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In this study, a range of organic dyes were prepared to investigate difference between five- and six- number-membered ring transition states for internal proton transfer in excited state. Different strength intramolecular hydrogen bond in the target dyes was demonstrated by X-ray crystallography, 1 H NMR spectroscopy and ultraviolet/visible spectroscopy. The fluorescence measurement suggested excited state intramolecular proton transfer occurred via six number-membered ring transition state, while it could not occur through five number-membered ring transition state. The molecular geometry optimization of the target dyes further accounted for the difference of internal proton transfer in excited state occurred by five- or six- number-membered ring transition state. [ABSTRACT FROM AUTHOR]

We have investigated the electronic and geometric structures in the lowest excited states of six phosphorescent heteroleptic [Cu I (NN)(DPEphos)] + (DPEphos = bis[(2-diphenylphosphino)phenyl]ether) complexes with varying NN = diimine ligand structures using density functional theory. In comparison to the ground state, the results show a decrease of the dihedral angle between the N–Cu–N and P–Cu–P planes for these excited states with mixed ligand-to-ligand (DPEphos lone pair → π ∗ (NN)) and metal-to-ligand charge transfer (dπ(Cu) → π ∗ (NN)) character. Sterically less demanding ligands facilitate this process, which is accompanied by a geometric relaxation of the DPEphos ligand and contraction of the Cu–N bonds. The density functional for the excited state calculations has been selected based on ground state validation studies. We evaluated the ability of seven density functionals to reproduce the molecular ground state geometries and absorption spectra obtained by single-crystal X-ray diffraction and solution-phase UV–Vis absorption spectroscopy respectively. Standard methods (PBE and B3LYP), which do not account for dispersion, systematically overestimate internuclear distances. In contrast, approaches including dispersion (B97D3, PBE0-GD3, M06L, M06, ω B97XD) remove this systematic effect and give less expanded molecular structures. We found that only the hybrid functionals (B3LYP, PBE0-GD3, M06), incorporating a portion of exact exchange from Hartree–Fock theory, accurately predict the experimental absorption energies. [ABSTRACT FROM AUTHOR]

The photodissociation process of the nitrosyl hematoporphyrin complex has been studied using quantum-chemical methods. Photolysis of hematoporphyrin complexes is of high biological usefulness and is widely employed in laser-therapy methods. However, the mechanism of photodissociation of these complexes is not entirely clear. Based on the computations, we propose a detailed mechanism for the photolysis of the nitrosyl hematoporphyrin complex. A transition 'dissociative' excited state has been described, which has an energy barrier value of only 0.4 eV for NO dissociation. [ABSTRACT FROM AUTHOR]

The two-state reactivity of N-exposure including C N bond dissociation and ring-closure elementary steps are characterized by DFT atomistic modelling. Geometries, energetics and frequencies of equilibrium structures and transition states with pronounced barriers are evaluated at the B3LYP/6-31G(d) level of theory. Special emphasis is placed on the substituent effect, the role played by nearby saturated carbon and the characteristics of excited state pathways. When comparing the energetics, our DFT results show the nature of resonance may lead to the decrease of activation energy and endothermicity, highlighting the importance of oxyradical substituent for N-exposure. Also, it can be found that the presence of nearby H will saturate the carbon atom and therefore inhibits the N-exposure reaction. What is more, the excited state pathways with lower energy barrier and larger reaction energy should be cautioned for reactivity modelling of the carbonaceous surface. Understanding of the N-exposure reaction will finally provide insight into not only the mechanism associated with the conversion of char-N to volatile-N, but also an idea for further research of N-related thermo-chemical behaviors. [ABSTRACT FROM AUTHOR]

Introduction Previous studies have demonstrated the potential of solvatochromic dyes for investigating the physical chemistry of homeopathic potencies. Results Following examination of this class of dyes in organic solvents, results obtained using the positively solvatochromic dye Bis-dimethylaminofuchsone (BDF) in aqueous solution are now reported. Spectral changes observed with this dye in the presence of potencies are both substantial and reproducible. Studies across a wide range of pH values reveal an unusual pH dependence for the dye's interaction with homeopathic potencies. Results indicate potency enhances dye protonation at pH values below c. 7.0, whilst protecting the dye from attack by hydroxyl ions above c. pH 7.5. Conclusion A possible explanation for these observations is offered in terms of a potency – induced electron density shift in BDF. The interaction of homeopathic potencies with solvatochromic dyes, particularly BDF, points towards a possible physico-chemical model for the nature of potencies, how they may be interacting with this class of dyes, and moreover how their biological effects may be mediated. [ABSTRACT FROM AUTHOR]

In this paper, the influence of different ancillary ligands on geometric structures, frontier molecular orbitals character, gap energy and electronic absorption spectra of [Ir(5-NO 2 -ppy) 2 (PPh 3 )(L)] (L = Cl − , NCO − , NCS − and N − 3 ) has been theoretically studied by density functional theory and time-dependent density functional theory calculations with B3LYP and PBE0 hybrid functionals. Calculated geometric parameters of studied complexes are in good agreement with the available experimental values. The theoretical absorption spectra reproduce the main properties of the experimental spectra. Both energy gaps and absorption spectra depend on the composition of HOMO Orbital, π-donor orbitals reduce the energy gaps and red shift the absorption spectra while π-acceptor orbitals increase the energy gaps and blue shift the absorption spectra. All the spectra are characterized by mixed MLCT/LLCT states in the visible energy domain. [ABSTRACT FROM AUTHOR]

This study presents a variety of organic dyes with similar molecular structures that could undergo intramolecular proton transfer in excited states via five-, six- and seven-number-membered ring transition states, respectively. In addition, the dyes without proton transfer segments are also synthesized to use as references. X-ray single crystal diffraction, NMR spectra as well as UV/visible spectra suggests the presence of internal hydrogen bond with different strength in the target dyes. The steady and transient fluorescence measurements demonstrate occurrence of excited state intramolecular proton transfer via a six number-membered ring transition state. In contrast, it cannot be processed through five- and seven-number-membered ring transition states of the studied dyes. The molecular geometry optimization of the studied dyes reveals fundamental factors for the difficulties of intramolecular proton transfer in excited states via five- and seven-number-membered ring transition states. [ABSTRACT FROM AUTHOR]

This study presents an efficient algorithm to search for the poles of dynamic polarizability to obtain excited states of large systems with nonlocal excitation nature. The present algorithm adopts a homogeneous search with a constant frequency interval and a bisection search to achieve high accuracy. Furthermore, the subtraction process of the information about the detected poles from the total dynamic polarizability is used to extract the undetected pole contributions. Numerical assessments confirmed the accuracy and efficiency of the present algorithm in obtaining the excitation energies and oscillator strengths of all dipole-allowed excited states. A combination of the present pole-search algorithm and divide-and-conquer-based dynamic polarizability calculations was found to be promising to treat nonlocal excitations of large systems. © 2016 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Carrier heating (CH) theory in a four-wave mixing quantum dot structure has been investigated. The impact of wetting layer (WL) carrier density, CH time constant, effective intraband relaxation time have been examined. The derived heat capacity for QD structure have ( T - 1 ) dependence. It is shown here that both WL carrier density and QD excited state (ES) occupation controls the overall nonlinear contributions. Then inclusion of WL and ES in the CH induces a new equilibrium reached at a faster recovery time. The proposed model yields results in a line with experiments at high carrier density reflecting the efficiency of our model. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesis of BNBT with a high key-step yield based on simple raw materials. • An empirical linear relationship between Stokes shift and solvent parameters. • High fluorescence quantum yield and extremely low triplet yield of BNBT. We report a novel synthetic route of BN-benzo[b]triphenylene (BNBT) with a key-step yield exceeding 90% based on simple raw materials. The solvent effect on the optical absorption and fluorescence of BNBT is examined, and a linear relationship between the Stokes shift (Δ ν S) and the solvent parameters { α , β , π *} is generalized. The fluorescence lifetime correlates positively with the fluorescence quantum yield, which is about 10 folds of benzo[b]triphenylene (BT) as a structural counterpart (66% vs 6%). Moreover, the quantum yield of triplet-excited state BNBT is shown to be as low as a few thousandths. [ABSTRACT FROM AUTHOR]

• The molecular properties of an insulating gas material under electric field were studied theoretically. • In the specific electric field direction, the molecular ionization potential decreases significantly. • The long carbon chain molecules may reduce the insulating performance of the insulating gas. With the deterioration of global greenhouse effect, CF 3 SO 2 F (Trifluoromethanesulphonyl Fluoride) has become an alternative gas of SF 6 (Sulfur Hexafluoride). CF 3 SO 2 F has environmentally friendly characteristics and has been widely concerned. In this work, we analyze the electric field level of the discharge in the dielectric and the direction of the molecular intrinsic dipole moment. Density functional theory and time-dependent density functional theory are used to calculate the molecular structure parameters, dipole moments, frontier orbitals and excited states at corresponding electric field levels and in specific electric field directions. C 2 F 5 SO 2 F and C 3 F 7 SO 2 F, as by-products in the synthesis of CF 3 SO 2 F, are studied together to explore the influence of carbon atom number on molecular properties. As a result, the molecular structure is clearly changed under the electric field and the molecular bond length strongly depended on the electric field. The HOMO is mainly contributed by O atoms and the LUMO is mainly contributed by S atoms. When the electric field in the -z-axis direction is applied, the HOMO energies of molecules increase, especially for C 3 F 7 SO 2 F molecule, and the ionization potentials decrease correspondingly. The reduced ionization potentials facilitate the liberation of electrons from the molecule and the propagation of the streamer. The excitation energy of each molecule in each excited state decreases with the increasing of electric field intensity. Therefore, during the preparation process of CF 3 SO 2 F molecule, C 3 F 7 SO 2 F molecule should be reduced or removed as much as possible to prevent the reduction of dielectric insulation strength. The finding of this study is beneficial to the performance improvement and application research of CF 3 SO 2 F. [ABSTRACT FROM AUTHOR]

[Display omitted] • The excited-state properties of three hydroxyanthraquinone compounds from the Marine Crinoid Pterometra venusta were studied by TDDFT. • After the excitation procession the pull shrinkage deformation about the middle ring is slightly stronger in HAQ3 than HAQ1 and HAQ2. • For S 0 → S 1 excitation, HAQ1 and HAQ2 is the local excitation of π-π*, while HAQ3 presents S 0 → S 1 as n-π*charge transfer excitation characteristic. Three natural hydroxyanthraquinone compounds HAQ (1–3) extracted from the Marine Crinoid Pterometra venusta. In order to identify their photochemical and electronic excited state properties of them, the theoretical research of optoelectronic properties have been studied. Using density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods, UV- absorbance and fluorescence emission spectra of HAQ (1–3) had been calculated. The results show that calculated spectra are very consistent with the experimental data. For S 0 → S 1 excitation, HAQ1 and HAQ2 are the local excitation of π-π*, while HAQ3 presents S 0 → S 1 as n-π*charge transfer excitation characteristic. [ABSTRACT FROM AUTHOR]

• New tris(trifluoromethyl)germylethynyl derivative of biphenyl with ferrocenylethnyl donor group have been prepared. • Intramolecular energy and electron transfer have been investigated in the unsymmetrical 4-ferrocenylethnyl-4´-[tris(trifluoromethyl)germylethynyl]biphenyl molecule. • Vacant Ge 4d atomic orbitals play a key role in this phenomenon. Unsymmetrical 4,4′-biphenyl derivative with tris(trifluoromethyl)germylethynyl ‒C C‒Ge(CF 3) 3 and ferrocenylethynyl Fc‒C C‒ substitutes have been prepared (21), its properties have been studied and compared with those full non-fluorinated analogue of trimethylgermylethynyl ‒C C‒Ge(CH 3) 3 compound (20). UV-visible, absorption, steady state, and time-resolved fluorescence spectra in solution for these germanium and a number of similar compounds (15 - 17, 22) have been investigated. The process of photoinduced electron transfer from the π-conjugated system to the germanium center is confirmed for 21 , as well as for the first time discovered earlier [19] in the 4-biphenyl ‒C C‒Ge(CF 3) 3 molecule (9). It was found that the lifetime of the radical-ion pair 21 in the excited state (k CR2 = 1.2 × 105 s-1) is approximately an order of magnitude longer than for 9 , which can be explained by the stabilizing effect of the electron donor Fc‒C C‒ group. Density-functional theory (DFT) computations was used to calculate the optimized geometry of 21 in excited state, and two main bands in the emission spectrum at laser excitation (340 and 386 nm) an excellent fit to the experimental data. An additional data on the nature of the (CF 3) 3 Ge group, including geometry, electronegativity, and contributions 4d AOs of germanium into lowest unoccupied molecular orbital (LUMO) in a wide range of fluorinated and non-fluorinated compounds were also calculated. The molecular structure of compound 21 was determined by X-ray structural analysis. In the crystal lattice of 21 , numerous intermolecular F‧‧‧F interactions shortened in comparison with the van der Waals radii were detected, which leads to the formation of quasi-two-dimensional fluorinated layers in crystals. The unsymmetrical triad of 4-ferrocenylethynyl-4΄-[tris(trifluoromethyl)germylethynyl]biphenyl exhibits stepwise intramolecular energy and charge transfer into (CF 3) 3 Ge group upon laser excitation at 266 nm. This confirms the previously discovered effect for a similar compound of 4-[tris(trifluoromethyl)germylethynyl]biphenyl containing no ferrocenylethynyl group. The total quantum yield of the state with completely separated charges is 33%. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Regulating excited-state properties for high brightness DR/NIR fluorophores. • Both fluorophores show aggregation-induced emission performance. • The PLQY arrives to 56 % with maximal emission of 692 nm at aggregation. Deep red/Near-infrared (DR/NIR) emitters with high photoluminescent quantum yield (PLQY) in the aggregate state are still challenge for achieving highly efficient non-doped organic light emitting diodes (OLEDs). Herein, we utilize the methodology of regulating excited-state property to adjust the proportion of radiative and nonradiative transition at aggregation, three aggregation-induced emission (AIE) active emitters (TNZNp, TNZTPAN and TNZTPEDA) with diverse sum of benzene ring rotors are prepared. TNZTPEDA with more rotors suffers from fast nonradiative transition which leads to the low fluorescent efficiency in the unimolecular and aggregate levels. Oppositely, decreasing rotors to enhance obviously solid-state PLQY of TNZNp, but the radiative transition rate is still lower than the nonradiative rate. After introducing rotational electronic donor to improving locally excited-state proportion and suppress intermolecular interaction, simultaneously, TNZTPAN has the best PLQY of 56 % due to the faster radiative transition than nonradiative transition at aggregation. Three emitters are used to manufacture non-doped OLEDs, TNZTPAN shows the maximal electroluminescence peaking at 692 nm with Commission International de L'Eclairage coordinates of (0.68, 0.30), the external quantum efficiency of 3.54 % represents a higher level among the reported non-doped DR/NIR-type OLEDs. The results of this work demonstrate the feasibility of regulating excited-state property to prepare highly bright emitters, which plays important role in designing organic DR/NIR emitters with high fluorescent efficiency at aggregation in the future. [ABSTRACT FROM AUTHOR]

[Display omitted] • electronic properties of γ-graphyne cluster models converge rapidly. • electronic properties of γ-graphyne clusters have a low dependence on vacancy defects. • γ-graphyne is an efficient electron acceptor (low LUMO and ability to delocalize excess charge). • photoinduced electron transfer from electron donors to γ-graphyne is efficient and fast. The search for new materials is constantly ongoing. Recently, a two-dimensional carbon allotrope , γ-graphyne , has been synthesized with a unified crystalline structure. Because of its low LUMO and excellent electron mobility, it appears to be a promising electron acceptor for photovoltaic applications. Here we report an analysis of the electronic properties of model van der Waals complexes of γ-graphyne with several partners of different electronic nature. We show that photoinduced electron transfer from electron-donating partners to γ-graphyne is favorable and occurs on nano to picosecond time scale. In contrast, electron transfer from γ-graphyne to strong electron acceptors is unlikely. Our results open perspectives for the future application of γ-graphyne in photovoltaic devices. [ABSTRACT FROM AUTHOR]

A better knowledge of the structure of the electronically excited state of substrates is indispensable for the understanding and optimization of . For this study, triplet energies of a variety of α,β-unsaturated γ-lactones (furanones) as well as the structures of the vibrationally relaxed triplet state (T1) have been determined using ab initio coupled-cluster (CCSD) method and/or density functional theory (DFT) calculation. A twist of the original planar structure around C = C bond is found in the relaxed triplet state, π-π*. In the 5-membered ring of furanones the contribution of this mode is limited and the pyramidalization in the C4 position also contributes to the stabilization. The contribution of each stabilization mode is characterized by the dihedral angles and the Mulliken atomic spin densities. The substituent effect on the pyramidalization and the spin density distribution in the C4 and in the C5 position are reported. Depending on the substitution in the C4 position, the orientation of the pyramidalization is either favored syn or anti with respect of the hydroxyl substituent in the C5 position. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Potential energy curves (PECs) for the ground and first-excited electronic states of Na2 are obtained by fitting the ab initio energies calculated at the MRCI(Q)/aug-cc-pV XZ ( X = T, Q, 5) level of theory, which are subsequently extrapolated to the complete basis set limit. The relativistic effect and core-valence correlation are also considered. The PECs are accurate at both short and long internuclear distances with the root-mean-squared deviations being 0.72 cm−1 for Na2 and 0.36 cm−1 for Na2 . Utilizing the obtained PECs, we calculate the spectroscopic parameters, vibrational energy levels, classical turning points, inertial rotation, and centrifugal distortion constants, which are in good agreement with other theoretical and experimental work. [ABSTRACT FROM AUTHOR]

The ground-state geometries, electronic structures, spectra and photoelectric properties of two dyes (JA1 and JA2) used for dye-sensitised solar cells (DSSCs) have been investigated with density functional theory (DFT) and time-dependent density functional theory (TDDFT). For simulation of the realistic environment, we calculated the energy levels of molecular orbitals and absorption spectra in solvent, and the different electric fields have been considered. For interpreting the difference of photoelectric properties, we assessed the energy levels and energy gaps of frontier molecular orbitals, electron density, absorption, the total static first hyperpolarisability and driving force of electron injection. The relationship between structure and performance should be established. Furthermore, 24 dyes were designed on the basis of JA1 and JA2 to improve optical response and electron injection. The results of molecular modelling would provide the optional approach for improving performance of photoelectric materials. [ABSTRACT FROM AUTHOR]

The photophysics of the photoinitiator Camphorquinone was investigated computationally in this work, by using time-dependent Density Functional Theory methods. DFT calculations. We fully assigned the UV-Vis electronic transition of the Camphorquinone monomer. Moreover, the emission energy as well as the structural differences between the geometries of the molecule in the ground and excited state have been analyzed. [ABSTRACT FROM AUTHOR]

Basing on the experimental data, it has been shown that for EХ (E = N, P, As, or Sb; X = F, Cl, Br, I, CH, СН, or SiH) compounds the value of the difference between first ionization potentials of atoms and molecules is a function of the bond angle and dipole moment of the molecule. The calculated values of dipole moments of charged atoms and groups are regularly changed within the considered compounds series. The change of the dipole moment of the molecules during the vibrational excitation has been determined, and intensities of symmetric stretching and deformation bands in IR spectra of EF and ECl compounds have been estimated. [ABSTRACT FROM AUTHOR]

The photoelectrical properties of two dyes--ethyl red and carminic acid--as sensitizers of dye-sensitized solar cells were investigated in experiments herein described. In order to reveal the reason for the difference between the photoelectrical properties of the two dyes, the ground state and excited state properties of the dyes before and after adsorbed on TiO2 were calculated via density functional theory (DFT) and time-dependent DFT (TDDFT). The key parameters including the light harvesting efficiency (LHE), the driving force of electron injection (ΔGinject) and dye regeneration (ΔGregen), the total dipole moment (μnormal), the conduction band of edge of the semiconductor (ΔECB), and the excited state lifetime (τ) were investigated, which are closely related to the short-circuit current density (Jsc) and open circuit voltage (Voc). It was found that the experimental carminic acid has a larger Jsc and Voc, which are interpreted by a larger amount of dye adsorbed on a TiO2 photoanode and a larger ΔGregen, excited state lifetime (τ), μnormal, and ΔECB. At the same time, chemical reactivity parameters illustrate that the lower chemical hardness (h) and higher electron accepting power (ω+) of carminic acid have an influence on the short-circuit current density. Therefore, carminic acid shows excellent photoelectric conversion efficiency in comparison with ethyl red. [ABSTRACT FROM AUTHOR]

We describe and analyze the selective (resonance) laser-induced initiation of chemical decomposition reactions in PETN and propose a potential mechanism of the phenomenon. Based on our experiments, the photoinitiation of PETN is a two-stage process that is comprised of a laser-induced optical excitation of the molecule with the activation energy of 1.17 eV (1060 nm) by neodymium phosphate glass laser followed by the thermal decomposition of the excited state with the energy barrier of 0.4 eV. We also illustrate that the small efficiency of the optical absorption of PETN at this wave length can be enhanced by the MgO light scattering additives, which significantly increase the absorption due to multiple scattering incidents in PETN. The discovered resonance photoinitiation clearly demonstrates a strategy for designing tunable explosive material systems and identifies ways to control sensitivity of the materials to rapid decomposition.

Herein we employ density functional theory (DFT) and linear response time-dependent density functional theory (LR-TDDFT) together with our own n-layered integrated molecular orbital and molecular mechanics (ONIOM)-based quantum mechanical/molecular mechanics (QM/MM) methods to study the room-temperature phosphorescent (RTP) micro-mechanism of several benzonitrile-carbazole (CzBz-X) molecules (i.e. CzBz-H, CzBz-F, CzBz-Cl, CzBz-Br) in liquid and solid state. Based on the calculated the ground- and excited-state geometric and electronic structures, the absorption and emission spectra are simulated and agreed well with previous experimental observation. The intersystem crossing (ISC) rate constants of S1 -> T1 obtained by the formula derived from the Fermi golden rule are small in liquid state, while the ISC rate constants are comparable to the relative radiative rate constants of S1 ->S0 in solid state. Molecular vibrations are restricted in solid state, which lead to the decrease of reorganization energies and Huang-Rhys factors, and the increase of ISC rate constants. Both the heavy-atom effect and aggregation effect play important roles in improving the RTP performance in CzBz-X compounds. Through quantum chemistry calculations, the present work not only elucidates the RTP mechanism and the significance of heavy-atom and aggregation effects in CzBz-X, but also provides new insights for designing novel RTP materials.

• The geometry changes of the tgt - and the ttt -rotamer of 1,2-diphenoxyethane have been determined from a combined fit of rotation al constants and fluorescence emission intensities from several vibronic bands. • The geometry changes are compared to the results of ab initio calculations at the spin-component-scaled approximate coupled cluster singles and doubles (CC2) level of theory. • The excitonic splitting of the origins of both rotamers has been determined from ab initio calculations. The geometry changes of the tgt - and the ttt -rotamer of 1,2-diphenoxyethane were determined from a combined fit of line intensities in fluorescence emission spectra, obtained via pumping different vibronic transition, and the changes of rotational constants upon electronic excitation, which were taken from [E.G. Buchanan, P.S. Walsh, D.F. Plusquellic, T.S. Zwier, J. Chem. Phys. 138 (2013) 204313]. The so determined geometry changes are compared to the results of ab initio spin-component-scaled approximate coupled cluster singles and doubles (SCS-CC2) calculations. [ABSTRACT FROM AUTHOR]

Photoenzymes use light to initiate biochemical reactions. Although rarely found in nature, their study has advanced understanding of how light energy can be harnessed to facilitate enzyme catalysis, which is also of importance to the design and engineering of man-made photocatalysts. Natural photoenzymes can be assigned to one of two families, based broadly on the nature of the light-sensing chromophores used, those being chlorophyll-like tetrapyrroles or flavins. In all cases, light absorption leads to excited state electron transfer, which in turn initiates photocatalysis. Reviewed here are recent findings relating to the structures and mechanisms of known photoenzymes. We highlight recent advances that have deepened understanding of mechanisms in biological photocatalysis. [ABSTRACT FROM AUTHOR]

• The electronic structures of SnBr are calculated with MRCI+Q method. • The spin-orbit coupling effect is considered. • The predissociation mechanism of 14Σ- is discussed. • The avoided crossing phenomenon of the same symmetry is analyzed. • The lifetimes of vibrational states of 12Σ+ are evaluated. The electronic structures and spectroscopic properties of SnBr molecule are calculated by high-level multireference configuration interaction (MRCI) method. The Davidson correction (+Q) and spin-orbit coupling (SOC) effect are investigated in the calculations. The potential energy curves (PECs) of 23 Ʌ-S states and 45 Ω states generated from those Ʌ-S states are obtained. Based on the calculated PECs, the spectroscopic constants of the bound states are evaluated, which are in good accordance with previous experimental data. At the avoided crossing point, the dipole moments (DMs) of Ʌ-S states exhibit abrupt change, which are attributed to the change of electronic configurations of those states. With the help of the calculated SO matrix elements, the interaction between 14Σ- and nearby states is analyzed, and the possible predissociation pathway of low-lying vibrational levels of 14Σ- is illuminated. In the end, transition dipole moments (TDMs) and the radiative lifetimes from the excited states to the ground state are determined. [Display omitted] The calculated potential energy curves of the Λ-S states of SnBr using MRCI+Q method. [ABSTRACT FROM AUTHOR]

The structure-properties relationships of copolymer involving N-vinylcarbazole (PVK) and poly (p-phenylene-vinylene) ( PPV) blocks, denoted PVK–PPV, was investigated by calculations based on density functional theory (DFT) and completed by experimental analyses. Thus, vibrational, optical and emission spectra of model compound have been simulated and compared to the experiments observations published recently. Ionization potentials (IPs), electron affinities (EAs) and energy gaps were determined. Furthermore, quantum yields, radiative and nonradiative exciton lifetime was highlighted. [ABSTRACT FROM AUTHOR]

The analysis of electron structure of yttrium(III) complexes with cinnamic and quinaldic acids was carried out. Electron transitions were assigned, and influence of the nature of frontier orbitals on the position of absorption bands in the electron spectra was revealed. The TD-DFT calculation has shown that different ratios of intensities of π- π* and n- π* bands in the electron absorption spectra of the compounds are caused by different natures of frontier orbitals of the complexes. It was found that dipole moments of both complexes increase upon photoexcitation, greater changes being observed in Y(III) quinaldate. The reason of the greater Stokes shift of Y(III) quinaldate was established. [ABSTRACT FROM AUTHOR]

The structural and photophysical properties of four heteroleptic Iridium (III) complexes, based on 1-phenylpyrazole ligand, have been investigated theoretically. The effect of chemical substitution on the absorption and the emission spectra of the complexes has been studied and compared with the experimental data. We observe a significant structural change in the lowest triplet excited state as compared to the ground singlet state. We compute the emission wavelength of the complexes by considering the spin-orbit coupling. Using these understandings, we predict two new complexes having deeper blue emission which are supposed to be better efficient OLED materials. [ABSTRACT FROM AUTHOR]

The results of quantum yield (QY) study of tryptophanyl glutamate (Trp–Glu), tryptophanyl lysine (Trp–Lys) and lysinyl tryptophan (Lys–Trp) dipeptides over the pH range, 1.5–13, show that the charge state of the N-terminal amine, and not the nominal molecular charge determines the QY. When the terminal amine is protonated, QY is low (10 −2 ) for all three dipeptides. As the terminal amine cation is found proximal to the indole ring in Trp–Glu and Trp–Lys conformers but not in those for Lys–Trp, its effect may lie only in the partitioning of energy between nonradiative processes, not on QY reduction. QY is also low when both the N-terminal amine and indole amine are deprotonated. These two low QY states can be distinguished by fluorescence lifetime measurement. Molecular dynamics simulation shows that the Chi 1 conformers persist for tens of nanoseconds such that 10 0 –10 1 ns lifetimes may be associated with individual Chi 1 conformers. The ground state electron density or isosurface of high QY (0.30) 3-methyindole has a uniform electron density over the indole ring as do the higher QY Trp dipeptide conformers. This validates the association of ground state isosurfaces with QY. Excited state orbitals from calculated high intensity, low energy absorption transitions are typically centered over the indole ring for higher QY dipeptide species and off the ring in lower QY species. Thus excited state orbitals substantiate the earlier finding that the ground state isosurface charge density pattern on the indole ring can be predictive of QY. [ABSTRACT FROM AUTHOR]

To tune the efficiency of organic semiconductor devices it is important to understand limiting factors as trapping mechanisms for excitons or charges. An understanding of such mechanisms deserves an accurate description of the involved electronical states in the given environment. In this study, we investigate how a polarizable surrounding influences the relative positions of electronically excited states of dimers of different perylene dyes. Polarization effects are particularly interesting for these systems, because gas phase computations predict that the CT states lie slightly above the corresponding Frenkel states. A polarizable environment may change this energy order because CT states are thought to be more sensitive to a polarizable surrounding than Frenkel states. A first insight we got via a TD-HF approach in combination with a polarizable continuum model (PCM). These give limited insights because TD-HF overestimates excitation energies of CT states. However, SCS-CC2 approaches, which are sufficiently accurate, cannot easily be used in combination with continuum solvent models. Hence, we developed two approaches to combine gas phase SCS-CC2 results with solvent effects based on TD-HF computations. Their accuracies were finally checked via ADC(2)//COSMO computations. The results show that for perylene dyes a polarizable surrounding alone does not influence the energetic ordering of CT and Frenkel states. Variations in the energy order of the states only result from nuclear relaxation effects after the excitation process. © 2016 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

In this work, the low-lying electronic singlet states of 9-methylhypoxanthine (9MHPX) were explored by the complete active space self-consistent-field (CASSCF) and complete active space second-order perturbation theory (CASPT2) calculations, and the conical intersections between the optically bright excited S1state and ground S0state were optimised by the two-root state-averaged SA-2-CASSCF approach. These studies indicate that four slightly different kinds of S1/S0conical intersections are identified computationally for 9MHPX, corresponding to four main internal conversion pathways, respectively, all of which are found to show the comparable timescales according to dynamics simulations. At the CASPT2 level, four brightππ* transitions of 9MHPX are calculated to locate at 4.47, 5.35, 5.97 and 6.30 eV, respectively, responsible for the available experimental absorption peaks of 9MHPX in the vapour phase (4.41, 5.19, 6.05 and 6.42 eV). Though one relatively weakππ* transition computed at 5.69 eV is not observed in the vapour phase, it is in accordance with the circular dichroism measurement of another hypoxanthine derivative deoxyinosine 5'-phosphate near 5.51 eV. [ABSTRACT FROM PUBLISHER]

So far, coumarin dyes have been extensively studied with various means to understand their photophysical behaviors and properties. Here, our performing time-dependent density functional theory calculation is aimed at exploring the excited-state hydrogen bonding dynamics of coumarin 153 (C153) in protic ethanol (EtOH) solvent. The calculated results suggest that the excited-state hydrogen bond CO⋯HO between CO group and OH group in the C153-EtOH complex is strengthened, and the S0 → S1 transition of the complex corresponds to the highest occupied molecular orbital (HOMO) hopping to the lowest unoccupied molecular orbital (LUMO). The excited-state hydrogen bond strengthening has been further confirmed by its larger binding energy in the S1 state than in the S0 state. In addition, because of the formation of the hydrogen bond CO⋯HO, a red shift of about 7 nm occurs in the electronic spectra of the C153-EtOH complex, which is in good accordance with the experiment result. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

We have performed a series of calculations using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) for 1-methylamideanthraquinone (MAAQ). In the S0 state of MAAQ, amide group is coplanar with anthraquinone, and an intramolecular hydrogen bond is formed. The transition has an intramolecular charge transfer character. Two stable structures (planar nMAAQ and twisted tMAAQ) have been obtained in the S1 state of MAAQ. Thereinto, nMAAQ is lower by 0.105eV than tMAAQ in energy, so nMAAQ is the dominant conformation in the S1 state of MAAQ and the emission spectra of tMAAQ cannot be observed in the solution of MAAQ. Excited state intramolecular proton transfer (ESIPT) between CO and N-H was not observed in the S1 state of MAAQ. Upon addition of fluoride anion, only twisted conformations were obtained in both S0 and S1 states of MAAQ-F. An intermolecular hydrogen bond is formed in the S0 state, and intermolecular proton transfer happens in the S1 state for MAAQ-F. • We find a stable conformer with an intramolecular C=O⋯H-N hydrogen bond for the S0 state of 1-methylamideanthraquinone (MAAQ). • There are two stable conformers (planar nMAAQ and twisted tMAAQ) in the S1 state of MAAQ, corresponding to two emission peaks in fluorescence spectra. • Upon addition of fluoride anion, doprotonation can occur in both S0 and S1 states of MAAQ. [ABSTRACT FROM AUTHOR]

A variety of AB2 type new target dyes containing two proton transfer segments ( o -hydroxy-phenyl-imino) are presented in this study. Furthermore, the corresponding reference molecules absent of hydroxy or imino groups are provided as well. Dual intramolecular hydrogen bonds in the target dyes are demonstrated by 1 H NMR spectra, X-ray single crystal analysis as well as one-photon absorption spectra. Linear emission properties (static and transient emission nature) and two-photon absorption optical properties of these target and reference dyes are determined in various media such as organic solvents, solid phase state as well as PMMA substrate. The results show that the new AB2 type target dyes can efficiently undergo internal proton transfer in the excited states under one-photon irradiation and near-infrared femtosecond laser two-photon irradiation, respectively, and thus they exhibit well-separated dual-emission. The molecular geometry optimization is performed for the analysis of the occurrence of internal proton transfer in the excited states of the target AB2 chromophores. [ABSTRACT FROM AUTHOR]

N-Hydroxypyridine-2(1H)-thione (N-HPT) is an important photochemical generator of hydroxyl radicals; however, it has been pointed out that N-HPT is not a specific precursor of hydroxyl radical. Photoionization of N-HPT competes with photochemical N–O bond cleavage in neutral aqueous solution. The possibility of a competitive reaction could be critical for studies using N-HPT as the radical precursor; therefore, the detailed behaviors of electronic excitation and ionization of N-HPT and its deprotonated anion, which is the dominant tautomer under neutral pH conditions, are studied using quantum chemical methods with the symmetry-adapted cluster-configuration interaction (SAC-CI) method and the polarizable continuum model (PCM). The detailed assignment of the UV–Vis spectra of N-HPT is provided, and the origin of the observed negative solvatochromism is found to be the charge transfer excitation between the sulfur and the pyridine ring. The photochemical N–O bond cleavage occurs via the conical intersections between the lowest π → π* and π → σ* states and between the π → σ* and ground state, when N-HPT dissociates into PyS· and ·OH radicals. The calculated ionization potentials of N-HPT and the deprotonated N-HPT anion are 5.75 and 4.67 eV in PCM water. This demonstrates that the charge transfer excitation energy between N-HPT and liquid water becomes significantly lower for the deprotonated anion in comparison with the neutral molecule. Even under mild photochemical conditions, photoinduced ionization of N-HPT may occur in neutral aqueous solution. [ABSTRACT FROM AUTHOR]

Numerical computations of ground and excited states of Bose–Einstein condensates (BECs) require high spatial resolution due to the presence of the multiscale structures and boundary layers and interior layers in the solution. In this paper, a new discontinuous Galerkin (DG) method is presented for the computation of ground and excited states of BECs. For the spatial discretization, the direct discontinuous Galerkin (DDG) method is applied by using the normalized gradient flow. For the time discretization, we integrate the ordinary differential equations (ODEs) which is obtained by linearizing the interaction term. To evaluate the matrix exponential operator efficiently, we apply the Krylov subspace approximations to the matrix exponential operator. Numerical examples with different potentials are reported to demonstrate the validity and effectiveness of the semi-implicit DG method. [ABSTRACT FROM AUTHOR]

Theoretical chemistry provides a panel of powerful tools to investigate the geometries and electronic properties of excited states. However, it is necessary to benchmark the accuracy of existing models to determine the range of their applicability and accountability. In the present work, the performance of two related methodologies in this context, symmetry-adapted cluster-configuration interaction (SAC-CI) and time-dependent double-hybrid density functional theory (TD-DHDFT), is compared in detail for the calculation of absorption and fluorescence energies of small organic molecules and π-conjugated heteroaromatic compounds. Pragmatically, for the SAC-CI calculations the singles and doubles linked excitation operators are considered in the wave functions. On the other hand, for the TD-DHDFT calculations the linear-response Tamm–Dancoff formalism has been imposed. The considered DH density functionals include the approximations from both families of adjusted and non-adjusted models. Our numerical data reveal that of the tested adjusted DHs, B2-PLYP performs the best, while among the category of non-adjusted approximations the PBE0-DH functional outperforms others. Furthermore, the DH density functionals show deviations less than those obtained from SAC-CI method. Putting all the results together, the B2-PLYP and B2GP-PLYP functionals are found to be superior for overall performance. Altogether, the present contribution and recent efforts in this arena point out that besides the ground-state properties the DH approximations have also unquestionably entered into the field of excited-state calculations, where the DHDFT again comes into play and further evidence on the quality of the corresponding models is pronounced. [ABSTRACT FROM AUTHOR]

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The time-dependent density functional theory (TDDFT) method has been carried out to investigate the hydrogen bonding dynamics of a series of hydrogen-bonded complexes of PYP chromophore formed with water molecules both in vacuum and aqueous solution. We demonstrate that the intermolecular hydrogen bonds formed between carbonyl oxygen and hydrogen of water are strengthened in the lowest bright state as well as one other charge transfer state and result in spectral redshift. Whereas, a totally opposite result happens to the site of phenolate oxygen, which can be confirmed based on the excited-state geometric optimizations by TDDFT method. In addition, the frontier molecular orbital analysis reveals the nature of the lowest bright state and the CT state as well as the understanding of the electronic excited-state hydrogen bonding dynamics. Moreover, two approaches are adopted to consider the solvation effect. [ABSTRACT FROM AUTHOR]

We present an efficient real-time time-dependent density functional theory (TDDFT) method for large-scale accurate simulations of electron–nucleus dynamics, as implemented in the time dependent ab-initio package (TDAP). By employing a local basis-set presentation, we are able to simulate systems of large size (∼500 atoms) and for long electronic propagation time (∼300–500 fs) with less computation cost while maintaining relatively high accuracy. We show several quintessential examples, such as photoabsorption spectra of dye-sensitized TiO 2 nanowire, proton transfer coupled nonradiative relaxation of eumelanin constituents, electron injection and electron–hole recombination in dye solar cells, hole-transfer dynamics between MoS 2 /WS 2 interlayer heterojunction, and solvent effects on electron dynamics. Our method is demonstrated to have superiority over available methods in dealing with interesting excited state characteristics of complex systems involving dynamics of electrons and atoms. [ABSTRACT FROM AUTHOR]

A search for double-beta decays of 136 Xe to excited states of 136 Ba has been performed with the first phase data set of the KamLAND-Zen experiment. The 0 1 + , 2 1 + and 2 2 + transitions of 0 ν β β decay were evaluated in an exposure of 89.5 kg ⋅ yr of 136 Xe, while the same transitions of 2 ν β β decay were evaluated in an exposure of 61.8 kg ⋅ yr . No excess over background was found for all decay modes. The lower half-life limits of the 2 1 + state transitions of 0 ν β β and 2 ν β β decay were improved to T 1 / 2 0 ν ( 0 + → 2 1 + ) > 2.6 × 10 25 yr and T 1 / 2 2 ν ( 0 + → 2 1 + ) > 4.6 × 10 23 yr (90% C.L.), respectively. We report on the first experimental lower half-life limits for the transitions to the 0 1 + state of 136 Xe for 0 ν β β and 2 ν β β decay. They are T 1 / 2 0 ν ( 0 + → 0 1 + ) > 2.4 × 10 25 yr and T 1 / 2 2 ν ( 0 + → 0 1 + ) > 8.3 × 10 23 yr (90% C.L.). The transitions to the 2 2 + states are also evaluated for the first time to be T 1 / 2 0 ν ( 0 + → 2 2 + ) > 2.6 × 10 25 yr and T 1 / 2 2 ν ( 0 + → 2 2 + ) > 9.0 × 10 23 yr (90% C.L.). These results are compared to recent theoretical predictions. [ABSTRACT FROM AUTHOR]

The spectral-luminescent properties of a series of new functionally substituted dipyrrin fluoroborates (BODIPY) in acidified ethanol solutions are studied. The complex stabilities in the ground and excited states are estimated and the quantum yields of phototransformations on exposure to laser radiation are measured. [ABSTRACT FROM AUTHOR]

Symmetrical and unsymmetrical 4,4′-biphenyl, and 9,10-anthracene derivatives with tris(trifluoromethyl)germylethynyl –C C–Ge(CF 3 ) 3 substitutes have been prepared, their properties have been studied and compared with those of dimethyl(phenyl)silylethynyl –C C–Si(Ph)Me 2 compounds. UV–visible absorption, steady-state, and time-resolved fluorescence spectra in solution for this germanium and silicon compounds have been investigated. The process of photoinduced electron-transfer from the aromatic group to the germanium center has been found in the unsymmetrical 4-biphenyl –C C–Ge(CF 3 ) 3 molecule. Anthracene derivatives with –C C–Ge(CF 3 ) 3 substitutes have been characterized crystallographically. [ABSTRACT FROM AUTHOR]

Dicyanophenyl derivatives, DCN1 – 3 , were rationally synthesized and their thermally activated delayed fluorescence properties were investigated. OLED devices were further fabricated using DCN1 – 3 . Particularly DCN3 (5-{3,6-di(9 H -carbazole-9-yl)-9 H- carbazol-9-yl}isophthalonitrile) showed excellent device performances employing TADF mechanism with power efficiency of 15.26Cd/A, luminous efficiency of 8.14 lm/W, the maximum external quantum efficiency of 13.33%, and brightness of 1526 Cd/m 2 . [ABSTRACT FROM AUTHOR]

A comparison of excited state and electroluminescent properties between Pt(C^N^N)Cl and Pt(N^C^N)Cl complexes has been done with Time-Dependent Density Functional Theory (TDDFT), [C^N^N = 6-phenyl-2,2-bipyridine, N^C^N = 1,3-di(2-pyridyl)benzene]. The substituent effect of fluorine ligands on eight tridentate cyclometalated Pt(C^N^N)Cl complexes has been investigated, which includes electronic density variation between ground states and excited states, absorption and emission spectra, quantum yields and radiative lifetime. In addition, one dimeric form of Pt(C^N^N)Cl complex has been investigated. [ABSTRACT FROM AUTHOR]