Vibrational Spectra Research Articles

Synthesis, structural study, antimicrobial activity and theoretical treatment of Cr(III), Ni(II), Pt(IV) and Zn(II) complexes with 2-hydroxy-4-Nitro phenyl piperonalidene

The complexes of the 2-hydroxy-4-Nitro phenyl piperonalidene with metal ions Cr(III), Ni(II), Pt(IV) and Zn(II) were prepared in ethanolic solution. These complexes were characterized by spectroscopic methods, conductivity, metal analyses and magnetic moment measurements. The nature of the complexes formed in ethanolic solution was study following the molar ratio method. From the spectral studies, monomer structures proposed for the nickel (II) and Zinc (II) complexes while dimeric structures for the chromium (III) and platinum (IV) were proposed. Octahedral geometry was suggested for all prepared complexes except zinc (II) has tetrahedral geometry, Structural geometries of these compounds were also suggested in gas phase by using hyper chem-8 program for the molecular mechanics and semi-empirical calculations. The heat of formation and binding energy for the prepared compounds was calculated by using PM3 and AMBER methods. The method of PM3 was used for evaluate the vibration spectra for the imine and starting material as authentic compound. Preliminary in vitro tests for antibacterial and antifungal activity show that most of the prepared compounds display good activity to (Staphylococcus aureus), (Escherichia coli) and (Candida albicans).

Novel Vibrational Proteins.

Genetically encoded green fluorescent protein (GFP) and its brighter and redder variants have tremendously revolutionized modern molecular biology and life science by enabling direct visualization of gene regulated protein functions on microscopic and nanoscopic scales. However, the current fluorescent proteins (FPs) only emit a few colors with an emission width of about 30-50 nm. Here, we engineer novel vibrational proteins (VPs) that undergo much finer vibrational transitions and emit rather narrow vibrational spectra (0.1-0.3 nm, roughly 3-10 cm-1). In response to an amber stop codon (UAG), a terminal alkyne bearing an unnatural amino acid (UAA, pEtF) is directly incorporated in place of Tyr64 in the chromophore of pr-Kaede by genetic code expansion. Essentially, the UAA64 further conjugates into a large π system with the contiguous two editable amino acid residues (His63 and Gly65), resulting in a programmable Raman resonance shift of the embedded alkyne. In the proof-of-concept experiment, we constructed a series of novel pEtF-VP mutants and observed fine Raman shifts of the alkynyl group in different chromophores. The genetically encoded novel VPs, could potentially label tens of proteins in the future.

Exploring the activation potential of heme for 2,4-dichlorophenol, 2,4,6-trichlorophenol, and pentachlorophenol

The presence of chlorophenols in water poses a significant threat to human health and the environment. In response to this issue, a study was undertaken to evaluate the catalytic capabilities of chlorinated Heme towards common chlorophenols present in water, such as 2,4-dichlorophenol, 2,4,6-trichlorophenol, and pentachlorophenol. The study employed the B3LYP method, a sophisticated computational technique within density functional theory, to investigate the molecular interactions and transformations involved. It scrutinized structural parameters, Wiberg Bond Indices, which offer insights into the strength and nature of chemical bonds, along with spectroscopic data including infrared vibrational spectra, ultraviolet-visible absorption spectra, and molecular fluorescence spectra. Furthermore, the research analyzed molecular binding energies and orbital energy levels before and after the formation of complexes between Heme and the targeted chlorophenols. The findings indicate that Heme displays a notable activation characteristic towards these chlorophenols. This suggests that Heme could act as an effective catalyst in the degradation of chlorophenols in water, presenting a novel approach to water purification. The theoretical insights derived from this study are invaluable, potentially guiding the development of more efficient catalytic systems for treating chlorophenol-contaminated water, thereby reducing the environmental and health risks associated with these hazardous compounds.

Structure and Dynamics of ATP and the ATP-Zn2+ Complex in Solution.

Despite the crucial role of ATP in life and artificial life-like applications, fundamental aspects relevant to its function, such as its conformational properties and its interaction with water and ions, remain unclear. Here, by integrating linear and two-dimensional infrared spectroscopy with ab initio molecular dynamics, we provide a detailed characterization of the vibrational spectra of the phosphate groups in ATP and in its complex with Zn2+ in water. Our study highlights the role of conformational disorder and solvation dynamics, beyond the harmonic normal-mode analysis, and reveals a complex scenario in which electronic and environmental effects tune the coupling between phosphate vibrations. We identify βγ-bidentate and αβγ-tridentate modes as the preferential coordination modes of Zn2+, as was proposed in the literature for Mg2+, although this conclusion is reached by a different spectral interpretation.

Theoretical computation of thermodynamic functions of sodium dimer with modified shifted Morse potential

In this article, the asymptotic iteration method and the Laguerre polynomials are employed to obtain the eigensolutions of the Schrödinger equation with modified shifted Morse potential model. Vibrational energy results for sodium dimer have been presented numerically and these results are compared with experimental data from available literatures. With the help of the energy expression, the partition function and other thermodynamic function expressions of this potential model for sodium dimer are obtained, using the Euler MacLaurin’s formula. For various vibrational quantum numbers considered, the thermodynamic functions show high level of dependence on the temperature parameter. These results are justified by the numerical results presented for the thermodynamic functions of sodium dimer. Our results also agree with the available results in literatures and can also serve as a guiding reference in further studies concerning chemical physics and spectroscopy.

New Co(II) complexes of 5-nitroorotate with imidazole or N-methylimidazole co-ligands: Crystal and molecular structures, vibrational spectra and antimicrobial activities

Two novel Co(II) complexes of 5-nitroorotate with imidazole (ImH), [Co(5-NO2HOr)(H2O)2(ImH)2] (1) and N-methylimidazole (N-MeIm), [Co(5-NO2HOr)(H2O)2(N-MeIm)2] (2) have been synthesized and characterized by single crystal X-ray diffraction, PXRD, FT-IR and Raman spectroscopy, as well as elemental and thermal analyses. Both complexes crystallize in the monoclinic system (space group P21/c). The cobalt(II) ion is chelated by the 5-nitroorotate dianion through the carboxylate oxygen (O1) and the deprotonated pyrimidine nitrogen (N1) atoms. Two monodentate co-ligands, (ImH) in (1) or (N-MeIm) in (2), and two water molecules in cis conformation complete a distorted octahedral coordination sphere. Strong intermolecular OH···O and NH···O hydrogen bonds as well as weak NO···π and CH···π interactions, promote the crystal cohesion. The Hirshfeld surface analysis has been performed. Detailed assignment of the characteristic bands in the IR and Raman spectra, along with the thermogravimetric studies, have provided further evidence for the nature of bonding in these compounds. Additionally, both complexes have been investigated in vitro for their activity against selected bacteria: Gram-negative (E. coli ATCC 11229, P. aeruginosa ATCC 27853), Gram-positive (S. aureus ATCC 6538), and yeast (C. albicans ATCC 10231) under aerobic conditions. Moreover, their activity against bacteria that can constitute pathogens (E. coli ATCC 11229) or the probiotic strain (L. rhamnosus GG) has been tested under anaerobic conditions.

Exploration of crystal structure, supramolecular organization, and computational studies of a novel pyrazole derivative: A structural and theoretical perspectives

An eminent challenge in contemporary medicine and pharmacy is the identification of powerful, biologically active, and benign anti-COVID drugs. The objective of this work is to synthesize 3-chloro-1-(3-chloropyridin-2-yl)-1H-pyrazole-5-carboxylic acid to investigate its properties using different spectroscopic methods. The crystal structure of the compound is determined using single-crystal X-ray diffraction methodology. Hirshfeld surface analysis was employed to evaluate the impact of intermolecular interactions on crystal packing. The interactions were visually depicted using 2D fingerprint plots, which highlighted the specific surface area associated with each interactant. Indications suggest that the crystal packing is mostly governed by C-H...O and N-H...O interactions, resulting in the formation of S(7) self-motif and R44(24) synthon, which greatly improve crystal stability. Density functional theory (DFT) was employed to better examine the structural and electrical characteristics. Computations were conducted at the 6–311+G(d,p) level to determine the optimal geometry, total energy, HOMO-LUMO gap, and vibrational spectra. The results showed a HOMO-LUMO gap of 3.092 eV, suggesting a moderate amount of stability. Bader et al. employed reduced density gradient (RDG) techniques and topological analysis, taking into account the quantum theory of atoms in molecules (QTAIM), to examine noncovalent interactions. Additionally, the molecule satisfies Lipinski's rule of five and exhibits encouraging pharmacokinetic activities. Additional in-silico investigations, including molecular docking, were conducted on the SARS-CoV-2 spike protein variation to assist in the advancement of enhanced vaccines and therapeutics.

Low-temperature sintered Li2BaP2O7 ceramic: structural insights, bond characteristics, and microwave dielectric properties

The Li2BaP2O7 ceramics, synthesized through the solid-state reaction method, exhibit a pure monoclinic phase. Upon sintering at 750 °C, the ceramic achieves a high relative density of 97.3%, which is indicative of an optimal microstructure conducive to the superior microwave dielectric properties: a εr of 9.9, a Q × f of 86200 GHz, and a τf of -95.4 ppm/°C. The variation in relative density is identified as the principal driver of changes in both the εr and Q × f values for the Li2BaP2O7 ceramics. The molecular polarizability is pivotal in determining the εr of Li2BaP2O7 ceramics. The P-V-L theory analysis elucidates that the P-O bond significantly surpasses other chemical bonds in contributing to the ionicity, lattice energy, and bond energy, thereby underscoring its dominance over the three principal microwave dielectric characteristics. Furthermore, Raman spectroscopy data demonstrate that the P-O bond vibration predominantly governs the overall vibrational spectrum.

Solvation and its influence on the electronic structure and pharmacological activity of 2-fluoro-6-trifluromethyl acetophenone

The molecular framework and vibrational spectra of 2′-Fluoro-6′-Trifluoromethyl Acetophenone (MA3) in diverse solvent environments are being studied using quantum chemistry methods like DFT. The structure was successfully optimized using gas phase and solvent phases such as ethanol, diethyl sulfoxide, chloroform, and diethyl ether. Using FT-Raman and FT-IR techniques, both theoretical and experimental scenarios were examined. The IEFPCM model was used to explore the electronic properties, including HOMO-LUMO gaps, UV–Vis spectra, NBO, Mulliken analysis, and MEP, in various solvents. The TD-DFT approach and IEFPCM model were utilized to replicate the UV spectra. The Fukui function helped locate reactive sites and understand chemical interactions. Comprehensive topological analysis using Multiwfn – 3.8 suite integrated RDG, ALIE, ELF, and LOL to identify key binding sites and weak interactions. The molecular docking studies highlighted the compound’s binding affinities with target proteins, showcasing its potential pharmacological applications. This research underscores the critical role of solvation in determining the electronic and structural properties of MA3, paving the way for its application in drug development and other fields.

Mechanism of tetracycline sorption on carbon-bentonite

Antibiotics increased industrial production is the reason of their occurrence in wastewater, soils, groundwater, and drinking water. In this regard, treating the environment for pharmaceuticals is one of the urgent environmental challenges. Synthesis of adsorbents using different types of raw materials by the methods of mechanochemical activation makes it possible to significantly increase their sorption capacity due to the accumulation of various kinds of defects in the crystal structure of the adsorbent. We obtained the bentonite-carbon composite using roller-ring vibratory mill with coal-bentonite ratio of 30 : 70 and 50 : 50. However, the nature of the interaction between carbon and bentonite correlates with changes of surface area and porosity. The porous structure parameters of the samples show the mechanochemical activation of the mixture involves their components interactions. The authors studied the structural and chemical changes during the modification of bentonite with activated carbon by analysing the vibrational spectra of carbon, initial, and modified aluminosilicate samples. According to infrared spectroscopy of adsorbents, absorption bands characteristic of Si-O-C bond vibrations occurred. The paper investigates the sorption capacity of mechanochemically modified natural clay mineral Dash-Salakhli bentonite towards tetracycline hydrochloride. Research investigates the kinetics of the process and rapid sorption of tetracycline. The paper provides possible mechanisms of chemisorption due to donor-acceptor interaction and ion-exchange processes.

Physico-mechanical characterization and DFT studies of benzoyl peroxide treated water hyacinth reinforced polypropylene composites

The use of eco-friendly natural fiber-reinforced polymer composites is rapidly expanding across diverse sectors. The rapid spread of water hyacinth disrupts aquatic ecosystems by modifying the pH of water and salinity in Bangladesh. This work investigated on the impact of incorporating both untreated and chemically treated water hyacinth fibers into polypropylene (PP). Untreated water hyacinth (UWH) powder was treated with an alkaline solution, producing mercerized water hyacinth (MWH). MWH was further oxidized to yield oxidized water hyacinth (OWH). Analysis of attenuated total reflection-fourier transform infrared (ATR-FTIR) spectra of UWH, MWH and OWH confirmed cellulose modification. The UWH and OWH were taken in varying contents (1, 2.5, 5, 7.5, and 10 wt%) and added to PP to make UWH-PP and OWH-PP composites using compression molding technique. The 1% fiber content OWH-PP composites exhibited enhanced tensile strength, elongation, and impact strength compared to UWH-PP composites. Enhanced mechanical properties in OWH-PP composites suggested that benzoyl peroxide treatment improves interfacial adhesion. Morphological analysis of the OWH-PP composite showed better interfacial bonding between water hyacinth and PP than that of the UWH-PP composite. Thermogravimetric analysis (TGA) depicted the thermal stability of the UWH-PP and OWH-PP composites. The chemical reaction of cellulose monomer was further studied with DFT/B3LYP level of theory using two different basis sets 6-31+G(d, p) and cc-pVTZ. The calculated vibrational spectra of the untreated, mercerized and oxidized cellulose monomer agree well with the ATR-FTIR spectra, confirming chemical modification. DFT calculations of thermodynamic properties revealed the feasibility of the reactions. Electronic property (NBO charge) indicated charge transfer and structural changes during chemical modification.

Where Have All the Sulfur Atoms Gone? Polycyclic Aromatic Hydrocarbon as a Possible Sink for the Missing Sulfur in the Interstellar Medium. I. The C–S Band Strengths

Despite its biogenic and astrochemical importance, sulfur (S), the 10th most abundant element in the interstellar medium (ISM) with a total abundance of S/H ≈ 2.2 × 10−5, largely remains undetected in molecular clouds. Even in the diffuse ISM where S was previously often believed to be fully in the gas phase, in recent years, observational evidence has suggested that S may also be appreciably depleted from the gas. What might be the dominant S reservoir in the ISM remains unknown. Solid sulfides like MgS, FeS, and SiS2 are excluded as major S reservoirs due to the nondetection of their expected infrared spectral bands in the ISM. In this work, we explore the potential role of sulfurated polycyclic aromatic hydrocarbon (PAH) molecules—PAHs with sulfur heterocycles (PASHs)—as a sink for the missing S. Utilizing density function theory, we compute the vibrational spectra of 18 representative PASH molecules. It is found that these molecules exhibit a prominent C–S stretching band at ∼10 μm and two relatively weak C–S deformation bands at 15 and 25 μm that are not mixed with the nominal PAH bands at 6.2, 7.7, 8.6, 11.3, and 12.7 μm. If several parts per million of S (relative to H) are locked up in PAHs, the 10 μm C–S band would be detectable by Spitzer and the James Webb Space Telescope (JWST). To quantitatively explore the amount of S/H depleted in PASHs, a detailed comparison of the infrared emission spectra of PASHs with the Spitzer and JWST observations is needed.

Chromophore Structural Change during the Photocycle of a Light-Driven Cl- Pump from Mastigocladopsis repens: A Cryogenic Raman Study.

Microbial rhodopsins are the most widely distributed photoreceptors that bind a retinal Schiff base chromophore. Among them, a light-driven Cl- pump discovered from Mastigocladopsis repens (MrHR) is distinctive in that it has the structural features of both H+ and Cl- pumps. While the photocycle has been characterized by light-induced changes of the absorption spectrum, the structural changes of the retinal chromophore remain largely unknown. In this study, we examined the chromophore structural changes of MrHR by using cryogenic Raman spectroscopy. We observed five photointermediates─K, L, N1, N2, and MrHR'─that show distinct vibrational spectra, indicating atypical chromophore structures, e.g., small distortion in the K intermediate and Schiff base configurational change in the MrHR' intermediate. Based on the Raman spectra of two N intermediates (N1 and N2), we propose that N1 is the Cl--bound state and N2 is the Cl--unbound state, which are responsible for the Cl- release and uptake, respectively, to achieve Cl- pumping.

Quantifying mass-dependent isotope fractionation and nuclear field shift effects for the light rare Earth elements in hydrous systems

The improving sensitivity of mass-spectrometers has opened the potential of using stable isotope signatures of the rare Earth elements (REE) as geochemical tracers. However, thus far only limited studies have utilised REE stable isotopes, despite resolvable variations having been observed in a range of systems. An interesting but poorly explored area remains variations in aqueous environments across a range of temperatures including seawater, marine sediments, ion adsorption deposits or hydrothermal systems. Furthermore, the magnitudes and competing effects of mass-dependent isotope fractionation and mass-independent nuclear field shift effects, which can be significant factor for heavy elements especially at high temperatures, remain poorly understood.To contribute to a holistic understanding of REE isotope signatures, we calculated reduced partition function ratios (as 103lnβ) for mass-dependent and nuclear field shift effects for aqueous La, Ce, and Nd complexes from first principles. Theoretical calculations were compared with experimental data, and this demonstrates that calculations involving a combination of two explicit hydration shells and additional implicit solvation effects are required to accurately describe the coordination and molecular vibrations of aqueous complexes. This data was then combined with speciation modelling of seawater and hydrothermal fluids to assess isotope fractionation in hydrous systems. The predicted magnitude of isotope fractionation is significant in low (T = 25 °C) temperature systems (Δ139/138LaMax-Min = 0.20 ‰, Δ142/140CeMax-Min = 0.33 ‰, Δ146/144NdMax-Min = 0.34 ‰) and remains above currently achievable analytical uncertainties even at high (T = 500 °C) temperatures (±0.015 ‰ for δ146/144Nd; ±0.040 ‰ for δ142/140Ce). Unless oxidation occurs, which is only relevant for Ce in terrestrial environments, nuclear field shift effects are negligible even at temperatures up to 500 °C. The large difference in nuclear charge radius between 140Ce and 142Ce strongly enriches the lighter Ce isotope in the higher oxidation state (103lnβCe(IV)-Ce(III) = −0.45 at 25 °C) which almost completely cancels out the opposing mass-dependent effect (103lnβCe(IV)-Ce(III) = +0.46 at 25 °C). This means that variations in δ142/140Ce isotope signatures cannot easily be related to oxidation in ancient or recent environments.

Vibrational Fermi Resonance in Atomically Thin Black Phosphorus.

Fermi resonance is a phenomenon involving the hybridization of two coincidentally quasi-degenerate states that is observed in the vibrational or electronic spectra of molecules. Despite numerous examples in molecular systems, vibrational Fermi resonances in dispersive semiconducting systems remain largely unexplored due to the rarity of occurrence. Here we report a vibrational Fermi resonance in atomically thin black phosphorus. The Fermi resonance arises via anharmonic mixing of a fundamental Raman mode and a Davydov component of an infrared mode, leading to a doublet with mixed character. The extent of Fermi coupling can be modulated by the application of external biaxial strain. The consequences of Fermi hybridization are revealed by electronic resonance effects in the thickness-dependent and excitation-wavelength-dependent Raman spectrum, which is predicted by ab initio hybrid functional simulations including excitonic interactions. This work reveals new insight into electron-phonon coupling in black phosphorus and demonstrates a novel method for modulating Fermi resonances in 2D semiconductors.

Intermolecular Bending States and Tunneling Splittings of Water Trimer from Rigorous 9D Quantum Calculations: I. Methodology, Energy Levels, and Low-Frequency Spectrum.

We present the computational methodology that enables the first rigorous nine-dimensional (9D) quantum calculations of the intermolecular bending states of the water trimer, as well as its low-frequency spectrum for direct comparison with experiment. The water monomers, treated as rigid, have their centers of mass (cm's) at the corners of an equilateral triangle, and the intermonomer cm-to-cm distance is set to a value slightly larger than that in the equilibrium geometry of the trimer. The remaining nine strongly coupled large-amplitude bending (angular) degrees of freedom (DOFs) enter the 9D bend Hamiltonian of the three coupled 3D rigid-water hindered rotors. Its 9D eigenstates encompass excited librational vibrations of the trimer, as well as their torsional and bifurcation tunneling splittings, which have been the subject of much interest. The calculations of these eigenstates are extremely demanding, and a sophisticated computational scheme is developed that exploits the molecular symmetry group of the water trimer, G48, in order to make them feasible in a reasonable amount of time. The spectrum of the low-frequency vibrations of the water trimer simulated using the eigenstates of the 9D bend Hamiltonian agrees remarkably well with the experimentally observed far-infrared (FIR) spectrum of the trimer in helium nanodroplets over the entire frequency range of the measurements from 70 to 620 cm-1. This shows that most peaks in the experimental FIR spectrum are associated with the intermolecular bending vibrations of the trimer. Moreover, the ground-state torsional tunneling splittings from the present 9D calculations are in excellent agreement with the spectroscopic data. These results demonstrate the high quality of the ab initio 2 + 3-body PES employed for the DOFs included in the bound-state calculations.

Fe-MOF derived Fe3O4/C-based hydrogel for efficient solar-driven photothermal evaporation

Solar-driven interfacial photothermal evaporation (SIPE) has been considered as a green and sustainable technology for obtaining fresh water, and the exploring efficient photothermal materials is crucial. Nanocomposite derived from metal-organic framework exhibits high light absorption properties and excellent chemical stability, making it an ideal candidate in the SIPE. Herein, Fe3O4/C nanocomposite was obtained using MIL-101 (Fe) as a precursor, and Fe3O4/C-based porous hydrogel (Fe3O4/C-PH) was subsequently prepared through chemical crosslinking foaming polymerization. The obtained Fe3O4/C-PH exhibited an evaporation rate of 3.33 kg m−2 h−1 under one sun intensity. Fe3O4/C-PH demonstrated outstanding desalination and salting out resistance when treating real seawater. Moreover, it could remove over 99 % of dyes from wastewater. The photothermal mechanisms are molecular thermal vibration of C component and semiconductor relaxation of Fe3O4. Meanwhile, the hydrophilic and porous skeleton structure of the hydrogel ensure Fe3O4/C-PH to transport water rapidly and exhibit good light absorption properties. This research broadens the candidate of photothermal materials for applications in SIPE, and also provides new avenues for desalination and wastewater purification.

Tracing the Background‐Suppressed Vibrational Decay Time of a Molecular Monolayer with Time‐Resolved Surface‐Enhanced Broadband Coherent Anti‐Stokes Raman Scattering

AbstractThe sensitivity of molecular spectroscopy based on surface‐enhanced coherent anti‐Stokes Raman scattering (SECARS) is limited by the spectrally overlapping background from nonresonant four‐wave mixing (FWM). While the SECARS signal is mediated by the molecular vibrational eigenstates and exhibits long lifetime (a few picoseconds), the FWM background stems from the instantaneous electronic polarization and decays rapidly with the vanishment of excitation. Therefore, CARS and FWM can be separated by time‐resolved CARS (trCARS) using ultrashort pulsed lasers. The broad spectral bandwidth also enables broadband CARS (BCARS) for simultaneous identification of multiple vibrational signatures. This work combines trCARS and BCARS with an optimized plasmonic system to demonstrate time‐resolved surface‐enhanced BCARS) and show its capability in obtaining background‐suppressed broadband vibrational spectra from a monolayer of 4‐Aminothiophenol (4‐ATP) molecules self‐assembled on a gold grating. The vibrational dephasing time of the ring‐breathing mode for the 4‐ATP monolayer on the gold grating (≈1.00 ± 0.17 ps) is significantly shortened compared to that for 4‐ATP powder on a glass substrate (2.10 ± 0.05 ps). This work presents an effective method to suppress FWM background and investigate the vibrational dynamics of molecules in the vicinity of plasmonic nanostructures.

Revealing the molecular structures of α-Al2O3(0001)-water interface by machine learning based computational vibrational spectroscopy.

Solid-water interfaces are crucial to many physical and chemical processes and are extensively studied using surface-specific sum-frequency generation (SFG) spectroscopy. To establish clear correlations between specific spectral signatures and distinct interfacial water structures, theoretical calculations using molecular dynamics (MD) simulations are required. These MD simulations typically need relatively long trajectories (a few nanoseconds) to achieve reliable SFG response function calculations via the dipole moment-polarizability time correlation function. However, the requirement for long trajectories limits the use of computationally expensive techniques, such as abinitio MD (AIMD) simulations, particularly for complex solid-water interfaces. In this work, we present a pathway for calculating vibrational spectra (IR, Raman, and SFG) of solid-water interfaces using machine learning (ML)-accelerated methods. We employ both the dipole moment-polarizability correlation function and the surface-specific velocity-velocity correlation function approaches to calculate SFG spectra. Our results demonstrate the successful acceleration of AIMD simulations and the calculation of SFG spectra using ML methods. This advancement provides an opportunity to calculate SFG spectra for complicated solid-water systems more rapidly and at a lower computational cost with the aid of ML.

Exploring Spectral and Electrochemical Behavior of Hydroxy‐N‐Benzylideneanilines by Integrated Theoretical and Experimental Approaches

ABSTRACTThe present work explored the effect of –OH group substitution (o/p) on the spectral and electrochemical behavior of N‐benzylideneaniline. The geometry optimization of unsubstituted and (o/p)‐OH‐substituted analogs revealed the coplanarity of the molecules. The vibrational spectra of the compounds were computed using density functional theory (DFT) and compared with the experimental data. The observed bands were assigned based on total energy distribution (TED). Predicted electronic absorption spectra from time‐dependent density functional theory (TD‐DFT) calculation were compared with the UV–visible spectra of the molecules. The analysis of the lowest spin‐allowed (singlet‐singlet) excited states divulged possible electronic transition. The o‐substituted benzylideneaniline possessed the lowest highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) energy gap among the substituted and unsubstituted analogs. The intramolecular contacts were interpreted using natural bond orbital and localized molecular orbital analysis. The –CH=N– linkage was investigated as a bridge for the electron delocalization from the donor to acceptor moieties. The manifestation of a reduction peak in the cyclic voltammetric studies confirmed the electrochemical behavior in the –OH‐substituted molecule, which was diffusion‐controlled. The discrepancy in the electrochemical property concerning the position of the –OH substituent of the candidate molecules was put forward.