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Applications of Molecular Spectroscopy to Current Research in the Chemical and Biological Sciences || Geometric and Electronic Properties of Porphyrin and its Derivatives
摘要： In this chapter, we discuss protonation and substitution effects on the absorption spectra of porphyrin molecules based on density functional theory (DFT) and time-dependent DFT calculations. The results of the calculations are compared with experimental data. The calculations show that protonation of core nitrogen atoms of porphyrin and meso-substituted porphyrins produces a substantial shift in Soret and Q-absorption bands, relative to their positions in corresponding nonprotonated and nonsubstituted chromophores. A relaxed potential energy surface (RPES) scan has been utilized to calculate ground and excited state potential energy surface (PES) curves as functions of the rotation of one of the meso-substituted sulfonatophenyl groups about dihedral angles θ (corresponding to Cα─Cm─C?─C) ranging from 40 to 130°, using 10° increments. The ground state RPES curve indicates that when the molecule transitions from the lowest ground state to a local state, the calculated highest potential energy barrier at the dihedral angle of 90° is only 177 cm?1. This finding suggests that the meso-sulfonatophenyl substitution groups are able to rotate around Cm─C? bond at room temperature because the thermal energy (kBT) at 298 K is 207.2 cm?1. Furthermore, the calculations show that the geometric structure of the porphyrin is strongly dependent on protonation and the nature of the meso-substituted functional groups.
关键词： DFT calculation,protonation,PES,porphyrins,absorption
更新于2025-09-23 15:21:21
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A Density Functional Theory Study on Nonlinear Optical Properties of Double Cage Excess Electron Compounds: Theoretically Design M[Cu(Ag)@(NH <sub/>3</sub> ) <sub/><i>n</i> </sub> ](M?=?Be, Mg and Ca; <i>n</i> ?=?1-3)
摘要： In this work, we investigated the nonlinear optical (NLO) properties of excess electron electride molecules of M[Cu(Ag)@(NH3)n] (M = Be, Mg and Ca; n = 1–3) using density functional theory (DFT). This electride molecules consist of an alkaline-earth (Be, Mg and Ca) together with transition metal (Cu and Ag) doped in NH3 cluster. The natural population analysis of charge and their highest occupied molecular orbital suggests that the M[Cu(Ag)@(NH3)n] compound has excess electron like alkaline-earth metal form double cage electrides molecules, which exhibit a large static ?rst hyperpolarizability (βe0) and one of which owns a peak value of βe0 216,938 (a.u.) for Be[Ag@(NH3)2] and vibrational harmonic ?rst hyperpolarizability.
关键词： NLO,transition metal,alkaline-earth,DFT,double cage excess electron compounds
更新于2025-09-23 15:21:21
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Exploring the potential of iron to replace ruthenium in photosensitizers: a computational study
摘要： In an effort to replace the widely used ruthenium metal complexes with low-cost, earth abundant iron complexes as photosensitizers for dye-sensitized solar cell (DSSC) applications, herein we report the computational design of heteroleptic iron complexes (FC1–3) coordinated with benzimidazole-phenylcarbene (C^N) ligands. DFT and TDDFT calculations predicted the stronger σ-donating and π-accepting nature of phenyl carbene ligands substituted with electron-withdrawing CF3, donating –N(CH3)2, and benzothiazine annulation than the imidazole carbene ligands (FC4); consequently, the metal-ligand bond distances and interactions that influence the ordering of charge transfer states with respect to metal centered states are altered in FC1–3 complexes. Detailed analysis based on energy decomposition analysis, spin density distribution analysis, and ab initio ligand field theory parameters were enabled to understand the nature of heteroleptic ligand interactions with the rest of the metal complex. The results from the study shed light on the judicious choice of ligands, as the same non-innocent ligand that is experimentally proven as favorable for Ru-dyes (TC1) is found to be detrimental for Fe-dyes (FC1). Among the complexes studied, the FC3 complex is a promising sensitizer for DSSC with 1,3MLCT energy level well separated from 3,5MC, thereby preventing the deactivation of MLCT. The outcome of the study is therefore an important step toward the development of photosensitizers based on iron metal.
关键词： DSSC,Photosensitizers,Iron,Spin states,TD-DFT,Carbene ligands,Ruthenium
更新于2025-09-23 15:21:21
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Quantum chemical investigation of modified coumarin-based organic efficient sensitizers for optoelectronic applications
摘要： One of the most major features in the improvement of dye-sensitized solar cells (DSSCs) is the survey and plan of high-efficiency and low-cost dyes. In this paper, a new series of metal-free coumarin-based (NKX-2311) dye molecules, namely (D1–D4) are investigated for use in DSSC applications. The dye molecules contain three parts, electron-donor (D) connected by the π-conjugated linker as a spacer and electron-acceptor (A)/anchoring group. Molecular structure, electronic absorption spectra and photovoltaic (PV) parameters of the D1–D4 dyes have been performed by using density functional theory (DFT) and time-dependent DFT (TD-DFT) approaches are employed. The effects of chemical modification on the spectra and PV properties of the coumarin-modified organic dyes have been revealed. The performance of three functionals (B3LYP, CAM-B3LYP and ωB97XD) has been evaluated to get an experimental absorption wavelength of NKX-2311. From the functionals, B3LYP method was better matched with the absorption wavelength of NKX-2311. Therefore, D1–D4 dye molecules excited state calculations of the absorption spectra have been investigated by using B3LYP functional with 6-31G(d) basis set. The results show that D1, D3 dyes are smaller energy gap and absorption spectra are systematically red-shifts. The theoretical results have a display that the lowest occupied molecular orbitals (LUMOs) and highest occupied molecular orbitals (HOMOs) of the D1–D4 dyes can be confirming positive response on the electron injection and dye regeneration process. The NLO property of the D1–D4 dyes can be derived as polarizability and first-order hyperpolarizability. The calculated values of D1 and D3 dyes are the best applicants for NLO performance. The conclusion of this study will deliver a useful reference to the future proposal and beneficial to get DSSCs with superior power conversion efficiency (PCE).
关键词： TD-DFT,coumarin-based dyes,DSSCs,NLO properties,DFT,photovoltaic properties
更新于2025-09-23 15:21:01
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Theoretical modifications of the molecular structure of Aurantinidin and Betanidin dyes to improve their efficiency as dye-sensitized solar cells
摘要： Two modifications of the molecular structures of Aurantinidin and Betanidin dyes were modeled, and the optical and electrical properties were calculated by using density functional theory (DFT) and time-dependent DFT (TD–DFT). The modification of the structures was done by connecting the units through vinyl groups and using regular electron acceptor and electron donor moieties to the original structures. It has been demonstrated that the modifications improved the electron injection properties of the molecules with higher light-harvesting efficiencies, an increase in the driving force of electron injection ( ΔG inject ) and open-circuit photovoltages ( V OC ).
关键词： DSSC,DFT,Frontier molecular orbitals,Electron injection,TD–DFT
更新于2025-09-23 15:21:01
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Improving the heterointerface in hybrid <scp>organica??inorganic</scp> perovskite solar cells by surface engineering: Insights from periodic hybrid density functional theory calculations
摘要： A periodic hybrid density functional theory computational strategy is presented to model the heterointerface between the methylammonium lead iodide (MAPI) perovskite and titanium dioxide (TiO2), as found in perovskite solar cells (PSC), where the 4-chlorobenzoic acid (CBA) ligand is used to improve the stability and the band alignment at the interface. The CBA ligand acts as a bifunctional linker to efficiently connect the perovskite and the oxide moieties, ensuring the stability of the interface through Ti–O and Pb–Cl interactions. The computed density of states reveals that the perovskite contributes to the top of the valence band while the oxide contributes to the bottom of the conduction band with a direct bandgap of 2.16 eV, indicating a possible electron transfer from MAPI to TiO2. Dipole moment analysis additionally reveals that the CBA ligand can induce a favorable effect to improve band alignment and thus electron transfer from MAPI to TiO2. This latter has been quantified by calculation of the spin density of the reduced MAPI/CBA/TiO2 system and indicates an almost quantitative (99.94%) electron transfer from MAPI to TiO2 for the surface engineered system, together with an ultrafast electron injection time in the femtosecond timescale. Overall, the proposed DFT-based computational protocol therefore indicates that surface engineering and the use of a bifunctional linker can lead to a better stability, together with improved band alignment and electron injection in PSC systems.
关键词： DFT,perovskite solar cells,interface
更新于2025-09-23 15:21:01
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Enhancement in Photovoltaic Properties of <i>N</i> , <i>N</i> a??diethylaniline based Donor Materials by Bridging Core Modifications for Efficient Solar Cells
摘要： The increasing demand of energy expedited the development of efficient photovoltaic materials.Herein, five push-pull donor materials (D1-D5) having N,N-diethylaniline as donor moiety and rhodanine-3-acetic as acceptor group are designed to be used as donor molecules in organic solar cells (OSCs). The bridging core modification of recently synthesized MR3 molecule (reference R) has been made with different π-spacers namely thiazole (B1), thieno[3,2-b]thiophene (B2), thiazolo[5,4-d] thiazole (B3), 2-(thiophen-2-yl)thiophene (B4) and 5-(thiazol-5yl)thiazole (B5). The structure–property relationship is studied and influence of bridging core modifications on photovoltaic, photophysical and electronic properties of D1-D5 are calculated and compared with reference R.The DFT and TDDFT calculations have been performed for the estimation of frontier molecular orbital (FMO) analysis, density of states (DOS) graphs, reorganization energies of electron and hole, open circuit voltage, photophysical characteristics, transition density matrix (TDM) surfaces and charge transfer analysis.Designed molecules exhibit better and comparable optoelectronic properties than synthesized reference molecules. Among all investigated molecules, D5 is proven as best candidate for OSCs application due to its promising photovoltaic properties including lowest band gap (2.24 eV), small electron mobility (λe = 0.0056 eV), small hole mobility (λh = 0.0046 eV), low binding energy (Eb = 0.21 eV), highest λmax values 610.76 nm (in gas) 670.22 nm (in acetonitrile) and high open circuit voltage (Voc = 1.17 V) with respect to HOMOdonor–LUMOPC61BM. This theoretical framework demonstrates that bridging core modification is a simple and effective alternative strategy to achieve the desirable optoelectronic properties. Furthermore, conceptualized molecules are superior and thus are recommended to experimentalist for out-looking future developments of highly efficient solar cells.
关键词： Rhodanine-3-acetic acid,Solar cells,Photovoltaic properties,Bridging core modifications,Density functional theory (DFT),N,N-diethylaniline
更新于2025-09-23 15:21:01
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Interfacial and Bulk Properties of Hole Transporting Materials in Perovskite Solar Cells: Spiro-MeTAD versus Spiro-OMeTAD
摘要： Two spiro-MeTAD compounds (1 and 2) were synthesized, characterized by experimental and quantum mechanical methods, and used as hole transporting materials (HTMs) in perovskite solar cells (PSC). The new compounds differ from spiro-OMeTAD only by the presence of methyl substituents as compared to methoxy groups. This modification results in absorption-band blue shift by ~20 nm as compared to spiro-OMeTAD, increased glass transition temperature for 2, and reduced ionization potentials by 0.02-0.12 eV. Hole mobilities larger by five times were obtained for spiro-MeTAD /spiro-MeTAD, which is maintained in the presence of additives. Despite this improvement, J-V measurements in PSCs resulted in power conversion efficiency (PCE) of 17.2% and 17.05% for 1 and 2 HTMs, respectively, as compared to 19.24?% for spiro‐OMeTAD. Photoluminescence measurements of perovskite:HTM layers indicate much stronger quenching in the case of spiro-OMeTAD/spiro-MeTAD. These results point to the dominant importance of the perovskite/HTM interfacial properties as compared to HTM hole-transport properties in the bulk. Given that improved hole-mobility and energy-level alignment are the main targets of the current research efforts in this domain, our results alert on the necessity to give priority to improving perovskite-HTM interaction properties.
关键词： dft,perovskites,energy disorder,solar cells,interaction energy,interfaces
更新于2025-09-23 15:21:01
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First Member of an Appealing Class of Cyclometalated 1,3-Di-(2-Pyridyl)Benzene Platinum(II) Complexes for Solution-Processable OLEDs
摘要： The preparation and characterization of a new platinum(II) complex bearing a N^C^N-cyclometalating ligand and a thiolate coligand, namely 5-mesityl-1,3-di-(2-pyridyl)benzene and 1-phenyl-1H-tetrazole-5-thiolate, is reported. Its structure is determined by X-ray diffraction studies on a single crystal. This new complex exhibits green and red phosphorescence in dichloromethane solution (Φlum = 0.90) and in the solid state (Φlum = 0.62), respectively. In both cases the quantum yield is impressive showing for the first time that N^C^N platinum(II) complexes with a suitable thiolate can reach outstanding luminescent properties. The excellent solubility of this complex allows to fabricate green processable solution-OLEDs with maximum EQE similar to that obtained with more expensive vacuum techniques and, depending on its concentration, one can tune the color of the OLED. The molecular geometry, ground state, electronic structure, and excited electronic states of the complex, both as monomer and dimer aggregate in solution, are calculated by density functional theory (DFT) and time-dependent DFT approaches, giving insight into the electronic origin of the absorption spectra. Remarkably, the dimer is less sensitive to oxygen quenching than the monomer because the two 1-phenyl-1H-tetrazole fragments protect the platinum(II) centers, as suggested by a combination of luminescence studies and theoretical calculations.
关键词： thiolate ligand,DFT,luminescence,platinum(II) complex,OLED
更新于2025-09-23 15:21:01
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Theoretical Studies into the Spectral Characteristics, Biological Activity, and Photovoltaic Cell Efficiency of Four New Polycyclic Aromatic Chalcones
摘要： In the present work, (E)-1-(4,400-difluoro-50-methoxy-1,10:30,100-terphenyl-40-yl)-3-phenylprop-2-en-1-one (DFTP), (2E)-1-(4,400-difluoro-50-methoxy-1,10:30,100-terphenyl-40-yl)-3-(4-fluorophenyl)prop-2-en-1-one (TFTP), (2E)-3-(4-bromophenyl)-1-(4,400-difluoro-50-methoxy-1,10:30,100-terphenyl-40-yl)-prop-2-en-1-one (BFTP), and (E)-1-1(4,400-difluoro-50-methoxy-1,10:30-100-terphenyl-40-yl)-3-(4-methylphenyl)prop-2-en-1-one (FMTP) have been synthesized and vibrational wavenumbers and electronic properties have also been performed. The compound series shows good light harvesting properties and photovoltaic modeling shows that they can be used successfully in DSSCs as photo sensitizers. The NLO activity of the title compounds have been investigated and b and c values varies in the order BFTP > FMTP > TFTP > DFTP. The consequences which were made by electron donor acceptor due to charge transfer mechanism have been scrutinized by the natural bond investigation. Molecular docking has been performed to understand the binding interactions of the analyzed ligands with tyrosine-protein kinase JAK2 and these compounds can be developed as anticancer agent.
关键词： terphenyl,DSSC,DFT,MEP,docking,FT-IR
更新于2025-09-23 15:21:01