Changes In Substituents Research Articles

Theoretical Study of Three Ratiometric 1,8-naphthalimide Fluorescent Probes for Hydrogen Sulfide Detection.

Three ratiometric 1,8-naphthalimide fluorescent probes for hydrogen sulfide detection have been studied theoretically by using density functional theory and time-dependent functional theory. From the detailed comparison of the optimized geometries, it is found that the change of substituents has a slight effect on the structure of 1,8-naphthalimide fluorophore, and the effect is mainly located in the part attached to the changed substituent. The change of the electron-withdrawing or electron-donating ability of the substituents on the 1,8-naphthalimide has an effect on the electronic spectra. Based on the analysis of frontier molecular orbital, the intramolecular charge transfer process was found for the three probes and their corresponding products. Finally, the analysis of the energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital was elaborated. This work provides a theoretical explanation of the experimental results and thus contributes to the development of novel fluorescent probes in the future.

Exploration of pyridine-thiazolidin-4-one: Synthesis, DFT study, UV–Vis/ fluorescence spectroscopy analysis, antibacterial evaluation and molecular docking

The synthesis of the objective pyridine-thiazolidin-4-one (DCPI-MBT) was involved via the Knoevenagel reaction between 2-((3,5-dichloropyridinyl)imino)thiazolidinone derivative 1 and 4-methylbenzaldehyde 2 over refluxing in acetic acid and sodium acetate. The confirmed structure of this hybrid was elucidated through detailed spectral analyses. A comparison was made between the density functional theory (DFT) configurations of the frontier molecular orbitals in both the gas and solvated ground state (So) and the solvated excited state (S1). UV–Visible and fluorescence spectra of the thiazolidin-4-one derivative were obtained in DMSO, displaying a significant Stokes’ shift (Δν¯= 3136.81 cm−1). The synthesized DCPI-MBT was established to see how well they killed different kinds of pathogenic microbes, such as bacteria, viruses, and fungi. These results demonstrate that the synthesized DCPI-MBT has a broad-spectrum antibacterial capability that is on par with or even superior to conventional treatments in certain instances. Moreover, molecular docking simulation was used to evaluate the bindings of the synthesized DCPI-MBT with a target protein (PDB: 1kzn). The binding energies, RMSD values, kinds of interactions with amino acid residues, and interaction distances of the hybrids were determined based on their substituent changes. This study analyzed the pharmacokinetic profiles of newly DCPI-MBT, using SwissADME predictions to focus on their potential as therapeutic agents. The DCPI-MBT has the promising pharmacokinetic profile for future development as a therapeutic drug, with optimum solubility, bioavailability, and a favorable interaction profile with biological targets.

Design, Synthesis, and Acaricidal Activity of 2,5-Diphenyl-1,3-oxazoline Compounds.

By using a scaffold hopping/ring equivalent and intermediate derivatization strategies, a series of compounds of 2,5-diphenyl-1,3-oxazoline with substituent changes at the 5-phenyl position were prepared, and their acaricidal activity was studied. However, the synthesized 2,5-diphenyl-1,3-oxazolines showed lower activity against mite eggs and larvae compared to the 2,4-diphenyl-1,3-oxazolines with the same substituents. We speculate that there is a significant difference in the spatial extension direction of the substituents between the two skeletons of compounds, resulting in differences in their ability to bind to the potential target chitin synthase 1. This work is helpful in inferring the internal structure of chitin synthase binding pockets.

Fine-tuning the photophysical properties of Imidazo[1,2-a]pyridine-based dyes by the change in substituent and solvent media: DFT and TD-DFT studies

In the present work, photophysical properties of the nine excited-state intramolecular proton transfer (ESIPT) active 2-(2 -hydroxyphenyl)imidazo[1,2-a]pyridine (HPIP)-based dyes A1-A9 (X= H, Me, F, Cl, OMe, OH, CN, NO2 and CF3) were investigated at PBE0/6-31++G(d,p) and M06-2X/6-31++G(d,p) levels of theory in the gas phase and solvent media. The structural parameters, relative energies, vibrational spectra, photophysical properties, potential energy curves, natural bond orbital (NBO) charges, hole and electron isosurfaces, electron density properties and reduced density gradient (RDG) spikes were computed. The H-bonding is strengthened at the S1 state by comparing infrared vibrational spectra, the relevant bond length and bond angle, electron density properties and RDG analysis. The results revealed that ESIPT in the A1-A7 and A9 in the gas phase is a barrier-less process, while there is an energy barrier for the A8 (X=NO2). In polar solvents, it is predicted that the ESIPT process only in A5 and A6 is a barrier-less process. The A2, A4 and A5 exhibited the greatest redshift in the keto fluorescence emission in tetrahydrofuran solvents. The significant Stokes shift observed in the S1-K emission of certain dyes makes these molecules highly appealing for various applications such as chemosensors, fluorescent probes, laser dyes and optoelectronic devices.

Synthesis of Piperazine-containing Derivatives and their Antimicrobial, Antimycobacterial, Antimalarial and Antioxidant Activities

Background: One of the most crucial heterocycles is piperazine for the creation of novel medication candidates with a variety of medicinal applications. The piperazine moiety is a cyclic compound with four carbon atoms and two nitrogen atoms in positions 1 and 4. Objective: The objective of this studty is the development of 1-((3,4-dimethoxyphenyl) (substitutedphenyl) substituted -piperazine (A1-A10) analogs via the one-pot synthesis method and evaluation for their preliminary antibacterial, antifungal, antimycobacterial, antioxidant, and antimalarial activity. Methods: Desired piperazine derivatives were obtained in a single step reaction using piperazine, aldehydes, and boronic acid derivatives. The structures of all newly synthesized compounds have been established based on analytical and spectral data. An in silico molecular docking study was carried out for the series. Results: The spectral data using IR, 1 H NMR, and 13C NMR and mass spectra confirmed the structure of the synthesized compounds. Compounds A6 and A10 were found to be the most promising agents for antimalarial activity. A1-A10 showed a higher IC50 value and found less antioxidant activity. Some of the compounds showed higher potency when compared to the standard drugs in this antimicrobial study. Conclusion: The structure-activity study showed that changes in substituents either on aldehyde, piperazine, or boronic acid derivatives can lead to potential active compounds. These facts make the compounds interesting candidates for further evaluation of their efficacy in the treatment of microbial, tubercular and malarial diseases.

Modification of slow relaxation of magnetization behavior via substituent change on two neutral mononuclear dysprosium(III) single-molecule magnets

Modification of slow relaxation of magnetization behavior via substituent change on two neutral mononuclear dysprosium(III) single-molecule magnets

Resonance Raman study of oxoiron(IV) porphyrin π-cation radical complex: Porphyrin ligand effect on ν(Fe=O) frequency

Resonance Raman (rR) spectroscopy has been applied to study the nature of the iron-oxo (Fe=O) moiety of oxoiron(IV) porphyrin π-cation radical complex (CompI). While the axial ligand effect on the nature of the Fe=O moiety has been studied with rR spectroscopy, the porphyrin ligand effect has not been studied well. Here, we investigated the porphyrin ligand effect on the Fe=O moiety with rR spectroscopy. The porphyrin ligand effect was modulated by the electron-withdrawing effect of the porphyrin substituent at the meso-position. This study shows that the frequency of the Fe=O stretching band, ν(Fe=O), hardly change even when the electron-withdrawing effect of the porphyrin substituent changes. This result is further supported by theoretical calculation of CompI. The natural atomic charge analysis reveals that the oxo and axial ligands work to buffer the electron-withdrawing effect of the porphyrin substituent. The electron-withdrawing porphyrin substituent shifts an electron population from the ferryl iron to the porphyrin, but the decreased electron population on the ferryl iron is compensated by the shift of the electron population from the oxo ligand and the axial ligand. The shift of the electron population makes the Fe–axial ligand bond length short, but the Fe=O bond length unchanged, resulting in the invariable ν(Fe=O) frequency.

Gold and Silver Nanoparticles as Biosensors: Characterization of Surface and Changes in the Adsorption of Leucine Dipeptide under the Influence of Substituent Changes.

Early detection of diseases can increase the chances of successful treatment and survival. Therefore, it is necessary to develop a method for detecting or sensing biomolecules that cause trouble in living organisms. Disease sensors should possess specific properties, such as selectivity, reproducibility, stability, sensitivity, and morphology, for their routine application in medical diagnosis and treatment. This work focuses on biosensors in the form of surface-functionalized gold (AuNPs) and silver nanoparticles (AgNPs) prepared using a less-time-consuming, inexpensive, and efficient synthesis route. This allows for the production of highly pure and stable (non-aggregating without stabilizers) nanoparticles with a well-defined spherical shape, a desired diameter, and a monodisperse distribution in an aqueous environment, as confirmed by transmission electron microscopy with energy-dispersive X-ray spectroscopy (TEM-EDS), X-ray diffraction (XRD), photoelectron spectroscopy (XPS), ultraviolet-visible (UV-VIS) spectroscopy, and dynamic light scattering (DLS). Thus, these nanoparticles can be used routinely as biomarker sensors and drug-delivery platforms for precision medicine treatment. The NPs' surface was coated with phosphonate dipeptides of L-leucine (Leu; l-Leu-C(R1)(R2)PO3H2), and their adsorption was monitored using SERS. Reproducible spectra were analyzed to determine the orientation of the dipeptides (coating layers) on the nanoparticles' surface. The appropriate R2 side chain of the dipeptide can be selected to control the arrangement of these dipeptides. This allows for the proper formation of a layer covering the nanoparticles while also simultaneously interacting with the surrounding biological environment, such as cells, tissues, and biological fluids.

Can a Small Change in the Heterocyclic Substituent Significantly Impact the Physicochemical and Biological Properties of (Z)-2-(5-Benzylidene-4-oxo-2-thioxothiazolidin-3-yl)acetic Acid Derivatives?

Rhodanine-3-acetic acid derivatives are attractive compounds with versatile effects. What is very important is that compounds of this type have many biological properties. They are tested, among others, as fluorescent probes for bioimaging and aldose reductase inhibitors. Rhodanine-3-acetic acid derivatives also have antibacterial, antifungal and anticancer activity. The presented work demonstrates that a slight change in the five-membered heterocyclic substituent significantly affects the properties of the compounds under consideration. Three rhodanine-3-acetic acid derivatives (A-1-A-3) were obtained in the Knoevenagel condensation reaction with good yields, ranging from 54% to 71%. High thermal stability of the tested compounds was also demonstrated above 240 °C. The absorption and emission maxima in polar and non-polar solvents were determined. Then, the possibility of using the considered derivatives for fluorescence bioimaging was checked. Compounds A-1 and A-2 were successfully used as fluorescent dyes of fixed cells of mammalian origin. In addition, biological activity tests against bacteria and fungi were carried out. Our results showed that A-1 and A-2 showed the most excellent antimicrobial activity among the newly synthesized compounds, especially against Gram-positive bacteria.

Charge‐Transfer Modulation of Emissivity in Polarized Diketopyrrolopyrroles

AbstractStrongly polarized donor‐acceptor‐donor′ diketopyrrolopyrroles, differing in the type of key donor moiety, were designed and synthesized to examine how this affects the non‐radiative decay. Dyes possessing less electron‐rich N‐carbazolyl substituents are characterized by strong yellow emission from a locally excited (LE) state, whereas replacing this donor with more electron‐rich N‐phenothiazinyl substituent changes the relative position of charge‐transfer (CT) and LE states, leading to weaker, reddish‐orange fluorescence. As a result, there is solvent‐dependent charge‐transfer emission shifted to as far as 700 nm. The opening of the intersystem crossing channel to the triplet state possessing CT character is the most likely cause of the fluorescence quantum yield variation in some cases. These results reveal that the fate of molecules in their excited state can be fine‐tuned by very small structural changes.

Influence of the length of end-group double bond substituents on the temperature change of phase transition in liquid crystals

ABSTRACT A series of nematic liquid crystal (LC) monomers, containing a reactive group in the lateral substituent, were designed and synthesised through an organic synthesis reaction. Considerable changes were made to the properties of the liquid monomers by varying the terminal alkyl chain lengths. The molecular structures of the intermediates and the LC monomers were characterised by flourier infrared absorption spectrometry and proton nuclear magnetic resonance (1H NMR) spectroscopy, leading to the identification of the target product. The phase transition temperatures of the LC monomers were observed and analysed using differential scanning calorimetry (DSC) and polarising optical microscopy (POM) with a hot stage. The two-way thermotropic liquid crystalline behaviour was observed during the heating process, providing insight into the effect of substituent changes on the phase transition temperature.

Interstitial or interstitialcy: effect of the cation size on the migration mechanism in NaSICON materials.

Sodium superionic conductors (NaSICONs) with general formula NaM2A3O12 have attracted significant attention as solid electrolytes for all solid-state batteries owing to their remarkable room temperature ionic conductivity in the order of 10-3 S cm-1. Their flexible structural framework, which allows the incorporation of various aliovalent cations, affects the Na+ ion transport. However, establishing a straightforward correlation between Na+ mobility and NaSICON composition proves challenging due to competing influences such as framework alteration and stoichiometric changes of the cation substituents and thus the mobile Na+ ions. Therefore, we systematically investigate the NaSICON system across various Na1+xM2SixP3-xO12 compositions. We unravel and examine independently two key aspects impacting the Na+ ion transport in NaSICONs: structural factors determined by introduced M4+ framework cations and the substitution level (x). By employing DFT calculations, we explore the interstitial- and interstitialcy-like migration mechanisms, revealing that these mechanisms and the associated migration energies are primarily influenced by metastable transient states traversed during the Na+ ion migration. The stability of these transient states, in turn, depends on the spatial arrangement of the Na+ ions, the size of the M4+ cations defining the structural framework, and x. This study enhances our fundamental understanding of Na+ ion migration within NaSICONs across a wide range of compositions. The findings offer valuable insights into the microscopic aspects of NaSICON materials and provide essential guidance for prospective studies in this field.

Reaction Mechanism and Effect of Substituent in Direct Bromination of Indoles

AbstractA reaction mechanism for the direct bromination of substituted indoles in dimethylformamide solution at 298.15 K and 1 atm is proposed and studied. It consists of two steps, the first one, in which the lowest unoccupied molecular orbital of Br2 overlaps with the highest occupied molecular orbital of the substituted indole, is the rate‐determining step. A linear correlation is observed between the electron‐withdrawing power of the substituent (expressed through the relative molecular electrostatic potential) and the Gibbs free energy barrier of the reaction‘s rate‐determining step, . This correlation is suggested for estimating in other unexplored cases. The variation of with a change in substituents is primarily governed by electronic factors, but the presence of itself is due to entropic factors. The rate of the bromination reaction under the studied conditions diminishes with a change in the substituent, R, following the order: R=−OCH3, −CH3, −H, −CCH3CH2, −C6H5, −CH2OH, −F, −SCH2CH3, −Cl, −Br, −COCH3, −COOH, −NC, −COH, and −CN.

Novel Series of Peripherally Phthalocyanines (Zn, Pd and Cu): Spectroscopic Studies

Abstract:A new series of metallophthalocyanines (MPc) containing metals such as : Zn (II), Cu (II) and, Pd (II) were designed, synthesized, and characterized, using MS, IR and UV-Vis spectroscopy. A Suzuki cross-coupling reaction was investigated by using the Pd(dppf)Cl2 as a catalyst and cesium carbonate as a base to improve the yield of the precursor 2.6-di(pyridin-3-yl)- phenyl benzyl ether. The changes of metals, substituents, and positions increases the Q-band value from the monosubstituted to the octa-substituted macrocycles, and from Pd, to Cu to Zn complexes. All MPc showed quite similar IR spectra.

Homobimetallic Au(I)-Au(I) and Heterotrimetallic Au(I)-Fe(II)-Au(I) Complexes with Dialkyldithiophosphates and Phosphine Ligands: Structural Characterization, DFT Analysis, and Tyrosinase Inhibitory and Biological Effects.

The role of bridging and terminal ligand electronic and steric properties on the structure and antiproliferative activity of two-coordinated gold(I) complexes was investigated on seven novel binuclear and trinuclear gold(I) complexes synthesized by the reaction of either Au2(dppm)Cl2, Au2(dppe)Cl2, or Au2(dppf)Cl2 with potassium diisopropyldithiophosphate, K[(S-OiPr)2], potassium dicyclohexyldithiophosphate, K[(S-OCy)2], or sodium bis(methimazolyl)borate, Na(S-Mt)2, which afforded air-stable gold(I) complexes. In 1-7, the gold(I) centers adopt a two-coordinated linear geometry and are structurally similar. However, their structural features and antiproliferative properties highly depend upon subtle ligand substituent changes. All complexes were validated by 1H, 13C{1H}, 31P NMR, and IR spectroscopy. The solid-state structures of 1, 2, 3, 6, and 7 were confirmed using single-crystal X-ray diffraction. A density functional theory geometry optimization calculation was used to extract further structural and electronic information. To investigate the possible cytotoxicities of 2, 3, and 7, in vitro cellular tests were carried out on the human cancerous breast cell line MCF-7. 2 and 7 show promising cytotoxicity.

Toward More Efficient Organic Solar Cells: A Detailed Study of Loss Pathway and Its Impact on Overall Device Performance in Low‐Offset Organic Solar Cells

AbstractLow‐offset organic solar cell systems have attracted great interest since nonfullerene acceptors came into the picture. While numerous studies have focused on the charge generation process in these low‐offset systems, only a few studies have focused on the details of each loss channel in the charge generation process and their impact on the overall device performance. Here, several nonfullerene acceptors are blended with the same polymer donor to form a series of low‐offset organic solar cell systems where significant variation in device performance is observed. Through detailed analyses of loss pathways, it is found that: i) the donor:acceptor interfaces of PM6:Y6 and PM6:TPT10 are close to the optimum energetic condition, ii) energetics at the donor:acceptor interface are the most important factor to the overall device performance, iii) exciton dissociation yield can be field‐dependent owing to the sufficiently small energetic offset at the donor:acceptor interface, and iv) the change in substituents in the terminal group of Y‐series acceptors in this work mainly affects energetics at the donor:acceptor interface instead of the interface density in the active layer. In general, this work presents a path toward more efficient organic solar cells.

Role of Polymethinic Chain Substitution on the Two‐Photon Absorption Cross‐section of Heptamethine Cyanine Dyes

AbstractThe effect on the two‐photon absorption of heptamethine cyanines (HMCy) upon polymethinic chain substitution is explained via measurements with a femtosecond laser and time‐dependent/density functional theory calculations. An analysis of the optical properties of several HMCy is presented, emphasizing the similarities and differences between IR780 and HITC (used as a case study of HMCy), mainly by analyzing meso‐substitution and investigating the effect of intermediate structures between both molecules. The two‐photon absorption cross‐section of HITC diluted in methanol was measured, yielding a peak of 1838 GM at 830 nm. Spectroscopic and electronic structure computational data show that the change of polymethine chain substituents significantly affects excited state S4 of the molecules, modulating their transition moment and relative energy which, together with changes in the molecular geometry, govern non‐linear absorption.

Thermodynamic and Structural Effects of Fe Doping in Magnesium Manganese Oxides for Thermochemical Energy Storage

Thermochemical energy storage potentially provides a cost-effective means of directly storing thermal energy that can be converted to electricity to satisfy demand, and MgxMn1–xO4 has been identified as a stable, high-energy density storage material. Here, we investigate the effects of doping small quantities of Fe into the MgMnOx system as a means to increase the reduction extent and storage energy via an increase in entropic contributions and the higher reduction energy of Fe as compared to that of Mn. We find that small additions of Fe (Mg0.5Mn0.4975Fe0.0025)3O4 (Fe = 0.5%) show increased reduction extent, but larger quantities of Fe (Mg0.5Mn0.485Fe0.015)3O4 and (Mg0.5Mn0.475Fe0.025)3O4 (Fe = 3 and 5%) show decreased reduction capability. This finding suggests that small quantities of Fe as a substituent change the thermodynamics of the material increasing the reduction extent through entropic effects, but at larger quantities of Fe, the higher reduction energy of Fe lowers the overall reduction capability. Additionally, the reduction occurs through the formation of intermediate phases which co-occur with the oxidized spinel and reduced halite phases; the presence of Fe significantly narrows the window where the intermediate phase is present, narrowing the T range where most of the reduction occurs. This narrowing thus potentially stabilizes the outlet temperature of a thermochemical energy storage system as compared to undoped (MgxMn1–x)3O4.

Influence of Changing the Remote Substituents on Charge Transfer Properties of Cyanide‐Bridged Trinuclear Fe−Ru−Fe Complexes

AbstractTo investigate the effect of ligand remote (>10 Å) substituents on the bridging metal center on the metal‐to‐metal charge transfer (MMCT) properties in cyanidometa‐bridged complexes, a series of new cyanidometal‐bridged complexes and their one‐electron and two‐electron oxidation products have been synthesized and well characterized (namely, trans‐[Cp(dppe)Fe−NC−(L)Ru(PPh3)−CN−Fe(dppe)Cp][PF6]n (n=2, 3, 4) (L=dmptpy, 1[PF6]n; L=meoptpy, 2[PF6]n; L=t‐Buptpy, 3[PF6]n) (Cp=1,3‐cyclopentadiene, dppe=1,2‐bis(diphenylphosphino)ethane, PPh3=triphenylphosphine, dmptpy=4′‐(4‐dimethylaminophenyl)‐2,2′,6′,2′′‐terpyridine, meoptpy=4′‐(4‐methoxyphenyl)‐2,2′,6′,2′′‐terpyridine, t‐Buptpy=4′‐(4‐tertbutylphenyl)‐2,2′,6′,2′′‐terpyridine)). The investigations suggest that the cyanido‐stretching (νCN) vibration energy for the complexes is unsensitive to the electron‐donating ability change of the remote substituents of the cyanidometal bridging auxiliary ligand from tertbutyl, methoxy to dimethylamino group. However, the MMCT energies of the one‐ and two‐electron oxidation complexes are still sensitive to the remote substituents of the ligand on the bridging metal center, and decreases with the increase of the electron‐donating ability of the remote substituents from tertbutyl, methoxy to dimethylamino group. All one‐electron and two‐electron oxidation products belong to Class II mixed valence compounds according to the classification of Robin and Day.

Solar–Thermal Fuels and the Role of Carbon Nanomaterials: A Perspective with Emphasis on the Azobenzene System

Molecular switches have long been investigated aiming at developing sustainable and renewable energy-based technologies. Among molecular photoswitches, azobenzene (AB) has been the quintessential template for solar–thermal fuels (STFs), acting as “molecular batteries”, storing and discharging energy by converting between its trans- and cis-isomers upon absorption of UV light. Nevertheless, key properties for device performance such as stored energy, energy density, stability of the “charged” metastable isomer, or the control of energy release are highly influenced by a mediating interface. This has motivated the study of metal and carbon nanomaterials as templates in hybrid STFs. The latter have been shown to be especially promising owing to their unique electronic properties, topological tailoring, and abundant sourcing. This review discusses recent advances that explore enhancements on several molecular photoswitch systems, with a special emphasis on the AB system, associated with changes in the molecular substituents and the development of hybrid systems, involving mainly carbon nanotemplates, such as reduced graphene oxide, graphene, carbon nanotubes, and fullerenes. The energy density, τ1/2, grafting density, and charge transfer of the AB and the hybrid adsorbed AB system on carbon nanomaterials are discussed. Key facets of the design of hybrid STF devices are discussed, along with a perspective on the aspects that merit further investigation toward the development of efficient STFs.