patterns. We employed density functional theory calculations to quantify F-mediated lone pair F⋯π, C–H⋯F, and F⋯F interactions attributed to the distinct enantiospecific molecular self-organizations. Our findings underpin a viable route to fabricate long-range chiral recognition patterns in supramolecular assemblies by engineering the weak non-covalent intermolecular interactions.

Preorganization is a common strategy to align halogen bond (XB) donors to form two or more halogen bonds simultaneously. Previous approaches have utilized various non-covalent interactions such as steric interactions, π⋯π stacking, and hydrogen bond interactions. However, some of the introduced aligning interactions may compete with halogen bond interactions if the donors are employed in catalysis. To achieve thiourea-like properties, we have designed in silico several neutral bidentate halogen bond donors in whose structures the donor moieties are connected via covalent bonds. Compared to previous XB catalyst designs, the new design does not involve other potentially competitive non-covalent interactions such as hydrogen bonds. One of the designed XB donors can deliver strong halogen bonds, with a O–I distance as short as 2.64 A. Density functional theory (DFT) calculations predicted that our designed catalysts may catalyze important organic reactions on their own, particularly for those reactions that involve (developing) soft anions such as thiolates.

Deciphering rich non-covalent interactions that govern many chemical and biological processes is crucial for the design of drugs and controlling molecular assemblies and their chemical transformations. However, real-space characterization of these weak interactions in complex molecular architectures at the single bond level has been a longstanding challenge. Here, we employed bond-resolved scanning probe microscopy combined with an exhaustive structural search algorithm and quantum chemistry calculations to elucidate multiple non-covalent interactions that control the cohesive molecular clustering of well-designed precursor molecules and their chemical reactions. The presence of two flexible bromo-triphenyl moieties in the precursor leads to the assembly of distinct non-planar dimer and trimer clusters by manifold non-covalent interactions, including hydrogen bonding, halogen bonding, C–H⋯π and lone pair⋯π interactions. The dynamic nature of weak interactions allows for transforming dimers into energetically more favourable trimers as molecular density increases. The formation of trimers also facilitates thermally-triggered intermolecular Ullmann coupling reactions, while the disassembly of dimers favours intramolecular cyclization, as evidenced by bond-resolved imaging of metalorganic intermediates and final products. The richness of manifold non-covalent interactions offers unprecedented opportunities for controlling the assembly of complex molecular architectures and steering on-surface synthesis of quantum nanostructures., A real-space characterization of dynamic non-covalent interactions in molecular assemblies and chemical reactions at the atomic bond level.

The drug-resistant pathogen phenomenon, resulting in infections and deaths that are increasingly difficult to treat, requires research into searching new potential antimicrobial agents. The presented study is focused on the investigation of impact of silver ions (Ag

We report a computational analysis of the [5,5] bicyclic guanidine-catalyzed asymmetric cycloaddition reaction of anthrones. Based on extensive conformational search of key intermediates and transition states on the potential energy surface and density functional theory calculations, we studied five plausible binding modes between the guanidine catalyst and substrates for this reaction. Our results indicate that the most favorable pathway is a stepwise conjugate addition-Aldol sequence via the dual hydrogen-bond binding mode. The predicted level of enantioselectivity is in good agreement with experimental values. Trends in variation of substrates and catalysts have also been reproduced by our calculations. Decomposition analysis revealed the significance of aromatic interactions in stabilizing the key enantioselectivity-determining transition state structures.

Chemistry campaigns identified amphiphilic indolyl Mannich bases as novel membrane-permeabilizing antimycobacterials. Spiroketal analogs of this series showed increased potency, and the lead compound 1 displayed efficacy in a mouse model of tuberculosis. Yet the mechanism by which the spiroketal moiety accomplished the potency "jump" remained unknown. Consistent with its membrane-permeabilizing mechanism, no resistant mutants could be isolated against indolyl Mannich base 2 lacking the spiroketal moiety. In contrast, mutations resistant against spiroketal analog 1 were obtained in mycobacterial membrane protein large 3 (MmpL3), a proton motive force (PMF)-dependent mycolate transporter. Thus, we hypothesized that the potency jump observed for 1 may be due to MmpL3 inhibition acquired by the addition of the spiroketal moiety. Here we showed that 1 inhibited MmpL3 flippase activity without loss of the PMF, colocalized with MmpL3tb-GFP in intact organisms, and yielded a consistent docking pose within the "common inhibitor binding pocket" of MmpL3. The presence of the spiroketal motif in 1 ostensibly augmented its interaction with MmpL3, an outcome not observed in the nonspiroketal analog 2, which displayed no cross-resistance to mmpL3 mutants, dissipated the PMF, and docked poorly in the MmpL3 binding pocket. Surprisingly, 2 inhibited MmpL3 flippase activity, which may be an epiphenomenon arising from its wider membrane disruptive effects. Hence, we conclude that the potency increase associated with the spiroketal analog 1 is linked to the acquisition of a second mechanism, MmpL3 inhibition. In contrast, the nonspiroketal analog 2 acts pleiotropically, affecting several cell membrane-embedded targets, including MmpL3, through its membrane permeabilizing and depolarizing effects.

Controllable fabrication of enantiospecific molecular superlattices is a matter of imminent scientific and technological interest. Herein, we demonstrate that long-range superlattice chirality in molecular self-assemblies can be tailored by tuning the interplay of weak intermolecular non-covalent interactions between hexaphenylbenzene-based enantiomers. By means of high-resolution scanning tunneling microscopy measurements, we demonstrate that the functionalization of a hexaphenylbenzene-based molecule with fluorine (F) atoms leads to the formation of molecular self-assemblies with distinct long-range chiral recognition patterns. We employed density functional theory calculations to quantify F-mediated lone pair F⋯π, C-H⋯F, and F⋯F interactions attributed to the distinct enantiospecific molecular self-organizations. Our findings underpin a viable route to fabricate long-range chiral recognition patterns in supramolecular assemblies by engineering the weak non-covalent intermolecular interactions.

Herein, we report the conjugate addition of α,β-unsaturated carbonyl compounds to thiophene derivatives. We used a 2-iodoimidazolinium triflate salt as a halogen-bonding donor, which afforded moderate-to-excellent yields of the corresponding alkylated thiophenes. Insight into the catalytic process was obtained from 1 H NMR spectroscopy studies and DFT calculations, which indicated a halogen-bonding-supported mechanism with limited Bronsted acid catalysis.

Halogen-bond (XB) catalyzed reactions could also be catalyzed by Brønsted acids, which may complicate the picture of the true activation pathway for these reactions. Herein, we report the first density functional theory study of the mechanistic pathways for the uncatalyzed, iodoimidazolinium halogen bond catalyzed, and a competitive Brønsted acid-catalyzed reduction of quinoline by Hantzsch ester. The uncatalyzed reaction was found to proceed via stepwise pathways. In the lowest energy pathway, proton transfer from Hantzsch ester, a weak Brønsted acid, to quinoline prior to hydride reduction was identified as the key to the lowered energy barriers compared to other reaction pathways. The same reaction steps are involved in the XB-catalyzed pathway, but with substantially lowered reaction barriers, particularly for the hydride-transfer steps. In contrast to the general belief that halogen bond catalysts bind to the electrophile quinoline and activate it by lowering its LUMO energy, we discovered that it is preferable to lower the LUMO energy of quinoline through protonation by Hantzsch ester as a Brønsted acid and stabilize the conjugate anion of Hantzsch ester via halogen bond. Finally, our calculations reveal that the iodoimidazolinium type of catalyst is prone to reduction by Hantzsch ester, generating a Brønsted acid as product. The Brønsted acid catalyzed pathway was calculated to be competitive with the halogen bond catalyzed pathway. Our theoretical findings highlight the need to be cautious when applying iodoimidazolinium catalysts in organocatalysis, and we hope it will aid the design of new halogen bond catalysts that could avoid undesirable Brønsted acid catalysis.

Adsorption behavior and corrosion inhibition mechanism of imidazole and its C2-halogenated analogues (with the halogen atoms being Cl, Br or I) on Fe(1 0 0) surface were investigated by DFT periodic slab calculations and electrochemical techniques. DFT calculations revealed that C2-halogenated imidazoles adopt the tilted conformation on Fe surface with a significantly lengthened C–halogen bond and readily undergo facile dissociation at the halo-substitution with calculated adsorption energies −3.95, −3.76 and −3.48 eV for 2-I-Imz, 2-Br-Imz and 2-Cl-Imz, respectively. Electrochemical evaluations supported with surface characterization studies showed that the inhibitor molecules adsorb onto mild steel with 2-I-Imz having the highest inhibition efficiency of 83.5%. The trend of observed inhibition efficiencies correlates with adsorption energies and kinetic behavior predicted by the MD approach. The strength of adsorption in the order I > Br > Cl. The present study therefore provides a thorough mechanistic understanding of the role halogen substituents could play on the corrosion inhibitive performance of small organic systems.

A high-throughput smartphone-based colorimetric reader (HSCR) was developed to quantitatively detect hypochlorite in aqueous solution and determine hypochlorite scavenging capacity in high-throughput format by a blue probe DMMA-IR780, which changes from deep blue to pink upon epoxidation by hypochlorite on one of the double bonds. The reaction mechanism between probe and hypochlorite was study by mass spectrum and attribute to the formation and degradation of chlorohydrins. The color change was recorded by a smartphone-based colorimetric reader to apply into an android-based application for on-site determination and analysis. This portable system could quantify hypochlorite with linearity range of 0.43 to 875 μM and limit of detection at 0.08 μM. Taking advantages of smartphone and probe DMMA-IR780, the assay provides a cost-effective and hand-held platform for on-site HOCl determination and quantification of hypochlorite scavenging capacity of dietary antioxidants.

Controllable fabrication of the enantiospecific molecular superlattices is a matter of imminent scientific and technological interest. Herein, we demonstrate that long-range superlattice chirality in molecular self-assemblies can be tailored by tuning the interplay of weak intermolecular non-covalent interactions. Different chiral recognition patterns are achieved in the two molecular self-assemblies comprised by two molecular enantiomers with identical steric conformations, derived from the hexaphenylbenzene – the smallest star-shaped polyphenylene. By means of high-resolution scanning tunneling microscopy measurements, we demonstrate that functionalization of star-shaped polyphenylene with fluorine (F) atoms leads to the formation of molecular self-assemblies with the distinct long-range chiral recognition patterns. We employed the density functional theory calculations to quantify F-mediated lone pair F ···π, C-H··· F, F···F interactions attributed to the tunable enantiospecific molecular self-organizations. Our findings underpin a viable route to tailor long-range chiral recognition patterns in supramolecular assemblies by engineering the weak non-covalent intermolecular interactions.

The reversibility of metal anode is a fundamental challenge to the lifetime of rechargeable batteries. Though being widely employed in aqueous energy storage systems, metallic zinc suffers from dendrite formation that severely hinders its applications. Here we report texturing Zn as an effective way to address the issue of zinc dendrite. An in‐plane oriented Zn texture with preferentially exposed (002) basal plane is demonstrated via a sulfonate anion‐induced electrodeposition, noting no solid report on (002) textured Zn till now. Anion‐induced reconstruction of zinc coordination is revealed to be responsible for the texture formation. Benchmarking against its (101) textured‐counterpart by the conventional sulphate‐based electrolyte, the Zn (002) texture enables highly reversible stripping/plating at a high current density of 10 mA cm−2, showing its dendrite‐free characteristics. The Zn (002) texture‐based aqueous zinc battery exhibits excellent cycling stability. The developed anion texturing approach provides a pathway towards exploring zinc chemistry and prospering aqueous rechargeable batteries. National Research Foundation (NRF) Accepted version The authors appreciate the financial support by National Research Foundation of Singapore (NRF) investigatorship award number NRF-NRFI2017-08 (NRF2016NRF-NRFI001-22). The authors would like to acknowledge the Facility for Analysis, Characterization, Testing and Simulation, Nanyang Technological University, Singapore, for use of their electron microscopy/X-ray facilities.

Here, we present a collection of publicly availableintrinsic aqueous solubility data of 829 drug-likecompounds. Four different machine learning algorithms(random forest, light GBM, partial least squares andLASSO) coupled with multi-stage permutationimportance for feature selection and Bayesian hyperparameter optimization were employed for theprediction of solubility based on chemical structuralinformation. Our results have shown that LASSOyielded the best predictive ability on an external test setwith and RMSE(test) of 0.70 log points and 105 featuresin the model. Taking into account the number ofdescriptors as well, an RF model achieved the bestbalance between complexity and predictive ability withan RMSE(test) of 0.72 with only 17 features. Wepropose a ranking score for choosing the best model, astest set performance is only one of the factors in creatingan applicable model. The ranking score is a weightedcombination of generalization, number of featuresinvolved and test set performance The data related to this paper can be downloaded from 10.5281/zenodo.3968754

The reversibility of metal anode is a fundamental challenge to the lifetime of rechargeable batteries. Though being widely employed in aqueous energy storage systems, metallic zinc suffers from dendrite formation that severely hinders its applications. Here we report texturing Zn as an effective way to address the issue of zinc dendrite. An in-plane oriented Zn texture with preferentially exposed (002) basal plane is demonstrated via a sulfonate anion-induced electrodeposition, noting no solid report on (002) textured Zn till now. Anion-induced reconstruction of zinc coordination is revealed to be responsible for the texture formation. Benchmarking against its (101) textured-counterpart by the conventional sulphate-based electrolyte, the Zn (002) texture enables highly reversible stripping/plating at a high current density of 10 mA cm-2 , showing its dendrite-free characteristics. The Zn (002) texture-based aqueous zinc battery exhibits excellent cycling stability. The developed anion texturing approach provides a pathway towards exploring zinc chemistry and prospering aqueous rechargeable batteries.

In this work, the molecular mechanism of Lactobacillus paracasei bio-colloid clumping under divalent metal ions treatment such as zinc, copper and magnesium at constant concentrations was studied. The work involved experimental (electrophoretic - capillary electrophoresis in pseudo-isotachophoresis mode, spectroscopic and spectrometric - FT-IR and MALDI-TOF-MS, microscopic - fluorescent microscopy, and flow cytometry) and theoretical (DFT calculations of model complex systems) characterization. Electrophoretic results have pointed out the formation of aggregates under the Zn2+ and Cu2+ modification, whereas the use of the Mg2+ allowed focusing the zone of L. paracasei biocolloid. According to the FT-IR analysis, the major functional groups involved in the aggregation are deprotonated carboxyl and amide groups derived from the bacterial surface structure. Nature of the divalent metal ions was shown to be one of the key factors influencing the bacterial aggregation process. Proteomic analysis showed that surface modification had a considerable impact on bacteria molecular profiles and protein expression, mainly linked to the activation of carbohydrate and nucleotides metabolism as well with the transcription regulation and membrane transport. Density-functional theory (DFT) calculations of modeled Cu2+, Mg2+ and Zn2+ coordination complexes support the interaction between the divalent metal ions and bacterial proteins. Consequently, the possible mechanism of the aggregation phenomenon was proposed. Therefore, this comprehensive study could be further applied in evaluation of biocolloid aggregation under different types of metal ions.

Currently, rapid evaluation of the physicochemical parameters of drug candidates, such as lipophilicity, is in high demand owing to it enabling the approximation of the processes of absorption, distribution, metabolism, and elimination. Although the lipophilicity of drug candidates is determined using the shake flash method (n-octanol/water system) or reversed phase liquid chromatography (RP-LC), more biosimilar alternatives to classical lipophilicity measurement are currently available. One of the alternatives is immobilized artificial membrane (IAM) chromatography. The present study is a continuation of our research focused on physiochemical characterization of biologically active derivatives of isoxazolo[3,4-b]pyridine-3(1H)-ones. The main goal of this study was to assess the affinity of isoxazolones to phospholipids using IAM chromatography and compare it with the lipophilicity parameters established by reversed phase chromatography. Quantitative structure–retention relationship (QSRR) modeling of IAM retention using differential evolution coupled with partial least squares (DE-PLS) regression was performed. The results indicate that in the studied group of structurally related isoxazolone derivatives, discrepancies occur between the retention under IAM and RP-LC conditions. Although some correlation between these two chromatographic methods can be found, lipophilicity does not fully explain the affinities of the investigated molecules to phospholipids. QSRR analysis also shows common factors that contribute to retention under IAM and RP-LC conditions. In this context, the significant influences of WHIM and GETAWAY descriptors in all the obtained models should be highlighted.

Prediction of the retention time from the molecular structure using quantitative structure-retention relationships is a powerful tool for the development of methods in reversed-phase HPLC. However, its fundamental limitation lies in the fact that low error in the prediction of the retention time does not necessarily guarantee a prediction of the elution order. Here, we propose a new method for the prediction of the elution order from quantitative structure-retention relationships using multi-objective optimization. Two case studies were evaluated: (i) separation of organic molecules in a Supelcosil LC-18 column, and (ii) separation of peptides in seven columns under varying conditions. Results have shown that, when compared to predictions based on the conventional model, the relative root mean square error of the elution order decreases by 48.84%, while the relative root mean square error of the retention time increases by 4.22% on average across both case studies. The predictive ability in terms of both retention time and elution order and the corresponding applicability domains were defined. The models were deemed stable and robust with few to no structural outliers.

The strong, specific, and directional halogen bond (XB) is an ideal supramolecular synthon in crystal engineering, as well as rational catalyst and drug design. These attributes attracted strong growing interest in halogen bonding in the past decade and led to a wide range of applications in materials, biological, and catalysis applications. Recently, various research groups exploited the XB mode of activation in designing halogen-based Lewis acids in effecting organic transformation, and there is continual growth in this promising area. In addition to the rapid advancements in methodology development, computational investigations are well suited for mechanistic understanding, rational XB catalyst design, and the study of intermediates that are unstable when observed experimentally. In this review, we highlight recent computational studies of XB organocatalytic reactions, which provide valuable insights into the XB mode of activation, competing reaction pathways, effects of solvent and counterions, and design of novel XB catalysts.

In this study, three series of new indazole derivatives linked with double long alkyl-chains (N-alkyl-chain, O-alkyl-chain or S-alkyl-chain) were designed. Then, to estimate the potential used as corrosion inhibitors and effects of number, type and length, their geometries, frontier molecular orbital energies, global electrophilicity index, nucleophilicity index, absolute electronegativity, absolute hardness, softness, a fraction of electrons transferred, Fukui functions and binding energy were investigated by the density functional theory method and molecular dynamics simulation. The results showed that the introduced second long chain has significant effects on the anti-corrosive properties and is very helpful for improving the inhibition efficiency. Among three long-chains, the N-alkyl-chain is favorable for donating electrons to metals, while the S-chain is good for accepting electrons to form feedback bonds. Both the N-alkyl-chain and O-alkyl-chains are much more convenient for forming big water-block than the S-alkyl chain. As a result, inhibitors linked with two N-alkyl-chains may have higher inhibition efficiency than others. When the length of the long-chain is longer than eight carbon atoms, most anti-corrosive properties will not change any more obvious, but the binding energy will decrease, and the adsorption strength between inhibitors and metals may be weakened because of the curling, bending and repulsion of long chains. The N3/O/S, N1, C1, C4, C6 and C7 atoms are possible reactive sites to donate electrons, while N2, C1, C4, C5, C7 and N1 atoms are the main electrophilic centers to form feedback bonds. This work may be helpful for developing new multi-chain organic corrosion inhibitors.

Herein, we report on fluorophore-tagged Grubbs catalysts as turn-on fluorescent probes for the sensitive detection and quantitation of ethylene, a plant hormone that plays a critical role in many phases of plant growth and fruit ripening. The ruthenium-based weak fluorescent probes were prepared handily through the metathesis reaction between the first-generation Grubbs catalyst and selected fluorophores that have high quantum yields and contain terminal vinyl groups. Upon exposure to ethylene, fluorescence enhancement was observed via the release of fluorophore from the probe. Our probe shows an excellent limit of detection for ethylene at 0.9 ppm in air and was successfully applied for monitoring ethylene released during the fruit-ripening process. Our work opens up a new avenue of application of Grubbs catalysts for bioanalytical chemistry of ethylene, which is critically important in plant biology, agriculture, and food industry.

Singlet oxygen plays an important role in cancer chemotherapy and biology of reactive oxygen species. In recent years, there are some reports of selective fluorescent probes for detection and imaging of singlet oxygen but the existing probes have some major drawbacks including complicated synthetic routes, poor fluorescence enhancement effects. We report herein that anthracenylmethyl modified non-fluorescent derivatives of fluorescein and rhodamine-6G can reacts with 1O2, which resulted in C C bond cleavage that detach anthracene unit from the fluorophores resulting in strong fluorescence enhancement. These probes exhibit high selectivity and sensitivity in detection and imaging of 1O2 in chemical and in living cells. Our approach makes it simple and flexible for development of reaction-based 1O2 fluorescent probes for broad application in chemical, biomedical, and environmental sciences.

In the past decade, halogen bonding (XB) has been utilized extensively in the design of novel materials and new drugs. One of the emerging applications of XB is in devising organic room-temperature phosphorescent materials. Several reports showed that the use of benzaldehyde-based phosphors with appropriate XB donors results in high phosphorescence quantum yields because of enhanced intersystem crossing (kISC) and phosphorescence (kPH) rates. It is often advocated that a combination of factors, namely, rigidification, heavy-atom effect, and reduction of quenching by triplet dioxygen, is responsible for the enhancement. However, to what extent each factor contributes to the enhancement is unknown. In this study, we performed ab initio excited-state calculations on two XB complexes, benzaldehyde···XF (X = Br and I), with varying XB distance to elucidate the effect of XB on kISC and kPH. Our results show that XB reduces the kISC of benzaldehyde and changes the character of T1 from which phosphorescence takes...

Selenofunctionalization is used for the introduction of aryl- or alkylseleno moieties, which can then be transformed into other functional groups (such as alkenes and carbonyls). However, asymmetric selenofunctionalization of unactivated olefins is often difficult to realize, as aryl- and alkylseleno cations rapidly interchange between olefinic partners. Recently, it has been demonstrated that Lewis bases, assisted by Bronsted acids, induce high levels of enantioselectivity in selenocyclization reactions. The Bronsted acid serves as an activator for the reaction. In this work, we demonstrate an asymmetric selenoetherification and desymmetrization of olefinic 1,3-diols, driven by a unique chiral pairing between a C2-symmetric cyclic selenide catalyst and a chiral Bronsted acid. The resulting substituted tetrahydrofurans contain a phenylselenoether handle and can be transformed into synthetically useful building blocks. A series of experimental and computational investigations suggest that the reaction proc...

We discovered a reaction between 1,8-pyrenedione and N,N′-dialkylethylenediamine to form highly fluorescent products, via aza-Michael addition followed by double C–H activation facilitated by visible light. Remarkably, the reaction intermediates and mono C–H bond activation product could only be formed when the reaction was carried out in the presence of a base and UV-light (254 nm). Dehydrogenation of the intermediate under room lighting converts it to the final products. The reaction is a general one as it works with a number of ethyleneamines with different substituents with a (N)–CHn (n = 1, 2) linkage. The reaction mechanisms suggested that nucleophilic addition of the amine followed by dehydrogenation occurs to restore aromaticity and give an amine substituted 1,8-pyrenedione intermediate. The C–H activation requires photoexcitation via a radical mechanism. Our work opens a new avenue for the construction of novel molecules with a pyrene core as a fluorophore with good quantum yields.