Molecular Aggregates Research Articles

Molecular Aggregations in Crystals of Butene Isomers Determined at High Pressure

Molecular Aggregations in Crystals of Butene Isomers Determined at High Pressure

Enhancing Near-Infrared Photothermal Performance by Molecular Aggregation Optimization in Semiconductive Coordination Polymers.

Near-infrared (NIR) photothermal conversion materials have recently received widespread attention due to their potential in diverse applications. However, highly efficient organic-based NIR photothermal agents remain limited. Developing strategies to enhance the efficiency of NIR photothermal materials and elucidating the relationship between the NIR photothermal performance and molecular aggregation are highly desired. Herein, we report two coordination polymers {[Cd2(ONDI)(ox)]·2/3(H2O)}n (1) and [Ba(ONDI)(H2O)2]n (2), in which the ONDI2- ligands assemble into different π-π stacking arrangements. Compound 1 exhibits H-aggregation, while compound 2 displays X-aggregation. The X-aggregation in compound 2 extends the optical absorption into the NIR region and enhances the absorption intensity. Consequently, compound 2 demonstrates a 1.8-fold increase in NIR photothermal efficiency (68.6%) compared to compound 1 (38.8%), attributed to more effective π-π interactions in X-aggregation. In addition, both compounds show semiconductive properties, with conductivities of 2.1 × 10-7 S/cm for compound 1 and 3.0 × 10-7 S/cm for compound 2 at 30 °C in a nitrogen atmosphere. These properties arise from the synergistic effects of "band-like" charge transport within crystals and "hopping" charge transport across grain boundaries. By integration of their NIR photothermal effects and semiconductive properties, compounds 1 and 2 show interesting NIR photoelectrical responses.

Effect of transglutaminase cross-linking on the structure and emulsification performance of heated black bean protein isolate.

Transglutaminase (TGase) is a heat-resistant biocatalyst with strong catalytic activity, which functions effectively under moderate temperature and pH conditions, and is used widely in protein cross-linking and recombination. Transglutaminase cross-linking is a novel and specific modification method for black bean protein isolate (BBPI). This article investigates the effect of transglutaminase cross-linking on the structure and emulsification performance of heated BBPI. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed that heated BBPI with TGase had a higher molecular weight than heated BBPI without TGase, and the protein bands widened with increasing enzyme activity, indicating that TGase cross-linking promoted protein molecule aggregation. A high molecular weight polymer can better stabilize the oil-water interface, preventing the emulsion from layering. Fourier transform infrared (FTIR) spectroscopy showed that the α-helix content decreased from 15.64% to 13.75%, and the β-sheet content increased from 48.13% to 54.08%. The decrease in α-helix content and increase in β-sheet content could make the structure more stable and improve the emulsifying properties of heated BBPI. When TGase was 20 U g-1, the protein emulsification activity index (EAI) reached its highest value of 1.87 m2 g-1, and the emulsification stability index (ESI) value was 0.27 min (P < 0.05); these figures were 0.19 m2 g-1, and 0.07 min higher, respectively, than in the sample without added TGase. In summary, transglutaminase cross-linking has a positive effect on the structure and emulsification performance of heated BBPI and can be used as an effective method for BBPI modification. © 2024 Society of Chemical Industry.

Terminal Fluorination Modulates Crystallinity and Aggregation of Fully Non‐Fused Ring Electron Acceptors for High‐Performance and Durable Near‐Infrared Organic Photodetectors

High dark current density (Jd) severely hinders further advancement of near‐infrared organic photodetectors (NIR OPDs). Herein, we tackle this grand challenge by regulating molecular crystallinity and aggregation of fully non‐fused ring electron acceptors (FNREAs). In contrast to the general trend in terminal halogenation of electron acceptors, TBT‐V‐F, featuring fluorinated terminals, notably demonstrates crystalline intensification and a higher prevalence predominance of J‐aggregate compared to its chlorinated counterpart (TBT‐V‐Cl). The amalgamation of advantages confers TBT‐V‐F‐based OPDs with more organized active layer morphology and denser molecular packing, resulting in improved charge transport, decreased energetic disorder, and reduced trap density. Consequently, the corresponding self‐powered OPDs exhibit a 40‐fold decrease in Jd, a remarkable increase in detectivity (D*sh), faster response time, and superior thermal stability compared to TBT‐V‐Cl‐based OPDs. Further interfacial optimization results in an ultra‐low Jd of 7.30´10‐12 A cm‐2 with D*sh over 1013 Jones in 320‐920 nm wavelength and a climax of 2.2´1014 Jones at 800 nm for the TBT‐V‐F‐based OPDs, representing one of the best results reported to date. This work paves a compelling material‐based strategy to suppress Jd for highly sensitive NIR OPDs, while also illustrates the viability of FNREAs in construction of stable and affordable NIR OPDs for real‐world applications.

Host-Guest Adduct as a Stimuli-Responsive Prodrug: Enzyme-Triggered Self-Assembly Process of a Short Peptide Within Mitochondria to Induce Cell Apoptosis.

To address the issue of nonspecific biodistribution of a chemotherapeutic drug, stable [2]pseudorotaxane complexes (PK@CAOPP and PR@CAOPP) are used to demonstrate a proof of concept. Cationic -PPh3 + moiety in CAOPP allows specific localization of the PK@CAOPP/ PR@CAOPP in the mitochondrial membrane (MM). Electrostatic interaction between the cationic LysinePK or ArgininePR moiety and the negatively charged phosphoesterCAOPP functionality in CAOPP favours strong adduct formation. The ALP-induced hydrolytic cleavage of the phosphoester moiety in cancer cells triggers dephosphorylation and releases PK/ PR moiety from PK@CAOPP/PR@CAOPP. PK or PR, derived from the Phe-Phe dipeptide, formed fibril-like molecular aggregates in the MM to induce dysfunction, depolarization, ROS generation and apoptotic MCF7 cell death. Such phenomena were not observed in ALP-negative HEK293 normal cells. These propositions were confirmed through control studies using NBDK and PE, other guest molecules. Smaller size and inclusion of the short peptides (PK or PR) within the hydrophobic interior of CAOPP, were attributed to their stability in blood serum. Thus, we have demonstrated the use of supramolecular adducts as a potential therapeutic option for treating cancer cells without affecting healthy cells. The efficacy was also established with an in-vivo MCF7 tumour xenograft model using Balb/c nude mice.

Degradation Analysis of Exciplex-Based Organic Light-Emitting Devices Using Carbazole-Based Materials.

A spectral shift and new emission bands in the green and red regions have been observed in deep blue exciplex-based organic light-emitting diodes (OLEDs) using carbazole-based materials, namely, tris(4-carbazoyl-9-ylphenyl)amine (TCTA). To deeply understand the origin of these new bands, single-layer and bilayer TCTA-based OLEDs subjected to electrical and optical (ultraviolet (UV)) stresses were investigated by using various optical, electrical, morphological, and chemical measurements. The results showed that the stress-induced emission bands primarily originate from morphological changes rather than chemical changes. The accumulation of excitons in the TCTA layer induces molecular aggregation, leading to the formation of electrically active electronic states, namely, electroplexes and electromers, which lead to the appearance of additional emission bands in green and red regions. Impedance spectroscopy measurements on single-layer OLEDs complemented this study. The results showed that TCTA degradation affects charge injection and transport. It was concluded that the stress-induced emission bands are caused by aggregate domain formation and are closely linked to the formation of electrically active defects, which act as trap states for charge carriers in the TCTA band gap.

Embedded Many‐Body Green's Function Methods for Electronic Excitations in Complex Molecular Systems

ABSTRACTMany‐body Green's function theory in the GW approximation with the Bethe–Salpeter equation (BSE) provides a powerful framework for the first‐principles calculations of single‐particle and electron–hole excitations in perfect crystals and molecules alike. Application to complex molecular systems, for example, solvated dyes, molecular aggregates, thin films, interfaces, or macromolecules, is particularly challenging as they contain a prohibitively large number of atoms. Exploiting the often localized nature of excitation in such disordered systems, several methods have recently been developed in which GW‐BSE is applied to a smaller, tractable region of interest that is embedded into an environment described with a lower‐level method. Here, we review the various strategies proposed for such embedded many‐body Green's functions approaches, including quantum–quantum and quantum–classical embeddings, and focus in particular on how they include environment screening effects either intrinsically in the screened Coulomb interaction in the GW and BSE steps or via extrinsic electrostatic couplings.

Tuning molecular aggregation to enhance photovoltaic performance of polymers by isomerizing benzodithiophene moiety

Tuning molecular aggregation to enhance photovoltaic performance of polymers by isomerizing benzodithiophene moiety

Cosensitization of a Tetraethylene Glycol‐Substituted Unsymmetrical Zinc Phthalocyanine Sensitized Solar Cells with D131 Auxiliary Dye Exhibited Enhanced Efficiency

AbstractAn asymmetric zinc phthalocyanine dye (ZnPcT3C), bearing three tetraethylene glycol donor groups and one carboxylic acid anchoring group, was synthesized as a photosensitizer dye for dye‐sensitized solar cells (DSSCs). The tetraethylene glycol (TEG), consisting of four ethoxy units, works as an amphiphilic long‐chain donor group that greatly helped in reducing the molecular aggregation. Carboxylic acid group, on the other hand, an acceptor, together with TEG in ZnPcT3C functions as a ‘push–pullʼ system suitable for DSSCs. Absorption spectra of ZnPcT3C in DMSO showed a strong sharp Q band in the infrared region 600–700 nm with (λmax = 682 nm) and a less intense soret band appeared in the region 300–400 nm with λmax = 340 nm. The zinc phthalocyanine (ZnPcT3C) exhibited molar extinction coefficient (ε) of 72,727 L mol−1cm−1. The emission was observed at λem = 695 nm upon excitation at 650 nm and exhibited a fluorescence decay of 2.82 ns. The ZnPcT3C dye sensitised solar cell (c = 1 mM) exhibited the power conversion efficiency (η) of 3.52% in chloroform in I−/I3 electrolyte under simulated 100% brightness. Cosensitization of ZnPcT3C with another auxiliary dye D131 in 1:1 ratio in a cocktail‐type DSSC attained the power conversion efficiency of twice as high as η = 6.27% in an identical condition. A mixture of D131 (λmax = 470 nm) dye with the ZnPcT3C phthalocyanine harvests sunlight across the visible spectra, enabling DSSCs to attain a large photocurrent and photovoltage, enhancing power conversion efficiency.

Regulation on Aggregation Behavior and In Vitro Digestibility of Phytic Acid-Whey Protein Isolate Complexes: Effects of Heating, pH and Phytic Acid Levels.

The impact of heat treatment, pH and phytic acid (PA) concentration on the aggregation behavior and digestibility of whey protein isolate (WPI) was investigated. The experimental results indicated that below the isoelectric point of WPI, heat treatment and elevated PA levels significantly increased turbidity and particle size, leading to the aggregation of WPI molecules. No new chemical bonds were formed and the thermodynamic parameters ΔH < 0, ΔS > 0 and ΔG < 0 suggested that the interaction between PA and WPI was primarily a spontaneous electrostatic interaction driven by enthalpy. After the small intestine stage, increasing phytic acid levels resulted in a significant decrease in hydrolysis degree from 16.2 ± 1.5% (PA0) to 10.9 ± 1.4% (0.5% PA). Conversely, above isoelectric point of WPI, there was no significant correlation between the presence of PA and the aggregation behavior or digestion characteristics of WPI. These results were attributed to steric hindrance caused by PA-WPI condensates, which prevented protease binding to hydrolysis sites on WPI. In summary, the effect of PA on protein aggregation behavior and digestive characteristics was not simply dependent on its presence but largely on the aggregation degree of PA-WPI induced by heat treatment, pH and PA concentration. The findings obtained here suggested that phytic acid may be utilized as an agent to modulate the digestion characteristics of proteins according to production requirements. Additionally, the agglomerates formed by heating phytic acid and protein below the isoelectric point could also be utilized for nutrient delivery.

Non‐Fused Star‐Shape Giant Trimer Electron Acceptors for Organic Solar Cells with Efficiency over 19 %

AbstractOrganic solar cells (OSCs) based on giant molecular acceptors (GMAs) have attracted extensive attention due to their excellent power conversion efficiency (PCE) and operation stability. However, the large conjugated plane of GMAs poses great challenges in regulating the solubility, over‐size aggregation and yield, which in turn further constrains their development in commercial products. Herein, we employ a non‐fused skeleton strategy to develop novel non‐fused star‐shape trimers (3BTT6F and 3BTT6Cl) for improving device performance. Single‐bond linkage can break the rigid planarity to form a 3D architecture, generating multidimensional charge transfer pathways. Importantly, the non‐fused skeleton strategy can not only significantly improve solubility and synthesis yield, but also effectively suppress molecular excessive aggregation. Consequently, due to the optimized film‐forming process and charge dynamics, 3BTT6F‐based binary device obtains a high PCE of 17.52 %, which is significantly higher than the reported fully fused trimers. Excitingly, 3BTT6F‐based ternary device even obtains a top‐level PCE of 19.26 %. Furthermore, the non‐fused star‐shape configuration also endows these acceptors with enhanced intermolecular interaction in the active layer, demonstrating excellent operational stability. Our work emphasizes the potential of non‐fused star‐shape trimers, providing a new pathway for achieving highly efficient and stable OSCs.

Benchmarking luminescent properties of the arylvinylpyrimidine scaffold.

The exploration of the photophysical properties of push-pull molecules incorporating pyrimidine rings as electron-attracting moieties in their structure continues to be a fascinating area of investigation. A thorough examination of these properties not only contributes to fundamental knowledge but also provides crucial insights for the rational design of emissive materials in prospective applications. In this context, this work conducts an in-depth analysis of four families of 4,6-bis(arylvinyl)pyrimidines, evaluating the influence of substituents on both the aryl groups and position 2 of the pyrimidine ring. While previous research has primarily focused on solution studies, this work emphasizes the importance of examining solid-state photophysics. Through a multidisciplinary approach encompassing optical techniques, x-ray diffraction, and quantum chemical calculations, a comprehensive understanding of the structure-property relationships is achieved. This study underscores the intricate interplay between molecular structure, aggregation, and fluorescence behavior in pyrimidines, offering valuable insights with broader implications beyond academic realms.

Comparison of Matrix Product State and Multiconfiguration Time-Dependent Hartree Methods for Nonadiabatic Dynamics of Exciton Dissociation.

The excited-state dynamics of organic molecules, molecular aggregates, and donor-acceptor clusters is typically governed by the interplay of electronic excitations and, due to their flexibility and soft bonding, by the interaction with their vibrations. This interaction in these systems can be characterized by a few relevant electronic states that are coupled to numerous vibrational normal modes, encompassing a vast configurational space of the molecules. The full quantum simulation of these type of systems has been long dominated by the multiconfiguration time-dependent Hartree (MCTDH) approach and its multilayer variants, which are considered the gold standard in the presence of electron-vibration coupling with a large number of modes. Recently, also the matrix product state ansatz (MPS) with appropriate time-evolution schemes has been applied to these types of Hamiltonians. In this article, we provide a numerical comparison of excited-state dynamics between the MCTDH and MPS approaches for two electron-vibration coupled systems. Notably, we consider two models for exciton dissociation at a P3HT:PCBM heterojunction, comprising two electronic states and 100 vibrational modes, and 26 electronic states and 113 vibrational modes, respectively. While both methods agree very well for the first model, more pronounced deviations are found for the second model. We trace back the divergence between the methods to the different way entanglement is treated.

Effect of CHAPS on the selective synthesis of (S)-n-octyl ibuprofen ester in AOT reverse micelle catalyzed by lipase

CHAPS (3-[(3-cholamidopropyl) dimethylammonio]-1-propane sulfonate), a biocompatible zwitterionic surfactant derived from bile salt, has attracted great attention due to its distinct molecular structure and aggregation behavior. Addition of a low level of CHAPS to AOT (sodium bis(2-ethylhexyl) sulfosuccinate) reverse micelles has been found to be able to enhance the catalytic activity of the solubilized lipase. In this study, the effect of CHAPS on the lipase-catalyzed selective synthesis of (S)-n-octyl ibuprofen ester was investigated in AOT reverse micelles at 37 °C. The results demonstrate that the presence of CHAPS in AOT reverse micelle enhances both the yield and the enantiomeric excess (ee) value of (S)-n-octyl ibuprofen ester, especially at low water content. With 8 mM CHAPS in AOT reverse micelle ([AOT] = 100 mM, [H2O]/[AOT] = 12, pH = 7.0), a 48-hour yield of 34.2 % could be obtained, which is approximately twice that without CHAPS. In addition, the ee value of the product is increased from 89.1 % to 98.2 %. To understand the mechanism of the CHAPS effect, dynamic light scattering, fluorescence emission spectroscopy and Fourier transform infrared spectroscopy techniques were used to characterize the size of the reverse micelle, the conformation of the solubilized lipase and the activity of the bulk water in the reverse micelle. It reveals that at low water content, the addition of CHAPS enlarges the size of AOT reverse micelle, stabilizes the lipase conformation and reduces the nucleophilicity of bulk water in AOT reverse micelle. The synergistic effect of the aforementioned factors results in the improvement of the enzymatic synthesis of the ester. The above research provides scientific support for the lipase-based preparation of chiral acids/alcohols in the reverse micellar system.

Indigestible proteins and peptide-bound AGEs in ultra-processed foods: Dulce de leche as a model of severely transformed protein food systems

Caramel milk confectioneries, such as dulce de leche, are produced by simmering whole or reconstituted milk with sugar and alkali at temperatures ranging from 115 to 130 °C for several hours. This process triggers extensive non-enzymatic browning through the Maillard reaction, leading to significant modifications in milk proteins. Our research focused on the effects of such severe processing conditions on the structural integrity and digestibility of milk proteins, using dulce de leche as a model for severely transformed food protein systems. Due to structural modifications, covalent interchain cross-links, and sugar-derived bridging moieties, milk proteins in dulce de leche form high molecular weight aggregates that are not resolvable by SDS-PAGE. Proteomic analysis revealed that all major milk proteins are involved in the formation of these covalent molecular complexes. When subjected to static gastro-duodenal digestion using both adult and infant models, these macroaggregates showed resistance to pepsin and marginal susceptibility to duodenal proteases. High pressure liquid chromatography-tandem mass spectrometry (HPLC-MS/MS)-based peptidomic analysis of dulce de leche digests allowed identifying variously sized polypeptides bearing the hallmarks of the Maillard reaction. However, many MS signals could not be assigned due to unknown modifications. The prevalence of free and peptide-bound advanced glycated end products (AGEs) in caramel milk products and other ultra-processed foods poses significant health concerns, stressing the need for a comprehensive dedicated evaluation.

Nonadiabatic dynamical simulations to the radiative recombination of nonfullerene acceptor molecular excited states.

Improving the radiative recombination rate of nonfullerene acceptor (NFA) molecular excited states can help to promote their photoluminescence quantum yield and thus reduce the nonradiative energy loss in NFA-based organic solar cells. In this Letter, by developing a nonadiabatic dynamical simulation method, we clarify quantitative correlations of some typical characteristics of NFA molecules with their radiative recombination rates. For a single NFA molecule, the weakening of electron-phonon coupling and the strengthening of electron-push-pull potential can each improve the radiative recombination rate. For different NFA molecular aggregates, their radiative recombination rates are all reduced compared with a single molecule, where the A-to-A and A-to-D type J-aggregates have higher rates than D-to-D type H-aggregate. To further improve the radiative recombination rate of NFA molecular J-aggregates, we should increase the intermolecular distance, such as extending the side chain length.

FMO-LC-TDDFTB method for excited states of large molecular assemblies in the strong light-matter coupling regime.

We present a new methodology to calculate the strong light-matter coupling between photonic modes in microcavities and large molecular aggregates that consist of hundreds of molecular fragments. To this end, we combine our fragment molecular orbital long-range corrected time-dependent density functional tight-binding methodology with a generalized Tavis-Cummings Hamiltonian. We employ an excitonic Hamiltonian, which is built from a quasi-diabatic basis that is constructed from locally excited and charge-transfer states of all molecular fragments. To calculate polaritonic states, we extend our quasi-diabatic basis to include photonic states of a microcavity and derive and implement the couplings between the locally excited states and the cavity states and built a Tavis-Cummings Hamiltonian that incorporates the intermolecular excitonic couplings. Subsequently, we demonstrate the capability of our methodology by simulating the influence of the electric field polarization on the polaritonic spectra for a tetracene aggregate of 125 monomers. Furthermore, we investigate the dependence of the splitting of the upper and lower polaritonic branches on the system size by comparing the spectra of five different tetracene clusters. In addition, we investigate the polariton dispersion of a large tetracene aggregate for electric field polarizations in the x, y, and z directions. Our new methodology can facilitate the future study of exciton dynamics in complex molecular systems, which consist of up to hundreds of molecules that are influenced by strong light-matter coupling to microcavities.

Proteome Aggregation in Cells Derived from Amyotrophic Lateral Sclerosis Patients for Personalized Drug Evaluation.

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder that currently lacks effective therapy. Given the heterogeneity of clinical and molecular profiles of ALS patients, personalized diagnostics and pathological characterization represent a powerful strategy to optimize patient stratification, thereby enabling personalized treatment. Immortalized lymphocytes from sporadic and genetic ALS patients recapitulate some pathological hallmarks of the disease, facilitating the fundamental task of drug screening. However, the molecular aggregation of ALS has not been characterized in this patient-derived cellular model. Indeed, protein aggregation is one of the most prominent features of neurodegenerative diseases, and therefore, models to test drugs against personalized pathological aggregation could help discover improved therapies. With this work, we aimed to characterize the aggregation profile of ALS immortalized lymphocytes and test several drug candidates with different mechanisms of action. In addition, we have evaluated the molecular aggregation in motor neurons derived from two hiPSC cell lines corresponding to ALS patients with different mutations in TARDBP. The results provide valuable insight into the different characterization of sporadic and genetic ALS patients' immortalized lymphocytes, their differential response to drug treatment, and the usefulness of proteome homeostasis characterization in patients' cells.

Cation-Dependent Mixed Ionic-Electronic Transport in a Perylenediimide Small-Molecule Semiconductor.

A rapidly growing interest in organic bioelectronic applications has spurred the development of a wide variety of organic mixed ionic-electronic conductors. While these new mixed conductors have enabled the community to interface organic electronics with biological systems and efficiently transduce biological signals (ions) into electronic signals, the current materials selection does not offer sufficient selectivity towards specific ions of biological relevance without the use of auxiliary components such as ion-selective membranes. Here, we present the molecular design of an n-type (electron-transporting) perylene diimide semiconductor material decorated with pendant oligoether groups to facilitate interactions with cations such as Na+ and K+. Using the cyclic 15-crown-5 oligoether motif, we find that the resulting mixed conductor PDI-crown displays a strong dependence on the size of the electrolyte cation when tested in an organic electrochemical transistor configuration. In stark contrast to the low current response on the order of 1 μA observed with aqueous sodium chloride, a nearly 200-fold increase in current is observed with aqueous potassium chloride. We ascribe the high selectivity to extended molecular aggregation and therefore efficient charge transport in the presence of K+ due to a favourable sandwich-like structure between two adjacent 15-crown-5 motifs and the potassium ion.

Impact of Loss Mechanisms on Linear Spectra of Excitonic and Polaritonic Aggregates.

The presence of loss mechanisms governed by empirical timescales can profoundly affect the dynamics in molecular systems, leading to changes in their spectra. However, incorporation of these effects along with the system's interaction with the thermal dissipative environments proves to be challenging. In this work, we demonstrate the possibility of utilizing the recently developed path integral Lindblad dynamics (PILD) method to study the linear spectra of molecular aggregates. PILD presents a uniquely powerful simulation technique for retaining the effects of the vibrations in a numerically exact manner through the Feynman-Vernon influence functional while incorporating the effects of losses in an empirical manner using the Lindbald master equation. As illustrations of this technique, we provide examples taken from chiral excitonic and polaritonic aggregates for which we simulate both the absorption spectra and circular dichroism (CD) spectra. We demonstrate that the effect of loss on particular states can differ not just on the basis of the symmetries of the state but also on the basis of complicated "interactions" of the structured dissipative environments with the system and its loss mechanisms. Due to the different selection rules between the absorption and CD spectra and the relative intensities and broadening of the peaks, the two linear spectra together give an interesting insight into the contributions of the various eigenstates to the correlation functions. While the focus here is on linear spectroscopy, it should be possible in the future to use PILD to study multidimensional spectra under loss mechanisms as well.