Polarizable Continuum Model Research Articles

An implicit electrolyte model for plane wave density functional theory exhibiting nonlinear response and a nonlocal cavity definition.

We have developed and implemented an implicit electrolyte model in the Vienna Ab initio Simulation Package (VASP) that includes nonlinear dielectric and ionic responses as well as a nonlocal definition of the cavities defining the spatial regions where these responses can occur. The implementation into the existing VASPsol code is numerically efficient and exhibits robust convergence, requiring computational effort only slightly higher than the original linear polarizable continuum model. The nonlinear + nonlocal model is able to reproduce the characteristic "double hump" shape observed experimentally for the differential capacitance of an electrified metal interface while preventing "leakage" of the electrolyte into regions of space too small to contain a single water molecule or solvated ion. The model also gives a reasonable prediction of molecular solvation free energies as well as the self-ionization free energy of water and the absolute electron chemical potential of the standard hydrogen electrode. All of this, combined with the additional ability to run constant potential density functional theory calculations, should enable the routine computation of activation barriers for electrocatalytic processes.

Role of the Solvent and Intramolecular Hydrogen Bonds in the Antioxidative Mechanism of Prenylisoflavone from Leaves of Vatairea guianensis.

This work discusses the electron structure, antioxidative properties, and solvent contribution of two new antioxidant molecules discovered, named S10 and S11, extracted from a medicinal plant called Vatairea guianensis, found in the Amazon rain-forest. To gain a better understanding, a study using density functional theory coupled with the polarizable-continuum model and the standard 6-311++G(d,p) basis set was conducted. The results indicate that S10 has a higher antioxidant potential than S11, confirming the experimental expectations. In the gas phase, the hydrogen atom transfer route dominates the hydrogen scavenging procedure. However, in the water solvents, the antioxidant mechanism prefers the sequential proton loss electron transfer mechanism. Furthermore, the solvent plays a fundamental role in the antioxidant mechanism. The formation of an intramolecular OH···OCH3 hydrogen bond is crucial for accurately describing the hydrogen scavenging phenomenon, better aligning with the experimental data. The results suggest that the two isoflavones investigated are promising for the pharmacologic and food industries.

Role of explicit hydrogen bonding in solvation calculation on the photophysics of 2-(2′-Hydroxyphenyl)oxazolo[4,5-b]pyridine

The photophysics of 2-(2′-hydroxyphenyl)oxazolo[4,5-b]pyridine (HPOP) was theoretically examined by employing the integral equation formalism variant of polarizable continuum model (PCM) at the level of density functional theory with M06 functional. Polar protic methanol and water and aprotic acetonitrile and tetrahydrofuran, which have varied dielectric constants, were considered to study the role of polarity on the photophysics of HPOP and was compared with the results obtained in vacuum. Six different structural forms of HPOP were observed: cis and trans-closed enol, cis and trans-open enol, and cis and trans-keto. cis-closed enol is the most stable and trans-keto the least in the ground state. In the S1 state, cis-keto is the most stable and cis-open enol the most unstable. The relative stabilities of the different structures increase with the polarity of the solvent. The calculations were extended to vacuum and methanol environments by adding two methanol molecules, and similarly done with two water molecules in vacuum and water environments which are explicitly hydrogen bonded to HPOP at different hydrogen bonding centres of HPOP to study the role of solute–solvent hydrogen bond on its photophysics and the changes in results obtained under the PCM formalism. The hydrogen bond between the solute and solvent molecules further increases the relative stabilities of the different hydrogen bonded clusters. The calculations show that the intramolecular proton transfer (IPT) between cis-closed enol and cis-keto is a barrierless process with the transition state displaying a submerged barrier both in S0 and S1 states where the IPT occurs within a single OH stretching vibration. The IPT trajectory is shorter in the S1 state.

A Geometric Approach for the Calculation of the Nonrandomness Factor Using Computational Chemistry.

The nonrandomness factor (α) is a parameter related to the polarity (and consequent randomness of spatial orientation) of the molecules and is generally fixed between 0.20 and 0.47 since no technique has been developed so far for its accurate estimation. However, the consideration of a constant nonrandomness factor for mixtures is known to harden azeotrope description and to cause convergence issues in both the Nonrandom Two-Liquid (NRTL) and Universal Quasi-chemical (UNIQUAC) models, which have been widely applied in the correlation of phase equilibria. In this work, a novel geometric methodology, named Porto's approach, was applied in the calculation of the nonrandomness factors for 50 pure components (mainly alkanes, alcohols, and ketones) at 298.15 K and 0.1 MPa. This methodology relied on computational chemistry (Density Functional Theory, DFT) to minimize the energy of molecules in a cavity within a solvent composed of molecules of their own (applying the Polarizable Continuum Model, PCM), and thereafter define the most stable chemical configuration in the pure liquid state. Then, the nonrandomness factor of each component was determined based on its molecular dipole moment, which was calculated after a population analysis of the optimized partial electrical charges with the Natural Bond Orbital (NBO) function. This innovative approach was applied in the correlation of liquid-liquid equilibria (LLE) data for 15 ternary systems comprising only neutral molecules with NRTL and UNIQUAC. The classical methods (α = 0.2 or 0.3 for NRTL and α = 0.2 for UNIQUAC) were compared against the usage of a component-specific nonrandomness factor, and similar standard deviations were obtained. Hence, this work is considered a strong advance in the application of these excess free Gibbs energy models to phase equilibria estimation and opens the door to more accurate thermodynamic modeling of nonideal mixtures (such as the ones containing electrolytes) by providing enhanced physical meaning to the nonrandomness factors.

Cluster-Based Approach Utilizing Optimally Tuned TD-DFT to Calculate Absorption Spectra of Organic Semiconductor Thin Films.

The photophysics of organic semiconductor (OSC) thin films or crystals has garnered significant attention in recent years since a comprehensive theoretical understanding of the various processes occurring upon photoexcitation is crucial for assessing the efficiency of OSC materials. To date, research in this area has relied on methods using Frenkel-Holstein Hamiltonians, calculations of the GW-Bethe-Salpeter equation with periodic boundaries, or cluster-based approaches using quantum chemical methods, with each of the three approaches having distinct advantages and disadvantages. In this work, we introduce an optimally tuned, range-separated time-dependent density functional theory approach to accurately reproduce the total and polarization-resolved absorption spectra of pentacene, tetracene, and perylene thin films, all representative OSC materials. Our approach achieves excellent agreement with experimental data (mostly ≤0.1 eV) when combined with the utilization of clusters comprising multiple monomers and a standard polarizable continuum model to simulate the thin-film environment. Our protocol therefore addresses a major drawback of cluster-based approaches and makes them attractive tools for OSC investigations. Its key advantages include its independence from external, system-specific fitting parameters and its straightforward application with well-known quantum chemical program codes. It demonstrates how chemical intuition can help to reduce computational cost and still arrive at chemically meaningful and almost quantitative results.

Investigating the molecular crystals of L-Alanine, DL-Alanine, β-Alanine, and Alanine hydrogen chloride: Experimental and DFT analysis of structural and optoelectronic properties

In this study, DFT calculations were employed to assess and contrast the structural, electronic, and optical characteristics of five alanine crystal forms. The Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA) with the Tkatchenko-Scheffler dispersion correction scheme was employed and compared to the PBE functional and the local density approximation (LDA) without dispersion correction. Experimentally, alanine crystal powders were characterized through X-ray diffraction (XRD) and UV–VIS absorption spectrum. Additionally, UV–VIS absorption measurements were performed on L-α-alanine, DL-alanine, β-alanine, and alanine hydrochloride solvated in water. Significant deviations (>10%) were observed between the experimental crystal lattice parameters and those predicted by the GGA and LDA methods. Incorporating dispersion correction into the GGA functional improved prediction accuracy. Additionally, time-dependent DFT (TD-DFT) computations using the polarizable continuum model were conducted to analyze the UV/VIS absorption spectrum of α-, β-, DL-, and hydrogen chloride alanine in water and interpret experimental data. Different alanine crystals exhibited substantial anisotropic electronic and optical properties, including effective masses, absorption, and dielectric function. The L-α-HCl structure displayed the smallest band gap (4.67 eV), suggesting its suitability for applications such as L-α/L-α-HCl/L-α quantum well structures. The main effective masses of electrons and holes were also determined for each crystal for a better understanding of their electronic transport properties.

Quantifying plasmonic characteristics of pure and alkali doped aluminium clusters

Study of plasmonic response of molecules and metal nanoclusters have drawn a considerable attention during recent times due to their various practical applications. In this study, the optical properties and the plasmonic response of our recently reported Al13+ cluster [Guin et al. Journal of Molecular Graphics and Modelling, 2020, 97, 107544] and its alkali doped counterparts [Guin et al. Journal of Molecular Modeling, 2021, 27, 235] have been investigated based on Transition dipole moment (TDM), Natural Transition Orbital (NTO) and transition inverse participation ratio (TIPR) indices. Recently these indices have been utilized by various scientists to characterize plasmonic transitions of molecular systems and metal nanoclusters. In TDM analysis, the magnitude of all the contributing TDMs associated with the molecular orbital transitions have been estimated along with the angles the individual dipoles make with the resultant dipole moment vector. A transition having at least two dominating TDM contributions along with phase matching indicate a collective or plasmonic transition. The collectiveness of orbital transitions is also corroborated through NTO and TIPR analysis. The effect of solvent medium on the optical properties and plasmonic transitions have also been studied using time dependent density functional theory in the conductor like polarizable continuum model (TDDFT-CPCM). The solvent has a strong impact on the optical properties as well as the plasmonic response of the clusters. The dielectric environment of the solvent red shifts and broadens the spectra with respect to that in the gas phase. Plasmon like excitations have been found for Li doped Al13+ cluster without solvent and Na doped Al13+ cluster in ethanol and THF.

Does the Intersystem Crossing Rate of β-Iodinated Phosphorus Corrole Depend on Iodine Numbers and/or Positions?

The heavy-atom effect is known to enhance the intersystem crossing (ISC) in organic molecular systems. Effects of iodine numbers and positions on the ISC rate of a few meso-difluorophenyl substituted β-iodinated phosphorus corroles (PCs) with axially ligated fluorine atoms (mI-FPC; m = 1-4) are studied using a time-dependent optimally tuned range-separated hybrid. Solvent effects are accounted for through a polarizable continuum model with a toluene dielectric. Calculations suggest similar thermodynamic stability for all mI-FPCs and also reproduce the experimentally measured 0-0 energies for some of the freebase phosphorus corrole (FPC) systems studied here. Importantly, our results reveal that all mI-FPCs display 10 times larger ISC rate (∼109 s-1) than the fluorescence rate (∼108 s-1), and the higher ISC rate stems from the improved spin-orbit coupling (SOC) introduced by lighter heteroatoms like central P and biaxial F rather than the I heavy-atom effect. However, an enhanced SOC is found with increasing I content for El-Sayed forbidden ISC channels. Research findings reported in this study unveil the impact of light heteroatoms and heavy atoms in promoting ISC in several iodinated PCs, which help in designing visible-light-driven efficient triplet photosensitizers.

Molecular structure, electronic properties, spectroscopic, quantum computational studies of 1-(4-hydroxy-3-methoxyphenyl)ethanone-effective anticancer medicine

The molecular structure of 1-(4-hydroxy-3-methoxyphenyl) ethenone has been optimized, and its various parameters were ascertained, using Density Functional Theory. The molecule’s Fourier Transform-Infra Red and Raman spectra are recorded and examined. By comparing the computational and experimental results, molecular structure, bond length, and vibrational band intensity were all interpreted. The Integral Equation Formalism polarizable continuum model’s depictions of electronic and Frontier Molecular Orbital solvent interaction investigations are sported to perceive the charge transfer among the atoms of the molecule in eco-green solvents such as water, acetone, and ethanol. The reactivity sites can be studied by locating and charting the electron density on the surface. The compound’s hardness, softness, electrophilicity, and ionization potential were all analyzed. The pharmacological effects and intra-molecular hyper conjugative interactions are liable for its molecular stability, as shown by Natural Bond Orbital research. Topological studies, including Electron Localized Function, Localized Orbital Locator, and Reduced density gradient analysis, were performed to locate the compound’s bonding area and Vander Waals interactions. Urea was used as a reference compound to examine the substance’s non-linear optical characteristics. Total Density of States has investigated the role of molecular orbitals. Drug-likeness, a Ramachandran plot, and molecular docking were also performed to further analyze 1-(4-hydroxy-3-methoxyphenyl) ethanone’s biological activity. The docking results lend credence to the idea that the title compound could function as a powerful cancer treatment.

Vibrational spectra, molecular level solvent interaction, stabilization, donor- acceptor energies, thermodynamic, non-covalent interaction and electronic behaviors of 6-Methoxyisoquinoline- anti tubercular agent

The present research is a theoretical examination of 6-methoxyisoquinoline implementing Density Functional Theory quantum mechanical approach. Structural optimization was performed to achieve a stable molecular structure with the least amount of energy. Several protic and aprotic solvent interactions were performed using the IEF polarization continuum model to examine the reactivity and stability of the molecules. Molecular interactions with solvents were investigated using UV–Visible, HOMO-LUMO, MEP, NBO, and NLO properties, which shows some changes in the compound activity at solvent phases against gas phase. The molecular interaction of π*C1–N2 to π*C5 - C10 shows the higher stabilizing energy. DMSO solvent exhibits a very low band gap energy, favors the molecule's high stability. Molecular reactivity, interactions, and optical behavior were all readily apparent. The chemical reactivity of the compound was found good in water. The percentage of PED contributions was evaluated for each mode of vibrations using vibrational spectral investigation. Topological surface analysis was used for better understanding of molecular electron density, reactive center, and steric effect. ELF, LOL, and RDG was generated for compounds with different solvents. The distance of transition and the overlapping of electron and hole were calculated using electron hole analysis. Pharmacological assessments include drug likeness, ADME, toxicity, and a pre-ADMET online tool, which supports the biological capability of the compound. Finally, molecular docking with anti-tubercular protein was performed, and a Ramachandran plot of chosen protein was shown to explore stability.

Effect of number of donor–acceptor repeat units and macrocyclic configuration on excited state properties in TADF emitters: A multiscale theoretical study

Thermally Activated Delayed Fluorescent (TADF) molecules with Donor (D) -Acceptor (A) –Donor-Acceptor π-Conjugated Macrocycle structures have broad application potential in organic light-emitting diodes. In this paper, three D − A line type and one D − A − D − A π‑Conjugated Macrocycle molecules with same donor and acceptor groups are investigated using polarizable continuum model (PCM) combined with density functional theory (DFT) and time-dependent functional theory (TD-DFT) in solvent and film. It is found that the macrocyclic structure has a smaller energy gap (ΔEST) between the first singlet excited state (S1) and the first triplet excited state (T1) than the linear structure. The TADF efficiency is also analyzed based on the calculation of spin–orbit coupling (SOC) and the (reverse) intersystem crossing (RISC) rates between S1 and T1. The macrocyclic molecules have larger SOC and faster RISC rates, which also well explains the experimental predictions and results.

Theoretical Study of the Photophysical and Photochemical Properties of 1H‐Benzimidazole and 2‐Ethyl‐7‐nitro‐5‐Substituted 1H‐Benzimidazoles

AbstractTheoretical study of the photophysical/photochemical properties of 1H‐benzimidazole and its derivatives was carried out using APFD, B3LYP, CAM‐B3LYP and PBE0 density functionals with 6‐311+G(2d,p) basis set. The effects of ethanol, 1,4‐dioxane, acetonitrile and water was investigated by means of Integral Equation Formalism of the Polarizable Continuum Model (IEPCM) in the framework of Self‐Consistent Reaction Field (SCRF). The results obtained show that S2 state of the 1H‐benzimidazole molecule is more acidic than the S0 state as the N5−H11 bond length increased to ~ 1.01 Å. At B3LYP/6‐311+G(2d,p) level of theory, the excitation energy of 1H‐bensimidazole molecule in ethanol from S0 to the S2 state was calculated to be 273 nm (4.54 eV). The electronic energy for this transition was calculated to be 0.131 a.u. and observed to occur between π→π* orbitals. Calculations with the PBE0, APFD and B3LYP functionals reproduced the experimental dipole moment in 1,4‐dioxane, with values of 4.09, 4.09 and 4.07 Debye respectively. However, the dipole moments of the 2‐ethyl‐7‐nitro‐5‐substituted‐1H‐benzimidazoles were calculated to be higher for electron donating groups (EDGs) than those bearing electron withdrawing groups (EWGs). In addition, the molecular polarizability was observed to increase with decreasing energy gap. Local excitation (LE) and charge‐transfer (CT) were observed to mediate the mechanisms of electronic excitation in 2‐ethyl‐7‐nitro‐5‐substituted‐1H‐benzimidazoles.

Specific versus Nonspecific Solvent Interactions of a Biomolecule in Water.

Solvent interactions, particularly hydration, are vital in chemical and biochemical systems. Model systems reveal microscopic details of such interactions. We uncover a specific hydrogen-bonding motif of the biomolecular building block indole (C8H7N), tryptophan's chromophore, in water: a strong localized N-H···OH2 hydrogen bond, alongside unstructured solvent interactions. This insight is revealed from a combined experimental and theoretical analysis of the electronic structure of indole in aqueous solution. We recorded the complete X-ray photoemission and Auger spectrum of aqueous-phase indole, quantitatively explaining all peaks through ab initio modeling. The efficient and accurate technique for modeling valence and core photoemission spectra involves the maximum-overlap method and the nonequilibrium polarizable-continuum model. A two-hole electron-population analysis quantitatively describes the Auger spectra. Core-electron binding energies for nitrogen and carbon highlight the specific interaction with a hydrogen-bonded water molecule at the N-H group and otherwise nonspecific solvent interactions.

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.

Conformational distributions of tetrahydro-2-turoic acid in water at different pH values by their IR and vibrational circular dichroism spectra

Infrared (IR) and vibrational circular dichroism (VCD) spectra of tetrahydro-2-furoic acid (THFA) in aqueous solutions under several different pH conditions were recorded. To interpret the IR and VCD spectra of THFA obtained in highly acidic and basic aqueous solutions, extensive and systematic conformational searches were conducted to acquire the low-energy minima for both the neutral and deprotonated forms of THFA species, as well as their hydrated clusters. This was accomplished by using the conformer-rotamer ensemble sampling tool (CREST) with an implicit solvation model for water. The CREST candidates were further optimized at the B3LYP-D3BJ/def2-TZVP level of theory. The simulated VCD spectra of the neutral THFA conformers in the polarizable continuum model (PCM) of water alone exhibit little agreement with the experimental data under highly acidic conditions. Applying the clusters-in-a-liquid solvation model by considering the monohydrate THFA conformers in the PCM of water, significantly improved agreement with the experimental data. Similarly, the deprotonated THFA species solvated with one to four explicit water molecules in the PCM of water were considered. While the IR and VCD spectra of the deprotonated THFA monohydrate conformers offer the best agreement with the experimental data, other larger hydrated clusters, particularly the dihydrates, also contribute to the spectra. Through the synergistic combined experimental and theoretical approach used in the study, comprehensive conformational distributions of the predominant THFA species across various pH conditions were extracted.

Assessing Implicit and Explicit Polarizable Solvation Models for Nuclear-Electronic Orbital Systems: Quantum Proton Polarization and Solvation Energetics.

Accurate simulations of many chemical processes require the inclusion of both nuclear quantum effects and a solvent environment. The nuclear-electronic orbital (NEO) approach, which treats electrons and select nuclei quantum mechanically on the same level, combined with a polarizable continuum model (PCM) for the solvent environment, addresses this challenge in a computationally practical manner. In this work, the NEO-PCM approach is extended beyond the IEF-PCM (integral equation formalism PCM) and C-PCM (conductor PCM) approaches to the SS(V)PE (surface and simulation of volume polarization for electrostatics) and ddCOSMO (domain decomposed conductor-like screening model) approaches. IEF-PCM, SS(V)PE, C-PCM, and ddCOSMO all exhibit similar solvation energies as well as comparable nuclear polarization within the NEO framework. The calculations show that the nuclear density does not leak out of the molecular cavity because it is much more localized than the electronic density. Finally, the polarization of quantized protons is analyzed in both continuum solvent and explicit solvent environments described by the polarizable MB-pol model, illustrating the impact of specific hydrogen-bonding interactions captured only by explicit solvation. These calculations highlight the relationship among solvation formalism, nuclear polarization, and energetics.

DFT Model of Elemental Sulfur in Sulfolane Solutions.

The structure and the thermodynamic and optical (UV) properties of elemental sulfur solution in sulfolane (Sl) have been studied using density functional theory methods. The cyclic molecular form of sulfur (S8 "crown") was found using PBE1PBE/6-311+G(d,p) approximation in combination with a polarizable continuum model (the integral equation formalism variant) to exist in sulfolane medium as a Sl-S8-Sl solvate. It has been theoretically established that sulfur can form stable (S8)n clusters in concentrated solutions. An increase in the extent of association (n) of the sulfur cluster leads to a decrease in the extinction coefficient [TD-DFT(TPSSTPSS/6-311+G(d,p))] of the most intense absorption maximum lying at about 50,000 cm-1 while maintaining the shape of the remaining part of the spectrum. The observed pattern qualitatively expresses the spectral regularities of solutions with different concentrations of sulfur in sulfolane. It has been proposed that a model of the absorption spectrum of elemental sulfur suggests a minor contribution of the S12 molecular form (G298°((S12)2) - G298°((S8)3) ≈ -15.5 kJ mol-1). The findings of the study will provide deeper insights into the transformation of molecular forms of sulfur and more precisely analyze processes involving sulfur as an acting species using electronic spectroscopy.

A Computational Study of the Electronic Energy and Charge Transfer Rates and Pathways in the Tetraphenyldibenzoperiflanthene/Fullerene Interfacial Dyad.

The electronic transition rates and pathways underlying interfacial charge separation in tetraphenyldibenzoperiflanthene:fullerene (DBP:C70) blends are investigated computationally. The analysis is based on a polarization-consistent framework employing screened range-separated hybrid functional in a polarizable continuum model to parametrize Fermi's golden rule rate theory. The model considers the possible transitions within the 25 lowest excited states of a DBP:C70 dyad that are accessible by photoexcitation. The different identified pathways contributing to charge carrier generation include electron and hole transfer and backtransfer, exciton transfer, and internal relaxation steps. The larger density of states of C70 appears to explain the previously observed larger efficiency for charge separation through hole transfer mechanism. We also analyze the validity of the high-temperature and short-time semiclassical approximations of the FGR theory, where both overestimated and underestimated Marcus theory based constants can be affected.

Potential energy surfaces of the [formula omitted] clusters in solution phase

In the present work, we have studied the effects of the implicit solvent on the structural and energetic parameters of Cu2+(MeOH)n=1-8 clusters. Initially, we explored the potential energy surfaces (PESs) obtained in the solution phase using the functional DFT M06-2X method, in conjunction with the 6–31++G** Pople basis set, and compared them with isomers of the same complexes optimized in the gaseous phase. The implicit solvent is described here by the polarized continuum model of integral equation formalism (IEF-PCM). Subsequently, we reported the temperature dependence and the binding electronic energies per methanol molecule. Our investigations reveal that the 6- and 5-coordinate isomers occupy the ground states on the PESs of the Cu2+(MeOH)n=1-8 clusters. The stability rules of the Cu2+ ion established in the gas phase are best adhered to in the implicit solvent. Regarding the temperature dependence of the solution phase conformer distribution, symmetric and compact structures, as well as those with a high coordination number (CN), dominate the population of the Cu2+(MeOH)n=1-8 clusters at all temperatures. Notably, the populations of clusters with sizes n=7-8 are exclusively dominated by hexa-coordinated structures at all temperatures, while penta- and tetra-coordinated isomers are disadvantaged. For the determination of the binding electronic energy, using a function fit, we computed these energies to be -1589kJ mol−1 in the implicit solvent and -7150kJ mol−1 in the gaseous phase. This significant difference is attributable to the interactions between the methanol molecules and the implicit solvent, which are present in the solvent phase but absent in a gaseous medium. This difference is further supported by the analysis of the Wiberg bond index of the metal–ligand interactions of the clusters in the two media.

Photophysical properties of four-membered BN3 heterocyclic compounds: theoretical insights.

Understanding the photochemistry of boron nitrogen (BN)-containing compounds is an important aspect to enhance the various optical and electronic applications. In this work, we have explored the structure, bonding, reactivity, electronic absorption (UV-Vis), and light harvesting efficiency (LHE) of a series of BN3 ring and open-chain systems. The frontier molecular orbitals (FMO) analysis found that ring systems have a low HOMO-LUMO energy gap as compared to the open-chain systems which insinuates the feasibility of ring systems in the optoelectronic materials. Also, the molecular electrostatic potential (MEP) maps have been computed to pursue the electrophilic and nucleophilic sites available at the surface of the compound. Interestingly, we have found that the open-chain compounds show more molecular charge distribution range rather than the ring compounds. The investigation of photophysical properties showed that the UV-Vis absorption significantly red-shifted in BN3 ring systems as compared to open-chain counterparts. Furthermore, light harvesting efficiency (LHE) was also found higher in the ring systems as compared to the BN3 open-chain systems. Moreover, the computed structural parameters are found well corroborated with the available X-ray data. Structures of all compounds were optimized by using density functional theory (DFT) method, with M06-2X/6-31G(d,p) level. All the calculations in this work are carried out in Gaussian 16 program package. GaussView6.1 software was used for the modeling of initial geometries and for the plotting of MEP plots. To account the solvent effect on geometries the polarized continuum model (PCM) was used and tetrahydrofuran (THF) taken as solvent. The NBO6.0 program (incorporated in G16 software) was used for the exploration of bonding nature and stabilization energies of B-N bond. The absorption spectra were simulated by using ORCA 4.2 program.