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This paper explores a novel group of D-π-A configurations that has been specifically created for organic solar cell applications. In these material compounds, the phenothiazine, the furan, and two derivatives of the thienyl-fused IC group act as the donor, the π-conjugated spacer, and the end-group acceptors, respectively. We assess the impact of substituents by introducing bromine atoms at two potential substitution sites on each end-group acceptor (EG1 and EG2). With the donor and π-bridge held constant, we have employed density functional theory and time-dependent DFT simulations to explore the photophysical and optoelectronic properties of tailored compounds (M1–M6). We have demonstrated how structural modifications influence the optoelectronic properties of materials for organic solar cells. Moreover, all proposed compounds exhibit a greater Voc exceeding 1.5 V, a suitable HOMO-LUMO energy gap (2.14–2.30 eV), and higher dipole moments (9.23–10.90 D). Various decisive key factors that are crucial for exploring the properties of tailored compounds—frontier molecular orbitals, transition density matrix, electrostatic potential, open-circuit voltage, maximum absorption, reduced density gradient, and charge transfer length (Dindex)—were also explored. Our analysis delivers profound insights into the design principles of optimizing the performance of organic solar cell applications based on halogenated material compounds. [ABSTRACT FROM AUTHOR]

We report absolute high-resolution vacuum ultraviolet (VUV) photoabsorption cross-sections of carbon tetrachloride (CCl4) in the photon energy range 5.0–10.8 eV (248–115 nm). The molecular spectrum and electronic structure have been comprehensively investigated together with quantum chemical calculations, providing geometries, bond lengths, vertical excitation energies and oscillator strengths. The major electronic excitations have been assigned to valence and Rydberg transitions which are also accompanied by vibrational excitation assigned to degenerate stretching, v 3 ′ t 2 and degenerate deformation v 4 ′ t 2 modes. The rather complex nuclear dynamics along the degenerate deformation mode, v 4 ′ t 2 , have been thoroughly investigated by Time-Dependent Density Functional Theory (TD-DFT) method. The relevant Jahn–Teller distortion operative within the lowest-lying electronic excited-state is shown here for the first time in order to yield a weak absorption feature at 6.156 eV. Further calculations on the potential energy curves for the singlet excited-states along the C–Cl stretching coordinate show the relevance of efficient C–Cl bond excision. [ABSTRACT FROM AUTHOR]

Singlet fission (SF) is a photophysical process where one singlet exciton splits into two triplet excitons. To construct design guidelines for engineering directional triplet exciton migration, we investigated the SF dynamics in symmetric linear heterotrimer systems consisting of different unsubstituted or 6,13-disubstituted pentacene derivatives denoted as X/Y (X, Y: terminal and center monomer species). Time-dependent density functional theory (TDDFT) calculations clarified that the induction effects of the substituents, represented as Hammett's para-substitution coefficients σ p , correlated with both the excitation energies of S1 and T1 states, in addition to the energies of the highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO). Electronic coupling calculations and quantum dynamics simulations revealed that the selectivity of spatially separated TT states for heterotrimers increased over 70%, superior to that in the homotrimer: an optimal region of the difference in σ p between the substituents of X and Y for the increase in SF rate was found. The origin of the rise in SF rate is explained by considering the quantum interference effect: reduction in structural symmetry opens new interaction paths, allowing the S1-TT mixing, which contributes to accelerating the hetero-fission between the terminal and center molecules. [ABSTRACT FROM AUTHOR]

Organic molecular fluorophores have been extensively utilized for biological imaging in the visible and the first near-infrared windows. However, their applications in the second near-infrared (NIR-II) window remain constrained, primarily due to the insufficient fluorescence brightness. Herein, we employ a theoretical protocol combining the thermal vibration correlation function with the time-dependent density functional theory method to investigate the mechanism of the planar-twisted strategy for developing fluorophores with balanced NIR-II emission and fluorescence brightness. Based on a planar donor–acceptor–donor molecular skeleton, various ortho-positioned alkyl side chains with steric hindrances are tactfully incorporated into the backbone to construct a series of twisted fluorophores. Photophysical characterizations of the studied fluorophores demonstrate that the emission spectra located in the NIR-II region exhibited a hypsochromic shift with the structural distortion. Notably, conformational twisting significantly accelerated the radiative decay rate while simultaneously suppressing the nonradiative decay rate, resulting in an improved fluorescence quantum efficiency (FQE). This enhancement can be mainly attributed to both the enlarged adiabatic excitation energy and reduced nonadiabatic electronic coupling between the first excited state and the ground state. Compared with the planar fluorophore, the twisted structures possessed a more than fivefold increase in FQE. In particular, the optimal twisted fluorophore BBTD-4 demonstrated a desirable fluorescence brightness (16.59 M−1 cm−1) on the premise of typical NIR-II emission (980 nm), making it a promising candidate for NIR-II fluorescence imaging in biomedical applications. The findings in this study elucidate the available experimental observations on the analogues, highlighting a feasible approach to modulating the photophysical performances of NIR-II chromophores for developing more highly efficient fluorophores toward optical imaging applications. [ABSTRACT FROM AUTHOR]

Continuing the investigation started for dopamine (DA) and dopamine-o-quinone (DoQ) (see, the light absorption and charge transfer properties of the dopamine zwitterion (called dopamine-semiquinone or DsQ) adsorbed on the graphene nanoparticle surface is investigated using the ground state and linear-response time-dependent density functional theories, considering the ωB97X-D3BJ/def2-TZVPP level of theory. In terms of the strength of molecular adsorption on the surface, the DsQ form has 50% higher binding energy than that found in our previous work for the DA or DoQ cases (−20.24 kcal/mol vs. −30.41 kcal/mol). The results obtained for electronically excited states and UV-Vis absorption spectra show that the photochemical behavior of DsQ is more similar to DA than that observed for DoQ. Of the three systems analyzed, the DsQ-based complex shows the most active charge transfer (CT) phenomenon, both in terms of the number of CT-like states and the amount of charge transferred. Of the first thirty electronically excited states computed for the DsQ case, eleven are purely of the CT type, and nine are mixed CT and localized (or Frenkel) excitations. By varying the adsorption distance between the molecule and the surface vertically, the amount of charge transfer obtained for DA decreases significantly as the distance increases: for DoQ it remains stable, for DsQ there are states for which little change is observed, and for others, there is a significant change. Furthermore, the mechanistic compilation of the electron orbital diagrams of the individual components cannot describe in detail the nature of the excitations inside the complex. [ABSTRACT FROM AUTHOR]

A tetraphenylethylene (TPE) derivative, TPEPhDAT, modified by diaminotriazine (DAT), was prepared by successive Suzuki–Miyaura coupling and ring-closing reactions. This compound exhibits aggregation-induced emission enhancement (AIEE) properties in the DMSO/MeOH system, with a fluorescence emission intensity in the aggregated state that is 5-fold higher than that of its counterpart in a dilute solution. Moreover, the DAT structure of the molecule is a good acceptor of protons; thus, the TPEPhDAT molecule exhibits acid-responsive fluorescence. TPEPhDAT was protonated by trifluoroacetic acid (TFA), leading to fluorescence quenching, which was reversibly restored by treatment with ammonia (on–off switch). Time-dependent density functional theory (TDDFT) computational studies have shown that protonation enhances the electron-withdrawing capacity of the triazine nucleus and reduces the bandgap. The protonated TPEPhDAT conformation became more distorted, and the fluorescence lifetime was attenuated, which may have produced a twisted intramolecular charge transfer (TICT) effect, leading to fluorescence redshift and quenching. MeOH can easily remove the protonated TPEPhDAT, and this acid-induced discoloration and erasable property can be applied in anti-counterfeiting. [ABSTRACT FROM AUTHOR]

A new coordination polymer {[Cd(C12H13O5)2(4,4′-bpy)(H2O)2]}n (Cd-Tmca-bpy) was constructed with trans-2,3,4-Trimethoxycinnamic acid (HTmca) and 4,4′-Bipyridine (4,4′-bpy) ligands. This complex was structurally characterized on the basis of elemental analysis, infrared (IR) spectroscopy, powder X-ray diffraction and thermogravimetric analyses. X-ray crystallography revealed that the complex was monoclinic, space group C2/c. The Cd(II) ion in the complex was six coordinated, adopting an octahedron geometry. The neighboring Cd(II) ions linked linear ligand 4,4′-bpy molecules to form an infinite 1D chain. The 1D chain was further interlinked by O–H···O and C–H···O hydrogen bonds, resulting in a 3-D supramolecular framework. Meanwhile, the photoluminescence spectrum of the Cd(II) complex at room temperature exhibited an emission maximum at 475 nm. Using the time-dependent density functional theory (TD-DFT) method, the electronic absorption spectra of the Cd(II) complex was predicted. A good agreement was achieved between the predicted spectra and the experimental data. Bioactivity studies showed that the complex exhibited significant inhibition halos against Pseudomonas aeruginosa (P. aeruginosa) and Staphylococcus aureus (S. aureus). [ABSTRACT FROM AUTHOR]

Photoresponsive drug delivery stands as a pivotal frontier in smart drug administration, leveraging the non-invasive, stable, and finely tunable nature of light-triggered methodologies. The generative pre-trained transformer (GPT) has been employed to generate molecular structures. In our study, we harnessed GPT-2 on the QM7b dataset to refine a UV-GPT model with adapters, enabling the generation of molecules responsive to UV light excitation. Utilizing the Coulomb matrix as a molecular descriptor, we predicted the excitation wavelengths of these molecules. Furthermore, we validated the excited state properties through quantum chemical simulations. Based on the results of these calculations, we summarized some tips for chemical structures and integrated them into the alignment of large-scale language models within the reinforcement learning from human feedback (RLHF) framework. The synergy of these findings underscores the successful application of GPT technology in this critical domain. [ABSTRACT FROM AUTHOR]

Weak doping can broaden, shift, and quench plasmon peaks in nanoparticles, but the mechanistic intricacies of the diverse responses to doping remain unclear. In this study, we used the time-dependent density functional theory (TD-DFT) to compute the excitation properties of transition-metal Pd- or Pt-doped gold and silver atomic arrays and investigate the evolution characteristics and response mechanisms of their plasmon peaks. The results demonstrated that the Pd or Pt doping of the off-centered 10 × 2 atomic arrays broadened or shifted the plasmon peaks to varying degrees. In particular, for Pd-doped 10 × 2 Au atomic arrays, the broadened plasmon peak significantly blueshifted, whereas a slight red shift was observed for Pt-doped arrays. For the 10 × 2 Ag atomic arrays, Pd doping caused almost no shift in the plasmon peak, whereas Pt doping caused a substantial red shift in the broadened plasmon peak. The analysis revealed that the diversity in these doping responses was related to the energy positions of the d electrons in the gold and silver atomic clusters and the positions of the doping atomic orbitals in the energy bands. The introduction of doping atoms altered the symmetry and gap size of the occupied and unoccupied orbitals, so multiple modes of single-particle transitions were involved in the excitation. An electron transfer analysis indicated a close correlation between excitation energy and the electron transfer of doping atoms. Finally, the differences in the symmetrically centered 11 × 2 doped atomic array were discussed using electron transfer analysis to validate the reliability of this analytical method. These findings elucidate the microscopic mechanisms of the evolution of plasmon peaks in doped atomic clusters and provide new insights into the rational control and application of plasmons in low-dimensional nanostructures. [ABSTRACT FROM AUTHOR]

A chemical and biological exploration of the European polypore Dentipellis fragilis afforded two previously undescribed natural products (1 and 2), together with three known derivatives (3–5). Chemical structures of the isolated compounds were confirmed through 1D/2D NMR spectroscopic analyses, mass spectrometry, and by comparison with the reported literature. The relative and absolute configurations of 1 were determined according to the ROESY spectrum and time-dependent density functional theory electronic circular dichroism (TDDFT-ECD), respectively. Furthermore, the absolute configuration of dentipellinol (3) was revisited and revealed to be of (R) configuration. All the isolated compounds were assessed for their cytotoxic and antimicrobial activities, with some being revealed to have weak to moderate antimicrobial activity, particularly against Gram-positive bacteria. [ABSTRACT FROM AUTHOR]

In this paper, the current status of time-dependent density functional theory (TDDFT)-based calculations for ion–atom collision problems is reviewed. Most if not all reported calculations rely on the semiclassical approximation of heavy particle collision physics and the time-dependent Kohn–Sham (TDKS) scheme for computing the electronic density of the system. According to the foundational Runge–Gross theorem, all information available about the electronic many-body system is encoded in the density; however, in practice it is often not known how to extract it without resorting to modelling and approximations. This is in addition to a necessarily approximate implementation of the TDKS scheme due to the lack of precise knowledge about the potential that drives the equations. Notwithstanding these limitations, an impressive body of work has been accumulated over the past few decades. A sample of the results obtained for various collision systems is discussed here, in addition to the formal underpinnings and theoretical and practical challenges of the application of TDDFT to atomic collision problems, which are expounded in mostly nontechnical terms. Open problems and potential future directions are outlined as well. [ABSTRACT FROM AUTHOR]

Advances in electronics and medical diagnostics have made organic dyes extremely popular as key functional materials. From a practical viewpoint, it is necessary to assess the spectroscopic and physicochemical properties of newly designed dyes. In this context, the condensation of 1,3-dimethylbarbituric acid with electron-rich alkylaminobenzaldehyde derivatives has been described, resulting in a series of merocyanine-type dyes. These dyes exhibit intense blue-light absorption but weak fluorescence. An electron-donating alkylamino group at position C4 is responsible for the solvatochromic behavior of the dyes since the lone electron pair of the nitrogen atom is variably delocalized toward the barbituric ring, which exhibits electron-withdrawing properties. This was elucidated, taking into account the different geometry of the amino group. The intramolecular charge transfer in the molecules is responsible for the relatively high redshift in absorption and fluorescence spectra. Additionally, an increase in solvent polarity moves the absorption and fluorescence to lower energy regions. The observed solvatochromism is discussed in terms of the four-parameter Catalán solvent polarity scale. The differences in the behavior of the dyes were quantified with the aid of time-dependent density functional theory calculations. The obtained results made it possible to find regularities linking the basic spectroscopic properties of the compounds with their chemical structure. This is important in the targeted search for new, practically important dyes. [ABSTRACT FROM AUTHOR]

Anthocyanins are colored water-soluble plant pigments. Upon consumption, anthocyanins are quickly absorbed and can penetrate the blood–brain barrier (BBB). Research based on population studies suggests that including anthocyanin-rich sources in the diet lowers the risk of neurodegenerative diseases. The copigmentation caused by copigments is considered an effective way to stabilize anthocyanins against adverse environmental conditions. This is attributed to the covalent and noncovalent interactions between colored forms of anthocyanins (flavylium ions and quinoidal bases) and colorless or pale-yellow organic molecules (copigments). The present work carried out a theoretical study of the copigmentation process between cyanidin and resveratrol (CINRES). We used three levels of density functional theory: M06-2x/6-31g+(d,p) (d3bj); ωB97X-D/6-31+(d,p); APFD/6-31+(d,p), implemented in the Gaussian16W package. In a vacuum, the CINRES was found at a copigmentation distance of 3.54 Å between cyanidin and resveratrol. In water, a binding free energy ∆G was calculated, rendering −3.31, −1.68, and −6.91 kcal/mol, at M06-2x/6-31g+(d,p) (d3bj), ωB97X-D/6-31+(d,p), and APFD/6-31+(d,p) levels of theory, respectively. A time-dependent density functional theory (TD-DFT) was used to calculate the UV spectra of the complexes and then compared to its parent molecules, resulting in a lower energy gap at forming complexes. Excited states' properties were analyzed with the ωB97X-D functional. Finally, Shannon aromaticity indices were calculated and isosurfaces of non-covalent interactions were evaluated. [ABSTRACT FROM AUTHOR]

The level of fluoride ions (F−) in the human body is closely related to various pathological and physiological states, and the rapid detection of F− is important for studying physiological processes and the early diagnosis of diseases. In this study, the detailed sensing mechanism of a novel high-efficiency probe (PBT) based on 2-(2′-hydroxyphenyl)-benzothiazole derivatives towards F− has been fully investigated based on density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods. F− attacks the O-P bond of PBT to cleavage the dimethylphosphinothionyl group, and the potential products were evaluated by Gibbs free energy and spectroscopic analyses, which ultimately identified the product as HBT-Enol1 with an intramolecular hydrogen bond. Bond parameters, infrared vibrational spectroscopy and charge analysis indicate that the hydrogen bond is enhanced at the excited state (S1), favoring excited state intramolecular proton transfer (ESIPT). The mild energy barrier further evidences the occurrence of ESIPT. Combined with frontier molecular orbital (FMO) analysis, the fluorescence quenching of PBT was attributed to the photoinduced electron transfer (PET) mechanism and the fluorescence turn-on mechanism of the product was attributed to the ESIPT process of HBT-Enol1. [ABSTRACT FROM AUTHOR]

Excited state calculations are performed to predict the electronic structure and optical absorption characteristics of Cu-doped anatase Ti O 2  nanofilms, focusing on their (101) and (001) surface terminations. Using model structures that successfully represent the equilibrium positions of deposited Cu atoms on the Ti O 2  surface, a comprehensive analysis of the absorption spectra for each considered model is made. The proposed modeling reveals phenomena when photogenerated electrons from Ti O 2  tend to accumulate in the vicinity of the deposited Cu atoms exposed to photon energies surpassing the band gap of Ti O 2  (approximately 3.2 eV). The crucial transition states that are essential for the creation of potential photocatalytic materials are identified through detailed calculations of the excited states. These insights hold substantial promise for the strategic design of advanced photocatalytic materials. The obtained results provide a base for subsequent analyses, facilitating the determination of heightened surface reactivity, photostimulated water splitting, and antibacterial properties. [ABSTRACT FROM AUTHOR]

We report on DFT-TDDFT studies of the structural, electronic and vibrational properties of B 24 N 24 nanocapsules and the effect of encapsulation of homonuclear diatomic halogens ( C l 2 , B r 2 and I 2 ) and chalcogens ( S 2 and S e 2 ) on the interaction of the B 24 N 24 nanocapsules with the divalent magnesium cation. In particular, to foretell whether these BN nanostructures could be proper negative electrodes for magnesium-ion batteries, the structural, vibrational and electronic properties, as well as the interaction energy and the cell voltage, which is important for applications, have been computed for each system, highlighting their differences and similarities. The encapsulation of halogen and chalcogen diatomic molecules increases the cell voltage, with an effect enhanced down groups 16 and 17 of the periodic table, leading to better performing anodes and fulfilling a remarkable cell voltage of 3.61 V for the iodine-encapsulated system. [ABSTRACT FROM AUTHOR]

Florfenicol (FLO) is a widely used antibacterial drug, which is often detected in the environment. In this paper, the photolysis mechanism of FLO in water was investigated using density functional theory (DFT) and time-dependent density functional theory (TDDFT). The focus of the study is to elucidate the direct photolysis mechanism of FLO in the water environment and the indirect photolysis of free radicals (·OH, ·NO3, and ·SO4−) as active species. The effect of metal ions Ca2+/Mg2+/Zn2+ on the indirect photolysis was also investigated. The results show that the direct photolysis of FLO involves C–C/C–N/C–S bond cleavage, the C5–S7 bond cleavage is most likely to occur, and the C17–C18 cleavage reaction is not easy to occur during the direct photodegradation of FLO. The indirect photolysis of FLO is more likely to occur in the environment than direct photolysis. The main indirect photolysis involves OH-addition, NO3-addition, and SO4-addition on benzene ring. The order of difficulty in the indirect photolysis with ·OH is C2 > C3 > C4 > C5 > C6 > C1, Ca2+ can promote the indirect photolysis with ·OH, and Mg2+/Zn2+ has a dual effect on the indirect photolysis with ·OH. In other words, Mg2+ and Zn2+ can inhibit or promote the indirect photolysis with ·OH. These studies provide important information for theoretical research on the environmental behavior and degradation mechanism of drug molecules. [ABSTRACT FROM AUTHOR]

Due to their unique photophysical and electronic properties, pyrene and its analogues have been the subject of extensive research in recent decades. The propensity of pyrene and its derivatives to form excimers has found wide application in various fields. Nitrogen-substituted pyrene derivatives display similar photophysical properties, but for them, excimer emission has not been reported to date. Here, we use time-dependent density functional theory (TD-DFT) calculations to investigate the low-lying exciton states of dimers of pyrene and 2-azapyrene. The excimer equilibrium structures are determined and the contribution of charge transfer (CT) excitations and intermolecular interactions to the exciton states is disclosed using a diabatization procedure. The study reveals that the dimers formed by the two molecules have quite similar exciton-state patterns, in which the relevant CT contributions govern the formation of excimer states, along with the La/Lb state inversion. In contrast with pyrene, the dipole–dipole interactions in 2-azapyrene stabilize the dark eclipsed excimer structure and increase the barrier for conversion into a bright twisted excimer. It is suggested that these differences in the nitrogen-substituted derivative might influence the excimer emission properties. [ABSTRACT FROM AUTHOR]

The formation of a peptide fragment ion [c + 2H]+ was examined using ultraviolet matrix-assisted laser desorption/ionization in-source decay mass spectrometry (UV/MALDI-ISD MS). Unusually, an ISD experiment with a hydrogen-abstracting oxidative matrix 4-nitro-1-naphthol (4,1-NNL) resulted in a [c + 2H]+ ion when the analyte peptides contained serine (Ser), threonine (Thr), and/or cysteine (Cys) residues, although the ISD with 4,1-NNL merely resulted in [a]+ and [d]+ ions. The [c + 2H]+ ion observed could be rationalized through intramolecular hydrogen atom transfer (HAT), like a Type-II reaction via a seven-membered conformation involving intramolecular hydrogen bonding (HB) between the active hydrogens (–OH and –SH) of the Ser/Thr/Cys residues and the backbone carbonyl oxygen at the adjacent amino (N)-terminal side residue. The ISD of the Cys-containing peptide resulted in the [c + 2H]+ ions, which originated from cleavage at the backbone N-Cα bonds far from the Cys residue, suggesting that the peptide molecule formed 16- and 22-membered transient conformations in the gas phase. The time-dependent density functional theory (TDDFT) calculations of the model structures of the Ser and Cys residues indicated that the Cys residue did not show a constructive bond interaction between the donor thiol (-SH) and carbonyl oxygen (=CO), while the Ser residue formed a distinct intramolecular HB. [ABSTRACT FROM AUTHOR]

The marine-derived fungal strains KMM 4718 and KMM 4747 isolated from sea urchin Scaphechinus mirabilis as a natural fungal complex were identified as Penicillium sajarovii and Aspergillus protuberus based on Internal Transcribed Spacer (ITS), partial β-tubulin (BenA), and calmodulin (CaM) molecular markers as well as an ribosomal polymerase two, subunit two (RPB2) region for KMM 4747. From the ethyl acetate extract of the co-culture, two new polyketides, sajaroketides A (1) and B (2), together with (2′S)-7-hydroxy-2-(2′-hydroxypropyl)-5-methylchromone (3), altechromone A (4), norlichexanthone (5), griseoxanthone C (6), 1,3,5,6-tetrahydroxy-8-methylxanthone (7), griseofulvin (8), 6-O-desmethylgriseofulvin (9), dechlorogriseofulvin (10), and 5,6-dihydro-4-methyl-2H-pyran-2-one (11) were identified. The structures of the compounds were elucidated using spectroscopic analyses. The absolute configurations of the chiral centers of sajaroketides A and B were determined using time-dependent density functional theory (TDDFT)-based calculations of the Electronic Circular Dichroism (ECD) spectra. The inhibitory effects of these compounds on urease activity and the growth of Staphylococcus aureus, Escherichia coli, and Candida albicans were observed. Sajaroketide A, altechromone A, and griseofulvin showed significant cardioprotective effects in an in vitro model of S. aureus-induced infectious myocarditis. [ABSTRACT FROM AUTHOR]

Luminescent diimine-Pt(IV) complexes [Pt(N^N)(Me)2(PhSe)2], (N^N = 2,2′-bipyridine (bpy, 1b), 1,10-phenanthroline (phen, 2b), and 4,4′-dimethyl-2,2′-bipyridine (Me2bpy, 3b), PhSe− = phenyl selenide were prepared and identified using multinuclear (1H, 13C{1H} and 77Se{1H}) NMR spectroscopy. The PhSe− ligands were introduced through oxidative addition of diphenyl diselenide to the non-luminescent Pt(II) precursors [Pt(N^N)(Me)2], N^N = (bpy, 1a), (phen, 2a), (Me2bpy, 3a), to give the luminescent Pt(IV) complexes 1b–3b. The UV-vis absorption spectra of 1b–3b are characterised by intense bands in the range 240–330 nm. We assigned them to transitions of essentially π−π* character with small metal and PhSe− ligand contributions with the help of TD-DFT (time-dependent density functional theory) calculations. The weak long-wavelength bands in the range 350–475 nm are of mixed ligand-to-metal charge transfer (L'MCT) (n(Se)→d(Pt)/intra-ligand charge transfer (IL'CT) (n(Se)→π*(Ph) or π(Ph)→π*(Ph))/ligand-to-ligand' charge transfer (LL'CT) (L = N^N, L' = PhSe−, M = Pt and n = lone pair) character. The Pt(IV) complexes showed broad emission bands in the solid state at 298 and 77 K, peaking at 560–595 nm with a blue shift upon cooling. Structured emission bands were obtained in the range 450–600 nm, with the maxima depending on the N^N ligands and the solvent polarity (CH2Cl2 vs. dimethyl sulfoxide (DMSO) and aqueous tris(hydroxymethyl)aminomethane hydrochloride (tris-HCl) buffer). The emissions originate from essentially ligand-centred triplet states (3LC) with mixed IL'CT/L'MCT contributions as concluded from the DFT calculation. Such dominating PhSe contributions to the emissive states are unprecedented in the world of luminescent diimine-Pt(IV) complexes. [ABSTRACT FROM AUTHOR]

A new copper(I) complex, [Cu2(L)2dppm](PF6)2 (1) [L = 3-(2-Pyridyl)-5,6-diphenyl-1,2,4-triazine and dppm: Bis(diphenylphosphino)methane], was prepared and characterized by IR, 1H-NMR, 31P-NMR spectroscopy, elemental and thermogravimetric analysis, and a single-crystal X-ray diffraction technique. Complex 1 is a dinuclear compound, showing that L and dppm act as tridentate and bidentate chelating ligands, respectively. The two Cu(I) atoms exhibit a distorted tetrahedral coordination sphere embedded in N3P environments. The supramolecular interactions in the solid-state structure are characterized by C−H···N, C−H···F, C-H···π and π···π intermolecular interactions, which we studied using Hirshfeld surface and fingerprint tools. Additionally, the complex was studied experimentally using UV–Vis spectroscopy and cyclic voltammetry, and theoretical studies with time-dependent density functional theory (TD-DFT) were performed. Moreover, the optical and electrochemical properties were studied, focusing on the band gap. Compound 1 was used as a co-sensitizer in a dye-sensitized solar cell, showing a good photovoltaic performance of 2.03% (Jsc = 5.095 mAcm−2, Voc = 757 mV, and FF = 52.7%) under 100 mW cm−2 (AM 1.5G) solar irradiation, which is similar to that of DSSC, which was only sensitized by N719 (2.2%) under the same condition. [ABSTRACT FROM AUTHOR]

Three new cembranoids (1–3) and a new casbanoid (4), along with three known analogues (5–7), have been isolated from the soft coral Sinularia nanolobata collected off Ximao Island. The structures, including the absolute configurations of new compounds, were established using extensive spectroscopic data analysis, time-dependent density functional theory/electronic circular dichroism (TDDFT-ECD) calculations, and the comparison with spectroscopic data of known compounds. In the in vitro bioassay, compounds 1 and 5 exhibited moderate cytotoxic activities against human erythroleukemia (HEL) cell lines, with IC50 values of 37.1 and 42.4 μM, respectively. [ABSTRACT FROM AUTHOR]

Fluorescent labels are key tools in a wide range of modern scientific applications, such as fluorescence microscopy, flow cytometry, histochemistry, direct and indirect immunochemistry, and fluorescence in situ hybridization (FISH). Small fluorescent labels have important practical advantages as they allow maximizing the fluorescence signal by binding multiple fluorophores to a single biomolecule. At present, the most widely used fluorescent labels available present small Stokes shifts and are too costly to be used in routine applications. In this work we present four new coumarin derivatives, as promising and inexpensive fluorescent labels for biomolecules, obtained through a cost-effective, efficient, and straightforward synthetic strategy. Density functional theory and time-dependent density functional theory calculations of the electronic ground and lowest-lying singlet excited states were carried out in order to gain insights into the observed photophysical properties. [ABSTRACT FROM AUTHOR]

Developing efficient and sensitive MOF-based luminescence sensors for bioactive molecule detection is of great significance and remains a challenge. Benefiting from favorable chemical and thermal stability, as well as excellent luminescence performance, a porous Zn(II)Ho(III) heterometallic–organic framework (ZnHoMOF) was selected here as a bifunctional luminescence sensor for the early diagnosis of a toluene exposure biomarker of hippuric acid (HA) through "turn-on" luminescence enhancing response and the daily monitoring of NFT/NFZ antibiotics through "turn-off" quenching effects in aqueous media with high sensitivity, acceptable selectivity, good anti-interference, exceptional recyclability performance, and low detection limits (LODs) of 0.7 ppm for HA, 0.04 ppm for NFT, and 0.05 ppm for NFZ. Moreover, the developed sensor was employed to quantify HA in diluted urine samples and NFT/NFZ in natural river water with satisfactory results. In addition, the sensing mechanisms of ZnHoMOF as a dual-response chemosensor in efficient detection of HA and NFT/NFZ antibiotics were conducted from the view of photo-induced electron transfer (PET), as well as inner filter effects (IFEs), with the help of time-dependent density functional theory (TD-DFT) and spectral overlap experiments. [ABSTRACT FROM AUTHOR]

The modulation of molecular characteristics in metal-free organic dyes holds significant importance in dye-sensitized solar cells (DSSCs). The D-π-A molecular design, based on the furan moiety (π) in the conjugated spacer between the arylamine (D) and the 2-cyanoacrylic acid (A), was developed and theoretically evaluated for its potential application in DSSCs. Utilizing linear response time-dependent density functional theory (TDDFT) with the CAM-B3LYP functional, different donor and acceptor groups were characterized in terms of the electronic absorption properties of these dyes. All the studied dye sensitizers demonstrate the ability to inject electrons into the semiconductor's conduction band (TiO2) and undergo regeneration through the redox potential triiodide/iodide (I3−/I−) electrode. TDDFT results indicate that the dyes with CSSH anchoring groups exhibit improved optoelectronic properties compared to other dyes. Further, the photophysical properties of all dyes absorbed on a Ti(OH)4 model were explored and reported. The observed results indicate that bidentate chemisorption occurs between dyes and TiO4H5. Furthermore, the HOMO–LUMO energy gaps for almost all dye complexes are significantly smaller than those of the free dyes. This decrease of the HOMO–LUMO energy gaps in the dye complexes facilitates electron excitation, and thus more photons can be adsorbed, guaranteeing larger values of efficiency and short-circuit current density. [ABSTRACT FROM AUTHOR]

In the present work, we apply recently developed real-time descriptors to study the time evolution of plasmonic features of pentagonal Ag clusters. The method is based on the propagation of the time-dependent Schrödinger equation within a singly excited TDDFT ansatz. We use transition contribution maps (TCMs) and induced density to characterize the optical longitudinal and transverse response of such clusters, when interacting with pulses resonant with the low-energy (around 2–3 eV, A 1 ) size-dependent or the high-energy (around 4 eV, E 1 ) size-independent peak. TCMs plots on the analyzed clusters, Ag 25 + and Ag 43 + show off-diagonal peaks consistent with a plasmonic response when a longitudinal pulse resonant at A 1 frequency is applied, and dominant diagonal spots, typical of a molecular transition, when a transverse E 1 pulse is employed. Induced densities confirm this behavior, with a dipole-like charge distribution in the first case. The optical features show a time delay with respect to the evolution of the external pulse, consistent with those found in the literature for real-time TDDFT calculations on metal clusters. [ABSTRACT FROM AUTHOR]

The potential involvement of polysulfide radical anions Sn•− is a recurring theme in discussions of the basic and applied chemistry of elemental sulfur. However, while the spectroscopic features for n = 2 and 3 are well-established, information on the structures and optical characteristics of the larger congeners (n = 4–8) is sparse. To aid identification of these ephemeral species we have performed PCM-corrected DFT calculations to establish the preferred geometries for Sn•− (n = 4–8) in the polar media in which they are typically generated. TD-DFT calculations were then used to determine the number, nature and energies of the electronic excitations possible for these species. Numerical reliability of the approach was tested by comparison of the predicted and experimental excitation energies found for S2•− and S3•−. The low-energy (near-IR) transitions found for the two acyclic isomers of S4•− (C2h and C2v symmetry) and for S5•− (Cs symmetry) can be understood by extension of the simple HMO π-only chain model that serves for S2•− and S3•−. By contrast, the excitations predicted for the quasi-cyclic structures Sn•− (n = 6–8) are better described in terms of σ → σ* processes within a localized 2c-3e manifold. [ABSTRACT FROM AUTHOR]

Two novel ionic red/near-infrared Ir(III) complexes (Ir1 and Ir2) were reasonably designed and prepared using 2-(1-isoquinolinyl)-9,10-anthraquinone as the main ligand and 4,4′-dimethyl-2,2′-bipyridyl and 4,4′-dimethoxy-2,2′-bipyridyl as the auxiliary ligands, respectively. Both complexes showed bright phosphorescence in solution (peak at 618 nm with a shoulder at 670 nm). Interestingly, the phosphorescence peak of two Ir(III) complexes showed a blue-shift of about 36 nm after being ground. Simultaneously, both complexes exhibited mechanical force-induced enhanced emission, and the intensity of the luminescence for Ir1 and Ir2 increased by around two times compared to the one before being ground, respectively. Powder X-ray diffraction (PXRD) and time-dependent density functional theory (TD-DFT) calculation were utilized to understand well the mechanism of this phenomenon and suggested that the destruction of the well-ordered crystalline nature and the decline in triplet-triplet annihilation maybe responsible for the pressure-induced blue-shift and the enhancement of the phosphorescence. [ABSTRACT FROM AUTHOR]

Citalopram (CIT) is a commonly prescribed medication for depression. However, the photodegradation mechanism of CIT has not yet been fully analyzed. Therefore, the photodegradation process of CIT in water is studied by density functional theory and time-dependent density functional theory. The calculated results show that during the indirect photodegradation process, the indirect photodegradation of CIT with ·OH occurs via OH-addition and F-substitution. The minimum activation energy of C10 site was 0.4 kcal/mol. All OH-addition and F-substitution reactions are exothermic. The reaction of 1O2 with CIT includes the substitution of 1O2 for F and an addition reaction at the C14 site. The Ea value of this process is 1.7 kcal/mol, which is the lowest activation energy required for the reaction of 1O2 with CIT. C–C/C–N/C–F cleavage is involved in the direct photodegradation process. In the direct photodegradation of CIT, the activation energy of the C7-C16 cleavage reaction was the lowest, which was 12.5 kcal/mol. Analysis of the Ea values found that OH-addition and F-substitution, the substitution of 1O2 for F and addition at the C14 site, as well as the cleavage reactions of C6–F/C7–C16/C17–C18/C18–N/C19–N/C20–N are the main pathways of photodegradation of CIT. [ABSTRACT FROM AUTHOR]

The optical properties of graphene nanodots (GND) and their interaction with phosphate ions have been investigated to explore their potential for optical sensing applications. The absorption spectra of pristine GND and modified GND systems were analyzed using time-dependent density functional theory (TD-DFT) calculation investigations. The results revealed that the size of adsorbed phosphate ions on GND surfaces correlated with the energy gap of the GND systems, leading to significant modifications in their absorption spectra. The introduction of vacancies and metal dopants in GND systems resulted in variations in the absorption bands and shifts in their wavelengths. Moreover, the absorption spectra of GND systems were further altered upon the adsorption of phosphate ions. These findings provide valuable insights into the optical behavior of GND and highlight their potential for the development of sensitive and selective optical sensors for phosphate detection. [ABSTRACT FROM AUTHOR]

Organic light-emitting diodes (OLEDs) are energy-efficient; however, the coordinating ligand can affect their stability. Sky-blue phosphorescent Pt(II) compounds with a C^N chelate, fluorinated-dbi (dbi = [1-(2,4-diisopropyldibenzo [b,d]furan-3-yl)-2-phenyl-1H-imidazole]), and acetylactonate (acac) (1)/picolinate (pic) (2) ancillary ligands were synthesized. The molecular structures were characterized using various spectroscopic methods. The Pt(II) Compound Two exhibited a distorted square planar geometry, with several intra- and inter-molecular interactions involving Cπ⋯H/Cπ⋯Cπ stacking. Complex One emitted bright sky-blue light (λmax = 485 nm) with a moderate photoluminescent quantum efficiency (PLQY) of 0.37 and short decay time (6.1 µs) compared to those of 2. Theoretical calculations suggested that the electronic transition of 1 arose from ligand(C^N)-centered π–π* transitions combined with metal-to-ligand charge-transfer (MLCT), whereas that of 2 arose from MLCT and ligand(C^N)-to-ligand(pic) charge-transfer (LLCT), with minimal contribution from C^N chelate to the lowest unoccupied molecular orbital (LUMO). Multi-layered phosphorescent OLEDs using One as a dopant and a mixed host, mCBP/CNmCBPCN, were successfully fabricated. At a 10% doping concentration of 1, a current efficiency of 13.6 cdA−1 and external quantum efficiency of 8.4% at 100 cdm−2 were achieved. These results show that the ancillary ligand in phosphorescent Pt(II) complexes must be considered. [ABSTRACT FROM AUTHOR]

The exponentially growing energy requirements and, in turn, extensive depletion of non-restorable sources of energy are a major cause of concern. Restorable energy sources such as solar cells can be used as an alternative. However, their low efficiency is a barrier to their practical use. This provokes the research community to design efficient solar cells. Based on the study of efficacy, design feasibility, and cost of fabrication, DSSC shows supremacy over other photovoltaic solar cells. However, fabricating DSSC in a laboratory and then assessing their characteristics is a costly affair. The researchers applied techniques of computational chemistry such as Time-Dependent Density Functional Theory, and an ab initio method for defining the structure and electronic properties of dyes without synthesizing them. However, the inability of descriptors to provide an intuitive physical depiction of the effect of all parameters is a limitation of the proposed approaches. The proven potential of neural network models in data analysis, pattern recognition, and object detection motivated researchers to extend their applicability for predicting the absorption maxima (λmax) of dye. The objective of this research is to develop an ANN-based QSPR model for correctly predicting the value of λmax for inorganic ruthenium complex dyes used in DSSC. Furthermore, it demonstrates the impact of different activation functions, optimizers, and loss functions on the prediction accuracy of λmax. Moreover, this research showcases the impact of atomic weight, types of bonds between constituents of the dye molecule, and the molecular weight of the dye molecule on the value of λmax. The experimental results proved that the value of λmax varies with changes in constituent atoms and types of bonds in a dye molecule. In addition, the model minimizes the difference in the experimental and calculated values of absorption maxima. The comparison with the existing models proved the dominance of the proposed model. [ABSTRACT FROM AUTHOR]

The peculiarities of the optical properties of 2-aryl-1,2,3-triazole acids and their sodium salts were investigated in different solvents (1,4-dioxane, dimethyl sulfoxide DMSO, methanol MeOH) and in mixtures with water. The results were discussed in terms of the molecular structure formed by inter- and intramolecular noncovalent interactions (NCIs) and their ability to ionize in anions. Theoretical calculations using the Time-Dependent Density Functional Theory (TDDFT) were carried out in different solvents to support the results. In polar and nonpolar solvents (DMSO, 1,4-dioxane), fluorescence was provided by strong neutral associates. Protic MeOH can weaken the acid molecules' association, forming other fluorescent species. The fluorescent species in water exhibited similar optical characteristics to those of triazole salts; therefore, their anionic character can be assumed. Experimental 1H and 13C-NMR spectra were compared to their corresponding calculated spectra using the Gauge-Independent Atomic Orbital (GIAO) method and several relationships were established. All these findings showed that the obtained photophysical properties of the 2-aryl-1,2,3-triazole acids noticeably depend on the environment and, therefore, are good candidates as sensors for the identification of analytes with labile protons. [ABSTRACT FROM AUTHOR]

We report a joint experimental and theoretical work on the steady-state spectroscopy and time-resolved emission of the coumarin C153 dye in methanol. The lowest energy excited state of this molecule is characterized by an intramolecular charge transfer thus leading to remarkable shifts of the time-resolved emission spectra, dictated by the methanol reorganization dynamics. We selected this system as a prototypical test case for the first application of a novel computational protocol aimed at the prediction of transient emission spectral shapes, including both vibronic and solvent effects, without applying any phenomenological broadening. It combines a recently developed quantum–classical approach, the adiabatic molecular dynamics generalized vertical Hessian method (Ad-MD | g VH), with nonequilibrium molecular dynamics simulations. For the steady-state spectra we show that the Ad-MD|gVH approach is able to reproduce quite accurately the spectral shapes and the Stokes shift, while a ∼0.15 eV error is found on the prediction of the solvent shift going from gas phase to methanol. The spectral shape of the time-resolved emission signals is, overall, well reproduced, although the simulated spectra are slightly too broad and asymmetric at low energies with respect to experiments. As far as the spectral shift is concerned, the calculated spectra from 4 ps to 100 ps are in excellent agreement with experiments, correctly predicting the end of the solvent reorganization after about 20 ps. On the other hand, before 4 ps solvent dynamics is predicted to be too fast in the simulations and, in the sub-ps timescale, the uncertainty due to the experimental time resolution (300 fs) makes the comparison less straightforward. Finally, analysis of the reorganization of the first solvation shell surrounding the excited solute, based on atomic radial distribution functions and orientational correlations, indicates a fast solvent response (≈100 fs) characterized by the strengthening of the carbonyl–methanol hydrogen bond interactions, followed by the solvent reorientation, occurring on the ps timescale, to maximize local dipolar interactions. [ABSTRACT FROM AUTHOR]

The systems of poloidal field coils in D-shaped Tokamaks such as ITER, EAST, JET, ASDEX Upgrade, TCV, GLOBUS-M2, DIII-D, SPARC, IGNITOR, JT-60SA, DEMO-9.1, DEMO-1.6, T-15MD, and TRT are analyzed for their efficiency in the application of plasma position, current, and shape control systems in these Tokamaks. The problem of magnetic plasma control in Tokamaks is presented. A methodology for designing hierarchical cascade systems of magnetic plasma control in D-shaped Tokamaks has been developed on the basis of generalizations of existing plasma magnetic control systems. The hierarchical levels are as follows: multivariable robust cascade control level, adaptation level, artificial intelligence level, and decision-making level. To implement these systems in the practice of physical experimentation, it is proposed to use digital twins, the basis of which is a real-time digital testbed created by Lomonosov Moscow State University and the Trapeznikov Institute of Control Sciences of the Russian Academy of Sciences. [ABSTRACT FROM AUTHOR]

The six stilbene-based dyes containing benzoxazole substituents to improve solubility of dyes as well as the efficiency of fluorescence at blue emission were synthesized. In this work, absorption and fluorescent properties of the synthesized dyes were investigated. For the derivatization of benzoxazolyl stilbene dye, -NO2 and -NH2 groups were introduced in sequence onto benzoxazolyl rings. The emission maxima of the six dyes prepared were observed in the range of 435 nm~471 nm. In addition, the solubility of the dyes in dichloromethane was examined for application to the nonpolar polymer films such as PE, PP, PVC and so on. N-alkyl groups were determined to have a greater solubility of alkylated stilbene-based dyes than analogue containing and unsubstituted group. Furthermore, investigation of the optical effects of tortional strain according to conformation of side group was also performed. For identifying these properties, the geometry, dihedral angle, and other parameters of synthesized dyes were calculated by the density functional theory and time-dependent function using a gaussian 09 program. [ABSTRACT FROM AUTHOR]

The geometry and electronic structures of iron(II) complexes with porphyrin (FeP) and tetrabenzoporphyrin (FeTBP) in ground and low-lying excited electronic states are determined by DFT (PBE0/def2-TZVP) calculations and the complete active space self-consistent field (CASSCF) method, followed by the multiconfigurational quasi-degenerate second-order perturbation theory (MCQDPT2) approach to determine the dynamic electron correlation. The minima on the potential energy surfaces (PESs) of the ground (3A2g) and low-lying, high-spin (5A1g) electronic states correspond to the planar structures of FeP and FeTBP with D4h symmetry. According to the results of the MCQDPT2 calculations, the wave functions of the 3A2g and 5A1g electronic states are single determinant. The electronic absorption (UV–Vis) spectra of FeP and FeTBP are simulated within the framework of the simplified time-dependent density functional theory (sTDDFT) approach with the use of the long-range corrected CAM-B3LYP function. The most intensive bands of the UV–Vis spectra of FeP and FeTBP occur in the Soret near-UV region of 370–390 nm. [ABSTRACT FROM AUTHOR]

Phosphorescent material is widely used in light-emitting devices and in the monitoring of cell phenomena. Anthraquinone compounds (AQs), as important phosphorescent materials, have potential applications as emitters for highly efficient organic light-emitting diodes (OLEDs). Therefore, the accurate calculation of the phosphorescence energy of anthraquinone compounds is particularly important. This study mainly analyzes the phosphorescence energy calculation method of anthraquinone compounds. The time-dependent density functional theory (TDDFT) and the unrestricted density functional theory (UDFT) with seven functionals are selected to calculate the phosphorescence of AQs, taking the high-precision coupled-cluster singles and doubles (CC2) method as a reference. The results showed that the mean unsigned error (MUE) of UDFT was 0.14 eV, which was much smaller than that of TDDFT at 0.29 eV. Therefore, UDFT was more suitable for calculating the phosphorescence energy of AQs. The results obtained by different functionals indicate that the minimum MUE obtained by M06-2X was 0.14 eV. More importantly, the diffuse function in the basis set played an important role in calculating the phosphorescence energy in the M06-HF functional. In the BDBT, FBDBT, and BrBDBT, when M06-HF selected the basis set containing a diffuse function, the differences with CC2 was 0.02 eV, which is much smaller than the one obtained without a diffuse function at 0.80 eV. These findings might be of great significance for the future study of the phosphorescence energy of organic molecules. [ABSTRACT FROM AUTHOR]

In this paper, both methods (DFT and HF) were used in a theoretical investigation of 3-bromo-2-Hydroxypyridine (3-Br-2HyP) molecules where the molecular structures of the title compound have been optimized. Molecular electrostatic potential (MEP) was computed using the B3LYP/6-311++G(d,p) level of theory. The time-dependent density functional theory (TD-DFT) approach was used to simulate the HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) on the one hand to achieve the frontier orbital gap and on the other hand to calculate the UV–visible spectrum of the compound in gas phase and for different solvents. In addition, electronic localization function and Fukui functions were carried out. Intermolecular interactions were discussed by the topological AIM (atoms in molecules) approach. The thermodynamic functions have been reported with the help of spectroscopic data using statistical methods revealing the correlations between these functions and temperature. To describe the non-covalent interactions, the reduced density gradient (RDG) analysis is performed. To study the biological activity of the compound of the molecule, molecular docking studies were executed on the active sites of BRD2 inhibitors and to explore the hydrogen bond interaction, minimum binding energies with targeted receptors such as PDB ID: 5IBN, 3U5K, 6CD5 were calculated. [ABSTRACT FROM AUTHOR]

In this contribution, we report a computational study of the vibrational Resonance Raman (vRR) spectra of cytosine in water, on the grounds of potential energy surfaces (PES) computed by time-dependent density functional theory (TD-DFT) and CAM-B3LYP and PBE0 functionals. Cytosine is interesting because it is characterized by several close-lying and coupled electronic states, challenging the approach commonly used to compute the vRR for systems where the excitation frequency is in quasi-resonance with a single state. We adopt two recently developed time-dependent approaches, based either on quantum dynamical numerical propagations of vibronic wavepackets on coupled PES or on analytical correlation functions for cases in which inter-state couplings were neglected. In this way, we compute the vRR spectra, considering the quasi-resonance with the eight lowest-energy excited states, disentangling the role of their inter-state couplings from the mere interference of their different contributions to the transition polarizability. We show that these effects are only moderate in the excitation energy range explored by experiments, where the spectral patterns can be rationalized from the simple analysis of displacements of the equilibrium positions along the different states. Conversely, at higher energies, interference and inter-state couplings play a major role, and the adoption of a fully non-adiabatic approach is strongly recommended. We also investigate the effect of specific solute–solvent interactions on the vRR spectra, by considering a cluster of cytosine, hydrogen-bonded by six water molecules, and embedded in a polarizable continuum. We show that their inclusion remarkably improves the agreement with the experiments, mainly altering the composition of the normal modes, in terms of internal valence coordinates. We also document cases, mostly for low-frequency modes, in which a cluster model is not sufficient, and more elaborate mixed quantum classical approaches, in explicit solvent models, need to be applied. [ABSTRACT FROM AUTHOR]

Aggregates of organic dyes that exhibit excitonic coupling have a wide array of applications, including medical imaging, organic photovoltaics, and quantum information devices. The optical properties of a dye monomer, as a basis of dye aggregate, can be modified to strengthen excitonic coupling. Squaraine (SQ) dyes are attractive for those applications due to their strong absorbance peak in the visible range. While the effects of substituent types on the optical properties of SQ dyes have been previously examined, the effects of various substituent locations have not yet been investigated. In this study, density functional theory (DFT) and time-dependent density functional theory (TD-DFT) were used to investigate the relationships between SQ substituent location and several key properties of the performance of dye aggregate systems, namely, difference static dipole (Δd), transition dipole moment (μ), hydrophobicity, and the angle (θ) between Δd and μ. We found that attaching substituents along the long axis of the dye could increase μ while placement off the long axis was shown to increase Δd and reduce θ. The reduction in θ is largely due to a change in the direction of Δd as the direction of μ is not significantly affected by substituent position. Hydrophobicity decreases when electron-donating substituents are located close to the nitrogen of the indolenine ring. These results provide insight into the structure–property relationships of SQ dyes and guide the design of dye monomers for aggregate systems with desired properties and performance. [ABSTRACT FROM AUTHOR]

As diseases caused by solar radiation have gained great prominence, several methods to prevent them have been developed. Among the most common, the use of sunscreens is customary and accessible. The application of theoretical methods has helped to design new compounds with therapeutic and protective functions. Natural compounds with described photoprotective potential properties (3-O-methylquercetin, gallic acid, aloin, catechin, quercetin, and resveratrol) were selected to perform theoretical studies. Computational methods were applied to predict their absorption spectra, using DFT and TD-DFT methods with functional B3LYP/6−311+g(d,p) basis sets and methanol (IEFPCM) as a solvent. The main electronic transitions of the compounds were evaluated by observing whether the differences in HOMO and LUMO energies that absorb in the UV range are UVA (320–400 nm), UVB (290–320 nm), or UVC (100–290 nm). Experimental validation was carried out for EMC, quercetin, and resveratrol, demonstrating the consistency of the computational method. Results obtained suggest that resveratrol is a candidate for use in sunscreens. The study provided relevant information about the in silico predictive power of natural molecules with the potential for use as photoprotective adjuvants, which may result in fewer time and resource expenditures in the search for photoprotective compounds. [ABSTRACT FROM AUTHOR]

Conducting poly orthophenylene diamine polymer (PoPDA) was synthesized via the oxidative polymerization route. A poly(o-phenylene diamine) (PoPDA)/titanium dioxide nanoparticle mono nanocomposite [PoPDA/TiO2]MNC was synthesized using the sol–gel method. The physical vapor deposition (PVD) technique was successfully used to deposit the mono nanocomposite thin film with good adhesion and film thickness ≅ 100 ± 3 nm. The structural and morphological properties of the [PoPDA/TiO2]MNC thin films were studied by X-ray diffraction (XRD) and scanning electron microscope (SEM). The measured optical properties of the [PoPDA/TiO2]MNC thin films such as reflectance (R) in the UV–Vis-NIR spectrum, absorbance (Abs), and transmittance (T) were employed to probe the optical characteristics at room temperatures. As well as the calculations of TD-DFT (time-dependent density functional theory), optimization through the TD-DFTD/Mol3 and Cambridge Serial Total Energy Bundle (TD-DFT/CASTEP) was employed to study the geometrical characteristics. The dispersion of the refractive index was examined by the single oscillator Wemple–DiDomenico (WD) model. Moreover, the single oscillator energy ( E o ), and the dispersion energy (Ed) were estimated. The obtained results show that thin films based on [PoPDA/TiO2]MNC can be utilized as a decent candidate material for solar cells and optoelectronic devices. The efficiency of the considered composites reached 19.69%. [ABSTRACT FROM AUTHOR]

Chloride is one of the most abundant ions in sea water, which is more available than fresh water. Due to lack of H 2 O adsorbate states near the valence band maximum (VBM) edge, the difficulty of water dissociation incidents has been reported on the rutile TiO 2 surface as the excitation energy is around the band gap energy of TiO 2 . It is interesting whether the extra chloride can be a benefit to the water dissociation or not. In this study, the models of chlorine adatoms placed on the rutile TiO 2 (110)/water interface are constructed using ab initio methods. The time-dependent spatial charges, bond-lengths of water molecules, and Hirshfeld charges are calculated by real-time time-dependent density functional theory and the Ehrenfest dynamics theory for investigating the excited state nonadiabatic dynamics of water dissociation. This study presents two photoinduced water-splitting pathways related to chlorine and analyzes the photogenerated hole along the reactions. The first step of water dissociation relies on the localized competition of oxygen charges between the dissociated water and the bridge site of TiO 2 for transforming the water into hydroxyl and hydrogen by photoinduced driving force. [ABSTRACT FROM AUTHOR]

The present contribution proposes an optical method for the detection of glyphosate (GLY) using a Cu(II) bis-(oxamate) complex ([Cu(opba)]2−) as the fluorescent probe. It wa found that in acetonitrile solution, its fluorescence increases in the presence of GLY and scales linearly (R2 = 0.99) with GLY concentration in the range of 0.7 to 5.5 µM, which is far below that established by different international regulations. The probe is also selective to GLY in the presence of potential interferents, namely aminomethyl phosphonic acid and N-nitrosoglyphosate. Theoretical results obtained by time-dependent density functional theory coupled to a simplified treatment of the liquid environment by using a self-consistent reaction-field revealed that GLY molecules do not coordinate with the central Cu2+ ion of [Cu(opba)]2−; instead, they interact with its peripheral ligand through hydrogen bond formation. Thereby, GLY plays mainly the role of the proton donor. The results also suggest that GLY increases the dielectric constant of the medium when it contributes to the stabilization of the excited state of the [Cu(opba)]2− and enhancement of its fluorescence. [ABSTRACT FROM AUTHOR]

The equilibrium and conical intersection geometries of the benzene dimer were computed in the framework of the conventional, linear-response time-dependent and spin-flipped time-dependent density functional theories (known as DFT, TDDFT and SF-TDDFT) as well as using the multiconfigurational complete active space self-consistent field (CASSCF) method considering the minimally augmented def2-TZVPP and the 6–31G(d,p) basis sets. It was found that the stacking distance between the benzene monomers decreases by about 0.5 Å in the first electronic excited state, due to the stronger intermolecular interaction energy, bringing the two monomers closer together. Intermolecular-type conical intersection (CI) geometries can be formed between the two benzene molecules, when (i) both monomer rings show planar deformation and (ii) weaker (approximately 1.6–1.8 Å long) C–C bonds are formed between the two monomers, with parallel and antiparallel orientation with respect to the monomer. These intermolecular-type CIs look energetically more favorable than dimeric CIs containing only one deformed monomer. The validity of the dimer-type CI geometries obtained by SF-TDDFT was confirmed by the CASSCF method. The nudged elastic band method used for finding the optimal relaxation path has confirmed both the accessibility of these intermolecular-type CIs and the possibility of the radiationless deactivation of the electronic excited states through these CI geometries. Although not as energetically favorable as the previous two CI geometries, there are other CI geometries characterized by the relative rotation of monomers at different angles around a vertical C–C axis. [ABSTRACT FROM AUTHOR]

Hesperidin and narirutin are a class of flavanone glycosides, which are the main active constituents in Citrus reticulata Blanco. In the present study, a chiral HPLC-UV method with amylose tris(3,5-dimethylphenylcarbamate) as a stationary phase under a normal-phase mode was used to achieve the stereoselective separation of the C-2 diastereomers of hesperidin and narirutin simultaneously. The single epimer was then successfully prepared by applying semi-preparative chromatography, whose absolute configuration (R/S) was characterized by combining the experimental electronic circular dichroism (ECD) detection with time-dependent density functional theory (TDDFT) calculations. The epimer composition of these two chiral flavanone glycosides in Citrus reticulata Blanco was then determined, which was found to be slightly different in the herbs from different production regions. The anti-inflammatory activity of each prepared single epimer was further evaluated, and some differences between one pair of epimers of hesperidin and narirutin were observed, which suggested that the presence of different epimers should be considered in the quality evaluation and control of natural medicine. [ABSTRACT FROM AUTHOR]

An organoboron small-molecular acceptor (OSMA) MB←N containing a boron–nitrogen coordination bond (B←N) exhibits good light absorption in organic solar cells (OSCs). In this work, based on MB←N, OSMA MB-N, with the incorporation of a boron–nitrogen covalent bond (B-N), was designed. We have systematically investigated the charge-transport properties and interfacial charge-transfer characteristics of MB-N, along with MB←N, using the density functional theory (DFT) and the time-dependent density functional theory (TD-DFT). Theoretical calculations show that MB-N can simultaneously boost the open-circuit voltage (from 0.78 V to 0.85 V) and the short-circuit current due to its high-lying lowest unoccupied molecular orbital and the reduced energy gap. Moreover, its large dipole shortens stacking and greatly enhances electron mobility by up to 5.91 × 10−3 cm2·V−1·s−1. Notably, the excellent interfacial properties of PTB7-Th/MB-N, owing to more charge transfer states generated through the direct excitation process and the intermolecular electric field mechanism, are expected to improve OSCs performance. Together with the excellent properties of MB-N, we demonstrate a new OSMA and develop a new organoboron building block with B-N units. The computations also shed light on the structure–property relationships and provide in-depth theoretical guidance for the application of organoboron photovoltaic materials. [ABSTRACT FROM AUTHOR]

Intermolecular interactions modulate the electro-optical properties of molecular materials and the nature of low-lying exciton states. Molecular materials composed by oligoacenes are extensively investigated for their semiconducting and optoelectronic properties. Here, we analyze the exciton states derived from time-dependent density functional theory (TDDFT) calculations for two oligoacene model aggregates: naphthalene and anthracene dimers. To unravel the role of inter-molecular interactions, a set of diabatic states is selected, chosen to coincide with local (LE) and charge-transfer (CT) excitations within a restricted orbital space including two occupied and two unoccupied orbitals for each molecular monomer. We study energy profiles and disentangle inter-state couplings to disclose the (CT) character of singlet and triplet exciton states and assess the influence of inter-molecular orientation by displacing one molecule with respect to the other along the longitudinal translation coordinate. The analysis shows that (CT) contributions are relevant, although comparably less effective for triplet excitons, and induce a non-negligible mixed character to the low-lying exciton states for eclipsed monomers and for small translational displacements. Such (CT) contributions govern the La/Lb state inversion occurring for the low-lying singlet exciton states of naphthalene dimer and contribute to the switch from H- to J-aggregate type of the strongly allowed Bb transition of both oligoacene aggregates. [ABSTRACT FROM AUTHOR]