Position Of Substituents Research Articles

On the Notation of Catastrophes in the Framework of Bonding Evolution Theory: Case of Normal and Inverse Electron Demand Diels-Alder Reactions.

This paper generalizes very recent and unexpected findings [J. Phys. Chem. A, 2021, 125, 5152-5165] regarding the known "direct- and inverse-electron demand" Diels-Alder mechanisms. Application of bonding evolution theory indicates that the key electron rearrangement associated with significant chemical events (e. g., the breaking/forming processes of bonds) can be characterized via the simplest fold polynomial. For the CC bond formation, neither substituent position nor the type of electronic demand induces a measurable cusp-type signature. As opposed to the case of [4+2] cycloaddition between 1,3-butadiene and ethylene, where the two new CC single bonds occur beyond the transition state (TS) in the activated cases, the first CC bond occurs in the domain of structural stability featuring the TS, whereas the second one remains located in the deactivation path connecting the TS with the cycloadduct.

Effect of the phenyl substituent’s position on the encapsulation of porphyrins inside lignin nanoparticles: Photophysical and antibacterial properties

Porphyrins are well studied molecules that are widely used in Photodynamic Therapy, aiming for the eradication of tumours, but also for the eradication of bacteria. The formulation of porphyrins is a crucial factor when developing photodynamic applications, due to the limited stability and low solubility of porphyrins in aqueous media. Our research group has previously demonstrated that porphyrins, and especially 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin are easily encapsulated inside acetylated lignin spherical nanoparticles, while conserving their main photophysical features. In the present study we encapsulated 5,10,15,20-tetrakis(3-hydroxyphenyl)porphyrin, the precursor of the well-known photosensitizer Temoporfin, in acetylated lignin nanoparticles, yielding a stable formulation while keeping the photophysical properties of the encapsulated porphyrin. This formulation was tested as a photodynamic antibacterial agent against Staphylococcus aureus CIP 76.25 and Escherichia coli CIP 53.126, where it efficiently eradicated S. aureus, although also showing non-neglectable dark toxicity against the bacterial cells. In conclusion, the 3-hydroxyphenyl substituted porphyrin yielded nanoparticles physically and photophysically similar to those prepared with its isomer. However, the change in the position of the phenyl substituent seems to increase the dark toxicity of the nanoparticles, a phenomenon that still needs to be explored.

A combined QTAIM/IRI topological analysis of the effect of axial/equatorial positions of NH2 and CN substituents in the [(PY5Me2)MoO]+ complex

By means of the Interaction Region Indicator (IRI) and Quantum Theory of Atoms in Molecules (QTAIM), the influence exerted by NH2 (amino) and CN (cyano) as electron donor and electron acceptor substituent groups, respectively, located at para–positions of axial and equatorial pyridine rings of derivatized complexes coming from the [(PY5Me2)MoO]+ complex during the hydrogen molecular release in the gas phase was analyzed. In any case, a H–H covalent bond is forming at the transition state, with a strengthening of the electron density of 5.5% when the substituent group involved is NH2 at the para–position of the axial pyridine ring. However, there was no difference between NH2 and CN when these substituent groups are located at the para–positions of the equatorial pyridine rings. The topological properties of electron densities from the QTAIM are not perturbed by the electron donor and electron acceptor nature of the substituents, even when these substituent groups are located at the axial or equatorial pyridine rings of the Mo–based complex.

Solution chemical properties and anticancer potential of 8-hydroxyquinoline hydrazones and their oxidovanadium(IV) complexes

We report the synthesis and characterization of a family of benzohydrazones (Ln, n = 1–6) derived from 2-carbaldehyde-8-hydroxyquinoline and benzylhydrazides containing different substituents in the para position. Their oxidovanadium(IV) complexes were prepared and compounds with 1:1 and 1:2 metal-to-ligand stoichiometry were obtained. All compounds were characterized by elemental analyses and mass spectrometry as well as FTIR, UV–visible absorption, NMR (ligand precursors) and EPR (complexes) spectroscopies, and by DFT computational methods. Proton dissociation constants, lipophilicity and solubility in aqueous media were determined for all ligand precursors. Complex formation with V(IV)O was evaluated by spectrophotometry for L4 (Me-substituted) and L6 (OH-substituted) and formation constants for mono [VO(HL)]+, [VO(L)] and bis [VO(HL)2], [VO(HL)(L)]−, [VO(L)2]2− complexes were determined. EPR spectroscopy indicates the formation of [VO(HL)]+ and [VO(HL)2], with this latter being the major species at the physiological pH. Noteworthy, the EPR data suggest a different behaviour for L4 and L6, which confirm the results obtained in the solid state. The antiproliferative activity of all compounds was evaluated in malignant melanoma (A-375) and lung (A-549) cancer cells. All complexes show much higher activity on A-375 (IC50 < 6.3 μM) than in A-549 cells (IC50 > 20 μM). Complex 3 (F-substituted) shows the lowest IC50 on both cell lines and lower than cisplatin (in A-375). Studies identified this compound as the one showing the highest increase in Annexin-V staining, caspase activity and induction of double stranded breaks, corroborating the cytotoxicity results. The mechanism of action of the complexes involves reactive oxygen species (ROS) induced DNA damage, and cell death by apoptosis.

Asymmetric Tris-Heteroleptic Cyclometalated Phosphorescent Iridium(III) Complexes: An Emerging Class of Metallophosphors

ConspectusThe rapid developments of cutting-edge research on photofunctional organic semiconductor materials are greatly promoting the progress of science and technology. As one of the most important organic semiconductor materials, phosphorescent iridium(III) complexes are a promising class of organometallic emitters because of their rich emissive excited states together with excellent chemical stability, which have been widely used in various fields, such as organic electroluminescence, solar cells, photocatalysis, biosensing, bioimaging, cancer therapy, etc. The exploration of highly efficient phosphorescent iridium(III) complexes showing various structural features is blooming quickly. In general, the traditional iridium(III) phosphors usually contain at least two identical cyclometalating bidentate ligands. These iridophosphors with two identical bidentate ligands are termed as the bis-heteroleptic complex Ir((L1)2L2), where L denotes the free ligand or the deprotonated form of the free ligand. Those with three identical ligands are called homoleptic complex Ir(L)3. Recently, the iridium(III) complexes Ir(L1L2L3) supported by three different (cyclometalating) ligands are emerging as a novel and interesting category of phosphors. This class of iridophosphors usually refers to tris-heteroleptic cyclometalated phosphorescent iridium(III) complexes, and they usually show the asymmetry in their molecular structures. Compared with the case for the traditional iridium(III) phosphors, the independent ligand control provides tris-heteroleptic iridium(III) phosphors with more flexible molecular design/synthesis and excited-state fine-tuning ability, thereby resulting in more rich and appealing excited states and potential multifunctional applications.In this Account, we will highlight our recent efforts on the asymmetric tris-heteroleptic cyclometalated iridium(III) phosphors including the molecular design strategies, chemical synthesis, excited-state tuning, and structure–property relationships as well as their applications, especially in organic electroluminescence. Specifically, the molecular design of tris-heteroleptic iridium(III) phosphors focuses on the independent ligand design including the following three aspects: (1) the substituent functionalization engineering (SFE); (2) the ligand skeleton engineering (LSE); (3) the double metalation engineering (DME). For SFE, we mainly introduce the substituent based on the main-group element into the ligand of iridophosphors and also investigate the influence of the substituent position on the emissive excited states of iridophosphors. For instance, the main-group elements show unique electronic effects, which could contribute to the manipulation of the photoelectric properties of complexes (e.g., balanced charge transport ability, improved utilization of excitons, etc.). For LSE, different types of aromatic skeleton or various lengths of π conjugation of the ligands are also examined for the effective tuning of their excited states. For DME, the type and spatial orientation of the bridging/franking ligand will be considered. At the same time, the related optoelectronic applications (e.g., electroluminescence, optical power limiting, etc.) of this novel class of versatile iridophosphors are also discussed. Finally, we give some perspectives on this fascinating topic and also try to provide some potential research opportunities based on the current stage of asymmetric tris-heteroleptic cyclometalated phosphorescent iridium(III) complexes. It is believed that the emerging asymmetric tris-heteroleptic cyclometalated iridophosphors will open an important avenue for designing novel metallophosphor-based materials with tunable and appealing photophysical properties, thus offering new probabilities for potential multifunctional applications.

Thermal stability limits of imidazolium, piperidinium, pyridinium, and pyrrolidinium ionic liquids immobilized on metal oxides

Twenty-nine different ionic liquids (ILs) consisting of imidazolium, pyridinium, piperidinium, and pyrrolidinium cations and I–, Cl–, Br–, PF6–, BF4–, [DCA]–, and [NTf2]– anions were immobilized on MgO and SiO2. Their short-term thermal stability limits were investigated by thermogravimetric analysis and compared with those of the corresponding bulk ILs. Data showed that the thermal stability limits of ILs change significantly when the ILs are immobilized on metal oxides. These changes were evaluated based on the structural interactions determined by infrared (IR) spectroscopy. Systematic structural differences were considered to investigate the factors affecting the thermal stability of bulk ILs, and their counterparts immobilized on MgO and SiO2. These structural changes were the change in the alkyl chain length, the methylation on C2 site in imidazolium ILs, the change in substituent position in the pyridinium ring, the change in the anion, and the change in the IL family. The strongest factor controlling the thermal stability limits of both bulk ILs and their supported counterparts was determined as the anion type. Accordingly, the basicity of the anion and the surface acidity of the metal oxide and their resulting interactions were found to have a significant effect on the thermal stability limits. Data presented here offer the opportunity to pick a suitable anion and cation pair according to the metal oxide, so that the supported IL can withstand the desired operation conditions in various applications, such as catalysis or gas separation.

Influence of derivatives of 2-((6-r-quinolin-4-yl)thio)acetic acid on rhizogenesis of Paulownia clones

In recent years, the demand for effective and low-toxic stimulators of rhizogenesis, which are used in microclonal propagation of plants, has been increasing in Ukraine. One of the promising directions in the search for effective compounds is molecular modeling based on known natural and synthetic compounds. The development of new highly effective and low-toxic biologically active compounds is largely based on derivatives of nitrogen-containing heterocycles, and quinoline occupies a significant place among them. Modern methods of chemometric analysis make it possible to find certain regularities in the "chemical structure – biological activity" and to select the most promising compounds for experimental research. The values of lipophilicity log P for neutral forms and the value of the distribution coefficient log D at pH = 7 were obtained by quantum chemical calculation. The values of log P and log D of the studied compounds are in the most favourable interval for overcoming the biological membranes of the cells of the root system, depending on the pH of the environment. According to Lipinski’s "rule of five", all studied compounds can show high biological activity. The toxicity of compounds of 2-((6-R-quinolin-4-yl)thio)acetic acid derivatives was evaluated by computer programs and experimentally. Among the derivatives of 2-((6-R-quinolin-4-yl)thio)acetic acid, the most toxic compounds were those that did not have alkoxy substituents in the 6th position of the quinoline ring. Sodium salts are more toxic than the corresponding acids. This is due to an increase in the bioavailability of ionized compounds. Derivatives of 2-((6-R-quinolin-4-yl)thio)acetic acid (sodium salt of 2-((quinolin-4-yl)thio)acetic acid (QAC-5) showed the greatest toxic effect on the model of the study of progressive sperm motility) and 2-((quinolin-4-yl)thio)acetic acid (QAC-1), which will reduce this indicator by 15–20% compared to intact. The toxicity assessment of the studied compounds made it possible to determine a number of factors of the structure of molecules which affect the level of toxic action of 2-((6-R-quinolin-4-yl)thio)acetic acid derivatives and the directions of creation of non-toxic growth stimulants in this series. The impact on rhizogenesis during microclonal reproduction in vitro in explants Paulownia clone 112 and further adaptation of microplants in vivo hybrid molecules of quinoline and acetic acid, which are analogues of known growth stimulants, was studied. A number of factors influencing the level of influence on rhizogenesis of the action of derivatives of 2-((6-R-quinolin-4- yl)thio)acetic acid and directions of creation of highly active substances in this series was defined. The studied compounds showed a high stimulating effect on rhizogenesis in vitro in Paulownia explants. It was established that the sodium salt of 2-((quinolin-4-yl)thio)acetic acid was the greatest stimulator of rhizogenesis compared to the corresponding original acid. The presence of alkoxy groups in the 6th position and methyl in the 2nd position of the quinoline ring of 2-((6-R-quinolin-4-yl)thio)acetic acid reduced the activity of the compounds. The selection of new effective, low-toxic, less expensive substances was carried out for further testing as potential stimulators of rhizogenesis for microclonal propagation of plants.

Photo-Spectro-Electrochemical Properties of Phospholes – Promising Molecules for Organic Electronics

Pentasubstituted phospholes with extended p-conjugated arms in positions 1,2 and 5 were synthesized using a new procedure1 and characterized electrochemically and by UV-vis and EPR spectra. Quantum chemical calculations of redox potentials and HOMO-LUMO energies were performed and experimental and theoretical data were successfully correlated. Tuning of redox properties can be achieved by combination of induction and resonance effects of substituents, extension / diminution of the p- delocalized system and by steric changes which affect intramolecular electron communication.These non planar five-membered heterocycles have tri-coordinated phosphorus atom with a non-bonding electron pair. In the series of analogous heterocycles like pyrrol, thiophene and furan, phosphole exhibits lowest aromaticity and therefore it behaves rather like a diene 2,3. Thanks to specific sterical and "push-pull" properties resulting from combination of electron withdrawing and electron donating substituents, phospholes are considered as promising material for organic electronics with application e.g. in solar cells, organic light-emitting diodes (OLEDs) or as fluorescent probes.4,5 The studied derivatives are substituted asymmetrically (two para-extended aryl substituents in positions 1,2 and a different one in position 5), whereas in the positions 3 and 4 are methyl groups. The aryl in the position 1 is perfectly perpendicular to the plane of the heterocycle, therefore this substituent is completely electronically isolated. On the other hand, the two aromates in the positions 2 and 5 are partly twisted, therefore some π-overlap with the heterocycle is preserved.In this contribution6 we focus on the first oxidation and the first reduction potentials and their difference, which we call "electrochemical gap" (as an analogy to HOMO-LUMO gap). This value is related to electron delocalization and also to the push-pull abilities of substituents and, in this way, electrochemistry can be interconnected with photochemistry and light absorption or emission.All first reduction and oxidation potentials are reversible or quasi-reversible, therefore they are thermodynamically relevant and thus suitable for correlation with quantum chemical calculations.Based on their structure and fundamental electrochemical, spectroscopic and computational characterization, the new compounds could be arranged into several individual homologous „series“, where influence of substituents and their position on a) reduction / oxidation potentials; b) changes and extent of electron delocalization; c) absorption / emission of light, was followed and evaluated. The understanding of the structure – properties relationship enables tuning of photo-redox qualities of the title molecules. Acknowledgement: The authors are grateful to the grant support from GAČR No. 18-12150 S and to the institutional support RVO 61388955. References Polák P., Čejka J., Tobrman T., Org. Lett., 22, 2187 (2020).Szűcs R., Bouit P.-A., Hissler M., Nyulászi L., Struct. Chem. 26, 1351 (2015).Charrier C., Bonnard H., De Lauzon G., Mathey F., J. Am. Chem. Soc. 105, 6871 (1983).Shameem M. A., Orthaber A., Chem. Eur. J. 22, 10718 2016).Duffy M. P., Delaunay W., Bouit P. A., Hissler M., Chem. Soc. Rev. 45, 5296 (2016).to be published

Влияние гетероциклических соединений ряда изоксазолона на рост и развитие проростков пшеницы (Triticum aestivum L.)

Arylidenisoxazolones have been known since the second half of the 20th century and still retain their relevance as biologically active compounds and the basis for further transformations. Biological testing of synthetic heterocyclic compounds – 4-arylidene-3-methylisoxazol-5-ones, which differ in nature, position and number of substituents in the aryl fragment, was carried out: 4-(4-methoxybenzylidene)-3-methylisoxazol-5-one, 4- (4-chlorobenzylidene)-3-methylisoxazol-5-one, 4-(4-dimethylaminobenzylidene)-3-methylisoxazol-5-one, 4-(4-hydroxy-3-methoxybenzylidene)- 3-methylisoxazol-5-one, 4-(3,4-dimethoxybenzylidene)-3-methylisoxazol-5-one. The compounds were obtained at the Department of Organic and Bioorganic Chemistry of the Saratov National Research State University named after N.G. Chernyshevsky in order to identify the relationship between structure and biological action. The paper presents the characteristics of the tested compounds and a modified method for the synthesis of arylidenisoxazolones. Seedlings of spring soft wheat Triticum aestivum L. cv. Saratovskaya 36 served as test objects. To assess the physiological activity of the tested compounds, we used the seed germination index, analysis of the morphometric data of the seedling, the root-to-shoot ratio and the root index. The inhibitory effect of some compounds on seed germination has been established. The most pronounced effect was manifested during seed germination in a solution of 4-(4-hydroxy-3-methoxybenzylidene)-3-methylisoxazol-5-one at a concentration of 10-7M. No significant effect of isoxazolone derivatives on the growth of the first leaf of the test object was found. All tested 4-arylidene-3-methylisoxazol- 5-ones had a stimulating effect on the growth of the root system in length. The direct nature of the dependence of this effect on the concentration of a solution of 4-(4-chlorobenzylidene)-3-methylisoxazol-5-one and 4-(3,4-dimethoxybenzylidene)-3-methylisoxazol-5-one was determined. A positive effect of the tested compounds on the root-to-shoot ratio of seedlings was revealed (with the exception of 4-(4-dimethylaminobenzylidene)- 3-methylisoxazol-5-one). The root index of seedlings was determined and it was found that the presence of methoxyl groups has an inhibitory effect on the value of this indicator. Based on the data obtained, it can be concluded that 4-(4-dimethylaminobenzylidene)-3-methylisoxazol-5-one and 4-(4-chlorobenzylidene)-3-methylisoxazol-5-one are promising compounds for further research.

Co‐assembled Monolayers as Hole‐Selective Contact for High‐Performance Inverted Perovskite Solar Cells with Optimized Recombination Loss and Long‐Term Stability

AbstractSelf‐assembled monolayers (SAMs) have been widely employed as an effective way to modify interfaces of electronic/optoelectronic devices. To achieve a good control of the growth and molecular functionality of SAMs, we develop a co‐assembled monolayer (co‐SAM) for obtaining efficient hole selection and suppressed recombination at the hole‐selective interface in inverted perovskite solar cells (PSCs). By engineering the position of methoxy substituents, an aligned energy level and favorable dipole moment can be obtained in our newly synthesized SAM, ((2,7‐dimethoxy‐9H‐carbazol‐9‐yl) methyl) phosphonic acid (DC‐PA). An alkyl ammonium containing SAM is co‐assembled to further optimize the surface functionalization and interaction with perovskite layer on top. A champion device with an excellent power conversion efficiency (PCE) of 23.59 % and improved device stability are achieved. This work demonstrates the advantage of using co‐SAM in improving performance and stability of PSCs.

Co-assembled Monolayers as Hole-Selective Contact for High-Performance Inverted Perovskite Solar Cells with Optimized Recombination Loss and Long-Term Stability.

Self-assembled monolayers (SAMs) have been widely employed as an effective way to modify interfaces of electronic/optoelectronic devices. To achieve a good control of the growth and molecular functionality of SAMs, we develop a co-assembled monolayer (co-SAM) for obtaining efficient hole selection and suppressed recombination at the hole-selective interface in inverted perovskite solar cells (PSCs). By engineering the position of methoxy substituents, an aligned energy level and favorable dipole moment can be obtained in our newly synthesized SAM, ((2,7-dimethoxy-9H-carbazol-9-yl) methyl) phosphonic acid (DC-PA). An alkyl ammonium containing SAM is co-assembled to further optimize the surface functionalization and interaction with perovskite layer on top. A champion device with an excellent power conversion efficiency (PCE) of 23.59 % and improved device stability are achieved. This work demonstrates the advantage of using co-SAM in improving performance and stability of PSCs.

Synthesis, Optical Characterization in Solution and Solid-State, and DFT Calculations of 3-Acetyl and 3-(1'-(2'-Phenylhydrazono)ethyl)-coumarin-(7)-substituted Derivatives.

Intramolecular charge transfer (ICT) effects are responsible for the photoluminescent properties of coumarins. Hence, optical properties with different applications can be obtained by ICT modulation. Herein, four 3-acetyl-2H-chromen-2-ones (1a–d) and their corresponding fluorescent hybrids 3- (phenylhydrazone)-chromen-2-ones (2a–d) were synthesized in 74–65% yields. The UV-Vis data were in the 295–428 nm range. The emission depends on the substituent in position C-7 bearing electron-donating groups. Compounds 1b–d showed good optical properties due to the D-π-A structural arrangement. In compounds 2a–d, there is a quenching effect of fluorescence in solution. However, in the solid, an increase is shown due to an aggregation-induced emission (AIE) effect given by the rotational restraints and stacking in the crystal. Computational calculations of the HOMO-LUMO orbitals indicate high absorbance and emission values of the molecules, and gap values represent the bathochromic effect and the electronic efficiency of the compounds. Compounds 1a–d and 2a–d are good candidates for optical applications, such as OLEDs, organic solar cells, or fluorescence markers.

Spectral and generation properties of new coumarins – benzopyrylium derivatives

The spectral and generation parameters of coumarins, benzopyrylium derivatives, in ethanol and acetonitrile under coherent excitation were studied. It was found that the absorption spectra of the investigated compounds contain several maxima and the structuredness of the spectra is associated with their bichromophoric structure. It is shown that these organic dyes are bichromophoric compounds. It is noted that the nature of the substituents in positions 6 and 7 of the coumarin base and positions 6′ and 7′ of the benzopyrylium core determines their spectral-luminescent and lasing properties. It is demonstrated that the presence of substituents in certain positions of the coumarin base and the benzopyrylium core changes the conformation of the molecule and, accordingly, the dipole moments and oscillator strengths of the transition. The generation ability of coumarins of this class manifests itself only in the presence of the strongest donor substituents (for example, Et2N and OH) in position 7, and sufficiently strong acceptors in positions 6′ and 7′. Lasing was obtained in the spectral region of 730 –740 nm on dyes – benzopyrylium derivatives.

Divergent Access to Polycyclic N-Heterocyclic Compounds through Büchner-Type Dearomatization Enabled Cycloisomerization of Diynamides under Gold Catalysis.

Catalytic dearomatization has been considered as a valuable approach to convert readily accessible flat molecules to products with three-dimensional frameworks. Herein, an unprecedented gold-catalyzed oxidative Büchner-type cyclopropanation is described that enables the cycloisomerization of diynamides. By variation of the position of substituents on the phenyl ring, a variety of fused N-heterocyclic products with challenging structural skeletons were obtained divergently.

Synthesis of Coumarin and Homoisoflavonoid Derivatives and Analogs: The Search for New Antifungal Agents.

A set of twenty-four synthetic derivatives, with coumarin and homoisoflavonoid cores and structural analogs, were submitted for evaluation of antifungal activity against various species of Candida. The broth microdilution test was used to determine the Minimum Inhibitory Concentration (MIC) of the compounds and to verify the possible antifungal action mechanisms. The synthetic derivatives were obtained using various reaction methods, and six new compounds were obtained. The structures of the synthesized products were characterized by FTIR spectroscopy: 1H-NMR, 13C-NMR, and HRMS. The coumarin derivative 8 presented the best antifungal profile, suggesting that the pentyloxy substituent at the C-7 position of coumarin ring could potentiate the bioactivity. Compound 8 was then evaluated against the biofilm of C. tropicalis ATCC 13803, which showed a statistically significant reduction in biofilm at concentrations of 0.268 µmol/mL and 0.067 µmol/mL, when compared to the growth control group. For a better understanding of their antifungal activity, compounds 8 and 21 were submitted to a study of the mode of action on the fungal cell wall and plasma membrane. It was observed that neither compound interacted directly with ergosterol present in the fungal plasma membrane or with the fungal cell wall. This suggests that their bioactivity was due to interaction involving other pharmacological targets. Compound 8 was also subjected to a molecular modeling study, which showed that its antifungal action mechanism occurred mainly through interference in the redox balance of the fungal cell, and by compromising the plasma membrane; not by direct interaction, but by interference in ergosterol synthesis. Another important finding was the antifungal capacity of homoisoflavonoids 23 and 24. Derivative 23 presented slightly higher antifungal activity, possibly due to the presence of the methoxyl substituent in the meta position in ring B.

Primary- and secondary-sphere effects of amine substituent position on rhenium bipyridine electrocatalysts for CO2 reduction

It is well-established that electrocatalysts with biologically inspired moieties provide advantageous qualities for the efficient transformation of fossil fuel combustion products, such as carbon dioxide, into value-added products. Herein, we present a family of Re(bpy)(CO)3Cl electrocatalysts with pendant NH2 groups in the 4,4′-, 5,5′-, and 6,6′-positions of the bipyridine backbone with the objective of determining the effects of combined primary- and secondary-sphere interactions on the reduction of CO2 to CO. Cyclic voltammetry studies under CO2 indicate that the catalytic onset potential is more positive for 6,6′-NH2-Re, indicating that proximity of the available pendant protons to the metal center is beneficial during catalysis. Controlled potential electrolysis studies demonstrate that, similar to 6,6′-NH2-Re, 4,4′-NH2-Re displays a dependence of Faradaic efficiency (FE) on catalytic potential, reaching a maximum FECO of 91% at −2.40 V. This FE is greater than that observed for 6,6′-NH2-Re but occurs at a more negative potential. Density functional theory (DFT) calculations were performed to compare the HOMO-LUMO gap of these complexes, and the following trend of 4,4′-NH2-Re > 6,6′-NH2-Re > 5,5′-NH2-Re was determined. Mulliken electron population analysis indicates a greater degree of electron density on the metal center for 6,6′-NH2-Re compared to its related congeners, in agreement with the electrolysis studies which illustrate a more favorable CO2 reduction for 6,6′-NH2-Re. Ultimately, it is important that the various catalytic parameters are properly balanced to provide the greatest overall catalytic activity.

Vacuum-deposited petroporphyrins: Effect of regioisomerism on film morphology

Petroporphyrins are geochemical marker molecules that could provide evidence for the biogenic origin of crude oil. Despite the standing interest in their properties, the structure of the condensed phase has not received due attention so far. Here we report on the optical absorption, microscopic structure and molecular ordering in thin vacuum-deposited films of four closely related compounds of petroporphyrin family (transition metal etioporphyrins) that differ either position of peripheral substituents or by the central metal atom. It is shown that even such minor alteration in the molecular architecture as regioisomerism results in remarkable distinctions in film morphology. The observed structural features can potentially be useful in organic electronics applications.

Synthesis of Benzofuran–based Schiff bases as anti-diabetic compounds and their molecular docking studies

Inhibition of α-glucosidase and α-amylase enzymes is one of the significant approaches in designing anti-diabetic drugs because of its role in decreasing the carbohydrate digestion. In the present study we designed a new series of benzofuran Schiff base and evaluated them for their inhibitory potentials against α-amylase and α-glucosidase enzymes. Compounds 1–22 exhibited a varying degree of inhibitory activity with IC50 value ranging from 1.10 ± 0.10 to 24.60 ± 0.70 µm for α-amylase and 1.40 ± 0.10 to 24.00 ± 0.70 µm for α-glucosidase when compared with the standard drug acarbose having an IC50 value of 11.50 ± 0.30 and 12.20 ± 0.30 µm for α-amylase and α-glucosidase respectively. The most potent analogue among the series was analogue 12 having IC50 value of 1.10 ± 0.10 µm for α-amylase and 1.40 ± 0.10 µm for α-glucosidase. Similarly, analogues 1, 8 and 19 were also identified as potent analogues having IC50 values of 2.20 ± 0.10, 2.10 ± 0.10 and 2.10 ± 0.10 for α-amylase and 2.70 ± 0.10,1.90 ± 0.10 and 2.50 ± 0.10 for α-glucosidase respectively. Analogues 11( = 4.70 ± 0.10, 4.40 ± 0.10), 17 (IC50 = 5.20 ± 0.10, 5.70 ± 0.10) and 22 ( = 4.80 ± 0.10, 4.50 ± 0.10) exhibited moderate inhibition. Structure-activity relationship (SAR) of this series has been established which is mainly based on the position and nature of substituent on phenyl ring. In order to analyze the mode of inhibition of these compounds docking studies were carried out. Binding mode analysis of the most active inhibitors showed that these are well accommodated into the binding site of enzyme.

A strategy integrating parent ions list-modified mass defect filtering-diagnostic product ions for rapid screening and systematic characterization of flavonoids in Scutellaria barbata using hybrid quadrupole-orbitrap high-resolution mass spectrometry

In this study, full scan (FS)-parent ions list (PIL)-higher energy collision induced dissociation (HCD)-MS/MS (FS-PIL-HCD-MS/MS) was used to acquire the chemical profile of flavonoids in Scutellaria barbata. Mass defect filtering (MDF) induced subtype classification and diagnostic product ions (DPIs) dominated structural confirmation were integrated into an effective strategy for the systematic screening and identification of the flavonoids. An in-house flavonoid MS database based on molecular design was established to construct a modified triangle MDF algorithm for progressive screening and subtype classification. The obtained results demonstrated that the modified MDF was capable of simplifying the workload in formula editing and subsequent screening process, and distinguishing different subtypes. The fragmentation behaviors of eleven reference standards were evaluated to obtain the MS2 fragmentation pathway and DPIs which can provide a criterion to eliminate false-positive results and judge the target flavonoids with the exact number and position of substituents for the first time. Structure confirmation was characterized by comparing with the reference substance, searching the database, and analyzing DPIs. To distinguish some isomers, ClogP (the calculated lipophilicity parameter) was adopted. As a result, 127 target flavonoids, including 30 flavone/flavonol aglycones, 10 flavanone/flavanonol aglycones, 49 flavone/flavonol monoglycosides, 16 flavanone/flavanonol monoglycosides, 21 flavone/flavonol diglycosides and 1 flavanone/flavanonol diglycoside, were ultimately identified or tentatively characterized based on the MS fragmentation pathway and DPIs analysis. This study provides a novel MDF method with improved subtype classification and develops a novel strategy for the progressive screening, subtype classification and systematic characterization of complex components in herbal medicines.

Palladium-Catalyzed One-Step Synthesis of Stereodefined Difunctionalized Glycals

Palladium-Catalyzed One-Step Synthesis of Stereodefined Difunctionalized Glycals