Electronic Transition Spectra Research Articles

Molecular docking, QTAIM analysis, UV-Vis spectra, vibrational analysis, and electronic properties of Lantadenes C and D — A complete comparative study

We have done geometry optimization of two conformers of Lantadene series C and D. The fundamental vibrational frequencies with intensity have been done by using B3LYP/6-311G (d, p) method. The complete vibrational assignments of wavenumbers are made on the basis of potential energy distribution (PED). The nonbonding interactions in Lantadenes C and D are calculated by using the same level theory at the bond critical point (BCP). The calculated topological parameters at BCP are utilized to determine the nature and strength of interactions. We have also computed HOMO–LUMO gap and plotted frontier orbital HOMO–LUMO surfaces, molecular electrostatic potential surfaces to explain the reactive nature of Lantadenes C and D. The electronic transition spectra UV–Vis spectra of Lantadenes C and D are calculated by using TDDFT theory. The values of hyperpolarizability show a probable use of these compounds in electro-optical applications. The natural bonding orbital theory is utilized to calculate transition of electron from donor to acceptor which is very useful to describe nonbonding as well as bonding interactions. The calculated value of Log [Formula: see text] and Log [Formula: see text] for Lantadene C Lantadene D established its pharmaceutical behaviors. The biological activity of Lantadenes C and D is also calculated by using PASS online server for [Formula: see text]. The docking of Lantadene C Lantadene D is also performed by using Auto dock with predicted drug by Swiss dock online server.

Preparation of some Complexes of Nickel(II) and Copper (II) Metals with Macrocyclic Ligand, 1,7,9,15 tetra-aza-3,5,11,13 difurano-cyclo-1,6,9,14-hexa-deca tetra ene

The complexes of Nickel(II) and Copper(II) metals have been prepared with the macrocyclic ligand-1,7,9, 15-tetra-aza-3, 5,11,13- - difurano-cyclo-1,6,9,14-hexa deca tetra-ene. The complexes of both the metals have been characterised by usual physico-chemical methods such as elemental analysis, measurement of electrical conductance, magnetic moment and electronic transition spectra of the complexes and I.R. spectral behaviour of both ligands and the complexes. All the complexes of both the metals have been found to be non-electrolyte, mono-meric, paramagnetic with octahedral geometryy . T he general molecular formula of the complexes have been found to be [M(L) (X)2] Where M= Nickel(II) and Copper(II) Cations, L= ligand and X= monodentate anions.

Differential evolution reveals the effect of polar and nonpolar solvents on carotenoids: A case study of astaxanthin optical response modeling

• Unique software that simulates optical response of biological pigments was developed • Differential evolution is used for finding the best model to fit experimental data • Multimode Brownian oscillator models were created to simulate carotenoid absorption • The optimal settings of Differential evolution allowing fast convergence were found • Differential evolution allowed distinguishing models for polar and nonpolar solvents The task to simulate realistic absorption spectra of electronic transitions in pigment molecules takes the form of the art of optimization, particularly if one must choose between the quality of the results obtained and the calculation time necessary to get such quality. The semiclassical theory of optical response provides us with a good opportunity to escape a so-called sum-over-state procedure of considering the innumerable number of vibronic states of a pigment by applying a correlation function approach. This approach, known as the multimode Brownian oscillator model (MBOM), involves replacing an infinite set of vibronic states, which interacts with an electronic transition, with a finite set of effective vibronic modes. Thus, the parameters of effective vibronic modes and an electronic transition can be found only by fitting experimental data. This situation gives rise to the following problem: as the number of free parameters increases, it becomes more difficult to find a single solution. To overcome this obstacle, differential evolution (DE), a method of global optimization, which is based on the idea of natural selection, seems to be the right choice. To test the efficiency of DE in solving quantum mechanical problems, we simulated absorption spectra of astaxanthin (AST) in 18 different organic solvents by using the MBOM. To do so, we developed software that implements both the DE algorithm and linear absorption modeling procedures. We have shown that simulating practically identical AST spectra, DE allows determining the effect of polar and nonpolar solvents on several parameters of MBOM of AST with high accuracy.

Gas-phase optical absorption spectra of the indene cation (C9H8 +)

The electronic transition spectra of the indene molecular cation (In, ) in the 550–580 nm region has been measured in the gas phase in direct absorption. The spectra were experimentally recorded using sensitive cavity ring-down spectroscopy in a supersonically expanding planar plasma. Two lifetime-broadened vibronic bands are assigned to the - electronic transition system of In. A set of indicative spectroscopic parameters have been obtained from a band contour analysis of the 0 band in combination with supporting ab-initio calculations. The inferred Lorentz line width of indicates an upper state lifetime of . The laboratory data are compared to the diffuse interstellar bands (DIBs), and no matches can be found. Upper limits for In column densities in the diffuse interstellar medium have also been estimated from six sightline spectra.

High-Resolution Electronic Spectrum of the 1,4,6-Heptatrienyl Radical in the Gas Phase.

We report the gas-phase identification of the 1,4,6-heptatrienyl (C7H9) radical via its - electronic transition spectrum. The optical absorption spectrum in the 590-630 nm region is recorded using cavity ring-down spectroscopy in combination with a supersonic plasma jet. An analysis of the rotationally resolved origin band spectrum has allowed an accurate determination of spectroscopic constants for both the electronic ground and excited states of this radical. Ab initio calculations at the CASPT2/cc-pVTZ level have been performed to predict the radical structure and molecular constants that are in good agreement with the experimental results. By combination with available experimental data for the allyl and 1,4-pentadienyl radicals, we extrapolate an excitation energy gap between the ground and first excited states of a long C2n-1H2n+1 polyenyl chain converging to a residual energy gap, suggesting the presence of residual nonuniform C-C bond lengths in a long polyenyl chain.

Synthesis, characterization, theoretical calculations of novel benzoic acid based azo molecules and their use in effective extraction of Hg(II) ions from aqueous medium

In this study, two series of benzoic acid derivative azo compounds were synthesized using coupling reaction and characterized by various spectroscopic techniques. By using o-, m-, p-chloroaniline and o-, m-, p-nitroaniline as starting materials, the effects of the directing groups on the color intensity of azo dyes were investigated. It was concluded that the nitro group increased both the reaction efficiency and the color intensity. Optimized molecular structures, vibrational and electronic transition spectra, NMR chemical shift values, frontier molecular orbitals and MEP diagrams of each molecule were calculated using the 6-311G(d,p) basis set. All calculations were performed and compared with both Density Functional Theory (DFT) and Hartree-Fock (HF) methods. Experimental and theoretical results were found to be quite compatible with each other. The extraction capabilities of all synthesized azo derivatives were investigated using various transition metal picrates such as Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, Pb2+ cations. Solvent extraction studies of azo derivatives revealed that all compounds showed strong binding ability against Cu2+ and especially Hg2+ ions and were able to remove the Hg2+ cation from aqueous medium at a high rate (97.3%).

Local structures and dynamics of interfacial imidazolium-based ionic liquid depending on the electrode potential using electrochemical attenuated total reflectance ultraviolet spectroscopy

Recently, ionic liquids (ILs) have attracted attention as prospective electrolytes for Li-ion batteries, with safe performance. Herein, the dynamics of the IL at the electrochemical interface, which is the key to the electrochemical reaction, was monitored using attenuated total reflectance far- and deep-ultraviolet (ATR-FUV-DUV) spectroscopy. An original measurement system, which combined an ATR-FUV-DUV spectrometer with a Kretschmann type (fully metal-coated prism) electrochemical setup, was assembled. Spectral measurements and assignments were performed for the 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([EMIM][TFSI])/Pt electrode (∼7 nm) interface. The incident light in the FUV and DUV regions entered a measurement system comprising an [EMIM][TFSI]/Pt electrode/ATR sapphire prism, and the potential-dependent absorption spectra were measured in the 180–450 nm range. This in-situ spectroscopic technique is unique in that the electronic transition spectra of the interfacial IL can be obtained. By switching the applied potentials, temporal spectral changes (i.e. relaxation signals) were tracked at wavelengths of 450 nm and 221 nm, where the direct electronic absorption of the IL was active and inactive, respectively. Comparing these relaxation times, it was revealed that the absorption signal at 221 nm changed more slowly than that at 450 nm. This indicated that the molecular conformations that affected the electronic absorption of the interfacial ILs changed slowly. Considering the surface-normal dipole selection rule for molecules on a metal surface, it is suggested that the slow changes in the molecular conformations can be ascribed to the potential-dependent interfacial orientations of [EMIM]+.

Synthesis, spectroscopic, and computational studies on molecular charge-transfer complex of 2-((2-hydroxybenzylidene) amino)-2-(hydroxymethyl) propane-1, 3-diol with chloranilic acid: Potential antiviral activity simulation of CT-complex against SARS-CoV-2

An innovative charge-transfer complex between the Schiff base 2-((2-hydroxybenzylidene) amino)-2-(hydroxymethyl) propane-1,3-diol [SAL-THAM] and the π-acceptor, chloranilic acid (CLA) within the mole ratio (1:1) was synthesized and characterized aiming to investigate its electronic transition spectra in acetonitrile (ACN), methanol (MeOH) and ethanol (EtOH) solutions. Applying Job`s method in the three solvents supported the 1:1 (CLA: SAL-THAM) mole ratio complex formation. The formation of stable CT- complex was shown by the highest values of charge-transfer complex formation constants, KCT, calculated using minimum-maximum absorbance method, with the sequence, acetonitrile > ethanol > methanolDFT study on the synthesized CT complex was applied based on the B3LYP method to evaluate the optimized structure and extract geometrical and reactivity parameters. Based on TD-DFT theory, the electronic properties, 1H and 13C NMR, IR, and UV-Vis spectra of the studied system in different solvents showing good agreement with the experimental studies. MEP map described the possibility of hydrogen bonding and charge transfer in the studied system. Finally, a computational approach for screening the antiviral activity of CT - complex towards SARS-CoV-2 coronavirus protease via molecular docking simulation was conducted and confirmed with molecular dynamic (MD) simulation.

Rotationally resolved electronic S1 spectra of tryptoline and oxindole: Reversal of the 1La and 1Lb state character

Rotationally resolved S1←S0 fluorescence excitation spectra of the lowest electronic transitions (origin bands) of tryptoline (TRY) and oxindole (OXI) have been recorded and analyzed. A higher vibronic band of OXI has also been observed and assigned. The derived inertial parameters from the fits provide detailed information about their conformational or tautomeric structures in both the ground and excited electronic states. These molecules exhibit significantly different transition dipole moment orientations relative to the parent reference frame of indole that signify S1 state characters having principal parentage in a 1La state for OXI and a 1Lb state for TRY.

Computational studies on electronic and optical properties of dopamine derivatives structure: A DFT study**

Abstract Dopamine is considered an important molecule that plays several essential roles in the human body, and herein lies the key to this paper on the electronic and optical properties of dopamine and its derivatives, such as quinone and L-dihydroxyphenylalanine (L-DOPA), using DFT and TD-DFT methods, respectively. Our findings show that dopamine has a dielectric behavior, whereas quinone and L-DOPA have semiconductor behaviors in the ground and excited states. By computing the optical properties, we disclose that the electronic transition spectrum of dopamine, quinone and L-DOPA are observed in the ultra-violet region, visible spectrum, and (ultraviolet and visible regions), respectively. Other properties, such as ionization potential, electronic affinity, hardness and softness are also calculated due to their importance in sensor applications and sensing.

Topological transitions in electronic spectra: Crossover between Abrikosov and Josephson vortices

The electronic structure of a vortex line trapped by a planar defect in a type-II superconductor is analyzed within the Bogoliubov-de Gennes theory. The normal reflection of electrons and holes at the defect plane results in the topological transition in the spectrum and formation of a new type of quasiparticle states skipping or gliding along the defect. This topological transition appears to be a hallmark of the initial stage of the crossover from the Abrikosov to the Josephson vortex type revealing in the specific behavior of the quantized quasiparticle levels and density of states. The increase in the resulting hard and soft gaps affects the vortex mobility along the defect plane and splitting of the zero bias anomaly in the tunneling spectral characteristics.

Synthesis, photophysical properties, and density functional theory studies of phenothiazine festooned vinylcyclohexenyl-malononitrile.

A novel phenothiazine derivative conjugated with vinylcyclohexenyl-malononitrile (PTZ-CDN) was synthesized through the Knoevenagel reaction of 10-octyl-10H-phenothiazine-3,7-dicarbaldehyde with 2-(3,5,5-trimethylcyclohex-2-en-1-ylidene)-malononitrile and fully characterized. The UV-vis absorption spectra of PTZ-CDN in different solvents showed a λmax band at 497-531 nm with a high molar extinction coefficient attributed to intramolecular charge transfer (ICT) with the characteristics of a π-π* transition. Increasing the solvent polarity resulted in a bathochromic shift of λmax . The PTZ-CDN fluorescence emission spectra were more sensitive to increasing the solvent polarity than the absorption spectra; they displayed a blue shift of λem by 85 nm. To understand the behaviour of the PTZ-CDN derivative, Stokes' shift ( with respect to the solvent polarity, Lippert-Mataga and linear solvation-energy relationship (LSER) models were applied in which the LSER showed better regression than the Lippert-Mataga plots (r2 = 0.9627). Finally, the TD-density functional theory (DFT) electronic transition spectra in dioxane and dimethyl formamide (DMF) were calculated. The DFT data showed that λmax resulted from the support of the highest occupied molecular orbital to the lowest unoccupied molecular orbital transition with 74% and 99% in dioxane and DMF, respectively.

X-ray crystal structure, spectroscopic and DFT computational studies of H-bonded charge transfer complexes of tris (hydroxymethyl)aminomethane (THAM) with chloranilic acid (CLA)

The crystal and molecular structures of two new synthesized charge transfer complexes produced from the reaction of tris(hydroxymethyl)aminomethane, THAM and 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone (chloranilic acid, CLA) in the mole ratios (2:1) [I] and (1:1) [II], have been studied. The; FT-IR and 1H NMR spectral data of the complexes are confirmed by single-crystal X-ray crystallography. The single-crystal X-ray crystallography, indicated the formation of both inter- and intra-molecular hydrogen bonding as well as the proton transfer from CLA to THAM. The electronic transition spectra of these two complexes as acetonitrile (AN), methanol (MeOH), ethanol (EtOH) solutions are recorded. The molecular compositions of the formed complexes in the three solvents determined by Job's method, support 1:1 mol ratio complex, whatever the polarity of the solvent. The high values of charge transfer complex formation constants, KCT determined by applying the minimum–maximum absorbance method, indicated the formation of stable CT-complexes, with the order Ethanol > Methanol ≫ Acetonitrile. Computational study incorporated the use of TD-DFT with PCM as solvation model are applied for energy minimization and estimation of the stabilization energy for the produced complexes. The geometrical parameters (bond lengths and angles) of the formed CT complexes are computed and analyzed. Furthermore, Mulliken atomic charges, molecular potential energy surface, HOMO and LUMO molecular orbitals of the formed complexes are presented. A good agreement between experimental and DFT computational analysis has been found.

A2Πu and 14Σu- States of Br2+ Studied by [1+1] Two-Photon Dissociation Spectroscopy in a Cold Ion Beam.

The A2Πu-X2Πg and 14Σu--X2Πg electronic transition spectra of Br2+ have been studied in the 500-720 nm wavelength range in a cold ion beam using a cryogenic cylindrical ion trap velocity map imaging spectrometer. The cryogenic ion trap produces a rotationally and vibrationally cold mass selected ion beam of Br2+, which simplifies the experimental spectra from vibrational hot bands and bands of mixed isotopic species. Vibrationally resolved photofragment excitation spectra are recorded for individual isotopologues of Br2+ (79Br2+, 79Br81Br+, 81Br2+) by [1+1] two-photon dissociation spectroscopy. Velocity map imaging of the photofragmented Br+ ions provides complementary information in the determination of spin-orbit states involved in corresponding electronic transitions. An experimental identification of the 14Σu- state has becomes possible based on the present experimental results and previously reported theoretical calculations. Vibrational analyses of the photofragment excitation spectra have yielded spectroscopic parameters, including state origins, harmonic frequencies, and anharmonic constants, for both A2Πu and 14Σu- states. The observed A2Πu state spin-orbit splitting and the "spin-forbidden" 14Σu--X2Πg transition band intensities indicate considerable spin-orbit couplings between the 14Σu- and A2Πu states. In addition, two groups of weak vibrational bands are also observed in the experimental spectra of 79Br81Br+, which may be due to symmetry-forbidden transitions from the X2Πg ground state to low-lying gerade states.

Electronic transitions of tungsten monosulfide

Electronic transition spectrum of the tungsten monosulfide (WS) molecule in the near infrared region between 725 nm and 885 nm has been recorded using laser ablation/reaction free-jet expansion and laser induced fluorescence spectroscopy. The WS molecule was produced by reacting laser - ablated tungsten atoms with 1% CS2 seeded in argon. Fourteen vibrational bands with resolved rotational structure have been recorded and analyzed, which were organized into six electronic transition systems. Least-squares fit of the measured line positions yielded molecular constants for the electronic states observed. The ground state has been identified to be the X3Σ−(0+) state with bond length, ro, and vibrational frequency, ΔG1/2, determined to be 2.0676 Å and 556.7 cm−1 respectively. Molecular constants and potential energy curves of low-lying Λ-S states and Ω sub-states of the WS molecule have been calculated at the MRCISD + Q level of theory with spin-orbit coupling. Calculated molecular properties of the ground and low-lying electronic states are generally in good agreement with experimental determinations. This work represents the first experimental investigation of the electronic transition spectrum of the WS molecule.

Potential Dependence of Electronic Transition Spectra of Interfacial Ionic Liquids Studied by Newly Developed Electrochemical Attenuated Total Reflectance Spectroscopy.

Recently, ionic liquids at the electrode/ionic liquid interface have been intensively studied because they are promising as novel alternatives to traditional electrolyte solutions that are both safe and functional. In this study, we constructed an attenuated total-reflectance spectroscopic system that operates under electrochemical conditions in order to investigate the electronic states of ionic liquids near the electrode surface. Upon application of voltage to an ionic liquid consisting of imidazolium cations and iodide anions, electronic transition spectra in the 150-450 nm range varied. In particular, absorbance due to charge transfer from the anion to the cation drastically increased at positive potentials. The extent of spectral change and contact area between the electrode and the ionic liquid were positively correlated, and thus spectral variations reflected the behavior of the interfacial ionic liquid on the electrode. In addition to potential dependence, time dependence and hysteresis were also investigated. The newly developed system can be applied not only for ionic liquids but foreseeably also for various electrochemical materials such as organic semiconductors.

<i>Ab initio</i> calculation of electronic state structure of TiAl

The potential energy curves (PECs) of the low-lying electronic states of TiAl are calculated with the complete active space self-consistent field (CASSCF) method combined with the <i>N</i>-electron valence perturbation theory (NEVPT2) approximation. The complete active space is mainly composed of the (3s<sup>2</sup>3p<sup>1</sup>) valence orbital of Al and (3d<sup>2</sup>4s<sup>2</sup>) valence orbital of Ti. Moreover, the valence splitting all-electron basis set def2-<i>n</i>ZVPP (<i>n</i> = T, Q) proposed by Karlsruhe group is used in the calculation. On the basis of confirming that the ground state of TiAl is a quadruple state, the PECs of the ground state and the lowest two excited states of TiAl are obtained in a range of nuclear distance <i>R</i> of 0.200–0.500 nm, and the electronic states are identified. It is found that there is a “break” of the electronic structure near <i>R</i> = 0.255 nm. In the <i>R</i> > 0.255 nm region, the ground state and the two excited states are X<sup>4</sup>Δ, A<sup>4</sup>Π and B<sup>4</sup>Γ respectively; in the <i>R</i> < 0.255 nm region, the ground state is still X<sup>4</sup>Δ, but the two excited states become A'<sup>4</sup>Φ and B'<sup>4</sup>Π, and the degeneracy of the excited state tends to be eliminated. Based on the PECs of TiAl obtained by the dynamic correlation correction with NEVPT2, the characteristic parameters of three low-lying quadruple electronic states (such as equilibrium nuclear distance, binding energy, adiabatic excitation energy) and transition dipole moment, are obtained, and these parameters are used to explain the reason why the electronic transition spectrum of TiAl is not observed experimentally. The characteristic of “break” in the electronic state structure also provides a meaningful reference for analyzing and understanding the brittleness of TiAl alloy at room temperature.

Electronic transitions of tantalum monofluoride

The electronic transition spectrum of the tantalum monofluoride (TaF) molecule in the spectral region between 448 and 560 nm has been studied using the technique of laser-ablation/reaction free jet expansion and laser induced fluorescence spectroscopy. The TaF molecule was produced by reacting laser-ablated tantalum atoms with sulfur hexafluoride gas seeded in argon. Twenty-two vibrational bands with resolved rotational structure have been recorded and analyzed, which were organized into seven electronic transitions. The X3Σ−(0+) state has been identified to be the ground state and the determined equilibrium bond length, re, and vibrational frequency, ωe, are 1.8184 Å and 700.1 cm−1, respectively. The low-lying Λ-S states and Ω sub-states of TaF were also theoretically studied at the MRCISD+Q level of theory with spin-orbit coupling. The Ω = 0+ and 2 sub-states from the Σ−3 and Φ3 state have been found to be the ground and the first excited states, respectively, which agrees well with our experimental determinations. This work represents the first experimental investigation of the molecular structure of the TaF molecule.

A theoretical and optical spectroscopic study of the mechanism of a tautomeric transformation in the 7-azaindole dimer and the 7-azaindole complex with a water molecule

Electronic, vibrational, and electronic vibrational spectra of the 7-azaindole dimer, the 7-azaindole complex with a water molecule, and their tautomers are calculated. Transition states are considered based on the analysis of frequencies and shapes of low-frequency vibrations and the Mulliken charge redistribution. The performed quantum chemical calculation of chemical reactions enabled the determination of the structure of transition states and proton transfer conditions. It is shown that in the 7-AzI dimer the proton transfer has a character consistent with the formation of a zwitterionic form. The structure of excited states is calculated and the fluorescence spectra of the first electronic transitions that can be used as a criterion of the formation of 7-AzI tautomers as a result of chemical reactions proceeding through a proton transfer in the 7-azaindole dimer and the 7-azaindole complex with a water molecule, are interpreted.

Electronic transitions of platinum monofluoride

Electronic transition spectrum of platinum monofluoride (PtF) between 431 and 560nm has been investigated using the technique of laser vaporization/reaction with free jet expansion and laser induced fluorescence spectroscopy. Eight vibrational bands had been observed but only six of them were analyzed, they were grouped into four electronic transitions: the [18.9]2Π3/2 – X2Π3/2, the [18.9]2Π3/2 – [0.04]2Δ5/2, the [19.9]2Δ5/2 – X2Π3/2 and the [23.2]2Δ5/2 – X2Π3/2 transitions. Accurate molecular constants have been determined for the [23.2]2Δ5/2, [19.9]2Δ5/2, [18.9]2Π3/2 and [0.04]2Δ5/2 electronic states. The agreement between experimental determined molecular constants and those from ab initio calculations incorporating the spin-orbit coupling is generally good.