Increase In Molecular Size Research Articles

4]Rhombene: Solution‐Phase Synthesis and Application in Distributed Feedback Lasers With Emission Beyond 830 nm

AbstractGraphene‐like molecules with multiple zigzag edges are emerging as promising gain materials for organic lasers. Their emission wavelengths can vary widely, ranging from visible to near‐infrared (NIR), as the molecular size increases. Specifically, rhombus‐shaped molecular graphenes with two pairs of parallel zigzag edges, known as [n]rhombenes, are excellent candidates for NIR lasers due to their small energy gaps. However, synthesizing large‐size rhombenes with emission beyond 800 nm in solution remains a significant challenge. In this study, we present a straightforward synthesis of an aryl‐substituted [4]rhombene derivative, [4]RB‐Ar, using a method that combines intramolecular radical‐radical coupling with Bi(OTf)3‐mediated cyclization of vinyl ethers. The structure of [4]RB‐Ar was confirmed through X‐ray crystallographic analysis. Bond length analysis and theoretical calculations indicate that aromatic sextets are predominantly localized along the molecule's long axis. Significantly, [4]RB‐Ar demonstrates narrow amplified spontaneous emission at around 834 nm when dispersed in polystyrene thin films. Moreover, solution‐processed distributed feedback lasers employing [4]RB‐Ar as the active gain material display tunable narrow emissions in the range of 830 to 844 nm.

4]Rhombene: Solution-Phase Synthesis and Application in Distributed Feedback Lasers With Emission Beyond 830 nm.

Graphene-like molecules with multiple zigzag edges are emerging as promising gain materials for organic lasers. Their emission wavelengths can vary widely, ranging from visible to near-infrared (NIR), as the molecular size increases. Specifically, rhombus-shaped molecular graphenes with two pairs of parallel zigzag edges, known as [n]rhombenes, are excellent candidates for NIR lasers due to their small energy gaps. However, synthesizing large-size rhombenes with emission beyond 800 nm in solution remains a significant challenge. In this study, we present a straightforward synthesis of an aryl-substituted [4]rhombene derivative, [4]RB-Ar, using a method that combines intramolecular radical-radical coupling with Bi(OTf)3-mediated cyclization of vinyl ethers. The structure of [4]RB-Ar was confirmed through X-ray crystallographic analysis. Bond length analysis and theoretical calculations indicate that aromatic sextets are predominantly localized along the molecule's long axis. Significantly, [4]RB-Ar demonstrates narrow amplified spontaneous emission at around 834 nm when dispersed in polystyrene thin films. Moreover, solution-processed distributed feedback lasers employing [4]RB-Ar as the active gain material display tunable narrow emissions in the range of 830 to 844 nm.

Assessing the domain-based local pair natural orbital (DLPNO) approximation for non-covalent interactions in sizable supramolecular complexes.

The titular domain-based local pair natural orbital (DLPNO) approximation is the most widely used method for extending correlated wave function models to large molecular systems, yet its fidelity for intermolecular interaction energies in large supramolecular complexes has not been thoroughly vetted. Non-covalent interactions are sensitive to tails of the electron density and involve nonlocal dispersion that is discarded or approximated if the screening of pair natural orbitals (PNOs) is too aggressive. Meanwhile, the accuracy of the DLPNO approximation is known to deteriorate as molecular size increases. Here, we test the DLPNO approximation at the level of second-order Møller-Plesset perturbation theory (MP2) and coupled-cluster theory with singles, doubles, and perturbative triples [CCSD(T)] for a variety of large supramolecular complexes. DLPNO-MP2 interaction energies are within 3% of canonical values for small dimers with ≲10 heavy atoms, but for larger systems, the DLPNO approximation is often quite poor unless the results are extrapolated to the canonical limit where the threshold for discarding PNOs is taken to zero. Counterpoise correction proves to be essential in reducing errors with respect to canonical results. For a sequence of nanoscale graphene dimers up to (C96H24)2, extrapolated DLPNO-MP2 interaction energies agree with canonical values to within 1%, independent of system size, provided that the basis set does not contain diffuse functions; these cause the DLPNO approximation to behave erratically, such that results cannot be extrapolated in a meaningful way. DLPNO-CCSD(T) calculations are typically performed using looser PNO thresholds as compared to DLPNO-MP2, but this significantly impacts accuracy for large supramolecular complexes. Standard DLPNO-CCSD(T) settings afford errors of 2-6 kcal/mol for dimers involving coronene (C24H12) and circumcoronene (C54H18), even at the DLPNO-CCSD(T1) level.

Scaling-up VPT2: A feasible route to include anharmonic correction on large molecules

Vibrational analysis plays a crucial role in the investigation of molecular systems. Though methodologies like second-order vibrational perturbation theory (VPT2) have paved the way to more accurate simulations, the computational cost remains a difficult barrier to overcome when the molecular size increases. Building upon recent advances in the identification of resonances, we propose an approach making anharmonic simulations possible for large-size systems, typically unreachable by standard means. This relies on the fact that, often, only portions of the whole spectra are of actual interest. Therefore, the anharmonic corrections can be included selectively on subsets of normal modes directly related to the regions of interest. Starting from the VPT2 equations, we evaluate rigorously and systematically the impact of the truncated anharmonic treatment onto simulations. The limit and feasibility of the reduced-dimensionality approach are detailed, starting on a smaller model system. The methodology is then challenged on the IR absorption and vibrational circular dichroism spectra of an organometallic complex in three different spectral ranges.

Effects of pore size, water content, and oxygen-containing functional groups on oxygen adsorption in bituminous coal

To further explore the mechanism of coal spontaneous combustion and better grasp the laws of spontaneous combustion, this article studied the adsorption behavior of O2 in coal. Materials studio software was applied to study the adsorption of oxygen under different water content, different pore sizes, and different oxygen-containing functional groups by means of grand canonical Monte Carlo and molecular dynamics simulation methods. The results show that the adsorption capacity of O2 decreases with the increase in water content. With the increase of molecular pore size of coal, the adsorption capacity of O2 increases, and the tight adsorption amounts decrease. The equivalent adsorption heat is less than 42 kJ/mol, indicating that the adsorption of O2 in coal pores is physical adsorption. The smaller the physical adsorption energy and charge transfer value of the hydroxyl group for O2, it indicates that the hydroxyl group is the active group for the physical adsorption of O2.

Structural distinction of zigzag-edge coronoids analyzed by spectroscopies

Unlike armchair-edge coronoids, the band gap of zigzag-edge coronoids (ZCs) can be adjusted via the molecular and cavity sizes. Herein, X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy are used to identify 12 structures of ZCs with different molecular and cavity sizes. Evidently, the C1s peak positions of the ZCs depend on the number of carbons (NC) between the inner and outer edges: they shift to a lower and higher binding energy if the ZCs have an even and odd value of NC, respectively, compared with that of structures without a cavity because of the change in band gap. The C1s peak positions of ZCs with NC = 2 and NC = 3–6 differ by more than 0.4 eV. Raman spectroscopic analysis reveals that the detected characteristic modes depend on NC. For structures with NC = 2, C−H vibration and C−C stretching vibration mode bands are observed, whereas for structures with NC = 3–6, C−H vibration and breathing mode bands are observed. In particular, the band originating from the C−H vibration on the inner edge appear in structures with NC = 3–6 and a pore size larger than 8.26 Å. As the molecular size increases, the intensities of the characteristic bands change and the breathing mode band shift to a higher wavenumber. These results indicate that the molecular and cavity sizes of the ZCs can be distinguished using XPS and Raman spectroscopy.

Fused Triangulene Dimers: Facile Synthesis by Intramolecular Radical‐Radical Coupling and Application for Near‐Infrared Lasers

AbstractLarge graphene‐like molecules with four zigzag edges are ideal gain medium materials for organic near‐infrared (NIR) lasers. However, synthesizing them becomes increasingly challenging as the molecular size increases. In this study, we introduce a new intramolecular radical‐radical coupling approach and successfully synthesize two fused triangulene dimers (1 a/1 b) efficiently. X‐ray crystallographic analysis of 1 a indicates that there is no intermolecular π‐π stacking in the solid state. When the more soluble derivative 1 b is dispersed in polystyrene thin films, amplified spontaneous emission in the NIR region is observed. Using 1 b as the active gain material, we fabricate solution‐processed distributed feedback lasers that exhibit a narrow emission linewidth at around 790 nm. The laser devices also exhibit low thresholds with high photostability. Our study provides a new synthetic strategy for extended nanographenes, which have diverse applications in electronics and photonics.

Fused Triangulene Dimers: Facile Synthesis by Intramolecular Radical-Radical Coupling and Application for Near-Infrared Lasers.

Large graphene-like molecules with four zigzag edges are ideal gain medium materials for organic near-infrared (NIR) lasers. However, synthesizing them becomes increasingly challenging as the molecular size increases. In this study, we introduce a new intramolecular radical-radical coupling approach and successfully synthesize two fused triangulene dimers (1 a/1 b) efficiently. X-ray crystallographic analysis of 1 a indicates that there is no intermolecular π-π stacking in the solid state. When the more soluble derivative 1 b is dispersed in polystyrene thin films, amplified spontaneous emission in the NIR region is observed. Using 1 b as the active gain material, we fabricate solution-processed distributed feedback lasers that exhibit a narrow emission linewidth at around 790 nm. The laser devices also exhibit low thresholds with high photostability. Our study provides a new synthetic strategy for extended nanographenes, which have diverse applications in electronics and photonics.

Effects of Enzymatic Hydrolysis and Size Fractionation of Mealworm (Tenebrio molitor larvae) Protein on Antioxidant and Anti-Inflammatory Activities and Inhibition of Muscle Loss

The antioxidant, anti-inflammatory, and muscle loss inhibitory effects of mealworm protein were investigated. Mealworm protein hydrolysate (MPH) was obtained by enzymatic hydrolysis and fractionated based on the molecular size. Although the protein content decreased with hydrolysis, it increased with an increase in size. Upon hydrolysis, essential and branched-chain amino acids decreased while free amino acids increased but decreased with an increase in size. The antioxidant activity increased upon hydrolysis and with an increase in molecular size. The anti-inflammatory effects were highest for MPH > 10 kDa and were similar to whey protein isolate (WPI), for IL-1β, IL-6, and TNF-α. Size fractionation did not significantly affect the anti-inflammatory effects. The MPH > 10 kDa (1.19-fold of control) resulted in the lowest myostatin expression in C2C12 muscle cells with and without LPS, which was similar to WPI (1.23-fold). Consequently, MPH may be a potential alternative to WPI.

Constraining the Effect of Surfactants on the Hygroscopic Growth of Model Sea Spray Aerosol Particles

The cloud condensation nuclei activation of sea spray aerosol (SSA) is tightly linked to the hygroscopic properties of these particles and is defined by their physical and chemical properties. While hygroscopic sea salt in SSA strongly influences particle water uptake, the marine-derived components that make up the organic fraction of SSA constitute a complex mixture, and their effect on hygroscopic growth is unknown. To constrain the effect of organic compounds and specifically surface-active compounds that adsorb on particle interfaces, particle hygroscopic growth studies were performed on laboratory-generated model sea salt/sugar particles. For sea salt/glucose particles, ionic surfactants facilitated water uptake at low relative humidity (RH), increasing the particle growth factor (GF) by up to 7.61%, and caused a reduction in the deliquescence relative humidity (DRH), while nonionic surfactants had a minimal effect. Replacing glucose with polysaccharide laminarin in sea salt/sugar/surfactant particles caused a reduction in GF at low RHs and minimized the effect of ionic surfactants on the DRH. At RHs above the DRH, the addition of anionic or nonionic surfactants caused a decrease in GF for both sea salt/glucose and sea salt/laminarin particles. The addition of cationic surfactants, however, did not have a dampening effect on water uptake of sea salt/sugar particles and even showed a GF increase of up to 3.7% at 90% RH. An increase in the complexity of the sugar dampens the water uptake for particles containing nonionic surfactants but increases the water uptake for cationic surfactants. The cloud activation potential for 100 nm particles analyzed in this study is higher for ionic surfactants and decreases with an increase in surfactant molecular size when particle interfacial tension is considered. The surfactant effect on the hygroscopic growth and cloud activation potential of the particles containing sea salt/sugar is dependent on the surfactant ionicity and molecular size, the particle size and interfacial tension, and the interactions between inorganic salt and organic species under different RH conditions.

25 Years of Small-Molecule Optimization at Novartis: A Retrospective Analysis of Chemical Series Evolution.

In the drug development process, optimization of properties and biological activities of small molecules is an important task to obtain drug candidates with optimal efficacy when first applied in subsequent clinical studies. However, despite its importance, large-scale investigations of the optimization process in early drug discovery are lacking, likely due to the absence of historical records of different chemical series used in past projects. Here, we report a retrospective reconstruction of ∼3000 chemical series from the Novartis compound database, which allows us to characterize the general properties of chemical series as well as the time evolution of structural properties, ADMET properties, and target activities. Our data-driven approach allows us to substantiate common MedChem knowledge. We find that size, fraction of sp3-hybridized carbon atoms (Fsp3), and the density of stereocenters tend to increase during optimization, while the aromaticity of the compounds decreases. On the ADMET side, solubility tends to increase and permeability decreases, while safety-related properties tend to improve. Importantly, while ligand efficiency decreases due to molecular growth over time, target activities and lipophilic efficiency tend to improve. This emphasizes the heavy-atom count and log D as important parameters to monitor, especially as we further show that the decrease in permeability can be explained with the increase in molecular size. We highlight overlaps, shortcomings, and differences of the computationally reconstructed chemical series compared to the series used in recent internal drug discovery projects and investigate the relation to historical projects.

Electron transfer of functionalized quinones in acetonitrile

Quinones are redox active organic molecules that have been proposed as an alternative choice to metal-based materials in electrochemical energy storage devices. Functionalization allows one to fine tune not only their chemical stability but also the redox potential and kinetics of the electron transfer reaction. However, the reaction rate constant is not only determined by the redox species but also impacted by solvent effects. In this work, we show how the functionalization of benzoquinone with different functional groups impacts the solvent reorganization free energies of electron transfer half-reactions in acetonitrile. The use of molecular density functional theory, whose computational cost for studying the electron transfer reaction is considerably reduced compared to the state-of-the-art molecular dynamics simulations, enables us to perform a systematic study. We validate the method by comparing the predictions of the solvation shell structure and the free energy profiles for electron transfer reaction to the reference classical molecular dynamics simulations in the case of anthraquinone solvated in acetonitrile. We show that all the studied electron transfer half-reactions follow the Marcus theory, regardless of functional groups. Consequently, the solvent reorganization free energy decreases as the molecular size increases.

Molecular dynamics simulation of calcium silicate hydrate/tannic acid interfacial interactions at different temperatures: configuration, structure and dynamic

In the paper, the effect of temperature on tannic acid molecular conformation and the interaction between tannic acid and substrate were investigated systematically by molecular dynamics. The tensile force of tannin acid separation from CSH matrix at three temperatures was calculated by SMD simulation, and then the adhesion energy between tannin acid and CSH was calculated by Bell Model. The results showed that high temperature affects the gyration of the single bond in the tannic acid, which leads to the increase of tannic acid molecular chain size and radius of gyration. Tannic acid molecules are more extended and the contact area with the substrate became larger in high temperature, which enhanced interfacial adhesion energy. Further, by analyzing the structure and dynamics of the composite, it comes out that not only the substrate has more sites available for tannic acid but also the interfacial ionic bonding formed is more stable after high temperature. Enhanced interfacial chemical bonds limit the bending motion of tannic acid molecular, which leave them in a well-stretched state, to causes tannic acid to be stably adsorbed on the substrate.

Nacre-like ultra-robust supramolecular-functionalized graphene oxide membrane for bifunctional separation

Two-dimensional graphene oxide (GO) membranes exhibit great potential for environmental aqueous separation and purification. However, their viability and performance are greatly limited under cross-flow conditions due to the enlargement of interlayer spacing and peeling of stacked GO laminates in aqueous environments. Herein, inspired by natural nacre structure, we present a dual-functional and ultra-stable β-cyclodextrin (β-CD) -polyacrylic acid (PAA) -GO composite membrane, with a constant d-spacing in both wet and dry states. Nanosheets and chain polymers construct a typical “brick-mortar” structural configuration, which exhibits great anti-swelling property compared with other reported GO membranes. By rationally optimizing and tuning the membrane structures, the ultrathin GO membrane (∼50 nm) exhibits outstanding stability in cross-flow and long-term filtration. Moreover, the designed membrane shows dual functions (high-throughput enantioselectivity and excellent dyes rejection) with the increase of molecular size. This strategy boosts the ongoing research in designing robust lamellar membrane materials for practical engineering applications in aqueous environments.

Application of Reaction Path Search Calculations to Potential Energy Surface Fits.

There has been significant progress in recent years in the use of machine learning techniques to model high-dimensional reactive potential energy surfaces using large-scale data obtained from ab initio electronic structure calculations. In these methods, the strategy used to gather data becomes a key issue as the molecular size increases. In this work, we examine the applicability of the reaction path search algorithm implemented in the Global Reaction Route Mapping (GRRM) code as a data-gathering approach. The electronic energies and gradients sampled by using the GRRM calculation are directly used in potential energy surface fitting to a permutationally invariant polynomial function. This simple approach was applied to the HNS and HCNO reaction systems, and we found that the fitted potential energy surfaces reasonably reproduce the features of the electronic structure calculations used in the GRRM calculations. This suggests that the GRRM sampling scheme can be used to construct an initial potential energy surface.

Study on rheological and chemical behaviors of unaged and aged modified asphalt with solid waste coking sulfur paste

In this study, solid waste coking sulfur paste was used as raw material to prepare asphalt modifier. Then, the rheological behaviors, storage stability, chemical characteristics and microscopic features of modified asphalt enriched with 10, 20, 30, and 40% of coking sulfur paste granule (CSPG) were investigate. The effects of CSPG on the properties of the modified asphalt after short- and long-term ageing were also studied. The modified asphalt was graded by multiple stress creep and recovery (MSCR) and performance grade (PG) methods. The results show that CSPG decreased the viscosity of modified asphalt and the mixing temperature. The addition of 10% and 20% CSPG improved the anti-cracking ability of modified asphalt at low temperature. Conversely, 30% and 40% CSPG modified asphalt performed better at high temperature with an improved resistance to deformation. The introduction of CSPG strengthened the favorable effect of ageing on the high-temperature properties, but also enhanced the adverse effect of ageing on the low-temperature properties. CSPG modified asphalt also exhibited better storage stability. Furthermore, CSPG can react with asphalt to produce polysulfide compounds (R-Sx-R’), resulting in the increase of large molecular size. CSPG also exists in the form of crystalline sulfur as an inorganic filler to enhance the high temperature anti-rutting ability of modified asphalt. Therefore, 40% CSPG modified asphalt exhibited the best high-temperature performance level, which can withstand very heavy traffic at 70 °C (PG70V).

Studies on the role of hydroxyapatite nanoparticles in imparting unique thermal, dielectric, flame retardancy and petroleum fuel resistance to novel chlorinated EPDM/chlorinated NBR blend

Novel elastomeric blend nanocomposites of chlorinated nitrile rubber (Cl-NBR) and chlorinated ethylene-propylene-diene rubber (Cl-EPDM) with different contents of nano-hydroxyapatite (HA) were prepared. The formation of blend nanocomposite was analyzed by FTIR, XRD, TEM, SEM and TGA. The fire resistance, dielectric behavior and diffusion of petroleum fuels through the blend membrane had been investigated as a function of nanoparticle loading. The FTIR revealed the absorption band of HA in the rubber blend indicated the effective interaction between HA nanofiller and the rubber blend. XRD plots indicated a reduction in amorphous region of rubber blend with the addition of nanoparticles. TEM and SEM images revealed the uniform dispersion of nanoparticles in the rubber blend. TGA results indicated that the thermal stability of rubber blend nanocomposite was higher than Cl-NBR/Cl-EPDM blend. Increased fire resistance of blend composites obtained from limiting oxygen index demonstrated that hydroxyapatite nanoparticles were served as an excellent fire-retardant additive for Cl-NBR/Cl-EPDM blend. Improvement in dielectric constant with the loading of nanoparticles indicated the reinforcement of blend matrix by the HA nanoparticles. The solvent uptake of blend nanocomposite decreased up to 7 phr HA-loaded sample. A decrease in solvent uptake was also observed with the increase in molecular size of the penetrant molecules. The mechanism of diffusion was anomalous in nature. Overall, the sample with 7 phr of HA-filled rubber blend showed a remarkable increase in dielectric properties, flame resistant and minimum solvent uptake.

Structure dependency of the reactivity of aromatic hydrocarbons involving the formation of oxygenated polycyclic aromatic hydrocarbons (OPAHs)

The reactivity of six aromatic hydrocarbons (benzene, naphthalene, anthracene, toluene, indene, and fluorene) with O or OH, which are involved in the formation of oxygenated polyaromatic hydrocarbons (OPAHs), were compared using quantum chemistry calculations to reveal the structure dependency. We revealed that comparing C6H6, C10H8, and C14H10, the barrier height becomes lower as the molecular size increases. Comparing C9H8 and C13H10, which contain a 5-membered ring, C9H8 is more reactive with both O and OH. In addition, possible reaction paths for the formation of indanone, an OPAH which is observed in combustion, from C9H8 are found.

The absorption of polycyclic aromatic hydrocarbons into the skin to elicit cutaneous inflammation: The establishment of structure–permeation and in silico–in vitro–in vivo relationships

Polycyclic aromatic hydrocarbons (PAHs) can induce skin toxicity. Although some investigations have been conducted to assess the skin toxicity of different PAHs, few comparisons using a series of PAHs with different ring numbers and arrangements have been done. We aimed to explore the skin absorption of 6 PAH compounds and their effect on cutaneous inflammation. In vitro skin permeation was rated by Franz cell with pig skin. Molecular docking was employed to compute the PAH interaction with stratum corneum (SC) lipids. Cultured keratinocytes were exposed to PAHs for analyzing cytotoxicity, cyclooxygenase (COX)-2, prostaglandin E2 (PGE2), chemokines, and differentiation proteins. The in vivo topical PAH exposure in mice was characterized by skin absorption, transepidermal water loss (TEWL), PGE2 level, and histology. The skin deposition from the aqueous vehicle increased following the increase of PAH lipophilicity and molecular size, with benzo[a]pyrene (5-ring PAH) showing the greatest absorption. Pyrene was the compound showing the highest penetration across the skin (flux). Although the PAHs fluoranthene, pyrene, chrysene, and 1,2-benzanthracene all had 4 rings, the skin permeation was quite different. 1,2-Benzanthracene showed the greatest absorption among the 4-ring compounds. The PAHs with higher absorption exhibited stronger interaction with SC lipids according to the in silico modeling. Chrysene and 1,2-benzanthracene generally showed the highest COX-2 and PGE2 expression, followed by benzo[a]pyrene. The lowest COX-2 and PGE2 upregulation was observed for naphthalene (2-ring PAH). A contrary tendency was detected for the upregulation of chemokines. Filaggrin and integrin β1 in keratinocytes were suppressed at a comparable level by all PAHs. The skin’s absorption of PAHs showed strong in vivo–in vitro correlation. 1,2-Benzanthracene and benzo[a]pyrene highly disrupted the skin barrier and elevated the inflammation in vivo. The tendency toward in vivo inflammation caused by various PAHs could be well predicted by the combined estimation using in vitro skin absorption and a keratinocyte bioassay. This study also established the structure–permeation relationship (SPR) of PAHs.

Thermal Diffusivity of Linear Alkanes and its Behaviour with the Size of the Chain: Study with a Photopyroelectric Technique

Thermal transport properties of substances are fundamental for science and engineering. Among these properties, thermal diffusivity characterizes the way materials transport heat under nonstationary conditions. The manner in which this thermal property behaves with the size or molecular configuration is very important to understand the mechanisms involved in heat transport. It is a complicated work to study variations on this thermal property taking these two variables (size and configuration) together. Linear alkanes have essentially the same spatial configuration, varying only the molecular size (the number of involved carbon atoms in the molecule), so they are ideal substances to study the behaviour of thermal properties with the molecular size alone. In this work photopyroelectric technique, taking the sample´s thickness as variable (the so-called TWRC method), is used for thermal diffusivity measurements of linear alkanes, from 1-heptane to 1-heptadecane. It is shown that this thermal property increases with the molecular size. This behaviour can be explained in a very simple way if it is considered that the increase in molecular size increases “routes” of heat transport.