Vibrational Spectroscopic Properties Research Articles

Electronic and vibrational spectroscopic study complemented with the computational evaluation of hydroxychloroquine mixed with silver nanoparticles

Synthesized silver nanoparticles via laser liquid ablation were characterized using XRD, TEM, EDS, UV–Vis, and Raman spectroscopy. The AgNPs were then conjugated with HCQ at different concentrations. The study aimed to explore the effectiveness of HCQ against malaria and autoimmune diseases as well as how conjugating AgNPs with HCQ would broaden its activity against various infections and diseases, owing to the antimicrobial activity of AgNPs. The electronic and vibrational study of HCQ and its mixture showed a successful conjugation of the two, which would increase the potent of HCQ against SARS Coronavirus (SARS-COV-2) infection. Steady-state absorption measurements revealed a broadband peak at around 337.4 nm (3.68 eV), corresponding to a π to π* transition in the quinoline ring of the HCQ molecule. In addition, the AgNPs Localized Surface Plasmon Resonance (LSPR) band centred around 408 nm exhibited an intensity decrease with an increase in the concentration of HCQ. The experimental Raman spectra exhibited bands similar to the density function theory (DFT) calculated spectra centred at 392 cm−1, 768 cm−1, 1392 cm−1, 2928 cm−1, 3224 cm−1, 3656 cm−1, and 3808 cm−1. TEM, EDS, and XRD analysis confirmed the formation of 8.75 nm AgNPs. Understanding the electronic and vibrational spectroscopic properties of the interaction between HCQ and AgNPs, as deduced from the spectroscopic results supported by DFT, can significantly benefit researchers in the pharmaceutical industry. Researchers could apply this knowledge to overcome drug resistance, repurpose existing drugs, and reduce the side effects of conventional clinically approved drugs.

Anharmonic Vibrational Spectroscopy of Germanium-Containing Clusters, GexC4-x and GexSi4-x (x = 0-4), for Interstellar Detection.

An extensive, high-level theoretical study on tetra-atomic germanium carbide/silicide clusters is presented. Accurate harmonic and anharmonic vibrational frequencies and rotational constants are calculated at the CCSD(T)-F12a(b)/cc-pVT(Q)Z-F12 levels of theory. With growing capabilities to discern more of the chemical composition of the interstellar medium (ISM), an accurate database of reference material is required. The presence of carbon is ubiquitous in the ISM, and silicon is known to be present in interstellar dust grains; however, germanium-containing molecules remain elusive. To begin understanding the presence and role of germanium in the ISM, we present this study of the vibrational and rotational spectroscopic properties of various germanium-containing molecules to aid in their potential identification in the ISM with modern observational tools such as the James Webb Space Telescope. Structures studied herein include rhomboidal (r-), diamond (d-), and trapezoidal (t-) tetra-atomic molecules of the form GexC4-x and GexSi4-x, where x = 0-4. The most promising structure for detection is r-Ge2C2 via the ν4 mode with a frequency of 802.7 cm-1 (12.5 μm) and an intensity of 307.2 km mol-1. Other molecules that are potentially detectable, i.e., through vibrational modes or rotational transitions, include r-Ge3C, r-GeSi3, d-GeC3, r-GeC3, and t-Ge2C2.

Polymorphism in S(+)Clopidogrel-Picrate: Insights from X-ray Diffraction, Vibrational Spectroscopy, Thermal Analysis, and Quantum Chemistry

The crystal structures of two pseudopolymorphic forms of S(+)clopidogrel–picrate are reported. Form 1 crystallizes in the monoclinic space group P21 with an ionic couple S(+)ClopH+·Pic− and a molecule of solvent ethanol in the asymmetric unit, while Form 2 crystallizes in the monoclinic space group C2 with two ionic couples in the asymmetric unit. The configurations and conformations of the ionic couples, held together by ionized +N-H···O hydrogen bonds, are nearly identical in the structures. The self-assembly properties are compared with reported clopidogrel salts, including those used in pharmaceutical formulations. The hydrogen bonds are discussed in reference to the general corresponding behavior of the N-bases picrates and the properties of the acid-base coformers. The preparations of the pseudopolymorphs were optimized toward two different methods: solvent evaporation and mechanochemical treatment. Reproducibility to generate the single crystalline phases was confirmed by thermal and vibrational spectroscopic properties. Periodic third-order density-functional tight binding (DFTB3) calculations predict rather small energy difference between the two pure phases of polymorphs 1 and 2. However, the included solvent molecules in Form 1 decrease the lattice energy for ~10.5 kcal mol−1, which leads to a lower ΔElatt. lattice energy in comparison to Form 2 (by ~7.3 kcal mol−1). All predicted trends are in line with the experimentally observed formation of Form 1 instead of its simulated non-solvated Form 1.

Exploring the Influence of the Phosphorus-Heteroatom Substitution in Nicotine on Its Electronic and Vibrational Spectroscopic Properties.

The influence of phosphorus substitution of nitrogen in heterocyclic compounds on the vibrational spectroscopy as well as frontier molecular orbitals are analyzed. Nicotine with two nitrogen atoms in its structure is taken as the sample system to be studied computationally. By replacing the nitrogen atom in one or both rings of this molecule with phosphorus, three nicotine derivatives are created. The vibrational circular dichroism and infrared spectra of these four molecules in their monomer state, as well as the assemblies up to trimers are determined. The aforementioned spectra are calculated using static quantum chemical calculations employing a cluster-weighted approach. The calculated gas phase spectra of nicotine are compared to their respective experimental spectra. It is observed that the nicotine derivatives with phosphorus in the methylpyrrolidine ring have considerably different gas phase and bulk phase vibrational circular dichroism spectra when compared to nicotine. The phosphorus substitution reduces the energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital as well as altering the polarizability and reactivity of the investigated molecules.

Gas-phase conformational analysis and vibrational signatures of diphenhydramine: Investigating the interplay with hydrochloride

We have performed a comprehensive analysis of the conformational and vibrational spectroscopic properties of Diphenhydramine in the gas phase using potential energy scanning calculations at DFT/B3LYP/6-31++G(d, p) level of theory which identified three different conformational structures. The influence of hydrochloride (HCl) on the energy profile and vibrational frequencies of the most stable conformational structure was investigated. The presence of HCl showed a decrement in the energy by -460.8312 a.u. confirming DPHHCl structurally more stable than isolated DPH. Normal coordinate analysis (NCA) was employed to compute the total potential energy distribution for both the most stable conformational structure and the HCl complex. The results indicate that the DFT-computed vibrational frequencies are in good agreement with previously reported values. HOMO and LUMO was conducted to study the transition profile of the molecule. Additionally, NBO calculations were performed to ensure the stability of electronic structures at the same level of theory.

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.

Synthesis, spectroscopic, and lead(II) binding behavior of three novel dibenzo-18-crown-6 hydrazones

Three novel hydrazonic derivatives of dibenzo-18-crown-6 were synthesized and their vibrational and electronic absorption spectroscopic properties thoroughly investigated. Their lead binding behaviors were also characterized and the observations rationalized by density functional theoretical modeling. All three cis-dihydrazonic compounds are of low overall molecular symmetry with their ether cavity adopting an open configuration at the global energy minima where the hydrazonic side-arms are electronically and vibrationally nonequivalent. Their optical absorption features are dominated by π → π * transitions where one side of the molecule exhibits Lewis acid behavior whereas the other behaves like a Lewis base. In addition to their sensitivity to pH, all three derivatives form stable 2:1 metal-ligand complexes with lead, due to coordination at the ether cavity, in addition to the hydrazone “backbone” and possibly the heterocyclic ring. The most stable lead complex is formed with the thiophene carboxylic acid hydrazide derivative due to favorable soft-soft interactions between lead and the ring-based sulfur atom.

Design, Vibrational and Fluorescence Spectroscopic Properties, and Molecular Docking Studies of 3‐(5‐Bromobenzofuran‐3‐ylmethyl)‐5‐(4‐methoxyphenyl)‐4H‐[1,2,4]‐triazole by Experimental and Density Functional Theory Methods

AbstractIn this work, we have reported the spectral and several other properties of 3‐(5‐bromobenzofuran‐3‐ylmethyl)‐5‐(4‐methoxy‐phenyl)‐4H‐[1,2,4]triazole (BBT) molecule. Primarily, the experimental and computational analyses have been conducted for this molecule and compared the results. The computational studies have been conducted by Gaussian software with the help of DFT/B3LYP/6‐311++G (d, p) basis set. First, we have optimised BBT molecule to conduct the overall computational studies. The detailed computational and experimental vibrational analyses of BBT have been carried out. The electronic absorption and emission spectra of BBT have been observed in a variety of solvents with different solvent parameters like refractive index n, and dielectric constant ϵ. In solvatochromic studies, bathochromic (red) shift have observed in the absorption and emission spectra as an outcome of solute‐solvent interaction due to π → transition. The solvent correlation methods experimentally investigated for the ground and excited‐state dipole moments. Along with these studies, we have also conducted Frontier Molecular Orbital (FMO) and Molecular Electrostatic Potential (MEP) analyses. Further, Molecular docking and drug likeness studies have also been performed to determine the pharmacological properties of the title molecule.

Heating temperatures affect meat quality and vibrational spectroscopic properties of slow- and fast-growing chickens

This study determined the effect of water bath cooking (70°C and 90°C for 40 min) and the extreme heat treatment by an autoclave (121°C for 40 min) on the quality of breast meat of a fast-growing chicken, commercial broiler (CB), and slow-growing chickens, Korat chicken (KC), and Thai native chicken (NC) (Leung Hang Khao), by vibrational spectroscopic techniques, including synchrotron radiation-based Fourier transform infrared (SR-FTIR) microspectroscopy and Fourier transform Raman (FT-Raman) spectroscopy. Taste-enhancing compounds, including inosine-5'-monophosphate (IMP) and guanosine-5'-monophosphate (GMP), were better retained in cooked KC and NC meats than in cooked CB meat (P < 0.05). The high heat treatment at 121°C depleted the amount of insoluble collagen in all breeds (P < 0.05). Shear force values of slow-growing chicken meat were not affected by high heating temperatures (P > 0.05). In addition, the high heat treatment increased protein carbonyl (P < 0.05), while no effect on in vitro protein digestibility (P > 0.05). SR-FTIR microspectroscopy performed better in differentiating the meat quality of different chicken breeds, whereas FT-Raman spectroscopy clearly revealed differences in meat qualities induced by heating temperature. Based on principal component analysis (PCA), distinct characteristics of chicken meat cooked at 70°C were high water-holding capacity, lightness (L*), moisture content, and predominant α-helix structure, correlating with Raman spectra at 3,217 cm-1 (O-H stretching of water) and 1,651 cm-1 (amide I; α-helix). The high heating temperature at 90°C and 121°C exposed protein structure to a greater extent, as evidenced by an increase in β-sheets, which was well correlated with the Raman spectra at 2,968 and 2,893 cm-1 (C-H stretching), tryptophan (880 cm-1), tyrosine (858 cm-1), and 1,042, 1,020, and 990 cm-1 (C-C stretching; β-sheet). SR-FTIR and FT-Raman spectroscopy show potential for differentiation of chicken meat quality with respect to breeds and cooking temperatures. The marked differences in wavenumbers would be beneficial as markers for determining the quality of cooked meats from slow- and fast-growing chickens.

AlOSO: Spectroscopy and Structure of a New Group of Astrochemical Molecules

With the ever-increasing detection of sulfur-bearing molecules and the high abundance and refractory nature of aluminum, the [Al, S, O2] isomers may play an important role in the gas-phase chemistry of circumstellar envelopes and the chemistry on the surface of dust grains. High-level theoretical exploration of the [Al, S, O2] molecular system yielded five isomers, and predictions of their rotational, vibrational, and electronic spectroscopic properties are provided to inform experimental and observational searches. Cis-AlOSO and diamond isomers are isoenergetic and connected via a very small (∼1 kcal mol−1) transition-state barrier. These isomers may act as intermediates along the chemical pathway between Al + SO2 and AlO + SO. Other isomers OAlOS and SAlO2 are stable relative to their corresponding dissociation asymptotes. Large permanent dipole moments of 2.521 D (cis-AlOSO), 1.239 D (diamond), and 5.401 D (OAlOS) predict strong rotational transitions and indicate these molecules as prime candidates for experimental study. Due to the low transition-state barrier, mixing of the vibrational levels is anticipated, complicating the vibrational spectrum. Electronic spectroscopy may be used as a means to differentiate between the two isomers. Strong electronic transitions are predicted to occur in the 200–300 nm range for cis-AlOSO and diamond. Simulated electronic absorption spectra provide a starting point for experimental characterization and spectral deconvolution of these isomers.

A comparative study of meat quality and vibrational spectroscopic properties of different chicken breeds

Chicken breed is one of the key factors that influence meat quality. The quality attributes of breast meat from commercial broiler (CB), Thai native chicken (NC, Leung Hang Khao), and the crossbred Korat chicken (KC) were investigated via synchrotron radiation-based Fourier transform infrared (SR-FTIR) microspectroscopy, Fourier transform Raman (FT-Raman) spectroscopy, and physicochemical analysis. The protein and carbonyl contents of KC and NC meats were higher than that of CB meat, but the lipid content was lower (P < 0.05). CB meat was characterized by high moisture, lightness (L*), and presence of taste-active nucleotides, namely, inosine 5′-monophosphate (IMP) and guanosine 5′-monophosphate (GMP). Moreover, NC meat had the highest insoluble collagen and inosine contents (P < 0.05). The predominant protein secondary structures of KC and NC meats were β-turns and random coils, whereas α-helices were mainly found in CB meat. Based on principal component analysis, the meat quality and spectra were clearly separated by breeds. The high moisture and lipid content of meat corresponded to O–H stretching (3,203 cm−1) and C–H stretching (2,854 cm−1) in the FT-Raman spectra, whereas PO2− stretching (1,240 cm−1), measured via SR-FTIR, was well correlated with the IMP content. In addition, the FT-Raman wavenumber of 934 cm−1, indicating C–C stretching, was correlated with high water-holding capacity (WHC) in KC meat. The quality of meat from slow- and fast-growing chickens significantly varies. Vibrational spectroscopy is a powerful technique that provides insightful molecular information correlated with various meat attributes.

The Spectroscopic Characterization of Halogenated Pollutants through the Interplay between Theory and Experiment: Application to R1122

In the last decade, halogenated ethenes have seen an increasing interest for different applications; in particular, in refrigeration, air-conditioning and heat pumping. At the same time, their adverse effects as atmospheric pollutants require environmental monitoring, especially by remote sensing spectroscopic techniques. For this purpose, an accurate characterization of the spectroscopic fingerprint—in particular, those of relevance for rotational–vibrational spectroscopy—of the target molecules is strongly needed. This work provides an integrated computational–theoretical investigation on R1122 (2-Chloro-1,1-difluoro-ethylene, ClHC=CF), a compound widely employed as a key intermediate in different chemical processes. State-of-the-art quantum chemical calculations relying on CCSD(T)-based composite schemes and hybrid CCSD(T)/DFT approaches are used to obtain an accurate prediction of the structural, rotational and vibrational spectroscopic properties. In addition, the equilibrium geometry is obtained by exploiting the semi-experimental method. The theoretical predictions are used to guide the analysis of the experimentally recorded gas-phase infrared spectrum, which is assigned in the 400–6500 cm region. Furthermore, absorption cross sections are accurately determined over the same spectral range. Finally, by using the obtained spectroscopic data, a first estimate of the global warming potential of R1122 vibrational spectra is obtained.

Vibrational disorder and densification-induced homogenization of local elasticity in silicate glasses

We report the effect of structural compaction on the statistics of elastic disorder in a silicate glass, using heterogeneous elasticity theory with the coherent potential approximation (HET-CPA) and a log-normal distribution of the spatial fluctuations of the shear modulus. The object of our study, a soda lime magnesia silicate glass, is compacted by hot-compression up to 2 GPa (corresponding to a permanent densification of ~ 5%). Using THz vibrational spectroscopic data and bulk mechanical properties as inputs, HET-CPA evaluates the degree of disorder in terms of the length-scale of elastic fluctuations and the non-affine part of the shear modulus. Permanent densification decreases the extent of non-affine elasticity, resulting in a more homogeneous distribution of strain energy, while also decreasing the correlation length of elastic heterogeneity. Complementary 29Si magic angle spinning NMR spectroscopic data provide a short-range rationale for the effect of compression on glass structure in terms of a narrowing of the Si–O–Si bond-angle and the Si–Si distance.

Spectroscopy and radiation-induced chemistry of an atmospherically relevant CH2F2…H2O complex: Evidence for the formation of CF2…H2O complex as revealed by FTIR matrix isolation and ab initio study

Difluoromethane is considered among the environment friendly alternatives to the ozone depleting chlorofluorocarbons. Due to its chemical inertness and lack of UV absorption above 200 nm, this compound can easily come to the upper layers forming complexes with widely abundant atmospheric components, such as water. The radiation-induced degradation of this compound and its complexes may be significant for reliable prediction of its long-term evolution in the environment as well as for development of new ways for its removal. In this work we have studied the vibrational spectroscopic properties and mechanisms of the radiation-induced decay of the CH2F2⋯H2O under the action of X-rays using matrix isolation FTIR spectroscopy and ab initio calculations. The IR spectrum of the complex in an argon matrix was characterized for the first time and assigned to a hydrogen-bonded structure with a binding energy of 11.1 kJ/mol (2.65 kcal/mol) (CCSD(T)/CBS level of theory). Complexation with water leads to a certain suppression of the efficiency of the radiation-induced decomposition of difluoromethane. The obtained results provide evidence for the radiation-induced formation of previously unreported CF2⋯H2O complex (in addition to other oxygen containing molecules, such as COF2 and CO). As demonstrated by calculations, the new difluorocarbene complex reveals a hydrogen bond and it is characterized by a binding energy of 5.73 kJ/mol (1.37 kcal/mol) (CCSD(T)/CBS level of theory).

Spectroscopic (FT-IR, FT Raman and UV-Vis), Quantum Computational and Molecular Docking studies on Propylthiouracil

The vibrational spectroscopic (FT-IR and FT Raman) and electronic properties (UV-Vis) have been investigated experimentally at room temperature and were compared with quantum computational calculations using DFT and TD DFT techniques with 6-311++G(d,p) as the level of theory by GAUSSIAN 09W. The fundamental modes of vibrations were carefully assigned which were compared with experimental vibrations. Theoretical information on the optimized structure, Natural Bond Orbitals (NBO) and NLO were also obtained. The delocalization of electrons due to hyper conjugation was understood using NBO analysis. Data on the stabilization of the molecule due to different transitions were explained using this analysis. Dipole moment, polarizability and first order hyperpolarizability calculations were done. These revealed that the compound may be a suitable NLO material. Thermodynamic properties such as entropy, enthalpy and specific heat of molecule over a temperature range 100-1000 K were studied. The compound was found to be stable for higher temperature range. Local reactivity sites of the compound were studied using Molecular Electrostatic Potential (MEP) and Localized Orbital Locator (LOL) studies, while Pauli exchange repulsion effect was used to obtain Electron Localization Function (ELF). Hence the electrophilic and nucleophilic sites of the molecule were elucidated. A Hirshfeld surface was obtained to study the intermolecular interactions. The HOMO-LUMO energy gap was calculated and compared with the experimental data obtained and was found to be in good agreement. An electrophilicity index of 3.439 explains that the molecule is biologically active. The drug-like nature of the molecule was confirmed using Lipinski’s rule of five. Hence, the protein binding orientations and energies of protein-ligand complexes were predicted using molecular docking studies.

Effect of Ni and Fe substitution on the thermal, structural, vibrational spectroscopic and electrochemical properties of LiMn2O4 cathode material

Spinel LiMn2O4, Li1.025(Mn1.95Ni0.025Fe0.025)O4, and Li1.025(Mn1.9Ni0.025Fe0.05)O4 cathodes were synthesized by a two-step solid-state reaction method. The thermal, structural, vibrational spectra and electrochemical properties of these materials were characterized by using TGA-DTA, XRD, SEM, EDS, Fourier-FT-IR spectroscopy, Raman spectroscopy, and charge-discharge test. The TGA-DTA analysis confirmed that 800°C is the suitable temperature for synthesizing all the samples using Li2CO3, Fe2O3, MnO2, and NiO precursors. The XRD analysis revealed the formation of a single-phase cubic spinel structure with Fd3¯m space group. Two distinct strong absorption peaks were identified by FT-IR analysis in the wavenumber regions of 512 to 621 cm−1. Enhancement of the discharge specific capacity due to Ni and Fe substitution into LiMn2O4 was observed. Among all samples, Li1.025(Mn1.95Ni0.025Fe0.025)O4 exhibited excellent cyclic performance (97.4%) after 50 cycles.

Precursors of tetragonal tungsten bronzes as catalysts in selective reactions: Liquid phase oxidation of diphenyl sulfide and gas phase oxidation of hydrogen sulfide

Mixed metal oxides, of the type (KNaM)xP0.11WV0.2NbOx and (NH4)x/(Na)xP0.11WV0.2NbOx, were prepared by hydrothermal synthesis from lacunary heteropolytungstates, [M4(H2O)2(PW9O34)2]10− (MPW9, with M(II) = Co, Cu or Mn) and their precursor Na8H(PW9O34) (NaPW9), chemically modified by Nb(V) and V(IV). For comparison mixed metal oxides were also synthesized by using a Keggin heteropolytungstates [PW12O40]3− as tungsten precursor. The pristine samples were finally heat-treated at 500 °C in flowing N2 for 2 h. The resulting mixed metal oxides were characterized by several physico-chemical techniques and tested in both the liquid phase catalytic oxidation of diphenyl sulfide (DPS), in friendly environmental conditions (using tert-butyl hydroperoxide as oxidant), and in the gas phase partial oxidation of hydrogen sulfide to sulfur (using air at oxidant). Although the catalytic behavior of these catalysts strongly depends on the composition of catalysts, high activity and selectivity have been achieved over mixed metal oxides in both reactions. The good catalytic performance of species containing Cu(II) was evidenced in both reactions studied and the reactivity of this element could be explained by its structural and vibrational spectroscopic properties.

Spectroscopic study of magnesium dinitrogen and sodium dinitrogen cation

ABSTRACT Despite its likely importance in astrochemistry, pure rotational spectra are not observable for gas-phase N2 since this molecule has no permanent dipole moment. Complexation of monomeric N2 with a cationic metal (MN2+) may be kinetically and thermodynamically favourable, and the detection of such MN2+ molecules could be useful tracers of N2 in order to probe its abundance and kinetics. Highly accurate quartic force field methods have been applied here to compute rotational and vibrational spectroscopic properties of the NaN2+ and MgN2+ molecules via a coupled cluster-based composite approach with additional corrections for post-CCSD(T) electron correlation and relativistic effects. The relative energies of various isomers have also been computed and show that both NaN2+ and MgN2+ have linear ground electronic states. At the highest level of theory, rotational constants (B0) of 4086.9 and 4106.0 MHz are predicted for NaN2+ and MgN2+, respectively, with dipole moments of 6.92 and 4.34 D, respectively, making them rotationally observable even at low concentrations. Post-CCSD(T) electron correlation corrections lower the N–N stretching frequency while relativistic corrections have a much smaller effect putting the fundamental frequencies at 2333.7 and 2313.6 cm−1, respective of NaN2+ and MgN2+ slightly above that in N2H+. Additive corrections do not significantly change the other two vibrational modes. An anharmonic, zero-point corrected N2 dissociation energy of 7.3 and 7.0 kcal mol−1 is, respectively, reported for NaN2+ and MgN2+ suggesting possible formation of these molecules in protoplanetary discs or planetary nebulae that are metal- and nitrogen-rich.

Probing the vibrational spectroscopic properties and binding mechanism of anti-influenza agent Liquiritin using experimental and computational studies

Liquiritin is an anti-viral agent of H1N1 and H3N2 influenza A virus which was reported to inhibit H1N1 and H3N2 NA enzyme with IC50 value of 82.3 and > 100 μM, respectively. The ground state optimized geometry was carried out for Liquiritin molecule through DFT method. The experimental vibrational (FT-IR and FT-Raman) and electronic (UV–Vis) spectral information were analysed and compared with theoretical data. The MEP and Fukui functions were determined for Liquiritin to analyse the electrophilic and nucleophilic attack of the molecule. The NBO and HOMO–LUMO were concluded for Liquiritin to investigate the chemical reactivity and kinetic stability. The druglikeness and ADMET predictions were analysed for Liquiritin, and it confirms the Lipinski’s rule of five. Liquiritin fits very well in the active site cavity of H1N1 and H3N2 NA enzyme with binding energies of − 6.36 and − 5.87 kcal mol−1 and inhibition constants (21.76 and 49.98 ki UM micromol), respectively, through docking study. Consequently, the molecule reveals good biological behaviour in nature and it can act as a probable drug candidate for H1N1 and H3N2 viral influenza.

DFT meets the segmented polarization consistent basis sets: Performances in the computation of molecular structures, rotational and vibrational spectroscopic properties

Quantum-chemical calculations assist the analysis of laboratory spectra, and often provide the only means to determine spectroscopic data that cannot be accessed experimentally. For the purpose, reliable predictions of structural and spectroscopic parameters are required. Although coupled cluster theory in conjunction with to large basis sets and composite schemes can reach impressive accuracies for structural, thermochemical and spectroscopic properties, it is still limited to small sized molecules. DFT represents the working option for medium to large molecular systems. In this context, systematic investigations are required aimed at characterizing the performances of the different DFT model chemistries. In this work, the accuracy of the popular hybrid B3LYP and the double hybrid B2PLYP functionals coupled to the segmented polarization consistent (aug-)pcs-n basis sets in the prediction of molecular structures and rotational- and vibrational spectroscopic parameters are investigated using a benchmark set of molecules of both atmospheric and astrochemical relevance. For comparison purposes, different flavors of Dunning’s triple-ζ basis sets and the SNSD basis set, are also employed. The convergence behavior of the pcs-n hierarchy with n = 1–4 is also addressed to some extent. The results indicate the B3LYP-D3 functional in conjunction with the aug-pcs-1 or SNSD basis sets as a cost-effective model chemistry for applications in the field of rotational and vibrational spectroscopies. Improved accuracy is obtained by coupling the B2PLYP-D3 functional with the aug-pcs-2 or aug-cc-pVTZ triple-ζ basis sets that show an accuracy around 0.003 Å and 0.3° for bond lengths and angles, 1% and 3% for rotational and quartic centrifugal distortion constants, respectively, 12 cm−1 for fundamental frequencies and 3 km mol−1 for IR intensities. The B2PLYP-D3/maug-cc-pVTZ-dH level keeps the same accuracy, with slightly larger deviations for intensities.