Acceptor Ability Research Articles

Nucleation of Insoluble Drugs in Solvents with Different Hydrogen Bond Donor and Acceptor Abilities─A Case Study of Probenecid

Nucleation of Insoluble Drugs in Solvents with Different Hydrogen Bond Donor and Acceptor Abilities─A Case Study of Probenecid

Design and synthesis of heterocycle-based push-pull NLOphores: A comprehensive study of their linear and non-linear optical properties

Push-pull chromophores, with strong intramolecular charge transfer (ICT), exhibit high ground-state polarization, driving strong NLO responses. The donor and acceptor abilities of the groups in the investigated compounds influence ICT, so the nonlinear response of these compounds was analyzed in relation to their strength. Two different families of NLOphores were synthesized through [2 + 2] cycloaddition-retroelectrocyclizations of heterocycle-based electron-rich alkynes with tetracyanoethylene (TCNE) and tetracyanoquinodimethane (TCNQ). The λmax values of push-pull chromophores, particularly for charge transfer bands, fall within the range of 424–758 nm. The linear and nonlinear optical properties of these NLOphores were subsequently examined through a combination of experimental and theoretical methods. NLO measurements were conducted using a validated custom-made Z-scan device. The nonlinear absorption coefficients range from −1.44 × 10−4 cm.W−1 to −9.90 × 10−4 cm.W−1, while nonlinear refractive indices range from −1.59 × 10−7 cm2. W−1 to −2.26 × 10−6 cm2. W−1. As expected from their molecular structures, the TCNQ products displayed stronger nonlinear responses than the TCNE products.

Enhanced Thermally Activated Delayed Fluorescence by Sole Coordination: From an Organic Molecule to Its Zinc Complex.

A BPAPTPyC organic molecule containing a sandwich structural chromophore is designed and synthesized to produce blue thermally activated delayed fluorescence (TADF). The chromophore is composed of two di(4-tert-butylphenyl)amino donors and one inserted terpyridyl acceptor hitched at positions 1, 8, and 9 of a single carbazole via the p-phenylene group, in which the multiple space π-π interactions between the donor and acceptor enable the molecule to possess the TADF feature with a high energy emission at 470 nm but a low photoluminescence quantum yield (PLQY) and a small proportion of the delayed component. In contrast, the corresponding Zn(BPAPTPyC)Cl2 complex has a high PLQY and a short lifetime with a red-shifted emission due to the enhanced rigidity and electron accepting ability of the terpyridyl group from coordination. A solution-processed organic light-emitting diode (OLED) based on the complex achieves a maximum external quantum efficiency (EQE) of 17.9% with an emission peak at 585 nm, while an OLED of the organic molecule produces blue emission with a maximum EQE of 2.7%.

Third-order nonlinear optical properties of phenothiazine-based imine covalent organic framework films

The manipulation of the chemical structure within covalent organic frameworks (COFs) is emerging as a potent approach to engineering materials with enhanced charge transfer efficiency and nonlinear optical (NLO) properties. This study introduces the synthesis of two donor-acceptor (D-A) COF films, PB-TZ and PT-TZ, via solvothermal processing, followed by a detailed examination of their third-order NLO characteristics. Notably, COF films demonstrated Saturation absorption and self-defocusing properties at a 532 nm laser irradiation, indicating their potential utility in optical applications. The third-order nonlinearly polarized magnetic induction (χ(3)) of the PT-TZ film is significantly higher compared with that of the PB-TZ film, reaching 16.05 ± 0.17 × 10−7 esu, which is 2.9 times higher than that of the PB-TZ film. This enhancement can be attributed to the superior acceptor ability of the triazine ring within PT-TZ, which promotes a more efficient electron transfer from the donor to the acceptor units. Consequently, this study provides a new idea for the development of COF films in the field of high-performance NLO.

N‒N hydrazonyl bond cleavage in benzothiazolyl-hydrazino-phenathrenequinone mediated by ruthenium(II) via an anion radical intermediate

The complexes [Ru(LBenz)H(CO)(PPh3)2] 2, [Ru(LBenz)Cl(CO)(PPh3)2] 3, (ligand behaving as bidentate monoanionic) and [Ru(LBenz)Cl(CO)(PPh3)] 4, (ligand is tridentate monoanionic) have been synthesized starting from benzothiazolyl-hydrazino-phenathrenequinone (HL) 1 and [RuH(CO)Cl(PPh3)3]. These are characterized by electrochemical and spectral methods as well as single crystal X-ray diffractometry (SCXRD). Upon treating with NaBH4, 3 accepts an electron within the coordinated ligand framework and the anionic hydrazonyl-N takes up a proton to be transformed to meta-stable hydrazinoquinone anion radical complex of ruthenium(II) [Ru(HLBenz•‒)Cl(CO)(PPh3)2] 5, possibly via concerted proton electron transfer process (CPET). Thus, the redox non-innocent character of the ligand upon complexation with ruthenium(II), has been disclosed and it is attributed to presence of low lying π* orbitals of almost entirely of phenanthraquinone and hydrazone character. In 5, the π‒acceptor ability of the ligand donor centres are reduced due to the existence of an odd electron in SOMO and hence the M-L distances around the coordination sphere are altered. The N‒N (hydrazonyl bond length increases from 1.296(6) Å in 3 to 1.429 Å in 5, leading to lesser thermodynamic stability of the latter and upon standing, the N‒N bond is cleaved to be transformed to 6+, possibly via the formation of iminoquinone anion radical complex, [6] (reported elsewhere). Also, it is via the dissociation of N‒N (hydrazonyl) bond, the biologically important molecule 2-aminobenzothiazole is formed along with 6+, so as to provide a novel route for its synthesis.

Understanding Bonding Nature of α‐Keggin Polyoxometalates [XW12O40]n− (X = Al, Si, P, S): A Generalized Superatomic Perspective

α‐Keggin polyoxometalates (POMs) [XW12O40]n− (X = Al, Si, P, S) are widely used in batteries owing to their remarkable redox activity. However, the mechanism underlying the applications appears inconsistent with the widely accepted covalent bonding nature. Here, first‐principles calculations show that XW12 are core–shell structures composed of a shell and an XO4n− core, both are stabilized by covalent interactions. Interestingly, owing to the presence of a substantial number of electrons in W12O36 shell, the frontier molecular orbitals of XW12 are not only strongly delocalized but also exhibit superatomic properties with high‐angular momentum electrons that do not conform to the Jellium model. Detailed analysis indicates that energetically high lying filled molecular orbitals (MOs) have reached unusually high‐angular momentum characterized by quantum number K or higher, allowing for the accommodation of numerous electrons. This attribute confers strong electron acceptor ability and redox activity to XW12. Moreover, electrons added to XW12 still occupy the K orbitals and will not cause rearrangement of the MOs, thereby maintaining the stability of these structures. Our findings highlight the structure–activity relationship and provide a direction for tailor‐made POMs with specific properties at atomic level.

Tridentate Lewis Acids Based on Tribenzotriquinacene Chalices.

Chalice-shaped tridentate poly-Lewis acids (PLA) based on the tribenzotriquinacene (TBTQ) scaffold have been synthesised. Stannylation of the alkyne units, attached via phenyl-spacers to the benzhydrylic positions to the TBTQ scaffold, with Me2NSnMe3 afforded the trimethyltin substituted TBTQ derivative. Replacement of these tin functions with other elements resulted in rigid boron- and aluminium-functionalised PLAs. More flexible PLAs were obtained by hydrometallation reactions of the terminal alkyne groups of 4b,8b,12b-tris((ethynyl)phenyl)tribenzotriquinacene. The resulting poly-Lewis acids were tested for their acceptor abilities in host-guest experiments with suitable bases. Preliminary tests with pyridine led to the synthesis of a large tridentate base with three pyridyl groups attached to a TBTQ backbone. Complexation of this Lewis base with the PLAs resulted in the formation of aggregates, which were studied in solution in more detail by 1H DOSY NMR experiments regarding their size. Further experiments were performed with the tridentate bases 1,4,7-trimethyl-1,4,7-triazacyclononane and tris((dimethylphosphino)methyl)phenylsilane.

Unveiling the Multielectron Acceptor Properties of π-Expanded Pyracylene: Reversible Boat to Chair Conversion.

In this work, the chemical reduction of a hybrid pyracylene-hexa-peri-hexabenzocoronene (HPH) nanographene was investigated with different alkali metals (Na, K, Rb) to reveal its remarkable multielectron acceptor abilities. The UV-vis and 1H NMR spectroscopy monitoring of the stepwise reduction reactions supports the existence of all intermediate reduction states up to the hexaanion for HPH. Tuning the experimental conditions enabled the synthesis of the HPH anions with gradually increasing reduction states (up to -5) isolated with different alkali metal ions as crystalline materials. The single-crystal X-ray diffraction structure analysis demonstrates that the highly negatively charged HPH anions (-4 and -5) exhibit a drastic geometry change from boat-shaped (observed in the neutral parent, mono- and dianions) to a chair conformation, which was proved to be fully reversible by NMR spectroscopy. DFT calculations show that this geometry change is induced by an enhanced interaction between the coordinated metal ions and negatively charged HPH core in the chair conformation.

Polarity of Aqueous Solutions

This short review describes the expansion of the solvatochromic approach utilizing water-soluble solvatochromic dyes to the analysis of solvent features of aqueous media in solutions of various compounds. These solvent features (polarity/dipolarity, hydrogen bond donor ability (HBD acidity), and hydrogen bond acceptor ability (HBA basicity)) vary depending on the nature and concentration of a solute. Furthermore, the solvent features of water (the solvent dipolarity/polarizability and hydrogen bond donor ability) in solutions of various compounds describe multiple physicochemical properties of these solutions (such as the solubility of various compounds in aqueous solutions, salting-out and salting-in constants for polar organic compounds in the presence of different inorganic salts, as well as water activity, osmotic coefficients, surface tension, viscosity, and the relative permittivity of aqueous solutions of different individual compounds) and are likely related to changes in the arrangement of hydrogen bonds of water in these solutions.

Antimony centre in three different roles: does donor strength or acceptor ability determine the bonding pattern?

A set of antimony(III) compounds containing a ligand (Ar) with a pendant guanidine function (where Ar = 2-[(Me2N)2CN]C6H4) was prepared and characterized. This includes triorgano-Ar3Sb, diorgano-Ar2SbCl and monoorgano-ArSbCl2 compounds and they were characterized by 1H and 13C NMR spectroscopy and by single-crystal X-ray diffraction analysis (sc-XRD). The coordination capability of Ar3Sb and Ar2SbCl was examined in the reactions with either cis-[PdCl2(CH3CN)2] or PtCl2 and complexes cis-[(κ2-Sb,N-Ar3Sb)MCl2] (M = Pd 1, Pt 2) and [(κ3-N,Sb,N-Ar2SbCl)MCl2] (M = Pd 3, Pt 4) were isolated, while their structures were determined by sc-XRD. Notably, the ligands Ar3Sb and Ar2SbCl exhibit different coordination modes - bidentate and tridentate, respectively - and the antimony exhibits three distinct bonding modes in complexes 1-4, which were also subjected to theoretical studies.

Pyroelectric-Effect-Assisted Near-Infrared-Driven Photoelectrochemical Biosensor Based on Exponential DNA Amplifier for MicroRNA Detection.

Although near-infrared responsive photoelectrochemical (PEC) biosensors have less damage to biological components compared to UV-visible light, they still reveal an inferior response due to the rapid recombination of photogenerated electron-hole. In this study, a near-infrared-driven PEC biosensor is fabricated for microRNA (miRNA) detection via integrating photoelectricity and pyroelectricity. Upon the introduction of target miRNA-21, the exponential DNA amplifier is triggered based on enzyme-assisted strand displacement amplification (SDA), releasing multiple Ag2S reporter probes to hybridize with capture probes immobilized on a CdS-2-mercaptobenzimidazole (2MBI)-modified photoelectrode. As a result, under the stimulation of NIR, the photoelectric conversion of Ag2S NPs generates the photocurrents. In addition, due to the strong hole acceptor ability of MBI, the pyroelectric effect of CdS-2MBI nanocomposites is enhanced, which generates highly pyroelectro-induced charge separation efficiency and induces the pyroelectric current benefited from the spontaneous polarization of CdS-2MBI caused by the temperature variation under the function of Ag2S nanoheaters. Impressively, this PEC biosensor has achieved the sensitive and selective determination of miRNA-21 with a detection limit as low as 54 fM. Overall, this NIR-driven PEC biosensor based on pyroelectric and photoelectric effects opens up a new horizon for bioanalysis and early disease diagnosis.

An Exploration of the Hydrogen Bond Donor Ability of Ammonia.

Ammonia is an important molecule due to its wide use in the fertiliser industry. It is also used in aminolysis reactions. Theoretical studies of the reaction mechanism predict that in reactive complexes and transition states, ammonia acts as a hydrogen bond donor forming N-H⋅⋅⋅O hydrogen bond. Experimental reports of N-H⋅⋅⋅O hydrogen bond, where ammonia acts as a hydrogen bond donor are scarce. Herein, the hydrogen bond donor ability of ammonia is investigated with three chalcogen atoms i. e. O, S, and Se using matrix isolation infrared spectroscopy and electronic structure calculations. In addition, the chalcogen bond acceptor ability of ammonia has also been investigated. The hydrogen bond acceptor molecules used here are O(CH3 )2 , S(CH3 )2 , and Se(CH3 )2 . The formation of the 1 : 1 complex has been monitored in the N-H symmetric and anti-symmetric stretching modes of ammonia. The nature of the complex has been delineated using Atoms in Molecules analysis, Natural Bond Orbital analysis, and Energy Decomposition Analysis. This work presents the first comparison of the hydrogen bond donor ability of ammonia with O, S, and Se.

Spectroscopic determination of the acidity constants and the effects of pH, temperature and solvents on the tautomerism of 1-substituted phenyl-3,5-diphenylformazans

UV–visible spectra were used to determine the acidity constants and the tautomeric properties of 1-substituted phenyl-3,5-diphenylformazans. The protonation and deprotonation behaviors of the compounds were investigated at different pHs. Protonation was observed for all compounds as two protons were acquired and deprotonation as one proton was lost. The effects of solvents on the tautomerism of 1-substituted phenyl-3,5-diphenylformazans were also investigated in neutral, acidic, and basic solutions at different pH and temperatures. The tautomerism interconversion percentages for the studied formazans were calculated from the absorption spectra obtained for different solvents at various temperatures. It was observed that the chelate form of the studied formazans was the dominant structure. It was concluded that the type of the substituents and hydrogen bonding acceptor ability of the solvents were the significant factors for the interaction in tautomerism.

π Acceptor Abilities of Anionic Ligands: Comparisons Involving Anionic Ligands Incorporated into Linear d10 [(NH3)Pd(A)]-, Square Planar d8 [(NN2)Ru(A)]-, and Octahedral d6 [(AsN4)Tc(A)]- Complexes.

Extended transition state-natural orbitals for chemical valence (ETS-NOCV)] data were used to rank electron acceptor capacities for several potentially synergistic anionic ligands incorporated into linear d10 [(NH3)Pd(A)]-, square planar d8 [(NN2)Ru(A)]-, and octahedral d6 [(AsN4)Tc(A)]- complexes [A = anionic ligand, NN2 = HN(CH2CH2CH2NH2)2, and AsN4 = [As(CH2CH2CH2NH2)4]-]. It was possible to differentiate between the best acceptors, among them BI2- and B(CF3)2-, and the poorest ones. A sizable fraction of the anionic ligands studied exhibit similar acceptor capacities (backbonding), mostly regardless of d electron count. A number of trends were discerned, including the fact that acceptor capacity decreases down families and across rows but increases down families of the peripheral substituents. The latter appears tied to the ability of the peripheral ligands to compete with the metal in donating electrons to the ligand-binding atom.

Recombination of hydrogen bonds clipping interfacial film effectively for dehydrated tight oil

Tight oil is an important unconventional oil resource. However, during the extraction process of tight oil, a large amount of tight oil emulsion is generated, combined with offshore oil releases, have caused serious environmental problems. Owing to the high content of resin molecules, which adsorbed the interfacial water molecules in the form of hydrogen bonds, as well as tightly bound resin molecules via π–π stacking, the interface structure is stable; hence, it is difficult to separate oil and water. In this study, the hydrogen-bond energy of O atoms in common groups and water molecules was analyzed, and the efficient separation of oil and water was realized by the regulation of hydrogen-bond energies of the demulsifier molecules and interfacial water molecules. The O atoms in EO, PO, ester group and hydroxyl group were named as Type 1–6 O atoms. The compatibility of the demulsifier and tight oil was improved by the introduction of an aromatic structure, which combined with the tight oil molecules via π–π stacking. At the same time, by the introduction of Types 1–6 O atoms, the electronegativity (Hydrogen bond acceptor ability) of the demulsifier molecules was optimized to improve the hydrogen-bond energy formed between the demulsifier and water molecules effectively; then, the interfacial resin molecules were replaced to form stronger hydrogen bonds with water molecules, weakening the π-π stacking interaction between resin molecules for clipping the interfacial film; thus, the mass-transfer efficiency of water molecules at the oil–water interfacial is enhanced.

Exploring solvation behaviour of biocompatible ionic liquid 2-hydroxyethylammonium formate + polyethylene glycols mixtures: Role of oxyethylene and hydroxyl units of PEGs

The favourable modification of the physicochemical properties of the ionic liquid with green co-solvent and their molecular level characterization with spectroscopic techniques is the area of current research. Further, the co-solvent modified ionic liquid mixtures furnishes interesting properties which render the utility of these solvents in several important applications. In the current work, the effects of addition of two polyethylene glycols (PEGs) with average molecular weights of 200, and 600 on solvent properties of IL 2-hydroxyethyl ammonium formate (HEF) has been explored with the help of solvatochromic absorbance probes. The physicochemical characteristics of the ionic liquid mixtures are altered in an unexpectedly positive way when PEGs are added to IL HEF. The absorbance behaviour of the solvatochromic probes Reichardt dye 33 shows interestingly positive non-ideal behaviour, which may be attributed to the high dipolarity/polarizability (π*) and hydrogen bond donor ability (HBD) (α) of the HEF + PEG mixtures. Further, the Kamlet-Taft parameters, including hydrogen bond acceptor ability (HBA) (β), and hydrogen bond donor ability (HBD) (α), and dipolarity/polarizability (π*) of the HEF + PEG binary mixtures display nonideality, which may be because of the strong Hydrogen bond networking of HEF-PEG molecules along with solute-HEF/PEG interaction present in the mixtures. Moreover, the preferential solvation approach has been invoked to explore the solute–solvent/solvent–solvent interactions present in the HEF + PEGs binary mixtures. The Redlich–Kister (CNIBS/R–K) theoretical model predicts the experimental results obtained by solvatochromic probe studies in satisfactory manner. The results of the DFT and FTIR study also predict the possibility of the H-bonding interactions in HEF + PEGs mixtures.

Spectroscopic study of solvent effects on the electronic absorption spectra of morpholine and its complexes

The electronic absorption spectra of morpholine and its five morpholine complexes have been studied in different solvents of various polarities. The regression and correlation coefficients have been calculated with the SPSS program. Solvation energy relationships were deduced from spectral shifts and correlated with solvent parameters α (solvent hydrogen bond donor acidity), β (solvent hydrogen bond acceptor basicity), and π* (dipolarity/polarizability). The percentage contributions of the calculated solvatochromic parameters show that classic solvation effects play a major role in explaining the spectral shifts in all investigated complexes. The blue shift of [Fe(MOR)3Cl3]·4H2O, [Ni(MOR)4Cl2]·4H2O, and [Cu(MOR)4Cl2]·6H2O complexes is due to the formation of hydrogen bonds, which suggests the stabilization of the ground electronic state compared with the excited state. [CuNi(MOR)2Cl4]·4H2O and [CuZn(MOR)3Cl4]·2H2O are mixed metal complexes that suffer a red shift due to the solute-solvent interactions, which causes stabilization of the excited solute state with increasing solvent polarity. The bands are affected by specific solute-solvent interactions including hydrogen bond donor ability (acidity) and hydrogen bond acceptor ability (basicity) and nonspecific solute-solvent interactions including electromagnetic interaction between the dipole moments of solute and polar solvents.

An Ultra‐Sensitive Fluorescent Probe Based on Hybridized Local and Charge‐Transfer Materials for Quantitative Detection of Propanol Isomers

AbstractIsopropanol has been widely applied in various fields as an important chemical solvent, which is produced by direct hydration of propylene accompanied with the byproduct of n‐propanol. Herein, an ultra‐sensitive fluorescent probe of TPA‐9AC, based on a non‐equivalent hybridized local and charge‐transfer (HLCT) material, is designed and synthesized to quantitatively detect the percentage of n‐propanol in propanol isomers. Owing to the stronger electron acceptor ability of n‐propanol, the excited state of probe transfers from highly emissive HLCT state to non‐emissive charge‐transfer state, resulting in the substantial fluorescence quenching. The low limit of detection (LOD) is achieved as sensitive as 0.02% v/v of n‐propanol in isopropanol. This contribution demonstrates a new approach to distinguish propanol isomers and an effective strategy for designing real‐time fluorescent sensors with high performances.

Reaction characteristics of metal-salt coordinated deep eutectic solvents during lignocellulosic pretreatment

A binary deep eutectic solvent consisting of choline chloride and glycerol (ChCl/Gly) is proven to be ineffective in lignocellulosic pretreatment, and arbitrarily screening coordination agents makes it difficult to directionally construct a valid solvent. This study investigated the designable diversity of ternary ChCl/Gly coordinated with various metal-salts by elucidating solvent properties and reaction characteristics. Alkaline/acidic strengths and hydrogen-bonding forces were key factors for component fractionation. Pretreatment performance was typically poor for solvents with few acidic sites and active protons (i.e., ChCl/Gly-KCl and MgCl2), as well as those with close proximity of H-bond donor and acceptor abilities (ChCl/Gly-ZnCl2). By contrast, strong alkaline ChCl/Gly-K2CO3 could achieved 72 % of delignification with a remarkable holo-cellulose preservation (70.8–80.9 %). Delignification underwent an independent rate-control of solvent diffusion and surface reaction with an endothermic nature (17.1 kJ/mol of ΔH and 20.3 kJ/mol of apparent activation energy). High temperature was beneficial for mitigating diffusion constraint at the initial pretreatment stage, maximally increasing the reaction rate by 7.7-fold. Moreover, Lewis acidic ChCl/Gly-FeCl3 (or AlCl3) removed 76–84.4 % of hemicellulose and 47.6–61.9 % of lignin while significantly deconstructing the aryl-ether bonds and β-O-4 linkages. But for acidic ChCl/Gly solvents, biomass dissolution was inconformity with the independent diffusion/reaction-controlling process, owing to the excessive hemicellulose degradation and hydrolytic by-product formation (maximally 91 g/kg xylose and 4 g/kg furans). Based on the lignin structural characterization, the potential reaction mechanism related to solvent properties was proposed to develop efficient ternary coordinated deep eutectic solvents.

Synthesis, characterisation and corrosion inhibitory study of Meldrum’s acid Thiosemicarbazone: Weight Loss, SEM-EDX and DFT

Meldrum’s acid thiosemicarbazone derivative, 2,2-dimethyl-5-(4-nitrobenzylidene)-1,3-dioxane-4,6-dione bis(4-ethyl-3-thiosemicarbazone) (4NMATSC), was successfully synthesised and characterised using the attenuated total reflectance-Fourier transform infrared (ATR-FTIR), nuclear magnetic resonance (NMR), ultraviolet–visible (UV–Vis) spectroscopies, and an elemental analyser. From the weight loss technique and SEM-EDX mapping analysis, 4NMATSC was verified to be a competent corrosion inhibitor in HCl by forming a protective layer on the surface of mild steel via adsorption. The effectiveness of the inhibitor increased as the concentrations of the inhibitor increased. The corrosion inhibitory effectiveness was 68.88 % at the highest concentration of 5 ppm. The density-functional theory (DFT) study revealed that the 4NMATSC was more favourable to nucleophilic attack through CS (covalent bond) to the mild steel surface to form an adsorption layer on the mild steel surface. Besides that, the values of ionisation potential, electron affinity, electron donating ability, and electron accepting ability deduced that the compound was preferred to donate electrons as compared to back-donating to the mild steel surface.