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Comparison and convergence of optical absorption spectra of noble metal nanoparticles computed using linear-response and real-time time-dependent density functional theories
摘要： The real-time time-dependent density functional theory (RT-TDDFT) is rapidly gaining prominence as an alternative approach to capture optical properties of molecular systems, which warrants the necessity to benchmark the traditional linear response (LR) method and the RT approach. We calculate the absorption spectra of noble metal nanoparticles with a variety of sizes and shapes to demonstrate the consistency of the two methods over a broad range of energy. The RT spectrum obtained using a grid-based basis set with pseudopotentials achieves results in good agreement with the LR spectrum obtained with large QZ4P atom-centered basis sets. Factors that lead to convergence of the spectra are considered. In addition, the real-time variation of the electron density is visualized to show the collective oscillation of electron density for the plasmon modes of noble metal nanoparticles. The RT approach is most useful when calculating wide absorption spectra of larger gold or silver nanoparticles.
关键词： optical absorption spectra,noble metal nanoparticles,RT-TDDFT,LR-TDDFT,plasmon modes
更新于2025-09-10 09:29:36
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Green-Light-Induced PhotoCORM: Lysozyme Binding Affinity towards Mn <sup>I</sup> and Re <sup>I</sup> Carbonyl Complexes and Biological Activity Evaluation
摘要： Reaction of N-(2-pyridylmethylene)benzene-1,4-diamine (L) with [MBr(CO)5] (M = MnI and ReI) affords complexes of the type [MBr(CO)3L] [M = MnI (1) and ReI (2)]. Complex 1 releases CO upon illumination with light in the range of 525–468 nm. No photo induced CO release is detected from 2. Reactive azide complex 3, obtained by bromide's ligand exchange, reacts with the electron-poor alkyne dimethyl acetylene dicarboxylate giving triazolato complex 4 ([Mn(triazolateCOOMe,COOMe)(CO)3L]) via the free catalyst [3+2] cycloaddition coupling. Complex 1 exhibits interesting antifungal activity (MIC = 30 nM) against Candida albicans and Cryptococcus neoformans as well as cytotoxic activity of 12.56 μg/mL against noncancerous human embryonic kidney cells. Reactivity of the complexes towards hen egg white lysozyme is studied by electrospray ionization mass spectrometry.
关键词： Carbon monoxide,Biological,Photoactivatable,TDDFT,Lysozyme,binding affinity
更新于2025-09-10 09:29:36
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Effects of Rare-Gas Matrices on the Optical Response of Silver Nanoclusters
摘要： The optical response of silver clusters, Agn with n = 8, 20, 35, 58, 92, embedded in a rare-gas matrix are calculated in the framework of the Time-Dependent Density Functional Theory (TDDFT). We present a methodology able to reproduce with unprecedented accuracy the experimental spectra measured on metal clusters embedded in neon, argon, krypton and xenon solid matrices. In our approach, the metal cluster is surrounded by explicit rare-gas atoms and embedded in a polarizable continuum medium. Interactions with the surrounding medium affects both the position and the width of the surface plasmon absorption band of metal clusters. The size dependent shift of the surface plasmon band is evaluated in the case of a neon matrix. While the band shifts to lower energies (red shift) for large clusters, it shifts to higher energies (blue shift) for very small clusters.
关键词： Silver Nanoclusters,Optical,TDDFT,Plasmonics,Magnetic,Hybrid Materials,Rare-Gas Matrices
更新于2025-09-09 09:28:46
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Unraveling the Role of Π - Conjugation in Thiophene Oligomers for Optoelectronic Properties by DFT/TDDFT Approach
摘要： Thiophene oligomer has been investigated using DFT/TDDFT calculations with an aim to check its suitability for opto electronic applications and also to analyse the influence of π-bridge. Our results revealed that thiophene oligomers have excellent π-conjugation throughout. FMO analysis give an estimate of band gap of thiophene oligomer and further revealed HOMO are localized on π – bridge, donor group and LUMO are localized on π – bridge and acceptor group. A TDDFT calculation has been performed to understand the absorption properties of them in gas phase and solvent phase. PCM calculations convey that absorption maxima show positive solvatochromism. Among the designed candidates, the one with more π – bridge show higher wavelength of absorption maxima and would be a choice for better optoelectronic materials. NBO analysis provides support for complete delocalization in these systems. It is interesting to note that oligomer with more π–bridge display an enhanced optoelectronic properties than with less π – bridge.
关键词： Thiophene oligomer,TDDFT,π – bridge,PCM,NBO
更新于2025-09-09 09:28:46
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<i>Ab Initio</i> Prediction of Fluorescence Lifetimes Involving Solvent Environments by Means of COSMO and Vibrational Broadening
摘要： The fluorescence lifetime is a key property of fluorophores that can be utilized for microenvironment probing, analyte sensing, and multiplexing as well as barcoding applications. For the rational design of lifetime probes and barcodes, theoretical methods have been developed to enable the ab initio prediction of this parameter, which depends strongly on interactions with solvent molecules and other chemical species in the emitter′s immediate environment. In this work, we investigate how a conductor-like screening model (COSMO) can account for variations in fluorescence lifetimes that are caused by such fluorophore-solvent interactions. Therefore, we calculate vibrationally broadened fluorescence spectra using the nuclear ensemble method to obtain distorted molecular geometries to sample the electronic transitions with time-dependent density functional theory (TDDFT). The influence of the solvent on fluorescence lifetimes is accounted for with COSMO. For an example 4-hydroxythiazole fluorophore containing different heteroatoms and acidic and basic moieties in aprotic and protic solvents of varying polarity, this approach was compared to experimentally determined lifetimes in the same solvents. Our results demonstrate a good correlation between theoretically predicted and experimentally measured fluorescence lifetimes except for the polar solvents ethanol and acetonitrile that can specifically interact with the heteroatoms and the carboxylic acid of the thiazole derivative.
关键词： Fluorescence Lifetimes,Quantum Chemistry,Molecular Structure,TDDFT,Spectroscopy,Vibrational Broadening,COSMO
更新于2025-09-09 09:28:46
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Can BODIPY Dimers Act as Photosensitizers in Photodynamic Therapy? A Theoretical Prediction
摘要： The photophysical properties of some monomeric and dimeric BODIPY systems were investigated at the density functional theory level and herein reported. In particular, the absorption spectra were fully characterized, low energy singlet and triplet excited states were discussed also focusing on the energy difference gaps between them and computing the spin-orbit couplings values for the possible intersystem crossing channels. The heavy atom effect of iodine substituents on the photophysical properties of a monomer and on a dimer under investigation was also estimated. Results obtained on the considered compounds allow us to predict which is the most promising candidate to be suggested as a photosensitizer in photodynamic therapy.
关键词： BODIPY,PDT,heavy atom effect,TDDFT,spin-orbit coupling
更新于2025-09-04 15:30:14
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Photo induced trans→cis isomerism studies of heteroleptic iridium complex with 8-quinolinol-5-phenylazo ligand: Photophysical and electrochemical studies and it's theoretical investigations
摘要： Free rotating azo type ligand in different types of metal complexes give trans-cis isomerism in presence of photon irradiation by UV light. For this connection one new iridium complex has been synthesized with 8-hydroxyquinoline-5-phenylazo ligand in which the azo part of the ligand is free from coordination with metal centre. UV light irradiation of the Ir complex with this type of 8-hydroxyquinoline-5-arylazo ligand at room temperature promotes the trans→cis photoisomerization of the N=N bond with formation of a cis-isomer. The complex is characterised by single X-ray diffractometry, IR, mass and 1HNMR spectroscopy method. Here we report on the synthesis, the electrochemical properties and the photophysical characterization of donor-acceptor azobenzene derivative that possess 8-quinolinol group connected to a benzene moiety and it’s cis-trans isomerisation reaction and stability of the isomers. Thoroughly DFT and TD-DFT calculations are performed to correlate experimental and theoretical interpretation.
关键词： Cis-trans isomerism,Iridium(III) complex,Absorption and emission Study,DFT and TDDFT study
更新于2025-09-04 15:30:14
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Simultaneous Prediction of the Energies of <i> Q <sub/><i>x</i> </sub></i> and <i> Q <sub/><i>y</i> </sub></i> Bands and Intramolecular Charge-Transfer Transitions in Benzoannulated and Non-Peripherally Substituted Metal-Free Phthalocyanines and Their Analogues: No Standard TDDFT Silver Bullet Yet
摘要： An insight into the electronic structure of the metal-free, unsubstituted, and nonperipherally substituted with electron-donating groups tetraazaporphyrin (H2TAP), phthalocyanine (H2Pc), naphthalocyanine (H2Nc), anthracocyanine (H2Ac) platforms has been gained and discussed on the basis of experimental UV?vis and MCD spectra as well as density functional theory (DFT), time-dependent DFT (TDDFT), and semiempirical ZINDO/S calculations. Experimental data are suggestive of potential crossover behavior between the 11B2u and 11B3u excited states (in traditional D2h notation) around 800 nm. A large array of exchange-correlation functionals were tested to predict the vertical excitation energies in H2TAPs, H2Pcs, H2Ncs, and H2Acs both in gas phase and solution. In general, TDDFT-predicted energies of the Qx and Qy bands and the splitting between them correlate well with the amount of Hartree?Fock exchange present in a speci?c exchange-correlation functional with the long-range corrected LC-BP86 and LC-wPBE functionals providing the best agreement between theory and experiment. The pure GGA (BP86) exchange-correlation functional signi?cantly underestimated, while long-range corrected LC-BP86 and LC-wPBE exchange-correlation functionals and semiempirical ZINDO/S method strongly overestimated the intramolecular charge-transfer (ICT) transitions experimentally observed for -OR, -SR, and -NR2 substituted at nonperipheral position phthalocyanines and their analogues in the 450?650 nm region. The hybrid CAM-B3LYP, PBE1PBE, and B3LYP exchange-correlation functionals were found to be much better in predicting energies of such ICT transitions. Overall, we did not ?nd a single exchange-correlation functional that can accurately (MAD < 0.05 eV) and simultaneously predict the energies and the splittings of the Qx and Qy bands as well as energies of the ICT transitions in a large array of substituted and unsubstituted metal-free phthalocyanines and their benzoannulated analogues.
关键词： electronic structure,metal-free phthalocyanines,UV?vis,intramolecular charge-transfer,MCD spectra,ZINDO/S,TDDFT
更新于2025-09-04 15:30:14
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Angle-resolved photoelectron spectroscopy and scanning tunnelling spectroscopy studies of the endohedral fullerene Li@C <sub/>60</sub>
摘要： Gas phase photoelectron spectroscopy (Rydberg Fingerprint Spectroscopy), TDDFT calculations and low temperature STM studies are combined to provide detailed information on the properties of the di?use, low-lying Rydberg-like SAMO states of isolated Li@C60 endohedral fullerenes. The presence of the encapsulated Li is shown by the calculations to produce a signi?cant distortion of the lowest-lying S- and P-SAMOs that is dependent on the position of the Li inside the fullerene cage. Under the high temperature conditions of the gas phase experiments, the Li is mobile and able to access di?erent positions within the cage. This is accounted for in the comparison with theory that shows a very good agreement of the photoelectron angular distributions, allowing the symmetry of the observed SAMO states to be identi?ed. When adsorbed on a metal substrate at low temperature, a strong interaction between the low-lying SAMOs and the metal substrate moves these states to energies much closer to the Fermi energy compared to the situation for empty C60 while the Li remains frozen in an o?-centre position.
关键词： Rydberg Fingerprint Spectroscopy,SAMO states,TDDFT calculations,Li@C60,STM studies
更新于2025-09-04 15:30:14