Donor-acceptor Properties Research Articles

Physicochemical Characterization of Gallstone Surfaces to Predict Their Interaction with Salmonella Typhi.

Salmonella Typhi can adhere to and build biofilms on the surface of gallstones causing abnormal gallbladder mucosa, which could lead to carcinogenesis. The surface physicochemical properties of microbial cells and materials have been shown to play a crucial role in adhesion. Therefore, the purpose of this study was to investigate, for the first time, the surface properties of nine gallstones and to evaluate the influence of these parameters on the theoretical adhesion of S. Typhi to gallstone surfaces. The physicochemical properties were determined by SEM-EDX and contact angle measurements (CAM) while the predictive adhesion of S. Typhi on gallstones was estimated using the XDLVO approach. SEM-EDX analysis revealed that cholesterol is the principal component on the surface of all gallstones, with carbon and oxygen as the main elements. Aluminum was detected as a trace element in only three gallstones: GS2, GS4, and GS5. S. Typhi CIP5535 has a hydrophilic character (ΔGiwi = 33.54mJm-2), as well as strong electron donor (γ- = 55,80mJ m-2) and weak electron acceptor properties (γ+ = 1,95mJ m-2). Regarding gallstones, it was found that they have a hydrophobic character (ΔGiwi between -29,9mJm-2 and -75,2mJ m-2), while their electron donor/acceptor characters change according to each gallstone. Predictive adhesion showed that all gallstones could be colonized by S. Typhi except GS1, GS5, and GS6 . Understanding the interfacial phenomena implicated in the process of bacterial adhesion makes it possible to limit or even inhibit the adhesion of S. Typhi on gallstone surfaces.

Thermodynamic Description of Oxotransfer Processes Involving Molybdenum and Tungsten Enzyme Models: DFT Calculations and Calorimetry.

The enthalpy of the oxotransfer reaction of [Bu4N]2[WO2(mnt)2] (where mnt2- is maleonitriledithiolate) with PPh3 in an inert atmosphere in an acetonitrile solution was determined by calorimetry. The obtained enthalpy value (-93 ± 5) kJ mol-1 differs from the enthalpy value of the reaction carried out by us earlier under aerobic conditions by (16 ± 9) kJ mol-1. The obtained results indicate the participation of atmospheric oxygen in the catalytic process. DFT calculations of the structures [MOx(LL)2]2- (where M = Mo or W, x = 1 or 2, and LL is dithiolene ligand) were carried out. DFT calculations of the thermodynamic potential values for the oxygen transfer reaction in the system [MIVO2(LL)2]2- - [MVIO(LL)2]2- were also carried out. It was shown that the determining contribution to these processes is made by the enthalpy changes. The enthalpies of these processes depend on the donor-acceptor characteristics of the dithiolene ligands. In the case of good acceptors, the oxidation process is more exothermic. The opposite picture is observed for the reduction processes of the complex. The M═O bond length can be used as a quantitative criterion for donor-acceptor properties of the ligands. Also, for molybdenum complexes, reduction processes are more favorable, while for tungsten complexes, oxidation processes are more favorable. The calculations agree well with experimental data that prove the validity of the model used for DFT calculations.

Manifestation of Donor-Acceptor Properties of N-Doped Polymer Carbon Dots During Hydrogen Bonds Formation in Different Solvents.

The effective use of polymer carbon dots (PCD) in various fields of science and technology requires a more detailed understanding of the mechanisms of their photoluminescence formation and change as a result of their interaction with the environment. In this study, PCD synthesized via a hydrothermal method from citric acid and ethylenediamine are studied in various solvents using FTIR spectroscopy, optical absorption spectroscopy, and photoluminescence spectroscopy. As a result of the analysis of the obtained dependencies of such PCD spectral characteristics as the photoluminescence FWHM, the photoluminescence quantum yield, the photoluminescence lifetime on the acidity and basicity of the solvent, a hypothesis was formulated on the formation mechanism of hydrogen bonds between the PCD surface groups and the molecules of the environment, and conclusions were made about the donor-acceptor nature of the synthesized PCD.

Core-Shell PLGA Nanoparticles: In Vitro Evaluation of System Integrity.

The objective of this study was to compare the properties of core-shell nanoparticles with a PLGA core and shells composed of different types of polymers, focusing on their structural integrity. The core PLGA nanoparticles were prepared either through a high-pressure homogenization-solvent evaporation technique or nanoprecipitation, using poloxamer 188 (P188), a copolymer of divinyl ether with maleic anhydride (DIVEMA), and human serum albumin (HSA) as the shell-forming polymers. The shells were formed through adsorption, interfacial embedding, or conjugation. For dual fluorescent labeling, the core- and shell-forming polymers were conjugated with Cyanine5, Cyanine3, and rhodamine B. The nanoparticles had negative zeta potentials and sizes ranging from 100 to 250 nm (measured using DLS) depending on the shell structure and preparation technique. The core-shell structure was confirmed using TEM and fluorescence spectroscopy, with the appearance of FRET phenomena due to the donor-acceptor properties of the labels. All of the shells enhanced the cellular uptake of the nanoparticles in Gl261 murine glioma cells. The integrity of the core-shell structures upon their incubation with the cells was evidenced by intracellular colocalization of the fluorescent labels according to the Manders' colocalization coefficients. This comprehensive approach may be useful for the selection of the optimal preparation method even at the early stages of the core-shell nanoparticle development.

Chiral Diselenophosphoric Acids for Ion Pair Catalysis: A Novel Approach to Enhance Both Proton Donating and Proton Accepting Properties.

The activation of poorly reactive substrates via strong chiral acids is a central topic in asymmetric ion pair catalysis these days. Despite highly successful scaffolds such as N-triflylphosphoramides, these catalysts either lack C2-symmetry or provide multiple H-bond acceptor sites, leading to lower ee values for certain reactions. We present BINOL-based diselenophosphoric acids (DSA) as an extremely promising alternative. Using an intertwined approach of synthesis and NMR studies, we developed a synthetic approach to DSA with up to 98 % NMR yield. The obtained acids provide both very high proton donor and proton acceptor properties, a bifunctionality, which is key to catalytic applications. Indeed, first reactivity test proved the much higher acidity of DSA and its ability to initiate Mukaiyama-Mannich reaction and protodesilylation of silyl ethers. Together with their C2-symmetry, the single donor and single acceptor situation, the decreased tendency of self-association, and the straightforward synthesis with potential 3,3'-substitution, the DSA provide all features ideal for the further development of ion pair catalysis.

Pyrene-Functionalized Nanoporous Covalent Organic Frameworks with a Donor–Acceptor Property for 2,4,6-Trinitrophenol Detection

Pyrene-Functionalized Nanoporous Covalent Organic Frameworks with a Donor–Acceptor Property for 2,4,6-Trinitrophenol Detection

Reactivity of amino acids and short peptide sequences: identifying bioactive compounds via DFT calculations.

Bioactive peptides are short amino acid sequences that play important roles in various physiological processes, including antioxidant and protective effects. These compounds can be obtained through protein hydrolysis and have a wide range of potential applications in a variety of areas. However, despite the potential of these compounds, more in-depth knowledge is still necessary to better understand details regarding their chemical reactivity and electronic properties. In this study, we used molecular modeling techniques to investigate the electronic structure of isolated amino acids (AA) and short peptide sequences. Details on the relative alignments between the frontier electronic levels, local chemical reactivity and donor-acceptor properties of the 20 primary amino acids and some di- and tripeptides were evaluated in the framework of the density functional theory (DFT). Our results suggest that the electronic properties of isolated amino acids can be used to interpret the reactivity of short sequences. We found that aromatic and charged amino acids, as well as Methionine, play a key role in determining the local reactivity of peptides, in agreement with experimental data. Our analyses also allowed us to identify the influence of the relative position of AA and terminations on the local reactivity of the sequences, which can guide experimental studies and help to propose/evaluate possible mechanisms of action. In summary, our data indicate that the position of active sites of polypeptides can be predicted from short sequences, providing a promising strategy for the synthesis and bioprospection of new optimized compounds.

The Nitro Group Reshapes the Effects of Pyrido[3,4-g]quinazoline Derivatives on DYRK/CLK Activity and RNA Splicing in Glioblastoma Cells.

Serine-threonine protein kinases of the DYRK and CLK families regulate a variety of vital cellular functions. In particular, these enzymes phosphorylate proteins involved in pre-mRNA splicing. Targeting splicing with pharmacological DYRK/CLK inhibitors emerged as a promising anticancer strategy. Investigation of the pyrido[3,4-g]quinazoline scaffold led to the discovery of DYRK/CLK binders with differential potency against individual enzyme isoforms. Exploring the structure-activity relationship within this chemotype, we demonstrated that two structurally close compounds, pyrido[3,4-g]quinazoline-2,10-diamine 1 and 10-nitro pyrido[3,4-g]quinazoline-2-amine 2, differentially inhibited DYRK1-4 and CLK1-3 protein kinases in vitro. Unlike compound 1, compound 2 efficiently inhibited DYRK3 and CLK4 isoenzymes at nanomolar concentrations. Quantum chemical calculations, docking and molecular dynamic simulations of complexes of 1 and 2 with DYRK3 and CLK4 identified a dramatic difference in electron donor-acceptor properties critical for preferential interaction of 2 with these targets. Subsequent transcriptome and proteome analyses of patient-derived glioblastoma (GBM) neurospheres treated with 2 revealed that this compound impaired CLK4 interactions with spliceosomal proteins, thereby altering RNA splicing. Importantly, 2 affected the genes that perform critical functions for cancer cells including DNA damage response, p53 signaling and transcription. Altogether, these results provide a mechanistic basis for the therapeutic efficacy of 2 previously demonstrated in in vivo GBM models.

Strong donor-acceptor interaction of difluoroboron β-diketonates with polyvinylcarbazole: Deeply red-shifted emission of charge-transfer complexes and exciplexes

Donor-acceptor systems exhibiting exciplex luminescence attract much attention due to the wide prospects for their application in the field of OLEDs, nonlinear optics and lasers. Difluoroboron β-diketonates (BF2bdks) are a well-known class of organic dyes, which are able to form effective exciplex fluorescence, but this process has not received due attention for practical application. Strong donor-acceptor interaction in polyvinylcarbazole (donor) and BF2bdks derivatives (acceptor) binary system induces deeply red-shifted emission of charge-transfer complexes and exciplexes with a large bathochromic shift up to ∼170 nm relative to conventional monomeric luminescence. The results of quantum chemistry simulation are in agreement with the experiment data. Luminescence color tuning of the film are capable by the dye concentration, the donor-acceptor properties of the dye substituents and even the excitation wavelength. White light broad spectrum of a dual luminescence of the investigated binary systems has CIE chromaticity coordinates (0.35; 0.33) close to the standard neutral white light CIE coordinates (0.33; 0.33). This study will facilitate photophysical research and industrial applications of donor-acceptor binary systems based on polymer materials.

PhenTAA: A Redox-Active N4-Macrocyclic Ligand Featuring Donor and Acceptor Moieties.

Here, we present the development and characterization of the novel PhenTAA macrocycle as well as a series of [Ni(R2PhenTAA)]n complexes featuring two sites for ligand-centered redox-activity. These differ in the substituent R (R = H, Me, or Ph) and overall charge of the complex n (n = -2, -1, 0, +1, or +2). Electrochemical and spectroscopic techniques (CV, UV/vis-SEC, X-band EPR) reveal that all redox events of the [Ni(R2PhenTAA)] complexes are ligand-based, with accessible ligand charges of -2, -1, 0, +1, and +2. The o-phenylenediamide (OPD) group functions as the electron donor, while the imine moieties act as electron acceptors. The flanking o-aminobenzaldimine groups delocalize spin density in both the oxidized and reduced ligand states. The reduced complexes have different stabilities depending on the substituent R. For R = H, dimerization occurs upon reduction, whereas for R = Me/Ph, the reduced imine groups are stabilized. This also gives electrochemical access to a [Ni(R2PhenTAA)]2- species. DFT and TD-DFT calculations corroborate these findings and further illustrate the unique donor-acceptor properties of the respective OPD and imine moieties. The novel [Ni(R2PhenTAA)] complexes exhibit up to five different ligand-based oxidation states and are electrochemically stable in a range from -2.4 to +1.8 V for the Me/Ph complexes (vs Fc/Fc+).

Utilization of the through-space effect to design donor-acceptor systems of pyrrole, indole, isoindole, azulene and aniline.

Molecular electrostatic potential (MESP) topology analysis reveals the underlying phenomenon of the through-space effect (TSE), which imparts electron donor-acceptor properties to a wide range of chemical systems, including derivatives of pyrrole, indole, isoindole, azulene, and aniline. The TSE is inherent in pyrrole owing to the strong polarization of electron density (PoED) from the formally positively charged N-center to the C3C4 bonding region. The N → C3C4 directional nature of the TSE has been effectively employed to design molecules with high electronic polarization, such as bipyrroles, polypyrroles, phenyl pyrroles, multi-pyrrolyl systems and N-doped nanographenes. In core-expanded structures, the direction of electron flow from pyrrole units towards the core leads to highly electron-rich systems, while the opposite arrangement results in highly electron-deficient systems. Similarly, the MESP analysis reveals the presence of the TSE in azulene, indole, isoindole, and aniline. Oligomeric chains of these systems are designed in such a way that the direction of electron flow is consistent across each monomer, leading to substantial electronic polarization between the first and last monomer units. Notably, these designed systems exhibit strong donor-acceptor characteristics despite the absence of explicit donor and acceptor moieties, which is supported by FMO analysis, APT charge analysis, NMR data and λmax data. Among the systems studied, the TSEs of many experimentally known systems (bipyrroles, phenyl pyrroles, hexapyrrolylbenzene, octapyrrolylnaphthalene, decapyrrolylcorannulene, polyindoles, polyazulenes, etc.) are unraveled for the first time, while numerous new systems (polypyrroles, polyisoindoles, and amino-substituted benzene polymers) are predicted to be promising materials for the creation of donor-acceptor systems. These findings demonstrate the potential of the TSE in molecular design and provide new avenues for creating functional materials.

An intercalated covalent organic framework with donor-acceptor property for photothermal therapy

Based on the supramolecular assembly strategy, a donor-acceptor (D-A) covalent organic framework (COF) was developed by intercalating the electron-rich tetrathiafulvalene (TTF) between the layers of the COF which used 1,3,5-tris-(4-aminophenyl)triazine (TAPT) as an electron-deficient building unit. Due to the supramolecular D-A interactions, the obtained intercalated COF can efficiently convert luminous energy into thermal energy with a satisfying photothermal conversion efficiency up to 38.1 % for photothermal therapy. To further improve the biocompatibility and tumor targeting ability, the TTF-intercalated COF was coated with cancer cell membranes. In vitro and in vivo experiments demonstrated that the intercalated COF with D-A properties could effectively suppress the growth of tumors upon laser irradiation. This work provided a paradigm to feasibly construct D-A COF with promising photothermal performance for cancer treatment.

O,S-Acetals in a New Modification of oxo-Friedel–Crafts–Bradsher Cyclization—Synthesis of Fluorescent (Hetero)acenes and Mechanistic Considerations

This paper presents the use of O,S-acetals in a new modification of the oxo-Friedel-Crafts-Bradsher cyclization. In this reaction, under mild reaction conditions (25 °C), three- and four-ring fused RO-acenes (major) and/or HO(CH2)2S-acenes (minor) are formed, the latter products having never been observed before in this type of cyclization. In this way, two electronically different fluorophores could be obtained in a single cyclization reaction, one of them having strong electron donor properties (+M effect of alkoxy groups) and the other having donor-acceptor properties (+M and -I effects of the HO(CH2)2S-group, Hammett's constants). Further increasing the reaction temperature, HCl concentration or prolonging reaction time, surprisingly, yielded a 2:1 mixture of cis and trans dimeric isomers, as the only products of this cyclization. The DFT calculations confirmed a greater stability of the cis isomer compared to the trans isomer. The formation of unexpected dimeric products and HO(CH2)2S-acenes sheds light on the mechanism of oxo-Friedel-Crafts-Bradsher cyclization, involving competitive O/S atom protonation in strained O,S-acetals and in strain-free side groups of intermediate species.

Photocatalytic CO2 reduction with aminoanthraquinone organic dyes

The direct utilization of solar energy to convert CO2 into renewable chemicals remains a challenge. One essential difficulty is the development of efficient and inexpensive light-absorbers. Here we show a series of aminoanthraquinone organic dyes to promote the efficiency for visible light-driven CO2 reduction to CO when coupled with an Fe porphyrin catalyst. Importantly, high turnover numbers can be obtained for both the photosensitizer and the catalyst, which has not been achieved in current light-driven systems. Structure-function study performed with substituents having distinct electronic effects reveals that the built-in donor-acceptor property of the photosensitizer significantly promotes the photocatalytic activity. We anticipate this study gives insight into the continued development of advanced photocatalysts for solar energy conversion.

Adsorption of Organic Compounds on the Surfaces of Silicas with Grafted Acetoacet Ether Groups Saturated with Transition Metal Ions

A set of physicochemical means is used to study the adsorption properties of surfaces of silicas based on Silochrome C-120 with surface-grafted groups of acetoacetic ester saturated with transition metal ions. Gas chromatography is used to study the effect nickel, cobalt, and copper ethylacetoacetates have on the thermodynamic characteristics of adsorption (TCA) of different classes of organic substances on SiO2. Experimental data on the retention of adsorbates with different donor-acceptor properties (n-alkanes and chloroalkanes, alkenes, aromatic and oxygen-containing substances) are used to calculate differential molar heats of adsorption q¯dif,1 the change in the standard differential molar entropy ΔS¯S1,C and deposits Δq¯dif,1(spec) in the energy of dispersion and specific interactions.

Effect of void-carbon on blue-shifted luminescence in TADF molecules by theoretical simulations.

Thermally activated delayed fluorescence (TADF) molecules have a theoretical 100% photoluminescence quantum yield in comparison with traditional fluorescent materials, leading to broad application in organic light-emitting diode (OLED). However, the application of TADF molecules with conjugated donor-acceptor structures in blue OLED remains a challenge due to their generally narrow energy gap between frontier molecular orbitals. Recently, a strategy has been approved in the improvement of the performance in TADF, in which void-carbon atoms between donor and acceptor fragments (donor-void-acceptor (D-v-A)) could regulate blue light emission. In this study, we first select three reported isomers followed by two proposed D-v-A TADF isomers to verify the feasibility of the void-carbon strategy through evaluation of the electronic structures in the excited state and photophysical properties. We further proposed a series of TADF molecules by replacing different donor and acceptor fragments to assess the applicability of the void-carbon strategy from the aspect of simulations in electronic structures, different properties of donor and acceptor fragments, photophysical properties, and analysis in the molecular conjugation. The results indicate that void-carbon strategy has conditional feasibility and applicability. Donor-acceptor molecular properties could be tuned through void-carbon strategy on aromatic acceptor fragments during the selection of promising candidates of TADF molecules. However, the void-carbon strategy does not work for the molecules with antiaromatic acceptor fragments, where the steric hindrance of the molecules plays a dominant role. Our work provides insightful guidance for the design of the blue-emission TADF molecules.

Reversible Supramolecular Noncovalent Self-Assembly Determines the Optical Properties and the Formation of Melanin-like Nanoparticles.

The role of noncovalent supramolecular self-assembly in the formation of melanin-like NP, as well as the nature of the electronic transition at the basis of their unique optical properties, is strongly debated. Here we demonstrate that, during the first stage of formation of synthetic melanin, polydopamine (PDA), a small fraction of the molecular precursor dopamine (DA) is oxidized to quinone (Q) and a simple supramolecular charge-transfer (CT) adduct is formed thanks to the electron donor and electron acceptor properties of DA and Q, respectively. This adduct, also detectable by HPLC-MS, presents the broad absorption band in the red-NIR region typical of melanin-like materials. Importantly, its disaggregation upon dilution can be easily detected since it leads to the disappearance of the CT band, indicating the reversibility of the process. Moreover, the stability constant K of the CT adduct could be obtained using a simple association model.

Solvothermal synthesis of donor-acceptor covalent organic framework/coal-based polyaniline composites for three-state electrochromic materials

Conjugated covalent organic frameworks (COFs) with redox activity can be designed for photoelectric materials application. In this paper, COF based electrochromic films were synthesized by solvothermal method in a Teflon-lined reactor, with thieno [3,2-b]thiophene-2,5-dicarbaldehyde (TTDA) as electron donor unit (D) and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TTA) as electron acceptor unit (A) (COF TT ). Coal-based polyaniline (CPANI) was used as COF TT growth substrate and conductive enhancing agent to improve the photoelectric performance of COF TT . The addition of CPANI results in the morphology transformation of COF TT from nanosheet to nanofiber. Meanwhile, the impedance of COF TT is reduced and the optical contrast is improved. The color of COF TT -CPANI-1 can vary from yellow to dark orange and brown under a voltage window of −3 V–2.2 V. Stability tests show that the contrast retention rate of the electrochromic device is 90.6% after 1600 s switching. Considering the rich selectivity of COF construction units and the designability of topological structure, the development of COF-based electrochromic materials with rich colors and excellent properties has a broad prospect. • A COF electrochromic film was prepared by solvothermal method. • The morphology and photoelectrical properties of COF films was changed by the addition of coal-based polyaniline. • Due to the donor-acceptor properties of the synthesis unit, the COF film presents a three-state electrochromic behavior.

Integrating benzofuran and heteroradialene into donor-acceptor covalent organic frameworks for photocatalytic construction of multi-substituted olefins

Covalent organic framework (COF) is a novel platform to develop efficient and green safe heterogeneous photocatalysts. Additionally, multiple photoredox reactions and mechanism studies over porous catalysts remain to be further exploited. In this context, two benzofuran-embedded COFs (BF-COFs) with favorable solvent tolerance were constructed via tautomerism strategy. Attributing to the benzofuran-hetero[6]radialene knots, BF-COFs displayed as donor-acceptor properties, and exhibited wide visible light response range and well separation efficiency for photogenerated charges. Under visible-light, BF-COFs could promote the C-S bond formation reaction between β-ketoate ester and its analogues with NH4SCN, affording multi-substituted olefins (28 examples, upto 98% yield) efficiently. Moreover, the atomic economic strategy was also applicative to prepare L-proline derived olefins (≥ 99% ee), which could be further converted into the chiral amino-substituted thiazoles (99% yield and ≥ 99% ee). The research about BF-COFs sheds light on the green construction of C-S bond, (chiral) olefins and chiral amino thiazoles.

An environmentally friendly formulation based on Cannabis sativa L. seed oil for corrosion inhibition of E24 steel in HCl medium: Experimental and theoretical study

The poor corrosion resistance of carbon steel (CS) has long been an urgent challenge to its industrial applications. Green corrosion inhibitors are among the most widely used and economically viable methods to protect metals and alloys against corrosion. In the present work, a new green corrosion inhibitor formulation (CIF) based on Cannabis sativa L. seed oil (noted CSL) was prepared for protecting E24 carbon steel against corrosion in 1.0 mol/L HCl. Experiments were carried out using weight loss (WL), and electrochemical methods at different concentrations of CSL and immersion times. The surface morphology of corroded and inhibited CS was investigated using the scanning electron microscope (SEM), while Density Functional Theory (DFT) and molecular dynamics (MD) simulation were used to assess the reactivity of CSL’s components and their interactions with Fe(110) plane. The gas chromatographic analysis of the CSL indicated that the Linoleic acid (C18:2) is the most abundant fatty acid (51.3%), followed by Oleic acid ((C18:1) (20.3%)), α-Linolenic acid (C18:3 (15.7%)) and saturated Palmitic acid (C16:0 (7.9%)). According to WL and electrochemical results, an inhibition efficiency of over 92% was achieved using 1 g/L of CSL, indicating higher corrosion mitigation properties. Electrochemical results revealed that the tested formulation had a mixed-type inhibition effect, with a cathodic predominance. In addition, the charge transfer resistance of the CS electrode increased from 46 Ω cm2 in blank solution to 1115 Ω cm2 in HCl solution inhibited with 1 g/L of CSL and 24 h immersion. SEM images showed the formation of a protective barrier on CS surface, which prevented the corrosion attack. DFT and MD studies showed that CSL’s components have excellent donor-acceptor properties and exhibited a close contact with Fe(110) surface upon adsorption.