Effect Of Intermolecular Interactions Research Articles

MolPackL: Quantification and Interpretation of Intermolecular Interactions Driven by Molecular Packing.

In organic optoelectronic devices, the properties of the aggregated organic materials depend not only on individual molecules or monomers but also significantly on their packing modes. Different from their inorganic counterparts linked by explicit covalent bonds, organic solids exhibit intricate and numerous intermolecular interactions (IMIs). Due to the intrinsic complexity and disorder of IMIs, identifying and understanding them is a formidable challenge in experimental, theoretical, and data-driven approaches. In this work, we constructed an innovative algorithm framework, Molecular Packing Learning (MolPackL), which can accurately quantify elusive IMIs using contact density histograms (CDHs) and efficiently extract intermolecular features for further property prediction of organic solids. It performs satisfactorily in training predictive models of IMI-related properties in molecular crystals. Particularly, the band gap predictive model based on MolPackL achieved the best-reported performance, with an MAE of 0.20 eV and an impressive R2 of 0.92. Class activation mapping (CAM) visually demonstrates MolPackL's accurate identification of effective interaction sites as the molecular packing changes. What is more, the elemental importance analysis verified that the superior score benefits from MolPackL's ability to comprehensively consider multiple influencing factors of IMIs. In summary, MolPackL provides a new framework for quantitative assessment and understanding of the effect of IMIs. The development of MolPackL marks a significant advancement in establishing predictive models of molecular aggregates, deepening the comprehension of IMIs on the material properties. Given the superior performance, we believe that MolPackL will also become a powerful tool in the design of high-performance organic optoelectronic materials.

First Principles Simulations of Optical Rotation of Chiral Molecular Crystals.

In this work, we present simulations of the optical rotation (OR) for five molecular crystals at density functional theory level with periodic boundary conditions (DFT-PBC). Calculations are compared with experimental measurements and show semi-quantitative agreement with experimental data for three of the crystals: tartatic acid, benzil, and pentaerythritol. For the other two crystals, aspartic acid and glutamic acid, the calculated data are in qualitative agreement with, but two orders of magnitude smaller than, the experimental data. We provide some arguments that support the theoretical predictions and suggest that the experiments should be revisited. We also find that the position of H centers provided in experimental X-ray data is not sufficiently reliable for simulating OR, and better results are obtained when H atoms are allowed to relax while keeping heavier elements fixed at the experimental positions. Comparison with molecular cluster calculations with a better functional and a larger basis set indicate that the role of intermolecular interactions (reproduced with the PBC technique) is as or more important than the choice of model chemistry. Despite the current limitations in the level of theory that can be employed, these simulations provide a promising avenue to investigate the effect of intermolecular interactions on this sensitive electronic property of molecules and materials.

Structural and Physiochemical Properties of Polyvinyl Alcohol-Succinoglycan Biodegradable Films.

Polyvinyl alcohol (PVA)-bacterial succinoglycan (SG) biodegradable films were developed through a solvent-casting method. Effects of the PVA/SG ratio on the thickness, transmittance, water holding capacity, and structural and mechanical properties were investigated by various analytical methods. All the prepared films were transparent and uniform, and XRD and FTIR analyses confirmed that PVA was successfully incorporated into SG. The films also showed excellent UV-blocking ability: up to close to 80% with increasing SG concentration. The formation of effective intermolecular interactions between these polymers was evidenced by their high tensile strength and moisture transport capacity. By measuring the biodegradation rate, it was confirmed that films with high SG content showed the fastest biodegradation rate over 5 days. These results confirm that PVA/SG films are eco-friendly, with both excellent biodegradability and effective UV-blocking ability, suggesting the possibility of industrial applications as a packaging material in various fields in the future.

Effect of intermolecular interactions and pharmacokinetic profile of antidiabetic agent (E)-N,N‑diethyl-2-(5(3‑hydroxy-4-methoxybenzylidene)-2,4-dioxothiazolidin-3-yl) acetamide

Diabetes is a prevalent disease in South India, posing a severe threat to public health. To tackle this issue, researchers are focusing on developing multi-targeted ligands, and one promising candidate is (E)-N,N‑diethyl-2-(5(3‑hydroxy-4-methoxybenzylidene)-2,4-dioxothiazolidin-3-yl)acetamide (DMDA). Geometry optimization of DMDA was carried out using density functional theory with 6–311+G(d, p) basis set to develop a theoretical model close to the previously synthesized and reported DMDA. Natural Bond Orbital analysis was conducted to scrutinize the phenomena of charge delocalization and electronic exchange interactions governing both intermolecular and intramolecular associations. Moreover, the vibrational characteristics of the molecule were elucidated through FT-IR and FT-Raman spectra. Lowest Unoccupied Molecular Orbital and Highest Occupied Molecular Orbital have also been explored to enhance understanding of the molecule's electronic structure and reactivity. Hirshfeld surface analysis was utilized to investigate the interactions between molecules within the crystalline lattice. Absorption, distribution, metabolism, excretion, and toxicity (ADMET) analysis elucidates the potential pharmacokinetic profile of DMDA. Molecular docking was performed to predict the binding site responsible for various interactions with the targeted protein. By combining these techniques, a comprehensive molecular description of DMDA has been generated.There are three prominent intramolecular interactions within the ambit of van der Waals radii, leading to stability of the molecule. The presence of a broad and shallow band with a significant red shift provides evidence for the strong intermolecular OH hydrogen bonding. DMDA complies with Lipinski's Rule of Five, highlighting its favorable characteristics for pharmaceutical efficacy. The negative binding energies determined by docking studies ascertain the potential sites of ligand-protein interaction leading to inhibition of α-amylase and α-glucosidase enzyme.

Strengthening Near‐Infrared Photon Harvesting in Semi‐Transparent All‐Polymer Solar Cells through the Synergy of Fluorination on the Selenide Monomer Backbone

AbstractAll‐polymer solar cells (all‐PSCs) offer promising potential for large‐scale manufacturing due to their remarkable mechanical and thermal stability. However, the limited capacity of polymer acceptors for near‐infrared (NIR) photon harvesting has impeded their progress in semi‐transparent (ST) all‐PSCs. Here, the study develops a pair of new NIR polymer acceptors, named PYSeF‐T and PYSe2F‐T, with mono‐/di‐fluorinated end groups capped to the selenide monomer backbone, respectively. Owing to the stronger intermolecular interaction and intramolecular charge transfer effect of the di‐fluorinated end groups with the selenide backbone, PYSe2F‐T exhibits a stronger crystallinity and a more bathochromic absorption to 1000 nm. When blended with the donor, PM6, the PY2SeF‐T‐based all‐PSC demonstrates a higher efficiency of 16.73% with a remarkable short‐circuit current (JSC) of 27.7 mA cm−2, which is the highest JSC for all‐PSCs. Based on these, the ST device based on PM6:PYSe2F‐T demonstrates a superior efficiency of 12.52% with an average visible transmittance of 26.2% and a light utilization efficiency of 3.28%, outperforming the mono‐fluorinated counterpart. The work provides an in‐depth understanding of the above synergistic effects to develop NIR polymer acceptors and establishes a solid foundation for future investigations into large‐area and flexible ST all‐PSCs.

Experimental and simulation study on the solubility of 1-naphthylamine in twelve neat solvents

To meet the demand of separating and purifying 1-naphthylamine from the reaction production and filling the solubility data gap, the solubility of 1-naphthylamine in twelve pure solvents (acetone, acetonitrile, ethyl acetate, n-butyl acetate, cyclohexane, n-heptane, methanol, ethanol, n-propanol, iso-propanol, n-butanol, and iso-butanol) was experimentally investigated in the range from 273.15 K to 308.15 K. It was found that the solubility of 1-naphthylamine increases markedly with increasing temperature in all solvent systems. The maximum solubility was 0.8978 (in the solvent of acetone,T = 308.15 K) and the minimum solubility was 0.005485 (in the solvent of n-heptane, T = 273.15 K). Then the experimental solubility data was correlated by the modified Apelblat model, Van't Hoff model, NRTL model, Wilson model, and Margules model. ARD% was calculated to assess the accuracy of the five equations and the results indicated that the modified Apelblat model fits optimally with an average ARD% value of 1.62 %. The effects of various physicochemical properties such as solvent polarity, hydrogen bond donor, hydrogen bond acceptor, and cohesive energy density on solute dissolution behavior were explored. In addition, the apparent thermodynamic properties of 1-naphthylamine in different solvents were analyzed based on modified Van’t Hoff model, which indicated the dissolution process of 1-naphthylamine in selected solvents is endothermic and entropy-driving. Finally, the effect of intermolecular interactions on the dissolution behavior was investigated at the molecular scale through molecular dynamics simulation studies, including molecular electrostatic potential surface, solvation free energy and radial distribution function analysis. This work will provide a fundamental guidance for the crystallization, separation, and purification of 1-naphthylamine.

Low‐Cost, Large‐Area, and Highly Transparent Organic Glassy Scintillators for High Resolution X‐Ray Imaging

AbstractThe architectural design and fabrication of low‐cost, high‐performance organic scintillators are critical for medical imaging and material/device analysis. However, achieving large‐area and high‐transparency organic scintillators in a low‐cost and easy‐to‐implement method remains a challenge. Herein, a new design strategy for regulating the side chain length of maleimide derivatives is demonstrated to develop organic scintillators for achieving low‐cost, large‐area, and high spatial resolution in X‐ray imaging. The effective intermolecular interactions and relatively twisted molecular structure endow PAM‐M4 molecule with outstanding scintillator properties. More importantly, as demonstrated for the first time, pure organic glassy films with a diameter over 10 cm and high optical transparency can be prepared by the developed melt‐quenched method using PAM‐M4 crystal powder as a raw material. This glassy film exhibits excellent X‐ray imaging ability with a spatial resolution as high as 27.0 lp mm−1 at MTF = 0.20, which is one of the best results among reported organic scintillators. The results of this work not only develop a new design strategy for high‐performance organic scintillators but also demonstrate a reliable approach to fabricating large area screens with superior spatial resolution for medical or industrial X‐ray imaging applications.

Experimental and molecular simulation analysis of the dissolution behavior of Musk ambrette in organic solvents

The solubility of Musk ambrette in i-propanol (IPA), i-butanol (IBA), n-heptane (HPT), n-hexane (HX), cyclohexane (CYH), methyl acetate (MAC), ethyl acetate (EAC), acetone (ACE), IPA + ACE at 278.15 K to 318.15 K was determined. The mole fraction solubility of Musk ambrette in pure IPA at the temperature of 298.15 K were found to be 0.9492 × 10-2 mol·mol−1. The difference is that the solubility of Musk ambrette in ACE reaches 0.2257 mol·mol−1, which is much higher than the solvent mentioned above. The strong intermolecular hydrogen bonding formed by IPA resulted in its lowest solvation capacity for Musk ambrette. In addition, to further investigate the solubility pattern of Musk ambrette, we used 8 models (Van’t Hoff, modified Apelblat, Buchowski-Ksiazczak, Yaws, NRTL, Wilson, Jouyban-Acree and Sun model) to fit and obtain a general equation for solubility versus temperature. These results yielded a large amount of statistically significant data. Comparisons revealed that the modified Apelblat and Yaws equation showed the least deviation in forecasting solubility variations with temperature. Meanwhile, we proved that the dissolution of Musk ambrette is a heat-absorbing entropy increasing process by Van't Hoff equation calculation. ΔsolGo for the 12 solvents is in the following order: ACE < MAC < EAC < w = 0.2007 < w = 0.4025 < w = 0.6076 < CYH < w = 0.8070 < HPT < HX < IBA < IPA. ΔsolGo is smaller the easier it dissolves, which is consistent with the law of dissolution. Secondly, we performed thermal analysis and X-ray diffraction tests on Musk ambrette crystals prepared in different solvents, which showed that none of the several systems investigated led to the creation of new crystalline forms or solvatoids, further confirming the suitability of the solvents. Besides, we discuss the correspondence between solubility and the HSP, π, α, β, and CED of the solvents and thus tentatively confirm the significant influence of the solvent properties on solubility. The principle of similarity and compatibility is satisfied for most of the solvents. In particular, the CED values of the larger solvents were not favorable for the solubilization of Musk ambrette. We also analyzed the molecular surface electrostatic potential of Musk ambrette by visualization techniques. Finally, IPA and ACE and their binary solution systems were analyzed by molecular dynamics simulations. The effect of solvent intermolecular interactions on the solubilization pattern was discussed. It was further confirmed that weak interactions of solvent molecules contribute more to the dissolution of Musk ambrette. These findings suggest that the prediction of solvent solubility can be initially achieved by molecular simulation techniques. Undoubtedly, this study will furnish a valuable information for the purification of Musk ambrette.

Appending Coronene Diimide with Carbon Nanohoops Allows for Rapid Intersystem Crossing in Neat Film

AbstractThe development of innovative triplet materials plays a significant role in various applications. Although effective tuning of triplet formation by intersystem crossing (ISC) has been well established in solution, the modulation of ISC processes in the solid state remains a challenge due to the presence of other exciton decay channels through intermolecular interactions. The cyclic structure of cycloparaphenylenes (CPPs) offers a unique platform to tune the intermolecular packing, which leads to controllable exciton dynamics in the solid state. Herein, by integrating an electron deficient coronene diimide (CDI) unit into the CPP framework, a donor‐acceptor type of conjugated macrocycle (CDI‐CPP) featuring intramolecular charge‐transfer (CT) interaction was designed and synthesized. Effective intermolecular CT interaction resulting from a slipped herringbone packing was confirmed by X‐ray crystallography. Transient spectroscopy studies showed that CDI‐CPP undergoes ISC in both solution and the film state, with triplet generation time constants of 4.5 ns and 238 ps, respectively. The rapid triplet formation through ISC in the film state can be ascribed to the cooperation between intra‐ and intermolecular charge‐transfer interactions. Our results highlight that intermolecular CT interaction has a pronounced effect on the ISC process in the solid state, and shed light on the use of the characteristic structure of CPPs to manipulate intermolecular CT interactions.

Appending Coronene Diimide with Carbon Nanohoops Allows for Rapid Intersystem Crossing in Neat Film.

The development of innovative triplet materials plays a significant role in various applications. Although effective tuning of triplet formation by intersystem crossing (ISC) has been well established in solution, the modulation of ISC processes in the solid state remains a challenge due to the presence of other exciton decay channels through intermolecular interactions. The cyclic structure of cycloparaphenylenes (CPPs) offers a unique platform to tune the intermolecular packing, which leads to controllable exciton dynamics in the solid state. Herein, by integrating an electron deficient coronene diimide (CDI) unit into the CPP framework, a donor-acceptor type of conjugated macrocycle (CDI-CPP) featuring intramolecular charge-transfer (CT) interaction was designed and synthesized. Effective intermolecular CT interaction resulting from a slipped herringbone packing was confirmed by X-ray crystallography. Transient spectroscopy studies showed that CDI-CPP undergoes ISC in both solution and the film state, with triplet generation time constants of 4.5 ns and 238 ps, respectively. The rapid triplet formation through ISC in the film state can be ascribed to the cooperation between intra- and intermolecular charge-transfer interactions. Our results highlight that intermolecular CT interaction has a pronounced effect on the ISC process in the solid state, and shed light on the use of the characteristic structure of CPPs to manipulate intermolecular CT interactions.

The Effect of Intermolecular Interactions on the Dissolution Property of Aripiprazole

The Effect of Intermolecular Interactions on the Dissolution Property of Aripiprazole

Effects of polyurethane/functionalised carbon nanotube interfacial interactions on tensile and compressive properties – molecular dynamics simulations

In order to understand the enhancement mechanism of the interaction between functionalised carbon nanotubes and polymer matrix, and to investigate the effects of different functionalised carbon nanotubes on the properties of composites at the microscopic level, the models of pure polyurethane (PUR), carbon nanotubes/polyurethane (CNTs/PUR), hydroxyl-functionalised carbon nanotubes/polyurethane (CNTOH/PUR), and carboxyl-functionalised carbon nanotubes/polyurethane (CNTCOOH/PUR) systems were constructed, and molecular dynamics methods were used to simulate the effects of different functionalised carbon nanotubes on the mechanical properties of polyurethane composite systems. The effects of different functionalised carbon nanotubes on the properties of PUR composite systems were compared by analysing the properties of PUR and its composite systems in terms of free volume fraction (FFV), radial distribution function (RDF), binding energy, and density distribution of PUR around different functionalised carbon nanotubes. The effects of intermolecular interactions on the properties of the composite systems were elucidated at the microscopic level. The final simulation results show that the CNTCOOH/PUR composite system with added carboxylated CNTs has the highest tensile yield strength, compressive properties and modulus; the smallest free volume fraction; the strongest bonding energy between CNTCOOH and PUR matrix, the largest density distribution of PUR matrix around CNTCOOH, and the best interfacial interaction.

Dynamic behaviors of delaminated nanofilms partly bonded on substrates with sub-nanoscale van der Waals dynamic boundaries

Abstract Dynamic buckling-induced delamination of nanofilms on substrates is a universal and essential phenomenon in nanoelectromechanical systems (NEMS). Van der Waals (vdWs) interactions play an important role in the dynamic buckling-induced delamination of nanofilms on substrates due to the interaction distances at nanoscale or even sub-nanoscale in NEMS. Therefore, it is interesting yet challenging to reveal the effect of intermolecular vdWs interactions on dynamic buckling-induced delamination of nanofilms on substrates. By considering sub-nanoscale dynamic boundary effects induced by intermolecular vdWs interactions, a parametric excitation nonlinear vibration model for dynamic buckling-induced delamination of nanofilms partly bonded on substrates is established. Effects of sub-nanoscale vdWs dynamic boundaries on transient and steady-state responses of dynamically delaminated nanofilms on substrates are analyzed. The sub-nanoscale vdWs dynamic boundaries lead the dynamic responses of delaminated-nanofilm/substrate systems very sensitive to initial conditions. The bending and shifting frequency response results demonstrated that the system nonlinearities can be greatly amplified by the sub-nanoscale vdWs dynamic boundary effect. Moreover, the spontaneous symmetry breaking and violent interfacial tearing/healing phenomena can be also triggered in the systems. Based on spontaneous symmetry breaking, a trans-scale relationship between nanofilm equilibrium positions and intermolecular vdWs interactions is established, which can provide a promising route for trans-scale measurements of molecular scale interfacial interactions. The work can also be helpful for the dynamic design of resonant NEMS devices based on nanofilm/substrate systems.

Crystallographic and spectroscopic studies on persistent triarylpropargyl cations.

By acid treatment of precursor alcohols, mesitylethynyl-substituted diarylmethyl cations were isolated as stable solids, X-ray structural analyses of which revealed a planar geometry. Furthermore, the ion pairs including these triarylpropargyl cations form charge-segregated assemblies in the crystal, and effective intermolecular interaction induces a red-shift of absorption in the crystal.

A review on the influence of various metal oxide nanoparticles on structural, morphological, optical, thermal and electrical properties of PVA/PVP blends

Biopolymer blend based nanocomposites have been interestingly investigated by researchers to achieve advanced composite functional materials that are environmentally amicable. Among the varieties of biopolymers, widespread attention has been given to polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) owing to their interesting properties like water solubility, biodegradability, biocompatibility and non-toxicity. PVA and PVP form a completely miscible blend at all compositions as both the polymers are rich in a variety of functional groups that permit effective intermolecular interactions between the polymers as well as with filler. PVA/PVP blend exhibits excellent dopant sensitive properties also. Metal oxide nanoparticles (MONPs) have made a prominent place in the area of scientific and technological research due to their unique chemical and physical properties. Doping with MONPs enhances the properties of the PVA/PVP blend matrix and the resulting PVA/PVP/MONP polymer nanocomposites are suitable for multifunctional purposes. This review mainly focused on the influence of various MONPs such as ZnO, CuO, Al2O3, ZrO2, MnO, SnO, MgO, TiO2, etc. in the structural, morphological, thermal, optical and electrical properties of PVA/PVP blend as well as its applications in various fields.

Low bandgap fused-ring electron acceptors based on π-expended asymmetric benzotrithiophene core: Regulating aggregation and photovoltaic performance by side chain isomerization

Asymmetric molecular design strategy has received increasing attention in the development of fused-ring electron acceptors (FREAs). Benzo [2,1-b: 3,4-b’: 5,6-b”] trithiophene (asym-BTT) with intrinsically asymmetric and electron-rich π-plane is an ideal unit to construct asymmetric FREAs, whereas asym-BTT-based FREAs are still very limited. Herein, two asymmetric FREAs based on the π-expended asym-BTT fused-core with para-hexylphenyl and meta-hexylphenyl side chains (p-FABTT and m-FABTT) have been developed. Owing to strong electron-donating ability and planar configuration of π-expended asym-BTT fused-core, two acceptors exhibit effective intramolecular charge transfer and intermolecular interaction, leading to near infrared absorption above 900 nm with narrow bandgaps of around 1.34 eV. Although the same π-conjugated backbones of two acceptors afford the nearly identical energy levels and solution absorptions, side chain isomerization leads to significant differences in film absorption, molecular stacking orientation and crystallinity. In neat film, the m-FABTT with meta-hexylphenyl side chains exhibits slightly redshifted absorption with stronger 0-0 absorption peak from J-aggregation compared to p-FABTT with para-hexylphenyl side chains. More orderly molecular stacking and stronger π-π interactions with shorter π-π stacking distance in both the neat film and active layer can be observed for m-FABTT. When blended with donor polymer D18, m-FABTT exhibits broadened spectral region and proper phase separation morphology for effective exciton dissociation and charge transport. Therefore, the OSCs device based on m-FABTT achieves an optimal PCE of 7.14 % with a higher JSC of 15.39 mA cm−2 and an improved FF of 57.96 % as comparing with p-FABTT-based device (a PCE of 4.81 % with a JSC of 11.67 mA cm−2 and a FF of 48.51 %).

Experimental determination of relationship between intramolecular bond lengths and their stretching vibrational frequencies of N,N-dimethylformamide and acetonitrile molecules in the liquid state

Abstract Time-of-flight (TOF) neutron diffraction measurements have been carried out on pure liquid deuterated N,N-dimethylformamide (DMF-d7), acetonitrile (AN-d3), and their concentrated LiTFSA solutions to investigate the effect of intermolecular interaction to intramolecular bond lengths, rCO, of the DMF and rCN of the AN molecules in the liquid state. Intramolecular parameters of DMF and AN are determined by least-squares fitting analyses of neutron total interference terms observed in the high-Q region. Attenuated total reflection (ATR) IR spectra have been measured for pure liquid DMF, AN, and their LiTFSA solutions of natural abundances to determine the average C=O and C≡N stretching vibrational frequencies (νCO and νCN) of the DMF and AN molecules, respectively. The relationships between rCO and νCO for DMF, and between rCN and νCN for AN, are well approximated by linear functions. The value, dνCO/drCO = −3,400 ± 1,600 cm−1 Å−1 has been derived for DMF from the slope of the fitted function. dνCN/drCN = −7,000 ± 3,000 cm−1 Å−1 has been obtained for AN. It has been revealed that the C = O bond length of the DMF and the C≡N one of the AN molecules are sensitively affected by intermolecular interaction.

The Effect of Intermolecular Interactions between Aromatic Ring‐Containing Insulators and Semiconductors in Pentacene Thin‐Film Transistors

AbstractMobility is an important parameter to estimate the performance of organic thin‐film transistors, one of the key factors affecting the mobility is the first several semiconductors molecular layers near the insulator surface. A strategy is proposed to introduce aromatic‐rings in the gate insulating layer to modulate the growth of pentacene, thus a series of aryl group containing polymers by reversible‐addition‐fragmentation chain‐transfer polymerization is synthesized for the preparation of organic thin‐film transistor insulators. The semiconductor layer is evaporated on the polymer insulators at room temperature. As the inducing function of the aromatic ring, greater weak interactions between dielectric materials and semiconductors by simulation, which makes the initial pentacene layer weak epitaxial growth, therefore pentacene could form better morphology, especially larger crystal domains and uniform thin‐film continuity. The results show that precision design and synthesis of polymer insulator layers provide new methods to achieve high performance of organic thin‐film transistors with easier fabricating process.

Insights into the Mechanism of Tryptophan Fluorescence Quenching due to Synthetic Crowding Agents: A Combined Experimental and Computational Study.

Intrinsic tryptophan fluorescence spectroscopy is an important tool for examining the effects of molecular crowding and confinement on the structure, dynamics, and function of proteins. Synthetic crowders such as dextran, ficoll, polyethylene glycols, polyvinylpyrrolidone, and their respective monomers are used to mimic crowded intracellular environments. Interactions of these synthetic crowders with tryptophan and the subsequent impact on its fluorescence properties are therefore critically important for understanding the possible interference created by these crowders. In the present study, the effects of polymer and monomer crowders on tryptophan fluorescence were assessed by using experimental and computational approaches. The results of this study demonstrated that both polymer and monomer crowders have an impact on the tryptophan fluorescence intensity; however, the molecular mechanisms of quenching were different. Using Stern-Volmer plots and a temperature variation study, a physical basis for the quenching mechanism of commonly used synthetic crowders was established. The quenching of free tryptophan was found to involve static, dynamic, and sphere-of-action mechanisms. In parallel, computational studies employing Kohn-Sham density functional theory provided a deeper insight into the effects of intermolecular interactions and solvation, resulting in differing quenching modes for these crowders. Taken together, the study offers new physical insights into the quenching mechanisms of some commonly used monomer and polymer synthetic crowders.

Transformation of Highly Hydrophobic Triarylphosphines into Amphiphiles via Staudinger Reaction with Hydrophilic Trichlorophenyl Azide.

Owing to its hydrophobic properties and reactivity, triarylphosphines (PAr3 ) are promising precursors for the development of new amphiphiles. However, an efficient and reliable synthetic method for amphiphiles based on highly hydrophobic PAr3 is still required. Herein, a straightforward transformation of highly hydrophobic PAr3 into amphiphiles via the Staudinger reaction is reported. By simply mixing PAr3 and a hydrophilic trichlorophenyl azide containing two hydrophilic chains, amphiphiles bearing a N=P bond (i. e., an azaylide moiety) were quantitatively formed. The obtained azaylide-based amphiphiles were remarkably water-soluble, enabling their spontaneous self-assembly into 2 nm-sized micelles composed of 4-5 molecules in water with a low critical micelle concentration (up to 0.05 mM or less) due to the effective intermolecular interactions among the hydrophobic surfaces. Although the azaylide moiety is easily hydrolyzed in the presence of water, the azaylide in the amphiphiles displayed notable stability in water even at 60 h, which stems from the LUMO modulation induced by the presence of three electron-withdrawing chloro groups and two twisted alkoxycarbonyl groups, according to DFT calculations. An amphiphile having a large hydrophobic surface solubilized various hydrophobic organic dyes through efficient intermolecular interactions, resulting in the dyes exhibiting either monomer or excimer emissions in water.