Conductor-like Polarizable Continuum Model Research Articles

Two-photon absorption in bioactive C4-substituted Coumarin derivatives: Impact of electron-withdrawing and donating groups in different environment

The versatile applications of coumarin derivatives in materials processing, fluorescence imaging, data storage, and photodynamic therapy have sparked considerable interest in scientific community. In this research paper, we explore the UV–vis spectra, IR spectra, and two photon absorption (TPA) characteristics of biological active coumarin derivatives under the influence of electron withdrawing (specifically X = CONH2, CHO, and NO2) and electron donating (X= -CH3, -OH, -NH2) functional groups at C-4 position. To delve into the absorption spectra, we employ time-dependent density functional theory calculations. Results revealed that acceptor functional groups (specifically R = CONH2, CHO, and NO2) not only lower the energy of the lowest two photon active state but also increase the corresponding TPA cross-section. Furthermore, using the Conductor-like Polarizable Continuum Model (CPCM), the influence of solvent polarity on C-4 substituted coumarin derivative was also investigated. Our findings effectively capture how substitutions and solvents impact the nonlinear optical response in coumarins, as evidenced by the measurement of the two-photon absorption cross-section (σTPA). This study offers valuable insights for identifying and designing novel coumarin derivatives with C4 substitutions, unlocking new and intriguing possibilities for their practical applications.

Insight on relationship between crystallinity and band gap energies of polyhydroxyalkanoates polymers

This study explores the electronic properties of polyhydroxyalkanoates (PHAs), a class of biodegradable polymers. The focus lies in examining the relationship between crystallinity and band gap energies in PHAs. A notable discovery is the identification of a band gap plateau, suggesting a threshold in electronic properties with increasing polymer chain length. DFT calculations were employed to model the complexities of PHA polymers, with the conductor-like polarizable continuum model (CPCM) offering insights into solvent effects. The results demonstrate a strong negative correlation between crystallinity and band gap in both vacuum and CPCM environments. This study underscores the significance of structural order in shaping the electronic properties of PHAs, paving the way for the development of sustainable polymeric materials for various applications.

Theoretical Evaluation of Fluorinated Resazurin Derivatives for In Vivo Applications.

Primarily owing to the pronounced fluorescence exhibited by its reduced form, resazurin (also known as alamarBlue®) is widely employed as a redox sensor to assess cell viability in in vitrostudies. In an effort to broaden its applicability for in vivo studies, molecular adjustments are necessary to align optical properties with the near-infrared imaging window while preserving redox properties. This study delves into the theoretical characterisation of a set of fluorinated resazurin derivatives proposed by Kachur et al., 2015 examining the influence of fluorination on structural and electrochemical properties. Assuming that the conductor-like polarisable continuum model mimics the solvent effect, the density functional level of theory combining M06-2X/6-311G* was used to calculate the redox potentials. Furthermore, (TD-)DFT calculations were performed with PBE0/def2-TZVP to evaluate nucleophilic characteristics, transition states for fluorination, relative energies, and fluorescence spectra. With the aim of exploring the potential of resazurin fluorinated derivatives as redox sensors tailored for in vivo applications, acid-base properties and partition coefficients were calculated. The theoretical characterisation has demonstrated its potential for designing novel molecules based on fundamental principles.

A theoretical approach to the corrosion inhibition of iron in acidic solution by a green formulation derived from Nigella sativa L seeds oil

A theoretical approach combining density functional theory (DFT) computation, Monte Carlo (MC) methods, and molecular dynamics (MD) simulations was used to investigate and validate the iron corrosion inhibition performances in the acidic medium of a green formulation based on the oil extracted from Nigella sativa L. DFT calculations allowed to determine the energetic, global, and local chemical reactivity parameters. The most stable adsorption configuration of the fatty acids components of the Nigella sativa L. formulation was determined by the Monte Carlo methods with the adsorption locator module and by molecular dynamics simulations. Results indicated that all the compounds are absorbed with a totally flat orientation on the first layer of the metal surface.The active sites of molecules were effectively established by using DFT through the analysis of frontier molecular orbitals (FMO), the Hirshfeld population analysis (HPA), the electrostatic potential (ESP), molecular electron density analysis (MED), and Fukui indices (FI). The solvent effect was investigated by using the conductor-like polarizable continuum model (CPCM). Protonation effects were also analysed through the protonation energy (PE), the proton affinity (PA), and the absolute gas phase basicity (GB). The formation of a coating on the iron surface validated the good protective action of the green formulation derived from Nigella sativa L.The computational and theoretical approaches substantiate our experimental electrochemical and spectroscopic studies [1].

Computational-based investigation of antioxidative potential polyphenolic compounds of Salvia officinalis L.: combined DFT and molecular docking approaches.

The antioxidant properties of the three polyphenolic compounds (carnosol, cirsiliol, and luteolin) of Salvia officinalis L. were investigated employing the density functional theory (DFT) calculations at the B3LYP of basis set at 6-311 + + G (d, p) in order to evaluate their antioxidant activity. The enthalpies of reactions associated with the SET-PT, SPLET, and HAT mechanisms were analyzed in gas and in different solvents using the CPCM (conductor-like polarizable continuum) model. For all possible hydrogen donor sites, the corresponding parameters (BDE, AIP, PDE, PA, ETE, HOMOs, and LUMOs) and reactivity indices (IPE, EA, Χ, η, S, and ω) were also evaluated. The calculated results showed that derivatives 12-OH, 11-OH, 4'-OH, and 3'-OH had the lowest antioxidant activity. The results showed as well that carnosol, cirsiliol, and luteolin have higher reactivity compared to ascorbic acid and could be considered better antioxidants. According to research, the catechol group is crucial in influencing the studied compounds antioxidant activity. The theoretically predicted order of antioxidant efficiencies in this work agrees well with the QSAR (quantitative structure-activity relationship) data. The findings show that in the vacuum as well as benzene media. HAT would be the most effective mechanism; in contrast, the thermodynamic equilibrium approach in polar media is the SPLET mechanism. Likewise, the outcomes of the docking modeling confirm that the selected molecules have high inhibitory activity to glutathione-S-transferases (GSTs) receptors. Moreover, they have very important pharmacokinetic, chemical, and biological profiles. Finally, all the results show that the three natural molecules have good pharmacokinetic profiles, particularly the bioavailability and permeability toward biological membranes. The software packages used in this investigation are Gaussian 16, Discovery studio Visualizer, and AutoDock vina. The three compounds (carnosol, cirsiliol, and luteolin) of Salvia officinalis L. were optimized with DFT/B3LYP of basis set at 6-311 + + G (d, p). The optimized structures were established via vibrational analysis (i.e., no imaginary frequencies in the frequency set). All enthalpies were zero-point (ZPE) corrected. Vibrational frequency calculations were performed at 298.15K and 1 atmosphere pressure to determine the thermodynamic characteristics of the investigated reactions. The descriptors were associated with the antioxidant mechanisms for investigated molecules in vacuum and in various solvents. The molecular docking was used by AutoDock vina to estimate and evaluate the title compounds compatibility as potential antioxidant drugs utilizing appropriate receptor proteins. The solvation effect in the medium of benzene (ɛ = 2.27) and water (ɛ = 78.39) was taken into account. Furthermore, a methanol solvent (ɛ = 32.61) was also taken into consideration to compare with the empirical data.

Electronic structure and molecular properties of nitisinone and mesotrione in water

ContextNitisinone is a medium-sized organic molecule that is used in treating hereditary tyrosinemia type 1 (HT-1). The structurally analogous mesotrione, however, is used as a pesticide/herbicide. What molecular properties are responsible for the similarity/dissimilarity of these molecules is investigated here. The solvent effect reduces the electron affinity to rather negative values and causes the negative electron affinity which manifests itself in a very high positive absolute reduction potential.MethodsB3LYP method was utilized for a geometry optimization of nitisinone and mesotrione in their neural and ionized (L0, L+, L−) forms of 6 structures. The calculations were conducted in water as a solvent using conductor-like polarizable continuum model (CPCM), nitisinone also in vacuo. The complete vibrational analysis at the true energy minimum allows evaluating the thermodynamic functions with focus to the zero-point energy and overall entropic term. The change of the Gibbs energy on reductions and/or oxidation facilitates evaluating the absolute reduction and absolute oxidation potentials. Also, DLPNO-CCSD(T) method that involves the major part of the correlation energy has been applied to nitisinone and mesotrione and their molecular ions.

Structure of 2-nitro-2’-hydroxy-5’-methylazobenzene: Theoretical and spectroscopic study

Objectives. 2-Hydroxy-nitroazobenzenes comprise reagents for the synthesis of heteroaromatic compounds, in the molecules of which the benzene and azole cycles are annulated. These reagents are widely used in the production of chemical products for various industries. In particular, 2-2’-hydroxy-5’-methylphenylbenzotriazole is used as an effective photo stabilizer for polystyrene and polyethylene. A promising method for its preparation is the liquid-phase catalytic hydrogenation of 2-nitro-2'-hydroxy-5'-methylazobenzene (2NAB). The aim of the present study was to establish the structure of 2NAB in solutions of different composition.Methods. Theoretical calculations were carried out within the framework of the density functional theory at a temperature of 298.15 K for the gas phase at B3LYP/6-311++G(d, p) and M06-2X/6-311++G(d, p) levels; for hexane, 2-propanol, toluene at B3LYP/6-311++G(d, p) level using the conductor-like polarizable continuum model. An experimental study to determine the probable isomeric structure of 2NAB in various solvents, including sodium hydroxide (NaOH) and acetic acid (CH3COOH) additives, was carried out using infrared (IR) and ultraviolet (UV) spectroscopy.Results. The most probable structure of 2NAB isomers for the gas phase and a number of solvents was determined. Experimental and theoretical IR and UV spectra were obtained. The thermodynamic characteristics of the reaction of intramolecular proton transfer from –OH to –N=N– group in the gas phase were calculated.Conclusions. A comparison of the experimental and calculated results supports the conclusion that the cis-isomer should be considered most probable for the gas phase. For the studied solutions, a trans-isomer of 2NAB with hydrogen bonds formed between the hydroxyl group hydrogen and the β-nitrogen atom of the azo group of dye molecule should be considered as the most likely structure. In the studied individual and binary solvents, prototropic equilibrium is shifted towards the azo form of the dye, while intramolecular proton transfer is possible only in aqueous diethylamine and dimethylformamide solutions with additions of NaOH.

Structure of 2-nitro-2’-hydroxy-5’-methylazobenzene: Theoretical and spectroscopic study

Objectives. 2-Hydroxy-nitroazobenzenes comprise reagents for the synthesis of heteroaromatic compounds, in the molecules of which the benzene and azole cycles are annulated. These reagents are widely used in the production of chemical products for various industries. In particular, 2-2’-hydroxy-5’-methylphenylbenzotriazole is used as an effective photo stabilizer for polystyrene and polyethylene. A promising method for its preparation is the liquid-phase catalytic hydrogenation of 2-nitro-2'-hydroxy-5'-methylazobenzene (2NAB). The aim of the present study was to establish the structure of 2NAB in solutions of different composition.Methods. Theoretical calculations were carried out within the framework of the density functional theory at a temperature of 298.15 K for the gas phase at B3LYP/6-311++G(d, p) and M06-2X/6-311++G(d, p) levels; for hexane, 2-propanol, toluene at B3LYP/6-311++G(d, p) level using the conductor-like polarizable continuum model. An experimental study to determine the probable isomeric structure of 2NAB in various solvents, including sodium hydroxide (NaOH) and acetic acid (CH3COOH) additives, was carried out using infrared (IR) and ultraviolet (UV) spectroscopy.Results. The most probable structure of 2NAB isomers for the gas phase and a number of solvents was determined. Experimental and theoretical IR and UV spectra were obtained. The thermodynamic characteristics of the reaction of intramolecular proton transfer from –OH to –N=N– group in the gas phase were calculated.Conclusions. A comparison of the experimental and calculated results supports the conclusion that the cis-isomer should be considered most probable for the gas phase. For the studied solutions, a trans-isomer of 2NAB with hydrogen bonds formed between the hydroxyl group hydrogen and the β-nitrogen atom of the azo group of dye molecule should be considered as the most likely structure. In the studied individual and binary solvents, prototropic equilibrium is shifted towards the azo form of the dye, while intramolecular proton transfer is possible only in aqueous diethylamine and dimethylformamide solutions with additions of NaOH.

Rational design of co-ordination compounds in combination of bipyridine type of ligands and group 7 metal (M = Mn, Re) for photoCORM: a DFT study.

A large number of manganese and rhenium tricarbonyl complexes are known in literature along with various applications in different fields. CO-releasing molecules (CORMs) got recent research attention because CO can act as a prodrug for different diseases. CORMs offer the promising prospect of a safe and controllable amount of CO release. In this research work, we have explored the electronic properties of compounds such as bipyridine-related [Mn(CO)3] and [Re(CO)3] and we have compared the electronic properties of both manganese and rhenium tricarbonyl complexes in the light of carbon monoxide releasing tendency. The chosen Mn and Re metals have enough possibility to vary or play with ligands and design a new and novel CORM molecule. In this context, we have taken a range of 4,4'-disubstituted 2,2' bipyridyl ligands (Rbpy, where R = NH2, tBu, OCH3, H, CF3, CN, NO2) to investigate CO's liberation ability to identify and study such molecules. The calculated absorbance of designed complexes (1-14) shows visible/near-IR region (350-850 nm). The HOMO-LUMO energy gap of 7 (ΔE=2.40 eV) complex and for complex 14 (ΔE=2.28 eV) which is lesser in all complexes but the MLCT percentage is greater in Mn tricarbonyl complexes in comparison to Re tricarbonyl complexes. The calculated results of the FMO approach revealed that complex 7 and 14 have the lowest energy gap which is also in good agreement with DOSs and TDM results. The theoretically calculated results revealed that the both Mn and Re tricarbonyl complexes have a tendency for labialization of CO, but Mn tricarbonyl complexes are more prone to CO release because they have higher MLCT percentage. In this research work, we have performed density functional theory (DFT) calculations to explore the physical properties of compounds such as bipyridine-related [Mn(CO)3] and [Re(CO)3] and we have compared the physical properties of both manganese and rhenium tricarbonyl complexes in the light of carbon monoxide releasing tendency. DFT-based calculations were performed by using B3LYP/LANL2DZ basis set followed by acetonitrile solvent using the conductor-like polarizable continuum model (CPCM) for different calculations. Various geometrical calculations were performed using the Gaussian16 suite of programs and the output results obtained from Gaussian16 were visualized using GaussView 5.0.16. The same level of theory was used for various calculations, including frontier molecular orbital (FMO) analysis, metal to ligand charge transfer (MLCT), density of state (DOS) calculations, and transition density of matrix (TDM) calculations. For specific calculations, GaussSum 2.2 software package was used to calculate the density of states, and the Multiwfn 3.8 program was used to analyze the transition density matrix, which is presented using heat maps for both electrons and holes.

Design, synthesis, and density functional theory studies of a new selective chemosensor for Pb2+

Herein, we have focused on a new colorimetric ligand synthesized from the reaction of 2-hydroxy-5-methylbenzene-1,3-dialdehyde with 2-amino-thiophenol, and investigated its activity as a sensor. In this regard, the sensory activity of the ligand towards different ions (Mn2+, Cu2+, Co2+, Fe2+, Fe3+, Zn2+, Ni2+, Cd2+, Ag+, Na+, Cs+, Mg2+, Al3+, Ba2+, K+, and Pb2+) was studied. The specificity of ion bindings is discussed through UV–Vis analysis. The ligand that was synthesized showed remarkable sensitivity, with a detection limit of 0.001 ppb. Additionally, the presence of Pb2+ ions can be visually detected through a color change from colorless to yellow. In the last part of this work, we seek to predict the available experimental measurements. Density functional theory (DFT) and quantum theory of atoms in molecules (QTAIM) are employed to examine the bonding between the ligand and the Pb2+ ion. The effect of water solvent was thoroughly examined for all the steps via the conductor-like Polarizable Continuum Model (CPCM). The theoretical findings revealed that electronic properties, including energy gap, adsorption energy, charge/energy transfer, and optical characteristics, undergo significant changes when Pb2+ cations are present. Hence, it can be inferred that the newly synthesized chemosensor (NC) is highly efficient in detecting Pb2+.

Resonance Raman spectra and excited state properties of methyl viologen and its radical cation from time-dependent density functional theory.

Time-dependent density functional theory (TDDFT) was applied to gain insights into the electronic and vibrational spectroscopic properties of an important electron transport mediator, methyl viologen (MV2+ ). An organic dication, MV2+ has numerous applications in electrochemistry that include energy conversion and storage, environmental remediation, and chemical sensing and electrosynthesis. MV2+ is easily reduced by a single electron transfer to form a radical cation species (MV•+ ), which has an intense UV-visible absorption near 600 nm. The redox properties of the MV2+ /MV•+ couple and light-sensitivity of MV•+ have made the system appealing for photo-electrochemical energy conversion (e.g., solar hydrogen generation from water) and the study of photo-induced charge transfer processes through electronic absorption and resonance Raman spectroscopic measurements. The reported work applies leading TDDFT approaches to investigate the electronic and vibrational spectroscopic properties of MV2+ and MV•+ . Using a conventional hybrid exchange functional (B3-LYP) and a long-range corrected hybrid exchange functional (ωB97X-D3), including with a conductor-like polarizable continuum model to account for solvation, the electronic absorption and resonance Raman spectra predicted are in good agreement with experiment. Also analyzed are the charge transfer character and natural transition orbitals derived from the TDDFT vertical excitations calculated. The findings and models developed further the understanding of the electronic properties of viologens and related organic redox mediators important in renewable energy applications and serve as a reference for guiding the interpretation of electronic absorption and Raman spectra of the ions.

Extended Conductor-like Polarizable Continuum Solvation Model (CPCM-X) for Semiempirical Methods.

We have developed a new method to accurately account for solvation effects in semiempirical quantum mechanics based on a polarizable continuum model (PCM). The extended conductor-like polarizable continuum model (CPCM-X) incorporates a computationally efficient domain decomposition conductor-like screening model (ddCOSMO) for extended tight binding (xTB) methods and uses a post-processing approach based on established solvation models, like the conductor-like screening model for real solvents (COSMO-RS) and the universal solvent model based on solute electron density (SMD). According to various benchmarks, the approach performs well across a broad range of systems and applications, including hydration free energies, non-aqueous solvation free energies, and large supramolecular association reactions of neutral and charged species. Our method for computing solvation free energies is much more accurate than the current methods in the xtb program package. It improves the accuracy of solvation free energies by up to 40% for larger supramolecular association reactions to match even the accuracy of higher-level DFT-based solvation models like COSMO-RS and SMD while being computationally more than 2 orders of magnitude faster. The proposed method and the underlying ddCOSMO model are readily available for a wide variety of solvents and are accessible in xtb for use in various computational applications.

A high-level quantum chemical study of the thermodynamics associated with chlorine transfer between N-chlorinated nucleobases

The relative free energies of the isomers formed upon N-chlorination of each nitrogen atom within the DNA nucleobases (adenine, guanine, and thymine) have been obtained using the high-level G4(MP2) composite ab initio method (the free energies of the N-chlorinated isomers of cytosine have been reported at the same level of theory previously). Having identified the lowest energy N-chlorinated derivatives for each nucleobase, we have computed the free energies associated with chlorine transfer from N-chlorinated nucleobases to other unsubstituted bases. Our results provide quantitative support pertaining to the results of previous experimental studies, which demonstrated that rapid chlorine transfer occurs from N-chlorothymidine to cytidine or adenosine. The results of our calculations in the gas-phase reveal that chlorine transfer from N-chlorothymine to either cytosine, adenine, or guanine proceed via exergonic processes with ΔG o values of −50.3 (cytosine), −28.0 (guanine), and −6.7 (adenine) kJ mol–1. Additionally, we consider the effect of aqueous solvation by augmenting our gas-phase G4(MP2) energies with solvation corrections obtained using the conductor-like polarizable continuum model. In aqueous solution, we obtain the following G4(MP2) free energies associated with chlorine transfer from N-chlorothymine to the three other nucleobases: −58.4 (cytosine), −26.4 (adenine), and −18.7 (guanine) kJ mol–1. Therefore, our calculations, whether in the gas phase or in aqueous solution, clearly indicate that chlorine transfer from any of the N-chlorinated nucleobases to cytosine provides a thermodynamic sink for the active chlorine. This thermodynamic preference for chlorine transfer to cytidine may be particularly deleterious since previous experimental studies have shown that nitrogen-centered radical formation (via N–Cl bond homolysis) is more easily achieved in N-chlorinated cytidine than in other N-chlorinated nucleosides.

C-PCM study on the electronic and optical properties of Fe(CO)4B12N12 complexes

We explored solvent effect on the stability, dipole moment, polarizability and first hyperpolarizability of Fe(CO)4B12N12 complexes at MPW1PW91/6-311G(d,p) level of theory. These complexes were considered in the low spin states. The self-consistent reaction field theory (SCRF) based on conductor-like polarizable continuum model (PCM) was employed to illustration of the solvent influences. The relations between the parameters with solvent polarity functions (McRae and Suppan functions) were given. Also, relations of the wavenumbers values of the stretching of carbonyl ligands with the Kirkwood–Bauer–Magat equation (KBM) were provided.

Analytical derivative couplings within the framework of time-dependent density functional theory coupled with conductor-like polarizable continuum model: Formalism, implementation, and applications.

The nonadiabatic phenomena, which are characterized by a strong coupling between electronic and nuclear motions, are ubiquitous. The nonadiabatic effect of the studied system can be significantly affected by the surrounding environment, such as solvents, in which such nonadiabatic process takes place. It is essential to develop the theoretical models to simulate these processes while accurately modeling the solvent environment. The time-dependent density functional theory (TDDFT) is currently the most efficient approach to describe the electronic structures and dynamics of complex systems, while the polarizable continuum model (PCM) represents one of the most successful examples among continuum solvation models. Here, we formulate the first-order derivative couplings (DCs) between the ground and excited states as well as between two excited states by utilizing time-independent equation of motion formalism within the framework of both linear response and spin flip formulations of TDDFT/CPCM (the conductor-like PCM), and implement the analytical DCs into the Q-CHEM electronic structure software package. The analytic implementation is validated by the comparison of the analytical and finite-difference results, and reproducing geometric phase effect in the protonated formaldimine test case. Taking 4-(N,N-dimethylamino)benzonitrile and uracil in the gas phase and solution as an example, we demonstrate that the solvent effect is essential not only for the excitation energies of the low-lying excited-states but also for the DCs between these states. Finally, we calculate the internal conversion rate of benzophenone in a solvent with DC being used. The current implementation of analytical DCs together with the existing analytical gradient and Hessian of TDDFT/PCM excited states allows one to study the nonadiabatic effects of relatively large systems in solutions with low computational cost.

TDDFT versus GW/BSE Methods for Prediction of Light Absorption and Emission in a TADF Emitter.

Design concepts for organic light emitting diode (OLED) emitters, which exhibit thermally activated delayed fluorescence (TADF) and thereby achieve quantum yields exceeding 25%, depend on singlet-triplet splitting energies of order kT to allow reverse intersystem crossing at ambient temperatures. Simulation methods for these systems must be able to treat relatively large organic molecules, as well as predict their excited state energies, transition energies, singlet-triplet splittings, and absorption and emission cross sections with reasonable accuracy, in order to prove useful in the design process. Here we compare predictions of TDDFT with M06-2X and ωB97X-D exchange-correlation functionals and a GoWo@HF/BSE method for these quantities in the well-studied DPTZ-DBTO2 TADF emitter molecule. Geometry optimization is performed for ground state (GS) and lowest donor-acceptor charge transfer (CT) state for each functional. Optical absorption and emission cross sections and energies are calculated at these geometries. Relaxation energies are on the order of 0.5 eV, and the importance of obtaining excited state equilibrium geometries in predicting delayed fluorescence is demonstrated. There are clear trends in predictions of GoWo@HF/BSE, and TDDFT/ωB97X-D and M06-2X methods in which the former method favors local exciton (LE) states while the latter favors DA CT states and ωB97X-D makes intermediate predictions. GoWo@HF/BSE suffers from triplet instability for LE states but not CT states relevant for TADF. Shifts in HOMO and LUMO levels on adding a conductor-like polarizable continuum model dielectric background are used to estimate changes in excitation energies on going from the gas phase to a solvated molecule.

Evaluation of darrow red-organosilane composite as a photosensitizer for application in dye-sensitized zinc oxide photocatalysts: DFT and TD-DFT studies.

Density functional theory (DFT) and time-dependent DFT (TD-DFT) studies of darrow red covalently attached to 3-glycidyloxypropyltrimethoxysilane (DR-GPTMS) were conducted, and it was shown that DR-GPTMS can be applied as a photosensitizer in dye-sensitized zinc oxide (ZnO) photocatalysts. The frontier molecular orbital (FMO) levels of DR-GPTMS simulated using a conductor-like polarizable continuum model in water were suitable for electron injection from photoexcited DR-GPTMS to ZnO. Additionally, the oxidized DR-GPTMS produced by electron injection can be regenerated using triethanolamine. UV-visible absorption spectra, FMOs, and density of states spectra of DR-GPTMS adsorbed on the Zn2O3 cluster were also investigated to understand the mechanism of electron injection. The results suggest that DR-GPTMS induces good visible-light absorption and efficient electron injection to ZnO. DFT and TD-DFT calculations were performed using the Gaussian 09W package (Gaussian, Inc., Wallingford, CT, USA). The density of states spectra was obtained using GaussSum (3.0.2). The B3LYP/6-31G** level of theory was employed for all calculations except for the UV-visible absorption spectra simulation. In calculations involving ZnO, the LanL2DZ or SDD basis set was assigned to the zinc atoms. TD-DFT calculations were performed at the eight different functionals (B3LYP, PBE0, M06-L, M06, M06-2X, M06-HF, CAM-B3LYP, and ωB97XD) with the 6-31+G** basis set. A conductor-like polarizable continuum model (CPCM) using water was employed determining the solvent effect.

Solvent selection in membrane preparation from polyethylene terephthalate plastic waste: computational and experimental study

The selection of the solvent during the membrane preparation process significantly affects the characteristics of the resulting membrane. The large number of organic solvents available for dissolving polymers renders this experimental approach ineffective. A computational approach can select a solvent using the solvation energy value approach. In addition, no organic waste is generated from the computational approach, which is a distinct advantage. A computational approach using the DFT/B3LYP/def2-TZVP RIJCOSX method was used to optimize the structure of polyethylene terephthalate (PET). The PET for the experiment was obtained from the utilization of plastic bottle waste. In addition, a review of the thermodynamics, geometry, HOMO-LUMO orbitals, and vibrational frequencies was conducted to validate the PET molecule against the experimental results. A conductor-like polarizable continuum model was used to determine the best solvent for dissolving the PET plastic waste. The results demonstrated that the Fourier Transform Infra-Red and Fourier Transform Raman spectra obtained from computational calculations were not significantly different from the experimental results. Based on a thermodynamic approach, computationally the Gibbs free energy (−724.723), entropy (0.0428), and enthalpy (−724,723 Kjmol−1 ) values of the PET dimer molecule are not much different from the experimental values (−601, 0.042, and −488 Kjmol−1). The computational approach was successful in selecting solvents that can dissolve PET plastic bottle waste. Phenol solvent has the lowest solvation energy value (−101.879 Kjmol−1) and the highest binding energy (2.4 Kjmol−1) than other solvents. Computational and experimental results demonstrated that the phenol solvent was able to dissolve PET plastic bottle waste better than the other solvents.

Synthesis and Unusual Reactivity of Acyl-Substituted 1,4-Disilacyclohexa-2,5-dienes.

In continuation of our recent studies on group 14 rings with exocyclic silicon-carbon double bonds, we report here on the synthesis and reactivity of previously unknown acyl-substituted 1,4-disilacyclohexa-2,5-dienes. 1,1,4,4-Tetrakistrimethylsilyl-1,4-disilacyclohexa-2,5-diene 1 cleanly afforded the silyl anion 1-K after addition of 1 equiv of KO t Bu. 1-K subsequently could be reacted with various electrophiles to the expected substitution products including compounds 4 and 5. When photolyzed with λ > 300 nm radiation, 4 and 5 undergo Brook-type 1,3-Si → O migration reactions to generate the corresponding 1,4-disilacyclohexadienes with exocyclic Si=C bonds as the primary products. These metastable silenes only could be characterized in form of appropriate quenching products. The reaction of compound 4 with KO t Bu followed by the addition of 1 equiv of PhMe2SiCl surprisingly gave the silylated 1,4-disilanorbornadiene cages 8 and 9 instead of the expected exocyclic silene. The responsible sila-Peterson-type mechanism could be elucidated by density functional theory calculations at the conductor-like polarizable continuum model (THF) B3LYP-GD3/6-31 + G(d) level and by the isolation and characterization of unstable intermediate products after proper derivatization.

Impacts of polarizable continuum models on the SCF convergence and DFT delocalization error of large molecules.

Advances in algorithm developments have enabled density functional theory (DFT) description of large molecules, including whole proteins, but the self-consistent field (SCF) convergence issues often hamper practical applications. The conductor-like polarizable continuum model (CPCM), although initially introduced as an implicit solvent model, was reported to improve SCF convergence in some large molecules. However, the underlying mechanisms and applicable use cases were unclear. We investigated the impacts of CPCM on the SCF convergence of 25 peptides and found that the CPCM only effectively reduced the SCF iterations for molecules with charge separations (e.g., the zwitterionic form of peptides) but had little effect on non-charge-separated molecules. We observed that CPCM increased the HOMO-LUMO gap of both the zwitterionic and non-charge-separated molecules, but only the charge-separated molecules suffered from the vanishing HOMO-LUMO gap problem in the gas phase, which is the origin of the convergence issue. We revealed CPCM's gap-opening mechanism as the selective stabilization/destabilization of molecular orbitals (MOs) based on their local electrostatic environment. Compared to level-shifting, a traditional SCF improvement technique, CPCM has superior performance because the stabilization/destabilization of MOs is consistent through SCF iterations. Finally, we examined CPCM's impacts on DFT density delocalization error (DDE) when used as an SCF accelerator. CPCM can mitigate the DDE and reproduce the density-derived properties (e.g., dipole moments) matching high-level methods when a very low dielectric constant is used but tends to over-localize the electron density at higher dielectric constants.