Identification of singlet excited electronic states of toluidine isomers

The photoelectron and UV absorption spectra of para-, meta-, and ortho-toluidine in the gas phase are obtained. The photoelectron spectra in the energy region up to 15.5 eV are interpreted based on the B3LYP/6-311+G(d, p) calculations. Based on the TDDFT B3LYP/6-311+G(d, p) calculations and taking into account the obtained interpretation of photoelectron spectra, the UV absorption bands are assigned to particular singlet transitions. For each transition, the electron configuration that makes the dominant contribution to the transition is determined. It is shown that the transition energy for toluidine isomers depends on the energy gap between the corresponding occupied and unoccupied molecular orbitals. It is noted that this dependence is similar for different benzene derivatives.     

Specific effects of a polar solvent in optical absorption spectra of 1,2-naphthoquinone

The optical absorption spectra of 1,2-naphthoquinone in polar (methanol) and nonpolar (n-hexane) solvents are recorded. It is found that the specific effect of a polar solvent, which manifests itself in a hypsochromic shift of the first nπ* band and in a bathochromic shift of the second and third ππ* bands, is caused by the formation of hydrogen bonds between solvent molecules and the molecule under study and, as a result, by a change in the energy gap between the corresponding occupied and unoccupied molecular orbitals. This result is obtained by TDDFT B3LYP/6-311+G(d, p) calculations of electronic spectra, which, in the case of an isolated 1,2-naphthoquinone molecule, reproduce its experimental optical absorption spectra in n-hexane and, in the case of the same molecule forming a complex with methanol molecules by means of hydrogen bonds, reproduce the spectrum of 1,2-naphthoquinone in methanol.     

Molecular structure and spectral (FT-IR,Raman) investigations of 3-aminocoumarin

The molecular structure of 3-Aminocoumarin was determined by conformational analysis. Conformational space was scanned by conformer distribution option of Spartan 08 program package using Merck Molecular Force Field (MMFF) method. Then obtained conformers were optimized by B3LYP/6-311++G(d, p) and B3LYP/6-311G(d, p) levels of Density Functional Theory. As a result of these calculations, only one conformer was determined. Vibrational frequencies of this conformer were calculated by Gaussian 03 program package using the same levels of geometry optimizations. The FT-IR and Raman spectra of 3-Aminocoumarin were recorded and compared with the calculated values. Consequently, a good agreement between experimental and the calculated values were founded. Molecular electrostatic potentials (MEPs), HOMO-LUMO energies, thermodynamic properties and Mulliken atomic charges were also covered in this study.     

Synthesis,structural, and spectroscopic (FT-IR,NMR, and UV) Characterization of 1-(Cyclohexylmethyl)-2-(pyridin-2-yl)-1<Emphasis Type="Italic">H</Emphasis>-benzo[<Emphasis Type="Italic">d</Emphasis>]imidazole by experimental techniques and quantum chemical calculations

The title compound (II), 1-(cyclohexylmethyl)-2-(pyridin-2-yl)-1H-benzo[d]imidazole (C₁₉H₂₁N₃), was synthesized via N-alkylation of 2-(pyridin-2-yl)-1H-benzo[d]imidazole (I). Both compounds I and II were characterized by IR, NMR and UV-vis spectroscopy. Solid-state structure of compound II was determined by single-crystal X-ray diffraction technique. Furthermore, quantum chemical calculations employing density functional theory (DFT/B3LYP) method with the 6–311++G(d, p) basis set were performed for the theoretical characterization of the molecular and spectroscopic features of the compounds. Using the TD-DFT method, electronic absorption spectra of the compounds have been predicted at same level. When the obtained results were compared with the experimental findings, it is seen that theoretical results support the experimental data and a good agreement exists between them.     

Electrophilicity Indices for Peroxyl Radicals

In this work, electrophilicity indices are calculated for 50 peroxyl radicals with density-functional theory (B3LYP hybrid functional and the 6-311+G(d,p) basis set). There is a relationship between general and local electrophilicity indices of peroxyl radicals and Taft inductive constants (σ*) of the substituents at the–OO^? group.     

A Theoretical Study on <Emphasis Type="Italic">N</Emphasis>′-[(<Emphasis Type="Italic">Z</Emphasis>)-(4-Methylphenyl)Methylidene]-4-Nitrobenzohydrazide (NMPMN)

Quantum mechanical calculations of ground state energy, vibration wavenumbers, and electronic absorption wavelengths of N′-[(Z)-(4-methylphenyl)methylidene]-4-nitrobenzohydrazide with C15H13N3O3 empirical formula was performed by using Gaussian 09 program. Becke’s three-parameter exchange functional in conjunction with the Lee-Yang-Parr correlation functional and Heyd-Scuseria-Ernzerhof functional levels of density functional theory (DFT) with the 6-311++G(d,p) basis set were used in the performing of above mentioned calculations. The highest occupied and lowest unoccupied molecular orbital (HOMO and LUMO) energies have been also calculated at the same levels. Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using natural bond orbital (NBO) analysis. Nonlinear optical (NLO) behavior of the title molecule has been examined by the determining of electric dipole moment (μ), polarizability (α), and static first-order hyperpolarizability (β). Finally, molecular electrostatic potential (MEP) surface as well as Mulliken and NBO atomic charges were calculated by using Gaussian 09 program.     

Calculation of the optical spectra of the copper(I) complex with triphenylphosphine,iodine, and 3-pyridine-2-yl-5-phenyl-1<Emphasis Type="Italic">H</Emphasis>-1,2,4-triazole by the DFT method

The IR and UV spectra of the [CuIL(PPh₃)] complex (PPh₃ = triphenylphosphine, L = 3-pyridine- 2-yl-5-phenyl-1Н-1,2,4-triazole) have been analyzed in detail within the density functional theory (DFT) and its time-dependent version TD DFT. The standard functional B3LYP and sets of basis orbitals 6-311G(d,p) and Lanl2DZ are used for the atoms of the elements of periods I and II and for the iodine atom, respectively. The calculated IR spectra of the complex and free ligands coincide with the observed IR bands, due to which one can completely interpret all normal modes and confirm X-ray diffraction (XRD) data. Particular attention is paid to the structure of excited triplet (Т ₁) state in order to explain the role of copper and iodine ions in the formation of photo- and electroluminescence spectra. It is shown that the equilibrium Т ₁ state undergoes structural relaxation after the vertical excitation and significantly changes its electronic nature and the charge transfer structure.     

Specific features of optical absorption in rare-earth orthoaluminate DyAlO<Subscript>3</Subscript>

Polarization spectra of optical absorption of the 4f-4f transition ⁶ H _15/2 → ⁶ F _3/2 in the rare-earth orthoaluminate DyAlO₃ are theoretically and experimentally studied at the temperature T=78 K. It is shown that the nontrivial character of the anisotropy of the polarization absorption spectra at low temperatures can be explained by the J-J mixing of excited multiplets of the 4f ⁹ configuration of Dy³⁺ ions in a low-symmetry crystal field of the orthoaluminate structure. The energy and wave functions of the Stark sublevels within the excited ⁶ F _5/2 multiplet in the 4f ⁹ configuration of the Dy³⁺ rare-earth ion in the crystal field of C _s symmetry are numerically calculated.     

Structural,Spectroscopic, Antimicrobial Activity and DFT Studies on 4-Methyl-<Emphasis Type="Italic">N</Emphasis>-(4-methylphenylsulfonyl)-<Emphasis Type="Italic">N</Emphasis>-phenylbenzenesulfonamide

This study reports the structural characterization of a disulfonimide derivative, 4-methyl-N-(4-methylphenylsulfonyl)-N-phenylbenzenesulfonamide (MPBSA), using spectroscopic and quantum chemical methods. The molecule was characterized with FT-IR, ¹H ¹³C NMR and UV-Vis spectroscopies. Quantum chemical calculations of molecular geometry, vibrational wavenumbers and gauge including atomic orbital (GIAO) ¹H and ¹³C-NMR chemical shifts of the compound were carried out by using density functional method (DFT) at B3LYP/6?311++G(d,p) level of theory. Electronic absorption spectra of the compound have been computed using the time-dependent density functional theory (TD-DFT) method at the same level. A satisfactory consistency between the experimental and theoretical findings was obtained. The antimicrobial activity screening of the compound was performed on some bacteria and fungus species using microdilution method. The results showed that the title molecule have noteworthy antibacterial and antifungal activities.     

X-ray photoelectron and mössbauer spectroscopy studies of the valence state of transition metal ions in Co1–x Fe x Cr2O4 (x = 0.1, 0.2, 0.5) ceramics

The valence state of transition metal ions in the Co_1–x Fe _x Cr₂O₄ (x = 0.1, 0.2, 0.5) system has been investigated using X-ray photoelectron and Mössbauer spectroscopy. It has been shown that, in this system, there are Fe²⁺ and Fe³⁺ ions. The relative Fe³⁺/Fe²⁺ contents have been determined by fitting the experimental Fe 2p photoelectron spectra by a superposition of theoretical spectra of the Fe²⁺ and Fe³⁺ ions, as well as using Mössbauer spectroscopy.     

Spectra of rubidium-like Pd X-Sn XIV ions

Palladium, silver, and cadmium spectra excited in a low-inductive vacuum spark have been recorded on a vacuum grazing-incidence spectrograph with a grating of 3600 lines/mm and 3 m in radius, in the range 120–350 Å. The 4p ⁶4d-(4p ⁶5p + 4p ⁶4f + 4p ⁵4d ²) transitions in rubidium-like Pd X-Cd XII spectra have been investigated. Twenty two new spectral lines have been identified from the Dirac-Fock and Hartree-Fock calculations and the known lines were measured with high accuracy. The fine-structure intervals for the 4p ⁶4d ² D ground state and the energies of six, seven, and ten energy levels of excited configurations in Pd X, Ag XI, and Cd XII, respectively, were determined. On the basis of the analysis of isoelectronic regularities in the position of the energy levels, the previous identifications for the In XIII and Sn XIV spectra were refined.     

Intensity of singlet-triplet transitions in C<Subscript>60</Subscript> fullerene calculated on the basis of the time-dependent density functional theory and taking into account the quadratic response

The singlet-singlet and triplet-triplet absorption spectra of C₆₀ fullerene are calculated using the density functional method and taking into account the theory of linear and quadratic responses. The B3LYP density functional and the 6–31G and 3–21G atomic basis sets are used. The calculations are performed using the D_2h and D_5d symmetry groups, although the real symmetry of the ground state is described by the I _h symmetry group. The matrix elements of the operator of the spin-orbit coupling are calculated and the probabilities of some singlet-triplet transitions are estimated. Taking into account the data in the literature on vibronic interactions of vibrations of the t_1u, t_2u, g _u , and h _u symmetry species, the radiative lifetime of the 1³T_2g → 1¹A _g phosphorescence was estimated to be 45 s. The fact that this time proved to be considerably greater than the experimentally observed total lifetime of the triplet testifies to a fast nonradiative deactivation of the lowest triplet state of C₆₀ fullerene and agrees with a low phosphorescence intensity. The zero-field splitting of some triplets and the intensities of magnetic dipole transitions are discussed.     

Spectral and luminescence properties of gadolinium gallium garnet epitaxial films doped with terbium

Gadolinium gallium garnet single-crystal films containing terbium are grown through liquid-phase epitaxy from a supercooled solution melt in the PbO-B₂O₃ system. The optical absorption spectra in the wavelength range 0.2–10.0 μm and the luminescence spectra excited by synchrotron radiation with energies in the range 3.5–30.0 eV are investigated at temperatures of 10 and 300 K. It is revealed that the optical absorption spectra contain an absorption band with the maximum at a wavelength λ ≈0.260 μm, which corresponds to the spin-allowed electric dipole transition between the electronic configurations 4f ⁸(⁷ F ₆) → 4f ⁷(⁸ S)5d of the Tb³⁺ ions. The narrow low-intensity absorption bands attributed to the 4f → 4f transitions from the ⁷ F ₆ ground level to the ⁷ F _0–5 multiplet levels of the Tb³⁺ ions are observed in the wavelength range 1.7–10.0 μm. In the luminescence spectra measured at a temperature of 10 K, the highest intensity is observed for a band with the maximum at a wavelength λ ≈ 0.544 μm, which is associated with the ⁵ D ₄ → ⁷ F ₅ radiative transition in the Tb³⁺ ion.     

Electronic structure and spectra of CuO

We report the electronic structure of monoclinic CuO as obtained from first principles calculations utilizing density functional theory plus effective Coulomb interaction (DFT + U) method. In contrast to standard DFT calculations taking into account electronic correlations in DFT + U gave antiferromagnetic insulator with energy gap and magnetic moment values in good agreement with experimental data. The electronic states around the Fermi level are formed by partially filled Cu 3d _x²?y² orbitals with significant admixture of O 2p states. Theoretical spectra are calculated using DFT + U electronic structure method and their comparison with experimental photoemission and optical spectra show very good agreement.     

Vibrational Spectroscopic Investigation,First Hyper Polarizability and Homo–Lumo Analysis of Tetrahydroxy-1,4Quinone Hydrate Using Density Functional Theory and Hartree-Fock Method

The FTIR and FT-Raman spectra of tetrahydroxy-1,4quinone hydrate have been recorded in the regions 4000–400 and 3500–50 cm^–1 respectively. Using the observed Fourier-transform infrared spectroscopy (FTIR) and FT-Raman data, a complete vibrational assignment and analysis of the fundamental modes of the compound has been carried out. The optimum molecular geometry, harmonic vibrational frequencies, infrared intensities and Raman scattering activities, were calculated by the density functional theory (DFT/B3LYP) and Hartree–Fock (HF) method with 6-311+G(d,p) basis set. The difference between the observed and scaled wavenumber values of most of the fundamental vibrations is very small. A detailed interpretation of the infrared and Raman spectra of tetrahydroxy-1,4quinone hydrate is also reported. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule.     

Photoelectron Energy Loss in Al(002) Revisited: Retrieval of the Single Plasmon Loss Energy Distribution by a Fourier Transform Method

A Fourier transform (FT) algorithm is proposed to retrieve the energy loss function (ELF) of solid surfaces from experimental X-ray photoelectron spectra. The intensity measured over a broad energy range towards lower kinetic energies results from convolution of four spectral distributions: photoemission line shape, multiple plasmon loss probability, X-ray source line structure and Gaussian broadening of the photoelectron analyzer. The FT of the measured XPS spectrum, including the zero-loss peak and all inelastic scattering mechanisms, being a mathematical function of the respective FT of X-ray source, photoemission line shape, multiple plasmon loss function, and Gaussian broadening of the photoelectron analyzer, the proposed algorithm gives straightforward access to the bulk ELF and effective dielectric function of the solid, assuming identical ELF for intrinsic and extrinsic plasmon excitations. This method is applied to aluminum single crystal Al(002) where the photoemission line shape has been computed accurately beyond the Doniach–Sunjic approximation using the Mahan–Wertheim–Citrin approach which takes into account the density of states near the Fermi level; the only adjustable parameters are the singularity index and the broadening energy Г (inverse hole lifetime). After correction for surface plasmon excitations, the q-averaged bulk loss function, <Im[??1 / ε(E, q)]> _q , of Al(002) differs from the optical value Im[??1 / ε(E, q?=?0)] and is well described by the Lindhard–Mermin dispersion relation. A quality criterion of the inversion algorithm is given by the capability of observing weak interband transitions close to the zero-loss peak, namely at 0.65 and 1.65 eV in ε(E, q) as found in optical spectra and ab initio calculations of aluminum.     

Identification of excited singlet states of chlorophenol isomers

The UV spectra of optical absorption of para-, meta-, and ortho-chlorophenol are recorded in the gas phase. The bands of UV spectra are assigned to the electronic transitions of molecules to definite excited singlet states on the basis of calculations by the TDDFT B3LYP/6-311++G(d, p) method. In each case the electron configuration making the predominant contribution to the particular singlet state is determined. The energies of singlet electronic transitions are shown to depend on the energy spacing between the molecular orbitals involved in these transitions.     

X-ray photoelectron spectroscopy of FeP phosphide

The structure of the outer and inner electron spectra of iron (2p, 3p, 3s, and 3d) and phosphorus (3s and 3p) atoms in FeP monophosphide is studied in detail by the X-ray photoelectron spectroscopy (XPS) method. On the basis of the analysis of the binding energy of electrons, as well as the parameters characterizing the structure of experimental spectra, a conclusion is made that Fe³⁺ (d ⁵) cations in FeP are stabilized in a state with intermediate value of the total spin (IS, S = 3/2). The range of values of intra-atomic parameters (10Dq, J _H ) is established in which the consideration of the high degree of covalence of Fe–P bonds may lead to the stabilization of (FeP₆)^15– clusters in the IS state.     

Specific features of magneto-optical spectra of Tb<Subscript>3</Subscript>Ga<Subscript>5</Subscript>O<Subscript>12</Subscript>

The spectra of magnetic circular dichroism in the range of the ⁷ F ₆→⁵ D ₄ absorption band and the spectra of magnetic circular polarization of luminescence in the range of the ⁵ D ₄→⁷ F ₅ band in the terbium-gallium garnet Tb₃Ga₅O₁₂ are studied at a temperature of 80 K. The optical transitions between the Stark sublevels of the ⁷ F ₆, ⁷ F ₅, and ⁵ D ₄ multiplets are identified based on the analysis of the magneto-optical and optical spectra. It is shown that the experimentally determined symmetry and energy of the Stark sublevels of these multiplets confirm the results of numerical calculations of the energy spectrum of the Tb³⁺ rare-earth ion in terbium-gallium garnet.     

Study of the structure and spectral properties of radical anions of Zn complexes of porphyrins by the method of density functional theory

The structure, solvation energies, and electronic absorption spectra of possible products of the reaction of Zn porphin (Zn-P) with metallic sodium are calculated using methods of density functional theory. Calculated solvation energies of free and bound ions make it possible to assume that, in commonly used aprotic solvents, reduction products occur as \([Na^ + \cdot Zn - P^ - ]_{N, C_m } \) anion-cation contact pairs, with Na⁺ lying along either the NN or C _m C _m axis. This conclusion is consistent with results of calculations of electronic absorption spectra and of modeling of spectral manifestations of the electron photodetachment in frozen matrices.