Positive Cotton Effect Research Articles

Biofuel-Driven Stepping Chiral Supramolecular Transfer Container.

Herein, we reported a biofuel-driven recyclable chiral supramolecular transfer container based on hexacationic triphenylamine cage and nucleotides. Possessing rotatable paddle rigid backbones, the artificial receptor effectively encapsulated nucleotides with a high binding constant up to 5.37×105 M-1 in water, displaying guest-induced efficient fluorescence enhancement with quantum yield increased from 6.5% to 16.6%. Especially, the achiral cage could effectively bind with adenosine triphosphate to activate chirality transfer from substrates to the single molecular container, giving circularly polarized luminescence at 575 nm and positive Cotton effect peaks with significant asymmetric factor (gabs = +6.4×10-4). Meanwhile, the adaptive chiral supramolecule not only has reversible thermal responsiveness but also could stepwise regulate chirality transfer by the catalysis of hexokinase and apyrase in tandem, showing recovery adaptive chirality after refueled, achieving dynamically regulated programmable multistate chiral luminescent supramolecules. Therefore, the biofuel-driven chiral supramolecular transfer container could be successfully applied in chiral logic gates and multilevel information encryption, providing new insight into intelligent chiral materials.

Biofuel‐Driven Stepping Chiral Supramolecular Transfer Container

Herein, we reported a biofuel‐driven recyclable chiral supramolecular transfer container based on hexacationic triphenylamine cage and nucleotides. Possessing rotatable paddle rigid backbones, the artificial receptor effectively encapsulated nucleotides with a high binding constant up to 5.37×105 M‐1 in water, displaying guest‐induced efficient fluorescence enhancement with quantum yield increased from 6.5% to 16.6%. Especially, the achiral cage could effectively bind with adenosine triphosphate to activate chirality transfer from substrates to the single molecular container, giving circularly polarized luminescence at 575 nm and positive Cotton effect peaks with significant asymmetric factor (gabs = +6.4×10‐4). Meanwhile, the adaptive chiral supramolecule not only has reversible thermal responsiveness but also could stepwise regulate chirality transfer by the catalysis of hexokinase and apyrase in tandem, showing recovery adaptive chirality after refueled, achieving dynamically regulated programmable multistate chiral luminescent supramolecules. Therefore, the biofuel‐driven chiral supramolecular transfer container could be successfully applied in chiral logic gates and multilevel information encryption, providing new insight into intelligent chiral materials.

Hydrogen bond, protonation, and coordination-induced supramolecular chirality inversion in glutamide-based amphiphilic self-assembly

In this study, we have synthesized two types of Y-shaped chiral amphiphiles, namely L-BG and L-PG, with a benzene or pyridine ring at the terminal position, respectively. The optimized conformations of both amphiphiles indicate the presence of intramolecular interactions. In dimethylformamide (DMF) solution at the monomeric state, both amphiphiles exhibit positive cotton effects; however, in DMF/H2O mixed solution, the cotton effects are inverted. Molecular dynamics simulations reveal that both intermolecular and intramolecular hydrogen bonds facilitate the inversion of supramolecular chirality. Additionally, protonation and coordination of L-PG assembly results in chirality inversion and transformation of emission. This study emphasizes the significance of both inter- and intramolecular hydrogen bonds in the assembly process, providing insights into stimuli-responsive chiral supramolecular materials.

One-pot fabrication of sodium deoxycholate based supramolecular self-healing antibacterial double network hydrogels

Double network (DN) hydrogels have emerged as a significant technology for enhancement of mechanical strength of weak supramolecular gels. In the present study, we report the one-pot route for design of a low molecular weight gelator based DN hydrogel wherein sodium deoxycholate (NaDC) forms the primary network entangled with agar matrix. Various compositions of the reported agar-NaDC hydrogels were examined through FTIR, sol-gel transition temperature (Tsg), XRD, circular dichroism (CD), scanning electron microscopy (SEM), hydrophobicity probe studies, Zeta potential studies and rheology measurements. Analysis of all studies together reveal that 1 mg/ml agar-NaDC DN hydrogel is the optimum composition that exhibits dense networking with primarily β-sheet like structure, highest mechanical strength as well as self-healing characteristics with reversed optical activity and highest Tsg. Antibacterial activity studied using inhibition zone method suggests that 1 mg/ml agar-NaDC gel demonstrates significant bactericidal effect unlike the pure gel with an inhibition zone of ∼25 mm against E.coli after 24 h and ∼32 mm after 48 h incubation. The antibacterial activity was unique for this composition of the DN hydrogel which is attributed to its reversal in optical activity exhibiting positive cotton effect resulting in stronger interaction with the bacterial cell wall. Additionally, nearly 2 times reduced water absorption capacity of the 1 mg/ml agar-NaDC DN hydrogel compared to pure NaDC hydrogel ensures the retention of its mechanical strength as well as other properties in high moisture containing environment. Hence, the 1 mg/ml agar-NaDC DN hydrogel holds appreciable potential as a novel strong supramolecular self-healing antibacterial hydrogel with sustained release characteristics primarily important for biomedical applications.

Creation of Quasi‐DNA Origami at the Air/Water Interface Using the Collapsed Mechanism of Langmuir Monolayer

AbstractIt has achieved the preparation of quasi‐deoxyribonucleic acid (DNA) origami using the techniques of organized molecular films. After the adsorption of DNA from the subphase onto a Langmuir monolayer of polymers containing diamino‐s‐triazine rings, the monolayer collapses owing to high surface pressure, resulting in the formation of a three‐dimensional folded structure of DNA. A homopolymer featuring a diamino‐s‐triazine ring and a copolymer containing 20 % long alkyl chains are used to form the Langmuir monolayer. A‐T base pairs of salmon testis‐derived DNA from the subphase are hydrogen‐bonded and adsorbed onto each Langmuir monolayer. Following the collapse of the Langmuir monolayer, the film height almost doubles, indicating the formation of a bilayer structure consisting of a bioadsorbed polymer monolayer, especially evident in copolymer‐collapsed films. During this period, the bioconjugated bilayer structure adopts a mesoscopic linear morphology within the plane. In this quasi‐DNA origami structure, the chirality in the DNA molecule is maintained, as evidenced by the circular dichroism (CD) spectra displaying a positive Cotton effect. These results correspond to the proposal of a new DNA morphology control technology.

Spectral and HPLC Analyses of Synthesized Butin and Butein.

Butin and butein are significant bioactive flavanones derived from plants, existing as tautomers of each other. However, their physicochemical attributes, such as their spectral profiles under varying experimental conditions in aqueous solutions and established chromatographic methods for distinguishing between them, remain undetermined. In this study, we determined the basic properties of butin and butein using conventional spectroscopic, reversed-phase, and chiral HPLC analyses. The spectra of the synthesized butin and butein were analyzed using a UV-Vis spectrophotometer in several solvents with different polarities as well as in aqueous solutions at various pH values. Furthermore, the behavior of the measured spectra was reproduced by calculations to reveal the effects of the solvent and pH on the spectra of butin and butein in organic and aqueous solutions. Subsequently, we assessed the structural stability of butin and butein using reversed-phase HPLC, which revealed that butein is unstable compared with butin in a general culture medium. The synthesized butin was effectively separated into R- and S-isomers with positive and negative Cotton effects, respectively, via HPLC using a chiral column. These findings will aid in uncovering the individual properties of both butin and butein that may have been concealed by their tautomerism and enable the synthesis of S-butin, which is typically challenging and time-consuming to isolate.

Preparation of magneto-electro-optically active polymer using Fe ionic liquid as electro-magnetic dopant

In this research, we report the synthesis of conjugated polymers with magnetism. Electrochemical polymerization in liquid crystal was conducted with 1-butyl-3-methylimidazolium tetrachloroferrate (BMITF), which is a paramagnetic character having a large magnetic susceptibility, as a supporting salt. The polymer films thus obtained had magnetism because BMITF remains in the films as a dopant. Poly(2,2′-bithiophene) and poly(bis-(3,4-ethylenedioxythiophene)) were prepared in nematic or cholesteric liquid crystal with BMITF by electrochemical polymerization. Transcription of the liquid crystal structure was succeeded with a small amount of BMITF. Blush or fingerprint structures were confirmed by polarizing optical microscopy observation. The addition of the excess amount of BMITF broke the structure of the liquid crystal. Poly(2,2′-bithiophene) transcribed the cholesteric liquid crystal structure showed a negative Cotton effect, indicating with left-handed helical structure. Poly(bis-(3,4-ethylenedioxythiophene)) transcribed the cholesteric liquid crystal structure showed a positive Cotton effect, indicating the polymer forms a right-handed helical structure. The X-ray photoelectron spectroscopy measurements, confirming the existence of Fe element in the polymers thus obtained. From the electron spin resonance measurements, the polymers thus obtained showed magnetic activity. This method affords facile synthesis of conjugated polymers with magnetism.

Chiral Ligand‐Induced Inversion and Tuning of Excitonic Optical Activity in Intrinsically Chiral CsPbBr3 Perovskite Nanoplatelets

AbstractOwing to their attractive optical and chiroptical properties, chiral metal halide perovskites have received increasing attention, with potential applications ranging from photonics and optoelectronics to spintronics. Metal halide perovskite nanocrystals with either intrinsic or extrinsic (e.g., chiral ligand‐induced) chirality have been reported recently, and the interplay between these two types of chirality has yet to be addressed. Herein, the inversion and tuning of excitonic optical activity is reported in intrinsically chiral perovskite nanoplatelets, originating from interactions between their structural chirality (due to the spontaneously formed screw dislocations in the crystalline lattice) and the surface enantiomeric (R/S) chiral ligands R/S‐phenylethylammonium bromide. Through post‐preparative exposure of the perovskite nanoplatelets to these R/S ligands of varied contents, either chiral ligand‐induced intrinsic chirality inversion or negative and positive Cotton effects induced by the ligands via electronic coupling between the ligand and the nanoplatelets are identified. These findings deepen understanding of the modulation of excitonic optical activity in chiral perovskites and can guide the rational design and synthesis of novel chiral materials.

Helical self-assembly and Fe3+ detection of V-shaped AIE-active chiral tetraphenylbutadiene-based polyamides.

Chiral aggregation-induced emission (AIE) molecules have drawn attention for their helical self-assembly and special optical properties. The helical self-assembly of AIE-active chiral non-linear main-chain polymers would produced some desired optical features. In this work, a series of V-shaped chiral AIE-active polyamides P1-C3, P1-C6, P1-C12 and linear P2-C3, P2-C6, bearing n-propyl/hexyl/dodecyl side-chains, based on tetraphenyl-butadiene (TPB) were prepared. All of the target main-chain polymers exhibit distinct AIE characteristics. The polymer P1-C6 with moderate length alkyl chains shows better AIE properties. The V-shaped main-chains and the chiral induction of (1R,2R)-(+)-1,2-cyclohexanediamine in each repeatingunit promote the polymer chains display helical conformations, and multiple helical polymer chains induce nano-fibers helicity when the polymer chains aggregate and self-assemble in THF/H2O mixtures. Simultaneously, the helical conformation polymer chains and helical nano-fibers cause P1-C6 produce strong CD signals with positive Cotton effect. Moreover, P1-C6 could also occur fluorescence quenching response to Fe3+ selectively with a low detection limit of 3.48 μmol/L.

Chiral superstructures of inorganic nanorods by macroscopic mechanical grinding

The development of mechanochemistry substantially expands the traditional synthetic realm at the molecular level. Here, we extend the concept of mechanochemistry from atomic/molecular solids to the nanoparticle solids, and show how the macroscopic grinding is being capable of generating chirality in self-assembled nanorod (NR) assemblies. Specifically, the weak van der Waals interaction is dominated in self-assembled NR assemblies when their surface is coated with aliphatic chains, which can be overwhelmed by a press-and-rotate mechanic force macroscopically. The chiral sign of the NR assemblies can be well-controlled by the rotating directions, where the clockwise and counter-clockwise rotation leads to the positive and negative Cotton effect in circular dichroism and circularly polarized luminescence spectra, respectively. Importantly, we show that the present approach can be applied to NRs of diverse inorganic materials, including CdSe, CdSe/CdS, and TiO2. Equally important, the as-prepared chiral NR assemblies could be served as porous yet robust chiral substrates, which enable to host other molecular materials and induce the chirality transfer from substrate to the molecular system.

A combined study on structures and vibrational spectra of the antiviral rimantadine using SQMFF and DFT calculations

In this research, a combined study on structures and vibrational spectra of antiviral rimantadine have been performed using hybrid B3LYP/6–311++G∗∗ calculations and the scaled quantum force field (SQMFF) procedure. Harmonic force fields and scaled force constants of Free Base (FB), Cationic (CA) and Hydrochloride (HCl) species derived from the antiviral rimantadine have been calculated in gas phase and in aqueous solution using normal internal coordinates and scaling factors. Good correlations were acquired comparing the theoretical IR, Raman, 1H– 13C-NMR and UV spectra of three species with the analogous experimental ones, suggesting probably, the presence of all them in both phases. The main force constants of three species have evidenced lower values than the corresponding to antiviral amantadine. The ionic character of N1–H33⋯Cl36 bond of HCl species in aqueous solution evidence positive Mulliken charge on N1 atom indicating that this species is as CA one. Rimantadine presents higher solvation energies in water than other antiviral species, such as chloroquin, niclosamide, cidofovir and brincidofovir. The FB and HCl species of rimantadine are slightly less reactive than the corresponding to amantadine while the opposite is observed for the CA species. The predicted ECD spectra for the FB and CA species show positive Cotton effect different from the negative observed for the HCl one. These different behaviours of three species of rimantadine could probably explain the differences observed in the intensities of bands predicted in the electronic spectra of these species.

Controlled helicity inversion, selective enantiomer release, and methanol recognition in azobenzene gel

Constructing artificial supramolecular materials is important because they possesses wide application in many fields such as bio-, chiral and information science. Here, we prepared a glutamide–azobenzene gelator (GAZS) which is both chiral and amphiphilic. The GAZS gel exhibited different cotton effects depending on the solvents, in methanol the gel was endowed with chiroptical switch properties under external stimuli. Selective enantiomer release could be achieved by the shrinkage process of the gel in methanol under UV irradiation. In alcohol solvents only the gel in methanol is opaque and has a positive cotton effect. We believe our work could provide some insights into the solvent recognition and the construction of chiroptical supramolecular materials.

DNA patterning utilizing mixed monolayer template by phase separation between hydrocarbons and fluorocarbons and evaluation of second-order structural maintenance ability

Adsorption of DNA molecules on mixed phase-separated monolayers composed of a hydrocarbon-containing comb copolymer with an s-triazine ring and a fluorinated s-triazine derivative and their fluorescence emission behavior were investigated. DNA molecules derived from salmon testes were selectively adsorbed only on the diamino-s-triazine ring of the hydrogenated copolymer in the monolayer from the subphase. A mixed monolayer of a hydrocarbon-based comb copolymer and an s-triazine derivative with fluorocarbons exhibited phase separation behavior on water surfaces and indicated expansion behavior, reflecting interactions on the subphase containing DNA molecules. The phase-separated morphology changed depending on the mixing ratio of the hydrogenated copolymer and fluorinated s-triazine derivative. After DNA adsorption, the height of the domain formed by the hydrocarbon chain was selectively increased. In addition, because the DNA molecules adsorbed on the phase-separated template film maintain their fluorescence emission ability, the second-order structure, which is the origin of the emission ability, was evaluated using circular dichroism spectroscopy. The phase-separated, template-adsorbed DNA molecules maintained the same positive Cotton effect as in solution and were predicted to retain exquisite and delicate steric structure, leading to functional occurrence.

Reaction of N-Acetylcysteine with Cu2+: Appearance of Intermediates with High Free Radical Scavenging Activity: Implications for Anti-/Pro-Oxidant Properties of Thiols.

We studied the kinetics of the reaction of N-acetyl-l-cysteine (NAC or RSH) with cupric ions at an equimolar ratio of the reactants in aqueous acid solution (pH 1.4–2) using UV/Vis absorption and circular dichroism (CD) spectroscopies. Cu2+ showed a strong catalytic effect on the 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) radical (ABTSr) consumption and autoxidation of NAC. Difference spectra revealed the formation of intermediates with absorption maxima at 233 and 302 nm (ε302/Cu > 8 × 103 M−1 cm−1) and two positive Cotton effects centered at 284 and 302 nm. These intermediates accumulate during the first, O2-independent, phase of the NAC autoxidation. The autocatalytic production of another chiral intermediate, characterized by two positive Cotton effects at 280 and 333 nm and an intense negative one at 305 nm, was observed in the second reaction phase. The intermediates are rapidly oxidized by added ABTSr; otherwise, they are stable for hours in the reaction solution, undergoing a slow pH- and O2-dependent photosensitive decay. The kinetic and spectral data are consistent with proposed structures of the intermediates as disulfide-bridged dicopper(I) complexes of types cis-/trans-CuI2(RS)2(RSSR) and CuI2(RSSR)2. The electronic transitions observed in the UV/Vis and CD spectra are tentatively attributed to Cu(I) → disulfide charge transfer with an interaction of the transition dipole moments (exciton coupling). The catalytic activity of the intermediates as potential O2 activators via Cu(II) peroxo-complexes is discussed. A mechanism for autocatalytic oxidation of Cu(I)–thiolates promoted by a growing electronically coupled –[CuI2(RSSR)]n– polymer is suggested. The obtained results are in line with other reported observations regarding copper-catalyzed autoxidation of thiols and provide new insight into these complicated, not yet fully understood systems. The proposed hypotheses point to the importance of the Cu(I)–disulfide interaction, which may have a profound impact on biological systems.

Oxidation of sodium cholate catalyzed by Au NPs and chiral selective binding of R- and S-binaphthyl derivatives

Au NPs generated in situ by photochemical reduction method were used as catalysts for the oxidation of sodium cholate. The circular dichroism of the oxidation product of sodium cholate exhibits a positive Cotton effect at 335 nm and an intense negative Cotton effect at 281 nm. Electrospray ionization (ESI) mass spectra and nuclear magnetic resonance (NMR) spectra were performed to characterize the chemical composition of the oxidation product of sodium cholate, revealing that two of the hydroxyl groups were selectively oxidized to oxo groups and the oxidation product is 12-hydroxy-3,7-diketo-cholanic acid (3,7-DKCA). The chiral recognition abilities of the aggregates of 3,7-DKCA were investigated by using planar chiral molecules R- and S-binaphthyl compounds. Compared with sodium cholate, the aggregates of 3,7-DKCA displayed higher chiral selective host–guest binding to the model molecules and the chiral recognition mechanism was clarified.

Axially chiral indolenine derived chromophore dimers and their chiroptical absorption and emission properties.

Yamamoto homocoupling of two chiral oxindoles led to the atropo-diastereoselective formation of an axially chiral oxindole dimer. This building block served as the starting material for the syntheses of axially chiral squaraine and merocyanine chromophore dimers. These dimers show pronounced chiroptical properties, this is, outstandingly high ECD signals (Δε up to ca. 1500 M-1 cm-1) as a couplet with positive Cotton effect for the P-configuration around the biaryl axis and a negative Cotton effect for the M-configuration. All investigated dimers also exhibit pronounced circularly polarised emission with anisotropy values of ca. 10-3 cgs. Time-dependent density functional calculations were used to analyse the three contributions (local one electron, electric-magnetic coupling, and exciton coupling) to the rotational strength applying the Rosenfeld equation to excitonically coupled chromophores. While the exciton coupling term proves to be the dominant one, the electric-magnetic coupling possesses the same sign and adds significantly to the total rotational strength owing to a favourable geometric arrangement of the two chromophores within the dimer.

Biphenyl-Induced Superhelix in l -Phenylalanine-Based Supramolecular Self-Assembly with Dynamic Morphology Transitions

Biphenyl-Induced Superhelix in <scp>l</scp> -Phenylalanine-Based Supramolecular Self-Assembly with Dynamic Morphology Transitions

Synthesis and Structure-Chirality Relationship Analysis of Steroidal Quinoxalines to Design and Develop New Chiral Drugs

Of the utmost importance of chirality in organic compounds and drugs, the present work reports structure-chirality relationship of three steroidal quinoxalines, which were synthesised by condensing diaminobenzenes with cholestenone. All the compounds were purified and characterised by varying analytical tools prior to their chiroptical analysis by circular dichroism (CD) technique. The substituent groups on quinoxalines contributed to determining the chiroptical properties of the compounds. The positive Cotton effects have been observed in the CD spectra of unsubstituted and methyl-substituted quinoxalines, which indicated their P helicity. Importantly, chloro-substituent on quinoxalines produced different CD behaviour, which can be attributed to the presence of three lone pairs of electrons on Cl atom. The present work provides guidelines for determining the chiral properties of steroidal quinoxalines, which can be useful to design and develop potential molecules of biological importance.

The desulfite mechanism exploration in a mode: Interaction between casein and sulfite by multi-spectrometry

Sulfite is a restricted food additive in various food preservatives. In our previous study, the sulfite was effectively removed by casein in shrimp samples. In this paper, the possible desulfite mechanism were explored by examining the interaction of casein with sulfite by fluorescence quenching spectroscopy, Ultraviolet (UV) adsorption, Fourier transform infrared (FTIR) and circular dichroism (CD) spectroscopy. The binding constant (KS), binding thermodynamics, and the interaction effect on the casein's conformation were investigated. The results showed that casein bound with sulfite via hydrophilic and hydrophobic interactions, with Ks values of 1.07 × 105 at 293 K and 2.78 × 104 at 307 K respectively. The secondary structures and the conformation of casein were changed due to the interaction between casein and sulfite, with a decrease in positive Cotton effect, indicating the casein-sulfite interaction reduced the structural stability of β-sheet folding of casein. As a result, this work provides the theoretical basis for the desulfite mechanism for the sulfite removal by casein in food processing.

Characterization of Molecular Arrangement of Long‐chain Ferrocenyl Derivatives Having Asymmetric Carbon by Method of Organized Molecular Films and Formation of Its Helical Nanofibers

AbstractFormation of organized molecular film and helical nanofibers of ferrocene derivatives having R‐12‐hydroxystearyl chains with asymmetric carbon was investigated. The 12‐hydroxystearyl chain, which induces “thixotropy” due to the formation and breakage of intermolecular hydrogen bonds, was introduced into the ferrocenyl unit. The structure of this derivative as a monolayer on the water surface and its Langmuir‐Blodgett (LB) film properties were analyzed. The monolayer showed a two‐dimensional phase transition, corresponding to the formation of fibrous morphology. In the LB multilayers, intermolecular hydrogen bonding between hydroxyl groups at the 12‐position of the chain and crystalline packing was observed. Raman mapping revealed the difference in surface morphology of each derivative depending on the number of 12‐hydroxystearyl chains. The derivative having the single chain showed a right‐handed helical morphology in the film and this behavior is similar to those having two and three chains. In circular dichroism spectra, the film showed a positive Cotton effect. Since the helical chains easily entangle with each other to form a sponge‐like organization, it was expected that the solvent uptake was the origin of gelation induction to its contact solvent.