Aromatic Region Research Articles

Theoretical investigation of the structure-property relationships of [n]benzocyclobutadiene carbon nanobelt: Aromaticity, singlet fission, and (hyper)polarizability

We present a theoretical design for a series of multifunctional nanomaterials that exhibit superior performance in singlet fission (SF) as well as exceptional nonlinear optical (NLO) performance. Our study focuses on a systematic investigation into the aromaticity, diradical character, excited state transition and (hyper)polarizability of the [n]benzocyclobutadiene carbon nanobelt system. To provide further guidance for designing multifunctional nanomaterials, our quantum chemical calculations propose empirical rules regarding the influence of aromatics on SF and NLO: Through an exploration of SF properties, we observed significant diradical character with radical sites exclusively located at anti-aromatic positions. Furthermore, these anti-aromatic positions serve as transition sites for excited state transitions to achieve the necessary low triplet excited states energy for SF. Then, by conducting calculations on NLO properties, we ascertain that the main tensor components of first-order hyperpolarizability (βtotal) and second-order hyperpolarizability (γtotal) come from the anti-aromatic region. However, there exists a contrasting impact of anti-aromaticity on first- and second-order hyperpolarizability density. The positive and negative contributions to first-order hyperpolarizability density mainly come from both aromatic and anti-aromatic regions while for second-order hyperpolarizability density it is contradictory. This study elucidates the role of aromatic sites in multifunctional nanomaterials with respect to diradical sites, excited state transition regions, and (hyper)polarizability density distribution.

Harnessing Cross-strand π-π Interlocking for Synergistic Enhancement of Immune Checkpoint Blocking and Ferroptosis.

The dynamic nature of noncovalent bonds in peptide self-assembly allows for selective accommodation of guest molecules. However, it remains unclear how to harness coassembly to reinforce the host peptides and simultaneously improve the application defects of guest molecules. This study aims to achieve supramolecular synergy between the host and guest, further expanding the functional space of the hybrid nanostructures. Herein, we utilized the aromatic regions present in β-sheet peptides to accommodate aromatic molecules, forming long-range nanotubes (NQ40@AIF) through a unique 'cross-strand π-π interlocking'. This strategy not only stabilizes the coassembly effectively but also synergizes the biological functions of the host and guest molecules. Moreover, due to the chemical diversity of the coassembled NQ40@AIF, it exhibits advantages in tumor combination therapy, achieving effective synergy between ferroptosis and immune checkpoint blocking. This work provides a minimalistic strategy for constructing peptide nanostructures with complex functionalities.

Exploring the role of graphene-metal hybrid nanomaterials as Raman signal enhancers in early stage cancer detection

Molecular diagnosis plays a significant role in detection of biomolecules linked to early stage cancer since it offers greater sensitivity and reliability for identification of biomarker level changes as the disease progresses. The application of vibrational spectroscopy in biomarker detection is defined by the fingerprint spectrum of a molecule originating from single-molecule vibrations. This characteristic makes surface enhanced Raman spectroscopy (SERS) a promising tool for identification of biomarkers. The performance of the SERS technique largely depends on the material being used as the SERS substrate. Graphene, with its large surface area and abundance of aromatic regions, is considered advantageous as SERS substrate. Combining graphene with metal nanomaterials considerably increases SERS signal intensity, thereby enhancing detection sensitivity. Therefore, this review emphasizes the significance of selecting graphene-metal nanohybrids as suitable SERS substrates for signal amplification. The detail understanding of the mechanism of graphene-metal hybrid in SERS based detection of early stage cancer is also presented. Furthermore, several examples demonstrated the application of graphene-metal hybrid nanomaterials in detecting biomarkers and cancer cell differentiation using SERS imaging.

2D Nitrogen-Doped Graphene Materials for Noble Gas Separation.

Noble gases, notably xenon, play a pivotal role in diverse high-tech applications. However, manufacturing xenon is an inherently challenging task, due to its unique properties and trace abundance in the Earth's atmosphere. Consequently, there is a pressing need for the development of efficient methods for the separation of noble gases. Using mild fluorographene chemistry, nitrogen-doped graphene (GNs) materials are synthesized with abundant aromatic regions and extensive nitrogen doping within the vacancies and holes of the aromatic lattice. Due to the organized interlayer "nanochannels", nitrogen functional groups, and defects within the two-dimensional (2D)structures, GNs exhibits effective selectivity for Xe over Kr at low pressure. This enhanced selectivity is attributed to the stronger binding affinity of Xe to GN compared to Kr. The adsorption is governed by London dispersion forces, as revealed by theoretical calculations using symmetry-adapted perturbation theory (SAPT). Investigation of other GNs differing in nitrogen content, surface area, and pore sizes underscores the significance of nitrogen functional groups, defects, and interlayer nanochannels over thesurface area in achieving superior selectivity. This work offers a new perspective on the design and fabrication of functionalized graphene derivatives, exhibiting superior noble gas storage and separation activity exploitable in gas production technologies.

Endocrine-Disrupting Effects of Salicylate Preservatives on Neurosteroidogenesis: Targeting 5α-Reductase Type 1.

Salicylate preservatives are widely used in consumer products and pharmaceuticals. This study investigates their potential endocrine-disrupting effects on neurosteroidogenesis, focusing on 5α-reductase type 1 (SRD5A1). We evaluated the effects of 13 salicylates on human SRD5A1 using SF126 glioblastoma cell microsomes and rat brain microsomes, examining dihydrotestosterone production in SF126 cells. Results revealed a hierarchy of inhibitory potency against human SRD5A1, with methyl salicylate (IC50, 71.93 μM) to menthyl salicylate (2.41 μM), indicating increasing potency. Kinetic analysis indicates their mixed/noncompetitive inhibitions. In SF126 cells, all salicylates at 100 μM significantly reduced dihydrotestosterone production. Rat SRD5A1 showed reduced sensitivity, with menthyl salicylate as the most potent inhibitor (IC50, 17.12 μM). Docking analysis suggests salicylates bind to the reduced nicotinamide adenine dinucleotide phosphate site of both human and rat SRD5A1. Bivariate correlation analysis highlights the influence of LogP, molecular weight, carbon number in the alcohol moiety, and pKa on inhibitory potency. 3D-QSAR revealed the importance of hydrophobic aromatic regions in SRD5A1 binding. This study delineates the inhibitory effects of salicylates and binding mechanisms on human and rat SRD5A1, providing insights into their impact on neurosteroid production.

Ligand-based pharmacophore modeling targeting the fluoroquinolone antibiotics to identify potential antimicrobial compounds

Antibiotic resistance presents a serious challenge to global healthcare, making the discovery of new therapeutic agents crucial. In this study, we used pharmacophore modeling and virtual screening to identify potential lead compounds against drug-resistant bacteria. We developed a shared feature pharmacophore (SFP) map using four antibiotics—Ciprofloxacin, Delafloxacin, Levofloxacin, and Ofloxacin—and generated a drug library of 160,000 compounds from ZINCPharmer based on these features, which included hydrophobic areas, hydrogen bond acceptors (HBA), hydrogen bond donors (HBD), and aromatic moieties (Ar). Through virtual screening, we identified 25 potential drug compounds as hits, with fit scores ranging from 97.85 to 116 and RMSD values from 0.28 to 0.63. These hits were then subjected to molecular docking against the DNA gyrase subunit A protein (PDB ID: 4DDQ), with ciprofloxacin as a control. The top five compounds—ZINC09133461, ZINC03791737, ZINC21983587, ZINC26469742, and ZINC26740199—achieved the highest docking scores, ranging from − 7.3 to − 7.4 kcal/mol and ciprofloxacin − 7.3 kcal/mol. After evaluating the drug-likeness of these compounds using Lipinski’s rule and analyzing their physicochemical properties, ZINC26740199 emerged as the most promising lead, offering hope in the fight against antibiotic resistance. Furthermore, molecular scaffold analysis revealed key similarities between ZINC26740199 and Ciprofloxacin, particularly in aromatic rings, hydrophobic regions, and hydrogen bond acceptors. These features suggest its potential as an effective antimicrobial agent, though further laboratory studies are needed to confirm its efficacy.

In vitro and In silico Antibacterial Evaluation of N-Methyl-2-phenylmaleimides

Background: Novel antibiotics are needed to stem the rise of antimicrobial resistance. N-Methyl-2-phenylmaleimide (NMP) compounds previously synthesised by our research group are structural analogues of 2,3,5-substituted perhydropyrrolo[3,4-d]isoxazole-4,6-diones found by others to have antibacterial activity. Objectives: This study aims to explain the significance of NMPs and their antibacterial activity. The antibacterial activity of the NMPs was determined against Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa. The partition coefficient of the NMPs and a pharmacophore model were used to explain their antibacterial activity. Methods: The Kirby Bauer Disc diffusion method was used to screen the NMPs for activity, while the broth microdilution method was used to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the active NMPs. Using the in vitro antibacterial activity of 2,3,5-substituted perhydropyrrolo[3,4-d]isoxazole-4,6-diones, a common feature pharmacophore model was constructed and validated. The rank score, fit value, enrichment factor (EF20%), and receiver operating characteristic area under the curve (ROC-AUC) were used as validation metrics. Results: The NMPs were only active against S. aureus, with compound 3 (4 µg/ml) being the most active. The majority of NMPs were bacteriostatic. A common feature pharmacophore model was validated (rank score: 120.5; fit value: 4; EF20%: 4.3; ROC-AUC: 0.9 ± 0.03) and showed that three hydrogen bond acceptors and a ring aromatic region are important for activity. Comparing the partition coefficient of the NMPs to their MIC a statistically significant correlation was found. Conclusion: NMPs can be used as lead compounds in future studies. The validated pharmacophore model and partition coefficient can be used to develop more active compounds.

Investigation on Tensile Properties of Polylactide-Nanoclay (PLA/ MMT) Surface Modification Nanocomposites

Polylactic acid (PLA) has gained significant attention as an environmentally friendly biopolymer, but its limited mechanical properties have hindered broader applications. Nanoparticles such as montmorillonite (MMT) offer a promising approach to address this limitation. The intercalation of MMT with polymer chains can significantly impact the mechanical properties of the nanocomposites. Hence, this paper investigated the effect of surface-modified montmorillonite (MMT) nanoparticles on the mechanical properties of polylactic acid (PLA) nanocomposites. The acetylation process of MMT was carried out followed by neutralisation process with NaOH. PLA granules and acetylated-modified MMT were mixed, crushed into granular form, and moulded. The effect of varying concentrations of modified MMTs on the tensile strength, elongation at break, and maximum force of PLA/MMT nanocomposites was evaluated using the ASTM D638 standard. FTIR results showed shifts in peak intensities in regions 2750 cm-1- 2810 cm-1 led to changes in the aliphatic and aromatic regions, which confirmed the presence of acetylation. Controlled surface modification improved interfacial interactions and load distribution, enhancing overall mechanical performance. The incorporation of surface-modified MMT in PLA/MMT nanocomposite increased the maximum force, Young's modulus, elongation at breaks and tensile strength. PLA/1wt% MMT and the PLA/7wt% MMT compositions exhibited good mechanical properties. However, the PLA/5 wt% MMT blendis deemed more suitable for food applications, such as disposable cups, plates, and cutleries, due to its lower elongation point. In conclusion, the hydrophilic properties of MMT and the hydrophobic properties of PLA are compatible due to the synergistic effects during surface modification which enhance the overall performance of the nanocomposites.

Unexpected Self-Assembly of Nanographene Oxide Membranes upon Electron Beam Irradiation for Ultrafast Ion Sieving.

Nanographene oxide (nGO) flakes-graphene oxide with a lateral size of ≈100nm or less-hold great promise for superior flux and energy-efficient nanofiltration membranes for desalination and precise ionic sieving owing to their unique high-density water channels with less tortuousness. However, their potential usage is currently limited by several challenges, including the tricky self-assembly of nano-sized flakes on substrates with micron-sized pores, severe swelling in aqueous solutions, and mechanical instability. Herein, the successful fabrication of a robust membrane stacked with nGO flakes on a substrate with a pore size of 0.22µm by vacuum filtration is reported. This membrane achieved an unprecedented water permeance above 819.1 LMH bar-1, with a high rejection rate of 99.7% for multivalent metal ions. The nGO flakes prepared using an electron beam irradiation method, have uniquely pure hydroxyl groups and abundant aromatic regions. The calculations revealed the strong hydrogen bonds between two nGO flakes, which arise from hydroxyl groups, coupled with hydrophobic aromatic regions, greatly enhance the stability of stacked flakes in aqueous solutions and increase their effective lateral size. The research presents a simple yet effective approach toward the fabrication of advanced 2D nanographene membranes with superior performance for ion sieving applications.

Unveiling the Intermolecular Interactions between Drug 5-Fluorouracil and Watson-Crick/Hoogsteen Base Pairs: A Computational Analysis.

The adsorption of 5-fluorouracil (5FU) on Watson-Crick (WC) base pairs and Hoogsteen (HT) base pairs has been studied using the dispersion-corrected density functional theory (DFT). The adsorption, binding energy, and thermochemistry for the drug 5FU on the WC and HT base pairs were determined. The most stable geometries were near planar geometry, and 5FU has a higher preference for WC than HT base pairs. The adsorption energies of 5FU on nucleobase pairs are consistently higher than pristine nucleobase pairs, indicating that nucleobase pair cleavage is less likely during the adsorption of the 5FU drug. The enthalpy change for the formation of 5FU-DNA base pairs is higher than that for the formation of 5FU-nucleobases and is enthalpy-driven. The E gap of AT base pairs is higher, suggesting that their chemical reactivity toward further reaction would be less than that of GC base pairs. The electron density difference (EDD) analysis shows a significant decrease in electron density in aromatic regions on the purine bases (adenine/guanine) compared to the pyrimidine bases. The MESP diagram of the stable 5FU-nucleobase pair complexes shows a directional interaction, with the positive regions in a molecule interacting with the negative region of other molecules. The atoms in molecule analysis show that the ρ(r) values of C=O···H-N are higher than those of N···H/N-H···O. The N···H intermolecular bonds between the base pair/drug and nucleobases are weak, closed shell interactions and are electrostatic in nature. The noncovalent interaction analysis shows that several new spikes are engendered along with an increase in their strength, which indicates that the H-bonding interactions are stronger and play a dominant role in stabilizing the complexes. Energy decomposition analysis shows that the drug-nucleobase pair complex has a marginal increase in the electrostatic contributions compared to nucleobase pair complexes.

The Metabolic and Antioxidant Activity Profiles of Aged Greek Grape Marc Spirits.

In the last decade, "expressions" of grape marc spirits aged in wooden barrels of characteristic amber color and complex sensory attributes have been introduced. Yet studies on constituents migrating from the barrel to the beverage are scarce, and their metabolic profile remains unexplored. Furthermore, the literature on the assessment of their antioxidant activity is limited. NMR metabolomics and spectrophotometry have been implemented in 38 samples to elucidate the impact of the aging procedure on the metabolites' composition and establish whether these beverages exhibit antioxidant activity. Provenance was related to fusel alcohols, esters, acetaldehyde, methanol, saccharides, and 2-phenylethanol, while ethyl acetate and ethyl lactate contributed to discriminating samples of the same winery. Identified metabolites such as vanillin, syringaldehyde, and sinapaldehyde were related to the aging procedure. The maturation in the barrel was also associated with an increase in xylose, glucose, fructose, and arabinose. The antioxidant potential of the aged Greek grape marc spirits resulting from their maturation in oak barrels was highlighted. The metabolic profiling and antioxidant potential of aged Greek grape marc spirits were assessed for the first time. Finally, the enrichment of the aromatic region was noted with the presence of metabolites with a furanic and phenolic ring derived, respectively, from the polysaccharides' degradation or the thermal decomposition of lignin.

AM404 Analogs as Activators of the 20S Isoform of the Human Proteasome.

The proteasome is a multisubunit protease system responsible for the majority of the protein turnover in eukaryotic organisms. Dysregulation of this enzymatic complex leads to protein accumulation, subsequent aggregation, and ultimately diseased states; for that reason, positive modulation of its activity has been recently investigated as a therapeutic strategy for neurodegenerative and age-related diseases. The small molecule AM404 was recently identified as an activator of the 20S isoform of the proteasome and further exploration of the scaffold revealed the importance of the polyunsaturated fatty acid chain to elicit activity. Herein, we report the investigation of the aromatic region of the scaffold and the evaluation of the small molecules in a variety of proteasome activity and protein degradation assays. We found that derivatives A22 and A23, compared to AM404, exhibit enhanced proteasome activity in biochemical and cellular proteasome assays and more favorable cellular viability profiles. Additionally, these compounds demonstrate the ability to degrade intrinsically disordered proteins, regardless of their molecular weight, and the ability to restore the proteasome activity in the presence of toxic oligomeric α-Syn species in a biochemical setting.

Unraveling the influence of aromatic endcaps in peptide self-assembly

Aromatic peptides are an emerging class of building units for molecular self-assembly and creation of functional biomaterials. The strength of aromatic association plays an essential role in the self-assembly of aromatic peptides. Here, we design a series of aromatic peptides with different hydrophobic domains but the same peptide sequence. The hydrophobicity and aromaticity can be carefully regulated by the number of benzene rings and the alkyl spacer between the benzene and peptide regions. Upon the continuous enhancement of aromaticity, diverse supramolecular nanostructures, including nanotubes, nanofibers, and short helical ribbons, were clearly observed. The peptide with diphenyl groups exhibits the highest regularity of molecular packing, due to the synergy of force balance between hydrogen bonding and π–π interactions. In addition, the incorporation of a spacer in between the aromatic and peptide regions facilitates the self-assembly capability, as the interference between aromatic association and hydrogen bonding is hindered. These dramatic results demonstrate that aromaticity serves as an effective and robust parameter in the molecular arrangement, providing a new perspective into the formation and evolution of supramolecular assembly.

(Invited) In-Operando ftir Study on the Redox Behavior of Sulfurized Polymers As Cathode Material for Li-S Batteries

Sulfurized polymers are an attractive cathode active material, promising to overcome the intransigent polysulfide shuttle effect sulfur cathodes face via the anchoring of sulfur by a carbon-sulfur (C-S) bond. Both sulfur-diisopropenylbenzene copolymers (SDIB) and sulfurized polyacrylonitrile (SPAN) contain C-S bonds which should function in this way, however, their performance in ether electrolytes still exhibit capacity fade associated with the polysulfide shuttle. We investigate this anchoring effect using in-operando ATR-FTIR spectroscopy to develop a molecular level understanding of the polysulfide speciation reaction in sulfurized polymers and cathode level molecular changes. We find that in SDIB copolymers with sulfur wt % of 80 and 30 wt %, the C–S bond is not active in the voltage window of Li–S batteries (1.8-2.6V vs Li/Li+).In SPAN, however, we found that the C-S bond is active in the typical voltage window (1-3V vs Li/Li+) contributing to the evolution of polysulfide species in electrolyte with low concentrations of lithium nitrate (LiNO3), however this effect is mitigated when higher concentrations of LiNO3 are used. We attributed the mitigation of the polysulfide shuttle to the formation of a cathode electrolyte interface (CEI), composed of lithium fluoride, established via ex-situ XPS studies on cycled cathodes. Additionally, we observed the reversible behavior of the C-S bond in IR at ~680 cm-1 in electrolytes with high concentration of LiNO3, as opposed to the irreversible behavior of the bond in electrolyte with low concentrations of LiNO3. Moreover, we observed the lithiation of the cyclized PAN backbone, identified by the elimination of the aromatic region of the IR spectrum after the first cycle.

Bisphenol a alternatives suppress human and rat aromatase activity: QSAR structure-activity relationship and in silico docking analysis

The use of alternative substances to replace bisphenol A (BPA) has been encouraged. The objective of this study was to evaluate the effects of BPA and 9 BPA alternatives on human and rat aromatase (CYP19A1) in human and rat placental microsomes. The results revealed that bisphenol A, AP, B, C, E, F, FL, S, and Z, and 4,4′-thiodiphenol (TDP) inhibited human CYP19A1 and bisphenol A, AP, B, C, FL, Z, and TDP inhibited rat CYP19A1. The IC50 values of human CYP19A1 ranged from 3.3 to 172.63 μM and those of rat CYP19A1 ranged from 2.20 to over 100 μM. BPA alternatives were mixed/competitive inhibitors and inhibited estradiol production in BeWo placental cells. Molecular docking analysis showed that BPA alternatives bind to the domain between heme and steroid and form a hydrogen bond with catalytic residue Met374. Pharmacophore analysis showed that there were one hydrogen bond donor, one hydrophobic region, and one ring aromatic hydrophobic region. Bivariate correlation analysis showed that molecular weight, alkyl atom weight, and LogP of BPA alternatives were inversely correlated with their IC50 values. In conclusion, BPA alternatives can inhibit human and rat CYP19A1 and the lipophilicity and the substituted alkyl size determines their inhibitory strength.

An alternative route for tricyclic quinazolinone-iminosugars and their glucosidase inhibitory activities

A series of novel tricyclic quinazolinone-iminosugars 5 and their derivatives 7 were obtained from the tosylated sugars by three steps. Firstly, the reaction of the isopropylidene protected sugar tosylate 1 and o-aminobenzylamine 2 generated the precursor tricyclic quinazolin-iminosuar 3, which was then oxidized by KMnO4 to produce the corresponding quinazolinone 4. Finally, removal of the isopropylidene group yielded the target tricyclic quinazolinone iminosugars 5. In addition, quinazolinone-iminosugars 4ac, 4bc and 4cc who contain bromine in the aromatic region underwent Suzuki reaction with phenylboronic acid, followed with the removal of the isopropylidene group to afford the derivatives 7. This strategy will help to construct such fused multicyclic quinazolinone-iminosugars efficiently. Some compounds show certain inhibition against α-glucosidase (saccharomyce cerevisiae).

Novel insight into structure and content of olefins in thermally cracked heavy oil and its saturates, aromatics, resins and asphaltenes fractions determined by 1H NMR spectroscopy

The factors leading to olefinic hydrogen signal shielding in the 1H NMR spectra of thermally cracked vacuum residue (VR) and its heavy fractions were revealed using a series of model compound systems, and the effect of olefinic hydrogen signal shielding on the determination of olefinic hydrogen content was elucidated. There were two main factors leading to the olefinic hydrogen signal shielding in the 1H NMR spectra of olefins in heavy fractions, i.e. intramolecular and intermolecular. For the olefin itself in heavy fractions, the chemical shift of the olefinic hydrogen closest to the aromatic ring was in the aromatic region rather than the olefinic region due to the π-π conjugation effect between the double bond and the intramolecular aromatic ring. Notably, the response intensity of the olefinic hydrogen signal could be weakened or even disappear due to the suppressive effect of the intermolecular aromatic structures in other polycyclic aromatic hydrocarbons (PAHs), while alkanes and monocyclic aromatics had little effect on the olefinic hydrogen signal response. Although the olefinic hydrogen signal was detected merely at about 5.30 ppm in the 1H NMR spectra of heavy fractions, these olefinic structures may be predominantly of the R─CH═CH2 type rather than the R─CH═CH─R′ type. More importantly, the measured olefinic hydrogen content of thermally cracked VR and its heavy fractions may be considerably lower than the actual content, with the measured content being only about 30–40 % of the actual content. This is mainly due to the weakening and disappearance of the olefinic hydrogen signal, coupled with the fact that the integral area of the possible olefinic hydrogen signal in the aromatic region was overlooked when calculating the total integral area of the olefinic hydrogen signal in the 1H NMR spectrum.

Small conformational changes in IgG1 detected as acidic charge variants by cation exchange chromatography

Fully characterizing the post-translational modifications present in charge variants of therapeutic monoclonal antibodies (mAbs), particularly acidic variants, is challenging and remains an open area of investigation. In this study, to test the possibility that chromatographically separated acidic fractions of therapeutic mAbs contain conformational variants, we undertook a mAb refolding approach using as a case study an IgG1 that contains many unidentified acidic peaks with few post-translational modifications, and examined whether different acidic peak fractions could be generated corresponding to these variants. The IgG1 drug substance was denatured by guanidine hydrochloride, without a reducing agent present, and gradually refolded by stepwise dialysis against arginine hydrochloride used as an aggregation suppressor. Each acidic chromatographic peak originally contained in the IgG1 drug substance was markedly increased by this stepwise refolding process, indicating that these acidic variants are conformational variants. However, no conformational changes were detected by small-angle X-ray scattering experiments for the whole IgG1, indicating that the conformational changes are minor. Chromatographic, thermal and fluorescence analyses suggested that the conformational changes are a localized denaturation effect centred around the aromatic amino acid regions. This study provides new insights into the characterization of acidic variants that are currently not fully understood.

Colorimetric Chemosensor for Cu2+ and Fe3+ Based on a meso-Triphenylamine-BODIPY Derivative.

Optical chemosensors are a practical tool for the detection and quantification of important analytes in biological and environmental fields, such as Cu2+ and Fe3+. To the best of our knowledge, a BODIPY derivative capable of detecting Cu2+ and Fe3+ simultaneously through a colorimetric response has not yet been described in the literature. In this work, a meso-triphenylamine-BODIPY derivative is reported for the highly selective detection of Cu2+ and Fe3+. In the preliminary chemosensing study, this compound showed a significant color change from yellow to blue-green in the presence of Cu2+ and Fe3+. With only one equivalent of cation, a change in the absorption band of the compound and the appearance of a new band around 700 nm were observed. Furthermore, only 10 equivalents of Cu2+/Fe3+ were needed to reach the absorption plateau in the UV-visible titrations. Compound 1 showed excellent sensitivity toward Cu2+ and Fe3+ detection, with LODs of 0.63 µM and 1.06 µM, respectively. The binding constant calculation indicated a strong complexation between compound 1 and Cu2+/Fe3+ ions. The 1H and 19F NMR titrations showed that an increasing concentration of cations induced a broadening and shifting of the aromatic region peaks, as well as the disappearance of the original fluorine peaks of the BODIPY core, which suggests that the ligand-metal (1:2) interaction may occur through the triphenylamino group and the BODIPY core.

Response of oxidized asphaltene aggregations in presence of rejuvenators and characteristics of molecular assembly behavior

In this work, a high quantum level of density functional theory (DFT-D) approach and fourier transform infrared spectrum (FTIR) at a micro-level were used to understand one phenomenon: the specific molecular mechanisms responsible for the deagglomeration effect of 10 kinds of representative molecules of bio- and petroleum-based rejuvenators on asphaltene aggregations found in the aged asphalt. The DFT results indicated that the action site of rejuvenators in sulfoxide group (S = O) position was bound stronger than those in carbonyl (C = O) and pyridine nitrogen. Compared with petroleum-based rejuvenators, bio-rejuvenators were responsible for significant contribution to the deagglomeration process when they were adequately inserted into the oxidized asphaltene dimer. Especially, 2-methoxyphenol (phenolic compounds) showed significantly higher efficiency than either of them. The deagglomeration behavior was mainly attributed to a new interaction (hydrogen-bonds of O-H··O/N-H··O and dispersion-attraction) of a series of competing factors between the rejuvenators and the asphaltenes. This polarized the charge distribution throughout the aromatic region of the asphaltene dimer and built up a multi-centered electron density (such as a three-center four-electron H-bond), thus destroying eventual interactions between asphaltene stacks and reducing the extent of clustering of asphaltene units that were intensified during oxidative aging. The FTIR data painted a preliminary picture of the hybrid rejuvenator-asphaltene as aromatic cores with shorter aliphatic side chains and more carbonyl and hydroxyl side groups, and showed the absence of chemical bonding interaction between the rejuvenators and asphaltene nanoclusters.