Time-dependent Density Functional Theory Calculations Research Articles

Selecting electronic transitions between graphyne and lithium ions for entanglement generation using new organic material

This study explores the entanglement potential in a graphyne (GM) system embedded with lithium ions, employing time-dependent density functional theory (TD-DFT) calculations. A finite, non-periodic GM structure was optimized using the B3LYP functional and the 6-311G(d,p) basis set. Lithium ions were strategically positioned at various distances from the GM to investigate their interactions, focusing on charge transfer transitions to the unoccupied 2s orbitals of the lithium ions. Successful electronic transitions were identified and validated, emphasizing the role of contemporary atomic manipulation technologies such as optical tweezers. This research enhances the understanding of entanglement mechanisms in quantum systems and proposes potential applications in secure quantum communication and advanced quantum computing. The practical feasibility of precise atomic manipulation, enabled by cutting-edge technologies, underscores the applicability of the proposed configurations.

Electronic Structures of an Annulated meso-Tetraphenylchlorin and a Related Chlorin Analogue Incorporating an 8-Membered Ring through MCD Spectroscopy and DFT Calculations.

Herein, we compare the electronic structures of the metal-free and nickel(II) derivatives of an annulated meso-tetraphenyldihydroxychlorin with those of the (metallo)chlorin analogues derived by pyrroline β,β'-ring cleavage of the annulated (metallo)chlorins. These (metallo)chlorin analogues incorporate 8-membered heterocycles in place of the pyrroline, carry oxo-functionalities on the former pyrroline β-carbon atoms, and were previously shown to possess drastically ruffled (twisted) nonplanar conformations. The magnetic circular dichroism spectra of all chromophores investigated feature chlorin-like UV-vis spectra and correspondingly reversed (positive-to-negative in ascending energy) sign sequences in the Q-band region, indicative of ΔHOMO < ΔLUMO relationships. Density functional theory (DFT) calculations indicate that the HOMOs in all compounds are a1u-type molecular orbitals (in traditional for the porphyrin spectroscopy D4h point group). Time-dependent DFT calculations correlate well with the experimental spectra and indicate that Gouterman's four-orbital model can be applied to these chromophores. This work highlights to which degree synthetic chlorin analogues can deviate from the structural parameters of natural chlorins without losing their electronic chlorin characteristics.

Direct probing of low-energy intra d-band transitions in gas-phase cobalt clusters

The interplay between constituent localized and itinerant electrons of metal clusters defines their physical and chemical properties. In turn, the electronic and geometrical structures are strongly entwined and exhibit strong size-dependent variations. Current understanding of low-energy excited states of metal clusters relies on stand-alone theoretical investigations and few comparisons with measured properties, since direct identification of low-lying states is lacking hitherto. Here, we report on the measurement of low-lying electronic transitions in cationic cobalt clusters using infrared photofragmentation spectroscopy. Broad and size-dependent absorption features were observed within 0.056 – 0.446 eV, well above the energies of the sharp absorption bands caused by cluster vibrations. Complementary time-dependent density functional theory calculations reproduce the main observed absorption features, providing direct evidence that they correspond to transitions between electronic states of mainly d-character, arising from the open d-shells of the Co atoms and the high spin multiplicity of the clusters.

Synthesis and Characterization of a Cyclic Trimer of a Chiral Spirosilabifluorene.

A chiral shape-persistent macrocyclic compound (Si-[3]), designed by the C/Si substitution in the spiro-atom of spirobifluorene in the cyclic trimer (C-[3]), has been successfully synthesized in this study. The C/Si substitution made the spiro-conjugation and energy levels of HOMO and LUMO decrease. Due to the silicon substitution, the macrocyclic compound Si-[3] was able to be degraded by fluoride ions, but its reaction rate was slower than that of the unsubstituted spirosilabifluorene, showing the chemical stability of Si-[3]. Furthermore, the chiroptical properties of Si-[3] with D3-symmetric macrocyclic structure were investigated, and (P,P,P)-Si-[3] showed a high emission quantum yield (Φf=80 %) and moderate dissymmetry factor of circularly polarized luminescence (CPL) (glum,exp=-1.2×10-3). According to the time-dependent density-functional theory (TD-DFT) calculations using polarizable continuum model (PCM), the bright CPL from Si-[3] was explained by a planarization of one bisilafluorenyl moiety at the excited state, which is responsible for the almost fully-allowed radiative transition with a short emission lifetime of τf=1.89 ns.

The influence of positional isomerism of a cyano group of pyrene-based rod-like mesogens on mesomorphism, dual-state emission and multiple applications

Two novel cyanostilbene-based rod-like mesogens consisting of one terminal pyrene and one terminal alkyl chain were prepared by Suzuki coupling and Knoevenagel reactions. The influence of the positional isomerism of the cyano group of cyanostilbene unit on the liquid crystalline characteristics, photophysical characteristics, and mechanochromism characteristics was studied by using polarized optical microscopy, differential scanning calorimetry, X-ray diffraction, absorption spectra, photoluminescence spectra, density functional theory calculation and time-dependent density functional theory calculation. The mesogen in which the cyano group is adjacent to the phenylpyrene unit exhibits a monotropic smectic C phase, whereas the mesogen in which the cyano group is far away from the phenylpyrene unit exhibits an enantiotropic smectic C phase. The mesogen in which the cyano group is adjacent to the phenylpyrene unit exhibits more distinct positive solvatochromism due to more distinct intramolecular charge transfer. The mesogen in which the cyano group is adjacent to the phenylpyrene unit exhibits aggregation-induced emission behavior, but the mesogen in which the cyano group is far away from the phenylpyrene unit exhibits dual-state emission behavior. Reversible mechanochromism behavior could be achieved in both mesogens due to twisted molecular configurations. In addition, the rewritable luminescent paper and bioimaging applications were also achieved. These results demonstrated that the distinct molecular design could endow organic molecules with multifunctional properties and potential applications.

Time-dependent density-functional theory study on nonlocal electron stopping for inertial confinement fusion

Understanding laser–target coupling is of the utmost importance for achieving high performance in laser-direct-drive (LDD) inertial confinement fusion (ICF) experiments. Thus, accurate modeling of electron transport and deposition through ICF-relevant materials and conditions is necessary to quantify the total thermal conduction and ablation. The stopping range is a key transport quantity used in thermal conduction models; in this work, we review the overall role that the electron mean free path (MFP) plays in thermal conduction and hydrodynamic simulations. The currently used modified Lee–More model employs various physics approximations. We discuss a recent model that uses time-dependent density functional theory (TD-DFT) to eliminate these approximations in both the calculation of the electron stopping power and corresponding MFP in conduction zone polystyrene (CH) plasma. In general, the TD-DFT calculations showed a larger MFP (lower stopping power) than the standard modified Lee–More model. Using the TD-DFT results, an analytical model for the electron deposition range, λTD−DFT(ρ,T,K), was devised for CH plasmas between ρ=[0.05−1.05] g/cm3, kBT=[100−1000] eV. We implemented this model into LILAC, for simulations of a National Ignition Facility-scale LDD implosion and compared key physics quantities to ones obtained by simulations using the standard model. The implications of the obtained results and the path moving forward to calculate this same quantity in conduction-zone deuterium–tritium plasmas are further discussed, to hopefully close the understanding gap for laser target coupling in LDD-ICF simulations.

Visible and Red Light-Triggered Anticancer Profile of a Ferrocene-Re(I)-Tricarbonyl Conjugate: Experimental and Theoretical Studies.

We have red-shifted the light absorbance property of a Re(I)-tricarbonyl complex via distant conjugation of a ferrocene moiety and developed a novel complex ReFctp, [Re(Fctp)(CO)3Cl], where Fctp = 4'-ferrocenyl-2,2':6',2″-terpyridine. ReFctp showed green to red light absorption ability and blue emission, indicating its potential for photodynamic therapy (PDT) application. The conjugation of ferrocene introduced ferrocene-based transitions, which lie at a higher wavelength within the PDT therapeutic window. The time-dependent density functional theory and excited state calculations revealed an efficient intersystem crossing for ReFctp, which is helpful for PDT. ReFctp elicited both PDT type I and type II pathways for reactive oxygen species (ROS) generation and facilitated NADH (1,4-dihydro-nicotinamide adenine dinucleotide) oxidation upon exposure to visible light. Importantly, ReFctp showed effective penetration through the layers of clinically relevant 3D multicellular tumor spheroids and localized primarily in mitochondria (Pearson's correlation coefficient, PCC = 0.65) of A549 cancer cells. ReFctp produced more than 20 times higher phototoxicity (IC50 ∼1.5 μM) by inducing ROS generation and altering mitochondrial membrane potential in A549 cancer cells than the nonferrocene analogue Retp, [Re(CO)3(tp)Cl], where tp = 2,2':6',2″-terpyridine. ReFctp induced apoptotic mode of cell death with a notable photocytotoxicity index (PI, PI = IC50dark/IC50light) and selectivity index (SI, SI = normal cell's IC50dark/cancer cell's IC50light) in the range of 25-33.

Water-Regulated Evolution of Inversion, Reinversion, and Amplification of Circularly Polarized Luminescence of Supramolecular Organogels Based on Glutamide-Cyanostilbene Amphiphile.

Water incorporated with supramolecular building blocks in organic solvents can play a key role in the circularly polarized luminescence (CPL) inversion and amplification of supramolecular assemblies. Herein, we demonstrate that fine-tuning the water content regulated the assembly structure evolution and made the circular dichroism and CPL sign of the system undergo intriguing inversion, reinversion, and amplification processes based on a unique and interesting glutamide-cyanostilbene system, as supported by morphology, spectroscopic observations, and time-dependent density functional theory calculation.

New piperazine derivatives helvamides B–C from the marine-derived fungus Penicillium velutinum ZK-14 uncovered by OSMAC (One Strain Many Compounds) strategy

Four extracts of the marine-derived fungus Penicillium velutinum J.F.H. Beyma were obtained via metal ions stress conditions based on the OSMAC (One Strain Many Compounds) strategy. Using a combination of modern approaches such as LC/UV, LC/MS and bioactivity data analysis, as well as in silico calculations, influence metal stress factors to change metabolite profiles Penicillium velutinum were analyzed. From the ethyl acetate extract of the P. velutinum were isolated two new piperazine derivatives helvamides B (1) and C (2) together with known saroclazin A (3) (4S,5R,7S)-4,11-dihydroxy-guaia-1(2),9(10)-dien (4). Their structures were established based on spectroscopic methods. The absolute configuration of helvamide B (1) as 2R,5R was determined by a combination of the X-ray analysis and by time-dependent density functional theory (TD-DFT) calculations of electronic circular dichroism (ECD) spectra. The cytotoxic activity of the isolated compounds against human prostate cancer PC-3 and human embryonic kidney HEK-293 cells and growth inhibition activity against yeast-like fungi Candida albicans were assayed.Graphical

A theoretical study on the solvent effects on adsorption behavior of naproxen with PLGA nanoparticles

The objective of this research is to study the influence of naproxen (NPX) adsorption on structural, electronic, and optical features of poly (lactic-co-glycolic acid) (PLGA) in the dichloromethane (CH2Cl2), chloroform (CHCl3), and water (H2O) phases through density functional dispersion correction (DFT-D) calculations. The analyses conducted in the chloroform phase, considering binding energy and chemical reactivity parameters, indicate that NPX forms stronger hydrogen bonds with PLGA in state B (−0.60 eV) compared to states A (−0.37 eV) and C (−0.47 eV), primarily through its carboxyl (–COOH) group by using B3LYP-D/6–311 + G** level of theory. The formation of hydrogen bonds between naproxen and PLGA in the chloroform phase is most stable compared to the dichloromethane and water phases. According to time-dependent density functional theory (TDDFT) calculations, the B3LYP method predicts the maximum optical absorption in the UV region for complex B, with an optical energy of 5.41 eV and an oscillator strength of 0.781, resulting in a maximum absorption peak at 229 nm. Based on the infrared (IR) spectra analysis, we find alterations in pristine PLGA and NPX due to their interaction. The interaction between NPX and PLGA results in more negative Gibbs free energy (ΔG) values, which in turn lead to an elevation in dipole moment, enhanced solubility, and a decrease in the energy gap (Eg). As a result of NPX adsorption, the decreased energy gaps enhance the electronic and optical sensitivity of PLGA to the NPX molecule.

The Influence of the Alkylamino Group on the Solvatochromic Behavior of 5-(4-substituted-arylidene)-1,3-dimethylpyrimidine-2,4,6-triones: Synthesis, Spectroscopic and Computational Studies.

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

Theoretical study on the mechanism of alcohol photooxidation on Nb2O5 surface.

Theoretical modeling of the solid-state photocatalysis is one of the important issues as various useful photocatalysts have been developed to date. In this work, we investigated the mechanism of the alcohol photooxidation on niobium oxide (Nb2O5) which was experimentally developed, using the density functional theory (DFT)/time-dependent (TD)DFT calculations based on the cluster model. The alcohol adsorption and the first hydrogen transfer from hydroxy group to surface occur in the ground state, while the second hydrogen transfer from CH proceeds in the excited states during the photoirradiation of UV or visible light. The spin crossing was identified and the low-lying triplet states were solved for the reaction pathway. The photoabsorption in the visible light region was characterized as the charge transfer transition from O 2p of alcohol to Nb 4d of the Nb2O5 surface. The spin density and the natural population analysis indicated the generation of spin density in the moiety of carbonyl compound and its dissipation to the interface of the surface, which partly explains the electron paramagnetic resonance measurement. It was confirmed that the rate determining step is the desorption of carbonyl compound and water molecule in agreement with the experimental rate equation analysis. The present findings with the theoretical modeling will provide useful information for the further studies of the solid-state photocatalysis.

Theoretical Insights into the Structural and Optical Properties of D-π-A-based Cyanostilbene Systems of α and β Variants.

The π-conjugated organic molecules containing cyanostilbene motifs have been extensively investigated due to their great potential applications in several optoelectronic and biological fields. Developing efficient molecules in this respect requires strategic structural engineering and a deep understanding of the structure-property relationship at the molecular level. In this context, understanding the impact of positional isomerism in cyanostilbene systems is a fundamental aspect of designing desired materials with improved photophysical properties. Herein, we designed ten donor-π-acceptor (D-π-A) type cyanostilbene derivatives (P1 - P10) with different π linkers and compared their structural and optoelectronic properties arising from the positional variations of the -CN group (α and β- variations) through the utilization of density functional theory (DFT) and time-dependent DFT (TDDFT) methods. The topological analyses of the electron density are used to explain the relatively high stability of α isomer compared to that of β. Frontier molecular orbital analysis reveals that 17 molecules tend to show a reduced highest occupied molecular orbital-lowest unoccupied molecular orbital gap, and most of them showed a greater nonlinear optical (NLO) character compared to the parent molecule. TDDFT calculations indicate that β isomers show higher absorption maxima compared to their α counterparts. Among all the scrutinized molecules, the absorption maximum extended up to 602 nm for P9 and it possesses the highest first-order hyperpolarizability. This study sheds light on positional isomers and their reactivity, absorption spectra, and NLO properties of D-π-A type architecture that can be suitably tuned by appropriating the π-bridge for practical applications.

Two-photon absorption in bioactive C4-substituted Coumarin derivatives: Impact of electron-withdrawing and donating groups in different environment

The versatile applications of coumarin derivatives in materials processing, fluorescence imaging, data storage, and photodynamic therapy have sparked considerable interest in scientific community. In this research paper, we explore the UV–vis spectra, IR spectra, and two photon absorption (TPA) characteristics of biological active coumarin derivatives under the influence of electron withdrawing (specifically X = CONH2, CHO, and NO2) and electron donating (X= -CH3, -OH, -NH2) functional groups at C-4 position. To delve into the absorption spectra, we employ time-dependent density functional theory calculations. Results revealed that acceptor functional groups (specifically R = CONH2, CHO, and NO2) not only lower the energy of the lowest two photon active state but also increase the corresponding TPA cross-section. Furthermore, using the Conductor-like Polarizable Continuum Model (CPCM), the influence of solvent polarity on C-4 substituted coumarin derivative was also investigated. Our findings effectively capture how substitutions and solvents impact the nonlinear optical response in coumarins, as evidenced by the measurement of the two-photon absorption cross-section (σTPA). This study offers valuable insights for identifying and designing novel coumarin derivatives with C4 substitutions, unlocking new and intriguing possibilities for their practical applications.

Molecular engineering of benzothiadiazole core based non-fullerene acceptors to tune the optoelectronic properties of perovskite solar cells

Non-fullerene acceptors exhibit durable absorption capacity, and exceptional power conversion efficiency that make them appealing photovoltaic material for use as hole transport materials in perovskite solar cells (PSCs). To interpret the benzothiadiazole as the central-core unit, five novel acceptors (U1-U5) have been successfully fabricated by end-capped engineering. Their electrical and optical performance have been investigated theoretically. Utilizing density functional theory (DFT) and time-dependent DFT computations, we have examined the photo-physical and optoelectronic characteristics. U4 exhibits 3.80 eV optical band gap with an absorption (λmax) of 670.58 nm. Lowest excitation energy (1.85 eV), greater LHE (0.98) and improved PCE (18.31 eV) validate the U4 designed molecule as a brilliant photovoltaic material for PSCs. Outstanding charge transfer at the donor–acceptor junction has also been revealed by thorough analysis of U4/PTB7-Th. Therefore, substitution of alternate functional groups in terminal moieties is efficient for effective PSCs that can be used as photon harvesting materials.

Extending the limit of LR-TDDFT on two different approaches: Numerical algorithms and new Sunway heterogeneous supercomputer

First-principles time-dependent density functional theory (TDDFT) is a powerful tool to accurately describe the excited-state properties of molecules and solids in condensed matter physics, computational chemistry, and materials science. However, a perceived drawback in TDDFT calculations is its ultrahigh computational cost O(N5∼N6) and large memory usage O(N4) especially for plane-wave basis set, confining its applications to large systems containing thousands of atoms. Here, we present a massively parallel implementation of linear-response TDDFT (LR-TDDFT) and accelerate LR-TDDFT in two different aspects: (1) numerical algorithms on the X86 supercomputer and (2) optimizations on the heterogeneous architecture of the new Sunway supercomputer. Furthermore, we carefully design the parallel data and task distribution schemes to accommodate the physical nature of different computation steps. By utilizing these two different methods, our implementation can gain an overall speedup of 10x and 80x and efficiently scales to large systems up to 4096 and 2744 atoms within dozens of seconds.

Photophysical Studies of a Zr(IV) Complex with Two Pyrrolide-Based Tetradentate Schiff Base Ligands.

The reaction of two equivalents of N,N'-bis(2-pyrrolylmethylidene)-1,2-phenylenediamine (H2bppda) with tetrabenzylzirconium provided the air- and moisture-stable eight-coordinate complex Zr(bppda)2. Temperature-dependent steady-state and time-resolved emission spectroscopy established weak photoluminescence (ΦPL = 0.4% at 293 K) by a combination of prompt fluorescence and thermally activated delayed fluorescence (TADF) upon visible light excitation at and around room temperature. TADF emission is strongly quenched by 3O2 and shows highly temperature-sensitive emission lifetimes of hundreds of microseconds. The lifetime of the lowest energy singlet excited state, S1, was established by transient absorption spectroscopy and shows rapid deactivation (τ = 142 ps) by prompt fluorescence and intersystem crossing to the triplet state, T1. Time-dependent density functional theory (TD-DFT) calculations predict moderate ligand-to-metal charge transfer (LMCT) contributions of 25-30% for the S1 and T1 states. A comparison of Zr(bppda)2 to related zirconium pyridine dipyrrolide complexes, Zr(PDP)2, revealed important electronic structure changes due to the eight-coordinate ligand environment in Zr(bppda)2, which were correlated to differences in the photophysical properties between the two compound classes.

Inverse Hypercorroles.

Ground-state and time-dependent density functional theory (TDDFT) calculations with the long-range-corrected, Coulomb-attenuating CAMY-B3LYP exchange-correlation functional and large, all-electron STO-TZ2P basis sets have been used to examine the potential "inverse hypercorrole" character of meso-p-nitrophenyl-appended dicyanidocobalt(III) corrole dianions. The effect is most dramatic for 5,15-bis(p-nitrophenyl) derivatives, where it manifests itself in intense NIR absorptions. The 10-aryl groups in these complexes play a modulatory role, as evinced by experimental UV-visible spectroscopic and electrochemical data for a series of 5,15-bis(p-nitrophenyl) dicyanidocobalt(III) corroles. TDDFT (CAMY-B3LYP) calculations ascribe these features clearly to a transition from the corrole's a2u-like HOMO (retaining the D4h irrep used for metalloporphyrins) to a nitrophenyl-based LUMO. The outward nature of this transition contrasts with the usual phenyl-to-macrocycle direction of charge transfer transitions in many hyperporphyrins and hypercorroles; thus, the complexes studied are aptly described as inverse hypercorroles.

Orbital-Optimized Versus Time-Dependent Density Functional Calculations of Intramolecular Charge Transfer Excited States.

The performance of time-independent, orbital-optimized calculations of excited states is assessed with respect to charge transfer excitations in organic molecules in comparison to the linear-response time-dependent density functional theory (TD-DFT) approach. A direct optimization method to converge on saddle points of the electronic energy surface is used to carry out calculations with the local density approximation (LDA) and the generalized gradient approximation (GGA) functionals PBE and BLYP for a set of 27 excitations in 15 molecules. The time-independent approach is fully variational and provides a relaxed excited state electron density from which the extent of charge transfer is quantified. The TD-DFT calculations are generally found to provide larger charge transfer distances compared to the orbital-optimized calculations, even when including orbital relaxation effects with the Z-vector method. While the error on the excitation energy relative to theoretical best estimates is found to increase with the extent of charge transfer up to ca. -2 eV for TD-DFT, no correlation is observed for the orbital-optimized approach. The orbital-optimized calculations with the LDA and the GGA functionals provide a mean absolute error of ∼0.7 eV, outperforming TD-DFT with both local and global hybrid functionals for excitations with a long-range charge transfer character. Orbital-optimized calculations with the global hybrid functional B3LYP and the range-separated hybrid functional CAM-B3LYP on a selection of states with short- and long-range charge transfer indicate that inclusion of exact exchange has a small effect on the charge transfer distance, while it significantly improves the excitation energy, with the best-performing functional CAM-B3LYP providing an absolute error typically around 0.15 eV.

Chiral induction and amplification of achiral molecules induced by chiral compounds in solid matrices

Abstract To demonstrate chiral induction and amplification in the solid state, we investigated co-crystals prepared from (S)- or (R)-1-phenylethylamine and achiral biphenyl-4-carboxylic acid by solvent-free crystallization. The chiroptical and optical properties of the co-crystals were characterized by circular dichroism spectroscopy, Fourier transform infrared spectroscopy, and time-dependent density functional theory calculations, revealing chiral induction, and amplification in the solid phase.