Search

[Display omitted] • Mechanisms of the p -methoxyphenylpiperazine motif absorption and emission are studied. • While the excitation is based on a n,π → π* transition, the emission is π*→π. • The N(4) atom as a part of a 6-membered aliphatic ring adopts specific geometries. • DFT calculations with NBO and QTAIM analysis support the spectroscopic data. The p -methoxyphenylpiperazine motif can be found in many biologically active molecules, including approved drugs. It is characterized by a relatively weak fluorescence, which can be employed in different types of studies involving molecules with this motif. In this work, a thorough analysis of the absorption, excitation and emission spectra of the diphenyl(aminomethyl)phosphine and tris(aminomethyl)phosphine derivatives of p -methoxyphenylpiperazine, supported by the DFT calculations (ωB97XD/6-311++G(d,p)) with NBO and QTAIM analysis also for different model molecules (e.g. 1-(4-methoxyphenyl)-4-methylpiperazine) enabled determination of the mechanisms underlying beneath the electronic transitions and allowed to rationalize mixed solvent effects observed in electronic spectra of the studied compounds. Electronic transition from the ground state to the first excited state can be regarded as the n,π → π* transition with no solvatochromic effects, however the hydrogen bonds between the HBD solvent molecules and the nitrogen atom bound directly to the aromatic ring (N(4)) are shifting strongly the 1st absorption or excitation band maxima to the higher energies. Fluorescence band, as a result of the electron transition from the equilibrated 1st excited state to the ground state, can be described as the π*→π with positive solvatochromism. N(4) in the excited states adopts a sp2 hybridization and is no longer able to form HBs. On the other hand, increased electron density on the aromatic ring makes the emission processes vulnerable to its direct environment. [ABSTRACT FROM AUTHOR]

[Display omitted] • The electronic spectra of various chalcones in different solvents were interpreted. • The effect of substituents on the CT band of chalcone derivatives was established. • The converged gas-phase geometries of the studied chalcones was optimized. • Optimized geometrical structures were optimized using DFT PBE0 functional with the basis set 6-311++G** • Spectral properties of substituted chalcones are compared with parent and related ketones. • The theoretical calculations were comparable with the experimental data. The electronic spectra of the title compounds were measured in ethanol and cyclohexane. Three band systems are distinguished in the spectra of which the first and second band systems are attributed to local excitation of Ph CH and Ph CO rings. The third absorption band is assigned to a charge transfer (CT) band and is associated with the CO−CH=CH moiety. The solvent plays an important role in the absorption spectra and causes the CT band to consist of two electronic transitions. The effect of substituents on the phenyl rings on the charge transfer band of chalcone derivatives was also established in the two solvents. The converged gas-phase geometries of the studied chalcones was optimized using the DFT PBE0 functional with the basis set 6-311++G**. DFT calculations has been performed for an ethanol solution (using TD-PBE0/6-311++G**) level to understand electronic transitions on terms of energies and oscillator strengths to study the substituent effect on the electronic transitions of the chalcone derivatives. To consider the solvation effect of ethanol on the absorptions, the integral equation formalism variant of the polarizable continuum model (IEFPCM) was used. The calculated energies were in good agreement with experiment results. The molecular modelling technique was followed to monitor the effect of substitutions on the HOMO/LUMO energy and total dipole moment. Transitions between natural transition orbitals are also described as part of this study. [ABSTRACT FROM AUTHOR]

Diazene is the smallest member of the azo compound which has distinct chemical properties widely used in synthetic chemistry. In order to understand the structures and properties of diazene through different stages, the intermolecular interactions need to be studied. We have reported the many-body interactions of linear and cyclic diazene oligomers (mono to pentamer) in gas and water solvent in addition to spectroscopic characterization. It is observed that the sum of two body interaction energy contributes more to binding energy than relaxation energy. Upon solvation, significant changes have been observed in infrared and electronic absorption spectra of linear and cyclic diazene oligomers in the gas phase compared to the water solvent state. [Display omitted] • Spectroscopic study of linear and cyclic diazene oligomers in gas and water solvent. • Upon solvation, significant changes observed in the spectroscopic characterization. • NTOs studied for diazene oligomers in gas & solvent, IEFPCM used for solvent effect. • Many-body interaction of linear and cyclic diazene oligomers in gas and water solvent. • Sum of 2-body interaction contributes more to binding energy than relaxation energy. The present study reports the many-body analysis and spectroscopic characterization of linear and cyclic diazene oligomers in gas and water solvent states. The oligomers of diazene from monomer to pentamer have been considered for the study. The spectroscopic studies such as geometrical parameters, infrared spectra, electronic absorption spectra, and natural transition orbitals (NTOs) were reported. Many-body analysis techniques have been implemented to study the interactions among the diazene oligomers. These calculations have been performed using exchange and correlation functional (B3LYP) and 6–311++G (d,p) basis set. The geometrical parameters and infrared modes of monomer diazene in the gas state are well-matched with the available experimental determinations at this level of theory. A significant change in vibrational modes of linear and cyclic diazene oligomers has been observed in the gas phase-to-water solvent state. The time-dependent density functional theory (TD-DFT) has been used to calculate the electronic absorption spectra of diazene oligomers. The Wavelength of electronic transitions, oscillator strength, and HOMO to LUMO gap has been reported. Many-body analysis shows that two-, three-, four-, and five-body energies have a remarkable contribution to the binding energy in addition to relaxation energies. All these calculations have been performed using Gaussian 16 program package. [ABSTRACT FROM AUTHOR]

Diazene is the smallest member of the azo compound which has distinct chemical properties widely used in synthetic chemistry. In order to understand the structures and properties of diazene through different stages, the intermolecular interactions need to be studied. We have reported the many-body interactions of linear and cyclic diazene oligomers (mono to pentamer) in gas and water solvent in addition to spectroscopic characterization. It is observed that the sum of two body interaction energy contributes more to binding energy than relaxation energy. Upon solvation, significant changes have been observed in infrared and electronic absorption spectra of linear and cyclic diazene oligomers in the gas phase compared to the water solvent state. [Display omitted] • Spectroscopic study of linear and cyclic diazene oligomers in gas and water solvent. • Upon solvation, significant changes observed in the spectroscopic characterization. • NTOs studied for diazene oligomers in gas & solvent, IEFPCM used for solvent effect. • Many-body interaction of linear and cyclic diazene oligomers in gas and water solvent. • Sum of 2-body interaction contributes more to binding energy than relaxation energy. The present study reports the many-body analysis and spectroscopic characterization of linear and cyclic diazene oligomers in gas and water solvent states. The oligomers of diazene from monomer to pentamer have been considered for the study. The spectroscopic studies such as geometrical parameters, infrared spectra, electronic absorption spectra, and natural transition orbitals (NTOs) were reported. Many-body analysis techniques have been implemented to study the interactions among the diazene oligomers. These calculations have been performed using exchange and correlation functional (B3LYP) and 6–311++G (d,p) basis set. The geometrical parameters and infrared modes of monomer diazene in the gas state are well-matched with the available experimental determinations at this level of theory. A significant change in vibrational modes of linear and cyclic diazene oligomers has been observed in the gas phase-to-water solvent state. The time-dependent density functional theory (TD-DFT) has been used to calculate the electronic absorption spectra of diazene oligomers. The Wavelength of electronic transitions, oscillator strength, and HOMO to LUMO gap has been reported. Many-body analysis shows that two-, three-, four-, and five-body energies have a remarkable contribution to the binding energy in addition to relaxation energies. All these calculations have been performed using Gaussian 16 program package. [ABSTRACT FROM AUTHOR]

We systematically studied the vibrational-resolved electronic spectra of group IV dichlorides using the Franck–Condon approximation combined with the Duschinsky and Herzberg–Teller effects in harmonic and anharmonic frameworks (only the simulation of absorption spectra includes the anharmonicity). Calculated results showed that the band shapes of simulated spectra are in accordance with those of the corresponding experimental or theoretical ones. We found that the symmetric bend mode in progression of absorption is the most active one, whereas the main contributor in photoelectron spectra is the symmetric stretching mode. Moreover, the Duschinsky and anharmonic effects exert weak influence on the absorption spectra, except for PbCl 2 molecule. The theoretical insights presented in this work are significant in understanding the photophysical properties of MCl 2 (M = C, Si, Ge, Sn, Pb) and studying the Herzberg–Teller and the anharmonic effects on the absorption spectra of new dichlorides of this main group. [ABSTRACT FROM AUTHOR]

The electronic absorption spectra of some 2-azidobenzothiazoles were measured in different solvents. The effects of solvent and substitution on the spectra were investigated. Substitution by a bromine atom and by a nitro group have significant effects on both band maxima and band intensity. Correlation between the spectra of the studied compounds and the corresponding hydrocarbons proved to be weak, whereas the correlation between the observed spectra and those calculated is adequate. Theoretical treatment of the ultraviolet spectra of the studied compounds was carried out by using the TD–DFT procedures, at the B3LYP level and the 6-311+G ∗∗ basis sets, the results compared well with the experimental values. The computed molecular orbitals of the ground state indicate that some orbitals are “localized- π ” or “localized σ ” molecular orbitals while the others are delocalized orbitals. The calculated functions of the excited states lead to an accurate assignment of the bands observed in the spectra. [ABSTRACT FROM AUTHOR]

This study reports the spectroscopic characterization and second hyperpolarizability of the odd spin states of acetonitrile at B3LYP/aug-cc-pVDZ level of theory. The spectroscopic parameters studied in gas phase and water solvent. Upon changes of spin states of acetonitrile significant changes are observed in the spectroscopic study. Natural transition orbitals (NTOs) study also reported for acetonitrile in gas phase and water solvent. From nonlinear optical study it is observed that second hyperpolarizability of odd spin states of acetonitrile are more responsive than the first hyperpolarizability. [Display omitted] • Spectroscopic study of odd spin state of acetonitrile in gas and water solvent reported. • The solvent effect taken in to the consideration for the study using IEFPCM model. • The Natural transition orbital studied for the acetonitrile in gas phase and in water solvent. • An increase in field strength decreases the HOMO to LUMO gap in gas and solvent acetonitrile. • Thorough nlo study confirmed acetonitrile is more responsive to 2nd hyperpolarizability than 1st. The present study reports the spectroscopic characterization and second hyperpolarizability of odd spin states of acetonitrile in gas phase and water solvent. The odd spin states of acetonitrile are singlet, triplet and quintet spin state of acetonitrile have been considered for the study. The spectroscopic characterization viz. energy, geometrical parameters, infrared and electronic absorption spectra, molecular orbitals (MOs) their energies and natural transitions orbitals (NTOs) in gas phase and water solvent state reported at B3LYP/aug-cc-pVDZ level of theory. The second hyperpolarizability values are obtained using various methods and basis sets for comparison. It has been observed that the second hyperpolarizability values for the odd spin states of acetonitrile are more positive than the first hyperpolarizability. It is clearly seen that the effect of spin on spectroscopic parameters except on energy. The singlet gas phase acetonitrile calculations are well matching with the available experimental determinations. The TDDFT approach has been used to study electronic absorption spectra of all spin states of acetonitrile in gas phase and in water solvent. The IEFPCM model implemented in studying acetonitrile in water solvent at B3LYP/aug-cc-pVDZ level of theory. It is observed that HOMO to LUMO gap is larger for singlet than the triplet and quintet spin state and it decrease with an increase in strength of an applied field. All these calculations performed using Gaussian 16 program package. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesis of new disazobenzo[ c ]cinnolines were carried out. • The effects of the substituents, solvents, acidic and basic media on the absorption spectra of the dyes were investigated. • Azo-hydrazone tautomeric equilibria in different solvents for the dyes were observed. • Voltammetric and spectroelectrochemical behaviour of some of dyes were evaluated. A series of disazobenzo[ c ]cinnoline dyes was prepared by coupling reaction of 3,8-dihydroxybenzo[ c ]cinnoline with diazotised aromatic amines. The structures of these dyes were confirmed using UV–Vis, FTIR, 1H NMR, LC-MS/MS and LC-MS/TOF spectroscopic techniques. 13C NMR, 13C-DEPT, 1H–1H COSY, 1H–13C HMQC and 1H–13C HMBC spectra of dye 12 were demonstrated in this study. In addition, the effects of the substituent attached to the phenyl ring, solvent and acid-base on the UV-Vis spectra of the dyes were investigated. Besides, voltammetric and spectroelectrochemical behaviours of four disazobenzo[ c ]cinnolines (2 , 8 , 11 and 13) in acetonitrile (ACN) solution were also evaluated. It was observed that the disazobenzo[ c ]cinnoline derivatives indicated reversible voltammetric behaviour in acetonitrile-tetrabutylammonium perchlorate (ACN-TBAP) solution. A square-wave potential step method coupled with optical spectroscopy was used to probe switching times and optic contrast of the dyes. [ABSTRACT FROM AUTHOR]

• This work aims to understand the origin of the electronic spectra of Fe3+ (d5), Cr3+ (d3), and V3+ (d2) containing jarosites. • The electronic spectrum of the Fe-jarosite is currently assigned to spin forbidden transitions. This work shows that the spectra essentially arise due to tetragonal distortion of the metal ion coordination, and thereby obviates the need for invoking spin forbidden transitions. • The absorption spectra of Cr- and V- jarosite are also assigned to transitions predicted for the tetragonal distortion of the metal ion coordination. This work aims to understand the origin of the electronic spectra of Fe3+ (d5), Cr3+ (d3), and V3+ (d2) containing jarosites. The electronic spectrum of the Fe-jarosite is currently assigned to spin forbidden transitions. This work shows that the spectra essentially arise due to the tetragonal distortion of the coordination symmetry of the Fe3+ ion in the jarosite crystal, and thereby obviates the need for invoking spin forbidden transitions. The absorption spectra of Cr- and V-jarosite are also assigned to transitions predicted for the tetragonal distortion of the metal ion coordination. The electronic term symbols are worked out using the correlation diagram and Tanabe-Sugano diagram for orbital splitting for all three systems employing ab initio and DFT methods. The bandgaps were computed and corroborated with the experimentally measured values to support the low symmetry at the metal center. [ABSTRACT FROM AUTHOR]

• The visible absorption of AOH+ is due to the HOMO → LUMO transition. • The visible absorption of AO0 is due to the (HOMO-1) → LUMO transition. • The vibronic coupling play a significant role in the absorption spectrum of the AO. • The best agreement with the experiment gives the X3LYP/6-31G(d,p) level of theory. • During photoexcitation, a small electron transfer occurs in the AO central ring. The time-dependent density functional theory (TD-DFT) was used to obtain vibronic absorption spectra of acridine orange dye (AO) in an aqueous solution that were in good agreement with the experiment. The protonated and neutral forms of the dye have been investigated. The results of calculations using various functionals and basis sets have been analyzed. The best agreement with experiment was given by the level of theory X3LYP/6-31G(d,p). AO molecular orbitals involved in electronic transitions due light absorption in the visible region of the spectrum have been obtained. The dipole moments and atomic charges of the ground and excited states of the AO molecule have been calculated. Maps of the electrostatic potential have been drawn. An insignificant photoinduced electron transfer was found in the central ring of the chromophore of the dye molecule. According to our calculations, the vibronic coupling and the Boltzmann distribution play a significant role in the absorption spectra of the AO. [ABSTRACT FROM AUTHOR]

2-(2′-Hydroxyphenyl) thiazole-4-carboxaldeyde (aldehyde 1) and hemiacetal 2 were selected to study the mechanism of excited-state intramolecular proton transfer and the detecting of Al3+ ion in methanol by using density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods. Our theoretical results are in good agreement with the experimental values. The intramolecular H-bond is enhanced in the first excited-state based on the analyses of structural parameters, frontier molecular orbitals and electronic spectra. The stronger intramolecular H-bond is more favorable for ESIPT process. In order to further demonstrate the proton transfer process, we constructed the potential energy curves of probe 1 and 2 in both ground- and excited-states, and concluded that proton transfer processes in probe 1 and 2 are apt to happen in the S 1 state. In addition, the Mayer bond order, energy gap and absorption and fluorescence spectra were applied to interpret the process of detection of Al3+ ion. Unlabelled Image • The intramolecular H-bonds are obviously enhanced in the S 1 state which can facilitate the ESIPT process. • The calculated absorption and fluorescence spectra of 1 are coincident well with the experimental observation. • Proton transfer process in probe 1 and 2 are apt to happen in the S 1 state, and they are hard to occur in the S 0 state. • The rigid planar structure produced by chelation makes fluorescence peaks redshift and evidently enhances its intensity. [ABSTRACT FROM AUTHOR]

Non-planar boron subphthalocyanine chloride is a talented photoelectric material and has been widely applied. In this paper, we have investigated the effects of axial halogen substitutions on electronic spectra of boron subphthalocyanines by combining DFT/TDDFT calculations and available experimental data in solution and in the solid state. We utilize long range separated density functional and polarizable continuum model to obtain the electronic structure and absorption spectra. The computed frontier molecular orbital energy matches well with experiment in dichloromethane and the simulated spectra correctly reproduce the trend of experiment in toluene. Furthermore, we model two configurations (convex-to-convex and concave-to-concave) of dimers of boron subphthalocyanines based on experimental structures in thin film: From F to Cl to Br substitution, the simulated wavelength of absorption peaks in the visible region slightly increases; in contrast, the absorption strength decreases. Moreover, our calculated results suggest that the convex-to-convex configurations of dimers may be the main contributors to the absorption spectra of X-BsubPC (X = F, Cl, Br) in thin film, though no experimental spectra of thin film of X-BsubPC (X = F, Br) yet. Finally, we find that CAM-B3LYP is able to reproduce the energy of frontier molecular orbitals quite well. Unlabelled Image • The larger surface area of X-BsubPC (X = F, Cl, Br) monomer, the smaller absorption strength. • Different configurations of BsubPC dimers have different contributions to absorption spectra. • From F to Cl to Br substitution of X-BsubPC, wavelength/strength of absorption peak slightly increases/decreases. • CAM-B3LYP functional is able to reproduce experimental results quiet well. [ABSTRACT FROM AUTHOR]