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Identifying the oxidation structure of two-dimensional interfaces is crucial to improve surface chemistry and electronic properties. Beyond graphene with only phenyl rings, a novel carbon-nitrogen material, C3N, presents an intrinsic heterogeneous surface morphology where each phenyl ring is encircled by six nitrogen atoms, yet its atomistic oxidation structure remains unclear. Here, combining a series of density functional theory calculations and ab initio molecular dynamics simulations, we demonstrate that thermodynamically favorable oxidation loci are confined to the phenyl ring, and kinetic transformations of oxidation structures are feasible along the phenyl ring, whereas those toward nitrogen atoms are proven to be extremely difficult. These results are attributed to the lower barrier of oxygen atom migration along the phenyl ring, while the significantly high barriers toward nitrogen atoms are due to the heterogeneous potential energy surface for oxygen–C3N interaction. This work highlights the significance of surface morphology on the characteristics of oxidation structure, offering insights into tunable electronic properties via confined interfacial oxidation. [ABSTRACT FROM AUTHOR]

Wave packet interferometry with vacuum ultraviolet light has been used to probe a complex region of the electronic spectrum of molecular nitrogen, N2. Wave packets of Rydberg and valence states were excited by using double pulses of vacuum ultraviolet (VUV), free-electron-laser (FEL) light. These wave packets were composed of contributions from multiple electronic states with a moderate principal quantum number (n ∼ 4–9) and a range of vibrational and rotational quantum numbers. The phase relationship of the two FEL pulses varied in time, but as demonstrated previously, a shot-by-shot analysis allows the spectra to be sorted according to the phase between the two pulses. The wave packets were probed by angle-resolved photoionization using an infrared pulse with a variable delay after the pair of excitation pulses. The photoelectron branching fractions and angular distributions display oscillations that depend on both the time delays and the relative phases of the VUV pulses. The combination of frequency, time delay, and phase selection provides significant control over the ionization process and ultimately improves the ability to analyze and assign complex molecular spectra. [ABSTRACT FROM AUTHOR]

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

We present a detailed theoretical analysis of polarized absorption spectra and linear dichroism of cyanine dye aggregates whose unit cells contain two molecules. The studied threadlike ordered system with a molecular exciton delocalized along its axis can be treated as two chains of conventional molecular aggregates, rotated relative to each other at a certain angle around the aggregate axis. Our approach is based on the general formulas for the effective cross section of light absorption by a molecular aggregate and key points of the molecular exciton theory. We have developed a self-consistent theory for describing the orientational effects in the absorption and dichroic spectra of such supramolecular structures with nonplanar unit cell. It is shown that the spectral behavior of such systems exhibits considerable distinctions from that of conventional cyanine dye aggregates. They consist in the strong dependence of the relative intensities of the J- and H-type spectral bands of the aggregate with a nonplanar unit cell on the angles determining the mutual orientations of the transition dipole moments of constituting molecules and the aggregate axis as well as on the polarization direction of incident light. The derived formulas are reduced to the well-known analytical expressions in the particular case of aggregates with one molecule in the unit cell. The calculations performed within the framework of our excitonic theory combined with available vibronic theory allow us to quite reasonably explain the experimental data for the pseudoisocyanine bromide dye aggregate. [ABSTRACT FROM AUTHOR]

Doubly resonant sum frequency generation (DR-SFG) serves as a potent characteristic technique for probing the electronic spectra and vibronic coupling of molecules on surfaces. In this study, we successfully developed a novel infrared (IR)–white light (WL) DR-SFG spectroscopy based on narrowband IR and tunable broadband WL. This novel method was employed to explore the excitation spectrum and vibronic couplings of sub-monolayer Rhodamine 6G molecules. Our findings elucidate that the xanthene skeleton vibrational modes exhibit strong coupling with the S0–S1 electronic transition. Notably, we observed not only the 0–0 transition of the S0–S1 electronic continuum but also the 0–1 transition, a first time observation in the realm of DR-SFG spectroscopy. This advanced DR-SFG spectroscopy methodology facilitates a more sensitive examination of electronic spectra and the coupling between electronic transitions and vibrational modes, heralding a significant advancement in the understanding of molecular interactions on surfaces. [ABSTRACT FROM AUTHOR]

To spectroscopically qualify strength in the π-electron conjugation, the electronic spectra of jet-cooled 1,4-bis(phenylethynyl)benzene (BPEB) in the region of the transition to the lowest excited singlet (S1) 1B1u state are measured by the fluorescence excitation and the single-vibronic-level dispersed fluorescence methods. Strength is defined as the difference in potential energies between the planar and perpendicular conformations. BPEB possesses two large-amplitude torsional motions, out-of-phase 24 and in-phase 29 modes. The most stable is the planar conformation, and barrier heights at the perpendicular conformation are coincident in torsional potentials for the two modes. Torsional levels are successively observed up to 19± and 16− quantum levels in the ground state, respectively. Strength is determined to be 293 cm−1 (3.51 kJmol−1) with an accuracy of an error range smaller than 1 cm−1. In the excited state, strength is estimated to be 1549 ± 73 cm−1. Combination levels of two torsional modes are also measured up to high quantum levels. A systematic decrease in frequencies is observed with increasing the quantum number. Quantum-chemistry calculations of B3LYP, CAM-B3PLYP, WB97XD, and M062X with basis sets of aug-cc-pVDZ are performed, where B3LYP theories are carried out with the dispersion correlation. The calculated strength is 1.1–2.1 times larger than observed. [ABSTRACT FROM AUTHOR]

Ultraviolet and vacuum ultraviolet photo-absorption spectra of azido (–N3)-based energetic plasticizer, bis(1,3-diazido-prop-2-yl)-malonate (abbreviated as BDAzPM), in the gas phase is recorded at room temperature and in the photon energy range of 5.5–9.9 eV using a synchrotron radiation source. Complementary computational results obtained using the time-dependent density functional theory document the vertical transition energies and oscillator strengths. Comparison of the simulated spectra with the experimental absorption spectrum of BDAzPM reveals that the early part of the absorption spectrum of BDAzPM is of pure valence excitation character, whereas the later intense part of the absorption spectrum is dominated by mixed Rydberg and valence electronic excitations. [ABSTRACT FROM AUTHOR]

Time-resolved pump–probe and two-dimensional spectroscopy are widely used to study ultrafast chemical and biological processes in solutions. However, the corresponding signals at long times can be contaminated by molecular photothermal effects, which are caused by the nonradiative heat dissipation of photoexcited molecules to the surroundings. Additionally, molecular diffusion affects the transient spectroscopic signals because photoexcited molecules can diffuse away from the pump and probe beam focuses. Recently, a theoretical description of molecular photothermal effects on time-resolved IR spectroscopy was reported. In this work, I consider the molecular photothermal process, molecular diffusion, and sample flow to develop a generalized theoretical description of time-resolved spectroscopy. The present work can be used to interpret time-resolved spectroscopic signals of electronic or vibrational chromophores and understand the rate and mechanisms of the conversion of high-frequency molecular electronic and vibrational energy to solvent kinetic energy in condensed phases. [ABSTRACT FROM AUTHOR]

Nonlinear optical methods, such as vibrational sum frequency generation (vSFG) and second harmonic generation (SHG), are powerful techniques to study elusive structures at charged buried interfaces. However, for the separation and determination of the Stern and diffuse layer spectra at these charged interfaces, complex vSFG spectra and, hence, the absolute phase need to be retrieved. The maximum entropy method is a useful tool for the retrieval of complex spectra from the intensity spectra; however, one caveat is that an understanding of the error phase is required. Here, for the first time, we provide a physically motivated understanding of the error phase. Determining the error phase from simulated spectra of oscillators with a spectral overlap, we show that for broadband vSFG spectra, such as for the silica/water interface, the diffuse and Stern layers' spectral overlap within the O–H stretching window results in a correlation between the error phase and the phase shift between the responses of these layers. This correlation makes the error phase sensitive to changes in Debye length from varying the ionic strength among other variations at the interface. Furthermore, the change in the magnitude of the error phase can be related to the absolute SHG phase, permitting the use of an error phase model that can utilize the SHG phase to predict the error phase and, hence, the complex vSFG spectra. Finally, we highlight limitations of this model for vSFG spectra with a poor overlap between the diffuse and Stern layer spectra (silica/HOD in D2O system). [ABSTRACT FROM AUTHOR]

Computational optimal transport is used to analyze the difference between pairs of continuous molecular spectra. It is demonstrated that transport distances which are derived from this approach may be a more appropriate measure of the difference between two continuous spectra than more familiar measures of distance under many common circumstances. Associated with the transport distances is the transport map which provides a detailed analysis of the difference between two molecular spectra and is a key component of our study of quantitative differences between two continuous spectra. The use of optimal transport for comparing molecular spectra is developed in detail here with a set of model spectra, so that the discussion is self-contained. The difference between the transport distance and more common definitions of distance is elucidated for some well-chosen examples and it is shown where transport distances may be very useful alternatives to standard definitions of distance. The transport distance between a theoretical and experimental electronic absorption spectrum for SO2 is studied and it is shown how the theoretical spectrum can be modified to fit the experimental spectrum better adjusting the theoretical band origin and the resolution of the theoretical spectrum. This analysis includes the calculation of transport maps between the theoretical and experimental spectra suggesting future applications of the methodology. [ABSTRACT FROM AUTHOR]

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

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

We develop an accurate and numerically efficient non-adiabatic path-integral approach to simulate the non-linear spectroscopy of exciton–polariton systems. This approach is based on the partial linearized density matrix approach to model the exciton dynamics with explicit propagation of the phonon bath environment, combined with a stochastic Lindblad dynamics approach to model the cavity loss dynamics. Through simulating both linear and polariton two-dimensional electronic spectra, we systematically investigate how light–matter coupling strength and cavity loss rate influence the optical response signal. Our results confirm the polaron decoupling effect, which is the reduced exciton–phonon coupling among polariton states due to the strong light–matter interactions. We further demonstrate that the polariton coherence time can be significantly prolonged compared to the electronic coherence outside the cavity. [ABSTRACT FROM AUTHOR]

We present a theoretical study on the structural and electronic properties of the p-dimethylamino-cinnamaldehyde (DMACA) merocyanine molecule in solvents of different polarities by combining the free energy gradient and the average solvent electrostatic configuration methods via an iterative procedure based on the sequential quantum mechanics/molecular mechanics hybrid methodology. Studying such a system in solution is a crucial step for understanding the solvent effects on its properties, which can have implications in fields such as optoelectronics and biophysics. We found that the DMACA molecule presents different geometries in nonpolar and polar solvents, changing from a polyene-like structure with a pyramidal dimethylamino group (in gas phase or nonpolar solvents) to a cyanine-like structure with a planar dimethylamino group in water due to the stabilizing effect of hydrogen bonds between DMACA and water. The molecular absorption spectrum showed a significant change, increasing solvent polarity with a large shift of the lower energy band, while the other two low lying bands did not shift significantly. The study accurately described the solvatochromic shift of the lowest-energy band and analyzed the structure of the excited states in terms of the one-electron transition density matrix, which showed that the dominant excited state (associated with the first lower energy band) is characterized by a local excitation on the benzene ring with charge transfer character to the carbon conjugated segment. [ABSTRACT FROM AUTHOR]

The computational predictions of transition-metal tri-chalcogenide (TMTCs) were performed using ab initio density functional theory (DFT) to investigate the electronic band structure, the partial density of states (PDOS), optical absorptions, dielectric functions, complex conductivity, reflectivity, refractive index, electron loss, the Poisson's ratio, Young's modulus, bulk-to-shear ratio, and phonon dispersion. The bandgap is measured from the valence band maximum (VBM) to the conduction band minimum (CBM) with the G–Z transitions. This suggests that the material is an indirect bandgap semiconductor. The electronic bandgap ( E g) is significantly improved with nonlocal hybrid functionals, especially in HSE0s, with E g of 1.0 eV, which is in excellent agreement with the experimental data. However, our data shows that the HF-LDA exchange correlations significantly overestimate the E g with 7.33 eV. Also, our optical absorption data indicates a high absorption coefficient of about 2. 9 × 1 0 5 cm − 1 . The absorption peak of 7.4 eV indicates TiS3 can be applied in vacuum ultra-violet (VUV) applications. The reflectivity is also shown to be high, with over 90% of light being reflected. The mechanical stability of the monoclinic system can be testified by our elastic coefficients and the phonon dispersions. [ABSTRACT FROM AUTHOR]

The aim of this work was to create new ligand complexes and evaluate their effectiveness against certain strains of bacteria. A Brucker Tensor 27co FTIR spectrophotometer was used to record the infrared spectra. Elemental analysis (C, H, N) was carried out on an AA670 atomic absorption spectrophotometer to determine mineral content, and the conductivity of PCM3 Jenway was measured to record electronic spectra. The ligand was prepared, that possessed physical constants and spectroscopic properties. The complexes [M(L)2Cl2] and [M(L)4Cl2] were also prepared, where M=Mn(II), Co(II), Ni(II), Cu(II), and Zn(II), which were synthesized by direct reaction of the above ligand with metal chlorides in (2:1) or (4:1) (Ligand : metal) molar ratio in the ethanol medium. The ligand compound 4-(2-(benzo-1,3-dioxol-5-yl)-4,5-diphenyl-2,5-dihydro1H-imidazol-1-yl)aniline (L) was obtained. The prepared complexes were shown by elemental analysis, spectroscopic studies (FTIR, UV/vis), 1H-NMR measurement, conductivity measurements, and electron spectrometry value, which indicate the presence of tetrahedral and octahedral geometry around the metal ions. The biological antibacterial activity of the compounds and complexes has been demonstrated against specific strains of G+ Staph. aureus and G− Bacillus. The bonding compound L coordinates the metal in a tetrahedral and octahedral N-M-N manner. The compound and its complexes had activity against specific strains of bacteria. The ligand (L1) and the complex (3) had a greater effect on different types of bacteria than the rest of the complexes, which had a lower efficiency rate. [ABSTRACT FROM AUTHOR]

A new arsenato-polyoxovanadate with the composition {[Ni(dien)2]3[V6As8O26]}2+·2 Cl– has been crystallized under solvothermal conditions as turquoise block-like crystals. The central structural feature is the [V6IVAs8IIIO26]4– cluster anion, which is composed of two trinuclear {V3O11} groups consisting of three edge-sharing VO5 polyhedra. Pairs of pyramidal AsO3 moieties share a common corner forming As2O5 units, which interconnect the {V3O11} groups. One of the [Ni(dien)2]2+ complexes adopts the s-fac (Ni1) and the second complex the mer configuration (Ni2). The Cl− anion is involved in strong hydrogen bonding interactions and links the [Ni(dien)2]2+ complexes to form twelve-membered rings which host the [V6As8O26]4– cluster anions. The Hirshfeld surface analysis yields a detailed picture of the intermolecular interactions revealing clear differences for the two unique [Ni(dien)2]2+ complexes. Intermolecular contacts also include As⋯H, O⋯H and H⋯H interactions. In the electronic spectrum the bands of d–d transitions of the vanadyl group and of the Ni2+ cations overlap, preventing a detailed analysis. [ABSTRACT FROM AUTHOR]

The current research focused on the Schiff base ligand (S,E)-2-((2-hydroxy-3-methoxybenzylidene) amino)-3-(1H-imidazol-4-yl)propanoic acid which synthesis by reacting L-histidine and 2-hydroxy-3-methoxy-benzaldehyde. Its complexes with Ce(III) and Fe(III) both in bulk and nano size were also synthesized. The ligand and its metal complexes were characterized by various physicochemical methods such as FT-IR, 1H NMR, 13C NMR, electronic spectra, XRD, TGA, and SEM. The synthesized ligand and its metal complexes were screened against different fungi. It was found from the results that the cerium nano complex shows a potent antifungal activity for indoor uses as wallpapers. [ABSTRACT FROM AUTHOR]

Curcumin (Cur) metal complexes of Mg(II), Ca(II), Cu(II), Cr(III), and Se(IV) were prepared and characterized using elemental analysis, molar conductance, IR, UV-spectra, 1H NMR, SEM, TEM, and X-ray diffraction. The very low values of molar conductance confirm that Cl-ions are absent inside or outside the chelation sphere confirming their non-electrolytic nature, while for Cr(III) Cur is high compared to other curcumin complexes, confirming that Cl-ions are inside the complexation sphere. Based on IR and electronic spectra, the Cur C=O group in enol form chelated to Mg(II), Ca(II), Cu(II), Cr(III), and tetravalent metal (Se). The surface morphology of the curcumin chelates showed an increase in particle size and irregular grains shaped with an elongated morphology. Transmission electron microscopy revealed that the Cur chelates have spherical black spots like shape with a particle size of 72.21-88.75 nm, 34.89-57.33 nm, and 80.71-100 nm for Cu(II), Zn(II), and Se(IV) Cur respectively. X-ray powder diffraction patterns for Cu(II) Cur complexes showed particle size within 70-90 nm; the antioxidant activities of Cur and its metal complexes were assessed. Results showed that the Cur complexes with Cr, Mg, Ca, Cu, or Se showed potent antioxidant activities. Further studies could evaluate the potency of these complexes to elevate the antioxidant defense system and enhance body functions against degenerative diseases, such as aging, Alzheimer's disease, and viral diseases. [ABSTRACT FROM AUTHOR]

Inclusion of one of the natural enantiomers of linalool ((R)-(-)-linalool, simply LIN) into cucurbit[n]urils (CB[n]s) was investigated by means of DFTB + and DFT computations with Grimme's dispersion correction and geometric counterpoise treatment. Among different cucurbit[n = 5 ~ 9]urils, some diastereoisomers of CB[7] can form relatively stable inclusion complexes (LIN@CB[n]s) with LIN in water. Hydrogen bonds and dispersion interaction between CB[n] and LIN play an important role in formation of the inclusion complexes. Molecular electrostatic potential, non-covalent interaction, and natural bond analysis were carried out for interpretation of stability of the relatively stable LIN@CB[7]s. Theoretical computations showed that LIN@i-CB[7] was the most stable and it can offer increased solubility to linalool in water than the normal CB[7]. The calculated electronic spectra of linalool, i-CB[7], and LIN@i-CB[7] showed that inclusion of linalool into i-CB[7] can be useful in protection of linalool from photo-degradation. [ABSTRACT FROM AUTHOR]

Research into and applications of phthalocyanines (Pc) are mostly connected to their intriguing electronic properties. Here, messenger‐type UV–vis spectroscopy of two metal‐free ions from the phthalocyanine family, cationic H2Pc+ and H2PcD+, along with their hydrates is performed. They show that the electronic properties of both ions can be traced to those in the conjugate base, Pc2–, however, they are affected by state splitting due to the reduced symmetry; in the H2Pc+ radical cation, a new band appears due to excitations into the singly‐occupied molecular orbital. Quantum chemical spectra modeling reproduces all important features of the measured spectra and provides insight into the nature of electronic transitions. Hydration of the ions has only a mild effect on the electronic spectra, showing the stability of the electronic structure with respect to solvation effects. [ABSTRACT FROM AUTHOR]

In this work, the four azo dyes (A1–A4) were synthesized using 5‐amino‐3‐methyl‐1‐phenyl pyrazole with four different coupling components by the conventional, simple diazo‐coupling method. These synthesized azo molecules were confirmed by various spectroscopic methods viz, FT‐IR spectra, HR‐MS spectra, 1H NMR spectra, and 13C NMR spectra. The electronic absorption and fluorescence spectra of synthesized azo compounds were recorded at room temperature, with different solvents. The DFT calculations were performed using 6‐311++G (d, p) basis set to evaluate the global reactive parameters of the synthesized azo dyes. The anti‐microbial activities were studied; the compound A1 exhibited a good antibacterial and anti‐fungal activities. The study of in silico molecular docking of the azo compounds revealed that all the compounds found to possess were extraordinary binding affinity as compared to the standards. The anti‐tuberculosis study was carried against mycobacterium tuberculosis and the results have shown that, the compound A2 showed good sensitivity to the studied azo compounds. [ABSTRACT FROM AUTHOR]

Anthraquinone derivatives are well recognized for their anticancer activities and pharmacological properties. In the present study, comprehensive theoretical and experimental FT-IR, FT-Raman, and UV-visible spectroscopic studies on the 1-Chloroanthraquinone (CAQ) molecule were carried out. The optimized molecular structure and harmonic vibrational frequencies was calculated using Gaussian 09 program. The experimental and calculated vibrational wavenumbers were assigned, which correlated well with the previous literature. The UV-visible absorption spectrum of the CAQ molecule was computed in the liquid phase (ethanol), which exhibits n–π* electronic transition, and the results were compared with the observed UV-visible spectrum. From the frontier molecular orbital analysis, the calculated energy gap value (4.03 eV) indicates that the CAQ molecule has a stable structure and the value was comparable with the band gap energy value of the reported bioactive molecules. The electron back donation from the carbonyl group oxygen atom to the benzene ring was identified using Mulliken atomic charge distribution analysis. Molecular electrostatic potential surface analysis confirms the reactive sites of the molecule. The natural bond orbital analysis validates electron back donation from the carbonyl group oxygen atom to the benzene ring of the CAQ molecule. The molecular docking analysis results that the CAQ molecule acts as a good inhibitor of histone deacetylase 6 (HDAC6) protein. HDAC6 protein is associated with oral squamous cell carcinoma. Thus, the present study paves the way for designing novel drugs for the treatment of oral squamous cell carcinoma. [ABSTRACT FROM AUTHOR]

Our understanding of quantum materials is commonly based on precise determinations of their electronic spectrum by spectroscopic means, most notably angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy. Both require atomically clean and flat crystal surfaces, which are traditionally prepared by in situ mechanical cleaving in ultrahigh vacuum chambers. We present a new approach that addresses three main issues of the current state-of-the-art methods: (1) Cleaving is a highly stochastic and, thus, inefficient process; (2) fracture processes are governed by the bonds in a bulk crystal, and many materials and surfaces simply do not cleave; and (3) the location of the cleave is random, preventing data collection at specified regions of interest. Our new workflow is based on focused ion beam machining of micro-strain lenses, in which shape (rather than crystalline) anisotropy dictates the plane of cleavage, which can be placed at a specific target layer. As proof-of-principle, we show ARPES results from micro-cleaves of Sr2RuO4 along the ac plane and from two surface orientations of SrTiO3, a notoriously difficult to cleave cubic perovskite. [ABSTRACT FROM AUTHOR]

The present study investigates the utilisation of density functional theory (DFT) to examine unmodified and amino acid-functionalised C4B32 borospherenes as potential carriers for drug transport. The recent and significant finding of borospherenes, which are composed of a cluster of four carbon atoms fused into a B364- structure (referred to as C4B32), has provided a valuable opportunity to explore the potential capabilities of unmodified and alanine-modified C4B32 clusters as efficient vehicles for medicinal substances. The main objective of this study was to utilise Density Functional Theory (DFT) to examine the interaction between unmodified and alanine-linked borospherenes and the medicinal substance Lamivudine (LV). The investigation results revealed that the incorporation of amino acids had a pivotal role in facilitating the distribution of bio-drugs, leading to an improvement in the binding capacity of the C4B32 cluster with the drug. In this study, the dispersion-corrected density functional theory (DFT) approach proposed by Grimme examined long-range interactions. The calculations were performed utilising the B3LYP functional, implemented with the 6–31 + G(d) basis set in the GAMMES software. The electronic spectra of the drug@cluster complexes were analyzed using UV-Vis calculations, revealing a noticeable shift towards longer wavelengths, commonly called redshift. The results above highlight the significant potential of alanine-modified C4B32 borospherenes in drug delivery applications. [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]

Linear and nonlinear electronic spectra provide an important tool to probe the absorption and transfer of electronic energy. Here, we introduce a pure state Ehrenfest approach to obtain accurate linear and nonlinear spectra that is applicable to systems with large numbers of excited states and complex chemical environments. We achieve this by representing the initial conditions as sums of pure states and unfolding multi-time correlation functions into the Schrödinger picture. By doing this, we show that one can obtain significant improvements in accuracy over the previously used projected Ehrenfest approach and that these benefits are particularly pronounced in cases where the initial condition is a coherence between excited states. While such initial conditions do not arise when calculating linear electronic spectra, they play a vital role in capturing multidimensional spectroscopies. We demonstrate the performance of our method by showing that it is able to quantitatively capture the exact linear, 2D electronic spectroscopy, and pump–probe spectra for a Frenkel exciton model in slow bath regimes and is even able to reproduce the main spectral features in fast bath regimes. [ABSTRACT FROM AUTHOR]

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

The interplay of nuclear and electronic dynamics characterizes the multidimensional electronic spectra of various molecular and solid-state systems. Theoretically, the observable effect of such interplay can be accounted for by response functions. Here, we report analytical expressions for the response functions corresponding to a class of model systems. These are characterized by coupling between the diabatic electronic states and the vibrational degrees of freedom, resulting in linear displacements of the corresponding harmonic oscillators, and by nonadiabatic couplings between pairs of diabatic states. In order to derive the linear response functions, we first perform the Dyson expansion of the relevant propagators with respect to the nonadiabatic component of the Hamiltonian, then derive and expand with respect to the displacements the propagators at given interaction times, and finally provide analytical expressions for the time integrals that lead to the different contributions to the linear response function. The approach is then applied to the derivation of third-order response functions describing different physical processes: ground state bleaching, stimulated emission, excited state absorption, and double quantum coherence. Comparisons between the results obtained up to sixth order in the Dyson expansion and independent numerical calculation of the response functions provide evidence of the series convergence in a few representative cases. [ABSTRACT FROM AUTHOR]

The structural, electronic, and optical properties of nine different polymorphs of silica are investigated with both the traditional generalized gradient approximation (GGA) scheme and the hybrid functional. These include the 4:2-coordinated systems of quartz, tridymite, cristobalite, coesite, and keatite, as well as the 6:3-coordinated stishovite. The phases with similar crystal structures tend to share analogous electronic and optical features, while these properties are different in the case of stishovite. For the 4:2-coordinated polymorphs, linear relations are firmly established between the bandgap and the static dielectric constant vs the unit cell volume, respectively. Further investigation of their refractive indices also reveals a strong linearity with the corresponding densities. Our calculation with the sX functional reproduces the experimental bandgap values well, while GGA is superior for the overall trends of their optical properties. [ABSTRACT FROM AUTHOR]

Many quantum chemical methods used for large complexes are based on a limited treatment of electrons due to the computational demand dictated by the number of electrons that must be explicitly considered, especially when considering the chemical environment. Such treatments can fail to correlate accurately with electronic spectra. Ab initio electronic structure theory using the spin–orbit configuration interaction method is applied in a study of spectral transitions in PtCl42− including counter-ion environmental effects. In this method, electronic wave functions are eigenfunctions of the total angular momentum operator belonging to one of the symmetry types of the molecular double group. PtCl42− is investigated as a charged gas phase complex, a point-charge-neutralized complex, and a pseudopotential-neutralized complex. Results indicate that the use of a whole-atom relativistic effective core potential for the potassium cation provides a more accurate representation of the environment than a point charge and accurately represents electronic states without increasing the complexity of the calculation and, therefore, its computational demand. [ABSTRACT FROM AUTHOR]

Thin-film materials from μ m thickness down to single-atomic-layered 2D materials play a central role in many novel electronic and optical applications. Coherent, nonlinear optical (NLO) μ -spectroscopy offers insight into the local thickness, stacking order, symmetry, or electronic and vibrational properties. Thin films and 2D materials are usually supported on multi-layered substrates leading to (multi-)reflections, interference, or phase jumps at interfaces during μ -spectroscopy, which all can make the interpretation of experiments particularly challenging. The disentanglement of the influence parameters can be achieved via rigorous theoretical analysis. In this work, we compare two self-developed modeling approaches, a semi-analytical and a fully vectorial model, to experiments carried out in thin-film geometry for two archetypal NLO processes, second-harmonic and third-harmonic generation. In particular, we demonstrate that thin-film interference and phase matching do heavily influence the signal strength. Furthermore, we work out key differences between three and four photon processes, such as the role of the Gouy-phase shift and the focal position. Last, we can show that a relatively simple semi-analytical model, despite its limitations, is able to accurately describe experiments at a significantly lower computational cost as compared to a full vectorial modeling. This study lays the groundwork for performing quantitative NLO μ -spectroscopy on thin films and 2D materials, as it identifies and quantifies the impact of the corresponding sample and setup parameters on the NLO signal, in order to distinguish them from genuine material properties. [ABSTRACT FROM AUTHOR]

The need for photosensors and gas sensors arises from their pivotal roles in various technological applications, ensuring enhanced efficiency, safety, and functionality in diverse fields. In this paper, interlinked PbS/Sb2O5 thin film has been synthesized by a magnetron sputtering method. We control the temperature to form the nanocomposite by using their different nucleation temperature during the sulfonation process. A nanostructured PbS/Sb2O5 with cross-linked morphology was synthesized by using this fast and efficient method. This method has also been used to grow a uniform thin film of nanocomposite. The photo-sensing and gas-sensing properties related to the PbS/Sb2O5 compared with those of other nanomaterials have also been investigated. The experimental and theoretical calculations reveal that the PbS/Sb2O5 exhibits extraordinarily superior photo-sensing and gas-sensing properties in terms of providing a pathway for electron transport to the electrode. The attractive highly sensitive photo and gas sensing properties of PbS/Sb2O5 make them applicable for many different kinds of applications. The responsivity and detectivity of PbS/Sb2O5 are 0.28 S/mWcm−2 and 1.68 × 1011 Jones respectively. The sensor response towards NO2 gas was found to be 0.98 at 10 ppb with an limit of detection (LOD) of 0.083 ppb. The PbS/Sb2O5 exhibits high selectivity towards the NO2 gas. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) were used to analyze the geometries, electronic structure, and electronic absorption spectra of a light sensor fabricated by PbS/Sb2O5. The results are very analogous to the experimental results. Both photosensors and gas sensors are indispensable tools that contribute significantly to the evolution of technology and the improvement of various aspects of modern life. [ABSTRACT FROM AUTHOR]

In this work, we analyze the effectiveness of different sets of well-known necessary N-representability conditions that are imposed on the variational determination of two-electron reduced density matrices corresponding to the ground and excited states of N-electron Hamiltonians within doubly occupied configuration interaction subspaces. The two-electron reduced density matrix elements are determined so that they are suitably related to those of higher-order reduced density matrices and other associated matrices, up to a given order, constituting positive semidefinite matrices. These conditions up to two-, three-, and four-order have been sequentially imposed on the variational calculation of the expectation values of the dispersion operator corresponding to several Hamiltonian models, obtaining the electronic spectra. These results have been contrasted with those arising from the full configuration interaction method, illuminating the sufficiency/insufficiency of the variational N-representability conditions applied. [ABSTRACT FROM AUTHOR]

To assign cis and trans isomers of m-tolyl isocyanate (mTI) and p-phenylene diisocyanate (pPDI) in the electronic excitation transition, we measured the time-of-flight mass-selected resonant ionization spectra of jet-cooled phenyl isocyanate (PI), mTI, and pPDI in the region of the 275 nm first ππ* absorption system. In the excitation spectra of jet-cooled mTI and pPDI, cis- and trans-rotational isomers appeared as doublets. Isomers were assigned by analyzing the methyl-group internal rotation for mTI and by applying low-frequency bending vibrations to the mutual exclusion rule between the one- and two-photon spectra for pPDI. The electronic spectra of the three molecules observed in the jet were assigned to the transition to the first ππ* and third singlet excited states with the aid of time-dependent (TD)-B3LYP/aug-cc-pVDZ and TD-CAM-B3LYP/aug-cc-pVDZ calculations. The 0 − 0 band of PI was observed at 36 354 cm−1, those of the cis and trans isomers of mTI at 36 018 and 35 853 cm−1, respectively, and those of the cis and trans isomers of pPDI at 34 437 and 34 383 cm−1, respectively. All vibronic bands were diffuse, probably because of internal conversion to two singlet nπ* states. For mTI, based on changes in the barrier height of methyl-group internal rotation upon excitation, the Hammett-σm of PI was determined to be −0.12. [ABSTRACT FROM AUTHOR]

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

We introduce two different approaches to represent the second-quantized electronic Hamiltonian in a sum-of-products form. These procedures aim at mitigating the quartic scaling of the number of terms in the Hamiltonian with respect to the number of spin orbitals and thus enable applications to larger molecular systems. Here, we describe the application of these approaches within the multi-configuration time-dependent Hartree framework. This approach is applied to the calculation of eigenenergies of LiH and electronic ionization spectrum of H2O. [ABSTRACT FROM AUTHOR]

Molecular electronic spectra can be represented in the time domain as auto-correlation functions of the initial vibrational wavepacket. We present a derivation of the harmonic vibrational auto-correlation function that is valid for both real and imaginary harmonic frequencies. The derivation rests on Lie algebra techniques that map otherwise complicated exponential operator arithmetic to simpler matrix formulas. The expressions for the zero- and finite-temperature harmonic auto-correlation functions have been carefully structured both to be free of branch-cut discontinuities and to remain numerically stable with finite-precision arithmetic. Simple extensions correct the harmonic Franck–Condon approximation for the lowest-order anharmonic and Herzberg–Teller effects. Quantitative simulations are shown for several examples, including the electronic absorption spectra of F2, HOCl, CH2NH, and NO2. [ABSTRACT FROM AUTHOR]

We present a methodology for simulating multidimensional electronic spectra of molecular aggregates with coupling of electronic excitation to a structured environment using the stochastic non-Markovian quantum state diffusion (NMQSD) method in combination with perturbation theory for the response functions. A crucial aspect of our approach is that we propagate the NMQSD equation in a doubled system Hilbert space but with the same noise. We demonstrate that our approach shows fast convergence with respect to the number of stochastic trajectories, providing a promising technique for numerical calculation of two-dimensional electronic spectra of large molecular aggregates. [ABSTRACT FROM AUTHOR]

Quantum master equations (QMEs) provide a general framework for describing electronic dynamics within a complex molecular system. Off-diagonal QMEs (OD-QMEs) correspond to a family of QMEs that describe the electronic dynamics in the interaction picture based on treating the off-diagonal coupling terms between electronic states as a small perturbation within the framework of second-order perturbation theory. The fact that OD-QMEs are given in terms of the interaction picture makes it non-trivial to obtain Schrödinger picture electronic coherences from them. A key experimental quantity that relies on the ability to obtain accurate Schrödinger picture electronic coherences is the absorption spectrum. In this paper, we propose using a recently introduced procedure for extracting Schrödinger picture electronic coherences from interaction picture inputs to calculate electronic absorption spectra from the electronic dynamics generated by OD-QMEs. The accuracy of the absorption spectra obtained this way is studied in the context of a biexciton benchmark model, by comparing spectra calculated based on time-local and time-nonlocal OD-QMEs to spectra calculated based on a Redfield-type QME and the non-perturbative and quantum-mechanically exact hierarchical equations of motion method. [ABSTRACT FROM AUTHOR]

Zinc(II) Schiff base complexes with different substituents at 5, 5' positions have been synthesized to study the effect of the electronic environment of the metal towards the cycloaddition reaction between CO2 and epoxide. The complexes have been characterized by FT‐IR, XPS, NMR, electronic spectroscopy, LC–MS, and TGA. We have used density functional theory to study the electronic structure of the Zn(II) complexes and modelled the electronic spectra and the mechanism of catalysis. Results obtained from DFT and LC–MS indicate the dimeric structures for all the complexes except ZnL4. The monomeric ZnL4 has the strongest electron withdrawing group, i. e. −NO2 at 5, 5' positions along with two labile water molecules attached to the Zn center. The dimeric complexes exhibit good to moderate yield for cycloaddition reaction to styrene carbonate under solvent‐free conditions and a relatively low reaction temperature of 80 °C, with CO2 pressure of ~1 atm. The best yield has been achieved by ZnL4. Different rate‐determining steps are captured by the DFT studies for dimeric and monomeric complexes. Without taking any preventing measure of dimerization by attaching the bulky tBu groups, relatively lesser catalytic amounts of all the complexes have shown yields of cyclic carbonate between 53–74 %, depending on the nature of the substituent present. [ABSTRACT FROM AUTHOR]

Two-dimensional polymers (2DPs) are a class of 2D crystalline polymer materials with definite structures, which have outstanding physical–chemical and electronic properties. They cleverly link organic building units through strong covalent bonds and can construct functional 2DPs through reasonable design and selection of different monomer units to meet various application requirements. As promising energy materials, 2DPs have developed rapidly in recent years. This review first introduces the basic overview of 2DPs, such as their historical development, inherent 2D characteristics and diversified topological advantages, followed by the summary of the typical 2DP synthesis methods recently (including "top-down" and "bottom-up" methods). The latest research progress in assembly and processing of 2DPs and the energy-related applications in energy storage and conversion are also discussed. Finally, we summarize and prospect the current research status, existing challenges, and future research directions of 2DPs. [ABSTRACT FROM AUTHOR]

Valence tautomerism (VT) involves the stimulated reversible intramolecular electron transfer between a redox-active metal and ligand. Dinuclear cobalt complexes bridged by bis(dioxolene) ligands can undergo thermally-induced VT with access to {CoIII-cat-cat-CoIII}, {CoIII-cat-SQ-CoII} and {CoII-SQ-SQ-CoII} states (cat2− = catecholate, SQ˙− = semiquinonate, CoIII refers to low spin CoIII, CoII refers to high spin CoII). The resulting potential for two-step VT interconversions offers increased functionality over mononuclear examples. In this study, the bis(dioxolene) ligand 3,3′,4,4′-tetrahydroxy-5,5′-dimethoxy-benzaldazine (thMH4) was paired with Mentpa (tpa = tris(2-pyridylmethyl)amine, n = 0–3 corresponds to methylation at 6-position of the pyridine rings) to afford [{Co(Mentpa)}2(thM)](PF6)2 (1a, n = 0; 2a, n = 2; 3a, n = 3). Structural, magnetic susceptibility and spectroscopic data show that 1a and 3a remain in the temperature invariant {CoIII-cat-cat-CoIII} and {CoII-SQ-SQ-CoII} forms in the solid state, respectively. In contrast, 2a exhibits incomplete thermally-induced VT between these two tautomeric forms via the mixed {CoIII-cat-SQ-CoII} tautomer. In solution, room temperature electronic absorption spectra are consistent with the assignments from the solid-state, with VT observed only for 2a. From electrochemistry, the proximity of the two 1e−-processes for the thMn− ligand indicates weak electronic communication between the two dioxolene units, supporting the potential for a two-step VT interconversion in thMn− containing complexes. Comparison of the redox potentials of the Co and thMn− processes suggests that only 2a has these processes in sufficient proximity to afford the thermally-induced VT observed experimentally. Density functional theory calculations are consistent with the prerequisite energy ordering for a two-step transition for 2a, and temperature invariant {CoIII-cat-cat-CoIII} and {CoII-SQ-SQ-CoII} states for 1a and 3a, respectively. This work presents the third example, and the first formally conjugated example, of a bridging bis(dioxolene) ligand that can afford two-step VT in a Co complex, suggesting new possibilities towards applications based on multistep switching. [ABSTRACT FROM AUTHOR]

The magnetic structure of Fe5O6 is studied using a combination of the group-theoretical analysis and DFT + U calculations of the electronic spectrum. The calculations are performed for the magnetic k = (0, 0, 0) vector. The magnetic ground state corresponds to the orthogonal ordering of two magnetic subsystems: the magnetic moments of Fe2+/Fe3+ ions located at the octahedral sites (slabs of octahedra) are directed along the c axis and are antiferromagnetically ordered, whereas the magnetic moments of Fe2+ ions in trigonal prisms forming one-dimensional chains are directed along the b axis and are antiferromagnetically coupled along the c axis. The formation of a nonzero antiferromagnetic component of magnetic moments in the slabs of octahedra directed along the b axis is caused by the effect of magnetic chains on the three-dimensional magnetic structure. [ABSTRACT FROM AUTHOR]

This study involves the synthesis of novel methoxyphenylthio-substituted phthalocyanines and their starting phthalonitriles as well as the characterization and investigation of their physical and spectral properties. Herein, although phthalocyanines were categorized as alpha and beta-substituted, the numbers of external substituent methoxy groups selected to obtain soluble phthalocyanines were also different. After their molecular structure was characterized using elemental analysis, FT-IR, NMR, and MALDI-TOF-MS techniques, the exhaustive electronic spectra of novel phthalocyanines were studied. During extensive UV-Vis spectroscopy studies, proton transfer complexes in basic coordinating solvents and protonated species in solvents containing acids as impurities occurred incidentally in some phthalocyanines. Then, it was investigated whether this incidentally encountered situation was related to the number of methoxy groups as external substituents. Consequently, it was revealed that the acidity of H atoms in the center of phenylthio-substituted phthalocyanines could be altered by outer groups in the substituents, and the wavelengths of the Q bands of the novel Pcs changed under the influence of these outer groups. Computational TD-DFT study at the ωB97XD/6-311G(d,p) level confirmed the redshift observed in electronic spectra upon inserting two additional OCH3 at outer groups, originating from small decreases in the HOMO–LUMO energy gap. The NBO charge distribution justified the electron donation from sulfur atoms to the phthalocyanine ring. [ABSTRACT FROM AUTHOR]

Photo‐induced charge transfer (CT) states are pivotal in many technological and biological processes. A deeper knowledge of such states is mandatory for modeling the charge migration dynamics. Real‐time time‐dependent density functional theory (RT‐TD‐DFT) electronic dynamics simulations are employed to explicitly observe the electronic density time‐evolution upon photo‐excitation. Asymmetrically substituted indenotetracene molecules, given their potential application as n‐type semiconductors in organic photovoltaic materials, are here investigated. Effects of substituents with different electron‐donating characters are analyzed in terms of the overall electronic energy spacing and resulting ultrafast CT dynamics through linear response (LR‐)TD‐DFT and RT‐TD‐DFT based approaches. The combination of the computational techniques here employed provided direct access to the electronic density reorganization in time and to its spatial and rational representation in terms of molecular orbital occupation time evolution. Such results can be exploited to design peculiar directional charge dynamics, crucial when photoactive materials are used for light‐harvesting applications. [ABSTRACT FROM AUTHOR]

Altermagnets are an emerging elementary class of collinear magnets. Unlike ferromagnets, their distinct crystal symmetries inhibit magnetization while, unlike antiferromagnets, they promote strong spin polarization in the band structure. The corresponding unconventional mechanism of time-reversal symmetry breaking without magnetization in the electronic spectra has been regarded as a primary signature of altermagnetism but has not been experimentally visualized to date. We directly observe strong time-reversal symmetry breaking in the band structure of altermagnetic RuO2 by detecting magnetic circular dichroism in angle-resolved photoemission spectra. Our experimental results, supported by ab initio calculations, establish the microscopic electronic structure basis for a family of interesting phenomena and functionalities in fields ranging from topological matter to spintronics, which are based on the unconventional time-reversal symmetry breaking in altermagnets. [ABSTRACT FROM AUTHOR]

This study successfully and cost-effectively synthesized a novel compound, 3-[(5-amino-1-phenyl-1H-pyrazol-4-yl)carbonyl]-1-ethyl-4-hydroxyquinolin-2(1H)-one (APPQ, 4), which displayed significant potential for various applications and yielded promising outcomes. Theoretical electronic absorption spectra in different media were acquired using the Coulomb-attenuating approach (CAM-B3LYP) and the Corrected Linear Response Polarizable Continuum Model (CLR) PCM. Employing CAM-B3LYP with the 6-311 + + G(d,p) level of DFT proved to be more accurate than alternative quantum chemical calculation methods, aligning well with the experimental data. Additionally, the CAM-B3LYP method using polarized split-valence 6-311 + + G(d,p) basis sets and CLR PCM in various solvents exhibited good agreement with the observed spectra. The high stability of APPQ, validated by the computed total energy and thermodynamic parameters at the same calculation level, surpassed that of anticipated structure 3. The theoretically calculated chemical shift values (1H and 13C) and vibrational wavenumbers were strongly correlated with the experimental data. The APPQ thin films demonstrated a band gap energy of 2.3 eV through distinctive absorption edge measurement. Photoluminescence spectra exhibited characteristic emission peaks at approximately 580 nm. Current–voltage measurements on n-Si heterojunction devices with APPQ thin films revealed typical diode behavior. These APPQ-based devices showed attractive photovoltaic properties, including an open-circuit voltage of 0.62 V, a short-circuit current of 5.1 × 10–4 A/cm2, and a maximum output power of 0.247 mW/cm2. Overall, the investigated heterojunctions display appealing photophysical characteristics, encouraging advancements in photovoltaics. [ABSTRACT FROM AUTHOR]

This study delves into the exploration of B′ site arranged Cs 2 NaB′Cl 5 perovskites (B′ = Ni, Mn, Fe) as prospective alternatives to lead-based perovskites, given the environmental concerns associated with lead toxicity and material instability. Structural analysis using X-ray diffraction revealed a stable tetragonal crystal structure with the P4/mmm space group. Electronic properties, assessed via density functional theory (DFT) calculations, identified these materials as p-type semiconductors with tunable band gaps, and this finding supported by optical experimental data. Thermogravimetric analysis (TGA) demonstrated decomposition temperatures up to 750 °C, with Cs 2 NaMnCl 5 exhibiting superior thermal stability. Field emission scanning electron microscopy (FESEM) unveiled distinct morphologies influenced by the transition metal in the B′ site, while elemental analysis confirmed material purity. The optical analysis revealed strong light absorption in the visible spectrum, highlighting the potential of these materials for sustainable energy conversion applications. Overall, this research contributes valuable insights into the environmental-friendly potential of B′ site arranged Cs 2 NaB′Cl 5 perovskites in photoelectrochemical and solar cell application. [Display omitted] • Theoretical and experimental studies were carried out for Cs 2 Na B′ Cl 5. • Band structure was stimulated using DFT. • Cs 2 Na B′ Cl 5 (B′ = Ni, Mn, Fe) was synthesized using a simple solution method. • Band gaps of the Cs 2 Na B′ Cl 5 (B′ = Ni, Mn, Fe) were found to be 1.6–2 eV. • Dielectric constants, extinction coefficient, and refractive index are conferred. [ABSTRACT FROM AUTHOR]

Two new pentagon‐embedded carbo[11]helicenes have been designed and synthesized in a three‐step process, which are the first example of carbo[11]helicenes through the post‐functionalization of twistacene. TD‐DFT analyses indicate that both of them possess high enantiomerization barriers of 42.29 kcal/mol and 40.76 kcal/mol, respectively. They emit strong red fluorescence and can be chemically oxidized into stable cationic radicals upon addition of AgSbF6 evidenced by the bathochromic‐shifted absorption spectra and the appearance of electronic paramagnetic resonance (EPR) signals. In addition, such helical derivatives can be chosen as radiative cooling materials in a glass model house, and the maxima of 5.4 °C for the former and 6.5 °C for the latter are found in the comparative tests, which might be caused by the NIR reflective response. [ABSTRACT FROM AUTHOR]