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The photophysical properties of a series of recently synthesized single benzene fluorophores were investigated using ensemble density functional theory calculations. The energetic stability of the ground and excited state species were counterposed against the aromaticity index derived from local vibrational modes. It was found that the large Stokes shift of the fluorophores (up to ca. 5800 cm −1) originates from the effect of electron donating and electron withdrawing substituents rather than π‐delocalization and related (anti‐)aromaticity. On the basis of nonadiabatic molecular dynamics simulations, the absence of fluorescence from one of the regioisomers was explained by the occurrence of easily accessible S 1/S 0 conical intersections below the vertical excitation energy level. It is demonstrated in the manuscript that the analysis of local mode force constants and the related aromaticity index represent a useful tool for the characterization of π‐delocalization effects in π‐conjugated compounds. [ABSTRACT FROM AUTHOR]

The dynamics of excited‐state charge transfer (CT) in second near‐infrared (NIR‐II) fluorophore proceeds with conformational change that govern fluorescence. Unveiling the relationship between CT dynamics and conformational change in excited state is of great fundamental significance in optimizing NIR‐II fluorescence but remains less explored. This study unveils the pivotal role of large conformational change in promoting the evolution of emissive CT state into nonemissive CT state in NIR‐II fluorophore (CA‐BBT). Spectroscopic and computational results reveal that large conformational rotation/twisting leads to a pronounced increase in the CT character in excited state. This heightened CT character in CA‐BBT enables a rapid evolution of emissive CT state into a nonemissive CT state within 1.4 ps, as observed by ultrafast spectroscopy. Subsequently, this nonemissive state dominates nonradiative decay, resulting in very low NIR‐II fluorescence. Preventing such detrimental evolution by constraining the conformational dynamics of CA‐BBT results in a 10‐fold enhancement of NIR‐II fluorescence, enabling high‐resolution dynamic visualization of vasculature within osteosarcoma. This study offers a profound understanding of the relationship between CT dynamics and conformational changes in NIR‐II fluorescence, presenting innovative perspectives to develop bright NIR‐II fluorophores. [ABSTRACT FROM AUTHOR]

In this research, the ground (µg) and excited (µe) state dipole moments of metformin hydrochlorides were determined using Lippert-Mataga, Bakhshiev's, Kawski-Chamma-Viallet, and Reichardt models from fluorescence emission and UV-Vis absorption spectra in various solvents. From solvatochromic effects the calculated excited (µe) dipole moment of metformin hydrochloride were, 8.55 D, 8.34 D, 6.08 D, and 6.40 D using the Lippert-Mataga, Bakhshiev's, Kawski-Chamma-Viallet and Reichardt models respectively. The results also indicated that the dipole moment at the ground state is smaller than the excited state. This is due to solvent polarity having a stronger effect on fluorescence emission than absorption spectra. Similarly, from density functional theory, the calculated ground and excited states dipole moments of metformin hydrochloride using (DFT-B3LYP- 3-21+G*(μg = 10.02 D and μe = 11.94 D), DFT-B3LYP- 6-31+G (d, p) (μg = 8.44 D and μe = 10.87 D), and DFT-B3LYP- 6-311+G (d, p) (μg = 8.24 D and μe = 18.74 D)) analyzed by Gaussian 09W. From the optimized geometry of the molecule, the HOMO-LUMO energy band gap of metformin hydrochloride were computed using DFT [DFT-B3LYP- 3-21+G*(5.51 eV), DFT-B3LYP- 6-31+G (d, p) (5.66 eV), and DFT-B3LYP- 6-311+G (d, p) (5.70 eV)] respectively. [ABSTRACT FROM AUTHOR]

Aryl‐maleimides undergo a novel [2+4]‐photodimerization instead of the expected [2+2]‐photodimerization under both direct irradiation with visible light and under sensitized energy transfer conditions. This new excited state reactivity in aryl‐maleimides is deciphered through photochemical, photophysical, and spectroscopic studies. The stereochemistry of the photodimer depends on the type of non‐bonding interactions prevalent during photodimerization which is in turn dictated by the substituents on the maleimide ring. More importantly, the stereochemistry of the photodimer formed is complementary to the product observed under thermal conditions. [ABSTRACT FROM AUTHOR]

Aryl‐maleimides undergo a novel [2+4]‐photodimerization instead of the expected [2+2]‐photodimerization under both direct irradiation with visible light and under sensitized energy transfer conditions. This new excited state reactivity in aryl‐maleimides is deciphered through photochemical, photophysical, and spectroscopic studies. The stereochemistry of the photodimer depends on the type of non‐bonding interactions prevalent during photodimerization which is in turn dictated by the substituents on the maleimide ring. More importantly, the stereochemistry of the photodimer formed is complementary to the product observed under thermal conditions. [ABSTRACT FROM AUTHOR]

A series of reported Pt(II) carbene complexes possibly have the ability to serve as the new generation of blue emitters in luminescent devices because of their narrow emission spectra, high photoluminescence quantum yields (PLQYs), and rigid molecular skeleton. However, the combination of all carbene ligands with different multidentate structures will affect the overall planarity and horizontal dipole ratio to varying degrees, but the specific extent of this effect has not previously been analyzed in detail. In this work, density functional computation is used to study a class of platinum tetracarbene bidentate complexes with similar absorption and emission band characteristics, which is the main reason for the remarkable difference in quantum efficiency due to subtle differences in electronic states caused by different ligands. From the calculation results, the major reason, which results in significantly decrease in quantum efficiency for [Pt(cyim)2]2+, is that [Pt(cyim)2]2+ can reach the non-radiative deactivation metal-centered d-d excited state through an easier pathway compared with [Pt(meim)2]2+. The result, based on changes in the dihedral angle between ligands, can achieve the goal of improving and designing materials by adjusting the degree of the dihedral angle. (meim: bis(1,1′-dimethyl-3,3′-methylene-diimidazoline-2,2′-diylidene); cyim: bis(1,1′-dicyclohexyl-3,3′-methylene-diimidazoline-2,2′-diylidene). [ABSTRACT FROM AUTHOR]

spectral dependencies of the electroluminescence intensity of a microdisk laser with a diameter of 31 μm with active region based on InAs/InGaAs quantum dots, operating in the continuous-wave regime, are investigated in a wide range of injection currents. Simultaneous lasing through the ground and excited states of quantum dots under intense excitation is demonstrated in injection microdisk laser for the first time. At low pumping powers lasing occurs via ground states of quantum dots only. [ABSTRACT FROM AUTHOR]

The rationality of the minimum electrophilicity principle (MElP) as a companion of minimum polarizability principle and maximum hardness principle is studied for simple diatomic, triatomic, and tetratomic molecules. The applicability is further justified considering organic molecules (e.g., pyrene and acridine yellow) are known for their photophysical properties and accordingly their excited state properties. Single excitation CI (CIS) and time‐dependent density functional theory (TDDFT) are employed to study the excited state reactivity. Two types of excitations, namely vertical and adiabatic, are considered. Processes involving conservation and change in spin multiplicity are included during excitation. The general trend is that the molecules are less electrophilic in the ground state than those in the corresponding excited states. It is found that adiabatic excitation validates the principle even for the triplet ground state molecules undergoing an excitation where spin multiplicity gets altered. The TDDFT method explains the validity of the MElP augmenting the CIS method. This study echoed the MElP during molecular electronic excitation. [ABSTRACT FROM AUTHOR]

A photochemical synthetic method to access sulfones from aryl halides and sodium alkylsulfinates in the presence of CuCl is reported. Regio‐ and chemoselectivity for the sulfonylation is observed for polyhalogenated arenes. Mechanistic studies indicate that a copper sulfinate reagent is formed in situ from CuCl and sodium sulfinate based on NMR experiments. Potential reaction intermediates, including excited state aryl halides are studied using density functional theory calculations and reveal energetically accessible non‐planar triplet geometries. [ABSTRACT FROM AUTHOR]

Photo-controlled self-assembly of nanoparticles (NPs) is an advanced and promising approach to address a series of material issues from the molecular level to the nano/micro scale, owing to the fact that light stimulus is typically precise and rapid, and can provide contactless spatial and temporal control. The traditional photo-controlled assembly of NPs is based on photochemical processes through NPs modified by photo-responsive molecules, which are realized through the change in chemical structure under irradiation. Moreover, photoexcitation-induced assembly of NPs is another promising physical strategy, and such a strategy aims to employ molecular conformational change in the excited state (rather than the chemical structure) to drive molecular motion and assembly. The exploration and control of NP assembly through such a photo-controlled strategy can open a new paradigm for scientists to deal with "bottom-up" behaviors and develop unprecedented optoelectronic functional materials. [ABSTRACT FROM AUTHOR]

Donor–π–acceptor fluorophores that consist of an electron‐donating amino group and an electron‐accepting triarylborane moiety generally exhibit substantial solvatochromism in their fluorescence while retaining high fluorescence quantum yields even in polar media. Herein, we report a new family of this compound class, which bears ortho‐P(=X)R2‐substituted phenyl groups (X=O or S) as a photodissociative module. The P=X moiety that intramolecularly coordinates to the boron atom undergoes dissociation in the excited state, giving rise to dual emission from the corresponding tetra‐ and tricoordinate boron species. The susceptibility of the systems to photodissociation depends on the coordination ability of the P=O and P=S moieties, whereby the latter facilitates dissociation. The intensity ratios of the dual emission bands are sensitive to environmental parameters, including temperature, solution polarity, and the viscosity of the medium. Moreover, precise tuning of the P(=X)R2 group and the electron‐donating amino moiety led to single‐molecule white emission in solution. [ABSTRACT FROM AUTHOR]

Donor–π–acceptor fluorophores that consist of an electron‐donating amino group and an electron‐accepting triarylborane moiety generally exhibit substantial solvatochromism in their fluorescence while retaining high fluorescence quantum yields even in polar media. Herein, we report a new family of this compound class, which bears ortho‐P(=X)R2‐substituted phenyl groups (X=O or S) as a photodissociative module. The P=X moiety that intramolecularly coordinates to the boron atom undergoes dissociation in the excited state, giving rise to dual emission from the corresponding tetra‐ and tricoordinate boron species. The susceptibility of the systems to photodissociation depends on the coordination ability of the P=O and P=S moieties, whereby the latter facilitates dissociation. The intensity ratios of the dual emission bands are sensitive to environmental parameters, including temperature, solution polarity, and the viscosity of the medium. Moreover, precise tuning of the P(=X)R2 group and the electron‐donating amino moiety led to single‐molecule white emission in solution. [ABSTRACT FROM AUTHOR]

Helicenes are an interesting scaffold for chiroptical properties and in particular circularly polarized luminescence (CPL). In this short review, we collect the luminescence (glum) and absorption (gabs) dissymmetry factors associated to the first Cotton effect of the electronic circular dichroism (ECD) spectrum. Considering the data for 170 [n]‐helicenes (n = 4–11), overall we found reasonable correlations between glum and gabs. Despite a few notable exceptions, this would confirm a similarity in the stereochemistry of the ground and emitting excited states for most helicenes. These results may be useful in rationalizing chiroptical data and help chemists in designing new helicene structures with the desired CPL properties. [ABSTRACT FROM AUTHOR]

Pressure‐induced emission (PIE) associated with self‐trapping excitons (STEs) in low‐dimensional halide perovskites has attracted great attention for better materials‐by‐design. Here, using 2D layered double perovskite (C6H5CH2CH2NH3+)4AgBiBr8 as a model system, we advance a fundamental physicochemical mechanism of the PIE from the perspective of carrier dynamics and excited‐state behaviors of local lattice distortion. We observed a pressure‐driven STE transformation from dark to bright states, corresponding a strong broadband Stokes‐shifted emission. Further theoretical analysis demonstrated that the suppressed lattice distortion and enhanced electronic dimensionality in the excited‐state play an important role in the formation of stabilized bright STEs, which could manipulate the self‐trapping energy and lattice deformation energy to form an energy barrier between the potential energy curves of ground‐ and excited‐state, and enhance the electron‐hole orbital overlap, respectively. [ABSTRACT FROM AUTHOR]

It is shown that, like conventional diffuse fluorescence spectra and despite the complex mechanism of formation of the excited state, the chemi- and bioluminescence spectra contain information about the frequency of the purely electronic (vertical) transition of the emitting molecules and the degree of homogeneity of their ensemble. As in the case of ordinary diffuse luminescence spectra, the frequency of a purely electronic transition is shifted significantly toward the short wavelength side (by almost the half-width of the band) from the maximum of the fluorescence spectrum. An example of the separation of the overlapping spectra using the position of a short-wavelength purely electronic transition is presented. [ABSTRACT FROM AUTHOR]

The theoretical investigation of excited state for large photoactive systems plays the fundamental role in understanding various optical processes in material and biological system. Frenkel exciton (FE) model describing the excitation of the whole system as a collective effect of quasi‐particles of excitons, that is, bound electron–hole pairs, is well‐known as a simple but powerful theoretical scheme to present a clear and insightful physical picture for complicated excited state problems. In this mini‐review, we summarize our recent developments of quantum chemical methods based on exciton models and their related applications for large photoactive systems. It is shown that our developed ab initio renormalized exciton model (REM) and block interaction product state (BIPS) schemes provide new efficient and automatic low‐scaling excited state methods for both localized and delocalized excited states in large systems. Illustrative examples including simulations of both absorption and emission spectrum in large sized molecular aggregates, indicate the exciton model based methods provide promising computational tools for unravel the mechanism of photophysical and photochemical processes in large photoactive systems. [ABSTRACT FROM AUTHOR]

We report on accurate variational calculations of the Born–Oppenheimer potential for excited states of the hydrogen molecule with Π , Δ , and Φ symmetries. The obtained potential energy curves reach the relative precision of 10 − 9 or better along internuclear distances of 0.01–20 au. Calculations rely on the recursive evaluation of two-centre two-electron molecular integrals with exponential functions in arbitrary precision arithmetics. Our results for most of the states are the first-ever reported, and for the previously calculated states constitute an improvement by several orders of magnitude. [ABSTRACT FROM AUTHOR]

CS molecule, which plays a key role in atmospheric and astrophysical circumstances, has drawn great attention for long time. Owing to its large state density, the detailed information of the electronic structure of CS is still lacking. In this work, the high-level MRCI+ Q method is used to compute the potential energy curves, dipole moments and transition dipole moments of singlet and triplet states correlated with the lowest dissociation limit of CS, based on which high accurate vibrationâ€"rotation levels and spectroscopic constants of bound states are evaluated. The opacity of CS relevant to atmospheric circumstance is computed at a pressure of 100 atms for different temperatures. With the increase of temperature, band systems from different transitions mingle with each other, and band boundaries become blurred, which are originated from the increased population on vibrational excited states and electronic excited states at high temperature. [ABSTRACT FROM AUTHOR]

Photosensitization associated with electron/energy transfer represents the central science of natural photosynthesis. Herein, we proposed a protocol to dramatically improve the sensitizing ability of metal–organic frameworks (MOFs) by switching their excited state distribution from 3MLCT (metal‐to‐ligand charge transfer) to 3IL (intraligand). The hierarchical organization of 3IL MOFs and Co/Cu catalysts facilitates electron transfer for efficient photocatalytic H2 evolution with a yield of 26 844.6 μmol g−1 and CO2 photoreduction with a record HCOOH yield of 4807.6 μmol g−1 among all the MOF photocatalysts. Systematic investigations demonstrate that strong visible‐light‐absorption, long‐lived excited state and ingenious multi‐component synergy in the 3IL MOFs can facilitate both interface and intra‐framework electron transfer to boost photocatalysis. This work opens up an avenue to boost solar‐energy conversion by engineering sensitizing centers at a molecular level. [ABSTRACT FROM AUTHOR]

Photosensitization associated with electron/energy transfer represents the central science of natural photosynthesis. Herein, we proposed a protocol to dramatically improve the sensitizing ability of metal–organic frameworks (MOFs) by switching their excited state distribution from 3MLCT (metal‐to‐ligand charge transfer) to 3IL (intraligand). The hierarchical organization of 3IL MOFs and Co/Cu catalysts facilitates electron transfer for efficient photocatalytic H2 evolution with a yield of 26 844.6 μmol g−1 and CO2 photoreduction with a record HCOOH yield of 4807.6 μmol g−1 among all the MOF photocatalysts. Systematic investigations demonstrate that strong visible‐light‐absorption, long‐lived excited state and ingenious multi‐component synergy in the 3IL MOFs can facilitate both interface and intra‐framework electron transfer to boost photocatalysis. This work opens up an avenue to boost solar‐energy conversion by engineering sensitizing centers at a molecular level. [ABSTRACT FROM AUTHOR]

Maximum overlap methods are effective tools for optimizing challenging ground‐ and excited‐state wave functions using self‐consistent field models such as Hartree‐Fock and Kohn‐Sham density functional theory. Nevertheless, such models have shown significant sensitivity to the user‐defined initial guess of the target wave function. In this work, a projection operator framework is defined and used to provide a metric for non‐aufbau orbital selection in maximum‐overlap‐methods. The resulting algorithms, termed the Projection‐based Maximum Overlap Method (PMOM) and Projection‐based Initial Maximum Overlap Method (PIMOM), are shown to perform exceptionally well when using simple user‐defined target solutions based on occupied/virtual molecular orbital permutations. This work also presents a new metric that provides a simple and conceptually convenient measure of agreement between the desired target and the current or final SCF results during a calculation employing a maximum‐overlap method. [ABSTRACT FROM AUTHOR]

The protolytic equilibrium of the excited states of fluorescein depends not only on the equilibrium in the ground state, but also on the efficiency of photoexcitation, relaxation, and proton transfer in the excited state. Due to rate-competing radiative and non-radiative processes occurring in a mixture of protolytic forms, there is still a problem of identifying the fluorescent characteristics of individual forms of fluorescein. In this work, the steady-state distribution of the concentrations of the ground and excited states of the cation, a number of tautomers of the neutral form, monoanion, and dianion of fluorescein under continuous photoexcitation was simulated. The pH values of the predominant existence of individual protolytic forms in the excited states were determined, which were confirmed by steady-state fluorescence measurements. Possible reasons for the discrepancies in the published data on the fluorescent properties of individual protolytic forms of fluorescein are discussed and refined data on the spectral shapes and lifetimes of the quinoid and monoanion of fluorescein are obtained. [ABSTRACT FROM AUTHOR]

The formulations and performances of spin‐restricted ensemble‐referenced KS and mixed‐reference spin‐flip time‐dependent density functional theory incorporating strong correlations into density functional theories are documented. As a result of balanced dynamic and nondynamic correlation, they are capable of describing strongly correlated challenging systems including diradicals, bond dissociation, conical intersections, doubly excited states, and so on, overcoming the limitations of current density functional theories. [ABSTRACT FROM AUTHOR]

Organic light‐emitting diodes (OLEDs) represent one of the most promising technologies for future displays and lighting sources, which have received extensive research attention. Purely organic thermally activated delayed fluorescence (TADF) emitters offer obvious advantages, including high efficiencies and low costs, and they are typically doped in host materials to achieve optimal device efficiencies. TADF emitters typically feature intramolecular charge transfer characteristics, and their excited states properties are sensitive to local environment, giving the implication that host materials can finely tune their emission properties. In recent years, the development of TADF emitters has been vigorous with abundant and fast‐growing reports on new design concepts and molecular structures. Comparatively, research on the host materials for TADF OLEDs has lagged, and reports on host materials, especially those providing insights into host‐dopant interactions are limited. This subject is at the interface of synthetic chemistry, physical chemistry, solid‐state physics, and computational modeling, etc. In this review article, current basic understanding of TADF and the reports on the impact of host materials on the photophysical properties/device performance of TADF emitters are reviewed to provide insights into the host‐dopant interactions, aiming to draw the attention of the research community from optoelectronics toward developing highly efficient TADF OLEDs. [ABSTRACT FROM AUTHOR]

The excited state dipole moments of two positional isomers of dicyanobenzene have been determined from thermochromic shifts of the absorption and fluorescence emission spectra in ethyl acetate solution and compared to the results of ab initio calculations. We found that the dipole moments of excited states from thermochromic shifts closely resemble the ab initio values of the isolated molecule, while the results of conductor-like screening model (COSMO) using the same wave function model as for the isolated molecule, shows considerable deviations from the experimental values. It is shown that the dipole moments of the two cyano groups add up vectorially for both the ground and excited states. • Dipole moment of two isomeric dicyanobenzenes determined in ground and excited state from thermochromic shifts. • Comparison of the experimental results to SCS-CC2 calculations shows a very good agreement for excited state dipole moments of the isolated molecules. • Bad agreement with the results of COSMO calculations. • Additivity rule for dipole increments works in the ground state and the excited state. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • New photoinduced decay mechanism of 3-OH-SMA system was proposed. • The decay channel is mainly driven by the C7 = N1 bond twisting motion. • The excited state intramolecular proton transfer process is not involved in 3-OH-SMA system. Schiff bases stand out as a highly significant class of photochromic materials with widespread applications. The exploration of their photochromic mechanisms has garnered substantial interest over the past decades. In this work, we investigated the photochromic mechanism of 3-hydroxy-salicylidene methylamine (3-OH-SMA) by high-level electronic structure calculations and on-the-fly excited state dynamics simulations. Our investigation revealed the identification of three minimum energy conical intersections between S 1 and S 0 states, while only the one characterized by the central C = N bond twisting motion was involved in the deactivation process. This finding contrasts with previous reports, suggesting that the excited state intramolecular proton transfer (ESIPT) process was the main reaction channel in 3-OH-SMA. The proposed new decay mechanism provides valuable theoretical insights, paving the way for the further enhancement or rational design of photochromic materials. [ABSTRACT FROM AUTHOR]

Properties of 0+ excited states generated by pairing and quadrupole-quadrupole forces in some rare-earth isotopes are investigated. Energies of the 0+ states, probabilities of the E(0) and E(2) transitions, Rasmussen parameters X, and effective cross sections of two-nucleon transfer reactions have been calculated taking into account mixing of the excited states with different Kπ values. The contribution of mixing of the excited states underestimates values of the calculated physical quantities. [ABSTRACT FROM AUTHOR]

The simultaneous quantum-chemical and spectral investigations of the possible relaxation pathways in the excited state for the two α,ω-di-substituted polyenes were performed. Lengthening of the polymethine chain is accompanied by the considerable decreasing of the first electron transition and hence is manifested as the bathochromic shift of both absorption and fluorescence spectra; however, the nature of transition does not change. It is established that the considerable changes of the bond lengths in polymethine chain for both vinylogs in the excited state cause firstly the appearance of the fast component in short wavelengths spectral region; after relaxation, the intensity of the fast component decreases, and it disappears, but then the spectral band, shifted bathochromically, appears, so that its maximum coincide with the band maximum in the steady-state fluorescence maximum, what corresponds to the final symmetrical relaxation of bond lengths. The parallel quantum-chemical calculation shows that two highest levels are mainly formed by the donor levels of both terminal groups and hence twice occupied splitting levels. Upon excitation, one of the splitting MO (HOMO) becomes single occupied; this causes the molecule in the excited state to be unstable and could transform it to the unsymmetrical form. Such relaxation path is confirmed by the time-resolved spectra: the spectral band in both molecules, with the different polymethine chains, undergoes the subsequent bathochromical shifting. [ABSTRACT FROM AUTHOR]

For the 5D energy-critical wave equation, we construct excited N -solitons with collinear speeds, i.e. solutions u of the equation such that lim t → + ∞ ∇ t , x u (t) − ∇ t , x ∑ n = 1 N Q n (t) L 2 = 0 , where for n = 1 , ... , N , Q n (t , x) is the Lorentz transform of a non-degenerate and sufficiently decaying excited state, each with different but collinear speeds. The existence proof follows the ideas of Martel–Merle [Construction of multi-solitons for the energy-critical wave equation in dimension 5, Arch. Ration. Mech. Anal.222(3) (2016) 1113–1160] and Côte–Martel [Multi-travelling waves for the nonlinear Klein–Gordon equation, Trans. Amer. Math. Soc.370(10) (2018) 7461–7487] developed for the energy-critical wave and nonlinear Klein–Gordon equations. In particular, we rely on an energy method and on a general coercivity property for the linearized operator. [ABSTRACT FROM AUTHOR]

The ground and lowest singlet excited state geometries of selected (para -C5H4X)Ir(PH3)3 iridabenzene complexes (para -substituent = NH2, OMe, Me, H, F, Cl, CCl3, CF3, NO2) are optimized using the MPW1PW91 procedure employing the LanL2DZ(Ir) and 6-311G(d, p) (C, H, N, O, P, F, Cl, P) basis sets. The excited state is generated using the time-dependent density function method. The effects of electron-donating groups and electron-withdrawing groups on the energy, atomization energy, rotational constants, and frontier orbital energies in the first singlet excited state (S1) of iridabenzene are investigated and compared to those of the ground state (S0). The Ir–C and Ir–P bonds in the studied molecules are analyzed by electron localization function and localized-orbital locator methods. The correlations between the Ir-C and Ir–P bond distances, electron localization function, and localized-orbital locator values Hammett constants (σp) and dual parameters (σI and σR) are given for the two studied states. The para -delocalization index is used for investigation of the aromaticity of the studied complexes. [ABSTRACT FROM AUTHOR]

To investigate substitution effects on excited-state intermolecular proton transfer (ESPT) reactions as well as acidity of proton donating fragments in the ground state, we synthesized substituted anthracen-2-yl-3-phenylurea derivatives that form a hydrogen bonds with acetate anions and undergo ESPT reaction. Fluorescence lifetime measurements and their kinetic analyses revealed that the trifluoromethyl group on the phenyl ring as an electron-withdrawing group caused a slow ESPT reaction despite an increase in the acidity of the N–H fragment in the ground state. In contrast, the methoxy group as a donating group leads to a fast ESPT reaction despite a reduction of the acidity of the N–H fragment in the ground state. These effects of substituents on ESPT reaction are due to their influence on the charge transfer reaction, which occurs from the N–H fragment to the anthryl ring to increase the acidity of N–H followed by ESPT reaction, over the urea unit by a combination of resonance and inductive effects. These opposing effects of substituents on the acidity of the urea unit in the ground and excited states provide an important insight in balancing the reactivity of proton transfer reaction in both the excited and ground states. [ABSTRACT FROM AUTHOR]

Soft lattice and strong exciton–phonon coupling have been demonstrated in layered double perovskites (LDPs) recently; therefore, LDPs represents a promising class of compounds as excellent self‐trapped exciton (STE) emitters for applications in solid‐state lighting. However, few LDPs with outstanding STE emissions have been discovered, and their optoelectronic properties are still unclear. Based on the three‐dimensional (3D) Cs2NaInCl6, we synthesized two 2D derivatives (PEA)4NaInCl8:Sb (PEA=phenethylamine) and (PEA)2CsNaInCl7:Sb with monolayer and bilayer inorganic sheets by a combination of dimensional reduction and Sb‐doping. Bright broadband emissions were obtained for the first time under ambient temperature and pressure, with photoluminescence quantum efficiency (PLQE) of 48.7 % (monolayer) and 29.3 % (bilayer), superior to current known LDPs. Spectroscopic characterizations and first‐principles calculations of excited state indicate the broadband emissions originate from STEs trapped at the introduced [SbCl6]3− octahedron. [ABSTRACT FROM AUTHOR]

Soft lattice and strong exciton–phonon coupling have been demonstrated in layered double perovskites (LDPs) recently; therefore, LDPs represents a promising class of compounds as excellent self‐trapped exciton (STE) emitters for applications in solid‐state lighting. However, few LDPs with outstanding STE emissions have been discovered, and their optoelectronic properties are still unclear. Based on the three‐dimensional (3D) Cs2NaInCl6, we synthesized two 2D derivatives (PEA)4NaInCl8:Sb (PEA=phenethylamine) and (PEA)2CsNaInCl7:Sb with monolayer and bilayer inorganic sheets by a combination of dimensional reduction and Sb‐doping. Bright broadband emissions were obtained for the first time under ambient temperature and pressure, with photoluminescence quantum efficiency (PLQE) of 48.7 % (monolayer) and 29.3 % (bilayer), superior to current known LDPs. Spectroscopic characterizations and first‐principles calculations of excited state indicate the broadband emissions originate from STEs trapped at the introduced [SbCl6]3− octahedron. [ABSTRACT FROM AUTHOR]

Predicting the energetics of chemical transformations requires localizing stationary points on a potential energy surface. While educts and products of a chemical reaction may be known, transition state optimization is challenging as good guesses may be unavailable. Extending stationary point searches to the excited state leads to additional difficulties as several states may be close in energy, requiring efficient state tracking. Here, we report the implementation of pysisyphus, an external optimizer, that allows localization of stationary points not only in the ground state but also for excited state by providing several state‐tracking algorithms. pysisyphus offers all necessary tools for calculating reaction paths, starting from the optimization of the reactants, running chain‐of‐states methods such as the nudged elastic band or the growing string method with subsequent transition state optimization, and a concluding intrinsic reaction coordinate calculation. [ABSTRACT FROM AUTHOR]

This article, titled "Innentitelbild: Dithienoazepine-Based Near-Infrared Dyes: Janus-Faced Effects of a Thiophene-Fused Structure on Antiaromatic Azepines," discusses a design strategy for creating near-infrared (NIR) dyes using antiaromatic azepine. The authors, Masahito Murai, Takahiro Enoki, and Shigehiro Yamaguchi, explain that while benzo-fused azepines have bent conformations that become planar in the excited state, thieno-fused azepines with electron-accepting groups remain flat even in the ground state, resulting in NIR emissions beyond 850 nm. The article includes cover art by Dr. Issey Takahashi at ITbM, Nagoya University. [Extracted from the article]

This article, titled "Inside Cover: Dithienoazepine-Based Near-Infrared Dyes: Janus-Faced Effects of a Thiophene-Fused Structure on Antiaromatic Azepines," discusses a design strategy for creating near-infrared (NIR) dyes using antiaromatic azepine. The authors, Masahito Murai, Takahiro Enoki, and Shigehiro Yamaguchi, explain that while benzo-fused azepines have bent conformations that become planar in the excited state, thieno-fused azepines with electron-accepting groups remain flat even in the ground state, resulting in NIR emissions beyond 850 nm. The article includes cover art by Dr. Issey Takahashi at ITbM, Nagoya University. [Extracted from the article]

• Both radical and non-radical processes have a synergistic effect on DMT dephosphorization. • The hydroxyl radical alone is insufficient for the complete dephosphorization of DMT. • The exposure of DMT to UV 185 enhances its vulnerability to radical assault. • Singlet oxygen atoms O(1D) demonstrates remarkable selectivity towards P = S bonds. • The role of non-radical processes varies depending on the molecular structure. Organophosphorus pesticides are extensively utilized worldwide, but their incomplete dephosphorization poses significant environmental risks. This study investigates the dephosphorization of dimethoate (DMT), a representative organophosphorus pesticide, using a vacuum ultraviolet system. Surprisingly, in addition to hydroxyl radicals (•OH), non-radical processes such as photoexcitation and singlet oxygen atoms (O(1D)) exert more significant effects on DMT dephosphorization. The degradation kinetics of DMT demonstrate a perfect linear correlation with the radical yield in both UV-based and VUV-based advanced oxidation processes (AOPs), with greater efficacy of radical attack observed in the VUV system. This heightened efficiency is attributed to the excitation of DMT to a high-energy excited state induced by UV 185 radiation. Additionally, •OH alone is inadequate for achieving complete dephosphorization of DMT. The Fukui index and singly occupied orbital (SOMO) analysis reveal that the O(1D) generated by UV 185 -induced photolysis of O 2 exhibits exceptional selectivity towards P=S bonds, thereby playing an indispensable role in the dephosphorization process of DMT. This study highlights the significant contribution of non-radical pathways in DMT dephosphorization by VUV, which holds great implications for the advancement of photochemical-based AOPs. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • The excited states of three blue emitters are manipulated from CT to HLCT. • Blue vacuum-evaporated HLCT OLEDs exhibit maximum EQE of 7.52%. • The solution-processed HLCT OLED shows a high maximum EQE of 6.49%. • Very low efficiency roll-offs of 0.8% and 3.7% at 100 and 1000 cd m−2 are achieved. Manipulating the excited states of organic luminescent materials can efficiently improve the utilization of both singlet and triplet excitons for developing high-performance organic light-emitting diodes (OLEDs), but the issue remains difficult due to the lack of well-controlled ways. Here, we proposed a molecular design strategy of excited state manipulation from charge-transfer (CT) to hybridized local and charge-transfer (HLCT) via adjusting the cyano position on pyridine acceptor. The meta -substituted PyAn4CN is mainly composed of a CT component, while the para -substituted PyAn5CN is endowed with a HLCT component. On further extending the conjugation of PyAn5CN by inserting a benzene unit between the pyrene and anthracene core, the HLCT character is preserved in PyPhAn5CN , accompanied by a faster radiative decay. Consequently, the vacuum-evaporated OLEDs exhibit blue electroluminescence (EL) with the emission peaks in the range of 455–460 nm and high external quantum efficiency (EQE) up to 7.52%, together with well-suppressed efficiency roll-offs of 0.8% and 3.7% at the luminance of 100 and 1000 cd m-2, respectively. More importantly, the solution-processed device shows an excellent performance with EQE of 6.49%, which is one of the best results in the solution-processed HLCT OLEDs. Our results clearly indicate that the formation of HLCT state is an efficient way to realize high-efficiency blue electrofluorescence. [ABSTRACT FROM AUTHOR]

A simple structural comparison method based on relative changes of internal coordinates among different electronic states is presented. As such, any electronic state with respect to the ground state could be represented as a point on two dimensions. Although this analysis is not based on quantum mechanically "correct" description of molecules based on electron density and thus employs geometries rather than topologies, it might have advantages over overlaying procedures in resolving small differences as well as quantification of similarity/dissimilarity. More importantly correlations of structural similarity with luminescence properties were discussed for popular π-chromophores by studying S0, S1, and T1 states of indole, coumarin, BODIPY, and naphthalene. A qualitative difference on the structural similarity plane in spanning of S0 → S1 and S0 → T1 coordinate deformation vectors for popular fluorophores was identified. This emphasized a well-protected/separated S1 state to be a key feature of an efficient fluorophore. Our calculations on excited states suggest that, a quick screening of structure–luminescence relationships is possible. Structural features of efficient fluorophores outlined in this work can hopefully help rational designing of chromophore cores with desired luminescence properties. [ABSTRACT FROM AUTHOR]

Push‐pull dibenzodioxins with electron withdrawing and donating groups were prepared in good yields through a short and simple synthesis. Strong green emission above 500 nm occurs in those derivatives where there is maximum charge transfer to the most electron deficit terephthalonitrile ring, from proximal cyclic amino donor groups. Theoretical calculations support experimental findings through evaluation of excited state properties. In molecules with a nitro group, the excited state localizes electron density exclusively onto it and twisted nitro geometry was also found. In effect, electronic charge cannot relocate into the molecular plane, rendering them non‐fluorescent. Also, studies on the fluorescent derivatives show that best emission would occur when the donor moiety contains a saturated cyclic amino ring and the amines are 2°. Overall, our study establishes structure‐property guidelines and limits on dibenzodioxin functionalization towards preparing fluorescent derivatives of the same. [ABSTRACT FROM AUTHOR]

Inspired by nature, improving photosensitization represents a vital direction for the development of artificial photosynthesis. The sensitization ability of photosensitizers (PSs) reflects in their electron-transfer ability, which highly depends on their excited-state lifetime and redox potential. Herein, for the first time, we put forward a facile strategy to improve sensitizing ability via finely tuning the excited state of Ru(II)-PSs (Ru-1 – Ru-4) for efficient CO2 reduction. Remarkably, [Ru(Phen)2(3-pyrenylPhen)]2+ (Ru-3) exhibits the best sensitizing ability among Ru-1 – Ru-4 , over 17 times higher than that of typical Ru(Phen)32+. It can efficiently sensitize a dinuclear cobalt catalyst for CO2-to-CO conversion with a maximum turnover number of 66 480. Systematic investigations demonstrate that its long-lived excited state and suitable redox driving force greatly contributed to this superior sensitizing ability. This work provides a new insight into dramatically boosting photocatalytic CO2 reduction via improving photosensitization. [ABSTRACT FROM AUTHOR]

Squaraines (SQs) with tunable emission in the solid state is of great importance for various demands; however a remaining challenge is emission quenching upon aggregation. Herein, a unique SQ, named as CIEE‐SQ, is designed to exhibit strong emission in crystal, undergoing crystallization‐induced reverse from dark 1(n+σ,π*) to bright 1(π,π*) excited states. Such an excited state of CIEE‐SQ can be subtly tuned by molecular conformation changes during the unexpected temperature‐triggered single‐crystal to single‐crystal (SCSC) reversible transformation. Furthermore, co‐crystallization between CIEE‐SQ and chloroform largely stabilize the 1(π,π*) state, enhancing the transition dipole moment and decreasing the reorganization energy to boost the fluorescence, which is promising in data encryption and decryption. [ABSTRACT FROM AUTHOR]

All‐electron fixed‐node diffusion quantum Monte Carlo energies of the two lowest‐lying states of C, N, O, F, and Ne atoms are reported. The Slater‐Jastrow form is used as the trial wave function. We will use single‐ and multideterminant wave functions as the Slater part. The single‐determinant wave function has been computed by the Hartree‐Fock method and the multideterminant wave functions have been computed by the complete active space self‐consistent field, configuration interaction with single and double excitation, configuration interaction with single, double, triple, and quadruple excitation and second‐order configuration interaction. For the ground‐ and first excited states, the multideterminant wave functions have computed more than 99% of the correlation energy. Significant improvements have been achieved using the backflow transformations and up to 99.8% of the correlation energy has been recovered. A very good agreement with the experimental data has been obtained for the excitation energies. [ABSTRACT FROM AUTHOR]

A new facial homoleptic tris‐cyclometalated phosphorescent iridium(III) complex Ir(ppyNO)3 featuring three oxygen‐bridged triarylamine units has been synthesized via an efficient Suzuki–Miyaura cross‐coupling reaction of oxygen‐bridged triarylamine unit based boron reagent 1‐b with corresponding tribrominated iridium(III) complex Ir‐Br. It can not only show an effective green light emission, but also display a narrower full width at half maximum (FWHM=57 nm) and better solubility than that of the classical complex fac‐Ir(ppy)3 (FWHM=82 nm, ppy=2‐phenylpyridine). Furthermore, a longer emission lifetime (τ=1201 ns) of Ir(ppyNO)3 in polystyrene (PS) film can be found than that (τ=45 ns) in CH2Cl2 solution. In addition, the lowest triplet state (T1) of Ir(ppyNO)3 can exhibit both metal‐to‐ligand charge transfer (3MLCT) and intraligand charge transfer (3ILCT) excited state character according to DFT calculations. [ABSTRACT FROM AUTHOR]

Details concerning the energetics and structure of the ion pair in gaseous chloroethane, obtained at the multi-reference configuration interaction with singles and doubles (MR-CISD) level, are given. It is formed in the third excited state (31A′), and it can be classified as a hydrogen-bonded contact ion pair, although from its total binding energy of 3.28 eV (including extensivity corrections, at the MR-CISD + Q level with the aug-cc-pVTZ basis set, and including zero-point energy corrections) only 0.14 eV is due to an underlying hydrogen bond. It is a highly polar structure, with a dipole moment of 9.56 D. As compared to previous systems for which the same type of bond has been observed, it has a much lower hydrogen-bond energy and a much larger distance between the charge centers. The three lowest frequency vibrational modes of the HBCIP correspond to intermolecular cation–anion modes. The structure here obtained brings important structural questions for HCFCs derived from chloroethane. [ABSTRACT FROM AUTHOR]

In this paper, we study the ground and first excited states of the fractional Bose–Einstein condensates (BEC) which is modeled by fractional Gross–Pitaevskii (GP) equation. We first introduce the normalized gradient flow method and prove its energy diminishing property. Then the weighted shifted Grünwald–Letnikov difference (WSGD) method is used to discretize the Gross–Pitaevskii equation. The corresponding normalization and energy diminishing property for the semi-discrete scheme are proved. For the time discretization, we use the implicit integration factor (IIF) method which decouples the diffusion and nonlinear terms separately. Finally the numerical methods are applied to compute the ground and first excited states of fractional BEC with harmonic oscillator, harmonic-plus-optical lattice and box potential. Our numerical results show that the ground and excited states in fractional GP equation differ from those of the standard (non-fractional) GP equation. [ABSTRACT FROM AUTHOR]

A study on C9‐imide acridinium photocatalysts with enhanced photoredox catalytic activity with respect to the well‐established C9‐mesityl acridinium salt is presented. The differences observed rely on the diverse accessibility of singlet charge‐transfer excited states, which have been proven by CASPT2/CASSCF calculations, fluorescence and quenching studies. [ABSTRACT FROM AUTHOR]

[Display omitted] • The excited state behavior of a group of newly developed fluoropurine analogues of aza-heterocycles, triazole pyrimidinyl fluorophores, has been comprehensively studied. • The reaction energy profiles indicate that ESIPT is difficult to happen. The large Stokes shift of the fluorophores, therefore, is reconsidered. • Based on the FMOs results, the large Stokes shift is attributed to an ICT process occurring in the excited state, the rationality of which is further confirmed by the fluorescence spectra results. Fluoropurine analogues are a kind of unnatural bases, which are widely used in chemistry, biological science, pharmacy and other fields. At the same time, fluoropurine analogues of aza-heterocycles play an important role in medicinals research and development. In this work, the excited state behavior of a group of newly developed fluoropurine analogues of aza-heterocycles, triazole pyrimidinyl fluorophores, was comprehensively studied. The reaction energy profiles indicate that excited state intramolecular proton transfer (ESIPT) is difficult to happen, which is further proved by fluorescent spectra results. This work proposed a new and reasonable fluorescence mechanism based on the original experiment, and found that the large Stokes shift of the triazole pyrimidine fluorophore is due to the intramolecular charge transfer (ICT) process of the excited state. Our new discovery is of great significance for the application of this group of fluorescent compounds in other fields and the regulation of fluorescence properties. [ABSTRACT FROM AUTHOR]

Vacuum ultraviolet (VUV) based advanced oxidation processes (AOPs) recently attracted widespread interests. However, the role of UV 185 in VUV is only considered to be generating a series of active species, while the effect of photoexcitation has long been overlooked. In this work, the role of UV 185 induced high-energy excited state for the dephosphorization of organophosphorus pesticides was studied using malathion as a model. Results showed malathion degradation was highly related to radical yield, while its dephosphorization was not. It was UV 185 rather than UV 254 or radical yield that was responsible for malathion dephosphorization by VUV/persulfate. DFT calculation results demonstrated that the polarity of P-S bond was further increased during UV 185 excitation, favoring dephosphorization while UV 254 did not. The conclusion was further supported by degradation path identification. Moreover, despite the fact that anions (Cl-, SO 4 2- and NO 3 -) considerably affected radical yield, only Cl- and NO 3 - with high molar extinction coefficient at 185 nm significantly affected dephosphorization. This study shed light on the crucial role of excited states in VUV based AOPs and provided a new idea for the development of mineralization technology of organophosphorus pesticides. [Display omitted] • High-energy excited states rather than radical yield dominated OPs mineralization. • Photoexcitation altered the regioselectivity of radical attack. • UV 185 weakened P–S bond, which decided dephosphorization, while UV 254 cannot. • Anions affected mineralization via UV 185 absorption rather than radical quenching. [ABSTRACT FROM AUTHOR]

[Display omitted] Comparative investigation of temperature dependences of the fast and slow fluorescence decay components in an aqueous solution of tryptophan molecules, frozen in the light and in the dark, was made in the range of –170 °C to + 20 °C. A quantitative analysis of the model of direct and reverse electronic transitions in tryptophan molecule from an excited state to the ground state and to the charge transfer state (CTS) was carried out. Three main spectral regions of tryptophan fluorescence are distinguished that differ in behavior of temperature dependences of the transition rates from the excited state of tryptophan to CTS. The key role of the hydrogen bond system dynamics determining the nonlinear behavior of tryptophan fluorescence parameters in the selected spectral regions is shown. The nonlinear behavior of the fluorescence lifetime, position and shape of fluorescence spectra with changing temperature is determined by tryptophan interaction with an aqueous medium. Besides, the rate of solvation shift of fluorescence spectra is observed. The important role of temperature rearrangements in the system of hydrogen bonds of the water solution surrounding the tryptophan molecule in the excited state is shown. The obtained results can be used to explain the key role of hydrogen bonds in the processes of charge transfer and energy migration in biological systems. [ABSTRACT FROM AUTHOR]