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We present a numerically exact approach for evaluating vibrationally resolved electronic spectra at finite temperatures using the coherence thermofield dynamics. In this method, which avoids implementing an algorithm for solving the von Neumann equation for coherence, the thermal vibrational ensemble is first mapped to a pure-state wavepacket in an augmented space, and this wavepacket is then propagated by solving the standard, zero-temperature Schrödinger equation with the split-operator Fourier method. We show that the finite-temperature spectra obtained with the coherence thermofield dynamics in a Morse potential agree exactly with those computed by Boltzmann-averaging the spectra of individual vibrational levels. Because the split-operator thermofield dynamics on a full tensor-product grid is restricted to low-dimensional systems, we briefly discuss how the accessible dimensionality can be increased by various techniques developed for the zero-temperature split-operator Fourier method. [ABSTRACT FROM AUTHOR]

The electronic and vibrational spectra of the meso-tetrakis(4-sulfonatophenyl)-porphyrins (TSPP) have been studied computationally using the PFD-3B functional with time-dependent density functional theory for the excited states. The calculated UV-vis absorption and emission spectra in aqueous solution are in excellent agreement with the experimental measurements of both H2TSPP−4 (monomer) at high pH and H4TSPP−2 (forming J-aggregate) at low pH. Moreover, our calculations reveal an infrared absorption at 1900 cm−1 in the singlet and triplet excited states that is absent in the ground state, which is chosen as a probe for transient IR absorption spectroscopy to investigate the vibrational dynamics of the excited state. Specifically, the S2 to S1 excited state internal conversion process time, the S1 state vibrational relaxation time, and the lifetime of the S1 excited electronic state are all quantitatively deduced. [ABSTRACT FROM AUTHOR]

We report here investigations on conformational effects in the vibrational and electronic spectra of the propionaldehyde (propanal) molecule using FTIR (600–3200 cm−1) and vacuum ultraviolet (VUV) synchrotron radiation photoabsorption (52 500–85 000 cm−1) spectroscopy respectively. Detailed theoretical calculations (using DFT and TDDFT methodologies) on ground and excited states of the cis and gauche conformers of propanal are performed; a comprehensive spectral analysis of the IR and VUV spectra is presented. A reinvestigation of the IR spectrum reveals several new bands assigned to the gauche conformer based on theoretical calculations. The VUV spectrum exhibits rich Rydberg series structure assigned to ns, np and nd series converging to the first ionization potentials of the two conformers. Earlier assignments of the 3s cis and gauche origins are revised in addition to extending Rydberg series analysis to several higher members. Vibronic bands accompanying the 3s, 4s and 4p Rydberg states are assigned using estimated vibrational frequencies of cis and gauche conformers in the cationic ground state. Simulated potential energy curves of the first few excited states (singlets and triplets) of cis and gauche conformers of propanal help in gaining insights into photodissociation mechanisms and possible conformational effects therein. [ABSTRACT FROM AUTHOR]

This study focuses on the properties and intermolecular interactions of nitrosamine oligomers, which are important in both semiconductor manufacturing and nuclear waste management. The study explores various configurations of nitrosamine oligomers, ranging from monomers to pentamers in linear, ladder, and cyclic clusters, with the finding that dimer cyclic forms and hexamers and above are unstable. Many‐body analysis revealed that two‐body interaction energies made remarkable contributions to the binding energy, while the sum of 3‐, 4‐, and 5‐body energy contributed less, indicating the decrease in stability of nitrosamine from dimer to pentamer clusters. Using advanced computational techniques, such as dispersion‐corrected B3LYP‐D3 and TD‐DFT, the study investigates the vibrational modes and electronic absorption spectra of nitrosamine oligomers. The results reveal that different configurations can significantly affect the vibrational modes and electronic properties of nitrosamine oligomers. The NH2 symmetric and asymmetric modes were particularly intense in various forms of nitrosamine oligomers. The wavelengths of electronic transition, oscillator strength, and HOMO to LUMO gap were reported. Additionally, the study reports on nitrosamine oligomers' hydrogen‐bonded cooperativity and binding energy contributions. Overall, these findings offer valuable insights into the stability and properties of nitrosamine oligomers, with potential applications in materials science and chemical engineering. [ABSTRACT FROM AUTHOR]

Following up on our previous work on vibrationally resolved electronic absorption spectra including the effect of vibrational pre-excitation [von Cosel et al., J. Chem. Phys. 147, 164116 (2017)], we present a combined theoretical and experimental study of two-photon-induced vibronic transitions in polyatomic molecules that are probed in the VIbrationally Promoted Electronic Resonance experiment using two-photon excitation (2P-VIPER). In order to compute vibronic spectra, we employ time-independent and time-dependent methods based on the evaluation of Franck–Condon overlap integrals and Fourier transformations of time-domain correlation functions, respectively. The time-independent approach uses a generalized version of the FCclasses method, while the time-dependent approach relies on the analytical evaluation of Gaussian moments within the harmonic approximation, including Duschinsky rotation effects. For the Coumarin 6 dye, two-dimensional 2P-VIPER experiments involving excitation to the lowest-lying singlet excited state (S1) are presented and compared with corresponding one-photon VIPER spectra. In both cases, coumarin ring modes and a CO stretch mode show VIPER activity, albeit with different relative intensities. Selective pre-excitation of these modes leads to a pronounced redshift of the low-frequency edge of the electronic absorption spectrum, which is a prerequisite for the VIPER experiment. Theoretical analysis underscores the role of interference between Franck–Condon and Herzberg–Teller effects in the two-photon experiment, which is at the root of the observed intensity distribution. [ABSTRACT FROM AUTHOR]

Phenol-benzimidazole and phenol-pyridine dyad complexes have served as popular model systems for the study of proton-coupled electron transfer (PCET) kinetics in solution-phase experiments. Interpretation of measured PCET rates in terms of key structural parameters, such as the H-bond donor–acceptor distance, however, remains challenging. Herein, we report vibrational spectra in the electronic ground state for a series of phenol-benzimidazole and phenol-pyridine complexes isolated and cryogenically cooled in an ion trap. The four models studied each display highly red-shifted and broadened OH stretching transitions that arise from strong H-bonding interactions between the phenol OH group and the basic N site on benzimidazole/pyridine rings. The OH stretch transition in each model displays relatively strong absorption onsets near 2500 cm−1 with broad shoulders that extend asymmetrically to higher frequencies over hundreds of wavenumbers. In contrast, the deuterated isotopologues yield much weaker OD stretch transitions that appear symmetrically broadened. The spectral breadth and shape of the OD stretch transitions are ascribed to variations in OD stretch frequencies that arise from zero-point distributions in the proton donor–acceptor low-frequency soft mode vibration. The asymmetric structure of the OH stretch transitions is attributed to a set of combination bands between the OH stretch and a series of low-frequency H-bond soft modes. The spectra and modeling highlight the importance of OH stretch-soft mode couplings, which are thought to play important roles in PCET and proton transfer dynamics. [ABSTRACT FROM AUTHOR]

Two-dimensional electronic-vibrational (2DEV) spectra have the capacity to probe electron–nuclear interactions in molecules by measuring correlations between initial electronic excitations and vibrational transitions at a later time. The trajectory-based semiclassical optimized mean trajectory approach is applied to compute 2DEV spectra for a system with excitonically coupled electronic excited states vibronically coupled to a chromophore vibration. The chromophore mode is in turn coupled to a bath, inducing redistribution of vibrational populations. The lineshapes and delay-time dynamics of the resulting spectra compare well with benchmark calculations, both at the level of the observable and with respect to contributions from distinct spectroscopic processes. [ABSTRACT FROM AUTHOR]

From paddlewheel starting reactants Ru2(R′CO2)4+, a family of edge-sharing bi-octahedral (ESBO) diruthenium(III , III) compounds has been prepared, formulated as Ru2(μ-O2CR′)2(μ-OR)2(η-L)2 (1–10) [R′ = CH3, R = CH3, L = acac (1), tfac (2); R′ = CH3, R = CH2CH3, L = hfac (3); R′ = CH2CH3, R = CH3, L = acac (4), tfac (5); R′ = CH2CH3, R = CH2CH3, L = hfac (6); R′ = CH2Cl, R = CH3, L = tfac (7); R′ = CH2Cl, R = CH2CH3, L = hfac (8); R′ = C6H5, R = CH3, L = tfac (9); and R′ = H, R = CH3, L = acac (10); here, acac, tfac and hfac represent acetylacetone, trifluoroacetylacetone and hexafluoroacetylacetone, respectively]. Compounds 1–10 have a similar ESBO coordination geometry of the Ru(μ-O2CR′)2(μ-OR)2Ru core with a Ru–Ru center chelated and bridged by two μ-O2CR′ and two μ-OR in a trans manner, and each Ru center is also coordinated with a η2-L bidentate ligand. The Ru–Ru distances fall in the range of 2.4560(9)–2.4771(4) Å. The investigation of the electronic spectra and vibrational frequencies as well as theoretical studies with density functional theory (DFT) reveal that compounds 1–10 are ESBO bimetallic species of d5–d5 valence electron counts showing a σ2π2δ2δ*2π*2 electronic configuration. Varying –CH3 to –CF3 groups on the η2-L bidentate ligands coordinating to the Ru(μ-O2CR′)2(μ-OR)2Ru core, and according to Raman spectrum measurements combined with theoretical calculations, the intense bands of compounds 1–10 appearing at ∼345 cm−1 in the small-wavenumber region can be assigned to the stretching of the Ru–Ru single bond. [ABSTRACT FROM AUTHOR]

VO and VO2 vanadyl groups with short (typically 1.57–1.68 Å), essentially covalent, V—O bonds are common for V4+‐bearing oxysalts with [5]‐ and [6]‐coordinated vanadium. There is a clear negative correlation between vanadyl bond lengths and wavenumbers of the bands of V—O stretching vibrations in infrared spectra (in the range 1000–880 cm−1). Optical, structural and chemical data for vanadyl minerals are used to calculate Gladstone–Dale compatibility coefficients. Gladstone–Dale compatibility indices of minerals containing vanadyl bonds are compared with total electronic polarizabilities of V4+. Unlike compounds of [5]‐coordinated Ti4+, for most minerals with V4+=O (vanadyl) bonds there is good agreement between measured refractive indices and those calculated based on the polarizability concept. [ABSTRACT FROM AUTHOR]

UV-induced processes are commonly studied in acetylacetone analogues. In this contribution, we revisit the existing work on the photoisomerization process in some of the fluorinated analogues of acetylacetone, i.e., trifluoroacetylacetone (F3-acac) and hexafluoroacetylacetone (F6-acac). We performed selective UV laser excitation of these molecules trapped in soft cryogenic matrices, namely neon and para-hydrogen, and probed by vibrational spectroscopy. Clear spectroscopy of 3 isomers of F6-acac and 6 isomers of F3-acac is obtained, including the first characterization of a second open enol isomer of hexafluoroacetylacetone. In addition, we present the electronic absorption spectra of both molecules in cryogenic matrices before and after specific UV irradiations, giving new data on the electronic transitions of photoproducts. Vibrational and electronic experimental results are analyzed and discussed within comparisons with DFT and TD-DFT calculations. Our findings contribute to a deeper understanding of the photoisomerization process in these molecules after electronic excitation in gas and condensed phase. [ABSTRACT FROM AUTHOR]

Laser-induced fluorescence/dispersed fluorescence (LIF/DF) and cavity ring-down spectra of the A 1 ̃ 2 A ′ ′ / A 2 ̃ 2 A ′ − X ̃ 2 A ′ electronic transition of the calcium ethoxide (CaOC2H5) radical have been obtained under jet-cooled conditions. An essentially constant A ̃ 2 − A ̃ 1 energy separation for different vibronic levels is observed in the LIF spectrum, which is attributed to both the spin–orbit (SO) interaction and non-relativistic effects. Electronic transition energies, vibrational frequencies, and spin–vibrational eigenfunctions calculated using the coupled-cluster method, along with results from previous complete active space self-consistent field calculations, have been used to predict the vibronic energy level structure and simulate the recorded LIF/DF spectra. Although the vibrational frequencies and Franck–Condon (FC) factors calculated under the Born–Oppenheimer approximation and the harmonic oscillator approximation reproduce the dominant spectral features well, the inclusion of the pseudo-Jahn–Teller (pJT) and SO interactions, especially those between the A 1 ̃ 2 A ″ / A 2 ̃ 2 A ′ and the B ̃ 2 A ′ states, induces additional vibronic transitions and significantly improves the accuracy of the spectral simulations. Notably, the spin–vibronic interactions couple vibronic levels and alter transition intensities. The calculated FC matrix for the A 1 ̃ 2 A ′ ′ / A 2 ̃ 2 A ′ − X ̃ 2 A ′ transition contains a number of off-diagonal matrix elements that connect the vibrational ground levels to the levels of the ν8 (CO stretch), ν11 (OCC bending), ν12 (CaO stretch), ν13 (in-plane CaOC bending), and ν21 (out-of-plane CaOC bending) modes, which are used for vibrational assignments. Transitions to the ν21(a″) levels are allowed due to the pJT effect. Furthermore, when LIF transitions to the A ̃ -state levels of the CaOC-bending modes, ν13 and ν21, are pumped, A 1 ̃ 2 A ′ ′ / A 2 ̃ 2 A ′ → X ̃ 2 A ′ transitions to the combination levels of these two modes with the ν8, ν11, and ν12 modes are also observed in the DF spectra due to the Duschinsky mixing. Implications of the present spectroscopic investigation to laser cooling of asymmetric-top molecules are discussed. [ABSTRACT FROM AUTHOR]

The electronic spectrum associated with the S1 ← S0 ( A ̃ 1 A 2 ← X ̃ 1 A 1 ) one-photon transition of jet-cooled N-methylpyrrole is investigated using laser-induced fluorescence (LIF) and (1 + 1) resonance-enhanced multiphoton ionization (REMPI) spectroscopy; in addition, the (2 + 2) REMPI spectrum is considered. Assignment of the observed bands is achieved using a combination of dispersed fluorescence (DF), two-dimensional LIF (2D-LIF), zero-electron-kinetic energy (ZEKE) spectroscopy, and quantum chemical calculations. The spectroscopic studies project the levels of the S1 state onto those of either the S0 state, in DF and 2D-LIF spectroscopy, or the ground state cation (D0+) state, in ZEKE spectroscopy. The assignments of the spectra provide information on the vibrational, vibration-torsion (vibtor), and torsional levels in those states and those of the S1 levels. The spectra are indicative of vibronic (including torsional) interactions between the S1 state and other excited electronic states, deduced both in terms of the vibrational activity observed and shifts from expected vibrational wavenumbers in the S1 state, attributed to the resulting altered shape of the S1 surface. Many of the ZEKE spectra are consistent with the largely Rydberg nature of the S1 state near the Franck–Condon region; however, there is also some activity that is less straightforward to explain. Comments are made regarding the photodynamics of the S1 state. [ABSTRACT FROM AUTHOR]

Two-dimensional vibrational–electronic (2DVE) spectra probe the effects on vibronic spectra of initial vibrational excitation in an electronic ground state. The optimized mean trajectory (OMT) approximation is a semiclassical method for computing nonlinear spectra from response functions. Ensembles of classical trajectories are subject to semiclassical quantization conditions, with the radiation–matter interaction inducing discontinuous transitions. This approach has been previously applied to two-dimensional infrared and electronic spectra and is extended here to 2DVE spectra. For a system including excitonic coupling, vibronic coupling, and interaction of a chromophore vibration with a resonant environment, the OMT method is shown to well approximate exact quantum dynamics. [ABSTRACT FROM AUTHOR]

We present an efficient method to simulate two-dimensional (2D) electronic spectra of condensed-phase systems with an emphasis on treating quantum nuclear wave packet dynamics explicitly. To this end, we combine a quantum Langevin equation (QLE) approach for dissipation and a perturbative scheme to calculate three-pulse photon-echo polarizations based on wave packet dynamics under the influence of external fields. The proposed dynamical approach provides a consistent description of nuclear quantum dynamics, pulse-overlap effects, and vibrational relaxation, enabling simulations of 2D electronic spectra with explicit and non-perturbative treatment of coupled electronic–nuclear dynamics. We apply the method to simulate 2D electronic spectra of a displaced-oscillator model in the condensed phase and discuss the spectral and temporal evolutions of 2D signals. Our results show that the proposed QLE approach is capable of describing vibrational relaxation, decoherence, and vibrational coherence transfer, as well as their manifestations in spectroscopic signals. Furthermore, vibrational quantum beats specific for excited-state vs ground-state nuclear wave packet dynamics can also be identified. We anticipate that this method will provide a useful tool to conduct theoretical studies of 2D spectroscopy for strong vibronically coupled systems and to elucidate intricate vibronic couplings in complex molecular systems. [ABSTRACT FROM AUTHOR]

The present work reports the vibrational spectroscopic signature, thermodynamics, and natural bond orbital analysis (NBO) of 4-Cyano-4-pentylbiphenyl (5CB) and 4-Cyano-4'-hexyl diphenyl (6CB) liquid crystals. The optimization of both compounds (5CB and 6CB) has been performed at DFT/B3LYP/6-31++G(d, p) level of theory. Most of the vibrational modes have wavenumbers in the expected range. The comparison of vibrational frequencies of both compounds has been made. Subsequently, the different thermodynamical parameters and electronic properties have been calculated and discussed in detail. The NBO analysis has been performed to check the stability of the electronic structures. The UV visible, HOMO- LUMO, MEP, and charge analysis has been performed. Moreover, the strong electronic transition from HOMO to LUMO (97% of MO contribution) has been predicted for 5CB and 6CB at 289 nm with oscillator strengths of 0.7242 and 0.7286, respectively. The MEP plots of both 5CB and 6CB are almost the same and show that strong electrophilic substitution would take place near the N atom attached to the CN group. The energy gap of 5CB and 6CB compounds is found to be 4.65eV. Molecules with large energy gaps are less polarizable and are termed as hard molecules, having low chemical reactivity and high kinetic stability. [ABSTRACT FROM AUTHOR]

In the present paper, we study the interaction of associates (dimers and trimers) of 4-n-pentyl-4΄-cyanobiphenyl (5CB) with 1, 2-Diamino-4-nitrobenzene and N, N-Dimethyl-4-nitrosoaniline dye molecules. The structures of the intermolecular complexes were studied using hybrid functionals of the DFT method M06 and B3LYP with the 6–31 + G (d) basis set. The intermolecular binding energy of dyes with associates depends on the structure of the complexes and is about 5 kcal/mol. Vibrational spectra were calculated for all intermolecular systems. The electronic absorption spectra of dyes are sensitive to the structure of the mesophase. The pattern of the spectrum changes depending on the structure of the complex of the dimer or trimer with the dye molecule. The long-wavelength transition bands are characterized by shifts that are bathochromic for 1, 2-Diamino-4-nitrobenzene and hypsochromic for N, N-Dimethyl-4-nitrosoaniline. [ABSTRACT FROM AUTHOR]

The B ̃ 1 A 1 ← X ̃ 1 A 1 absorption spectra of propargyl cations H2C3H+ and D2C3D+ were simulated by an efficient two-dimensional (2D) quantum model, which includes the C—C stretch (v5) and the C≡C stretch (v3) vibrational modes. The choice of two modes was based on a scheme that can identify the active modes quantitively by examining the normal coordinate displacements (∆Q) directly based on the ab initio equilibrium geometries and frequencies of the X ̃ 1 A 1 and B ̃ 1 A 1 states of H2C3H+. The spectrum calculated by the 2D model was found to be very close to those calculated by all the higher three-dimensional (3D) quantum models (including v5, v3, and another one in 12 modes of H2C3H+), which validates the 2D model. The calculated B ̃ 1 A 1 ← X ̃ 1 A 1 absorption spectra of both H2C3H+ and D2C3D+ are in fairly good agreement with experimental results. [ABSTRACT FROM AUTHOR]

Phenol derivatives are interesting molecules for theoretical studies due to their relatively small size and similarity to organic species. 2,6-dibromo-4-nitrophenol was investigated by using density functional theory (DFT). XRD data and optimized DFT studies are found to be in good correspondence with each other. Analysis of title compound was obtained by B3LYP/6-31 + G(d,p) level of theory to explain the vertical transactions. Calculated FT-IR and FT-Raman results are found to be in good agreement with experimental FT-IR and FT-Raman findings. Natural bond theory (NBO) study was also performed using B3LYP/6-31 + G(d,p) method. Correlations between the proton and carbon-13 experimental chemical shifts and the GIAO NMR calculations are in good agreement and these values have been used for the definitive signal assignments to the corresponding structures. Electronic absorption spectra of DBNP has been calculated by using CIS-DFT method based on the B3LYP/6-311++G (d,p) level of the optimized structure in gas phase. [ABSTRACT FROM AUTHOR]

From the last few years mode of interactions between drugs and DNA is an attractive research area as it bridges chemistry, molecular biology and medicinal science. Interactions between small heterocyclic molecules and human DNA is a noteworthy feature in pharmacology for investigation of drugs mechanism and designing of more effective and target specific drugs with fewer side effects. The present research work focuses on the theoretical investigations of 3-benzoyl-4-hydroxy-2-methyl-2H-1, 2-benzothiazine (SASA) by using Gaussian (16 W) software to predict optimized geometry, HOMO–LUMO gap, bond length, bond angle, dihedral angle, electronic and vibrational spectra. Possible reaction site observed in SASA was C7, C9 and C18 as these atoms show maximum charge density. Later the interactions of SASA with human DNA was explored spectroscopic investigations and viscometric investigations at physiological buffers of pH of 4.7 (stomach pH) and 7.4 (blood pH) respectively. Maximum absorbance between SASA-DNA complex was observed in buffer solution of pH 3.4 at wavelength of 370 nm, whereas at 7.4 has maximim absorbance between. Spectroscopic results reflects the bathochromic and hyperchromic shift succeeding the addition of human DNA. During viscosity measurement, intercalation and electrostatic mode of interaction were detected at low and high concentration of drug in solution respectively. Increase in the value of rate constant was observed with the increase in concentration of drug. Larger values of rate constant were observed at pH 7.4 in comparison to pH 3.5. Rate constant, thermodynamic parameters and viscometric analysis prefers the intake of SASA via blood. [ABSTRACT FROM AUTHOR]

In this work, we studied aqueous solutions of monoethanolamine (MEA), which are widely used to remove CO2 from flue and oil gases. This study combined experimental and theoretical methods of vibrational spectroscopy, using high-temperature infrared spectroscopy, quantum-chemical calculations of theoretical vibrational spectra, and structural electronic and energy characteristics of model structures. MEA has a propensity to form associations between various compositions and structures with water molecules, as well as those composed solely of water molecules. The structural and energy characteristics of such associates were analyzed in terms of their ability to interact and retain carbon dioxide. The influence of elevated temperatures and concentration of aqueous MEA solution on change in the structure of associates has also been investigated. An analysis of theoretical and experimental vibrational spectra allowed us to examine the IR spectra of MEA solutions, and identify the bands responsible for the formation of associates that would sorb CO2 well, but would delay its desorption from the solution. [ABSTRACT FROM AUTHOR]

Theoretical investigations of three pharmaceutically active pyrone derivatives, (E)-4-fluoro-N'-((4-oxo-4H-chromen-3-yl)methylene)benzohydrazide (FMB), (E)-3-((2-(5-fluoro-2-methylphenyl)hydrazono)methyl)-4H-chromen-4-one (MHC) and (E)-3-((2-(2-trifluoromethyl)phenyl)hydrazono)methyl)-4H-chromen-4-one (TPM) are reported. Molecular geometries, vibrational spectra, molecular electrostatic potential, and electronic properties were investigated using density functional theory. The frontier orbitals analysis gives charge transfer within the pyrones. In order to perform a better description of the FMOs the density of states was determined. The molecular electrostatic potential maps were calculated to provide information on the chemical reactivity of the molecule and also to describe the intermolecular interactions. The descriptors are compared with that of 4-pyrone and chromen-4-one molecules. All these studies including docking studies help a lot in determining the biological activities of pyrone derivatives. Activities of pyrone derivatives are compared with 5-fluorouracil and azathioprine (anti-tumor, anti-proliferative standards) and were found to be higher than reference ones. [ABSTRACT FROM AUTHOR]

Quantum chemical calculations have been carried out to explore structural and spectroscopic properties of some derivatives of N-iso-butyl, S-2-nitro-1-phenylethyl dithiocarbamate molecule in neutral and cationic forms. Electron-releasing groups (Me, OH and OMe) are considered to explore their effect on geometrical parameters, vibrational spectra and electronic properties of N-iso-butyl, S-2-nitro-1-phenylethyl dithiocarbamate. All the computations were performed at DFT/B3LYP level of Gaussian09 suite. The Raman spectra at different laser exciting frequencies are presented. The potential energy distributions of the considered derivatives were calculated by using the normal coordinate analysis method. The NBO calculations were performed to study the donor-acceptor interactions, HOMO-LUMO, electronic structure and hyper-conjugative interaction energies. The vibrational contribution of various thermodynamical parameters, viz, entropy, specific heat and free energy have also been presented and discussed in detail. Moreover, we have also explored the effect of temperature at specific heat and partition function of these molecules. Molecular docking studies have been performed to understand the nature of the interactions and the probable binding sites of NSD, NSD-Me, NSD-OH and NSD-OMe molecules in the active pockets of the 2KCE receptor. [ABSTRACT FROM AUTHOR]

Combined with mass spectrometry, ion spectroscopy can obtain a spectrum of the target ion by measuring its intensity change, which is induced by laser strength and wavelength. It integrates the high sensitivity of mass spectrometry and the structural specificity of spectroscopy, and thus proves to be very useful in structure characterization of complex biomolecules, such as proteins, peptides, glycans, oligonucleotides, etc. However, the electronic or vibrational spectra becomes too complex to be resolved when analyzing isomeric ions. Ion mobility spectrometry (IMS) allows ionized molecules to be separated on the basis of mobilities in the gas phase, and its coupling with electrospray and MALDI ion sources opens up possibilities for structural studies of a wide range of biomolecules in gas-phase. Ion mobility spectrometry coupled with mass spectrometry has seen spectacular growth for the last two decades. The introduction of ion mobility to ion spectroscopy has been of growing attention in recent years. While IMS can be used as an isomer filter to reduce spectral congestion of ions, highly resolved ion spectra facilitates the identification of the isomer peaks separated by IMS. Taken together, spectra and collision cross section (CCS) measurements on the same system prove to be rather useful for structural analysis and provide clearer spectroscopic fingerprint to isomers. Therefore, this paper briefly summarized advances in ion spectroscopy research based on ion mobility-mass spectrometry technology, introduced representative researches, and prospected possible development in multi-dimensional structural mass spectrometry. [ABSTRACT FROM AUTHOR]

Electronic and geometric structures of metal-free, Al, Ga and In complexes with tetrapyrazinoporphyrazine (TPyzPA) and octachlorotetrapyrazinoporphyrazine (TPyzPACl8) were investigated by density functional theory (DFT) calculations and compared in order to study the effect of chlorination on the structure and properties of these macrocycles. The nature of the bonds between metal atoms and nitrogen atoms was described using the NBO-analysis. Simulation and interpretation of electronic spectra were performed with the use of time-dependent density functional theory (TDDFT). A description of calculated IR spectra was carried out based on the analysis of the distribution of the potential energy of normal vibrational coordinates. [ABSTRACT FROM AUTHOR]

The turn of this century has undoubtedly brought in tremendous interest in the development of organic electronic and photonic devices. As an aid of understanding the physics behind the device mechanism, various experimental tools are innovated and applied. Herein, various nonlinear optical techniques that are employed towards characterization of these organic material-based devices are reviewed. We describe experimental techniques based on second-harmonic generation (SHG) and sum-frequency generation (SFG) and review some potential applications that basically probe the electric field distribution in the bulk and at interfaces of the electronic and photonic devices. SFG carries information about vibrational spectrum of molecules at the surface, and further analysis of that provides in-depth understanding about their chemical structure and interactions, whereas SHG is sensitive to the electronic spectrum of the interfacial molecules. Thus, a comprehensive study using both of these techniques allows a more complete interfacial characterization of organic devices. Most applications use electric-field-induced SFG (or SHG) to examine the electric field orientation and spatial distribution. Further, time-resolved techniques, such as transient SFG or SHG microscopy, allow direct investigation of the charge carrier motion inside the organic layers under device operation, by probing the change of transient electric field. At the end, we briefly discuss possible directions for further research with these techniques. [ABSTRACT FROM AUTHOR]

A combination of natural betanidin (Bd) or decarboxylated betanidin (dBd) dyes possessing efficient carboxylic anchoring groups with synthetic dye L0 containing strong electron donor triphenylamine moiety has been engineered on purpose to improve the dye's optoelectronic properties for DSSCs application. Novel complex D–π–A organic dyes, L0–Bd and L0–dBd with structural isomers, have been designed via esterification reactions. The DFT/B3LYP5/6-31G(d,p) approach is used in computations of geometry, vibrational spectra and thermodynamic characteristics of complexes; the TD–DFT method – for optoelectronic properties. Due to the combination, broader coverage of the solar spectrum with greater light-harvesting efficiency of the designed sensitisers was achieved compared to individual dyes. The dye complexes′ attachment to the TiO2 cluster was simulated in terms of the different possible adsorption modes; binding energies and electronic spectra of the dye@TiO2 systems were computed, and electron density distributions over frontier molecular orbitals were analysed. [ABSTRACT FROM AUTHOR]

This perspective gives an overview of the action spectroscopy methods for measurements of electronic, vibrational, and rotational spectra of mass‐selected ions in the gas phase. We classify and give a short overview of the existing experimental approaches in this field. There is currently a plethora of names used for, essentially, the same techniques. Hence within this overview, we scrutinized the notations and suggested terms to be generally used. The selection was either driven by making the name unique and straightforward or the term being the most broadly used one. We believe that a simplification and a unification of the notation in ion spectroscopy can make this field better accessible for experts outside the mass spectrometry community where the applications of gas‐phase action ion spectroscopy can make a large impact. [ABSTRACT FROM AUTHOR]

Vibrationally resolved electronic absorption spectra including the effect of vibrational pre-excitation are computed in order to interpret and predict vibronic transitions that are probed in the Vibrationally Promoted Electronic Resonance (VIPER) experiment [L. J. G. W. van Wilderen et al., Angew. Chem., Int. Ed. 53, 2667 (2014)]. To this end, we employ time-independent and time-dependent methods based on the evaluation of Franck-Condon overlap integrals and Fourier transformation of timedomain wavepacket autocorrelation functions, respectively. The time-independent approach uses a generalized version of the FC-classes method [F. Santoro et al., J. Chem. Phys. 126, 084509 (2007)]. In the time-dependent approach, autocorrelation functions are obtained by wavepacket propagation and by the evaluation of analytic expressions, within the harmonic approximation including Duschinsky rotation effects. For several medium-sized polyatomic systems, it is shown that selective pre-excitation of particular vibrational modes leads to a redshift of the low-frequency edge of the electronic absorption spectrum, which is a prerequisite for the VIPER experiment. This effect is typically most pronounced upon excitation of modes that are significantly displaced during the electronic transition, such as ring distortion modes within an aromatic π-system. Theoretical predictions as to which modes show the strongest VIPER effect are found to be in excellent agreement with experiment. [ABSTRACT FROM AUTHOR]

With the ever-increasing detection of sulfur-bearing molecules and the high abundance and refractory nature of aluminum, the [Al, S, O2] isomers may play an important role in the gas-phase chemistry of circumstellar envelopes and the chemistry on the surface of dust grains. High-level theoretical exploration of the [Al, S, O2] molecular system yielded five isomers, and predictions of their rotational, vibrational, and electronic spectroscopic properties are provided to inform experimental and observational searches. Cis-AlOSO and diamond isomers are isoenergetic and connected via a very small (∼1 kcal molâˆ'1) transition-state barrier. These isomers may act as intermediates along the chemical pathway between Al + SO2 and AlO + SO. Other isomers OAlOS and SAlO2 are stable relative to their corresponding dissociation asymptotes. Large permanent dipole moments of 2.521 D (cis-AlOSO), 1.239 D (diamond), and 5.401 D (OAlOS) predict strong rotational transitions and indicate these molecules as prime candidates for experimental study. Due to the low transition-state barrier, mixing of the vibrational levels is anticipated, complicating the vibrational spectrum. Electronic spectroscopy may be used as a means to differentiate between the two isomers. Strong electronic transitions are predicted to occur in the 200â€"300 nm range for cis-AlOSO and diamond. Simulated electronic absorption spectra provide a starting point for experimental characterization and spectral deconvolution of these isomers. [ABSTRACT FROM AUTHOR]

New nitronyl nitroxide radicals, 2-(4′(5′)-methylimidazol-2′-yl)- and 2-(4′(5′)-trifluoromethylimidazol-2′-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-1-oxyl 3-oxide, were synthesized. The molecular and crystal structures of the paramagnetic trifluoromethyl derivative were determined. A previously unknown type of hydrogen bonding of imidazol-2-yl-substituted nitronyl nitroxides to form ribbons was established. Within the ribbons, the molecules face in the same direction, with all oxygen atoms of the paramagnetic moieties being involved in H-bonding. The spectral and electrochemical properties of the radicals were compared. The first quantum chemical calculations of the electronic spectra of nitronyl nitroxide radicals taking account of the vibrational structure were performed. [ABSTRACT FROM AUTHOR]

We considered the recent application of quantum mechanical methods for studying the structure, interaction energies, as well as vibrational and electronic spectra of complexes of 2D nanomaterials (graphene, graphene oxide) with biological molecules. We analyzed how to overcome the main problems arising in computational studies of 2D nanobiohybrids, namely, the large size of systems, the nonuniformity of 2D nanomaterials, the need to use methods that can correctly take into account dispersion interactions. An analysis of the results of quantum mechanical studies, published over the recent decade, showed that the development of theoretical calculation methods and a significant increase in the productivity of computing technology made it possible to calculate not only the structure and interaction energies of nanobiosystems, but also their vibrational and electronic spectra. [ABSTRACT FROM AUTHOR]

The substitutional doping of graphene and related materials with Boron (B) and/or Nitrogen (N) atoms can be effectively used to tailor their properties for specific applications. In this paper, we investigate the energetics, electronic structures and vibrational spectra of substitutional pair-defects in graphene and graphane. The structural distortions in the vicinity of BN pair-defects are small as compared to the distortions in the vicinity of BB or NN pair-defects. The BB (NN) pair-defects in graphene and graphane transform them into p (n) semiconductors. However, the BN pair-defects doped graphene and graphane are intrinsic semiconductors. The Raman and IR spectra of above mentioned pair-defects have unique features, which can be used to identify these defects in graphene as well as graphane structures. [Display omitted] • Substitutional pair-defects doped in graphene and graphane show their signatures in electronic and optical properties. • BB (NN) pair-defects in graphene and graphane transform them into p(n) type semiconductors. • Raman and IR spectra of pair-defects have unique features, which can be used to identify these defects in graphene as well as graphane structures. [ABSTRACT FROM AUTHOR]

[Display omitted] • Structures of cyclic dimers and tetramer of adenine were studied by DFT calculations. • The characteristics of N-H···N interactions were studied by NBO and AIM calculations. • Complete vibrational assignments of cyclic dimers are presented. • Vibronic bands are observed in the electronic spectra. • Different scaled force constants values show the cyclic dimers of adenine. In this work, three different cyclic dimers and a tetramer of adenine taken from the experimental structure determined by X-ray diffraction have been studied by combination of experimental FT-IR, FT-Raman and UV–Visible spectra with hybrid B3LYP/6–311++G** and scaled quantum mechanical force field (SQMFF) calculations in order to perform the complete assignments of bands observed in the vibrational spectra. The characteristics of different N-H···N interactions of those three cyclic structures together with the group of IR bands observed between 2865 and 2599 cm−1 have been elucidated considering the tetrameric structure. The cyclic dimers and the tetramer of adenine confirm that the bands observed between 2865 and 2599 cm−1 are not due to N-H···N interactions but to bands of combination, as was previously suggested. The experimental available deuterated IR and terahertz spectra have allowed the complete assignments of regions of higher and lower wavenumbers. Good correlations were acquired comparing the theoretical IR, Raman and UV spectra of three species and the tetramer with the analogous experimental ones, suggesting the presence of all species in both phases. Vibronic bands are observed in the electronic spectra when adenine concentration is increased in aqueous solution evidencing the presence of monomer, tautomers and dimers, as reported by different studies. Similar characteristics of H bonds interactions are predicted for dimers 1 and 2 but different from the dimer 3, as revealed by using NBO and AIM calculations. Different scaled force constants values were found for the cyclic dimers 1 and 2, as compared to the corresponding to dimer 3. [ABSTRACT FROM AUTHOR]

New spectroscopic parameters have been calculated to aid in the laboratory and observational detection of AlCH, AlCH+, MgCH, MgCH+, and their deuterated analogs. All species exist in linear geometry except for AlCH+, which exhibits a bent structure. Rotational frequencies have been calculated and the transition with maximum intensity is discussed for three temperature regions present in space: 100 K for a central circumstellar envelope (CSE), 30 K for an outer CSE, and 3 K indicative of the interstellar medium. Pertinent frequencies range from 25 to 250 GHz, depending on the species. At 30 K, the most intense transition is expected to be J = 4 → 3 for all species. The vibrational spectrum of each molecule is expected to be complicated due to the flat nature of the potential energy surface along the bending angle and the presence of anharmonic resonances. Deuteration produces a decrease in vibrational frequency, which may be utilized in experiments to confirm detection of these molecules. The electronic absorption spectrum of both AlCH and MgCH is predicted to be congested and broad. Various high-oscillator-strength transitions are predicted. Upon photoexcitation in the 220–300 nm region, facile dissociation on a repulsive excited state along the Al–C coordinate is predicted to be a source of Al in the colder regions of space. Photodissociation of MgCH requires several nonradiative processes that will control the product state distribution of the fragments. [ABSTRACT FROM AUTHOR]

High dilutions (HD) of drugs used in homeopathy are too dilute to contain original drug molecules. Clinical and experimental evidence shows, however, that the HDs produce specific biological effects. Water structures in HDs are thought to be responsible for those effects. In our earlier experimental studies, we defined the water structure in terms of free water molecules (FWM) and the hydrogen bond strength (HBS) of the water hydroxyl in the aqueous ethanol solvent of this preliminary study is to further confirm the components of water structure by electronic (ES) and vibrational spectroscopy (VS). HDs, prepared by serial dilution of a drug followed by succussion, are called potencies. Three common homeopathic drugs, Bryonia alba, Rhus toxicodendron and Thuja occidentalis, and three potencies of each drug were analyzed by ES and VS using appropriate statistics. The results show that the potencies tested differ from each other with respect to FWM and HBS of the water hydroxy!. We conclude that the drugs could modify the water structure in an EtOH water solution, and this modification would continue to exist in HDs beyond the Avogadro number. Original drug molecules influence the HBS in the HDs. [ABSTRACT FROM AUTHOR]

A detailed first principle study on the three thiadiazole containing Schiff base ligands having phenol, chloro and bromo combinations has been carried out [Density functional theory-DFT/B3LYP/6-311 G (d, p)]. The calculated structural properties show close resemblance with the literature data. The vibrational spectra of phenol-substituted molecule is calculated and compared with those obtained with experimental FTIR (Fourier Transform infrared spectroscopy) while for chloro-and bromo-substituted, it is predicted theoretically with vibartional assignments. TDDFT (Time dependent Density Functional Theory) calculations and Natural bond (NBO) analysis of title molecules have been also done with same level of theory. From NBO analysis, the lone pair electron n1 (O21) plays significant role in stabilization of compound A as compared to lone pair electron of n2 (Cl26), n2 (Br26) in B and C respectively. Some biological parameter Log P and Log S (Electro-topological indices) are also calculated (molecular docking calculations) which suggests that the derivatives of the title molecule have good ability to deliver drugs in various diseases. The reactivity of molecules using various descriptors (local) such as Fukui functions, local softness and electrophilicity as well as global i.e., electronegativity, hardness, HOMO (Highest occupied molecular orbital) - LUMO (Lowest unoccupied molecular orbital) gap etc. of the same are calculated and discussed. [ABSTRACT FROM AUTHOR]

The experimental Fourier Transform-Infrared, Raman, and Ultraviolet-Visible spectral data along with the theoretical quantum chemical calculations for phenylenediamine isomers were investigated in detail. Vibrational modes were assigned by potential energy distributions. Energy gap, ionization potential, electron affinity, and electronegativity descriptors were obtained from frontier molecular orbitals. Molecular electrostatic potential surfaces were plotted to estimate chemical reactivity at isomers. It was aimed to determine the isomeric effect on the characterization of molecules by theoretical and experimental analysis. By using DFT/B3LYP method with aug-cc-PVDZ basis set, the structural and spectral properties of the molecule studied were interpreted. [ABSTRACT FROM AUTHOR]

The various tautomers and conformers of SLC-0111, a well-known biologically potent compound, have been investigated using density functional theory (DFT) calculations in the gas phase and aqueous solution. The amide form is found to be the only stable tautomeric form in both the phases, with the trans-cis conformer as the most stable structure in the gas phase and the trans-trans conformer in aqueous solution. The deprotonation of the sulfonamide nitrogen leading to the formation of the SLC-0111 anion occurs at pH > 10. The various intramolecular interactions and reactivity of the molecule have been characterized using natural bond orbital (NBO) analysis and calculation of global reactivity parameters. The effect of the solvent polarity on the energies and nature of the frontier molecular orbitals has been investigated for both the neutral and anionic forms. Further, the electronic spectra and vibrational spectra of both the states have also been computed and the effect of changing solvents on the electronic spectra has been investigated. The calculated nonlinear optical (NLO) properties of the molecule show that the molecule has potential to be featured as an NLO material. [ABSTRACT FROM AUTHOR]

Vibrationally and rotationally resolved electronic spectra of diphenylmethane-d5 (DPM-d5) are reported in the isolated-molecule environment of a supersonic expansion. While small, the asymmetry induced by deuteration of one of the aromatic rings is sufficient to cause several important effects that change the principle mechanism of vibronic coupling between the close-lying S1 and S2 states, and spectroscopic signatures such coupling produces. The splitting between S1 and S2 origins is 186 cm-1, about 50% greater than its value in DPM-d0 (123 cm-1), and an amount sufficient to bring the S2 zero-point level into near-resonance with the v = 1 level in the S1 state of a low-frequency phenyl flapping mode, vR = 191 cm-1 . Dispersed fluorescence spectra bear clear evidence that △v(R) = 1 Herzberg-Teller coupling dominates the near-resonant internal mixing between the S1 and S2 manifolds. The fluorescence into each pair of Franck-Condon active ring modes shows an asymmetry that suggests incorrectly that the S1 and S2 states may be electronically localized. From rotationally resolved studies, the S0 and S1 states have been well-fit to asymmetric rotor Hamiltonians while the S2 state is perturbed and not fit. The transition dipole moment (TDM) orientation of the S1 state is nearly perpendicular to the C2 symmetry axes with 66(2)%:3(1)%:34(2)% a:b:c hybrid-type character while that of the S2 origin contains 50(10)% a:c-type (S1) and 50(10)% b-type (S2) character. A model is put forward that explains qualitatively the TDM compositions and dispersed emission patterns without the need to invoke electronic localization. The experimental data discussed here serve as a foundation for a multi-mode vibronic coupling model capable of being applied to asymmetric bichromophores, as presented in the work of B. Nebgen and L. V. Slipchenko ["Vibronic coupling in asymmetric bichromophores: Theory and application to diphenylmethane-d5," J. Chem. Phys. (submitted)]. [ABSTRACT FROM AUTHOR]

The roadblock on the way to perform the quantum mechanical calculation as the "SCF or DFT" method for some molecules such as drugs, biological molecules, and so on is that these molecules are too large to study. They need a computer with a large amount of system memory and a very fast CPU. Therefore, we are looking for an entirely quantum-mechanical procedure to study the electronic properties of a large molecule with considerable saving computational time and acceptable accuracy. This procedure is based on searching for the active parts of a molecule, which are essentially HOMO and LUMO parts and their surroundings, and is called truncated molecule (TM) in this manuscript. To this end, at first, this procedure is inspected for Mn-complex, due to the availability of its experimental UV spectra. The calculation of the UV spectrum for TM part of Mn-complex shows λmax = 355.64 nm, while experimental UV spectra is λmax = 334.31 nm, and the corresponding theoretical value for the original molecule reveals λmax = 346.99 nm. The CPU time for the original molecule is 448,045 s that is reduced to 101,555 s for TM with acceptable accuracy (the CPU ratio is 4.41). Furthermore, this procedure is also tested for one of the sequences of A-chain of insulin, Docetaxel (drug molecule), and Taxol (drug molecule); the acceptable resemblance between UV spectra of the original and TM molecule is obtained. The computational time is reduced with a ratio of 3.59, 2.44, and 1.69, respectively. [ABSTRACT FROM AUTHOR]

Amino acids, polypeptides and proteins, which are all chiral, are the most important living substances. Most living organisms are made up of L-amino acids. Chirality is of great significance in exploring biomolecules. Studying polypeptides with a large number of atoms is a great challenge for quantum chemistry calculation. We conduct structural studies and perform vibrational and electronic spectra investigations on two polypeptides consisting of 14 L- and D-amino acids, both of which are right-handed α-helical. We find that the two polypeptides have similar IR and Raman vibrational spectra except that the polypeptide constituted by D-amino acids has an intramolecular hydrogen bond peak, but their chiral and excited state spectra are different and the chiral spectra are not mirror symmetric, which can be applied to distinguish them and shows that they have different structures in detail. Thus they may have different properties and functions. In addition, the amide III vibrations of the polypeptide include the information of the backbone and side chains. Therefore, care should be taken to apply the amide III vibrations to determine the secondary structure of polypeptide. [ABSTRACT FROM AUTHOR]

In this work, the structure–property relationship of push–pull chalcone derivative (3DPNP) has been studied through spectroscopic experiments and density functional theory calculations. The figure on the right side shows the non-linear absorption and non-linear refraction curves of 3DPNP. [Display omitted] • The structure–property relationship of a chalcone-based push–pull molecule (3DPNP) was explored using combined experimental and theoretical studies. • The vibrational and electronic contribution to NLO activity of 3DPNP was estimated. • Frequency-dependent NLO calculations shows abrupt changes when the incident frequency is doubled which confirms SHG efficiency of 3DPNP. • Z-scan studied indicated that the molecule 3DPNP is suitable for optical limiting application in CW laser regime. • The optical limiting threshold of 3DPNP is found to be 3.26 kJ/cm2. In this work, the optical limiting response of a highly π-conjugated push–pull chalcone derivative (2 E)-3-(2,3-dimethoxyphenyl)-1-(3-nitrophenyl)prop-2-en-1-one (abbreviated as 3DPNP) has been investigated. The structure–property relationship of 3DPNP was explored through spectroscopic investigation and quantum chemical computations. The existence of weak-non-covalent interactions and charge transfer species that responsible for the chemical stability of 3DPNP were studied by AIM and NBO analyses. The quantitative and qualitative analysis of vibrational and electronic contribution to non-linear optical (NLO) response of 3DPNP were discussed in detail. The normal vibrational modes associated with a change in the dipole moment, polarizability, first- and second-order hyperpolarizabilities of 3DPNP were identified using DFT calculations followed by potential energy distribution (PED) analysis using Gaussian 09 W software and Gar2ped program, respectively. The changes in the NLO parameters with respect to the varying frequencies and electric dipole fields were studied. The abrupt changes in the NLO properties were noticed when the frequency doubled, confirming the second harmonic generation (SHG) efficiency of 3DPNP. From the non-linear absorption and refraction studies through the z-scan experiment, the optical limiting threshold value of 3DPNP is determined to be 3.26 kJ/cm2, which shows the suitability of the material for optical limiting applications in the continuous wave (CW) laser regime. [ABSTRACT FROM AUTHOR]

Three novel five coordinated square-pyramidal bis-dioxolene cobalt complexes with triphenylphosphine were synthesized and characterized. A complex bearing donor methoxy substituents demonstrates a doublet → sextet spin crossover transition in solid state at temperatures above 250 K. [Display omitted] Three novel five-coordinated bis-dioxolene cobalt complexes with triphenylphosphine were synthesized. Complexes differ by dioxolene ligands: 3,6-di- tert -butylcyclohexa-3,5-diene-1,2-dione (complex 1), 5,8-di- tert -butyl-2,3-dihydro-1,4-ethanoquinoxaline-6,7-dione (complex 2), 3,6-di- tert -butyl-4-methoxycyclohexa-3,5-diene-1,2-dione (complex 3). The geometry of the inner coordination core of all compounds is close to square pyramidal. The base of the pyramid is formed by oxygen atoms of the dioxolene ligands whereas phosphine occupies the apical position. The planes of dioxolenes are slightly bent relative to each other. The magnetic moment values at low temperatures correspond to one unpaired electron per molecule for all complexes. In the complex containing a methoxy group in the dioxolene ligand (3), an increase in the magnetic moment is observed upon heating above 250 K, which indicates the appearance of a fraction of molecules with a higher spin multiplicity. A slight elongation of the Co-O, Co-P distances and shortening of the C O bonds is observed at 353 K. DFT calculations using the TPSSh functional correctly reproduce geometries of the complexes as well as their electronic absorption and vibrational spectra. DFT predicts the doublet-state complexes to possess the lowest enthalpies. Gibbs free energy of sextet complex 3 in solution is lower than that of its doublet state. This agrees well with the experimental electronic absorption spectra. On the basis of TD DFT calculations, a strong NIR absorption band in the spectra of low-spin 1 and 2 is assigned to the transition involving charge transfer from cobalt to the dioxolene and PPh 3 ligands (MLCT). The doublet molecules can be described by the (↑SQ—)(Co3+)(Cat2—) ↔ (Cat2—)(Co3+)(↑SQ—) resonance structures. The sextet state in all three systems represents the (↑SQ—)(↑↑↑Co2+)(PPh 3)(↑SQ—) bis-semiquinonate complex of high-spin Co(II). On the basis of the conventional description the doublet → sextet transition in complexes can be interpreted as a VT/SCO transformation. The electron density analysis of the doublet → sextet transition in the 1 and 3 molecules reveals areas of both increase and decrease in the charge density near the Co and O atoms. [ABSTRACT FROM AUTHOR]

It should be noted that carbon nitride is a two-dimensional nanomaterial and composed from carbon and nitrogen elements. Nanobiophysics is a new branch of science that emerged at the intersection of physics, biology, chemistry, materials science, nanotechnology, and medicine. One of them is dedicated to DNA conjugation with metal ions, in the other two experimental and theoretical articles DNA-protein interaction is considered. Authors have developed a polyelectrolyte model of monovalent counterions around I B i -forms of double-stranded DNA and also carried out the analysis of the counterion distribution around the DNA using molecular dynamics simulations. [Extracted from the article]

Quantum chemical cluster calculations show that reactions of C+ with HCN or HNC embedded in the surface of an icy grain mantle can account for the formation of a recently detected molecule, glycolonitrile, which is considered to be an important precursor to ribonucleic compounds. Reactions of cations deposited on ice mantles with minimal kinetic energy have been found theoretically to result in previously unknown pathways to significant organic compounds in protostellar systems and the interstellar medium. In density functional theory cluster calculations involving up to 24H2O, C+ reacts consistently with HCN embedded in ice to yield the neutral HOCHNC radical with no barrier, along with H3O+ as a byproduct. If HOCHNC then reacts with H, three species can be formed: HOCH2NC (isocyanomethanol), HOCH2CN (glycolonitrile), and HOCHNCH. For the C++ HNC reaction on ice, the HOCHCN and H2OCCN radicals form as intermediates, the first of which is another direct precursor to glycolonitrile via H addition. In addition to characterizing reaction pathways, predictions are provided of the vibrational and electronic spectra of the HCN and HNC starting clusters and the HOCHNC ice-bound intermediate. [ABSTRACT FROM AUTHOR]

The OH‐based excited‐state intramolecular proton transfer (ESIPT) of 2‐(5‐(4‐carboxyphenyl)‐2‐hydroxyphenyl)benzothiazole (CHBT) derivatives (4R‐CHBT) that were replaced by electron‐donating groups (CH3, OH) and electron‐withdrawing groups (COOH, CF3, CN) have been studied by the time‐dependent density functional theory (TD‐DFT) method. We analyzed structural parameters, infrared (IR) vibrational spectrum, frontier molecular orbitals (FMOs), and electronic spectra, which can describe the trend of ESIPT process. The constructed potential energy surfaces showed that the ESIPT potential energy barriers of 4R‐CHBT are in the range of 0.25 to 0.62 kcal/mol, which are just a little bigger than that value of CHBT. All the chosen substituents, no matter electron‐donating or electron‐withdrawing groups, make ESIPT processes slightly more difficult. [ABSTRACT FROM AUTHOR]

Echinatin (Ech), a characteristic retrochalcone isolated from liquorice, a widely used herbal medicine, has been investigated in detail in terms of its conformational and electronic properties in different dielectric media using density functional calculations. Natural bond orbital (NBO) analysis suggests an extended conjugation in the molecule, including a keto-ethylenic group (–CO–CH=CH–) connecting both the rings. The aromaticity of Ech has been studied using the nucleus-independent chemical shift (NICS) method. The acidity constants (pKa) have been simulated for both the hydroxyl groups in the molecule. Molecular electrostatic potentials (MEPs) have been computed to predict the reactivity of Ech toward both electrophiles and nucleophiles. Further, the electronic spectra of the neutral and deprotonated states have been computed in different solvents using an implicit solvation model, SMD. The vibrational spectra of both the neutral and anionic forms have also been simulated. Besides these, 1H-NMR and 13C-NMR spectra have been computed and compared with the experimental values. In addition, the frontier molecular orbital (FMO) energies, a number of global reactivity descriptors, viz., chemical hardness (η), chemical potential (μ), global softness (S), global electrophilicity (ω), and nucleophilicity (N) indices and various thermodynamic parameters have also been calculated in order to get a better insight into the molecular properties. [ABSTRACT FROM AUTHOR]

The current work deals with the VO(II), Cr (III), Mn(II) complexes which have been made by a new ligand, To classify the three complexes, infrared spectroscopy was used. FTIR, UV SPectroscopy and AtomiC AbSorption Spectrometry were also used to detect the ratio of carbon, hydrogen and nitrogen synthesized and precise materials. There was also a study of the physical properties like Temperature, Color, ElectrIcal Conductivity, and Magnetic characteristics. The ligand preparation was 2: 1, besides, all the synthesized complexes were 8 slanted façades. A theoretic treatment for structural of the (L) and its complexes in gas phase was conducted by using Hyper Chem. 8 program. PM3 Method used calculating the electrostatic potential (EP) and Molecular Orbital Surfaces of the (L). The Heat of Formation (ΔHf), Binding Energy (ΔEb), Total energy (ΔET), Vibration Spectra, and Electronic Spectra for the Ligand (L) and its metal complexes were calculated by PM3 and ZINDO/1 methods. [ABSTRACT FROM AUTHOR]