Time-dependent Density Functional Theory Theory Research Articles

Investigation of substituent effects on the electronic structure and antiviral activity of favipiravir derivatives for Covid-19 treatment using DFT and molecular docking

In this study, Density-functional theory/Time-dependent density-functional theory (DFT/TDDFT) and Molecular docking method was used to investigate the effect of methyl acetate, tetrahydrofuran and cyanobenzylidene substituents on the electronic structure and antiviral activity of favipiravir for treating COVID-19. The DFT and TDDFT computations were employed using the Gaussian 09 software package. The values were calculated using the 6-311++G(d, p) basis set and the hybrid B3LYP functional method. Autodock vina software was used for simulations to better predictions and to validate the modified compounds' binding affinities and poses. Results of the study indicate that compounds 1 to 6 all displayed a planar structure, where the pyrazine ring, carboxamide, hydroxyl groups, and other substituents are all situated within the same plane. In addition, the energy gaps (Egap) of these six compounds (Cpd 1, 2, 3, 4, 5, and 6) were compared. The significant dipole moment and binding affinity achieved implies a particular orientation for binding within the target protein, signaling the anticipated strength of the binding interaction. In all six compounds, the electrophilic domain is situated in the vicinity of the amine functional group within the carboxamide compound, whereas the nucleophilic domain encompasses both the carbonyl and hydroxyl groups. The most negatively charged sites are susceptible to electrophilic interactions. In conclusion, compounds 5 and 6 exhibit a high binding affinity of the target protein, while compound 6 has a high energy gap, which could enhance its antiviral activity against the COVID-19 virus.

Tuning the photovoltaic potential of thiazole based materials via incorporation of selenophene and electron acceptors rings at peripheral positions: A DFT approach

The non-fullerene acceptor (NFA) chromophores have sparked scientific and economic interest, due to their rapid advancements in power conversion efficiencies. Therefore, a series of new chlorothiazole based compounds (STM1-STM6) with A1–π–A2–π–A1 configuration was designed using reference chromophore (STMR). Structural modifications were made via incorporating selenophene and extended acceptor units, to enhance photovoltaic response in the designed materials. Density functional theory/time dependent-density functional theory (DFT/TD-DFT) calculations were executed at M06/6-311G (d,p) level to investigate key electronic and photovoltaic properties of STM1-STM6. So, various analyses such as UV–Visible, frontier molecular orbitals (FMOs), transition density matrix (TDM), density of states (DOS), open circuit voltage (Voc) and binding energy (Eb) were conducted to comprehend the photovoltaic properties. The designing in structural aspects with terminal acceptors and π-linker induced a reduction in energy gaps (ΔE = 2.078–2.237 eV) with an enhancement in the bathochromic shift (λmax = 744.650–798.250 nm in chloroform) than reference compound. A higher exciton dissociation rate was observed in all the compounds due to lower binding energy values (Eb = 0.525–0.572 eV). Additionally, TDM and DOS findings further endorsed the effective charge delocalization from HOMO to LUMO. Among all the examined compounds, STM3 exhibited the smallest band gap (2.078 eV), highest absorption maxima (798.250 nm), and the lowest exciton binding energy (0.525 eV), indicating significant electronic properties. Moreover, Voc analysis was conducted with respect to HOMOPBDBT-LUMOacceptor for all the designed chromophores; consequently, STM2 demonstrated a substantial Voc value of 1.647 V. Similarly, electron hole analysis was also conducted and significant electron and hole density was observed in all the investigated compounds, especially in STM2. The entitled compounds with photovoltaic potential would be considered as promising materials for the development of solar energy devices.

Exploring promising photovoltaic properties of dithiophene-based non-fullerene chromophores for efficient organic solar cells: A DFT approach

Currently, non-fullerene-based acceptors in organic solar cells (OSCs) have gained significant attention of researchers owing to their particular characteristics. Herein, new W-shaped dithiophene based acceptor chromophores (D1-D8) possessing A-π-D-π-A configuration were fabricated via end group structural tailoring by utilizing promising acceptors groups. To probe the effect of end group manipulation on the optoelectronic properties of entitled chromophores, density functional theory/time-dependent density functional theory (DFT/TD-DFT) calculations were accommodated at B3LYP/6–311 G(d,p) functional. Frontier molecular orbitals (FMOs) findings revealed that the derivatives (D1-D8) exhibited narrow band gap (1.191–2.110 eV) than that of reference chromophore (R=2.380 eV) due to efficient acceptor moieties. UV–Vis data collected in chloroform solvent revealed that λmax values of D1-D8 were existed in visible region (738.6–692.5 nm). Moreover, D2 and D4 proves to be the best chromophores exhibiting least band gap of 1.191 and 2.000 eV and broad absorption spectrum i.e., 738.573 and 735.986 nm, respectively. Among all the designed compounds, D2, D3, D4 and D6 manifested higher open circuit voltage values. Theoretical analysis disclosed that all the designed molecules exhibited almost comparable results with each other. Nevertheless, D2 and D4 provided significant findings and can be utilized as best candidate for use in optoelectronic devices.

Structural modifications and biomedical applications of π-extended, π-fused, and non-fused tetra-substituted imidazole derivatives

In this present study, we have designed, synthetized twenty three tetra-substituted-imidazole-based fluorescent dyes that belongs to three different families of π-extended, π-fused, and non-fused tetra-substituted derivatives, to investigate their photophysical and biological properties namely anti-cancer and urease inhibitory activity. The impact of structural variation on photophysical properties, and their association with solvent’s polarity, and proticity were throughly examined by comparing with their analogues of blocked ESIPT functionality. Further, they were studied experimentally by means of absorption and fluorescence spectra monitoring through different solvent systems as well as theoretically by density functional theory/time dependent-density functional theory (DFT/TDDFT) calculations, respectively. For the evaluation of biological properties of imidazole molecules, urease inhibitory activity of the imidazole derivatives against urease protein 4H9M was investigated through docking and in vitro studies. Among the synthesized compounds, AHPI-Br and POMPI-F showed the most effective urease inhibitory activity with IC50 values of 0.0288 ± 0.0034 and 0.0289 ± 0.0025 μM and provided the highest docking scores. Moreover, anti-cancer activity of PHPI-I and PHPI-CI imidazole derivatives was confirmed by cytotoxic, and flurorescene analysis in stomach cancer cell lines (AGS). Our results demonstrated that PHPI-I, PHPI-Cl exhibited significant apoptotic mediated cell death compared to all other imidazole groups in both in vitro and in silico analysis. Our present study concluded that synthesis of imidazole derivatives have ability to inhibit urease enzyme activity and anti-cancer activity in vitro and can act as a potential therapeutic targets and warrants in vivo studies.

Exploration of photovoltaic behavior of fused triphenylamine moiety as core donor with modified acceptors: Star-shaped D-[formula omitted]-A conjugated systems

Fullerene-free organic chromophores have drawn considerable attention as successful photonic devices for organic solar cells. So, a series of novel non-fullerene-based donor molecules (HBTD2–HBTD9) were fabricated via structural modification of the terminal acceptor groups from HBTR1. In order to achieve the photovoltaic, photophysical, and electronic behavior of fore-said compounds, density functional theory/time-dependent density functional theory (DFT/TD-DFT) based analyses were accomplished at B3LYP functional along with 6-311G(d,p) basis set. The optical and electrical characteristics of the derivatives were compared with HBTR1 architecture. All designed molecules exhibited a lower EHOMO-ELUMO band gap (2.183–4.106 eV) with a red shift in absorbance compared to the reference compound (4.179 eV). All derivatives (HBTD2–HBTD9), except HBTD3, showed a greater exciton dissociation rate due to low binding energy (Eb = −0.337 to 1.400 eV) when compared with HBTR1 (Eb = 1.401 eV). Interestingly, HBTD9 manifested to be the prime candidate for non-fullerene organic solar cells (NF–OSCs) owing to the lowest energy band gap, large mobility of charges, and least value of binding energy while holding an excellent redshift value compared to all the designed chromophores. This study revealed that these chromophores would be potential competitors in manufacturing effective optoelectronic materials.

Understanding the Deactivating/Activating Mechanisms in Three Optical Chemosensors Based on Crown Ether with Na+ /K+ Selectivity Using Quantum Chemical Tools.

The optical properties and transduction mechanisms in three reported optical chemosensors based on crown ether with selectivity turn-on luminescence toward Na+ over K+ , were investigated using Density Functional Theory/Time-Dependent Density Functional Theory (DFT/TD-DFT). The analysis of the structural stability of the conformers enables us to understand the optical properties of the sensors and their selectivity toward Na+ . The UV-Vis absorption and the radiative channels of the adiabatic S1 excited state were assessed. In these reported sensors, the Photoinduced Electron Transfer (PET) from the nitrogen and the oxygen (O-atoms of the substituted N-phenylaza group) lone pairs to fluorophore groups lead to a nonradiative deactivation process in the fluorophore to p-conjugated anilino-1,2,3-triazol ionophore. This Intramolecular Charge Transfer (ICT) deactivation produced the luminescence quenching in the free sensors and K+ /C1 complexes. The Na+ /sensor interaction produced a Chelation Enhanced Fluorescence (CHEF) due to the inhibition of the PET and ICT, which was confirmed via the calculated oscillator strength of the emission process. The K+ /sensor interaction displayed the possibility of PET in C3; however, this fact was inconclusive to affirm the quenching of luminescence, the CHEF in C2 and C3 and the selectivity toward Na+ over K+ in these systems. For this reason, simulation of the absorption and emissions spectra (calculated oscillator strength), calculation of the kinetic parameters (in charge transfers and radiative deactivations process), analysis of the metal-ligand interaction character, and the analysis of the structural stability of the conformers were determinant factors to understand the selectivity and the optical properties of these chemosensors. The results suggest that these theoretical tools can also be used to predict the optical properties and Na+ /K+ selectivity of optical chemosensors.

Application of 2,4,5-tris(2-pyridyl)imidazole as 'turn-off' fluorescence sensor for Cu(II) and Hg(II) ions and in vitro cell imaging.

The 2,4,5-tris(2-pyridyl)imidazole (L) molecule has been evaluated as a probe for dual sensing of Hg2+ and Cu2+ ions in EtOH/HEPES buffer medium (5 mM, pH = 7.34, 1:1, v/v). Probe L shows a good sensitive and selective turn-off response in the presence of both Hg2+ and Cu2+ ions, which is comprehensible under long UV light. The probe can detect Cu2+ ion in the pH range 3-11 and Hg2+ ion in pH 6-8. The limit of detection for Cu2+ (0.77 μM) is well under the allowable limit prescribed by the United States Environmental Protection Agency. Two metal (Cu2+ /Hg2+ ) ions are needed per L for complete fluorescence quenching. The probe shows marked reversibility on treatment with Na2 EDTA, making the protocol more economical for practical purposes. Paper strip coated with the L solution of EtOH can detect the presence of Cu2+ and Hg2+ ions in the sample using visible quenching of the fluorescence intensity. Density functional theory-time-dependent density functional theory (DFT-TDDFT) calculations support experimental observations, and d-orbitals of Cu2+ /Hg2+ provide a nonradiative decay pathway. Cell imaging study using HDF and MDA-MB-231 cells also supported the viability of L in detecting Cu2+ and Hg2+ ions in living cells.

Application of TD-DFT Theory to Studying Porphyrinoid-Based Photosensitizers for Photodynamic Therapy: A Review.

An important focus for innovation in photodynamic therapy (PDT) is theoretical investigations. They employ mostly methods based on Time-Dependent Density Functional Theory (TD-DFT) to study the photochemical properties of photosensitizers. In the current article we review the existing state-of-the-art TD-DFT methods (and beyond) which are employed to study the properties of porphyrinoid-based systems. The review is organized in such a way that each paragraph is devoted to a separate aspect of the PDT mechanism, e.g., correct prediction of the absorption spectra, determination of the singlet–triplet intersystem crossing, and interaction with molecular oxygen. Aspects of the calculation schemes are discussed, such as the choice of the most suitable functional and inclusion of a solvent. Finally, quantitative structure–activity relationship (QSAR) methods used to explore the photochemistry of porphyrinoid-based systems are discussed.

Molecular engineering of indenoindene-3-ethylrodanine acceptors with A2-A1-D-A1-A2 architecture for promising fullerene-free organic solar cells

Considering the increased demand and potential of photovoltaic devices in clean, renewable electrical and hi-tech applications, non-fullerene acceptor (NFA) chromophores have gained significant attention. Herein, six novel NFA molecules IBRD1–IBRD6 have been designed by structural modification of the terminal moieties from experimentally synthesized A2-A1-D-A1-A2 architecture IBR for better integration in organic solar cells (OSCs). To exploit the electronic, photophysical and photovoltaic behavior, density functional theory/time dependent-density functional theory (DFT/TD-DFT) computations were performed at M06/6-311G(d,p) functional. The geometry, electrical and optical properties of the designed acceptor molecules were compared with reported IBR architecture. Interestingly, a reduction in bandgap (2.528–2.126 eV), with a broader absorption spectrum, was studied in IBR derivatives (2.734 eV). Additionally, frontier molecular orbital findings revealed an excellent transfer of charge from donor to terminal acceptors and the central indenoindene-core was considered responsible for the charge transfer. Among all the chromophores, IBRD3 manifested the lowest energy gap (2.126 eV) with higher λmax at 734 and 745 nm in gaseous phase and solvent (chloroform), respectively due to the strong electron-withdrawing effect of five end-capped cyano groups present on the terminal acceptor. The transition density matrix map revealed an excellent charge transfer from donor to terminal acceptors. Further, to investigate the charge transfer and open-circuit voltage (Voc), PBDBT donor polymer was blended with acceptor chromophores, and a significant Voc (0.696–1.854 V) was observed. Intriguingly, all compounds exhibited lower reorganization and binding energy with a higher exciton dissociation in an excited state. This investigation indicates that these designed chromophores can serve as excellent electron acceptor molecules in organic solar cells (OSCs) that make them attractive candidates for the development of scalable and inexpensive optoelectronic devices.

Synthesis and Properties of Dibenzothiophene Embedded Heteroporphyrins.

A series of new stable dibenzothiophene embedded heteroporphyrins were synthesized in 6-7% yields by condensing 1 equiv of dibenzothiophene-based tripyrrane with 1 equiv of four different diols, 2,5-bis(hydroxymethyl)heterocycles (furan, thiophene, selenophene, and tellurophene), under mild acid-catalyzed conditions in CH2Cl2. The formation of dibenzothiophene embedded heteroporphyrins was confirmed by high-resolution mass spectrometry and thoroughly characterized by 1D and 2D nuclear magnetic resonance (NMR) spectroscopy, absorption, electrochemical, and density functional theory/time-dependent density functional theory (DFT/TD-DFT) studies. The NMR studies indicated that the macrocycles were nonaromatic in nature. The electronic properties of the macrocycles were significantly altered as the heterocycle of the macrocycles was varied from furan to thiophene, selenophene, and tellurophene, as reflected clearly in the spectral and electrochemical properties. The macrocycles exhibited a sharp band in the region of 420-440 nm and a relatively broad absorption band(s) in the higher wavelength region of 550-800 nm. The oxa analogue was considerably blue-shifted as compared to the other macrocycles, whereas the tellura analogue exhibited relatively broadened and red-shifted absorption bands. Upon protonation of these macrocycles, the resulting diprotonated species displayed bathochromically shifted absorption bands, which were extended to the NIR region. DFT studies revealed that the macrocycles were highly distorted and strained and exhibited half chair conformation with restricted π-conjugation and confirmed their nonaromatic nature due to the lack of planarity of the macrocycle. TD-DFT studies were in agreement with the experimental spectral and electrochemical results.

Modeling Electromagnetic Wave Phenomena in Large Quantum Systems [Special Series: Guest Editorial

The articles in this special section focuses on quantum technologies. This is a third article in a special series on this topic. While the first two were concerned with basic theory, this article is the first to tackle the practical simulation of realistic systems, such as nanoantennas. Furthermore, it departs from the classical electromagnetics homogenization of material properties, conventionally represented by permittivity and permeability, by turning to the time-dependent density functional theory (TDDFT), which aims at a quantum mechanics-based analysis of light–matter interactions on the atomistic level. Following a basic introduction into the DFT and TDDFT theory, its formulation in the Lorenz gauge is presented. It is shown how the efficient computation of the electrodynamic potentials in the Lorenz gauge can help to achieve the goal of atomic-scale simulations of nanodevices, which include both quantum atomistic and longer-range electromagnetic retardation effects. Finally, the computational challenge and a road map for future calculations are shown.

A Combined Experimental and first principle studies on (ZnO)12 nanocluster

We report the biogenic synthesis of ZnO nanoparticles using Mangifera indica aqueous extract and density functional theory/time-dependent density functional theory (DFT/TD-DFT) calculations on Zn12O12 nanocluster compared with various basis sets (B3LYP/6-31G, B3LYP/LANL2DZ, and B97D). The genesis of ZnO nanoparticles was achieved from the reduction of capping agent ZnSo4. The properties of ZnO nanoparticles were signalized by UV, FTIR, FESEM-EDAX, and XRD analysis. The intense band at 380nm in the UV-Vis absorption spectrum results from the formation of ZnOnanoparticles. The structure of ZnO nanoparticles was anatomized by FESEM analysis and the presence of Zn was confirmed using EDAX. The frontier molecular orbital exploration has been investigated to govern the charge transfer characteristics of donor-acceptor moieties of the Zn12O12. The energy gap (Eg), binding energy (EB), global reactivity descriptors, and the total dipole moment has also been investigated for Zn12O12. The total density of states (DOS) was analyzed to describe the orbital hybridization of Zn12O12. Mulliken atomic charge distribution, NBO analysis and molecularelectrostatic potential (MEP) have also been studied. The first-order hyperpolarizability calculation proves that the Zn12O12 is a suitable candidate with the predominant nonlinear optical property. TD-DFT excited state analysis of Zn12O12 was completely consistent with the experimental data of the UV-Vis spectrum makes its application in solar cells.

Photochemical α-Cleavage Reaction of 3',5'-Dimethoxybenzoin: A Combined Time-Resolved Spectroscopy and Computational Chemistry Study.

Benzoin is one of the most commonly used photoinitiators to induce free radical polymerization. Here, improved benzoin properties could be accomplished by the introduction of two methoxy substituents, leading to the formation of 3’,5’-dimethoxybenzoin (DMB) which has a higher photo-cleavage quantum yield (0.54) than benzoin (0.35). To elucidate the underlying reaction mechanisms of DMB and obtain direct information of the transient species involved, femtosecond transient absorption (fs-TA) and nanosecond transient absorption (ns-TA) spectroscopic experiments in conjunction with density functional theory/time-dependent density functional theory (DFT/TD-DFT) calculations were performed. It was found that the photo-induced α-cleavage (Norrish Type I reaction) of DMB occurred from the nπ* triplet state after a rapid intersystem crossing (ISC) process (7.6 ps), leading to the generation of phenyl radicals on the picosecond time scale. Compared with Benzoin, DMB possesses two methoxy groups which are able to stabilize the alcohol radical and thus result in a stronger driving force for cleavage and a higher quantum yield of photodissociation. Two stable conformations (cis-DMB and trans-DMB) at ground state were found via DFT calculations. The influence of the intramolecular hydrogen bond on the α-cleavage of DMB was elaborated.

Studies on Size Dependent Structures and Optical Properties of CdSeS Clusters

The size-dependent structures and optical properties of CdSeS nanoclusters in water medium are investigated. The stability of different size-dependent CdnSemSp nanoclusters (up to n = 6) is studied using density functional theory/time-dependent density functional theory (DFT/TDDFT). The computed results for ground (S0) and excited (S1, S2, S3) states are experimentally verified through UV–Vis spectroscopy. Computed ab initio results suggest that CdSeS clusters are significantly more hyperpolarizable compared to CdX (X = S, Se, Te) clusters. Structure dependent response properties are also observed, especially for n ≥ 3. Larger hyperpolarizabilities (β and γ), charge variation and orbital analysis establish Cd4SemSp clusters, as nonlinear optically active quantum dots (QDs).

A fluorescein-carbazole-based fluorescent probe for imaging of endogenous hypochlorite in living cells and zebrafish

In this article, a fluorescent probe FCZ with fluorescein-carbazole as the basic skeleton was designed and synthesized. In contrast to the presences of other coexisting anions, active oxygen and organic thiols, the probe could be "turn-on", exhibiting specific fluorescence performance towards hypochlorite (ClO-). Comprehensive analyses by electrospray ionization mass spectrometry (ESI-MS), thin-layer chromatography (TLC), nuclear magnetic resonance (NMR), and density functional theory/time-dependent density functional theory (DFT/TDDFT) revealed that ClO- could react with the imine bond of the probe, forming fluorescein, resulting in a significant increase of fluorescence emission intensity. The probe has a detection limit for ClO- in water of 0.056 μmol/L. In addition, the probe was successfully applied to detect ClO- in water samples, as well as in the imaging of ClO- in RAW264.7 cells and zebrafish.

The Simplest Possible Approach for Simulating S0- S1 Conical Intersections with DFT/TDDFT: Adding One Doubly Excited Configuration.

A simple combination of density functional theory/time-dependent density functional theory (DFT/TDDFT) and configuration interaction is presented to fix the incorrect topology of the S0- S1 conical intersection (CI) and allow a description of bond making and bond breaking in photoinduced dynamics. The proposed TDDFT-1D method includes one lone optimized doubly excited configuration in addition to the DFT/TDDFT singly excited states within the context of a large configuration interaction Hamiltonian. Results for ethylene and stilbene are provided to demonstrate that this ansatz can yield physically meaningful potential energy surfaces near S0- S1 avoided crossings without changing the vertical excitation energies far from the relevant crossings. We also investigate the famous linear water example to show that the algorithm calculates the correct topology of the S0- S1 CI and yields the correct geometric phase.

Theoretical insight into the photophysical properties of five phosphorescent heteroleptic iridium(iii) complexes bearing oxadiazol-substituted amide ligands.

A DFT/TDDFT (density functional theory/time-dependent density functional theory) investigation on the geometries in the ground and lowest triplet excited states, the frontier molecular orbitals, the absorption spectra and the phosphorescent emission properties of five heteroleptic iridium(iii) complexes have been performed to obtain a better understanding of structure-property relationships. The key aim was to investigate the effect of π-conjugation on the photophysical properties of these studied complexes. The lowest energy absorption wavelengths are located at 461 nm for 1, 418 nm for 2, 422 nm for 3, 426 nm for 4 and 417 nm for 5. The lowest energy emissions of complexes 1-5 are localized at 572, 463, 583, 707 and 553 nm, respectively, simulated in acetonitrile medium at M052X level. These findings could be useful to provide good guidance for the further design of new potential phosphorescent organic light-emitting diode (OLED) materials.

Synthesis, characterization, and DFT study of novel metallo phtalocyanines with four carboranyl clusters as photosensitisers for the photodynamic therapy of breast cancer cells

The synthesis and characterization of novel Zn(II) and Co(II) phthalocyanines 4 and 5, respectively containing four o-carboranyl units (40 boron atoms, 32.5% boron by weight) at the peripheral positions are described. The phthalocyanines (Pcs) were synthesized by cyclotetramerization of the previously prepared precursor 4‑(2‑thiol‑o‑carboranyl)thiolato‑phthalonitrile 3 with the presence of metal salt in boiling dry DMF under a dry nitrogen atmosphere. They were characterized by elemental analysis, UV–Vis, FT-IR, MALDI-TOF mass and 1H NMR spectrometry. To elucidate the structural, spectroscopic and bonding properties of the obtained compounds, calculations with DFT/TD-DFT(Density Functional Theory/Time Dependent-Density Functional Theory) were performed. The cytotoxic effects of 4 and 5 on cancer cells and epithelial cells were determined. The targeted cytotoxicities of both compounds against cancer cells were analyzed with the cell viability test. Although, 4 caused less PDT (Photodynamic therapy) based decrease in cell viability of cancer cell line in comparison to 5, it showed comparatively high cytotoxicity against cancer cells but not epithelial cells. The IC50 (half maximal inhibitory concentration) values indicate that 4 with PDT shows 17.3 fold more cytotoxicity to breast cancer cells than epithelial cells. The selectivity in cytotoxicity of 4 makes it a good candidate for cancer treatment. Interestingly, 5 was found to be highly cytotoxic for both cancer and epithelial cell lines. Considerably, 5 might be used as a cancer drug when combined with targeting agents such as antibodies and aptamers.

Phosphorescent Modulation of Metallophilic Clusters and Recognition of Solvents through a Flexible Host-Guest Assembly: A Theoretical Investigation.

MP2 (Second order approximation of Møller–Plesset perturbation theory) and DFT/TD-DFT (Density functional theory/Time-dependent_density_functional_theory) investigations have been performed on metallophilic nanomaterials of host clusters [Au(NHC)2]+⋅⋅⋅[M(CN)2]−⋅⋅⋅[Au(NHC)2]+ (NHC = N-heterocyclic carbene, M = Au, Ag) with high phosphorescence. The phosphorescence quantum yield order of clusters in the experiments was evidenced by their order of μS1/ΔES1−T1 values (: S0 → S1 transition dipole, : splitting energy between the lowest-lying singlet S1 and the triplet excited state T1 states). The systematic variation of the guest solvents (S1: CH3OH, S2: CH3CH2OH, S3: H2O) are employed not only to illuminate their effect on the metallophilic interaction and phosphorescence but also as the probes to investigate the recognized capacity of the hosts. The simulations revealed that the metallophilic interactions are mainly electrostatic and the guests can subtly modulate the geometries, especially metallophilic Au⋅⋅⋅M distances of the hosts through mutual hydrogen bond interactions. The phosphorescence spectra of hosts are predicted to be blue-shifted under polar solvent and the excitation from HOMO (highest occupied molecular orbital) to LUMO (lowest unoccupied molecular orbital) was found to be responsible for the 3MLCT (triplet metal-to-ligand charge transfer) characters in the hosts and host-guest complexes. The results of investigation can be introduced as the clues for the design of promising blue-emitting phosphorescent and functional materials.

Theoretical perspective on electronic structure and photophysical properties for three cyclometalated iridium(III) complexes bearing different substituent groups on the main ligands

To investigate the influence of the different substituents in the main ligands on the electronic structures, phosphorescent properties, and organic light-emitting devices (OLEDs) performance, three iridium(III) complexes 1, 2, and 3 are studied by means of the density functional theory/time-dependent density functional theory (DFT/TDDFT). Ionization potential, electron affinities, and reorganization energy have also been obtained to evaluate the charge transfer and balance properties between hole and electron for the three complexes. The lowest energy absorption wavelength calculated for complex 1 is in very good agreement with the experimental value. The lowest energy emissions of complexes 1, 2, and 3 are localised at 492, 565, and 510 nm, respectively, at M052X level. It is expected that this work might provide a way to develop potential iridium(III) phosphors with good electroluminescent performance.