Effect Of Molecular Structure Research Articles

The effect of molecular structure of chlorin photosensitizers on photo-bleaching of 1,3-diphenylisobenzofuran—the possible evidence of iodine reactive species formation

In this short communication, we focus on the ability of chlorin e 6 photosensitizers (PSs) with one, two or three cationic groups to generate singlet oxygen species ( 1 O 2 ) in an apolar model medium, viz. 1-octanol (OctOH). The quantum yield of 1 O 2 (Φ Δ ) is determined indirectly by the chemical method for seven synthesized PSs using 1,3-diphenylisobenzofuran (DPBF) as a singlet oxygen trap. The Φ Δ values of four PSs with one or two cationic groups occupying opposite positions in the macrocycle are equal to 0.6, which is nearly identical to the values obtained by the time-resolved fluorescence spectroscopy method. In contrast, three PSs containing a 3(1),3(2)-bis-(N,N,N-trimethylaminomethylvinyl) iodide fragment with two adjacent cationic groups have an abnormally high quantum yield reaching 0.8. It is apparent that this phenomenon results from faster trap oxidation induced by radical reactions leading to molecular iodine formation.

Extending the Range of Nitrofurantoin Solid Forms: Effect of Molecular and Crystal Structure on Formation Thermodynamics and Physicochemical Properties

Extending the Range of Nitrofurantoin Solid Forms: Effect of Molecular and Crystal Structure on Formation Thermodynamics and Physicochemical Properties

Traction behavior and mechanism of molecular level with effects of molecular structure and sliding velocity in boundary lubrication regime: A molecular dynamics study

The traction mechanism in power transmission systems with effects of sliding velocity and molecular structure are revealed at high temperature and pressure through molecular dynamics approach. Firstly, the simulated traction coefficients agree well with the experimental values, and the linear correlation between traction coefficient and bond energy is created to predict the coefficient. The molecule with higher bond energy and more –CH3 groups between two terminal cyclohexane rings shows higher traction coefficient. Then, the typical shear localization is found from the layered structure of alicyclic molecules confined between Fe2O3 slabs. The increase of sliding velocity has a very week effect on the velocity profile but benefits the slip length shrinkage on the whole. The traction coefficient increases fast and then converges toward a plateau with increasing velocity. Finally, the power transmission mechanism in molecular level is discussed and attributed to three effects, i.e., the interlocking effect between alicyclic rings in layer, the cross-linkage effect between layers, and the rotation resistance effect of alicyclic structure. This mechanism is desirable to be achieved with low degrees of slip, and thus maximize the efficiency of the device and help designing new traction fluids.

Manipulating the Self-Assembly of Multicomponent Low Molecular Weight Gelators (LMWGs) through Molecular Design.

Multicomponent low molecular weight gelators (LMWGs) may self-assemble by co-assembly (CA), social self-sorting (SSS), or narcissistic self-sorting (NSS). Understanding the nuances of the self-assembly processes is important to predict the behavior of multicomponent organogels. Here, we investigate the effect of molecular structure on self-assembly in a series of amino-acid based bicomponent LMWGs that differ in headgroup and alkyl chain length. Packing preference of the organogels was determined using differential scanning calorimetry, nuclear magnetic resonance spectroscopy and small angle X-ray scattering. From 66 bicomponent samples we found 50 CA, 14 SSS and 2 NSS. Furthermore, we performed statistical analysis to investigate the role of hydrophobicity and chain length on the overall pathway of self-assembly for these systems. We found the hydrophobicity of the headgroup strongly affected the assembly preference of the organogel, but alkyl chain length only played a small role.

Structure–activity relationships of pH-responsive and ionizable lipids for gene delivery

Ionizable lipids are the leading vectors for gene therapy. Understanding the effects of molecular structure on efficient gene delivery is one of the most important challenges for maximizing the utility of such lipid vectors. We synthesized an array of pH-responsive and ionizable lipids to investigate the relationship between lipid structure and activity. The optimized lipid (EDM) has double tertiary amines in the headgroup and an ester linker. EDM exhibited efficient DNA and siRNA delivery to, and gene silencing of, A549 cells. EDM has a pKa value of 6.67, which enabled it to quickly escape from the endosome after entering the cell; the ester linkages rapidly degraded and enabled gene release into the cytoplasm. EDM also delivered IGF-1R siRNA to inhibit tumor growth and induce cancer cell apoptosis by efficient inhibition of IGF-1R expression in mice. Our study on the structure–activity relationships of ionizable lipids will facilitate clinical applications.

A structure-property model for the prediction of pKa values of different amines in the CO2 capture process of concern to the prediction of thermodynamic properties

In this study, Quantitative Structure-Property Relationship (QSPR) method has been applied on a dataset including the pKa values of 21 different structures (20 amines and ammonia) at four temperatures in the post-combustion-capture process using QSARINS. QSPR models have been accomplished in two situations, called fixed and unfixed temperatures. In the fixed temperatures, four predictive models with one descriptor have been separately developed at each temperature. Besides, thermodynamic properties have been calculated by the van’t Hoff equation using predicted pKa values. In the unfixed temperatures, two general models were developed which take into account the effects of molecular structure and temperature, simultaneously. The predicted pKa values and calculated Gibbs free energy have a good consistency with related values in the literature. The reliability of each developed model has been examined using external assessments. The values of some statistical parameters such as R2 = 0.89 and AARD% = 2.68 verify the prediction capability of models.

Gold nanoparticles-based SERS nanosensor for thiram and chloramphenicol monitoring in food samples: Insight into effects of analyte molecular structure on their sensing performance and signal enhancement

Electrochemically synthesized gold nanoparticles (e-AuNPs) were deposited on aluminum substrates to fabricate effective surface enhanced Raman spectroscopy (SERS) sensors for thiram and CAP monitoring in food samples, between which the thiram sensor showed better performance in terms of sensibility, reliability and practicability. Regarding that the differences in SERS performance of the two sensors were closely associated to the distinction in molecular structure of the two analytes, we investigated the effects of analyte molecular structure on the sensing performance, especially the enhancement factors (EFs), of the sensors. As the enhancement of SERS signal is explained by both chemical and electromagnetic mechanisms (CM and EM), the investigation was also carried out in two directions. On one hand (CM), the adsorption of the analytes on the surface of e-AuNPs was studied by using both Langmuir and Freundlich isotherm models to qualitatively evaluate their adsorption capacity on e-AuNPs. On the other hand (EM), SERS measurements of thiram and CAP were performed on a set of substrates, on which the interpaticle distance between e-AuNPs were controlled by pH adjustment before deposition, to study their adsorption ability in the hotspots. The obtained results showed that thiram adsorption obeyed Langmuir model, thus, thiram residues adsorbed as a monolayer on the e-AuNPs surface at the same adsorbing site. In contrast, CAP adsorption obeyed Freundlich one with multilayer adsorption and two potential adsorbing sites. In addition, with sulfur-containing structure, small and simple molecule, capability of S-S bond cleavage and smaller steric hindrance, thiram exhibited better adsorption ability not only on the surface of e-AuNPs but also in the nano-gaps between them. Therefore, on SERS substrates that e-AuNPs were deposited before the addition of analyte, analyte molecular structure still shows great effects on sensing performance of the sensors, especially on the enhancement factors, in both CM and EM.

The role of some triazoles on the corrosion inhibition of C1020 steel and copper in a desalination descaling solution

The effect of molecular structure on the performance of three triazole derivatives namely benzotriazole (BZT), 5-methyl-1H-benzotriazole (5MBZT), and 3-amino-5-methylthio-1H-1,2,4, triazole (3AMT) as corrosion inhibitors for C1020 steel and pure copper in 2% hydrochloric acid (HCl), which simulate descaling process in a typical desalination plant was investigated. Electrochemical characterization such as electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), linear polarization resistance (LPR) techniques and theoretical simulations were utilized in this study. The electrochemical characterization results showed that the order of inhibition efficiencies for the inhibitors was a function of the type of metal, molecular structure, and immersion time. For instance, for C1020 steel, the order of inhibition efficiency using EIS data was 5MBZT (91.8%) > BZT (78.1%) > 3AMT (24.8%) after 24 h of immersion. On the other hand, for pure copper, the order of inhibition efficiency with the same EIS data was 3AMT (93.0%) > 5MBZT (92.1%) > BZT (90.4%) after 24 h of immersion indicating the role of different metallurgy on corrosion protection. The theoretical results provided molecular level insights on the nature and the active sites of the corrosion inhibiting species as well as the energetics of the adsorption process on steel and copper.

Combined effects of starch fine molecular structures and storage temperatures on long-term rice amylopectin retrogradation property

Though the retrogradation property as affected by starch fine molecular structures has been widely investigated, it remains largely unexplored how concurrent starch structures and storage conditions e.g. temperature tailor the starch retrogradation property. The amylopectin long-term retrogradation for 8 different rice starches with a broad range of amylose content was thus investigated under different storage temperatures. Results showed that gelatinized starch stored at −20 °C generally had a narrower melting temperature range from differential scanning calorimetry, while larger cells and thicker cell walls in the gel matrix than that stored at 4 °C. Different linear correlations were found between starch fine molecular structures and amylopectin retrogradation parameters when starch was stored under different temperatures. For example, the melting enthalpy of retrograded starch double helices was negatively correlated with the amount of amylose intermediate chains at 4 °C, while positively correlated with the relative length of amylopectin short chains at −20 °C. Under both temperatures, rice starch R250 had the highest retrogradation enthalpy. These results could help the rice industry improve both the nutritional and textural attributes of cooked rice by selecting starch with desirable molecular structures and optimizing the storage conditions for rice after cooking.

Nanomechanical behavior of hierarchical self‐assemblies of perylene bisimide derivatives

AbstractIn the field of self‐assemblies of perylene bisimide (PBI) derivatives, effect of molecular structure on the mechanical properties of assemblies is essential but still not understood in full detail. To reveal the relationships of PBI molecules and mechanical properties of their assemblies, the PeakForce Quantitative Nanomechanical Mapping (PeakForce QNM) is applied to visualize the structures and quantify the mechanical properties of assemblies formed by the model PBI derivatives (M1: C6H13‐PBI‐OH; M2: C12H25‐PBI‐OH). The influence of the linear alkyl chainson self‐assembly of PBI derivatives has been investigated. We found that the long‐range ordered structures could be formed for both M1 and M2 in high‐polarity solvents. M1 formed the micron‐size bricks with the Young's modulus of (3.1 ± 1.0) GPa, whereas M2 assembled into the nanosheets with the Young's modulus of (2.5 ± 0.5) GPa. The competitive, non‐competitive and cooperative interactions of the π–π stacking, hydrogen‐bond interactions, and van der Waals interactions facilitated the growth of assemblies with the different hardness and size. This method can be used to investigate the molecular self‐assembly, which helps to establish relationships among structure, performance, and corresponding application of assemblies.

Effects of Molecular Structure and Functional Groups on the Performance of Carbonyl Organic Compounds as Cathodes for Aluminum Batteries

Effects of Molecular Structure and Functional Groups on the Performance of Carbonyl Organic Compounds as Cathodes for Aluminum Batteries

Cocrystallization tailoring radiative decay pathways for thermally activated delayed fluorescence and room-temperature phosphorescence emission.

Modulation of excited-state processes in binary organic cocrystals has been rarely explored so far. Here, we develop two charge-transfer (CT) cocrystal microrods with a 1 : 1 stoichiometric ratio where halogenated dibenzothiophene (DBT) compounds act as π-electron donors and 1,2,4,5-tetracyanobenzene (TCNB) acts as an acceptor. Unexpectedly, the cocrystal containing one bromine (Br) atom at the 3-position of DBT (3-BrTC) presents thermally activated delayed fluorescence (TADF), while the other one comprising one Br atom at the 4-position of DBT (4-BrTC) exhibits both TADF and room-temperature phosphorescence (RTP). Experimental and theoretical calculation results reveal that CT interactions in 3- and 4-BrTC decrease the S1-T2 energy gap, whereas abundant lone-pair electrons from the Br atom in 4-BrTC facilitate the n → π* transition. As a consequence, single TADF and dual-emissive TADF/RTP were realized, respectively. The present work offers wonderful insight into the effect of molecular structures on the excited-state pathways of organic CT cocrystals.

Rydberg state excitation of atoms and molecules in ultrafast intense laser field

When atoms or molecules are irradiated by a strong laser field with pulse duration of tens of femtoseconds and intensity larger than 10<sup>13</sup> W/cm<sup>2</sup>, they will generally undergo tunneling ionization, which will induce various non-perturbative and highly nonlinear phenomena. Investigations into the strong field physical processes is of significance in studying attosecond physics, molecular orbital imaging, ultrafast electron diffraction and advanced short ultraviolet light sources. While there is a relatively long history of the studies of tunneling ionization induced physics including high-order above threshold ionization (HATI), high-order harmonic generation (HHG) and non-sequential double ionization (NSDI), it is until recently to surprisedly find that in the tunneling ionization region, neutral atoms or molecules can survive in strong laser fields in highly excited Rydberg states. As a basic process of the interaction between ultrafast strong laser fields and atoms or molecules, such a Rydberg state excitation (RSE) has been viewed as an important supplement to the physical picture of the tunneling ionization. During the past several years, the extensive research attention has been paid to the RSE process in strong laser field. Various theoretical and experimental methods have been developed to investigate the strong field RSE of both atoms and molecules, to understand the underlying physical mechanism behind the recapture of the tunneling electrons and to reveal the quantum features and molecular structure effect in RSE. These advances have brought about an in-depth understanding and a systematic view of the atomic and molecular RSE in strong laser fields, as well as their relations to the other tunneling ionization induced physical processes such as ATI, HHG and NSDI. Here, we systematically review recent research progress of the atomic and molecular RSE in strong laser fields. We particularly focus on several aspects of this strong field process, i.e. the physical mechanism of the recapture, the quantum feature and the interference of different orbits, and the structure effect in molecular RSE. In addition, neutral particle acceleration and coherent radiation which can be induced by the strong field RSE, are also discussed. Finally, we provide a short summary and prospect of the future studies on the strong field RSE.

Surface discharge of bulk materials investigated from change of charge trap characteristics of polyimide single molecular chain

Surface discharge is one of the reasons for insulation failure. Polyimide (PI) is used in gas-solid insulation of high-frequency electric power equipment. Therefore, based on density functional theory, the effects of single molecular chain structure, energy level, density of states, electrostatic potential, excited state and other micro parameters under external electric field on trap formation and surface discharge of both PI and polar- group- OH<sup>– </sup>affected PI are discussed from the atomic and molecular level. The results show that the structure of PI is crimped and the dipole moment increases under external electric field, which is easy to accumulate charges to form space charge center, especially after the introduction of polar group OH<sup>–</sup>. In the PI molecules, hole traps are formed in the benzene ring region, and electron traps are formed in the imide ring region. The number of electron trap energy levels is large, in which the space charge trap depth gradually deepens with the increase of external electric field. After the introduction of polar group OH<sup>–</sup>, the excitation energy of PI molecules decreases, which makes the electrons inside the molecules excited easily. The spatial separation of electrons and holes decreases with the increase of electric field, which is conducive to the recombination of holes and electrons to emit photons.

Evaluation of effects of molecular chain structure and crystallinity on mechanical properties of polyamide by finite element method using transient network model

Polyamide (PA) is a semi-crystalline polymer in which main chain is configured by repeating units of amide bonds (-NHCO-). The strength of PA is achieved by intermolecular hydrogen bond between hydrogen and oxygen atoms of amide bonds. In this study, the effects of the crystallinity and crystallite size were investigated by uniaxial tensile tests of commercial PA6 and PA-MXD10. Furthermore, the time-dependent nonlinear mechanical model based on the transient network model was proposed to predict the mechanical behavior of PAs with different crystallinities. From experimental results, the stress-strain curves of the PAs with small crystallinity showed the sharp drop after the maximum stress and the necking occurred due to local deformation. In contrast, near the maximum stress of PA with large crystallinity, a gradual change in stress was observed, and the local deformation was suppressed. Simulation results indicated that the modified transient network model can predict the mechanical behavior of PAs with different crystallinities.

An update of label-free protein target identification methods for natural active products.

Natural active products (NAPs) are derived from chemical substances found in nature that have biological activity and medicinal potential. Screening and revealing the protein targets of NAPs is an indispensable link in the pharmacological and toxicological understanding of NAPs. Proteins are the main factors executing cell functions, and cells rely on the function of proteins to complete various activities in the life cycle. The important mechanism of action of drugs is to regulate cell biological activities by interacting with proteins and other macromolecules. At present, the classic way to screen protein targets is based on the molecular label tracing method, which has a long cycle and changes the molecular structure and pharmacological effects of NAPs. Due to the shortcomings of molecular labelling methods, in recent years, scientists have tried to develop a variety of label-free protein target identification methods for NAPs and have made a certain amount of progress. This article reviews the current protein target identification methods for NAPs with the aim of providing a reference for research on NAP protein targets.

Experimental, insilico, DFT studies of novel compound 2-{2-[(3,4-dimethoxyphenyl)methylidene]hydrazinecarbonothioyl}-N-methyl-N- phenylhydrazine-1-carbothioamide

In the current investigation, we have obtained single crystals 2-{2-[(3,4-dimethoxyphenyl)methylidene]hydrazinecarbonothioyl}-N-methyl-N-phenylhydrazine-1-carbothioamide (H2L) by refluxing 3,4 dimethoxybenzaldehyde and N(4)- methyl-N(4)-phenyl thiosemicarbazide. Here we discuss the experimental as well as theoretical studies of the selected molecule. Computational studies were made by Gaussian 09 program. X-ray refinement data of the molecule is used for geometry optimization process using DFT (B3LYP) method with the 6–31 + G (d,p) basis sets. The optimised molecular structure, MEP, NBO, HOMO-LUMO analysis, and NLO effects of 2-{2-[(3,4-dimethoxyphenyl)methylidene]hydrazinecarbonothioyl}-N-methyl-N-phenylhydrazine-1-carbothioamide have been communicated in this paper. NBO analysis gave insight into the strongly delocalized structure, responsible for the nonlinearity and hence the stability of the molecule. H2L obeys Lipinski’s rule, and further in silico assessment of oral bioavailability, ADME, drug-likeness, and medicinal chemistry friendliness proposes that this molecule is a promising candidate for the cancer drug discovery process. Simultaneously, molecular docking of the compound into the 3D crystal structure of ribonucleotide reductase M−2 subunit (PDB ID: 2UW2) and Histone deacetylase 8 (PDB ID 1 T69) have been performed using GLIDE Dock Program. The study has shown that the ligand could be a potential inhibitor for the ribonucleotide reductase M−2 subunit protein.

Attosecond Delays of High-Harmonic Emissions from Hydrogen Isotopes Measured by XUV Interferometer

High-harmonic spectroscopy can access structural and dynamical information on molecular systems encoded in the amplitude and phase of high-harmonic generation (HHG) signals. However, measurement of the harmonic phase is a daunting task. Here, we present a precise measurement of HHG phase difference between two isotopes of molecular hydrogen using the advanced extreme-ultraviolet (XUV) Gouy phase interferometer. The measured phase difference is about 200 mrad, corresponding to ~3 attoseconds ( 1 as = 10 − 18 s ) time delay which is nearly independent of harmonic order. The measurements agree very well with numerical calculations of a four-dimensional time-dependent Schödinger equation. Numerical simulations also reveal the effects of molecular orientation and intramolecular two-center interference on the measured phase difference. This technique opens a new avenue for measuring the phase of harmonic emission for different atoms and molecules. Together with isomeric or isotopic comparisons, it also enables the observation of subtle effects of molecular structures and nuclear motion on electron dynamics in strong laser fields.

SYNTHESIS AND STUDY OF NEW HOMOLOGOUS SERIES: 4-(4’-N-ALKOXY BENZOYLOXY)-NAPTHYL -1-AZO-(2”-METHYL)- 4”-AZO-2”’-METHYL BENZENE

Novel homologous series 4-(4’-n-alkoxy benzoyloxy)- napthyl-1-azo-(2”-methyl)-4”-azo-2”-methyl benzene consisted of 12 members of a series. All the 12 members (ethoxy to hexadecyloxy) are enantiotropically nematogenic without exhibition of any smectogenic character. Transition temperatures and the textures are determinedby an optical polarizing microscopy furnished with a heatingstage. Textures of a nematic phase are threaded or schlieren. Analytical and spectral data supported the molecular structure ofhomologs. Transition curves viz., solid-nematic and nematic-isotropic showing phase behavior of the mesophase in a phase diagrambehave in normal manner. Reversion of transition temperatures is show by N–I transition curve. Hereby, novel series is entirely nematogenic and high to middle ordered melting type. Thus, synthesis of a novel azo ester homologous series is fulfil with a view to understand and establish the effect of molecular structure on Liquid crystal (LC) behaviors of a substance.

Investigation of acidic properties of 2-ethoxy-6-(3-substitue-4,5-dihydro-1H-1,2,4-triazol-5-one-4-yl-azomethine)-phenyl benzoates

In this study, to determine the pKa values of 2-ethoxy-6-(3-substitue-4,5-dihydro-1H-1,2,4-triazol-5-one-4-yl-azomethine)-phenyl benzoates (1-9) were titrated potentiometrically with tetrabutylammonium hydroxide in four non-aqueous solvents such as isopropyl alcohol, tert-butyl alcohol, acetone and N,N-dimethylformamide (DMF), and graphs were drawn for all cases. In addition, the effects of solvents and molecular structure upon acidity compounds 1-9 were also determined and discussed. The half-neutralization potential values and the corresponding pKa values were determined by half neutralization method.