A combined experimental and theoretical (DFT and AIM) studies on synthesis, molecular structure, spectroscopic properties and multiple interactions analysis in a novel ethyl-4-[2-(thiocarbamoyl)hydrazinylidene]-3,5-dimethyl-1H-pyrrole-2-carboxylate and its dimer

First-principle study of Cu-, Ag-, and Au-decorated Si-doped carbon quantum dots (Si@CQD) for CO2 gas sensing efficacies

CONTEXT

Nanosensor materials for the trapping and sensing of CO₂ gas in the ecosystem were investigated herein to elucidate the adsorption, sensibility, selectivity, conductivity, and reactivity of silicon-doped carbon quantum dot (Si@CQD) decorated with Ag, Au, and Cu metals. The gas was studied in two configurations on its O and C sites. When the metal-decorated Si@CQD interacted with the CO₂ gas on the C adsorption site of the gas, there was a decrease in all the interactions with the lowest energy gap of 1.084 eV observed in CO₂_C_Cu_Si@CQD followed by CO₂_C_Au_Si@CQD which recorded a slightly higher energy gap of 1.094 eV, while CO₂_C_Ag_Si@CQD had an energy gap of 2.109 eV. On the O adsorption sites, a decrease was observed in CO₂_O_Au_Si@CQD which had the least energy gap of 1.140 eV, whereas there was a significant increase after adsorption in CO₂_O_Ag_Si@CQD and CO₂_O_Cu_Si@CQD with calculated ∆E values of 2.942 eV and 3.015 eV respectively. The adsorption energy alongside the basis set supposition error (BSSE) estimation reveals that CO₂_C_Au_Si@CQD, CO₂_C_Ag_Si@CQD, and CO₂_C_Cu_Si@CQD were weakly adsorbed, while chemisorption was present in the CO₂_O_Ag_Si@CQD, CO₂_O_Cu_Si@CQD, and CO₂_O_Au_Si@CQD interactions. Indeed, the adsorption of CO₂ on the different metal-decorated quantum dots affects the Fermi level (E_f) and the work function (Φ) of each of the decorated carbon quantum dots owed to their low E_f values and high ∆Φ% which shows that they can be a prospective work function-based sensor material.

METHODS

Electronic structure theory method based on first-principle density functional theory (DFT) computation at the B3LYP-GD3(BJ)/Def2-SVP level of theory was utilized through the use of the Gaussian 16 and GaussView 6.0.16 software packages. Post-processing computational code such as multi-wavefunction was employed for result analysis and visualization.

SERS and DFT studies of 2-(trichloroacetyl)pyrrole chemisorbed on the surface of silver and gold coated thin films: In perspective of biosensor applications

The adsorption and orientations of 2-(trichloroacetyl)pyrrole (TCAP) adsorbed on a fabricated silver-coated thin film (SCF), and gold-coated thin film (GCF) were investigated using surface-enhanced Raman scattering (SERS) studies and compared with the normal Raman scattering (nRs) spectrum of TCAP. The observed nRs and SERS spectra of TCAP were validated theoretically using DFT quantum chemical calculations. Initially, the molecular structure of TCAP, TCAP-Ag₃ , and TCAP-Au₄ molecular systems were optimized and analyzed. The fabricated SCF and GCF are characterized using FESEM analysis, which confirms that the silver and gold nanoparticles of the corresponding films are spherical in shape. The obtained significant red-shift in UV-visible spectra of TCAP added on SCF and GCF surfaces reveal that the TCAP strongly adsorbed on SCF and GCF surfaces. The frontier molecular orbitals analysis authenticates the charge-transfer interaction from Ag₃ and Au₄ metal clusters to the TCAP molecule, leading to the adsorption of TCAP molecule on Ag₃ and Au₄ metal clusters, which validates the UV-vis results. SERS spectral analysis confirms that the TCAP chemisorbed on SCF and GCF surfaces with tilted orientation and the corresponding results were validated theoretically. The calculated SERS enhancement factor values illustrate that the GCF surface exhibits a higher SERS signal enhancement than the SCF surface. Therefore, the present investigation will be useful for the development of active SERS substrates and pyrrole-related biosensors.

One-Dimensional Organic-Inorganic Material (C6H9N2)2BiCl5: From Synthesis to Structural, Spectroscopic, and Electronic Characterizations

The new organic–inorganic compound (C₆H₉N₂)₂BiCl₅ (I) has been grown by the solvent evaporation method. The one-dimensional (1D) structure of the allylimidazolium chlorobismuthate (I) has been determined by single crystal X-ray diffraction. It crystallizes in the centrosymmetric space group C2/c and consists of 1-allylimidazolium cations and (1D) chains of the anion BiCl₅²⁻, built up of corner-sharing [BiCl₆³⁻] octahedra which are interconnected by means of hydrogen bonding contacts N/C–H⋯Cl. The intermolecular interactions were quantified using Hirshfeld surface analysis and the enrichment ratio established that the most important role in the stability of the crystal structure was provided by hydrogen bonding and H···H interactions. The highest value of E was calculated for the contact N⋯C (6.87) followed by C⋯C (2.85) and Bi⋯Cl (2.43). These contacts were favored and made the main contribution to the crystal packing. The vibrational modes were identified and assigned by infrared and Raman spectroscopy. The optical band gap (Eg = 3.26 eV) was calculated from the diffuse reflectance spectrum and showed that we can consider the material as a semiconductor. The density functional theory (DFT) has been used to determine the calculated gap, which was about 3.73 eV, and to explain the electronic structure of the title compound, its optical properties, and the stability of the organic part by the calculation of HOMO and LUMO energy and the Fukui indices.

2,4-Dimorpholino-4-yl-6-(4-nitrophenoxy)-[1,3,5]-triazine: Structural and spectroscopic study using experimental and DFT method

2,4-Dimorpholino-4-yl-6-(4-nitrophenoxy)-[1,3,5]-triazine (DMNT) was synthesized and the molecular structure and vibrational frequencies were studied by density functional theory (DFT) method. The functional used was Becke’s three parameter exchange functional combined with the Lee-Yang-Parr correlation (B3LYP) and the standard basis set was 6-31G(d) for all atoms. The Fourier Transform-Infra Red (FT-IR) and FT-Raman spectra of DMNT were recorded and complete assignments of the observed vibrational frequencies are done. The assignments were confirmed by isotopic labelling. The structural parameters, harmonic vibrational frequencies, IR intensities and Raman intensities of DMNT in the ground-state were also computed. Non-linear optical behaviour of DMNT was analysed by examining the properties like electric dipole moment, polarizability and hyperpolarizability. Molecular properties such as ionization potential, electro-negativity, chemical potential and chemical hardness were obtained from molecular orbital analysis. Hyper conjugative interaction and charge delocalization taking place in DMNT was confirmed by Natural bond analysis studies. UV-Vis spectrum of DMNT was also recorded to understand the electronic properties.

Graphical Abstract:

Experimental and Theoretical Study on the Interaction of P-Aminophenol Hydrochloride with H2O

UV-Vis absorption spectra, cyclic voltammetry and 1H nuclear magnetic resonance (1H NMR) spectra were applied to explore the hydrogen bond interactions of p-aminophenol hydrochloride (PAH) with H2O. The results indicated the hydrogen bonds were formed in PAH–H2O system. The anodic/cathodic peak potentials and UV-Vis absorption bands of PAH in H2O could be affected due to the interactions. The results of density functional theory, atoms in molecules theory and natural bond orbital analyses further confirmed the existence of hydrogen bonds between the phenolic hydroxyl, –NH3 + protons and Cl− of PAH and H2O. Furthermore, the π-π stacking was suggested between PAH benzene rings from the 1H NMR spectra at higher concentrations.

Antimycobacterial, antimicrobial activity, experimental (FT-IR, FT-Raman, NMR, UV-Vis, DSC) and DFT (transition state, chemical reactivity, NBO, NLO) studies on pyrrole-isonicotinyl hydrazine

As part of a study of pyrrole hydrazone, we have investigated quantum chemical calculations, molecular geometry, relative energy, vibrational properties and antimycobacterial/antimicrobial activity of pyrrole-2-carboxaldehyde isonicotinyl hydrazone (PCINH), by applying the density functional theory (DFT) and Hartree Fock (HF). Good reproduction of experimental values is obtained and with small percentage error in majority of the cases in comparison to theoretical result (DFT). The experimental FT-IR and Raman wavenumbers were compared with the respective theoretical values obtained from DFT calculations and found to agree well. In crystal structure studies the hydrated PCINH (syn-syn conformer) shows different conformation than from anhydrous form (syn-anti conformer). The rotational barrier between syn-syn and syn-anti conformers of PCINH is 12.7kcal/mol in the gas phase. In this work, use of FT-IR, FT-Raman, ¹H NMR, ¹³C NMR and UV-Vis spectroscopies has been made for full characterization of PCINH. A detailed interpretation of the vibrational spectrum was carried out with the aid of normal coordinate analysis using single scaling factor. Our results support the hydrogen bonding pattern proposed by reported crystalline structure. The calculated nature of electronic transitions within molecule found to be π→π*. The electronic descriptors study indicates that PCINH can be used as robust synthon for synthesis of new heterocyclic compounds. The first static hyperpolarizability (β₀) of PCINH is calculated as 33.89×10^-30esu_, (gas phase); 68.79×10^-30 (CHCl₃), esu; 76.76×10^-30esu (CH₂Cl₂), 85.16×10^-30esu (DMSO). The solvent induced effects on the first static hyperpolarizability were studied and found to increase as dielectric constants of the solvents increases. Investigated molecule shows better NLO value than Para nitroaniline (PNA). The compound PCINH shows good antifungal and antibacterial activity against Aspergillus niger and gram-positive bacteria Bacillus subtilis, respectively. The compound also shows good antituberculosis activity against Mycobacterium tuberculosis H37Rv using the microplate alamar blue assay (MABA).

Antimicrobial activity, structural evaluation and vibrational (FT-IR and FT-Raman) study of pyrrole containing vinyl derivatives

In this paper we present structural and vibrational study of three vinylpyrrole derivatives: 2-Cyano-3-(1H-pyrrol-2-yl)-acrylamide (CPA), 1-(1H-Pyrrol-2-yl)-Pent-1-en-3-one (PP) and 1-(1H-Pyrrol-2-yl)-but-1-en-3-one (PB), using ab initio, DFT and experimental approaches. The quantum chemical calculation have been performed on B3LYP method and 6-311+G(d,p) basis set. The experimental FT-IR and Raman wavenumbers were compared with the respective theoretical values obtained from DFT calculations and found to agree well. The experimental FT-IR and Raman study clearly indicate that the compound exist as dimer in solid state. The binding energies of (CPA), (PP) and (PB) dimers are found to be 20.95, 18.75 and 19.18 kcal/mol, respectively. The vibrational analysis shows red shifts in v(N-H) and v(C=O) stretching as result of dimer formation. Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using NBO analysis. Topological and energetic parameters reveal the nature of interactions in dimer. The local electronic descriptors analyses were used to predict the reactive sites in the molecule. Calculated first static hyperpolarizability of CPA, PP and PB is found to be 10.41×10(-30), 18.93×10(-30), 18.29×10(-30) esu, respectively, shows that investigated molecules will have non-linear optical response and might be used as non-linear optical (NLO) material. These vinylpyrrole compounds (CPA), (PP) and (PB) showed antifungal and antibacterial activity against Aspergillus niger and gram-positive bacteria Bacillus subtili.

Study on Pyrrole 4-Pyrazoline Derivatives: Experimental and Quantum Chemical Approaches

As part of a study on pyrrole derivatives we report here a combined experimental and quantum chemical study of pyrrole 4-pyrazoline biheterocyclic derivatives. The structure of the synthesised compounds have been studied using experimental IR, UV, 1H and 13C NMR spectroscopic analyses along with density functional theory (DFT) calculations using the B3LYP functional with 6–311+G (d,p) basis set. The global, local reactivity, and thermodynamic parameters support the analysis. All the experimental vibrational bands have been discussed and assigned to normal modes on the basis of our calculations. In addition, the computed 1H and 13C NMR data, obtained by DFT calculations, are found to be in good agreement with the experimental data and serve as valuable tools in identifying the products. The vibrational analysis shows red shifts in vN–H and vC=O stretching vibrations as a result of dimer formation. The theoretical electronic absorption spectra have been calculated by using time dependent-DFT methods. The static first hyperpolarizability (β0) values for the synthesized pyrrole–pyrazoline derivatives 4A–D are calculated as 16.97 × 10–30, 47.64 × 10–30, 65.40 × 10–30, 65.39 × 10–30 esu, respectively, and increase from 4A to 4C as a result of the addition of an –NO2 acceptor in 4B and two –NO2 group acceptors in 4C. However, an additional –Cl group in 4D on the phenyl ring attached to the pyrazoline moiety does not result in a clear change from 4C. The calculated static and dynamic hyperpolarizability results show that the investigated molecules might be used as non-linear optical materials.

New Diethyl Ammonium Salt of Thiobarbituric Acid Derivative: Synthesis, Molecular Structure Investigations and Docking Studies

The synthesis of the new diethyl ammonium salt of diethylammonium(E)-5-(1,5-bis(4-fluorophenyl)-3-oxopent-4-en-1-yl)-1,3-diethyl-4,6-dioxo-2-thioxohexaydropyrimidin-5-ide 3 via a regioselective Michael addition of N,N-diethylthiobarbituric acid 1 to dienone 2 is described. In 3, the carboanion of the thiobarbituric moiety is stabilized by the strong intramolecular electron delocalization with the adjacent carbonyl groups and so the reaction proceeds without any cyclization. The molecular structure investigations of 3 were determined by single-crystal X-ray diffraction as well as DFT computations. The theoretically calculated (DFT/B3LYP) geometry agrees well with the crystallographic data. The effect of fluorine replacement by chlorine atoms on the molecular structure aspects were investigated using DFT methods. Calculated electronic spectra showed a bathochromic shift of the π-π* transition when fluorine is replaced by chlorine. Charge decomposition analyses were performed to study possible interaction between the different fragments in the studied systems. Molecular docking simulations examining the inhibitory nature of the compound show an anti-diabetic activity with Pa (probability of activity) value of 0.229.

Experimental and theoretical study on the hydrogen bonding between dopamine hydrochloride and N,N-dimethyl formamide

The hydrogen bonding between dopamine hydrochloride (DH) and N,N-dimethyl formamide (DMF) were investigated by UV-visible spectra (UV-Vis), cyclic voltammetry (CV) and density functional theory (DFT). It was found that the position of UV-Vis absorption band and the anodic/cathodic peak potentials of DH were all affected by the concentrations of DH in DMF. It was suggested that hydrogen bonding were formed between DH and DMF, which was confirmed by the DFT results. AIM analyses were performed to elucidate the nature of the hydrogen bonding in the mixtures.

Assessment of conformational, spectral, antimicrobial activity, chemical reactivity and NLO application of Pyrrole-2,5-dicarboxaldehyde bis(oxaloyldihydrazone)

An orange colored pyrrole dihydrazone: Pyrrole-2,5-dicarboxaldehyde bis(oxaloyldihydrazone) (PDBO) has been synthesized by reaction of oxalic acid dihydrazide with 2,5 diformyl-1H-pyrrole and has been characterized by spectroscopic analysis (1H, 13C NMR, UV-visible, FT-IR and DART Mass). The properties of the compound has been evaluated using B3LYP functional and 6-31G(d,p)/6-311+G(d,p) basis set. The symmetric (3319, 3320 cm(-1)) and asymmetric (3389, 3382 cm(-1)) stretching wave number confirm free NH2 groups in PDBO. NBO analysis shows, inter/intra molecular interactions within the molecule. Topological parameters have been analyzed by QTAIM theory and provide the existence of intramolecular hydrogen bonding (N-H⋯O). The local reactivity descriptors analyses determine the reactive sites within molecule. The calculated first hyperpolarizability value (β0=23.83×10(-30) esu) of pyrrole dihydrazone shows its suitability for non-linear optical (NLO) response. The preliminary bioassay suggested that the PDBO exhibits relatively good antibacterial and fungicidal activity against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Streptococcus pyogenes, Candida albicans, Aspergillus niger. The local reactivity descriptors--Fukui functions (fk+, fk-), local softnesses (sk+, sk-) and electrophilicity indices (ωk+, ωk-) analyses have been used to determine the reactive sites within molecule.

Vibrational spectra, electronic absorption, nonlinear optical properties, evaluation of bonding, chemical reactivity and thermodynamic properties of ethyl 4-(1-(2-(hydrazinecarbonothioyl)hydrazono)ethyl)-3,5-dimethyl-1H-pyrrole-2-carboxylate molecule by ab initio HF and density functional methods

In this work, detailed vibrational spectral analysis of ethyl 4-(1-(2-(hydrazinecarbonothioyl)hydrazono)ethyl)-3,5-dimethyl-1H-pyrrole-2-carboxylate (EHCHEDPC) molecule has been carried out using FT-IR spectroscopy and potential energy distribution (PED). Theoretical calculations were performed by ab initio RHF and density functional theory (DFT) method, using 6-31G(d,p) and 6-311+G(d,p) basis sets. The other carried outwork cover: structural, thermodynamic properties, electronic transitions, bonding, multiple interaction, chemical reactivity and hyperpolarizability analysis. The results of the calculation were applied to the simulated spectra of (EHCHEDPC), which show excellent agreement with observed spectra. The vibrational analysis shows red shift in both group, the proton donor (pyrrole N-H) and proton acceptor (C=O of ester) indicating the presence of intermolecular hydrogen bonding. Time dependent density functional theory (TD-DFT) has been used to find electronic excitations and their nature. The results of natural bond orbital (NBOs) analysis show the charges transfer and delocalization in various intra- and intermolecular interactions. The binding energy of intermolecular multiple interactions is calculated to be 12.54 kcal mol(-1) using QTAIM calculation. The electronic descriptors analyses reveal the investigated molecule used as precursor for heterocyclic derivatives synthesis. First hyperpolarizability (β0) has been computed to evaluate non-linear optical (NLO) response.

FT-IR, Laser-Raman spectra and quantum chemical calculations of methyl 4-(trifluoromethyl)-1H-pyrrole-3-carboxylate-A DFT approach

In this study the experimental and theoretical vibrational frequencies of a newly synthesized anti-tumor and anti-inflammatory agent namely, methyl 4-(trifluoromethyl)-1H-pyrrole-3-carboxylate have been investigated. The experimental FT-IR (4000-400cm(-1)) and Laser-Raman spectra (4000-100cm(-1)) of the molecule in solid phase have been recorded. The theoretical vibrational frequencies and optimized geometric parameters (bond lengths, bond angles and torsion angles) have been calculated using density functional theory (DFT/B3LYP: Becke, 3-parameter, Lee-Yang-Parr and DFT/M06-2X: highly parameterized, empirical exchange correlation function) with 6-311++G(d,p) basis set by Gaussian 03 software, for the first time. The assignments of the vibrational frequencies have been done by potential energy distribution (PED) analysis using VEDA 4 software. The theoretical optimized geometric parameters and vibrational frequencies have been found to be in good agreement with the corresponding experimental data and results in the literature. In addition, the highest occupied molecular orbital (HOMO) energy, the lowest unoccupied molecular orbital (LUMO) energy and the other related molecular energy values of the compound have been investigated using the same theoretical calculations.