Supramolecular Structures Research Articles

Synthesis, structure, theoretical calculation and photocatalytic property of a novel Mn(II) supra-molecular compound containing SCN- and 2,2′-bipyridine ligands

A novel supra-molecular compound [Mn(SCN)2(byp)2] 1 (byp = 2,2′-bipyridine) was synthesized under hydrothermal conditions. Noteworthily, the SCN- in the title compound is derived from the in situ reaction of salicylaldehyde thiosemicarbazone. X-ray single-crystal diffraction analysis shows compound 1 is only a mononuclear structure, but it is expanded into a 3D supramolecular structure via H-bonds and π···π stacking. Hirshfeld Surface analysis shows C⋯H, H⋯H and S⋯H interaction are the main contribution of intermolecular interactions in the formation of compound 1. All of title compounds were characterized by IR spectroscopy, elemental analysis, XRD, XPS and TG analysis. The energy framework of compound 1 is dominated by dispersion interaction. The photocatalytic degradation ability of compound 1 for methylene blue is verified by photocatalytic degradation experiments (pH = 4: 44.6 %; pH = 7: 76.2 %; pH = 10: 78.8 %). Furthermore, the potential photocatalytic mechanism of compound 1 is inferred by UV–vis absorption spectra and Mott–Schottky curve.

Molecular Machines that Facilitate Bacterial Outer Membrane Protein Biogenesis.

Almost all outer membrane proteins (OMPs) in Gram-negative bacteria contain a β-barrel domain that spans the outer membrane (OM). To reach the OM, OMPs must be translocated across the inner membrane by the Sec machinery, transported across the crowded periplasmic space through the assistance of molecular chaperones, and finally assembled (folded and inserted into the OM) by the β-barrel assembly machine. In this review, we discuss how considerable new insights into the contributions of these factors to OMP biogenesis have emerged in recent years through the development of novel experimental, computational, and predictive methods. In addition, we describe recent evidence that molecular machines that were thought to function independently might interact to form dynamic intermembrane supercomplexes. Finally, we discuss new results that suggest that OMPs are inserted primarily near the middle of the cell and packed into supramolecular structures (OMP islands) that are distributed throughout the OM.

Comparative characterization and dyeing properties of poly(ethylene terephthalate-co-polyethylene glycol) fibers and poly(ethylene terephthalate) fibers

A comparative characterization of poly(ethylene terephthalate-co-polyethylene glycol) (PCP) fibers was performed using various parameters, including chemical and supramolecular structures, thermal properties, and physical properties. Dynamic scanning calorimetry and X-ray diffraction analyses revealed that PCP exhibits a lower melting point, glass transition temperature, and crystallinity than PET. In terms of tensile properties, PCP exhibited reduced tensile strength but increased elongation at break, indicating enhanced toughness. Dyeing test results demonstrated that PCP fibers are disperse dyeable at lower temperatures and exhibited optimal dyeability at 100 °C, surpassing PET, without compromising leveling properties or color fastness. These findings underscore the potential for energy savings and process streamlining through atmospheric-pressure dyeing.

Strengthening the π-conjugation of lignin by constructing its ordered supramolecular structure

The π-conjugation system of lignin makes it one kind of multifunctional biopolymer with many remarkable features such as ultraviolet-shielding properties, photothermal conversion capability, and fluorescence performance. The quest for effective strategies to strengthen the π-conjugation of lignin is significantly important to the design and production of outstanding lignin-based materials. In this work, we strengthen the π-conjugation of lignin by transforming lignin raw materials from disordered aggregates into ordered lignin colloidal spheres (LCSs) through supramolecular self-assembly. Moreover, we explore the relationship between the conjugation of lignin and its supramolecular structure by comparing the LCSs with different sizes, functional group arrangements, and compactness. Results demonstrate that the conjugation is stronger in the LCSs that have more hydrophobic groups inside and higher density. The primary strengthening mechanism of lignin conjugation is that the ordered and compact supramolecular structure results in a shorter average distance between benzene rings and stronger π-π interaction compared with that of disordered and loose supramolecular structure. We further demonstrate the great ultraviolet-shielding property and photothermal conversion capability of LCSs in polymer films, in which LCSs exhibit improved application performances than that of lignin raw materials due to their strengthened conjugation.

Advanced porous covalent organic framework (COF) materials for the capture of alizarin dye and its derivatives from the aquatic environment

The effective removal of dye pollutants from water and wastewater is a key environmental challenge. The present study is developed to investigate alizarin (ALI) dye and its derivations, including Alizarin blue (ABL), Alizarin purpurin (APU), Quinalizarin (AQU), Alizarin cyanin (ACY), and Alizarin Red S (ARS) removal process from water and wastewater sources, using covalent organic frameworks (COFs) nanoadsorbents. Herein, we explore the process of how dye molecules are absorbed onto COFs with precise supramolecular structures. The molecular dynamics (MD) and well-tempered metadynamics (WTMtD) simulations are used to investigate this process in aqueous solution. From the results obtained, it is clear that the intermolecular van der Waals (vdw) and π-π interactions have a significant role on accelerating the interaction between dye molecules and the COF nanostructures. This ultimately leads to the creation of a stable dye-COF complex. The dye-adsorbent average interaction energy value reaches around APU-COF1=−604.34, AQU-COF1=-515.25, ABL-COF1=−504.74, ALI-COF1=−489.48, ARS-COF1=−475.81, ACY-COF1=−273.82, AQU-COF2=−459.76, ALI-COF2=−451.46, ABL-COF2=−405.90, APU-COF2=−367.55, ACY-COF2=−287.89, ARS-COF2=−210.63 kJ/mol for dye/COF1 and dye/COF2 complexes, respectively. The primary interaction between dye and COFs is attributed to the Lennard-Jones term, resulting from the formation of a strong π-π interaction between the dye molecules and the surface of the adsorbent. Overall, our simulations confirmed that the COF1 nanostructure is more effective than the COF2 nanostructure in removing alizarin dye and its derivatives. In this study, not only the performance of two COFs in removing alizarin dye and its derivatives has been compared, but also the possibility of removing alizarin dye and its derivatives with both COFs has been examined.

Sophisticated natural products as antibiotics.

In this Review, we explore natural product antibiotics that do more than simply inhibit an active site of an essential enzyme. We review these compounds to provide inspiration for the design of much-needed new antibacterial agents, and examine the complex mechanisms that have evolved to effectively target bacteria, including covalent binders, inhibitors of resistance, compounds that utilize self-promoted entry, those that evade resistance, prodrugs, target corrupters, inhibitors of 'undruggable' targets, compounds that form supramolecular complexes, and selective membrane-acting agents. These are exemplified by β-lactams that bind covalently to inhibit transpeptidases and β-lactamases, siderophore chimeras that hijack import mechanisms to smuggle antibiotics into the cell, compounds that are activated by bacterial enzymes to produce reactive molecules, and antibiotics such as aminoglycosides that corrupt, rather than merely inhibit, their targets. Some of these mechanisms are highly sophisticated, such as the preformed β-strands of darobactins that target the undruggable β-barrel chaperone BamA, or teixobactin, which binds to a precursor of peptidoglycan and then forms a supramolecular structure that damages the membrane, impeding the emergence of resistance. Many of the compounds exhibit more than one notable feature, such as resistance evasion and target corruption. Understanding the surprising complexity of the best antimicrobial compounds provides a roadmap for developing novel compounds to address the antimicrobial resistance crisis by mining for new natural products and inspiring us to design similarly sophisticated antibiotics.

Solvatomorphism in a series of copper(II) complexes with the 5-phenylimidazole/perchlorate system as ligands.

In the course of an investigation of the supramolecular behaviour of copper(II) complexes with the 5-phenylimidazole/perchlorate ligand system (`blend') remarkable solvatomorphism has been observed. By employing a variety of crystallization solvents (polar protic, polar/non-polar aprotic), a series of 12 crystalline solvatomorphs with the general formula [Cu(ClO4)2(LH)4]·x(solvent) have been obtained [LH = 5-phenylimidazole, x(solvent) = 3.3(H2O) (1), 2(methanol) (2), 2(ethanol) (3), 2(1-propanol) (4), 2(2-propanol) (5), 2(2-butanol) (6), 2(dimethylformamide) (7), 2(acetone) (8), 2(tetrahydrofurane) (9), 2(1,4-dioxane) (10), 2(ethyl acetate) (11) and 1(diethyl ether) (12)]. The structures have been solved using single-crystal X-ray diffraction and the complexes were characterized by thermal analysis and infrared spectroscopy. The solvatomorphs are isostructural (triclinic, P1), with the exception of compound 9 (monoclinic, P21/n). The supramolecular structures and the role of the various solvents is discussed. All potential hydrogen-bond functionalities, both of the [Cu(ClO4)2(LH)4] units and of the solvents, are utilized in the course of the crystallization process. The supramolecular assembly in all structures is directed by strong recurring Nimidazole-H...Operchlorate motifs leading to robust scaffolds composed of the [Cu(ClO4)2(LH)4] host complexes. The solvents are located in channels and, with the exception of the disordered waters in 1 and the diethyl ether in 12, participate in hydrogen-bonding formation with the [Cu(ClO4)2(LH)4] complexes, serving as both hydrogen-bond acceptors and donors (for the polar protic solvents in 2-6), or solely as hydrogen-bond acceptors (for the polar/non-polar aprotic solvents in 7-11), linking the complexes and contributing to the stability of the crystalline compounds.

Chemical Structure and Thermal Properties versus Accelerated Aging of Bio-Based Poly(ether-urethanes) with Modified Hard Segments.

Aging of polymers is a natural process that occurs during their usage and storage. Predicting the lifetime of polymers is a crucial aspect that should be considered at the design stage. In this paper, a series of bio-based thermoplastic poly(ether-urethane) elastomers (bio-TPUs) with modified hard segments were synthesized and investigated to understand the structural and property changes triggered by accelerated aging. The bio-TPUs were synthesized at an equimolar ratio of reagents using the prepolymer method with the use of bio-based poly(trimethylene ether) glycol, bio-based 1,3-propanediol, and hexamethylene diisocyanate or hexamethylene diisocyanate/partially bio-based diisocyanate mixtures. The polymerization reaction was catalyzed by dibutyltin dilaurate (DBTDL). The structural and property changes after accelerated aging under thermal and hydrothermal conditions were determined using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic mechanical thermal analysis (DMTA). Among other findings, it was observed that both the reference and aged bio-TPUs decomposed in two main stages and exhibited thermal stability up to approximately 300 °C. Based on the research conducted, it was found that accelerated aging impacts the supramolecular structure of TPUs.

1,3,5–2,4,6‐Functionalized Benzene Molecular Cage: An Environmentally Responsive Scaffold that Supports Hierarchical Superstructures

AbstractNew stimulus‐responsive scaffolds are of interest as constituents of hierarchical supramolecular ensembles. 1,3,5–2,4,6‐Functionalized, facially segregated benzene moieties have a time‐honored role as building blocks for host molecules. However, their user as switchable motifs in the construction of multi‐component supramolecular structures remains poorly explored. Here, we report a molecular cage 1, which consists of a bent anthracene dimer 3 paired with 1,3,5‐tris(aminomethyl)‐2,4,6‐triethylbenzene 2. As the result of the pH‐induced ababab↔bababa isomerization of the constituent‐functionalized benzene units derived from 2, this cage can reversibly convert between an open state and a closed form, both in solution and in the solid state. Cage 1 was used to create stimuli‐responsive hierarchical superstructures, namely Russian doll‐like complexes with [K⊂18‐crown‐6⊂1]+ and [K⊂cryptand‐222⊂1]+. The reversible assembly and disassembly of these superstructures could be induced by switching cage 1 from its open to closed form. The present study thus provides an unusual example where pH‐triggered conformation motion within a cage‐like scaffold is used to control the formation and disassociation of hierarchical ensembles.

1,3,5-2,4,6-Functionalized Benzene Molecular Cage: An Environmentally Responsive Scaffold that Supports Hierarchical Superstructures.

New stimulus-responsive scaffolds are of interest as constituents of hierarchical supramolecular ensembles. 1,3,5-2,4,6-Functionalized, facially segregated benzene moieties have a time-honored role as building blocks for host molecules. However, their user as switchable motifs in the construction of multi-component supramolecular structures remains poorly explored. Here, we report a molecular cage 1, which consists of a bent anthracene dimer 3 paired with 1,3,5-tris(aminomethyl)-2,4,6-triethylbenzene 2. As the result of the pH-induced ababab↔bababa isomerization of the constituent-functionalized benzene units derived from 2, this cage can reversibly convert between an open state and a closed form, both in solution and in the solid state. Cage 1 was used to create stimuli-responsive hierarchical superstructures, namely Russian doll-like complexes with [K⊂18-crown-6⊂1]+ and [K⊂cryptand-222⊂1]+. The reversible assembly and disassembly of these superstructures could be induced by switching cage 1 from its open to closed form. The present study thus provides an unusual example where pH-triggered conformation motion within a cage-like scaffold is used to control the formation and disassociation of hierarchical ensembles.

Production of lignin-containing nanocellulose from six types of unpretreated lignocellulosic biomass by a one-step process

Lignin-containing nanocellulose (LCN) shows great potential in the fabrication of high performance bio-based materials, and suitable raw materials may achieve the production of LCN in a more economical approach. Therefore, in this study, the morphology, chemical and supramolecular structure of six types of lignocellulosic biomass (Broussonetia papyrifera bark, moso bamboo, rattan, balsa wood, poplar wood and fir wood) were analyzed for the production of LCN by using pure oxalic acid dihydrate (OAD). The results revealed that BPBs is a natural available cellulose-rich materials with extremely high cellulose content, low lignin content, and loosely connected cellulose chains. Compared with the other five types of lignocellulosic biomass materials, the hydrolysis of BPBs without any pretreatments by using OAD produced higher yield of LCN with much more uniform size distribution and smaller size. LCN from BPBs had higher crystallinity and thermal stability than that from the other five lignocellulosic biomass. The finding in this study indicated that Broussonetia papyrifera bark without any pretreatment was a favored material for high yield production of LCN compared with the other woody materials, which provided an economically realizable method on the efficient and high yield production of LCN from unpretreated BPBs by using OAD hydrolysis.

The cyanobacterial protein VIPP1 forms ESCRT-III-like structures on lipid bilayers.

The biogenesis and maintenance of thylakoid membranes require vesicle-inducing protein in plastids 1 (VIPP1). VIPP1 is a member of the endosomal sorting complex required for transport-III (ESCRT-III) superfamily, whose members form diverse filament-based supramolecular structures that facilitate membrane deformation and fission. VIPP1 cryo-electron microscopy (EM) structures in solution revealed helical rods and baskets of stacked rings, with amphipathic membrane-binding domains in the lumen. However, how VIPP1 interacts with membranes remains largely unknown. Here, using high-speed atomic force microscopy (HS-AFM), we show that VIPP1 assembles into right-handed chiral spirals and regular polygons on supported lipid bilayers via ESCRT-III-like filament assembly and dynamics. VIPP1 filaments grow clockwise into spirals through polymerization at a ring-shaped central polymerization hub, and into polygons through clockwise polymerization at the sector peripheries. Interestingly, VIPP1 initially forms Archimedean spirals, which upon maturation transform into logarithmic spirals through lateral annealing of strands to the outermore low-curvature spiral turns.

Biostimulation of humic acids on Lepidium sativum L. regulated by their content of stable phenolic O⋅ radicals

BackgroundHumic acid affects plant growth. Its source and structure may play a central role to its functionality. The relationship between humic acid and plant bioactivity is still unclear. This study investigated the biostimulation effects of two natural humic acids derived from soil (SHA) and lignite (LHA) on Lepidium sativum in comparison to a synthetic humic acid model (HALP) with known structure.ResultsAll humic acids positively affected cress seed germination and root elongation. Greater root hairs density and dry matter, compared to control, were observed using concentration of 5 mg L−1 for HALP, 50 mg L−1 for LHA, and 100 mg L−1 for SHA. The germination index was the largest (698% more effective than control) with 50 mg L−1 of SHA, while it was 528% for LHA, and 493% for HALP at 5 mg L−1. SHA contained the lowest aromatic and phenolic C content, the largest pK2 value of 9.0 (7.7 for LHA and 7.6 for HALP), the least ratio between the aromaticity index and lignin ratio (ARM/LigR) of 0.15 (0.66 for LHA and 129.92 for HALP), and at pH 6.3 the lowest amount of free radicals with a value of 0.567 × 1017 spin g−1 (1.670 × 1017 and 1.780 × 1017 spin g−1 for LHA and HALP, respectively), with the greatest g value of 2.0039 (2.0035 for LHA and 2.0037 for HALP).ConclusionsThe overall chemical structure of humic acids exerted a biostimulation of cress plantlets. The level of the intrinsic stable free radicals identified by EPR in the humic acids resulted well correlated to the ARM/LigR ratio calculated by NMR. Our results suggested that HA biostimulation effect is related to its applied concentration, which is limited by its free radical content. The modulation of the humic supramolecular structure by ROS and organic acids in root exudates can determine the release of bioactive humic molecules. When the content of the intrinsic humic free radicals is high, possible molecular coupling of the bioactive humic molecules may hinder their biostimulation activity. In such cases, a low humic acid concentration appears to be required to achieve the optimum biostimulation effects.Graphical

Microfluidic-Assisted Self-Assembly of Molecular Hydrogelator at Water-Water Interfaces for Continuous Fabrication of Supramolecular Microcapsules.

Control over the self-assembly of small molecules at specific areas is of great interest for many high-tech applications, yet remains a formidable challenge. Here, how the self-assembly of hydrazone-based molecular hydrogelators can be specifically triggered at water-water interfaces for the continuous fabrication of supramolecular microcapsules by virtue of the microfluidic technique is demonstrated. The non-assembling hydrazide- and aldehyde-based hydrogelator precursors are distributed in two immiscible aqueous polymer solutions, respectively, through spontaneous phase separation. In the presence of catalysts, hydrazone-based hydrogelators rapidly form and self-assemble into hydrogel networks at the generated water-water interfaces. Relying on the microfluidic technique, microcapsules bearing a shell of supramolecular hydrogel are continuously produced. The obtained microcapsules can effectively load enzymes, enabling localized enzymatic growth of supramolecular fibrous supramolecular structures, reminiscent of the self-assembly of biological filaments within living cells. This work may contribute to the development of biomimetic supramolecular carriers for applications in biomedicine and fundamental research, for instance, the construction of protocells.

Multi-laser nanoparticle tracking analysis (NTA): A unique method to visualize dynamic (shear) and dynamic (Brownian motion) light scattering and quantify nonliving natural organic matter (NNOM) in environmental water

Application of simultaneous multi-laser nanoparticle tracking analysis (NTA) to environmental water samples to investigate nonliving natural organic matter (NNOM) is introduced as an innovative method for observing particles directly in their native media. Multi-laser NTA results of particle visualization, particle number concentration, and particle size distribution elucidated particle dynamics in low and high total dissolved solids (TDS) aqueous environmental samples. A pond water sample and concentrate from a reverse osmosis (RO) treatment process (Stage 1) had 1.3 × 108 and 5.62 × 1019 particles/mL, respectively, (at time = 0) after filtration at 0.45 μm. Beyond the traditional applications for this instrument, this research presents novel evidence-based investigations that probe the existence of supramolecular structures in environmental waters during turbulence or quiescence. The pond water sample exhibited time-dependent aggregation as the volume distribution shifted to greater diameter during quiescence, compared to turbulence. Disaggregation (increased numbers of particles over time) was noted in the >250 nm to <600 nm region, and aggregation of >450 nm particles was also noted in the quiescent RO concentrate sample, indicative of depletion of small particles to form larger ones. Multi-laser NTA and dynamic light scattering (DLS) capabilities were compared and contrasted. DLS and NTA are different (complementary) particle sizing techniques. DLS yielded more information about the physical hydrogel in the NNOM hierarchy whereas multi-laser NTA better characterized meta-chemical and chemical hydrogel characteristics. Operationalization of innovation—moving from fundamental investigations to application—is supported by implementing novel analytical instrumentation as we address issues involving climate change, drought, and the scarcity of potable water. Multi-laser NTA can be used as a tool to study and optimize complex water and wastewater treatment processes. Questions about water treatment efficiencies, membrane fouling, assistance of pollutant transport, and carbon capture cycles affected by NNOM will benefit from insights from multi-laser NTA.

Synthesis and characterization of Ketotifen Fumarate Intercalated Zn–Al Layered Double Hydroxides as sustained-release carriers

The present study seeks to synthesize, characterize, and sustain the release of properties of Ketotifen Fumarate Intercalated Zn–Al Layered Double Hydroxides (Zn-Al-KF-LDHs) by the chemical co-precipitation method. A variety of techniques were used to analyze the synthesized products, including Elemental Analysis, X-ray diffraction (XRD), Scanning electron microscope (SEM), Fourier Transform Infrared Spectroscopy (FT-IR), and Thermogravimetry Differential Thermal Analysis (TG-DTA). The XRD patterns successfully highlighted the remarkable crystallinity of the typical hydrotalcite-like materials, Zn-Al-KF-LDHs. While the FT-IR analysis indicates the chemical functional groups and interlayer anions of Zn-Al-KF-LDHs, the elemental analysis determines the content of Zn, Al, S, C, H, and N. The TG-DTA results show that Zn-Al-KF-LDHs possess improved thermal stability. These findings provide an empirical understanding of the supramolecular structure of Zn-Al-KF-LDHs, enabling its comprehensive structural analysis. Additionally, the sustained-release properties of simulated gastric juice and intestinal juice, which followed the theoretical models of Higuchi and Riger-Peppas, indicated that the layered double hydroxides have potential applications as sustained-release carriers for ketotifen fumarate.

Design, synthesis, crystal structure and anticancer activity of organotin(IV)-rhein carboxylates

Two new rhein-organotin complexes Ph3Sn(O2CC14H7O4) (RS01) and Cy3Sn(O2CC14H7O4) (RS02) were synthesized and characterized by elemental analysis, IR, 1H NMR, 13C NMR, 119 Sn NMR, X-ray crystallography and thermo-gravimetric analysis. Both complexes has a triclinic crystal system P-1 space group and one-dimensional supramolecular chain structure. The MTT results demonstrated that rhein's anticancer activity was effectively increased by introducing organotin, RS01 and RS02 exhibited excellent anticancer activity in vitro, significantly superior to cisplatin and mitoxantrone. Interestingly, despite the fact that RS01 and mitoxantrone share the same 9,10-anthraquinone scaffold structure, RS01 not only showed high anticancer activity but also much lower nephrotoxicity than mitoxantrone. Flow cytometry showed that RS01 could significantly induce cell apoptosis and arrest cell cycle in G2 phase. Molecular docking and UV–Vis absorption spectra suggested that RS01 may be intercalation with DNA. Furthermore, western blot results showed that RS01 activated the DNA damage critical protein γ-H2AX and regulated the expression level of the mitochondrial apoptotic pathway critical protein (Bax/Bcl-2). Thus, RS01 induced cell death may be mediated through DNA damage and mitochondrial pathways. As a result, RS01 has significant development and application potential as an anticancer agent.

Photocatalytic degradation of methyl orange by a Pt(II) complex under visible light irradiation

An extremely effective photocatalytic complex, PtLCl2 (1), was synthesized with (4-([2,2':6',2''-terpyridin]-4'-yl)phenyl)boronic acid as ligand and further characterized through single crystal X-ray diffraction, X-ray photoelectron spectroscopy and UV-vis spectrum. Multipoint hydrogen bonds and three kinds of π-π stacking interactions are observed in the supramolecular structure of 1. More significantly, the Pt(II) complex exhibits outstanding photocatalytic degradation efficiency (94.76%) for methyl orange within 120 min under visible light irradiation. The kinetic rate constant (k) for 1 (10 mg) is 0.02505 min−1, which is approximately 70 times higher than that of the ligand (0.00036 min−1). Moreover, its photocatalysis mechanism proposed that ·O2 − and h+ were the main active species for MO degradation, providing a great prospect for development of a new efficient photocatalytic complex.

Intrinsic Chiroptical Activity and Excitonic Properties of Group II-VI Magic-Size Clusters.

Semiconductor magic-size clusters (MSCs), lying in the local minima of the potential landscape, are important intermediates that emerge during the synthesis of colloidal quantum dots. They have definite geometrical and electronic structures, thus serving as atomically precise building blocks for assembling supramolecular structures and devices with unprecedented functionalities. Here we report the intrinsic chiroptical activity in the magic-size cadmium and zinc chalcogenide clusters with magic numbers of 13, 33, and 34 possessing unique core-shell structures. They are responsive to circularly polarized light from the ultraviolet to visible region, with size-tunable energy gap, absorption wavelength, and excitonic characteristics. The origin of the chiroptical activity and the evolution of excitonic states with magic size are disclosed by time-dependent density functional theory calculations within a correlated electron-hole picture. This molecular-level understanding of the photophysical properties of group II-VI MSCs provides essential guidelines for utilizing them for chiral optoelectronics and photonics.

Experimental Correlation between Apparent pKa and Gelation Propensity in Amphiphilic Hydrogelators Derived from l-Dopa.

We report the gelation propensity of three gelators derived from l-dihydroxyphenylalanine (l-Dopa), where the amino group is derivatized with three different fatty acids (lauric acid, palmitic acid, and azelaic acid). The long aliphatic side chains should introduce additional van der Waals interactions among the molecules, contributing to the self-assembly process. The hydrogels have been prepared with the pH change method, and both the hydrogels and the corresponding aerogels have been analyzed using several techniques. In any case, Lau-Dopa provides stronger hydrogels compared with the other gelators. This property may be ascribed to its tendency to efficiently form supramolecular β-sheet structures, as outlined by the ECD, IR, and SEM analyses. Moreover, the preliminary measurement of the apparent pKa displays for Lau-Dopa two plateaux, as previously observed for, one at about pH 12 and a second one at pH 7.5. Thus, its pKa results in two apparent pKa shifts of ∼8.5 and ∼4 pH units above the theoretical pKa, as a consequence of a multistep self-assembly pathway that correlates, in the final β-sheet-based hydrogel, with a high degree of order and stability.