Reduced Density Gradient Research Articles

Exploring the Corrosion Potential of Three Bio-Based Furan Derivatives on Mild Steel in Aqueous HCl Solution: An Experimental Inquiry Enhanced by Theoretical Analysis.

This research deals with the corrosion inhibition of mild steel in a highly corrosive aqueous HCl medium with a concentration of 0.5 M, using three different corrosion inhibitors: furan-2-carboxylic acid (1), furan-2,5-dicarboxylic acid (2), and furan-2,5-diyldimethanol (3). Various electrochemical tests, such as potentiodynamic polarization (PP or Tafel curve) and electrochemical impedance spectroscopy, were systematically performed. The experimental results underscore the remarkable corrosion mitigating properties of inhibitors 1-3 on mild steel, showing inhibition efficiencies of 97.6, 99.5, and 95.8%, respectively, at a concentration of 5 × 10-3 M and temperature T = 298 K. Notably, the inhibition efficiency of each inhibitor 1-3 shows a positive correlation with its concentration. In addition, consistent results from all electrochemical methods confirm that 1-3 act as mixed inhibitors. These findings remain robust across different experimental techniques, ensuring the reliability and comprehensiveness of the results. Theoretically, the inhibitors were optimized using the Density Functional Theory/B3LYP/6-311++G(d,p) method in gas and aqueous phase to evaluate their reactivity and stability. Among them, compound 2 stands out for its enhanced reactivity and stability, highlighted by optimal EHOMO and ELUMO values. Negative electrostatic potential mapping suggests potential reaction centers, while Fukui functions reveal localized sites of reactivity, supported by a favorable electronic distribution and specific interactions with metal surfaces. Reduced density gradient analysis also confirms the suitability of this compound for noncovalent interactions, in agreement with experimental data.These theoretical results are in good agreement with experimental data, confirming the excellent performance of compound 2 as a corrosion inhibitor.

Characterization of 1,1- and 1,2-ethenedithiol, elusive compounds of potential astrochemical interest.

1,1- and 1,2-ethenedithiol are elusive systems that could potentially exist in interstellar space, similar to analogous diols. In this paper, we investigate the structure, stability, and bonding characteristics of these compounds as well as the ions produced by protonation, deprotonation, or simple ionization processes. 1,2-ethenedithiol has two isomers, Z and E, with the most stable conformer being syn-anti for the Z isomer and anti-anti for the E isomer. However, the energy gaps between the different conformers are never larger than 6kJ·mol-1. For 1,1-ethenedithiol, the global minimum is the syn-anti conformer. The vertical and adiabatic ionization processes as well as the intrinsic basicities and acidities of these families of compounds were analyzed and compared with those of the corresponding diols previously reported in the literature. This comparison revealed not only the numerical differences in these thermodynamic properties but also distinct trends between the two families of compounds. State-of-the-art G4 ab initio calculations were employed to calculate the structures and total energies of the systems under investigation. The QTAIM, ELF, and NBO approaches were used to analyze the electron density of all the neutral and charged systems included in our study. Van der Waals contributions, when relevant, were analyzed by locating regions of low reduced density gradient(s) using the NCIPLOT approach.

Structure-Activity relationship of 5‑butyl‑4,6-dimethyl-2-{[4-(o-fluorophenyl)-1-piperazinyl]-2-oxoethyl}-pyrrolo[3,4-c]pyrrole-1,3(2H,5H)‑dione: An experimental and theoretical study

Synthesis of 5‑butyl‑4,6-dimethyl-2-{[4-(o-fluorophenyl)-1-piperazinyl]-2-oxoethyl}-pyrrolo[3,4-c]pyrrole-1,3(2H,5H)‑dione 3 is reported. The compound was obtained by direct alkylation of 3,4-pyrrolodicarboximide 1 with (1-chloroacetyl-4-(o-fluorophenyl)piperazine) 2 in DMF. Its physico-chemical features were characterized by 1H NMR, 13C NMR, FT-IR, MS spectra, and elemental analysis. Single-crystal X-ray diffraction was also recorded. A colorimetric inhibitor screening assay was used to determine its inhibitory potency towards COX-1 and COX-2. It was found that the compound exhibits anti-inflammatory activity higher than the reference structure – Meloxicam (MXM). According to the experimental results, the tested compound inhibited the activity of COX-1 and COX-2 respectively. In the next step, molecular docking was performed to estimate the binding affinity of compound 3 and commercially available reference compounds for COX-1/COX-2 enzymes. It was found that the binding affinity of 3 is higher than for the reference compounds. Quantum Theory of Atoms In Molecules (QTAIM) and Reduced Density Gradient (RDG) methods were used to reveal non-covalent interactions present in the COX-1/COX-2 binding pocket. Finally, Born-Oppenheimer molecular dynamics (BOMD) based on semiempirical forces was carried out to gain insight into the dynamic features of the studied complexes and confirmed the fact that the weak hydrogen bonds play the most important role in stabilizing the ligand conformation for the studied COX-2 complexes with compound 3 and Rofecoxib.

Novel AIE and solvatochromism exhibiting TPE based organic fluorophore with excellent emission properties in solid and solution phase for latent fingerprint and metronidazole sensing in real samples

Organic molecules with extended aromaticity are important when designing probes with optical properties. Herein, we designed and synthesized a novel tetraphenylethylene (TPE) based organic molecule TC exhibiting excellent photophysical characteristics. A thorough and in-depth study of the optical properties of probe TC was performed including solvatochromism, aggregation and solid-state studies using ultraviolet–visible (UV Vis) and fluorescence spectroscopy. Also, its optical properties under a UV 365 nm laser were investigated. The compound exhibited aggregation induced emission (AIE) which was thoroughly investigated in a H2O/DMF system and later utilized in formulation of invisible ink and latent fingerprint sensing. Moreover, the excellent emission properties of probe TC were utilized for the highly selective detection of the antibiotic metronidazole (MET) in real samples including human serum and artificial urine. Furthermore, portable TLC and paper-based strips were designed for the on-site detection of MET. Additionally, the mechanism of selective sensing of MET was thoroughly investigated through spectroscopic studies including titration NMR, fluorescence, UV Vis studies and DFT studies. Photoinduced electron transfer (PET) was attributed as the plausible sensing mechanism for the detection of MET. Scanning electron microscopy (SEM) also supported the sensing of MET through change in morphology. DFT calculations involved the measurement of thermodynamic stability, reduced density gradient (RDG) analysis, molecular orbital, and charge transfer studies as well as analysis of quantum theory of atoms in molecules (QTAIM). All the studies supported the presence of non-covalent interactions between probe TC and MET.

Optimizing non-fullerene acceptor molecules constituting fluorene core for enhanced performance in organic solar cells: a theoretical methodology.

Looking for novel outstanding performance materials suitable for organic solar cells, we constructed a range of non-fullerene acceptors (NFAs) evolved from the recently synthesized acceptor molecule identified as DICTIF, structured around fluorene core where 2-(2,3-dihydro-3-oxo-1H-inden-1-ylidene) propanedinitrile presented the terminals end-groups. Employing density functional theory (DFT) and time dependent-DFT (TD-DFT) simulations, we have simulated the impact of altering the end groups of DICTIF molecule by five assorted acceptors molecules, for the purpose of exploring their opto-electronic properties and their performance in organic solar cell (OSC) applications. We proved that the designed non-fullerene acceptors provide enhanced efficiency compared to the synthesized molecule, such as planar geometries and narrower energy gap ranging from 1.51 to 1.95 eV. A red shift in absorption was observed for all tailored molecules (λmax = 583.5-711.4 nm) as compared to the reference molecule (λmax = 578 nm).Various decisive factors such as frontier molecular orbitals (FMOs), exciton binding energy (EB), absorption maximum (λmax), open circuit voltage (VOC), reorganization energies (RE), transition density matrix (TDM), reduced density gradient (RDG), and electron-hole overlap have also been computed for analyzing the performance of NFAs. Low reorganizational energy values facilitate charge mobility which improves the conductivity of all the designed molecules. This study showed that our novel tailored molecules might be suitable candidates for the fabrication of highly efficient photovoltaic materials. After testing various hybrid functionals, optimized geometries were assigned using DFT HSEH1PBE/6-31G(d) level of theory. Electronic excitations and absorption spectra were investigated using the TD-DFT MPW1PW91/6-31G(d) level of theory. We ascertained that HSEH1PBE/6-31G(d) level of theory yield the closest calculated highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of the DICTIF to the corresponding experimental ones and that TD-MPW1PW91//6-31G(d) was the most suitable level of theory for exploring electronic excitations and finding the maximum of absorption (λmax).

Supramolecular assembly mediated through NH···OX (X = C, N, P) hydrogen bonds and Y···π (Y = Br, π) contacts: Structural/computational studies of the P(O)(NHC(O)C6H4-3-NO2)(NHC6H4-3-Br)2 phosphoric triamide

Supramolecular assembly is studied in the structure of N,N'-bis(3‑bromo-phenyl)-N"-(3-nitro-benzoyl)phosphoric triamide, P(O)(NHC(O)C6H4-3-NO2)(NHC6H4-3-Br)2, I, by X-ray crystallography combined with quantum chemical calculations. The asymmetric unit of I is composed of two symmetry-independent molecules that show differences in some torsion angles, especially the ones related to the rotation of amine moieties. The conformations of amine moieties in two molecules are considered based on the resembling P—N—C—C/OP—N—C torsion angles, which associate with the ±sp/+sc conformations in one molecule and –sc/+sp and –sp/–sc conformations in the other molecule (sp = synperiplanar and sc = synclinal). In the crystal structure, the molecules are connected through N—H···OX (X = P, C, N) hydrogen bonds, forming a two-dimensional architecture along the bc plane. The C—H···O/π···π interactions do not change the dimensionality made by N—H···O hydrogen bonds, while the participation of Br···π interactions creates a three-dimensional network. The title structure represents the first observation of Br···π interaction in the C(O)NHP(O)-based family. The methods of Atoms in Molecules (AIM), Natural Bond Orbital (NBO) and Reduced Density Gradient (RDG) are used for the study of noncovalent interactions.

A detailed TD-DFT and intermolecular interaction study of vitamin K in soluble, poorly soluble and insoluble solvents, as well as an ADME and molecular docking study

Vitamin K is one of the most important fat-soluble vitamins and while there are two main types of vitamin K in nature, known as K1 (phylloquinone) and K2 (menaquinones), there is also a synthetic type of vitamin K known as K3 (menadione). Recent studies have shown that it is crucial to know the non-covalent interactions, ADME and molecular docking of molecules in different solvent media. Therefore, we have performed some quantum chemical calculations, ADME and intra-and intermolecular interaction calculations of a number of K1, K2 and K3 such as K1-water (K1 + W), K1-methanol (K1 + M), K1-triacetin (K1 + T), K2-water (K2 + W), K2-methanol (K2 + M), K2-triacetin (K2 + T), K3-water (K3 + W), K3-methanol (K3 + M), K3-triacetin (K3 + T) performed by Density Functional Theory (DFT) and Multiwfn: A multifunctional wavefunction analyzer. Molecular structures, HOMO-LUMO energies, MEP and electronic properties have been calculated and described using DFT at the level of B3LYP/6-311G (d,p) level. The nature of the molecular interactions between vitamin K and solvents such as water, methanol and triacetin were also investigated using topological analyses such as atoms in molecule (AIM), non-covalent interaction index (NCI), reduced density gradient (RDG), Localized orbital locator (LOL) and electron localization function (ELF). In addition, FMO for electronic transitions, MEP for electrophilic and nucleophilic attack, ADME to investigate how a chemical is processed by a living organism, and Fukui functions to determine electron density are explained. Finally, molecular docking was used to determine the biological activity of the vitamin K.

Tunable Properties of New Cyano‐Substituent Heptahelicenes for Optoelectronic Devices: A Combined Experimental and DFT Computational Study

AbstractHere, we describe a set of coupled experimental and theoretical analyses. The introduction of one and two additional cyano groups in the carboheptahelicene backbone enhance its electron‐accepting properties. New carboheptahelicene derivatives are synthesized, and relevant characterizations of structural features, photophysical and electrochemical properties, and structure‐property relationships are described. This present work concerns the use of the density functional theory (DFT) to highlight the structural and the optoelectronic properties of carboheptahelicene derivatives and comparing the obtained findings with the experimental ones. The experimental and theoretical spectra (UV‐Vis absorption and photoluminescence) provide excellent concurrence. Afterward, molecular structures, structural parameters, molecular electrostatic potential (MEP), highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies of frontier molecular orbitals (FMOs) are constructed. Some other optoelectronic parameter including electron affinity (EA), ionization potential (IP), and some reactive descriptor such as chemical potential (μ), global hardness (η), electronegativity (χ) and the overall electrophilicity index (ω) are determined and indicating its potential uses as an active layer in optoelectronic efficient devices. The topological methods such as electron localization function (ELF), localization orbital locator (LOL) and the reduced density gradient method (RDG) were also conducted to clarify the strengths and kinds of interactions.

Investigation of spectroscopic characterization, crystal structure, and antitumor activity of a novel 2ATP molecule

In this section, the spectroscopic characteristics of 2-amino-toysl-pyridine (2ATP) are fully examined, using both experimental and computational investigations guided by density functional theory (DFT). It will facilitate our computational research using the B3LYP approach to use the basis set 6–311++G(d,p). Comprehensive assignments of vibrational modes were obtained from the vibrational spectra, which comprised FT-Raman and FT-IR spectroscopy and were recorded in the region of 3500–400 cm−1 and 4000–500 cm-1, respectively, using the Vibrational Energy Distribution Analysis (VEDA) approach. The net atomic charges inside the molecule were ascertained by using Mulliken population analysis, natural atomic charges, and electrostatic potentials (CHELPG). The structural conformations of 2ATP were determined using NMR spectroscopy in a CDCl3 solvent. The donor-acceptor interactions of the 2ATP molecule at the 6–311++G(d,p) level were studied by means of a Natural Bond Orbital (NBO) study. Studies of the ultraviolet (UV) spectrum in ethanol were used to assess the effects of the solvent. An assessment was made of the energy difference between the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO) in order to understand charge transfer processes that suggest the molecule may have biological activity. Molecular electrostatic potential (MEP) surfaces were used to predict the nucleophilic and electrophilic sites in molecules. The non-covalent interactions were evaluated using the reduced density gradient (RDG) approach. The Multiwfn software was used to analyze the topological properties of the 2ATP, including the Localized Orbital Locator (LOL) and Electron Localization Function (ELF). Further attention was drawn to the compound's exceptional pharmacological potential when its ADMET (Absorption, Distribution, Metabolism, Excretion, and Toxicity) characteristics were evaluated. Not to add, molecular docking experiments were carried out to evaluate the feasibility of 2ATP as a bioactive material with possible uses in the pharmaceutical business.

Crystal structures, NCI-RDG, Hirshfeld surface and energy framework analysis of tetra aryl substitute bispidine and oxaquinuclidine core containing derivatives: A potential COVID-19 drug candidate

Two of the title compounds are crystallized in P21/c and monoclinic face groups. Each crystal unit cell has four molecules. There are two piperidine rings: one in the chair conformation and another one in the boat conformation. The piperidine nitrogen in the boat conformation is joined to the oxygen-containing chair conformation piperidine ring to produce the oxaquinuclidine ring (-N-CH2O-). Furthermore, because of the steric barrier between rings, all aryl groups are oriented in an equatorial position. The crystal network is maintained through several interactions, including C—H⋯O/N/Cl/π. The crystal void and interaction energy studies gave additional evidence of the strength of the crystal packing and intermolecular linkage. Crystal 3b has less cavity than crystal 3c, indicating that it is densely packed. The dispersion energy contribution dominates the stability, according to the analysis of the electrostatic, dispersion, and total energy frameworks. Reduced density gradient (RDG), electron localization function (ELF), and localized orbital locator (LOL) analysis were used to determine the molecular interaction, electron pair density, and maximally localized orbitals overlapping sites, respectively. This approach reveals that oxaquinuclidine ring steric hindrance and the electron densities throughout the molecules. Density function theory (DFT) provides more evidence for the ring's orientation and the molecules' reactivity. A molecular docking investigation of four essential COVID-19 proteins was carried out using these theoretical ideas. This investigation demonstrates that each protein's reactivity varies; certain proteins have more interaction with high electron density molecules (electron-donating substituent), while others have more interaction with low electron density molecules (electron-withdrawing substituent). The ADMET and drug-likeness investigations reveal that methoxy group substituted molecules perfectly correlate with the required pharmacological characteristics. The cytotoxicity of the five compounds was assessed using the HEK293T cell.

Quasi-hydrophobic deep eutectic solvents for simultaneous automated determination of polar and non-polar dyes in food products

In this work, quasi-hydrophobic deep eutectic solvents were used for the first time for the efficient extraction of both polar (Sunset Yellow FCF (E 110), Azorubine (E122), Ponceau 4R (E124)) and non-polar (Sudan I, Sudan II, Sudan III) dyes from food products at the same time. These solvents were made from polar and nonpolar components, which made it possible to extract analytes of various natures. To automate the technique, a flow analysis method was used, which increases the speed and reliability of determining analytes in food samples. For a detailed study of extraction mechanisms, various process modeling methods were used. The proposed DES-based method addresses the limitations of traditional extraction methods, offering a more robust and efficient solution for food analysis. Validation of the method has demonstrated high precision, accuracy and extraction efficiency, making it a promising tool for regulatory compliance and consumer safety in the food industry. The following analytical characteristics were achieved: the limits of detection were 0.03–0.13 mg L−1, limits of quantification were 0.09–0.44 mg L−1, an extraction recovery exceeding 85 %, a linear range was from 1 to 100 mg L−1, and a relative standard deviation ranging from 2 % to 10 %. The experiments were confirmed by both Conductor Like Screening Model-Segment Activity Coefficient (COSMO-SAC) and the Non-Covalent Interaction using the Reduced Density Gradient of the DES-dye system in aqueous media.

Synthesis, spectroscopic characterization, electronic elucidation, chemical reactivity, topological and molecular docking investigations of cefadroxil sulfoxide

The cefadroxil sulfoxide (CDSO) para-hydroxy derivative, derived from cefadroxil, has enormous significance in pharmaceutical applications. The cefadroxil sulfoxide (CDSO) compound was synthesized and characterized by spectroscopic (FT-IR, FT-Raman, and UV–Visible) assessments. Computational investigations have been carried out concurrently with a B3LYP-6-311++G(d,p) basis set and density functional theory (DFT). The molecular vibrational assignments, chemical reactivity, electronic properties, and optical activities are calculated using gas and different solvent phases. The stable ground state configuration of the given molecular compound is investigated using PES analysis. Furthermore, the chemical behavior of the CDSO was thoroughly investigated for different solvent aspects through HOMO-LUMO, MEP, UV–Visible and electron-hole excitation analyses. The molecular occupancy, virtual occupancy, and overlapping bonding energies are investigated by TDOS, PDOS, and COOP spectrum studies. Fukui function and dual descriptor investigations extend to the chemical reactivity of individual atomic sites. The intra-molecular analysis provided a deeper understanding of the molecular interactions performed by natural bond orbitals (NBO) and non-linear optics (NLO), which provided optical activity for the title compound. Additionally, electron localization function (ELF), localized orbital locator (LOL), and reduced density gradient (RDG) analyses were also accomplished to provide insight into the delocalized orbitals in the header composite. The molecular docking was achieved, and the ligand with 4EVM protein is providing the potential antimicrobial biological activity (binding energy −7.12 kcal/mol) of the CDSO compound.

DFT-aided stereo-structural and electronic structure studies of poly-hydroxyl substituted chlorophyllous molecules

Numerous chlorophyll-based derivatives have found applications in the dye and pharmaceutical industries. Here, we report the synthesis of a poly-hydroxyl substituted chlorophyll molecule (THM) and its absolute configuration determination using experimental electron circular dichroism (ECD), nuclear magnetic resonance (NMR) spectroscopy, and density functional theory (DFT) calculations. Furthermore, the photoreaction types of THM (type I and type II) were investigated through theoretical calculations and validated by biological experiments. We provide a detailed analysis of electron transfer and excitation processes in THM through theoretical calculation of hole-electron distribution, as well as study intramolecular weak interactions and conjugation effects using Reduced Density Gradient (RDG), Interaction Region Indicator (IRI), and Natural Bond Orbital Analysis (NBO). The photoreaction types (type I, type II) of THM in tumor cells have also been investigated by biological experimental measures and theoretical calculation of the single-triplet state energy gap and hole-electron distribution. Molecular electrostatic potential has also been investigated by DFT methods to give insight into the molecular structure. This study provides useful guidance for the structural and photochemical studies of the chlorophyll-derived photodynamic therapeutic drugs.

FT-IR, UV–Vis, density functional theory and molecular docking studies on 3,7,11,15-Tetramethyl-2hexadecen-1-ol

The organic molecule of 3,7,11,15-Tetramethyl-2-hexadecen-1-ol is frequently present in plant chlorophyll pigment. The title compound possesses antimicrobial, antibacterial, antioxidant, anti-inflammatory, and anticancer characteristics. The 3TMH molecule are being investigated using Gas Chromatography Mass Spectrometry (GC–MS) analysis, Ultraviolet-Visible (UV–Vis), Fourier Transform Infrared Spectroscopy (FT-IR), and Density Functional Theory (DFT) approach with the Becke,3-parameter, Lee–Yang–Parr (B3LYP) method, 6–311++G (d, p) basis set is used to analyse the geometrical parameters, Highest Occupied Molecular Orbital and the Lowest Unoccupied Molecular Orbital (HOMO-LUMO), and Molecular Electrostatic Potential (MEP) mapping. In the 3TMH molecules, the computed Natural Bond Orbital (NBO) analysis exhibit the high stabilization interaction (intra-inter, hydrogen bonding, and charge delocalization) between the donor and acceptor. The UV–Vis spectra of the maximum absorption correlated with different solvents as determined by Time-Dependent Density Functional Theory (TD-DFT). According to Veda 04, the measured FT-IR spectrum and the theoretical spectra of vibrational assignment with Potential energy distribution (PED%) are in good agreement. The Electron Localization Function (ELF) and Localized Orbital Locator (LOL) mapping has provided an explanation for the chemical bonding within fragments, as well as interactions between the atoms. The strong attraction, strong repulsion, and weak interaction have been estimated Reduced Density Gradient (RDG). Furthermore, the molecular docking examined ligand-protein interaction of least binding energy 6.73 kcal/mol against anti-cancer activity.

Photophysical Response of Propranolol in Biomimetic Micellar Media of Alkyltrimethylammonium Bromide Surfactants: Effect of pH and Alkyl Chain Length.

The photophysical behavior of a β-blocker drug propranolol (PPL) in micellar environments, formed by alkyltrimethylammonium bromide surfactants viz.; Cetyltrimethylammonium bromide (CTAB), Tetradecyltrimethylammonium bromide (TTAB), and Dodecyltrimethylammonium bromide (DTAB), has been investigated through fluorescence and UV-visible spectroscopic techniques at pH levels of 3.5, 7.4, and 10.4. The impact of pH on the critical micelle concentration (cmc) and micropolarity of micelles were assessed using pyrene as a photophysical probe. The cmc values were found to be lower at pH 10.4 compared to pH 7.4 and pH 3.5. Fluorescence emission intensities of PPL at 323nm, 338nm, and 352nm were significantly influenced by pH, hydrophobic alkyl chain length of surfactants, and their concentrations. Quenching experiments with Cetylpyridinium chloride (CpCl) indicated the localization of charged and uncharged forms of PPL within micelles, with quenching constant (Ksv) values dependent on alkyl chain length and pH. At pH < pKa, PPL is positioned near the Stern layer, whereas at pH 10.4, its naphthalene moiety resides near the hydrophobic micellar core. UV spectroscopy showed that the charged form of PPL interacted with micelles only above cmc, while the neutral form interacted even below the cmc. Density Functional Theory (DFT) reveals the HOMO of the surfactants to be localized on the hydrocarbon chains, and the LUMO localized around the quaternary ammonium unit. Upon complexation with PPL, both HOMO and LUMO shifted to the drug, thereby decreasing energy levels. The findings are explained based on weak noncovalent interactions, further supported and analyzed through Reduced Density Gradient (RDG) and Noncovalent Interaction (NCI) methods, confirming synergistic non-covalent interactions in surfactant-PPL complexes.

Interaction between Halogenated Phenols and Thyroxine‐Binding Protein: A Multispectral and Computational Approach

AbstractThe aim of this study was to understand the interaction between transthyretin (TTR) and halogenated phenols (HPs) including 2,4‐dichlorophenol (DCP), 2,4,6‐trichlorophenol (TCP), pentachlorophenol (PCP), 2‐bromophenol (2‐BP), 2,4‐dibromophenol (DBP) and 2,4,6‐tribromophenol (TBP). Computer simulation and multi‐spectroscopy techniques were used to investigate the interaction. The fluorescence of TTR was found to be quenched through static quenching and non‐radiative energy transfer by HPs, suggesting that the binding process between HPs and TTR was primarily influenced by van der Waals forces and hydrogen bonds. ANS substitution experiments indicated that HPs interacted with TTR at the T4 binding site. Three‐dimensional fluorescence spectra and Fourier transform infrared spectroscopy were used to investigate the conformational and microenvironmental changes of TTR resulting from the interactions with HPs. Additionally, molecular docking and reduced density gradient analysis were used to identify the specific residues and binding forces involved in the interaction between HPs and TTR binding sites. The findings were subsequently validated through quantum chemical analysis. This research integrates state‐of‐the‐art multispectral analytical methodologies with sophisticated computational modeling to introduce an innovative approach for dissecting the interactions between halogenated phenols (HPs) and transthyretin (TTR). This methodology offers a novel avenue for investigating the molecular interplay between HPs and TTR, thereby providing critical insights that are instrumental in assessing the latent toxicity of these compounds.

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.

Theoretical description of hydride-hydride interactions in selected hydrogen storage materials.

The high content of hydride-hydride contacts Hδ-···δ-H in hydrogen storage materials appears to be relevant for hydrogen formation. At present time there is no consensus whether these contacts are attractive or repulsive. Accordingly, the main goal of this article is to shed light on physical factors which constitute homopolar hydride-hydride interactions Hδ-···δ-H in selected transition metal complexes i.e. HCoL4, L = CO,PPh3,PH3. In order to achieve this goal, the charge and energy decomposition ETS-NOCV approach along with the Interacting Quantum Atoms (IQA) and reduced density gradient (NCI) are applied for the bonded adducts L4CoH···HCoL4. Based on DFT and correlated methods it has been shown, that hydride-hydride interactions might be attractive and even far stronger than classical hydrogen bonds. The stability of the adducts is increased by phosphine ligand installation: overall Hδ-···δ-H bonding energy changes in the order: CO << PPh3 ~ PH3. It has been revealed that depending on monomer's conformations Hδ-···δ-H bonds are dominated by charge delocalization or London dispersion forces and the electrostatic term is also relevant. It is finally determined by IQA energy decomposition, that diatomic hydride-hydride interaction CoH···HCo is chameleon-like, namely, it is attractive in CO4CoH···HCoCO4, whereas the repulsion is unveiled in (CO)3(PPh3)CoH···HCo(CO)3(PPh3).

Theoretical Analysis of Superior Photodegradation of Methylene Blue by Cerium Oxide/Reduced Graphene Oxide vs. Graphene.

Density functional theory and a semi-empirical quantum chemical approach were used to evaluate the photocatalytic efficiency of ceria (CeO2) combined with reduced graphene oxide (rGO) and graphene (GP) for degrading methylene blue (MB). Two main aspects were examined: the adsorption ability of rGO and GP for MB, and the separation of photogenerated electrons and holes in CeO2/rGO and CeO2/GP. Our results, based on calculations of the adsorption energy, population analysis, bond strength index, and reduced density gradient, show favorable energetics for MB adsorption on both rGO and GP surfaces. The process is driven by weak, non-covalent interactions, with rGO showing better MB adsorption. A detailed analysis involving parameters like fractional occupation density, the centroid distance between molecular orbitals, and the Lewis acid index of the catalysts highlights the effective charge separation in CeO2/rGO compared to CeO2/GP. These findings are crucial for understanding photocatalytic degradation mechanisms of organic dyes and developing efficient photocatalysts.

Investigations of fluorescence emission Mechanism: Formation of ring-like structures by interactions influenced by hydroxyl group and deprotonation

As one of the gaseous signaling molecules in biological systems, hydrogen sulfide(H2S) is involved in numerous physiological processes and diseases. Therefore, rapid, effective, and real-time detection of H2S is of great importance. Based on its excellent optical properties, dicyanoisophorone has attracted much attention in recent years, and a large number of corresponding probes have been developed to detect H2S in biological systems. In this paper, the fluorescence mechanisms of three dicyanoisophorone-based fluorescent probes are investigated and the near-infrared (NIR) fluorescence attribution of the products is discussed by density-functional theory and time-dependent density-functional theory methods. Frontier molecular orbital analysis shows that the non-fluorescence of the probes is attributed to the photo-induced electron transfer process. Structural change and reduced density gradient analyses indicate that the position of the hydroxyl group and the deprotonation have a non-negligible influence on the interactions within the products. The five- or six-membered ring-like structures formed by interactions make the molecule stain as a planar and the fluorescence emission, while the twist exists the fluorescence quenching. In addition, spectral information shows that the emission of NIR fluorescence originates from the deprotonated form of the product.