In this work, we investigated intermolecular interactions in benzoic acid and its ethanol solutions using Raman spectroscopy and quantum-chemical approaches. Analysis of the Raman spectra revealed that adding ethanol induces significant changes in benzoic acid's vibrational spectrum. These changes are primarily due to solvent effects and hydrogen-bond formation and are most pronounced in the vibrational modes corresponding to the carboxyl group. The near-invariance of the aromatic ring confirms the preservation of the structural integrity of the molecule. Theoretical calculations were performed at the DFT level, providing a thorough analysis of the system's electronic structure and energetic characteristics. The molecular electrostatic potential (MEP) surface was used to identify reactive sites within the molecule; the oxygen atoms of the carboxyl group emerged as the principal electron-rich nucleophilic centers, while the –OH group of ethanol played a significant role in hydrogen bond formation. HOMO–LUMO orbital analysis demonstrated a redistribution of electron density during complex formation and an increase in the reactivity of the system. Molecular docking results also confirmed benzoic acid's ability to interact with a biologically active binding site. During the calculations, the molecule adopted a stable conformation within the protein's active site, forming a complex through hydrogen bonds and other weak intermolecular interactions. These findings align with the MEP and electronic structure analyses, showing a close link between the molecule's quantum-chemical properties and its potential biological activity. The investigations reveal the mechanism of intermolecular interactions in the benzoic acid–ethanol system and provide a comprehensive explanation of how these interactions influence the molecule's vibrational properties, electronic structure, and behavior in a biological environment.

Using the B3LYP/6-31G(d,p) DFT method, the structural, electronic and vibrational properties of the b-5 lignin model compound and its sulfated derivatives were investigated. The introduction of sulfate groups was found to increase the electrophilicity and chemical softness of the molecules, shift the electron density toward the sulfate groups and create extensive negatively charged regions, thereby enhancing intermolecular interactions and improving solubility. These changes make sulfated lignin derivatives promising for applications in green chemistry, pharmaceuticals and functional biomaterials.

In this study, the C=O, C-H stretching, and ring breathing vibration bands of acetophenone in ethanol and chloroform solutions were assessed using Raman scattering spectroscopy. A blue shift and a red shift have been observed in the C-H and C=O stretching vibration bands respectively. To assess these modifications, computations using Density Functional Theory (DFT) were carried out. Consequently, a red shift was found to be caused by H-bonds passing via the C=O group in the given complexes. It was discovered that the C-H group mainly forms Van der Waals interactions or weak H-bonds, which cause blue shifts. The frontier molecular orbital (FMO) and molecular electrostatic potential (MEP) of the acetophenone monomer, dimer, and its interacting state with solvent (ethanol, chloroform) molecules are calculated by B3LYP/6-311G++(d, p) theoretical level. The Atoms in Molecules (AIM) study is performed for investigating the topological parameters, such as the density of electrons, the Laplacian of electron density, and the energy density. The vibrational assignment of the individual and interacting molecules is accomplished through the Potential Energy Distribution Analysis (PED). The theoretical and experimental values show good agreement with one another.

The intermolecular interactions between aniline (PhNH2) and ethyl acetate (EtOAc) were investigated by using Raman spectroscopy and density functional theory (DFT) calculations. Experimental Raman spectra revealed red and blue shifts in the vibrational bands of PhNH2, indicating the presence of weak hydrogen bonding and van der Waals interactions with EtOAc. A prominent hydrogen bonding was observed between the NH2 group of PhNH2 and the carbonyl (C=O) group of EtOAc. DFT calculations were performed to support the experimental findings, showing strong agreement. Molecular electrostatic potential (MEP) maps highlighted the electrophilic nature of the NH2 group and the nucleophilic character of the C=O group, corroborating the observed hydrogen bonding. Frontier molecular orbital (FMO) analysis revealed that the HOMO-LUMO energy gap of PhNH2(EtOAc)n (n = 1-3) complexes decreases with increasing number of EtOAc molecules, reaching a minimum of 4.69 eV. Quantum theory of atoms in molecules (QTAIM) analysis confirmed that the complexation is primarily governed by weak hydrogen bonding and van der Waals interactions involving N-HO=C, H-NH-C, and C-HO=C contacts. This study provides valuable insights into solvent effects on the molecular behavior of aniline, with implications for both fundamental research and practical applications in physics and chemistry.

This work presents a comprehensive study of the crystal structure, spectral properties (IR and UV-Vis), thermal behavior, and antimicrobial activity of homopiperazinium dichromate (C5H14N2)Cr2O7(VI). X-ray diffraction reveals that the compound crystallizes in the monoclinic space group P21/c, with unit cell dimensions a=8.7275(8)Å, b=10.5769(11)Å, and c=14.7467(10)Å and β=122.941(4)°. The crystal packing is stabilized by intermolecular N-H…O and C-H…O hydrogen bonds, with Hirshfeld surface analysis revealing dominant O…H/H…O interactions contributing 80.5% to the overall crystal cohesion. UV-Vis absorption bands are observed at 279, 354, and 446nm, with an estimated band gap energy of 3.019eV, indicating high stability and moderate optical activity. Thermal analysis shows an intense endothermic fusion peak followed by continuous decomposition, leading to chromium oxide formation. Antimicrobial tests demonstrate significant inhibition activity against tested pathogens, including notable antifungal effects against Candida albicans. These results highlight the potential of this hybrid material in antimicrobial development and photochemical applications.

In this paper, we investigated the non-coincidence effect (NCE), a spectroscopic manifestation of the intermolecular coupling in acetate esters. The isotropic and anisotropic Raman peak frequencies of the C = O stretching mode of ethyl, butyl, and amyl acetates have been discussed in the non-polar solvent carbon tetrachloride using different methods. It was predicted that dipolar forces play a dominant role in the pure state of the studied liquids, as a positive NCE occurred in their C = O stretching mode. The NCE of all selected liquids was determined for solvent and compared with the theoretical Onsager-Fröhlich dielectric continuum model. This theoretical model indicated that intermolecular processes in liquids depend on microscopic parameters such as molecular structure, intermolecular forces, and molecular orientation. Density functional theory calculations and the polarizable continuum model were used to investigate the vibration wavenumber of ethyl, butyl, and amyl acetate dimers at the B3LYP/6–311 + + G(d,p) levels based. Topological analyses, such as non-covalent interaction and reduced density gradient were used to better understand the nature and strength of intermolecular interactions in these dimers. The Mulliken charge distribution and molecular electrostatic potential surface analysis were performed to better understand charge transfer, displacements, and other molecular properties.

This paper investigates the vibrational properties and intermolecular interactions of formamide (FA) in polar solvents with varying dielectric constants and dipole moments, including dimethyl sulfoxide (DMSO), acetonitrile (AcN), and 1,4-dioxane (DiX). Raman non-coincidence effects (NCE) in the C--O stretching and NH2 bending modes were observed to decrease monotonically in all solvents, indicating a systematic solute-solvent interaction trend. To explain such trends, experimental results were compared with the Onsager-Frohlich dielectric continuum model, revealing strong agreement in solvents with high dielectric constants and dipole moments. Complementary DFT analyses of the Raman spectra for various FA self-associations identified a closer match with experimental results in odd-numbered molecular associations. The nature and strength of intermolecular forces in FA-solvent complexes were further investigated by topological methods (AIM, NCI, RDG), which confirmed findings from experiments. These findings advance our understanding of solute-solvent dynamics polar environments and have broad implications for studies of intermolecular forces in chemical and biological systems.

The intermolecular interactions of ethyl acetate (EtOAc)-water (H2O)/ethanol (EtOH) mixtures were investigated using a combination of Raman spectroscopy and quantum chemical calculations. The computational approach was used to analyze the structure of hydrogen-bonded complexes of ethyl acetate with water/ethanol molecules, based on density functional theory (DFT). The calculated frequencies closely matched the experimental Raman values, with differences being under 4

Raman and FTIR spectra of pure ethanol and its proton-donor and proton-acceptor solvents were studied using experiments and ab-initio (DFT) calculations. Spectral bands related to C-H and O-H stretching vibrations of pure ethanol are complex and consist of at least two bands, and these bands belong to different aggregates of ethanol. According to experiments and ab-initio calculations, when ethanol is dissolved in water, the Raman and FTIR spectra related to C-H and O-H stretching vibration shifted towards higher frequency as the concentration of ethanol decreased. This is due to hydrogen bonds in the form of C-H···O (non-classical) and O-H···O. Such shifts take place due to weak interactions between the methyl group in ethanol and water.

This work is focused on biologically active neat amyl acetate and its solutions in ethanol/heptane. According to the experimental results, when the concentration of amyl acetate in the amyl acetate-ethanol solution decreases, the additional band appears on the low-frequency side. The primary reason for the formation of such additional band is the intermolecular hydrogen bonding between amyl acetate and ethanol. In the amyl acetate-heptane solution, as the concentration of amyl acetate in the solution decreases, the band corresponding to the C=O stretching vibrations shifted to a higher frequency. This is explained by the fact that heptane breaks intermolecular interactions in solution, resulting in a simpler spectral band corresponding to the C=O stretching vibrations. Calculations are also used to study interactions in amyl acetateethanol complexes and their spectral manifestations. When the complex formation energies are calculated, this energy increases with the number of molecules, but the average hydrogen bond energy per one bond remains unchanged. The density functional theory (DFT) method is used to analyze molecular structural parameters: Mulliken atomic charge distribution; thermodynamic parameters; molecular electrostatic potential (MEP) surface; atoms in molecules (AIM) analysis; quantum chemical parameters such as reduced density gradient (RDG) and noncovalent interaction (NCI) analysis; electron localization functions (ELF) analysis; and localized orbital locator (LOL) analysis.

The realization of efficient large-area perovskite solar cells stands as a pivotal milestone for propelling their future commercial viability. However, the upscaling fabrication of perovskite solar cells is hampered by efficiency losses, and the underlying growth mechanism remains enigmatic. Here, it is unveiled that a prevalent upscaling technology, namely blade-coating, inherently triggers top-down inhomogeneity strains, predominantly concentrated on the surface of wide-bandgap perovskite films. Through strain mitigation strategies, the perovskite films exhibit reduced halide vacancies, leading to enhanced stability and improved optoelectronic characteristics. Consequently, the blade-coated perovskite solar cells achieve minimal efficiency loss when transitioning from small-area to large-area devices, enabling the realization of 1 cm2-area 1.77 eV-bandgap cells with a remarkable efficiency of 18.71%. Additionally, the strain-relieved device exhibits an exceptional 109% retention of its initial efficiency even after 400 h of continuous operation, in stark contrast to the control device which experiences a decline to 91%. Furthermore, the resulting 4-terminal all-perovskite tandem solar cells crafted utilizing blade-coated 1.77 eV-bandgap subcells achieve a maximum efficiency of 27.64% (stabilized at 27.28%). This study not only sheds light on the intricacies of upscaling preparation techniques but also overcomes potential obstacles that can impede the trajectory toward achieving large-scale perovskite solar cells. Blade-coated wide-bandgap perovskites encounter top-down inhomogeneity strains. Utilizing mixed-cation post-treatment for strain relief, large-area wide-bandgap solar cells demonstrate enhanced efficiency and stability. Specifically, 1 cm2-area 1.77 eV-bandgap cells achieve an 18.71% efficiency (stabilized at 18.50%), while 4-terminal all-perovskite tandems reach an exceptional 27.64% efficiency, coupled with enhanced stability.image

In this study, the optimal geometry and vibrational assignments of 2-methyl-4-hydro-1,3,4-triazol-thione-5, one of the triazole derivatives, were analysed by the DFT approach and vibrational spectroscopy. PED values were calculated, and vibrational assignments were determined. Experimental results showed that interactions between 2-methyl-4-hydro-1,3,4-triazol-thione-5 and solvent (acetone, acetonitrile, dioxane, and DMF) molecules lead to a red shift of the N-H stretching vibrational band. The computations were performed at the B3LYP/6-311++G(d,p) functional set. The molecular electrostatic potential surface was used to distinguish between electrophilic and nucleophilic regions. The reactivity of the molecular complexes was determined by examining their frontier molecular orbitals. Topological investigations revealed the existence of N-H…N and N-H…O-type hydrogen bonds between 2-methyl-4-hydro-1,3,4-triazole-thiol-5 and solvent molecules. The red-shift of the N-H stretching band and H-bond strength between solute–solvent molecules are in the order of acetonitrile, acetone, dioxane, and DMF.

In this work, on the example of butyl acetate, the nature of intermolecular interactions was studied using vibrational spectroscopy (Raman and FTIR) and non-empirical calculations. The geometric structures of the most stable dimer and trimer aggregates of butyl acetate were optimized using the Density Functional Theory (DFT) method based on the B3LYP/6-311++G(d,p) basis set. Molecular aggregations in liquid butyl acetate were shown to be formed by dipole-dipole interactions and weak C-H…O hydrogen bonds. A potential energy distribution (PED) analysis was performed for the butyl acetate molecule, and experimental and calculated frequencies were found to be in good agreement. Frontier molecular orbitals such as the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the butyl acetate molecule were analyzed.

The self-association of 1,2,4-triazole was studied by the DFT method at the B3LYP/6-311++G(d,p) level in the gas phase, and the most stable dimer and trimer were presented. Based on the integral equation formalism polarizable continuum model (IEFPCM), the effect of solvents such as water and dimethyl sulfoxide (DMSO) on the geometric parameters of molecular complexes (dimer and trimer), atomic charge distribution, molecular electrostatic potential (MEP) surface, and frontier molecular orbitals (FMO) was analyzed. Intermolecular in-teractions in cyclic and linear complexes were studied using topological analyses (QTAIM, NCI, RDG, ELF, and LOL). IR spectra of 1,2,4-triazole monomer, dimer, and trimer were simulated and compared with experimental results. In self-association, intermolecular hydrogen bonding causes a red shift of the N-H stretching vibrational frequency of 1,2,4-triazole. The solvent effect on the vibrational bands of monomer, dimer, and trimer was analysed.

This study describes the effect of ethanol on the vibrational modes of ortho-aminobenzoic acid (OABA) using Raman and FTIR spectroscopy. The intermolecular interactions between OABA and ethanol mole-cules were analysed using DFT, IEFPCM, and M062X methods based on the B3LYP/6-311++G(d,p) basis set. The effect of the solvent at different concentrations on the C = O stretching vibration of OABA was studied. The most stable complex formed by OABA and the ethanol molecules was determined. OABA, ethanol, and OABA + ethanol complexes' Raman and IR spectra were simulated. The scaled theoretical and experimental results show good agreement with each other. Mulliken atomic charge distribution and NBO analysis were used to study the mechanism of intermolecular and intramolecular charge trans-fer. MEP, HUMO-LUMO gap, and other electronic properties are reported. Interactions at the critical points of connections were studied using topological (AIM, NCI, RDG, ELF, and LOL) analyses. The inter-action of OABA with ethanol molecules was determined by the carboxyl group of OABA and the hydroxyl group of ethanol.(c) 2023 Elsevier B.V. All rights reserved.

The mechanism of molecular complex formation in liquid propionic acid and its solutions is investigated. The anisotropic component of the Raman band of the C=O stretching vibration of pure propionic acid consists of three bands with maxima at 1661, 1700, and 1753 cm−1. The effect of varying the concentrations of solvents such as CCl4, acetonitrile, and water on this vibration mode is studied. The mechanism of formation of molecular complexes in solutions is determined using DFT calculations at the B3LYP/6-311++G(d,p) level of theory. The AIM, RDG, and NCI topological analyses are also performed to investigate the intermolecular interactions in the complexes.

In this work, the mechanisms of molecular clusters formation in liquid trifluoroacetic acid were studied using Raman scattering spectra in different solutions. The polarized components of Raman scattering spectra corresponding of the C=O, O–H stretching bands of pure trifluoroacetic acid consist of three broad bands at 1734, 1754, and 1800 cm−1 with different depolarization ratios. When the acid is strongly dissolved in acetonitrile, the 1800 cm−1 spectral band belonging to the C=O band remains. The intermolecular interactions in the formation of trifluoroacetic acid monomer, dimer, and trimer, as well as clusters with water [CF3COOH + (H2O)n, n = 1–7] and acetonitrile [CF3COOH + (CH3CN)n, n = 1–2] molecules, were analysed using the density functional theory (DFT) method.

The intermolecular interaction in dimethyl sulfoxide (DMSO), which is a strong solvent, and its manifestation in vibrational spectra are studied by means of Raman spectroscopy and ab initio calculations. The optimal structure and vibrational spectra of DMSO monomer, dimer, and trimer, as well as complexes of DMSO with water molecules, are calculated, and the potential energy distribution (PED) analysis is carried out. In the Raman spectra of DMSO and its water solutions, a red shift of the S=O stretching band due to the conventional hydrogen bonding and a blue shift of the C–H stretching band due to non-classical hydrogen bonding are detected. The MEP surfaces (changes in the charge distribution) of DMSO monomer, dimer, and DMSO–water cluster are plotted.

In this work, the mechanisms of molecular clusters formation in liquid trifluoroacetic acid were studied using Raman scattering spectra in different solutions. The polarized components of Ra-man scattering spectra corresponding of the C=O, O-H stretching bands of pure trifluoroacetic acid consist of three broad bands at 1734, 1754, and 1800 cm-1 with different depolarization ra-tios. When the acid is strongly dissolved in acetonitrile, the 1800 cm-1 spectral band belonging to the C=O band remains. The intermolecular interactions in the formation of trifluoroacetic acid monomer, dimer, and trimer, as well as clusters with water /CF3COOH+ (H2O)n, n = 1- 7] and acetonitrile /CF3COOH+ (CH3CN)n, n = 1-2] molecules, were analysed using the density functional theory (DFT) method.

Nitromethane molecules have a large dipole moment (3.54 D), so there is a possibility of dipole-dipole aggregation for them. Ab initio calculations show an additional possibility of molecular interaction for the nitromethane molecules-hydrogen bonding. In particular, the formation of H-bond is observed in the case of nitromethane dimers. The hydrogen bonds of the NO horizontal ellipsis HC type are formed between an oxygen atom of a nitromethane group of one molecule and a hydrogen atom of the C-H group of the adjacent one. These interactions have a significant effect on the formation of molecular clusters of nitromethane.