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Recently, the new fluorescent probe 5'-amino-2-(2'-hydroxyphenyl) benzimidazole (P1) utilised in the ultrasensitive detection of phosgene based on excited-state intramolecular proton transfer (ESIPT) was synthesised experimentally (Z. J. Li et al., RSC Adv., 2021, 11, 10836). In this paper, the ESIPT process of the P1 molecule was theoretically investigated in detail by density functional theory and time-dependent density functional theory methods. The molecular structures in the ground state (S0) and the first excited state (S1) were optimised, and the infrared vibrational spectra, the frontier molecular orbitals, the potential energy curves were discussed. The calculated electronic spectra data is consistent with experimental observation. Also studied in detail is the mechanism of the ESIPT reaction, which confirms that the hydrogen bond can be enhanced in the S1 state. It will provide significant theoretical reference for future fluorescent probe experiments. Additionally, the react site is verified by calculating the electrostatic potential. ΔG < 0 indicates that the reaction of P1 with COCl2 is exothermic and occurring spontaneously. These results fully confirm that P1 is a good sensor for detecting phosgene. [ABSTRACT FROM AUTHOR]

ABSTRACT Photodynamic therapy (PDT) has been an effective tumor treatment to reduce the side effects of chemotherapy. Herein, we described the synthesis of two Ru (II) complexes by introducing a phenanthrene unit and their photocytotoxicity. Ru1 and Ru2 displayed high DNA affinities by intercalation. Under light, two complexes produced high singlet oxygen (1O2) quantum yields and cleaved DNA efficiently. Both high DNA affinities and 1O2 quantum yields of two complexes resulted in obvious photocytotoxicity towards Hela, A549, and A375 cells. Furthermore, low dark cytotoxicity was also observed for two complexes, which may promote them to act as potential PDT agents. TDDFT (Time‐dependent density functional theory) calculations also demonstrated two complexes that might display the PDT activities via 1O2 photogeneration. [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]

In the present work the effect of doping of P and Se on the reactivity and aromaticity of a few S,N-heteroacenes are discussed in the light of density functional theory (DFT) and conceptual density functional theory (CDFT). Reactivity parameters, hardness (η) and electrophilicity (ω), chemical potential (μ) and energy of the HOMO (highest occupied molecular orbital, EHOMO) are calculated to measure stability and reactive nature of the compounds. Doping of 'Se' in thiophene ring has no prominent effect on HOMO and LUMO energy (lowest unoccupied molecular orbital, ELUMO) of S,N-heteroacenes. Interestingly, there is a significant HOMO-LUMO energy gap reduction when 'N' of pyrrole ring is doped with 'P'. A steady decrease in the η values with respect to the size of the S,N-heteroacenes indicates the greater reactivity of larger acene systems. Nucleus independent chemical shift (NICS) advocates that doping of P exerts remarkable impact on the aromaticity of the concerned ring and overall aromaticity of the species. Time dependent density functional theory (TDDFT) study suggests decrease in absorption maxima with the increasing size of the oligomers. [ABSTRACT FROM AUTHOR]

Identification of a natural-based sensitizer with optimal stability and efficiency for dye-sensitized solar cell (DSSC) application remains a challenging task. Previously, we proposed a new class of sensitizers based on bio-nano hybrids. These systems composed of natural cyanidin dyes interacting with silver nanoclusters (NCs) have demonstrated enhanced opto-electronic and photovoltaic properties. In this study, we explore the doping of silver nanocluster within a cyanidin-Ag3 hybrid employing Density Functional Theory (DFT) and its time-dependent counterpart (TDDFT). Specifically, we investigate the influence of coinage metal atoms (Au and Cu) on the properties of the cyanidin-Ag3 system. Our findings suggest that cyanidin-Ag2Au and cyanidin-AgAuCu emerge as the most promising candidates for improved light harvesting efficiency, increased two-photon absorption, and strong coupling to the TiO2 surface. These theoretical predictions suggest the viability of replacing larger silver NCs with heterometallic trimers such as Ag2Au or AgAuCu, presenting new avenues for utilizing bio-nano hybrids at the surface for DSSC application. [ABSTRACT FROM AUTHOR]

The modulation of the photophysical properties of di‐substituted porphyrin rings upon the oxygen and sulfur‐for‐nitrogen replacement has been investigated at density functional theory (DFT) and its time‐dependent formulation (TDDFT). The considered properties range from structural behaviors and excitation energies to spin‐orbit coupling (SOC) and nonradiative intersystem kinetic constants. Results show that the SOC strongly increase upon chalcogen substitution and, accordingly, the computed nonradiative kinetic constant also indicate an efficient singlet‐triplet intersystem crossing in the sulfur containing macrocycle. The presented results indicate an alternative way to properly modulate the porphyrin's crucial properties for their use in photodynamic therapy, without resorting to the use of heavy atoms. [ABSTRACT FROM AUTHOR]

The novel hetero‐dinuclear complex trans,trans,trans‐[PtIV(py)2(N3)2(OH)(μ‐OOCCH2CH2CONHCH2‐bpyMe)IrIII(ppy)2]Cl (Pt‐Ir), exhibits charge transfer between the acceptor photochemotherapeutic Pt(IV) (Pt‐OH) and donor photodynamic Ir(III) (Ir‐NH2) fragments. It is stable in the dark, but undergoes photodecomposition more rapidly than the Pt(IV) parent complex (Pt‐OH) to generate Pt(II) species, an azidyl radical and 1O2. The Ir(III)* excited state, formed after irradiation, can oxidise NADH to NAD⋅ radicals and NAD+. Pt‐Ir is highly photocytotoxic towards cancer cells with a high photocytotoxicity index upon irradiation with blue light (465 nm, 4.8 mW/cm2), even with short light‐exposure times (10–60 min). In contrast, the mononuclear Pt‐OH and Ir‐NH2 subunits and their simple mixture are much less potent. Cellular Pt accumulation was higher for Pt‐Ir compared to Pt‐OH. Irradiation of Pt‐Ir in cancer cells damages nuclei and releases chromosomes. Synchrotron‐XRF revealed ca. 4× higher levels of intracellular platinum compared to iridium in Pt‐Ir treated cells under dark conditions. Luminescent Pt‐Ir distributes over the whole cell and generates ROS and 1O2 within 1 h of irradiation. Iridium localises strongly in small compartments, suggestive of complex cleavage and excretion via recycling vesicles (e.g. lysosomes). The combination of PDT and PACT motifs in one molecule, provides Pt‐Ir with a novel strategy for multimodal phototherapy. [ABSTRACT FROM AUTHOR]

In order to study the effect of substituents on the terpyridine molecular system, a series of substituted 2,2:6′,2″-terpyridines have been synthesized and fully characterized. The substitutions range from EWGs like –F to EDGs like –OMe, -NMe2, triphenylamine (TPA), heterocycles like furan and fused rings like anthracene. The –F, -OMe, and -NMe2 are connected to the terpyridine core via phenyl ring as spacer group whereas the TPA is attached via thienyl moiety. The furan and anthracene are directly appended to the terpyridine core. The synthesized terpyridines were structurally characterized with NMR and mass spectrometry. The terpyridines were then subjected to UV–Vis absorption, luminescence, and potentiometric analysis. An extension of the light harvesting window was observed for terpyridines with electron-donating groups (EDGs) as substituent. Density functional theory (DFT) based methods (B3LYP model with 6–311 G basis sets) were applied to optimize the molecular structures. The experimental absorption studies were simulated with TD-DFT based theoretical calculations (B3LYP with 6–311 G (d,p) basis set in DCM solvent using IEFPCM model) to ascertain the underlying electronic transitions. The findings were then used to define the structure-activity relationship. [ABSTRACT FROM AUTHOR]

Two new lanthanide complexes with the general formula [Ln(hqtsc)2Cl], where Ln = Eu3+/Tb3+ and hqtsc is (E)-2-((8-hydroxyquinolin-2-yl)methylene)hydrazine-1-carbothioamide have been synthesized. The structures of the complexes have been elucidated through IR, 1H NMR, 13C NMR and HR-mass spectroscopy. The coordination behavior of the ligand was investigated with proton and two trivalent lanthanides, Eu(III) and Tb(III), by potentiometric and spectrophotometric methods in a highly aqueous medium. The studies reveal that the two lanthanides form complexes of the type ML2H2, ML2H1, ML2, ML2H−1, and ML2H−2. The high formation constants of ML with log β = 26.55 and 27.13 indicate that these complexes will become promising candidates for chelation therapy, radioimmunotherapy, and other biomedical applications. Further, the change in colour and electronic spectra of the complexes in the presence of anions showed the selective colorimetric sensing ability towards H2PO4− (orange/yellow→, colorless) and CN− (orange/yellow → red). The DFT studies were also carried out to establish the structure, bonding, and sensing mechanism of the complexes. [ABSTRACT FROM AUTHOR]

Carbon dots (CDs) with a long-lifetime room-temperature phosphorescence (RTP) have received considerable attention but still remain a great challenge, especially for synthesizing visible-light-excited RTP CDs. Until now, most studies have applied isolated and chromophorous reactants to achieve visible-light-excited RTP CDs. Therefore, those strategies to modulate the excitation wavelength are not referential or reproducible. Herein, surface amination and combination with boric acid (BA, H3BO3) of CDs are applied to build long-lifetime RTP, which drives excitation light from the ultraviolet (UV) area to the visible area and gives out excitation-related afterglow. Meanwhile, surface amination promotes the intersystem crossing process, increasing the quantum yield to 18.63%. After removal of excitation light, the afterglow time visible to naked eyes can reach 10 s, with a phosphorescence lifetime of 453 ms. Furthermore, time-dependent density functional theory (TDDFT) explained the differentiated influence of surface amination on the triplet state and singlet state, which benefits the idea of realizing a wider region for excitation. Based on the above features, CDs@BA are applied in encryption with different excitation wavelengths in the advanced anticounterfeiting security field. [ABSTRACT FROM AUTHOR]

In this study, we present the synthesis of benzimidazo[1,2-a] quinoline-based heterocycles bearing organosulfur and organoselenium moieties through transition-metal-free cascade reactions involving a sequential intermolecular aromatic nucleophilic substitution (SNAr). Both sulfur and selenium derivatives presented absorption maxima located around 355 nm related to spin and symmetry allowing electronic 1π-π* transitions, and fluorescence emission at the violet-blue region (~440 nm) with relatively large Stokes shift. The fluorescence quantum yields were slightly influenced by the chalcogen, with the sulfur derivatives presenting higher values than the selenium analogs. In this sense, the quantum yields for selenium derivatives can probably be affected by the intersystem crossing or even the photoinduced electron transfer process (PET). The compounds were successfully applied in all-solution-processed organic light-emitting diodes (OLEDs), where poly(9-vinylcarbazole) was employed as a dispersive matrix generating single-layer device cells. The obtained electroluminescence spectra are a sum of benzimidazo[1,2-a]quinolines and PVK singlet and/or triplet emissive states, according to their respective energy band gaps. The best diode rendered a luminance of 25.4 cd⋅m−2 with CIE (0.17, 0.14) and current efficiency of 20.2 mcd⋅A−1, a fivefold improvement in comparison to the PVK device that was explained by a 50-fold increase of charge-carriers electrical mobility. [ABSTRACT FROM AUTHOR]

Aspirin is a commonly used nonsteroidal anti-inflammatory drug, associated with many adverse effects. The adverse effects of aspirin such as tinnitus, Reye's syndrome and gastrointestinal bleeding are caused due to conversion of aspirin into its active metabolite salicylic acid after oral intake. Glutathione is a naturally occurring antioxidant produced by the liver and nerve cells in the central nervous system. It helps to metabolize toxins, break down free radicles, and support immune function. This study aims to investigate and explore the possibility of inhibiting aspirin to salicylic acid conversion in presence of glutathione at a molecular level using spectroscopic techniques such as UV–Visible absorption, time-Resolved and time-dependent fluorescence and theoretical DFT/ TD-DFT calculations. The results of steady state fluorescence spectroscopy and time-dependent fluorescence indicated that the aspirin to salicylic acid conversion is considerably inhibited in presence of glutathione. Further, the results presented here might have significant clinical implications for individuals with variations in glutathione level. [ABSTRACT FROM AUTHOR]

Integrating plasmonic features as an emerging strategy for enhancing electrocatalysis for the carbon dioxide reduction reaction (CO2RR). The key parameters responsible for the enhanced electrocatalysis performance are the local heating, the hot carriers, and near‐field enhancement induced by localized surface plasmon resonance (LSPR, that is, plasmonic) excitation. This review provides a concise overview of the fundamental mechanism of CO2RR, detailing the generation and decay of plasmonic and the energy transfer dynamics between plasmonic nanostructures and adsorbates. It further involves recent progress in plasmonic‐assisted electrocatalysis for CO2RR, including experimental and theoretical research to decipher plasmonic mechanisms. Finally, it ends with an insightful discussion of the existing challenges and potential future directions in this field. [ABSTRACT FROM AUTHOR]

In this work, we comparatively studied the electronic and optical properties of triangular-shaped nanoflakes of VX 2 with varying flake sizes and compositions. We calculated the electronic properties using the density functional theory (DFT) while employing the time-dependent density functional theory (TD-DFT) to explore the optical properties of nanoflakes. The density of states (DOS) of VX 2 triangular nanoflakes showed the existence of localized metallic states, primarily originating from the presence of edge atoms in the flake. The optical spectra of VX 2 triangular nanoflakes revealed that the discrete peaks at low energy levels show broadening as flake size increases while splitting in resonance peaks upon changing the composition of the nanoflake. To gain insights into the nature of photoabsorption peaks, we analyzed the induced density and transition contribution map (TCM), which revealed the presence of both single-particle excitations and collective excitations. The collective excitations are known as plasmons which arise from the localized metallic edge states of the nanoflakes. This study sheds light on how nanoflakes' electronic and optical characteristics depend heavily on their shape, size, and composition. Future experiments are necessary to validate these theoretical findings. [ABSTRACT FROM AUTHOR]

'In this study, we employed density functional theory (DFT)/B3LYP method with a 6-311++G(d,p) basis set to analyze the infrared and UV spectra of a carboxylate-appended (2-pyridyl)alkylamine ligand. The FT-IR spectra were recorded within the range of 4000–500 cm-1. Geometrical parameters, energies, and wavenumbers were determined, and the fundamental vibrations were assigned based on the potential energy distribution (PED) of the vibrational modes. The UV spectrum of the compound was measured in various solvents, namely DMSO, CHCl3, and CH3OH. The 1H-NMR shifts were estimated using the GIAO method, and the results were compared to experimental spectra. To further investigate the electronic properties, including excitation energies, absorption wavelengths, and highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) energies, we employed the DFT/B3LYP approach. The degree of electron localization was assessed through analysis of the ELF diagram. Additionally, a molecular electrostatic potential (MEP) was generated, and a 3-D color representation was utilized to visualize reactive sites. Lastly, a biological study involving molecular docking was conducted using six different receptors in order to identify optimal ligand-protein interactions and assess drug similarities.' [ABSTRACT FROM AUTHOR]

Time-dependent density functional theory (TDDFT) offers a tractable means to predict electronic excitation spectra of ices if sufficient care is taken in selecting the DFT functional, basis sets, and the number of excited states. In this work 48 functionals in conjunction with various correlation consistent basis sets were benchmarked for predicting electronic spectra. A training set of important astromolecules was chosen: carbon monoxide, water, hydrogen cyanide, ammonia, methanol, and the hydroxyl radical. Vertical excitation energies between the ground and first excited state and some higher excited states were calculated using multireference configuration interaction calculations to serve as benchmarks for gas phase TDDFT calculations. When used in conjunction with aug-cc-pVDZ quality correlation consistent basis sets, two functionals, MPW1K and ωB97, emerged as very good choices to model electronic excitations for most of the molecules in the training set. Cluster calculation predictions for the UV spectra of amorphous ices of water and ammonia were performed at the TDDFT-MPW1K/AVDZ and TDDFT-ωB97/AVDZ levels and then compared against experimental data. The calculations qualitatively reproduce the shapes of the spectra for the most part and quantitatively predict the position of the critical first absorption peak. [ABSTRACT FROM AUTHOR]

'In this study, we employed density functional theory (DFT)/B3LYP method with a 6-311++G(d,p) basis set to analyze the infrared and UV spectra of a carboxylate-appended (2-pyridyl)alkylamine ligand. The FT-IR spectra were recorded within the range of 4000–500 cm-1. Geometrical parameters, energies, and wavenumbers were determined, and the fundamental vibrations were assigned based on the potential energy distribution (PED) of the vibrational modes. The UV spectrum of the compound was measured in various solvents, namely DMSO, CHCl3, and CH3OH. The 1H-NMR shifts were estimated using the GIAO method, and the results were compared to experimental spectra. To further investigate the electronic properties, including excitation energies, absorption wavelengths, and highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) energies, we employed the DFT/B3LYP approach. The degree of electron localization was assessed through analysis of the ELF diagram. Additionally, a molecular electrostatic potential (MEP) was generated, and a 3-D color representation was utilized to visualize reactive sites. Lastly, a biological study involving molecular docking was conducted using six different receptors in order to identify optimal ligand-protein interactions and assess drug similarities.' [ABSTRACT FROM AUTHOR]

We present the design and implementation of libkrylov, an open-source library for solving matrix-free eigenvalue, linear, and shifted linear equations using Krylov subspace methods. The primary objectives of libkrylov are flexible API design and modular structure, which enables integration with specialized matrix-vector evaluation "engines." Libkrylov features pluggable preconditioning, orthonormalization, and tunable convergence control. Diagonal (conjugate gradient, CG), Davidson, and Jacobi-Davidson preconditioners are available, along with orthonormal and nonorthonormal (nKs) schemes. All functionality of libkrylov is exposed via Fortran and C application programming interfaces (APIs). We illustrate the performance of libkrylov for eigenvalue calculations arising in time-dependent density functional theory (TDDFT) in the Tamm-Dancoff approximation (TDA) and discuss the convergence behavior as a function of preconditioning and orthonormalization methods.

Myricetin is a flavonol with high antioxidant properties. In this research, the fluorescence emission of myricetin powder and its solutions in different solvents were measured and analyzed by comparing with the results of calculations. Comparison of the calculated and measured characteristic wavelengths allowed the identification of all the spectral features in the fluorescence spectra of myricetin powder and solutions with different concentrations. The computation was based on modeling the process of the excited state intermolecular proton transfer, which predicts the formation of tautomeric forms of the flavonol molecule. Characteristic emission wavelengths were obtained using TDDFT/M06-2X/6-31++G(d,p). To understand the influence of the hydroxyl groups in the B-ring of the flavonol molecule on the emission spectrum, we also compared the fluorescence spectra of myricetin with those of kaempferol and quercetin. Moreover, based on the analysis of the changes in the shape of the FL spectra with the concentration of the solution, a criterion for the complete dissolution of the flavonol powders was established, which is important for bioavailability of flavonoids. [ABSTRACT FROM AUTHOR]

Context: The study of molecular aggregation effects on the electronic spectrum is essential for the development of optoelectronic devices. However, investigating the entire valence absorption spectrum of aggregates using quantum mechanical methods is a challenging task. In this work, we perform systematic simulations of the absorption spectrum of benzene molecular clusters up to 35 eV applying two approaches based on time-dependent density functional theory. The results show that depending on the dimer packing, different energy shifts occur for the symmetry allowed π → π ∗ transition, in comparison to the monomer. The transition intensity increases for the band around 6 eV for larger aggregates from the monomer to dimers and tetramer, indicating the occurrence of the symmetry forbidden (in D 6 h point group) 1 A 1 g → 1 B 1 u transition. The benzene crystal exhibits a large redshift following the experimental spectrum. Also, the continuum regions of all spectra show a good agreement with the experiments both in gas and solid phases. Methods: Geometry optimization of the monomer was carried out with Gaussian 09 software using the PBE0/def2-TZVP level of theory. We used dimers and tetramer molecular geometries extracted from the experimental crystal structure. The absorption spectra were directly obtained by the Liouville-Lanczos TDDFT approach with plane waves basis set or indirectly by TDDFT pseudo-spectra calculated in a L 2 basis followed by analytic continuation procedure to obtain complex polarizability. The former is available at Quantum ESPRESSO, and the latter was calculated using Gaussian 09 with the post-processing performed with a code previously developed in our group. [ABSTRACT FROM AUTHOR]

The BODIPY based molecules show promising properties towards bioimaging applications due to its structural flexibility and versatile optoelectronic characteristic features. Among many strategies in the development of such molecules, fusion of heterocyclic units into the BODIPY core structure is vital in tuning the π‐delocalization and spectral properties. Recently reported Thieno [3,2b] Thiophene based BODIPY (TTB) attracts a lot of attention while the caliber of their Selenophene derivatives are interesting and yet to be explored. Therefore, a systematic replacement of Sulphur by Selenium has been done on TTB and seven new selenophene fused TTB molecules are computationally designed and evaluated for their optoelectronic properties towards bioimaging of CDK2 kinase tumor cells. The optimized geometries indicate that all these molecules are showing excellent π‐delocalization and further stabilized by a range of intra‐molecular C−H−F and B−F−S/Se interactions. Molecular docking studies show that these TTB molecules are potential inhibitors and can be used for lung tumor imaging in biomedical applications. Molecular Dynamics analysis confirms their preferential binding inside the active site up to 100 ns. In summary, this study highlights the importance of Se replacement in designing new BODIPY‐based bioimaging candidates with excellent near‐IR luminescence and photo sensitizers for future biomedical applications. [ABSTRACT FROM AUTHOR]

The compound 3,4‐diaminopyridine (3,4‐AP), a derivative of 4‐aminopyridine (4‐AP), is used in the symptomatic treatment of fatigue in multiple sclerosis as well as Lambert–Eaton myasthenia syndrome whereas the parent compound 4‐AP is used as an acetylcholine‐releasing drug, in serum, saliva, and urine. 4‐AP is an experimental drug that may reduce symptoms in some people with multiple sclerosis, particularly those who are more sensitive to heat. The carbon nanotubes (CNTs) have inside cavity tethering on the surface upon functionalization and adsorption on the walls of CNTs, which provides extra ability to carry pharmaceutical agents through multiple ways. Due to these benefits, this communication will discuss the comparative changes in geometry, electronic properties, and shielding parameters of 4‐AP and 3,4‐AP absorbed C56H16. The DFT/B3LYP/6–31G (d, p) method is used for the first time to report electronic structure and interaction parameters on the CNT surface. The same level theory is used to discuss the thermodynamic stability of CNT‐4‐AP/3,4‐AP. The calculated UV spectra of CNT are compared with UV spectra of CNT‐4‐AP and 3,4‐AP by using the same level theory in a water solvent, which provides a better comprehension of CNT as a drug delivery system after absorption of the 4‐AP and 3,4‐AP in the human body. The nature and strength of interactions have been discussed with the help of AIM analysis, and the frontier orbital highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) gap, chemical softness, and chemical hardness have been calculated to understand its complete chemical properties. The characters of the frontier molecular orbitals are discussed and analyzed by comparing the DOS spectra of CNT with CNT‐4‐AP/3,4‐AP. [ABSTRACT FROM AUTHOR]

Lead-free perovskites are among the compounds that are currently the most investigated for their potential application in photovoltaics because of their nontoxic effect on the environment. In this work, we report the structural, electronic, and optical properties of hybrid organic-inorganic FAMgI3-based perovskite for use in photovoltaic technology. We use density functional theory (DFT) and time-dependent density functional theory (TDDFT) executed in the Quantum Espresso framework. These calculations were performed by applying the generalized gradient approximation of Perdew–Burke–Ernzerhof (GGA-PBE), the GGA-PBE revised for solids (GGA-PBESol), and local density approximation (LDA). The band structure and total and partial density of states (DOS and PDOS) of this perovskite are elaborated and discussed; the semiconductor behavior and direct band gap of this material are demonstrated. In addition, we investigated the effect of spin–orbit coupling (SOC) correction on the band gap energy and demonstrated that the band gap energy was reduced by the SOC effect. In fact, when using the GGA-PBE in the absence of SOC, the calculated band gap energy was 1.4 eV. When including the SOC effect, it is demonstrated that the band gap energy decreases to 1.01 eV. Moreover, the optical properties have been presented and discussed. The material also exhibits excellent optical properties, including high absorption, and can therefore be used in the development of lead-free perovskite solar cells and other optoelectronic applications. [ABSTRACT FROM AUTHOR]

Decaniobate is a polyoxoniobate considered in photocatalytic studies lacking more detailed electronic transition data. Moreover, its stability in aqueous solution depends on the pH and little is known regarding the protonation of this polyanion. Hence, this electronic structure study based on Density Functional Theory calculations shows that initial protonations occur at specific external oxygen sites situated above and below the equatorial plane of the polyanion [Oe(A)]. Moreover, these Oe(A) protonations cause small perturbations to the inner core structural skeleton constituted by bonds between niobium and internal oxygen atoms via a trans effect. The ultraviolet/visible spectra are slightly affected by these protonations as well, exhibiting a general trend for formation of four main bands in the range from 150 to 250 nm with similar positions and relative intensity profiles. The nature of the lowest energy electronic transitions (231 to 249 nm) indicates that these are charge transfer bands mainly from bridging oxygen to niobium atoms, with an amount of electronic charge received by metal atoms nearly unaltered by the protonations (from 0.32 to 0.38 e). [ABSTRACT FROM AUTHOR]

A new green procedure has been applied for the synthesis and purification of asymmetric monomethine cyanine dyes. The photophysical properties of the newly synthesized compounds have been examined by combined application of spectroscopic and theoretical methods. The structural characteristics of the molecules and dimer formation were characterized by quantum chemical computation and juxtaposed to the aggregachromism in UV/Vis spectra. The applicability of the dyes as fluorogenic nucleic acid probes has been proven by fluorescence titration, and their binding constants have been calculated. The mode of ligand–dsDNA/RNA interaction was rationalized by means of CD spectroscopy, molecular docking analysis, and fluorescent intercalator displacement experiments. [ABSTRACT FROM AUTHOR]

First-principles calculations have been performed on (HfO 2) p and Hf q Zr r O 2 (q + r) clusters using DFT and TDDFT. The effect of Zr-substitution on the structural, electronic, thermodynamic, and optical properties of (HfO 2) p clusters has been investigated using B3LYP and B3PW91 functionals with LANL2DZ basis set. The calculated properties depend upon geometry, type, and number of atoms present in the clusters. Zr-substitution in (HfO 2) p clusters leads to the reduced molecular mass of Hf q Zr r O 2 (q + r) clusters so that they can be used in making light weight semiconductor devices. Hf 3 Zr 2 O 10 is found to be the most reactive after Zr-substitution in (HfO 2) 5 because of the minimum value of HOMO-LUMO gap. Zr-substitution in (HfO 2) 5 increases the refractive index of Hf 3 Zr 2 O 10 , making it suitable for multi-layer antireflecting coatings. The dielectric constant of Hf 3 Zr 2 O 10 has increased after Zr-substitution finding applications in the MOSFET industry. The absorption spectra can be tuned over the ultraviolet and visible regions depending upon the Zr-substitution. [ABSTRACT FROM AUTHOR]

Abstract Integrating plasmonic features as an emerging strategy for enhancing electrocatalysis for the carbon dioxide reduction reaction (CO2RR). The key parameters responsible for the enhanced electrocatalysis performance are the local heating, the hot carriers, and near‐field enhancement induced by localized surface plasmon resonance (LSPR, that is, plasmonic) excitation. This review provides a concise overview of the fundamental mechanism of CO2RR, detailing the generation and decay of plasmonic and the energy transfer dynamics between plasmonic nanostructures and adsorbates. It further involves recent progress in plasmonic‐assisted electrocatalysis for CO2RR, including experimental and theoretical research to decipher plasmonic mechanisms. Finally, it ends with an insightful discussion of the existing challenges and potential future directions in this field.

The primary purpose of this research is to examine how the presence of thermal features variation affects the velocity and heat transfer rate of nanofluids composed of sodium alginate and molybdenum disulfide [Na-Alg/MoS2]m and sodium alginate and molybdenum disulfide and graphene oxide [Na-Alg/MoS2 + GO]h, respectively, flowing between two rotating, permeable plates. Both centripetal and Coriolis forces, which act on a spinning fluid, are taken into account. The impacts of magnetized force, thermal radiative flux, heat source (sinking), and varied pressure in the Darcy–Forccheimer material are considered. Using the physical vapor deposition method, single and hybridity nanofluid thin films of thickness 150 ± 5 nm may be created. The controlling mathematical equations of the suggested model are solved using the Keller-box technique in MATLAB software. The surface friction coefficient of a hybrid nanofluid is less, and the heat transfer rate is greater than that of a regular nanofluid. The rate of heat transmission is slowed by the rotational parameter. The thermal efficiency of mono nanofluids is as low as 6.16% and as high as 21.88% when compared to those of hybrid nanofluids. In particular, the findings of density functional theory (DFT) calculations reveal that the energy bandgap ΔEgOpt\Delta {E}_{{\rm{g}}}^{{\rm{Opt}}} drops from 1.641 eV for conventional nanofluid to 0.185 eV for hybridity nanofluid. Based on the findings, the addition of graphene oxide nanoparticles to the base nanofluid converts it from a semi-conductor to a hybridity nanofluid as a superconductor.

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.

Time‐dependent density functional theory (TDDFT) was applied to gain insights into the electronic and vibrational spectroscopic properties of an important electron transport mediator, methyl viologen (MV2+). An organic dication, MV2+ has numerous applications in electrochemistry that include energy conversion and storage, environmental remediation, and chemical sensing and electrosynthesis. MV2+ is easily reduced by a single electron transfer to form a radical cation species (MV•+), which has an intense UV–visible absorption near 600 nm. The redox properties of the MV2+/MV•+ couple and light‐sensitivity of MV•+ have made the system appealing for photo‐electrochemical energy conversion (e.g., solar hydrogen generation from water) and the study of photo‐induced charge transfer processes through electronic absorption and resonance Raman spectroscopic measurements. The reported work applies leading TDDFT approaches to investigate the electronic and vibrational spectroscopic properties of MV2+ and MV•+. Using a conventional hybrid exchange functional (B3‐LYP) and a long‐range corrected hybrid exchange functional (ωB97X‐D3), including with a conductor‐like polarizable continuum model to account for solvation, the electronic absorption and resonance Raman spectra predicted are in good agreement with experiment. Also analyzed are the charge transfer character and natural transition orbitals derived from the TDDFT vertical excitations calculated. The findings and models developed further the understanding of the electronic properties of viologens and related organic redox mediators important in renewable energy applications and serve as a reference for guiding the interpretation of electronic absorption and Raman spectra of the ions. [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]

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Partially reduced silver clusters growing in a polycytosine matrix could simultaneously possess stabilizing ability and remarkable optical features. The mechanisms of this phenomenon are not fully understood so far. We examined the thermodynamic stability of a cytosine–silver associate comprising four cytosines and three silver atoms that can be considered the smallest known luminescent silver marker stabilized on DNA. Quantum and molecular mechanical representations thermodynamic integration toward the dissociation pathway of the cytosine tetramer, time‐dependent density functional theory calculations of the lowest energy excited states and quantum theory of atoms in molecules analysis of bonding showed that the reduction of two ions within the silver trimer mediating cytosine tetramer leads to the appearance of the green‐emitting silver cluster with low stabilization ability of cytosines relative to a tetramer stabilized by two silver ions. [ABSTRACT FROM AUTHOR]

A DFT and TDDFT study has been carried out on Red Nile dye (RN) and on two chalcogens-derivatives in which the carbonyl-oxygen was replaced by Sulfur-(SNR) and Selenium-(SeNR) in order to evaluate the effect of such substitution on their photophysical properties. Inspection of Type I and Type II photoreactions have been achieved exploring the absorption properties, computing spin–orbit coupling, proposing the most plausible deactivation channels leading to the population of excited triplet states and through the analysis of vertical electron affinities and ionization potentials. Our data show a useful bathochromic shift of the lowest energy 1ππ* absorption band as the size of the substituted atom increases combined with an enhancement of the SOC values for the main nπ* → ππ* S1 → T1 deactivation pathways, suggesting a more efficient ISC mechanism for the thio- and seleno-dye. Moreover, the introduction of selenium in the NR dye has the intriguing effect to promote also the electron transfer reaction producing the O2(−)• species through the TypeI mechanism, allowing us to propose that designed dye as a dual TypeI/II PS. Our study supports the strategy to afford heavy-atom effect by using chalcogens showing as it could be successfully exploited to achieve metal-free PSs with desirable properties. [ABSTRACT FROM AUTHOR]

Computational studies of cyanidin and peonidin, and related anthocyanin: cyanidin-3-O glucoside (cya-3-O-glu) and peonidin-3-O glucoside (peo-3-O-glu) were performed to identify the dye potential in order to use in dye-sensitized solar cells (DSSCs). B3LYP/6-31+G(d, p) level of theory was used for ground state optimization and chemical properties estimation of the dyes. The absorption spectra, excited states, and optical parameters were obtained using TDDFT with the same functional and basis set. The dyes properties in water and ethanol as solvent were evaluated at the same level of theory for ground and excited states. The results have shown that the studied dyes, under the effects of solvents, can be used in DSCCs but not in the gas phase. Water and ethanol have the same effect on the chemical properties and absorption spectrum of the dyes. The hardness and ionization potential of peonidin have the lowest value. Also, light harvesting efficiency of it has the highest value. Electron injection from photoexcited dye to the conduction band of the semiconductor was done spontaneously with a negative value of ΔGinject as free energy change of electron inject process in order peo-3-O-glu < peo < cya-3-O-glu < cya. Therefore, all the studied dyes are suitable for application in DSSC technology, but peonidin and its glycoside form have higher efficiency. [ABSTRACT FROM AUTHOR]

Recent developments in the simulations of processing of semiconductors and metals by femto- (10-15) second pulse laser, especially silicon and aluminum, are presented. Laser processing is a complex process involving nonlinear phenomena. We have developed microscopic first-principles calculations that describe the light-electron interaction, the semiclassical Vlasov equation that can also include relaxation in metal, and a novel temperature model that allows us to study the entire initial processing process. Each method allows us to analyze the entire process from the moment of laser irradiation to the stage of energy transfer to the lattice. This paper describes the details of the methods and the findings obtained from the results. [ABSTRACT FROM AUTHOR]

Direct simulation of the von Neumann dynamics for a general (pure or mixed) quantum state can often be expensive. One prominent example is the real-time time-dependent density functional theory (rt-TDDFT), a widely used framework for the first principle description of many-electron dynamics in chemical and materials systems. Practical rt-TDDFT calculations often avoid the direct simulation of the von Neumann equation, and solve instead a set of Schrödinger equations, of which the dynamics is equivalent to that of the von Neumann equation. However, the time step size employed by the Schrödinger dynamics is often much smaller. In order to improve the time step size and the overall efficiency of the simulation, we generalize a recent work of the parallel transport (PT) dynamics for simulating pure states [An, Lin, Multiscale Model. Simul. 18, 612, 2020] to general quantum states. The PT dynamics provides the optimal gauge choice, and can employ a time step size comparable to that of the von Neumann dynamics. Going beyond the linear and near adiabatic regime in previous studies, we find that the error of the PT dynamics can be bounded by certain commutators between Hamiltonians, density matrices, and their derived quantities. Such a commutator structure is not present in the Schrödinger dynamics. We demonstrate that the parallel transport-implicit midpoint (PT-IM) method is a suitable method for simulating the PT dynamics, especially when the spectral radius of the Hamiltonian is large. The commutator structure of the error bound, and numerical results for model rt-TDDFT calculations in both linear and nonlinear regimes, confirm the advantage of the PT dynamics.

Identification of a natural-based sensitizer with optimal stability and efficiency for dye-sensitized solar cell (DSSC) application remains a challenging task. Previously, we proposed a new class of sensitizers based on bio-nano hybrids. These systems composed of natural cyanidin dyes interacting with silver nanoclusters (NCs) have demonstrated enhanced opto-electronic and photovoltaic properties. In this study, we explore the doping of silver nanocluster within a cyanidin-Ag3 hybrid employing Density Functional Theory (DFT) and its time-dependent counterpart (TDDFT). Specifically, we investigate the influence of coinage metal atoms (Au and Cu) on the properties of the cyanidin-Ag3 system. Our findings suggest that cyanidin-Ag2Au and cyanidin-AgAuCu emerge as the most promising candidates for improved light harvesting efficiency, increased two-photon absorption, and strong coupling to the TiO2 surface. These theoretical predictions suggest the viability of replacing larger silver NCs with heterometallic trimers such as Ag2Au or AgAuCu, presenting new avenues for utilizing bio-nano hybrids at the surface for DSSC application.

The scientific community has shown significant interest in organic materials due to their potential applications in optoelectronics. In this study, we present the design and theoretical investigation of a new class of carbazole-based organic chromogens (R1-6). These chromogens consist of a heteroaromatic carbazole unit as an electron-rich donor, connected to a substituted phenyl ring carrying various electron acceptor groups. Specifically, we analyse the structural impact of electron withdrawing moieties such as carboxylic acid (–COOH), cyano (–CN), and nitro (–NO2) on the photophysical properties of these chromogens. To gain insights into the electron density localization and charge transfer characteristics, we perform DFT, TD-DFT, and MESP calculations. The computational studies indicate that these materials exhibit promising potential as sensitizers for applications in dye-sensitized solar cells (DSSCs).

Cannabicitran is a cannabinoid found in levels up to ~10% in commercial "purified" cannabidiol (CBD) extracts. The structure of this natural product was first reported more than 50 years ago. However, few studies have investigated cannabicitran or its origin despite the rapidly increasing interest in the use of cannabinoids for the treatment of a wide range of physiological conditions. Following on a recent detailed NMR and computational characterization of cannabicitran, our group initiated ECD and TDDFT studies aimed at unequivocally determining the absolute configuration of cannabicitran present in Cannabis sativa extracts. To our surprise, we discovered the natural product was racemic, raising questions around its presumed enzymatic origin. Herein, we report the isolation and absolute configuration of (−)‐cannabicitran and (+)‐cannabicitran. Several possible scenarios for production of the racemate in the plant and/or during extract processing are discussed. [ABSTRACT FROM AUTHOR]

Water-insoluble organic UV filters like tris-biphenyl-triazine (TBPT) can be prepared as aqueous dispersions of nanoparticles. The particles consist of the respective UV absorber molecules and show strong UV absorbance. Since there is a certain solubility of such UV absorbers in organic solvents, it is possible to measure the absorbance spectrum also in solution, for instance in ethanol or dioxane. The UV spectrum of the aqueous dispersion shows a slight hypsochromic shift of the original band with an additional shoulder at longer wavelengths. For the understanding of the observed changes of UV–Vis spectra of this UV absorber, either dissolved in an organic solvent or dispersed as nanoparticles in water, DFT calculations were carried out with the respective monomer and aggregates of TBPT molecules in the different media. The calculated UV–Vis spectra of isolated, that means dissolved, TBPT molecules in ethanol and in dioxane agree well with experimentally observed ones. The observed changes in the shape of experimental UV–Vis spectra in aqueous dispersion cannot be explained with a solvent effect only. It was found that the studied molecules could form stable energetically favorable π-stacked aggregates, which show UV–Vis spectra in reasonable agreement with those experimentally observed in aqueous dispersion. Such aggregates of TBPT are most likely the reason for the observed additional shoulder in the UV/vis absorbance spectrum. In addition, the mechanism of the photochemical deactivation of excited TBPT molecules was studied in detail with TD DFT in dioxane and in water. [ABSTRACT FROM AUTHOR]

The realization of both thermally activated delayed fluorescence (TADF) and room-temperature phosphorescence (RTP) from a single molecule is highly advantageous for efficient light-emitting diodes (LEDs). In this work, we have studied a donor core-substituted pyromellitic diimide (CzPhPmDI) derivative which shows both RTP and TADF. Apart from CzPhPmDI, we have studied heavy atom-substituted (on both donor and acceptor) CzPhPmDI and methyl-substituted spacer for improved RTP and TADF emissions. In the optimized geometry of CzPhPmDI, phenyl spacer is not completely perpendicular to both donor and acceptor, and dihedral angle is nearly 600. From the dihedral angle-dependent studies of excited state property, we have found that a gradual increment of dihedral angle (more perpendicular to both Cz and PmDI) leads to lowering of singlet–triplet (ΔEST) gap initially, but later it further increases the singlet–triplet gap (spacer is nearly perpendicular). With Me substitution on spacer (in CzMe2PhPmDI), the spacer becomes perpendicular to both Cz and PmDI groups. The increased ΔEST can be attributed to different excitation natures of S1 and T1. Further investigation suggests that it leads to the formation of a twisted intramolecular charge transfer (TICT) state with increased coplanarity of the spacer with both the Cz and PmDI unit, which eventually leads to TADF with redshifted bright emission. While heavy atom substitution on donor does not influence the excited state characteristics, Br substitution on PmDI increases the spin–orbit coupling strength leading to improved intersystem and reverse intersystem crossing, which is beneficial for efficient RTP and TADF. [ABSTRACT FROM AUTHOR]

The design of highly efficient sensitizers is one of the most significant areas in dye-sensitized solar cell (DSSC) research. We studied a series of benzothiadiazole-based D-π-π-A organic dyes, putting emphasis on the influence of the donor moiety on the DSSC's efficiency. Using (linear-response time-dependent) density functional theory ((TD)DFT)) with the CAM-B3LYP functional, different donor groups were characterized in terms of electronic absorption spectra and key photovoltaic parameters. As a reference, a dye was considered that had a benzothiadiazole fragment linked via thiophene rings to a diphenylamine donor and a cyanoacrylic-acid acceptor. The different systems were first studied in terms of individual performance parameters, which eventually aggregated into power conversion efficiency. Only the amino-substituted species showed a modest increase, whereas the dimethylamino case showed a decrease. [ABSTRACT FROM AUTHOR]

In this work, we use UV-Vis and Raman spectroscopy to correlate the intensity of selected transitions to the onset of aggregation phenomena. Through TDDFT calculations, we rationalize the formation of H-aggregates and their influence on the observed changes in the UV-Vis spectra. A correlation between Raman intensity and the molar absorption coefficient is experimentally observed and theoretically rationalized. We develop this method by considering Disperse Orange 3 (DO3), a well-known push–pull azobenzene dye with strong optical absorption in the blue–green region of the visible spectrum, and the known tendency to form H-aggregates. [ABSTRACT FROM AUTHOR]