Electronic Absorption Spectra Research Articles

Investigation of the Dyeing Ability of Some Reactive Triazine Azo Dyes Containing Pyrazole Fragment.

The IR, 1H NMR, and DFT studies indicated that the prepared reactive disperse dyes predominately exist as hydrazone tautomers. The electronic absorption spectra in methanol were observed and compared to those computed using B3LYP/6-311G(d,p). The dyeing efficiency of the produced dispersed reactive dyes was examined on polyester, cotton, and polyester/cotton blended fabrics. The degree of exhaustion and the quick properties of the dyed samples in terms of perspiration, washing, scorch and light fastness were assessed. It was found that reactive disperse dyes under investigation have a higher affinity for dyeing polyester textiles than cotton textiles. Moreover, the reflectance and color strength of the synthesized dyes were measured and discussed.

New nanometric metal complexes based on thiazole derivative as potential antitumor and antimicrobial agents: Full structural elucidation, docking simulation and biological activity studies

Novel Mn(II), Ni(II), Zr(IV) and Cd(II) nanosized complexes of thiazole Schiff base derivative (HL) were synthesized for further medicinal applications. The inspected complexes were fully characterized using elemental and thermal analyses in addition to infrared spectroscopy (IR) and nuclear magnetic resonance (1HNMR). Electronic absorption spectra, X-ray powder diffraction (XRD), transmittance electron microscopy (TEM), molar conductance and magnetic moment were also measured and explained. The brought about data revealed that the ligand–metal chelation happened through the N atom of N = N group, and the ortho-dehydrogenated phenolic O atom to form the chelates where the metal binds with one molecule of the parent ligand. All applied spectroscopic and analytical techniques confirmed tetrahedral geometry in Mn(II) and Ni(II) complexes and octahedral geometry for Cd(II) and Zr(IV) complexes. The ligand, Mn(II), Ni(II), and Zr(IV) chelates' XRD patterns indicated an amorphous character where the Cd(II) complex's nature is crystalline. Transmission electron microscopy (TEM) images of the prepared compounds showed that the surface morphology is uniform and homogeneous. Also, the metal ions distribute through the complexes' surface in a nanosized nature. The metal complexes have been simulated by docking in the co-crystal structures of the liver cancer and breast cancer proteins with PDB IDs, 2JW2 and 3S7S, successively. Antibacterial, antifungal and anticancer activities for the ligand that has been produced and its complexes were achieved. The most encouraging antitumor results were acquired by Ni(II) chelate which exhibited an IC50 of 23.52 µg/ml contra MCF-7 cells (human breast cancer) which is lower than the reference 5-Fluorouracil (5-FU, IC50 = 28.00 µg/ml).

Investigation of the structural and optoelectronic characteristics in coumarin-based dye-sensitized solar cells, both in isolation and with TiO2 adsorption

In this study, six novel organic dyes derived from coumarin have been formulated by limiting the rotation of bithiophene through the introduction of substituents, namely NCH3, Si(CH3)2, C(CH3)2, C=C(CH3)2, and C=O. Their structural, electronic, photovoltaic, and spectral properties were investigated using density functional theory at the B3LYP/6-31G(d,p) level. Furthermore, the time-dependent DFT (TD-DFT) at TD-BHandH/6-31G(d,p) level method was chosen to calculate the electronic absorption spectra and charge transfer characteristics of the investigated dyes in the chloroform solvent, as well as molecular properties such as geometries parameters, optoelectronic properties, and frontier molecular orbitals. With our studies, we reveal that all the studied dyes show significance in the range of 340.97–610.89 nm, with a band gap in the range of 1.90–2.26 eV, as well as high light capture efficiency (LHE) and significant intramolecular charge transfer (ICT) properties. In addition, we were interested in the energetic, electronic, and absorption studies of dyes linked to the TiO2 semiconductor (Dye@TiO2). All designed dyes exhibit better geometric and optoelectronic properties except for D3, which has the lowest gap energy and extends towards the red. The results reveal that these compounds would be used as potential sensitizers for DSSC applications.

High-performance optoelectronic and thermoelectric properties of transparent conductors based on Tl2O3 under pressure

In this work, the full-potential linearized augmented plane wave method (FP- LAPW) and the modified Becke-Johnson (mBJ) functional with spin–orbit (SO) coupling are used the obtain the structural, optoelectronic and thermoelectric properties of Tl2O3 under pressure. The results show that Tl2O3, as transparent conducting oxide (TCO), is a direct bandgap semiconductor with a band gap of 1.23 eV. The band gap value and the effective mass of electrons increases by increasing pressure. Density of state spectra reveal that the nature of electrons in Tl-6s state in the bottom of conduction band, like free electrons in s state, is responsible for the conducting behavior of Tl2O3. A blue shift is observed in optical spectra such as electron energy loss and absorption spectra with an increase in pressure. Obtained dielectric constants under pressure are inversely proportional to the band gap value according to Penn model. The effects of pressure on thermometric properties are also explored. The hydrostatic pressure increases Seebeck coefficient, while it decreases thermal conductivity that is an effective way to the enhancement of the thermoelectric efficiency of TCOs. A figure of merit (ZT) of 0.98 in p-type Tl2O3 is achieved that is desirable for using in thermoelectric devices.

Comparison study (experimental and theoretical), hydrogen bond interaction through water, donor acceptor investigation and molecular docking study of 3,3-((1,2-phenylenebis (azaneylylidene)) bis (methaneylylidene)) diphenol

The novel Schiff’s base (CS6) was synthesized and confirmed by various studies. The B3LYP/cc-pVDZ basis set was used for theoretical study and the results indicated that both the theoretical and experimental studies correlated well. The interaction energy of CS6-water complex calculated by using the local energy decomposition analysis was found to be −7.28 kcal/mol. The TD-TFT method was used for the calculation of electronic absorption spectrum. This study confirmed that the observed wavelength and the simulated wavelength in the electronic spectra were almost similar. The electrophilic and nucleophilic attacking sites of the titled compound were identified by using FMO and MEP studies. The highest stabilization energy (30.19 kcal/mol) formed by LP (2) O24 to anti-bonding σ*(C18-C19) was confirmed by the NBO study. The localized and delocalized electrons were confirmed by ELF and LOL studies. The hydrogen bond interaction as well as the physical and chemical properties of CS6 indicated that it showed a moderate similarity to the drugs. The docking study confirmed that the dehydro-L-gulonate decarboxylase inhibitor (1Q6O) could interact with CS6 compound with the binding energy of −5.26 kcal/mol. Communicated by Ramaswamy H. Sarma

Exploring the weak visible-near-infrared and NO2 detection capabilities of PbS/Sb2O5 heterostructures with DFT interpretations

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.

Absorption spectra of p-nitroaniline derivatives: charge transfer effects and the role of substituents.

Push-pull compounds are model systems and have numerous applications. By changing their substituents, properties are modified and new molecules for different applications can be designed. The work investigates the gas-phase electronic absorption spectra of 15 derivatives of push-pull para-nitroaniline (pNA). This molecule has applications in pharmaceuticals, azo dyes, corrosion inhibitors, and optoelectronics. Both electron-donor and electron-withdrawing groups were investigated. Employing machine learning-derived Hammett's constants σm, σm0, σR, and σI, correlations between substituents and electronic properties were obtained. Overall, the σm0 constants presented the best correlation with HOMO and LUMO energies, whereas the σR constants best agreed with the transition energy of the first band and HOMO-LUMO energy gap. Electron-donors, which have lower σR values, redshift the absorption spectrum and reduce the HOMO-LUMO energy gap. Conversely, electron-withdrawing groups (higher σR's) blueshift the spectrum and increase the energy gap. The second band maximum energies, studied here for the first time, showed no correlation with σ but tended to increase with σ. A comprehensive charge transfer (CT) analysis of the main transition of all systems was also carried out. We found that donors (lower σ's) slightly enhance the CT character of the unsubstituted pNA, whereas acceptors (higher σ's) decrease it, leading to increased local excitations within the aromatic ring. The overall CT variation is not large, except for pNA-SO2H, which considerably decreases the total CT value. We found that the strong electron donors pNA-OH, pNA-OCH3, and pNA-NH2, which have the smallest HOMO-LUMO energy gaps and lowest σ's, have potential for optoelectronic applications. The results show that none of the studied molecules is fluorescent in the gas phase. However, pNA-NH2 and pNA-COOH in cyclohexane and water reveal fluorescence upon solvation. We investigated theoretically employing the second-order algebraic diagrammatic construction (ADC(2)) ab initio wave function and time-dependent density functional theory (TDDFT) the gas-phase electronic absorption spectra of 15 derivatives of p-nitroaniline (pNA). The investigated substituents include both electron-donor (C6H5, CCH, CH3, NH2, OCH3, and OH,) and electron-withdrawing (Br, CCl3, CF3, Cl, CN, COOH, F, NO2, and SO2H) substituents.

Synthesis of new [6]helicene derivatives for OLED applications. Experimental photophysical and chiroptical properties and theoretical investigation

Six-membered helicenes with specific functionalities were synthesized in good overall yields (40%–73%) through a concise photochemical method, allowing for their comprehensive characterization. The racemic mixtures were effectively resolved into their P- and M-enantiomers with high optical purity (97.56%–100% ee) by using chiral HPLC. This separation showcased remarkable optical activity, revealing substantial optical rotations (e.g., +2500–3000 for the (P)-enantiomer at λ = 589 nm) and notable electronic circular dichroism (ECD) signals. The organic helical species showed a strong absorption in the UV region and exhibited a red shifted emission, resulting in a quantum yield of 0.12–0.21. Moreover, they demonstrated irreversible one-electron oxidation and reduction processes, and their HOMO and LUMO energy levels were estimated via electrochemical methods. Utilizing DFT and TD–DFT computational approaches, we accurately predicted the electronic absorption and ECD spectra, as well as the frontier molecular orbitals (FMOs), aligning closely with experimental observations. Furthermore, in-depth analyses of absorption and ECD spectra, molecular electrostatic potential (MEP), and reduced density gradient (RDG) through quantum chemical calculations offered insights into the fundamental characteristics of these materials. The collective properties strongly indicate the potential application of these helicenes in electroluminescent and OLED devices, underscoring their promise as candidates in optoelectronic applications.

Enhanced reactivity and selective adsorption: Unveiling the potential of metal-decorated graphene membranes for biosensing

This study investigates the structural, stability, electronic, and optical properties of finite graphene membranes through a comprehensive computational analysis. The 2D membranes are constructed from hexagonal graphene quantum dots and are decorated with Co, Mn, and Ni. Stability assessments, based on binding energies, affirm the stable formation of the 2D membrane and its derivatives. Electronic investigations reveal a reduction in the energy gap upon metal decoration, indicating enhanced reactivity. Membrane studies demonstrate effective adsorption of creatinine and uric acid on both edge and surface sites, supported by negative adsorption energies. Electronic transitions and absorption spectra shifts indicate dynamic interactions, emphasizing the materials' potential for selective molecular separation. Non-covalent interaction analysis confirmed the role of van der Waals interactions in creatinine and uric acid adsorption. Overall, the findings suggest that the graphene membrane and its decorated derivatives hold promise for selective adsorption applications, especially in the context of biosensing.

Incorporation of the 99TcO4- Anion within the Ag24(C≡CtBu)204+ Cluster Unveiling the Unique Shell-to-Core Charge Transfer.

We present the first example of an 99TcO4- anion entrapped within the cavity of a silver cluster, revealing an unprecedented photoinduced charge transfer phenomenon. [Ag24(C≡CtBu)20(99TcO4)]·(BF4)3 (denoted as 99TcO4-@Ag24) was successfully synthesized and structurally characterized. Single-crystal X-ray diffraction and Raman spectroscopy reveal that the tetrahedral structure of the 99TcO4- anion sustains significant symmetry breaking with weakened Tc-O bond strength under confinement within the Ag24(C≡CtBu)204+ cluster. Notably, 99TcO4-@Ag24 exhibits a broadband electronic absorption spectrum in the visible region, which was absent for the other 99TcO4--containing compounds. Density functional theory calculations elucidate that host-guest electrostatic interactions result in an electron polarization effect between the 99TcO4- anion core and the Ag24 cationic shell. The emergence of an absorption band in 99TcO4-@Ag24 is rationalized by intermolecular charge transfer from the Ag24 electronic states to the lowest unoccupied molecular orbitals of 99TcO4- instead of the intramolecular electron transition observed in other 99TcO4--containing compounds.

First-Principles Investigations of Novel Guanidine-Based Dyes.

In the pursuit of finding efficient D-π-A organic dyes as photosensitizers for dye-sensitized solar cells (DSSCs), first-principles calculations of guanidine-based dyes [A1-A18] were executed using density functional theory (DFT). The various electronic and optical properties of guanidine-based organic dyes with different D-π-A structural modifications were investigated. The structural modification of guanidine-based dyes largely affects the properties of molecules, such as excitation energies, the oscillator strength dipole moment, the transition dipole moment, and light-harvesting efficiencies. The energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) is responsible for the reduction and injection of electrons. Modification of the guanidine subunit by different structural modifications gave a range of HOMO-LUMO energy gaps. Chemical and optical characteristics of the dyes indicated prominent charge transfer and light-harvesting efficiencies. The wide electronic absorption spectra of these guanidine-based dyes computed by TD-DFT-B3LYP with 6-31G, 6-311G, and cc-PVDZ basis sets have been observed in the visible region of spectra due to the presence of chromophore groups of dye molecules. Better anchorage of dyes to the surface of TiO2 semiconductors helps in charge-transfer phenomena, and the results suggested that -COOH, -CN, and -NO2 proved to be proficient anchoring groups, making dyes very encouraging candidates for DSSCs. Molecular electrostatic potential explained the electrostatic potential of organic dyes, and IR spectrum and conformational analyses ensured the suitability of organic dyes for the fabrication of DSSCs.

Synthesis, Solvatochromic Studies, DFT Calculations, Characterization, and In Silico Molecular Docking Studies of Azo Dyes of 3‐Methyl‐1‐phenyl‐1H‐pyrazol‐5‐amine

AbstractIn 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.

Reactivity and zinc affinity of dipyrromethenes as colorimetric sensors: structural and solvation effects

A wide range of dipyrromethenes (17 objects) with different nature, number, and attachment positions of alkyl, aryl, and meso-aza substituents was synthesized, and the effect of molecular structure features on their spectral properties was analyzed. It is shown that, chromophores absorb in a wide spectral range from ∼ 420 to ∼ 600 nm due to the structural modification of the dipyrromethene ligand backbone. Partially alkylated dipyrromethenes containing 4–5 methyl substituents absorb in the region from 421 to 436 nm. For fully alkylated dipyrromethenes, the band maximum position shifts to the region from 437 to 446 nm for ligands with 4,4′-substituents in the sequence: methyl, ethyl, propyl, butyl, amyl, hexyl, heptyl. The most significant spectral responses in the form of a red shift of 100 nm (in DMF) are observed when four methyl substituents in the 3,3′,5,5′-positions are replaced by phenyl groups. The replacement of the methine meso-spacer by a nitrogen atom leads to an additional red shift by another 70 nm. Particular attention is paid to the comparative analysis of the effect of structural factors on the coloristic and spectral responses of the complexation of dipyrromethene ligands with zinc(II) acetate and the stability of the resulting complexes [ZnL2], for which the lgKo values are varied from 6.4 to 10.9. The auxochromic action of Zn2+ cations shifts the band maxima of electronic absorption spectra to the long wavelength region by 20–76 nm relative to the spectra of the ligands. The highest complexation constant lgKo is 10.9 was obtained for the reaction of Zn(AcO)2 with hexamethylsubstituted dipyrromethene. Ligands with partially methylated pyrrole nuclei and extended alkyl and benzyl substituents form less stable complexes. The greatest effect of lowering the [ZnL2] stability is produced by the introduction of an electron-withdrawing aryl substituent into the meso-spacer of the dipyrromethene ligand (lgKo is 6.4).

DFT study of the spectroscopic behaviour of different iron(II)-terpyridine derivatives with application in DSSCs

Through a comprehensive computational analysis utilizing Density Functional Theory (DFT), we clarify the electronic structure and spectroscopic properties of modified iron(II)-terpyridine derivatives, with the aim of enhancing the efficiency of Dye-Sensitized Solar Cells (DSSCs). We optimized a series of nineteen iron(II)-terpyridine derivatives and related compounds in acetonitrile (MeCN) as the solvent using TDDFT, evaluating their potential as dyes for DSSCs. From the conducted computations on the optimized geometries of the nineteen [Fe(Ln)2]2+ complexes, containing substituted terpyridine and related ligands L1-L19, we determined the wavelengths (λ in nm), transition energy (E in eV), oscillator strength (f), type of transitions, excited state lifetime (τ), light harvesting efficiency (LHE), frontier orbital character and their energies (ELUMO/EHOMO), natural transition orbitals (NTOs), injection driving force of a dye (ΔGinject), and regeneration driving force of a dye (ΔGregenerate). Results show that the theoretically calculated values for assessing dye efficiency in a DSSC correlate with available experimental values. The UV–visible spectra of [Fe(Ln)2]2+ exhibited a peak above 500 nm (λmax) in the visible region, attributed to the ligand-to-metal charge transfer band (LMCT) in literature, and a significant absorbance peak at approximately 300 nm (λA,max) in the UV region. The M06-D3/CEP-121G method replicated all reported λmax and λA,max values with a mean absolute deviation (MAD) of 21 and 18 nm, respectively. Our findings underscore the connections between electronic modifications and absorption spectra, emphasizing their impact on the light-harvesting capabilities and overall performance of DSSCs. This research contributes to the advancement of fundamental principles governing the design and optimization of novel photovoltaic materials, facilitating the development of more efficient and sustainable solar energy technologies.

Growth, DFT, spectroscopic analysis, third-order NLO properties and optical limiting behavior of Bis(p-aminobenzoic acid-N) dichloro cadmium (II) (BPANDC) crystal

A new organic nonlinear optical crystal, Bis(p-aminobenzoic acid-N) dichloro cadmium (II) (BPANDC) has been grown by Slow Evaporation Solution Technique (SEST). The experiments were carried out to study the structural, optical, DFT and nonlinear optical properties of the grown crystals. The BPANDC crystal belongs to triclinic system with space group Pī with lattice parameters a = 6.359(4)Å, b = 7.509(11)Å, c = 17.263(7)Å, α= 94.50(2)˚, β=104.56(2)˚, γ=96.79(4)˚, and volume V = 787.20Å3. Using the TD-DFT method, the electronic absorption spectra of BPANDC was calculated in gas phase. The calculated FT-IR, FT-Raman spectrum, Molecular geometrical analysis, TD-DFT, HOMO–LUMO energy gap and Molecular electrostatic potential surface of BPANDC were calculated by DFT/ LANL2DZ basis set. The Z-scan analysis evidenced that the BPANDC exhibits sequential two-photon absorption induced reverse saturable absorption.

A new class of hexadentate thioether-containing ligands and their complexes with nickel(II)

A new series of hexadentate thioether-containing ligands was designed. Five nickel(II) dicationic pseudo-octahedral complexes synthesised with them revealed different degrees of deviation from ideal geometry. The electronic absorption spectra confirm the formation of high-spin octahedral [NiN4S2]2+chromophores with a large covalency typical for Ni(II) thioether complexes. DFT calculations help assign the chelating agent transitions, and support the Ni(II) high-spin ground state assignments, while suggesting that the SOMOs have mainly ligand character. The electrochemical behaviour of the complexes is consistent with irreversible n = 1 redox processes around −1.0 V, formally assignable to the Ni(II)/Ni(I) couple. Ligand reduction and large current augmentation due to catalytic H2production are also observed in this region.

Ionic strength and phase systems influence nanotubular material functionality

We synthesized novel thiacyanine chromonic liquid crystals (CLCs) and structurally characterized using NMR and mass spectrometry. The impact of distinct substitution at the para position of aromatic counter anions, aliphatic counter ion chain length, and varied spacer parity of thiacyanine dyes on CLC formation is investigated. Liquid crystal properties of the synthesized dyes are characterized by polarizing optical microscopy (POM) and X-ray diffraction (XRD) studies. Dyes exhibit nematic (N), lamellar (Lα), columnar rectangular (Colr), and columnar oblique (Colob) CLCs at different concentrations in the water. Electronic absorption spectra reveal Scheibe aggregation in all the dyes. Cylicvoltametry studies confirm redox behaviour in TC-1a and TC-5e dyes. Chromonic LCs hybrid nano-materials are synthesized using sol–gel method. Scanning electron microscopy employed to confirm nano tubular fiber structure of the hybrid nanomaterilals..

Solvation model, Vibrational analysis, Electronic level, Non-Covalent interactions and Molecular docking investigations of 6-Chloro-2-(4-Aminophenyl)-1H-Benzimidazole

6-Chloro-2-(4-Aminophenyl)-1H-Benzimidazole compound were synthesized and characterized by SC-XRD, FT-IR, FT-Raman, UV–Vis, 1H NMR, and 13C NMR and analyzed with experimental data. The DFT approach with the B3LYP functional and 6-311++G(d,p) basis set was used to calculate the geometry parameters and wavenumbers of the title compound. Electronic absorption spectra and 1H–13C NMR studies have been computed in gas and solvents (dimethylsulfoxide, chloroform, and H2O) by using the TD-DFT and the IEFPCM solvation model. The HOMO-LUMO energy band gap has also been determined. To identify the electron localization density and weak interactions, the Multiwin-3.8 was subjected to a topological analysis and non-covalent interactions, including ELF, LOL, DORI and ED.Studies of donor–acceptor connections were performed using NBO analysis. To calculate contributions to the molecular orbitals, TDOS was determined. Molecular electrostatic potential (MEP) reveals the chemical reactivity sites for the reaction. The antibacterial activity of the compound has been assessed with a zone of inhibition by the well diffusion method using a panel of selected gram-positive Staphylococcus aureus (MTCC-3160), Enterococcus faecalis (MTCC-3159) and gram-negative Pseudomonas aeruginosa (MTCC-4030), Escherichia coli (MTCC-1667) bacterial strains that have shown better activity than the standard drug (Ciprofloxacin). Finally, molecular docking and pharmacokinetics have been agreed upon to understand the binding energy of the ligand–protein interaction.

Artificial-Intelligence-Enhanced On-the-Fly Simulation of Nonlinear Time-Resolved Spectra.

Time-resolved spectroscopy is an important tool for unraveling the minute details of structural changes in molecules of biological and technological significance. The nonlinear femtosecond signals detected for such systems must be interpreted, but it is a challenging task for which theoretical simulations are often indispensable. Accurate simulations of transient absorption or two-dimensional electronic spectra are, however, computationally very expensive, prohibiting the wider adoption of existing first-principles methods. Here, we report an artificial-intelligence-enhanced protocol to drastically reduce the computational cost of simulating nonlinear time-resolved electronic spectra, which makes such simulations affordable for polyatomic molecules of increasing size. The protocol is based on the doorway-window approach for the on-the-fly surface-hopping simulations. We show its applicability for the prototypical molecule of pyrazine for which it produces spectra with high precision with respect to ab initio reference while cutting the computational cost by at least 95% compared to pure first-principles simulations.

Synthesis and Characterization of Isostructural Th(IV) and U(IV) Pyridine Dipyrrolide Complexes.

A series of pyridine dipyrrolide actinide(IV) complexes, (MesPDPPh)AnCl2(THF) and An(MesPDPPh)2 (An = U, Th, where (MesPDPPh) is the doubly deprotonated form of 2,6-bis(5-(2,4,6-trimethylphenyl)-3-phenyl-1H-pyrrol-2-yl)pyridine), have been prepared. Characterization of all four complexes has been performed through a combination of solid- and solution-state methods, including elemental analysis, single crystal X-ray diffraction, and electronic absorption and nuclear magnetic resonance spectroscopies. Collectively, these data confirm the formation of the mono- and bis-ligated species. Time-dependent density functional theory has been performed on all four An(IV) complexes, providing insight into the nature of electronic transitions that are observed in the electronic absorption spectra of these compounds. Room temperature, solution-state luminescence of the actinide complexes is presented. Both Th(IV) derivatives exhibit strong photoluminescence; in contrast, the U(IV) species are nonemissive.