UV Spectra Research Articles

Oxidation of [3]naphthylenes to cations and dications converts local paratropicity into global diatropicity

Oxidized states of polycyclic aromatic hydrocarbons are of importance as they represent charged conductive species in organic semiconductor substrates. In this work, we investigated the properties of radical cations and dications of linear and angular [3]naphthylenes, consisting of fused aromatic naphthalenoid and antiaromatic cyclobutadienoid moieties and containing different degrees of paratropicity. Electronic absorption and vibrational Raman spectroscopies were used to describe the more relevant bonding changes. Stretching force constants were evaluated to monitor the aromatic–antiaromatic alternation pattern upon oxidation. They showed us that the dication of linear [3]naphthylene became an overall global π-electron delocalized molecule. This result was supported by nucleus independent chemical shift (NICS) calculations and anisotropy of the current induced density (ACID) plots, as they evidenced the presence of a perimetral diatropic global ring current upon oxidation.

J-Aggregation of Chlorophyll-a Derivatives Inserting Fluorinated Phenylene Linker

Abstract Chlorophyll(Chl)-a derivatives inserting an ethynylene and fluorinated phenylene linker between the chlorin π-skeleton and hydroxymethyl group were prepared as chlorosomal Chl models. The self-aggregation of these derivatives was investigated by means of electronic absorption and circular dichroism spectroscopy. The spectroscopic results revealed that the electronic interactions between the chlorin core and the peripheral fluorinated aromatic π-systems had a large effect on the optical properties of the synthetic Chl-a derivative self-assemblies.

Electronic-vibrational resonance damping time-dependent photosynthetic energy transfer acceleration revealed by 2D electronic spectroscopy.

The effects of damping time of electronic-vibrational resonance modes on energy transfer in photosynthetic light-harvesting systems are examined. Using the hierarchical equations of motion (HEOM) method, we simulate the linear absorption and two-dimensional electronic spectra (2DES) for a dimer model based on bottleneck sites in the light-harvesting complex of photosystem II. A site-dependent spectral density is incorporated, with only the low-energy site being coupled to the resonance mode. Similar patterns are observed in linear absorption spectra and early time 2DES for various damping times, owing to the weak coupling strength. However, notable differences emerge in the dynamics of the high-energy diagonal and cross-peaks in the 2DES. It is found that the coupling of electronic-vibrational resonance modes accelerates the energy transfer process, with rates being increased as the damping time is extended, but the impact becomes negligible when the damping time exceeds a certain threshold. To evaluate the reliability of the perturbation method, the modified Redfield (MR) method is employed to simulate 2DES under the same conditions. The results from the MR method are aligned with those obtained from the HEOM method, but the MR method predicts faster dynamics.

New Ru(III) 2,6-Bis(2-benzimidazolyl)Pyridine Complexes Bearing p-sub-Benzyl Thiosemicarbazones Schiff Base: Synthesis, Characterization, DNA Binding and Anti-cancer Activity.

The six mononuclear Schiff's base Ru(III) complexes viz., [Ru(BZP)(LA)2].2NO3 (MRA), [Ru(BZP)(LB)2].2NO3 (MRB), [Ru(BZP))(LC)2].2NO3 (MRC), [Ru(BZP))(LD)2].2NO3 (MRD), [Ru(BZP)(LE)2].2NO3 (MRE) and [Ru(BZP)(LF)2].2NO3 (MRF), [(BZP = 2,6-bis(2-benzimidazolyl)pyridin], were synthesized using of p-sub-benzylthiosemicarbazones (BTS) [(Sub = 4-NO2 (LA), 4-N(CH3)2 (LB), 4-Cl (LC), 4-OCH3 (LD), 4-OCH2Ph (LE), 4-OH (LE)] and 4-OH (LF), as an ancillary ligand. The thiosemicarbazones ligands (LA-LF) were obtained by the condensation of p-substituted benzaldehyde and thiosemicarbazide. These complexes were characterized by elemental analysis, IR, ESR, ESI-MS, electronic absorption spectroscopy. The geometry was optimized by theoretical calculation using DFT and structure reveals that MRA-MRF adopt octahedral geometry. Further, the complexes were examined for anticancer against Leukemia cancer cell line K562 and shown significant responses to these cells. Moreover, DNA binding studies were studied with all complexes MRA-MRF and the binding constant (Kb) were found 1.54 x 104, 2.87 x 104, 1.67 x 104, 1.98 x 104 and 1.59 x 104, respectively. It was found that DNA binds in intercalation mode which is also validate by the Docking studies.

Biogenic Silver Nanoparticles for the Estimation of Lead in Chocolates

Background: This study aimed to demonstrate the practical and sensitive lead detection using biogenic silver nanoparticles in dark chocolate samples and silver nitrate was reduced using Syzygium cumini aqueous seed extract as a reducing agent to produce nanoparticles. The obtained NPs were characterized via spectrometry and scanning electron microscopy. Method: Silver nitrate was reduced using Syzygium cumini aqueous seed extract as a reducing agent to produce nanoparticles. The obtained NPs were characterized via spectrometry and scanning electron microscopy. The formation of NPs was confirmed by a shift in lambda max to 430 nm and the observation of 2 nm-sized particles in SEM. Data on change in lambda max as a function of time must be shown in a figure. Silver nanoparticles mixed with lead induce a red shift from the original 430 nm to 434 nm absorption maximum, confirming the efficiency of silver nanoparticles in finding a lead. Result: We evaluated that the limit of detection (LOD) was to be 0.8715 μg/mL, and the limit of quantification (LOQ) was found to be 150 μg/ mL. Conclusion: The prepared biogenic silver nanoparticles have been used to detect lead in spiked diluted chocolates.

Impact of ultrasonic pretreatment on pumpkin seed protein: Effect on protease activities, protein structure, hydrolysis kinetics and functional properties.

Adding value to food by-products, such as pumpkin seeds, is an important strategy for the complete utilization of plant foods and advancing sustainability goals. This study aimed to maximize the production of bioactive peptides from pumpkin seed protein (PSP) by combining ultrasonic (US) pretreatment (40kHz, 23.8W/L) with enzymatic hydrolysis. The PSP's structure after sonication and its effects on the commercial proteases (Brauzyn®, Flavourzyme®, Neutrase®) activity and degree of hydrolysis were studied. The hydrolysis consequences regarding solubility and antioxidant activity of the resulting peptides were also evaluated. Sonication of PSP increased enzymatic activity by up to 21.3% for Brauzyn®, 24.8% for Flavourzyme® and 19.2% for Neutrase®. Consequently, there was an increase in the degree of hydrolysis (up to 89%) using sonicated PSP, particularly at 60min/40°C. These effects can be attributed to ultrasound-induced protein conformation changes, including increased intrinsic fluorescence intensity (<22%), shifts in UV spectra, and alterations in FTIR amide bands, especially a decrease in β-sheet content (<7.14%). Additionally, ultrasonic pretreatment reduced particle size (<43.9%) and polydispersity index (<58%), enhancing enzyme accessibility by fragmenting protein aggregates, as observed via scanning electron microscopy. As a result, the peptides obtained from the hydrolysis of sonicated PSP exhibited higher protein solubility (12% to 49% at pH 6.0) and improved antioxidant activity (5.6% to 77%). Overall, sonication of PSP for 60min at 40°C followed by hydrolysis with Neutrase® proved to be the most effective strategy for producing highly soluble peptides with enhanced antioxidant properties, highlighting the potential of ultrasound as a valuable tool for optimizing bioactive peptide production. Based on these results, the developed process is ready for scale-up by the food industry, aiming to obtain protein hydrolysates with improved functional and/or nutritional properties from a low-cost raw material. In parallel, further researches can focus on the potential application of these hydrolysates as ingredients in bakery, meet or dairy products.

Comparative investigation of structural properties and biological applications of chemical and biogenic synthesis of zirconium dioxide (ZrO2) nanoparticles using Passiflora edulis.

Over the last decade, the environmental and wellness cost of antibiotic drug resistance to the societies have been astounding and require urgent attention Metal oxide nanomaterials have been achieved a pull-on deal with its entire applications in biological and photocatalytic applications. The present study conducts a comparative investigation on chemical and biogenic synthesis of zirconium dioxide (ZrO2) nanoparticles aimed at enhancing their efficacy in their applications. The plant extract of Passiflora edulis act as a reducing and capping properties offering a sustainable and eco-friendly alternative. ZrO2 nanoparticles have drawn a lot of scrutiny owing to their potential uses in numerous fields, including medicine and environmental remediation. Thereby produced ZrO2 nanoparticles were synthesized by employing sustainable techniques, and their successful production and their uses were confirmed by characterization by XRD, FTIR, UV-visible spectroscopy, SEM, EDAX, PL, TEM, XPS, TGA and Raman spectroscopy. The zirconia nanoparticles synthesized using chemical and green methods exhibited ultraviolet-visible (UV-Vis) absorption maxima at 221 and 224nm, respectively, demonstrating their synthesis. X-ray diffraction research revealed that the nanoparticles possess a tetragonal shape, with mean particle sizes of 11nm and 7nm, respectively. The synthesized ZrO2 nanoparticles (ZrO2 and Ext-ZrO2) exhibited inhibitory effects against Gram-positive strains (Bacillus subtilis and Staphylococcus aureus) and Gram-negative germs (Escherichia coli and Pseudomonas aureus), with zones of inhibition measuring (12, 8mm), (8, 11mm), (12, 15mm), and (7, 12mm) correspondingly. The antitumor activity of ZrO2 and Ext-ZrO2 was assessed using human colon cancer cells (HT29). The MTT assay was employed to assess the cytotoxicity of ZrO2 nanospheres on the HT-29 cell line at various concentrations (7.5, 15.6, 31.2, 62.5, 125, 250, and 500μg/ml). The HT29 cell line exhibits a reduction in cell viability from 96% to 34% when the concentration of ZrO2 nanoparticles escalates. The photocatalytic activity of ZrO2 and Ext-ZrO2 exhibited absorbance deterioration at around 445nm, resulting in the discoloration of Rh B dye under UV light irradiation after 100min, achieving maximal degradation rates of 96% and 99%, respectively. Consequently, the synthesized ZrO2 and Ext-ZrO2 may be utilized in antibiotic formulation, pharmaceutical sectors, and photocatalysts.

Catalytic-assisted remediation and phytotoxicity evaluations of organic pollutants in the presence of metal-doped Bi2O3-based NPs catalyst.

The chemical co-precipitation method was used to synthesize a variety of pure Bi2O3 and substituted Bi2-2xCoxCdxO3 NPs (x=0.0-0.8) and doping influences were evaluated based on the optical, photocatalytic, morphological, and structural characteristics. Powder X-ray diffraction (PXRD), scanning electron microscope (SEM), Energy dispersive X-ray (EDX), Fourier-transform infrared spectroscopy (FTIR), and UV-visible techniques were used to explore the characteristics of the synthesized Bi2O3-based NPs. XRD measurements confirmed the monoclinic structure and a P21/c space group, whereas the particle size was between 22 and 41nm. The SEM analysis gives the morphology of the synthesized NPs that were diverse and agglomerated platelets, whereas the EDX measurements provide the presence of Co and Cd in Bi2-2xCoxCdxO3 NPs. Additionally, FTIR investigations confirmed the existence of functional groups in Bi2-2xCoxCdxO3 NPs. The ultraviolet-visible absorbance region displaying a considerable red shift allowed for tuning of the band gap from 2.64 to 2.37eV. By analyzing the degradation of Reactive Black 5 (RB-5) dye in the presence of sunlight, pure Bi2O3 NPs showed 65.04% whereas the substituted Bi2-2xCoxCdxO3 NPs demonstrated enhanced photodegradation (86.40%) in 105min. For the degradation of RB-5 dye, the effects of catalyst dosage, dye concentration, and pH variations were studied as well. The phytotoxicity experiment was also performed by comparing the germination of Triticum aestivum seeds in treated and untreated RB-5 dye. In the untreated dye solution, seed germination was 50% inhibited, and in the treated dye solution, germination was observed to be 80%. Additionally, recycling investigations were used to confirm the stability of these fabricated nanoparticles, and the results showed that nanomaterials exhibited significant stability and reusability. Co and Cd-doped Bi2O3 NPs are promising solar-active photocatalysts for dye removal from wastewater applications because of their improved photocatalytic activity and narrow bandgap.

RES-CMCNPs Enhance Antioxidant, Proinflammatory, and Sensitivity of Tumor Solids to γ-irradiation in EAC-Bearing Mice.

Resveratrol (Res) is a bifunctional compound found in numerous plants, including grapes and mulberries. Nanotechnology has promising applications in medicine. The ability of various nanomaterials to serve as radiosensitizers against tumor cells were reported in several manuscripts. The present investigation aimed to assess the antitumor and radiosensitizing effects of Res-CMCNPs on EAC-bearing mice. Res-CMCNPs have been developed using the CMC emulsification cross-linking technique. Entrapment efficiency (%), particle size, Polydispersity index and ZETA potential, UV, FTIR spectra, and drug release were evaluated and described for RES-CMCNPs. The radiosensitizing properties of RES-CMCNPs were also evaluated in vitro and in vivo against EAC-carrying rodents. The LD50 of Res-CMCNPs was estimated and its 1/20 LD50 was prepared for treating EAC transplanted mice. The results revealed that the Res-CMCNPs exhibited a high entrapment efficiency (85.46%) and a size of approximately 184.60 ±17.36 nm with zeta potential value equals -51.866 mv. Also, the UV spectra of Res and Res-CMCNPs have strong absorption at 225 and 290 nm. The percentage of resveratrol release at pHs 5.8 and 7.4 was found to be 56.73% and 51.60%, respectively, after 24 h at 100 rpm. Also, the FTIR analysis confirmed the chemical stability of resveratrol in Res-CMCNPs cross-linking. The IC50 values of Res-CMCNPs against EAC cells viability were 32.99, 25.46, and 22.21 μg after 24-, 48- and 72 h incubation, respectively, whereas those of Res- CMCNPs in combination with γ-irradiation after 6-, 10 and 12-mins exposure were 24.07, 16.06 and 7.48 μg, respectively. Also, the LD50 of Res-CMCNPs was 2180 mg/kg.b.w. The treatment of EAC-bearing mice with Res-CMCNPs plus γ-irradiation improved plasma levels of NO, caspase-3, P53 and NF-kB levels as well as liver MDA, GSH, SOD, CAT, LT-B4, aromatase, Bax, Bcl2 and TGF-β levels and exhibited more significant anticancer activity than administration of Res- CMCNPs and/or exposure to γ-irradiation individually. On the other hand, administration of Res- CMCNPs in combination with γ-irradiation attenuated liver mRNAs (21, 29b, 181a, and 451) gene expression. Grafting resveratrol onto carboxymethyl chitosan appears to be a promising strategy for cancer therapy as a radiosensitizer, potentiating tumor cells' sensitivity to radiation by improving levels of proinflammatory features and antioxidant biomarkers.

A Comprehensive Comparison of Two Geometric Isomers of an Oxatetrasilacyclopentane

The highly electrophilic 1,4‐di‐t‐butyl‐2,2,3,3‐tetramethyl‐1,4‐diphenyltetrasilane‐1,4‐diyl bis(trifluoromethanesulfonate) (11) reacts with water to yield the cis/trans isomer mixture of 2,5‐di‐t‐butyl‐3,3,4,4‐tetramethyl‐2,5‐diphenyl‐1‐oxa‐2,3,4,5‐tetrasilacyclopentane (12). Cis‐12 and trans‐12 were separated and fully characterized by structural, spectroscopic and theoretical means. Remarkably, cis‐12 is preferably formed in the reaction mixtures, and the calculations reveal that this isomer is slightly more stable than trans‐12. This is due to the torsional distortion established in the crystal structure of the former isomer. Additionally, the electronic transitions between silicon backbone, the Ph substituents and the oxygen atoms are accounted for the main absorptions observed in the UV spectra of cis‐12 and trans‐12.

Microscopic Characterization Based Synthesis of Silver Nanoparticles Using Merremia quinquefolia (L.) Hallier f. Leaf Extract: Their Biological Approaches and Degradation of Methylene Blue Dye.

The green methods for the synthesis of silver nanoparticles (AgNPs) has developed popularity recently due to the low preparation costs, environmental friendliness, and non-toxicity of the precursors. In this study, AgNPs were synthesized using leaf extract from Merremia quinquefolia. Spectroscopic techniques were used for analyzing the functional groups, morphology, crystalline phase, and elemental composition of nanomaterials. The ultraviolet (UV) visible spectrometry absorption spectra of the AgNPs had a surface plasmon resonance band at 459 nm and Fourier transformed infrared spectrum (FTIR) analysis showed the presence of elements groups. X-ray diffraction (XRD) analysis indicates the crystalline structure and the energy-dispersive x-ray spectroscopy (EDAX) analysis shows strong signals for the silver element. Morphological analysis using transmission electron microscope (TEM) and scanning electron microscopy (SEM) analyses revealed that the AgNPs exhibited spherical shapes with an average size of 14 nm. Furthermore, it was indicated by the Raman spectra vibrational peak at 240 and 470 cm-1. The disk diffusion method showed that AgNPs were highly effective in inhibition of Gram-positive bacteria Staphylococcus aureus with a high inhibitory zone (14 ± 0.23 mm). Antioxidant activity, the IC50 values for assays DPPH (145.7 μg/mL) and ABTS (112.09 μg/mL), and albumin denaturation in human red blood cells showed higher anti-inflammatory activity. AgNPs had an IC50 value of 4.62 μg/mL against breast cancer (MCF-7) cells. Methylene blue (MB) degrading studies were used to assess the photocatalytic activity of AgNPs. They are at 240 min observed sunlight, the MB degradation efficiency was 94.89%. Overall, although M. quinquefolia synthesizes AgNPs for environmentally friendly applications, the study is indicated to fully understand the potential involved in treating breast cancer cells.

Minimum Energy Conical Intersection Optimization Using DFT/MRCI(2).

The combined density functional theory and multireference configuration interaction (DFT/MRCI) method is a semiempirical electronic structure approach that is both computationally efficient and has predictive accuracy for the calculation of electronic excited states and for the simulation of electronic spectroscopies. However, given that the reference space is generated via a selected-CI procedure, a challenge arises in the construction of smooth potential energy surfaces. To address this issue, we treat the local discontinuities that arise as noise within the Gaussian progress regression framework and learn the surfaces by explicitly incorporating and optimizing a white-noise kernel. The characteristic polynomial coefficient surfaces of the potential matrix, which are smooth functions of nuclear coordinates even at conical intersections, are learned in place of the adiabatic energies and are used to optimize the DFT/MRCI(2) minimum energy conical intersection geometries for representative intersection motifs in the molecules ethylene, butadiene, and fulvene. One consequence of explicitly treating the noise in the surfaces is that the energy difference cannot be made arbitrarily small at points of nominal intersection. Despite the limitations, however, we find the structures as well as the branching spaces to compare well with ab initio MRCI and conclude that this approach is a viable method to learn a smooth representation of DFT/MRCI(2) surfaces.

Characteristic Wavelength Selection and Surrogate Monitoring for UV–Vis Absorption Spectroscopy-Based Water Quality Sensing

Ultraviolet-visible (UV–Vis) absorption spectroscopy for in situ water quality sensing has garnered increasing attention. However, the selection of the characteristic wavelengths for water quality indicators has been underexplored in existing studies, resulting in surrogate monitoring models with low accuracy and high complexity. This research used field data from the Maozhou River in Shenzhen. The accuracy of the surrogate model based on the wavelength selection method is 134.8%, 52.5%, and 13.5% improvement in accuracy compared to the single wavelength method, the PCA method, and the full spectrum method, respectively. We investigate seven characteristic wavelength optimisation algorithms and five machine learning models for surrogate monitoring of five water quality indicators: TOC, BOD5, COD, TN, and NO3-N. The results indicate that the competitive adaptive reweighted sampling (CARS) method for wavelength selection, combined with ridge regression as a surrogate monitoring model, achieved the best performance in this study. The determination coefficient (R2) of the five water quality indicators were 0.80, 0.64, 0.82, 0.97, and 0.96, respectively. The study shows that for watersheds with relatively stable water chemical components, there is no need to use overly complex nonlinear models, and the regression model with characteristic wavelength selection can achieve good prediction results. This study provides detailed technical information on river water quality spectral surrogate monitoring, offering an important practice reference.

Extremophilic hemoglobins: The structure of Shewanella benthica truncated hemoglobin N.

Truncated hemoglobins (TrHbs) have an ancient origin and are widely distributed in microorganisms where they often serve roles other than dioxygen transport and storage. In extremophiles, these small heme proteins must have features that secure function under challenging conditions: at minimum, they must be folded, retain the heme group, allow substrates to access the heme cavity, and maintain their quaternary structure if present and essential. The genome of the obligate psychropiezophile Shewanella benthica strain KT99 harbors a gene for a TrHb belonging to a little-studied clade of globins (subgroup 2 of group N). In the present work, we characterized the structure of this protein (SbHbN) with electronic absorption spectroscopy and X-ray crystallography, and inspected its structural integrity under hydrostatic pressure with NMR spectroscopy and small-angle X-ray scattering. We found that SbHbN self-associates weakly in solution and contains an extensive network of hydrophobic tunnels connecting the active site to the surface. Amino acid replacements at the dimeric interface formed by helices G and H in the crystal confirmed this region to be the site of intermolecular interactions. High hydrostatic pressure dissociated the assemblies while the porous subunits resisted unfolding and heme loss. Preservation of structural integrity under pressure is also observed in non-piezophilic TrHbs, which suggests that this ancient property is derived from functional requirements. Added to the inability of SbHbN to combine reversibly with dioxygen and a propensity to form heme d, the study broadens our perception of the TrHb lineage and the resistance of globins to extreme environmental conditions.

An ab initio study of the electronic structure and spectroscopy of CO+ and CS+ diatomic cations

In this study, accurate ab initio methods are used to determine the electronic structure and spectroscopic properties of CS + and CO + cations of astrophysical relevance. The core-valence, scalar relativistic and complete basis set extrapolation (CBS) corrections are used in conjunction with the multireference configuration interaction method to obtain accurate properties. The results obtained are very satisfactory in comparison with the experiment. The potential energy curves have been plotted up to reasonable distances, allowing their asymptotes to be adequately described. The ionisation potentials of the neutral molecules were determined. They are 11.26 eV and 14.02 eV for CS and CO respectively. The vibrational energy levels and the rotational constants are also calculated. Our values are in very good agreement compared with the experiment. For instance, we have G ( 0 ) = 686.550 cm − 1 for the ground state X 2 Σ + ( CS + ), while the experimental value is 686.841 cm − 1 . New data for G ( 0 ) and for the rotational constants of the other states are proposed. The Franck-Condon Factors values computed are in perfect agreement with the experimental ones and this implies an accurate description of the transition properties and the radiative lifetimes.

What Two-Dimensional Electronic Spectroscopy Can Tell Us about Energy Transfer in Dendrimers: Ab Initio Simulations.

Two-dimensional (2D) electronic spectra of the phenylene ethynylene dendrimer with 2-ring and 3-ring branches were evaluated by combining the on-the-fly trajectory surface hopping nonadiabatic dynamics and the doorway-window simulation protocol. The ground state bleach (GSB), stimulated emission (SE), and excited-state absorption (ESA) contributions to the 2D signal were obtained and carefully analyzed. The results demonstrate that the ultrafast intramolecular nonadiabatic excited-state energy transfer (EET) from the 2-ring to the 3-ring units is comprehensively characterized by the SE and ESA signals. It is proven that the monitoring of the 2D ESA signal is especially convenient, because it is spectrally well separated from the SE and GSB signals. Hence, 2D electronic spectroscopy provides a detailed and multifaceted view of the intramolecular EET process in dendrimers.

Epigynum auritum-Derived Near-Infrared Carbon Dots for Bioimaging and Antimicrobial Applications.

The use of biomass feedstocks for producing high-value-added chemicals is gaining significant attention in the academic community. In this study, near-infrared carbon dots (NIR-CDs) with antimicrobial and bioimaging functions were prepared from Epigynum auritum branches and leaves using a novel green synthesis approach. The spectral properties of the synthesized NIR-CDs were characterized by ultraviolet-visible (UV-Vis) absorption and fluorescence spectroscopy. The crystal structures of the NIR-CDs were further characterized by high-resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), and X-ray diffraction (XRD). The NIR-CDs exhibited minimal toxicity, excellent biocompatibility, and high penetrability in both in vivo and in vitro environments, making them ideal luminescent probes for bioimaging applications. Moreover, the antimicrobial activity of NIR-CDs was tested against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), showing significant bacterial growth inhibition. The antimicrobial effect is likely attributed to the NIR-CDs disrupting the cell membrane integrity, leading to the leakage of the intracellular contents. Therefore, NIR-CDs hold promise as fluorescent bioimaging probes and antimicrobial agents.

Arechuines A-D, arecoline alkaloids from the peels of Areca catechu L.

Four novel arecoline alkaloid atropisomers, arechuines A-D (1 − 4), were obtained from the peels of Areca catechu L. Their structures were elucidated by UV, IR, MS and NMR spectra. The absolute configurations of (+)/(-)-4 were determined by comparing the experimental and calculated ECD spectra. Compounds 1 − 4 were evaluated for their neuroprotective effects in glutamate-induced HT22 cell and 3 revealed potent neuroprotective effects at 10 μM. These are the first reported arecoline alkaloid atropisomers isolated from A. catechu.

Physical properties of chlorophyll–quinone conjugates prepared via Friedel–Crafts reaction

Pheophytin-a derivatives possessing plastoquinone and phylloquinone analogs in the peripheral 3-substituent were prepared by Friedel–Crafts reactions of a 3-hydroxymethyl-chlorin as one of the chlorophyll-a derivatives with benzo- and naphthohydroquinones, respectively, and successive oxidation of the 1,4-dihydroxy-aryl groups in the resulting dehydration products. The 3-quinonylmethyl-chlorins exhibited ultraviolet–visible absorption and circular dichroism spectra in acetonitrile, which were composed of those of the starting 3-hydroxymethyl-chlorin and the corresponding methylated benzo- and naphthoquinones. No intramolecular interaction between the chlorin and quinone π-systems was observed in the solution owing to the methylene spacer. The first reduction potentials of the quinone moieties in the synthetic conjugates were determined by cyclic voltammetry and shifted positively from those of the reference quinones. The former quinonyl groups were reduced more readily by approximately 0.1 V than the latter quinones, which was ascribable to the stabilization of the quinonyl anion radical by the nearby macrocyclic chlorin π-chromophore. This observation implied that the reduction potentials of quinones were regulated by the close pheophytin-a derivative by through-space interaction. Considering the charge shift from pheophytin-a anion radical to plastoquinone and phylloquinone in reaction centers of photosystems II and I, respectively, the reduction potentials of these quinones as a determinant factor of the rapid electron transfer process would be dependent on the pheophytin-a in the photosynthetic reaction centers of oxygenic phototrophs as well as on the neighboring peptides.

Symmetry-Breaking Charge-Separation in a Subphthalocyanine Dimer Resolved by Two-Dimensional Electronic Spectroscopy.

Understanding the role of structural and environmental dynamics in the excited state properties of strongly coupled chromophores is of paramount importance in molecular photonics. Ultrafast, coherent, and multidimensional spectroscopies have been utilized to investigate such dynamics in the simplest model system, the molecular dimer. Here, we present a half-broadband two-dimensional electronic spectroscopy (HB2DES) study of the previously reported ultrafast symmetry-breaking charge separation (SB-CS) in the subphthalocyanine oxo-bridged homodimer μ-OSubPc2. Electronic structure calculations and 2D cross-peaks reveal the dimer's excitonic structure, while ultrafast evolution of the multidimensional spectra unveils subtle features of structural relaxation, solvation dynamics, and inhomogeneous broadening in the SB-CS. Analysis of coherently excited vibrational motions reveals dimer-specific low-frequency Raman active modes coupled to higher-frequency vibrations localized on the SubPc cores. Finally, beatmap amplitude distributions characteristic of excitonic dimers with multiple bright states are reported and analyzed.