Experimental (FT-IR, FT-Raman) and theoretical (HF and DFT) investigation and HOMO and LUMO analysis on the structure of p-fluoronitrobenzene

Engineering Sulfur-Containing Polymeric Fire-Retardant Coatings for Fire-Safe Rigid Polyurethane Foam

With the advantages of lightweight and low thermal conductivity properties, polymeric foams are widely employed as thermal insulation materials for energy-saving buildings but suffer from inherent flammability. Flame-retardant coatings hold great promise for improving the fire safety of these foams without deteriorating the mechanical-physical properties of the foam. In this work, four kinds of sulfur-based flame-retardant copolymers are synthesized via a facile radical copolymerization. The sulfur-containing monomers serve as flame-retardant agents including vinyl sulfonic acid sodium (SPS), ethylene sulfonic acid sodium (VS), and sodium p-styrene sulfonate (VSS). Additionally, 2-hydroxyethyl acrylate (HEA) and 4-hydroxybutyl acrylate are employed to enable a strong interface adhesion with polymeric foams through interfacial H-bonding. By using as-synthesized waterborne flame-retardant polymeric coating with a thickness of 600 µm, the coated polyurethane foam (PUF) can achieve a desired V-0 rating during the vertical burning test with a high limiting oxygen index (LOI) of >31.5 vol%. By comparing these sulfur-containing polymeric fire-retardant coatings, poly(VS-co-HEA) coated PUF demonstrates the best interface adhesion capability and flame-retardant performance, with the lowest peak heat release rate of 166 kW m-2 and the highest LOI of 36.4 vol%. This work provides new avenues for the design and performance optimization of advanced fire-retardant polymeric coatings.

Predicting the degradation potential of Acid blue 113 by different oxidants using quantum chemical analysis

In this work, quantum chemical analysis was used to predict the degradation potential of a recalcitrant dye, Acid blue 113, by hydrogen peroxide, ozone, hydroxyl radical and sulfate radical. Geometry optimization and frequency calculations were performed at ‘Hartree Fock’, ‘Becke, 3-parameter, Lee–Yang–Parr’ and ‘Modified Perdew-Wang exchange combined with PW91 correlation’ levels of study using 6-31G* and 6-31G** basis sets. The Fourier Transform-Raman spectra of Acid blue 113 were recorded and a complete analysis on vibrational assignment and fundamental modes of model compound was performed. Natural bond orbital analysis revealed that Acid blue 113 has a highly stable structure due to strong intermolecular and intra-molecular interactions. Mulliken charge distribution and molecular electrostatic potential map of the dye also showed a strong influence of functional groups on the neighboring atoms. Subsequently, the reactivity of the dye towards the oxidants was compared based on the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy values. The results showed that Acid blue 113 with a HOMO value -5.227 eV exhibits a nucleophilic characteristic, with a high propensity to be degraded by ozone and hydroxyl radical due to their lower HOMO-LUMO energy gaps of 4.99 and 4.22 eV respectively. On the other hand, sulfate radical and hydrogen peroxide exhibit higher HOMO-LUMO energy gaps of 7.92 eV and 8.10 eV respectively, indicating their lower reactivity towards Acid blue 113. We conclude that oxidation processes based on hydroxyl radical and ozone would offer a more viable option for the degradation of Acid blue 113. This study shows that quantum chemical analysis can assist in selecting appropriate advanced oxidation processes for the treatment of textile effluent.

Molecular structure, spectroscopic (IR, Raman, Ultra Violet-Visible) and nonlinear optical investigation on DCBLPZ: A novel semiorganic NLO material

Dichlorobis(L-proline) zinc(II) (DCBLPZ) is an excellent nonlinear optical (NLO) material because of its ability to exhibit high second harmonic generation and having significant optical transparency. In this work, electro-optical properties of the titled material has been thoroughly investigated by Hartree–Fock (HF) and Density functional theory using different basis sets in C1 symmetry. The calculated geometrical parametres and vibrational frequencies were found to be in good agreement with reported experimental results. Highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) studies were carried out to understand the intramolecular charge transfer within the molecule. Total dipole moment ([Formula: see text]), polarizability ([Formula: see text]), anisotropy of polarizability ([Formula: see text] and first hyperpolarizability ([Formula: see text]) values were calculated. The static first hyperpolarizability value is found to be six times higher than urea. Ultra violet-visible spectrum of DCBLPZ molecule was calculated by time-dependent density functional theory (TD-DFT) in gas phase using different functionals. The calculated value of absorption wavelength was found at 234[Formula: see text]nm using TD-B3LYP/[Formula: see text]* level of theory and was in good agreement with experimental value (230[Formula: see text]nm) than other applied methods. Our results give us flexibilty to predict about possible intramolecular charge transfer from both the chlorine atoms toward both the proline units through zinc atom in the studied metallic complex. The other important parametres such as frontier molecular orbital’s (FMO), global reactivity descriptors and molecular electrostatic potential have also been calculated and discussed.

Experimental and theoretical studies on IR, Raman, and UV-Vis spectra of quinoline-7-carboxaldehyde

Spectroscopic properties of quinoline-7-carboxaldehyde (Q7C) have been studied in detail both experimentally and theoretically. The FT-IR (4000-50 cm(-1)), FT-Raman (4000-50 cm(-1)), dispersive-Raman (3500-50 cm(-1)), and UV-Vis (200-400 nm) spectra of Q7C were recorded at room temperature (25 °C). Geometry parameters, potential energy surface about CCH(O) bond, harmonic vibrational frequencies, IR and Raman intensities, UV-Vis spectrum, and thermodynamic characteristics (at 298.15K) of Q7C were computed at Hartree-Fock (HF) and density functional B3LYP levels employing the 6-311++G(d,p) basis set. Frontier molecular orbitals, molecular electrostatic potential, and Mulliken charge analyses of Q7C have also been performed. Q7C has two stable conformers that are energetically very close to each other with slight preference to the conformer that has oxygen atom of the aldehyde away from the nitrogen atom of the quinoline.

Quantum chemical and spectroscopic (FT-IR and FT-Raman) investigations of 3-methyl-3h-imidazole-4-carbaldehyde

FT-IR and FT-Raman spectra of 3-methyl-3h-imidazole-4-carbaldehyde (3M3HI4C) were recorded in the region 4000-400cm(-1) and 3500-50cm(-1), respectively. Optimized geometric parameters, conformational equilibria, normal mode frequencies, and corresponding vibrational assignments of 3M3HI4C were theoretically examined by quantum chemical methods for the first time. All vibrational frequencies were assigned in detail with the help of total energy distribution (TEDs). The experimental wavenumbers were compared with the scaled vibrational frequencies determined by DFT/B3LYP method. The results showed that the B3LYP/6-311++G(d,p) method predicts vibrational frequencies and the structural parameters effectively. The most stable conformer of the title compound was determined. The total electron density and molecular electrostatic potential surfaces of the molecule were constructed by using B3LYP/6-311++G(d,p) method to display electrostatic potential (electron+nuclei) distribution. The electronic properties HOMO and LUMO energies were measured. The lower energy band was assigned to the HOMO→LUMO transition. Natural bond orbital analysis of title molecule has been performed to indicate the presence of intramolecular charge transfer. Energies, relative stabilities, and dipole moments of title molecule were also compared and analyzed in the gas phase and in solvents. Furthermore, solvent effects on the geometry and vibrational frequency of 3M3HI4C were studied theoretically at the DFT/B3LYP level in combination with the conductor polarizable continuum model (C-PCM).

Experimental FT-IR, Laser-Raman and DFT spectroscopic analysis of 2,3,4,5,6-Pentafluoro-trans-cinnamic acid

In this study, the experimental and theoretical vibrational frequencies of a newly synthesized 2,3,4,5,6-Pentafluoro-trans-cinnamic acid have been investigated. The experimental FT-IR (4000-400 cm(-1)) and Laser-Raman spectra (4000-100 cm(-1)) of the molecule in solid phase have been recorded. The theoretical vibrational frequencies and optimized geometric parameters (bond lengths and bond angles) have been calculated by using density functional theory (DFT/B3LYP: Becke, 3-parameter, Lee-Yang-Parr) and DFT/M06-2X (the highly parameterized, empirical exchange correlation function) quantum chemical methods with 6-311++G(d,p) basis set by Gaussian 09W software, for the first time. The assignments of the vibrational frequencies have been done by potential energy distribution (PED) analysis by 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 with the results in the literature. In addition, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energies and the other related molecular energy values have been calculated and depicted.

Vibrational spectra of quinoline-4-carbaldehyde: combined experimental and theoretical studies

The FT-IR (4000-50 cm(-1)), FT-Raman (4000-50 cm(-1)) and Dispersive-Raman (3500-50 cm(-1)) spectra of solid sample of quinoline-4-carbaldehyde (Q4C) have been recorded. The molecule structure, vibrational frequencies, IR intensities, Raman intensities and thermodynamic properties of the two possible aldehyde rotamers of Q4C have been obtained with the Hartree-Fock (HF) and density functional B3LYP calculations employing the 6-311++G(d,p) basis set. Q4C has two stable conformers, in one of which the O atom of the aldehyde is oriented to form a H-bond with one of the hydrogens of quinoline, while in the other there is no such a H bond. The conformer with an extra H-bond is more stable and, thus it is the ground state. The computed vibrational frequencies of the lowest energy conformer agree also slightly better than those of the higher energy rotamer with the experimental frequencies after the computed frequencies are scaled. The temperature dependence of the standard heat capacities (C), standard entropies (S) and standard enthalpy (H) changes of Q4C has been discussed.

Determination of structural and vibrational properties of 6-quinolinecarboxaldehyde using FT-IR, FT-Raman and dispersive-Raman experimental techniques and theoretical HF and DFT (B3LYP) methods

The FT-IR (4000-50 cm(-1)), FT-Raman (4000-50 cm(-1)) and Dispersive-Raman (3500-50 cm(-1)) spectra of solid sample of 6-quinolinecarboxaldehyde (6QC) have been recorded. The structure, vibrational frequencies, IR intensities, Raman activities and thermodynamic properties of the two possible aldehyde rotamers of 6QC have been calculated at the Hartree-Fock (HF) and density functional B3LYP levels employing 6-311++G(d,p) basis set. The complete assignments were performed on the basis of the potential energy distribution (PED) of the all vibrational modes. Since HF and B3LYP mode definitions of this molecule are quite similar to each other, we only give in Table 3 PED of Rot1 calculated at B3LYP level for the sake of simplicity. Potential energy surface has been scanned over the C3-C2-C1O16 torsion angle. When the O atom of the aldehyde is farther away than the nitrogen atom of the quinoline, 6QC has the lowest possible energy, and thus is in its ground state. The scaled theoretical frequencies of the lowest energy rotamer agree also slightly better than those of the higher energy rotamer with the experimental frequencies. The thermodynamic characteristics of the ground state of 6QC have been theoretically investigated at 298.15 K temperature.

Spectroscopic analysis (FT-IR/FT-Raman) and molecular structure investigation on m-fluoronitrobenzene using hybrid computational calculations

In the present investigation, the FT-IR/FT-Raman spectra of the m-fluoronitrobenzene (m-FNBZ) are recorded. The fundamental frequencies are assigned and the computational calculations are performed by DFT (B3LYP, B3PW91 and MPW1PW91) methods with 6-31++G(d,p) and 6-311++G(d,p) basis sets and the corresponding results are tabulated. The computed values of frequencies are scaled by using suitable factors. The distortion of the structure of the compound due to the substitutions of Fl and NO(2) is investigated. The alternation of the vibrational pattern of the pedestal molecule related to the substitutions is analyzed. A study on the electronic properties; absorption wavelengths, excitation energy, dipole moment and frontier molecular orbital energies, are performed by time dependent DFT (TD-DFT) approach. The electronic structure and the assignment of the absorption bands in the electronic spectra of steady compounds are discussed. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. Besides frontier molecular orbitals (FMO), molecular electrostatic potential (MEP) was performed. Mulliken charges of the m-FNBZ molecule was also calculated and interpreted. The thermodynamic properties (heat capacity, entropy, and enthalpy) of the title compound at different temperatures were calculated in gas phase.