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Synthesis and photochromic properties of some N-phthalimide azo-azomethine dyes. A DFT quantum mechanical calculations on imine-enamine tautomerism and trans-cis photoisomerization
摘要： This paper presents synthesis, photophysical characterization and quantum mechanical calculations of some N-phthalimide azo-azomethine dyes. The dyes were synthesized via azo coupling reaction between 2,4-substituted aromatic anilines and salicylic aldehyde followed by condensation reactions between azo dyes and N-aminophtalimide. Quantum chemical calculations to optimise the molecular geometry and to determine the electron densities of the trans (E) imine ? enamine and the cis (Z) imine ? enamine isomers and their vibrational frequencies have been computed by using DFT at B3LYP/6–31 + G(d,p) level of theory in vacuo. The effect of the used DMF solvent on the molecular structure and bond energies has been determined by using the IEFPCM model. Thermodynamic parameters such as total electronic energy E(RB3LYP), enthalpy H298 (sum of electronic and thermal enthalpies), free Gibbs energy G298 (sum of electronic and thermal free Gibbs energies) and dipole moment μ were computed in order to estimate the ΔE, Δμ, ΔH, ΔG and ΔS values. The NBO analysis was performed in order to understand the intramolecular charge transfer and the energy of resonance stabilization. After molecular geometry optimization, the electronic spectra were obtained by TD-DFT calculations at the above mentioned basis set using the IEFPCM model of DMF as a solvent. The solvatochromic effect of the dyes in four solvents with different polarity has been studied by UV–VIS spectroscopy and compared with the theoretically predicted. The coincidence between measured and calculated spectra is satisfactory. The dynamic photoisomerization experiments were performed in DMF under irradiation with UV light at λ = 365 nm (mostly E → Z) and with VIS light at λ = 400–800 nm (mostly Z → E). The spectra were recorded in the spectral region from 300 to 800 nm at identical sample concentrations of the three dyes and illumination times in order to investigate the photodynamical E → Z → E conversion of the\N_N\chromophore group of the dyes as well as the imine ? enamine tautomerization.
关键词： Tautomerism,DFT calculations,Schiff bases,Azo-azomethine dyes,Photochromism,Trans-cis photoisomerization
更新于2025-09-23 15:21:01
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Adsorption for SO2 gas molecules on B, N, P and Al doped MoS2: the DFT study
摘要： In this paper, we investigated SO2 adsorption on B, N, P and Al doped MoS2, which band structure, density of states, charge transfer, etc by the density function theory (DFT) calculation. Results show that the SO2 prefer to be absorbed at the top of Mo atom of MoS2. It is found that SO2 is strongly adsorbed on Al-MoS2 with considerable adsorption energy of -1–-2.33eV, however, the best adsorption position is the top of Mo atom of Al-MoS2, which the biggest Ea is -2.33eV, the best charge is -0.343e and the shortest d is 1.763?. So these findings confirm that Al-MoS2 can be used to detect the presence of SO2 in the environment.
关键词： SO2 adsorption,MoS2,Al-MoS2,doped MoS2,DFT study
更新于2025-09-23 15:21:01
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Impact of electronically excited state hydrogen bonding on luminescent covalent organic framework: a TD-DFT investigation
摘要： The investigation of intermolecular hydrogen bonding between the luminescent polypyrene covalent organic framework and formaldehyde (PPy-COF-HCHO) was carried out with the density functional theory and time-dependent density functional theory. The strengthening of the photoexcited hydrogen bond C = O—H–C was verified via geometric structures, electronic transition energies, binding energies, UV-Vis and infrared spectra comparison in both ground state and excited state of the PPy-COF’s truncated representative fragment. From the frontier molecular orbitals examination, natural population analysis, and plotted electron density difference map demonstrated that the strengthened hydrogen bond facilitated the rearrangement of electron density between H-donor and H-acceptor moieties which should account for charge transfer and ultimate fluorescence quenching. Interestingly, the energy gap between excited state and triplet state of the hydrogen-bonded complex showed the possibility of the intersystem crossing. The MOMAP programme further confirmed the quenching process because there was a lower fluorescent rate constant for the donor–acceptor PPy-COF-HCHO complex compared to free PPy-COF fragment. Results above significantly highlighted the high sensitivity of the PPy-COF towards organic analyte, i.e. the formaldehyde and can be employed as a sensor.
关键词： luminescence,TD-DFT,MOMAP,hydrogen bonding
更新于2025-09-23 15:21:01
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Photophysical properties and theoretical investigations of newly synthesized pyrene-naphthalene based Schiff base ligand and its copper(II) complexes
摘要： The present work describes the synthesis and characterization of a novel pyrene-naphthalene based Schiff base ligand and its copper complexes. The ligand was synthesized by reacting 1-Pyrenecarboxaldehyde and 1,8-Diaminonaphthalene in 2:1 molar ratio. The resulting Schiff base ligand, (N1E,N8E)-N1,N8-bis(pyren-1-ylmethylene)naphthalene-1,8-diamine (BPND) was characterized by NMR (1H and 13C), FT-IR and ESI-HRMS techniques. Further, BPND was used to synthesize two Cu(II) complexes (1 and 2) in 2:1 (ligand:metal) and 1:1:1 (ligand:metal:8-hyroxyquinoline) molar ratio, and characterized using electronic absorption, fluorescence spectroscopy, in addition to aforementioned spectroscopic techniques. DFT calculations have been used in order to obtain information on quantum-molecular descriptors reflecting the local reactivity properties. DFT calculations encompassed geometrical optimizations of title molecules and calculations of molecular electrostatic potential (MEP), average local ionization energies (ALIE) and atomic Fukui indices.
关键词： DFT,Fukui indices.,Cu(II) complex,Pyrene-naphthalene ligand,Spectroscopic characterization
更新于2025-09-23 15:21:01
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Crystal structure, vibrational spectra, optical properties and density functional theory approach of a picrate salt based on substituted triphenylphosphinium
摘要： A new organic crystal, [BzTPP][PIC](1) ([BzTPP]+ = benzyl triphenylphosphinium, [PIC]- = picrate), has been grown by slow evaporation solution growth technique. Single crystal XRD reveals that it belongs to monoclinic system with P21/c. The two neighboring [BzTPP]+ cations from a dimer through C-H···π interaction while anions stack into a columnar structure through N···O, O···O and π···π interaction. The anions and cations form a column structure alternately in ···AC-AC-AC-AC··· sequence through C-H···O hydrogen bonds. The experimental vibrational bands (IR and Raman) have been discussed and assigned based on DFT calculations. The HOMO-LUMO energy gap explains the charge transfer interactions in the molecule. The thermal stability of the hybrid crystal was analyzed by TG-TDA-MS technique and revealed that the title crystal was stable up to 290 °C. The fluorescence spectra reveal three main emission peaks at 295, 388 and 543 nm upon excitation at 250 nm in solid state at room temperature. The energy of weak interactions in the molecule and nonlinear optical properties were studies using DFT calculations.
关键词： Substituted benzyl triphenylphosphinium picrate,Optical properties,vibrational spectra,Crystal structure,DFT calculations
更新于2025-09-23 15:21:01
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Predicted bandgap opening in highly-oriented wrinkles formed in chemical vapour deposition grown graphene
摘要： We present a combined atomic force microscopy and Raman spectroscopy study of wrinkle formation in chemical vapour deposition graphene. Graphene was grown on copper and repeatedly transferred onto a SiO2 substrate to form a four-layer graphene stack. By means of depositing two electrodes with a small gap of 1μm on top of graphene, we can generate a long wrinkle along the channel. Such a wrinkle is pronounced and seems to form at the expense of other wrinkles otherwise present. Along the wrinkle, the strain measured by both atomic force microscopy and polarized Raman is revealed to be of a biaxial type, which is shown, through atomistic modelling, is predicted to produce a sizeable bandgap opening of up to 0.4 eV. Since graphene is normally a zero bandgap material, its applications as an electronic material for devices can be limited. The approach presented in this work could lead to graphene exhibiting a controllable bandgap similar to a semiconductor material that could, therefore, be exploited for the fabrication of graphene-based electronic devices.
关键词： DFT,AFM,Raman spectroscopy
更新于2025-09-23 15:21:01
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by angle-resolved photoelectron spectroscopy, scanning tunneling spectroscopy, and density functional theory
摘要： The electronic structure of 1T -TaS2 showing a metal-insulator transition and a sequence of different charge density wave (CDW) transformations was discussed in the frame of variable temperature angle-resolved photoelectron spectroscopy (ARPES), scanning tunneling spectroscopy (STS), and density functional theory (DFT) calculations. For the commensurate charge density wave phase (CCDW) the Mott gap was estimated to be 0.4 eV and energy gaps (cid:2)CCDW,1, (cid:2)CCDW,2, (cid:2)B3-HHB, (cid:2)B4-B3 were observed. For the nearly commensurate charge density wave phase (NCCDW), the reminiscent of higher and lower Hubbard bands and a very pronounced electronic state associated with the parabolic band at the ˉ(cid:3) point in the Brillouin zone were identi?ed. The incommensurate charge density wave phase (ICCDW) showed a high value of local density of states at the Fermi level and a very pronounced edge of the metallic surface state located in the range of 0.15–0.20 eV above the Fermi level. The obtained STS and ARPES results were consistent with our theoretical calculations performed within DFT formalism including spin-orbit coupling.
关键词： STS,1T -TaS2,charge density wave,ARPES,DFT,metal-insulator transition
更新于2025-09-23 15:21:01
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Study the electronic properties and magnetization of rutile polymorph CoxTi1-xO2 super cell at various cobalt (Co) concentrations using first principle calculation
摘要： First principle calculation has been performed to study the electronic properties and magnetization of CoxTi1-xO2 at different cobalt concentration. Equilibrium lattice constant of CoxTi1-xO2 at 0.0% cobalt concentration was obtained about 4.81?. The obtained value is slightly larger than the experimental value. The calculated band gap of CoxTi1-xO2 at 0.0% cobalt concentration is 3.0 eV which consistent with other reports. The calculated band gap for 16.6% is 0.5 eV, for 33.3% is 0.1 eV and for 50.0% is approximately 0.0 eV. The calculated band gap of CoxTi1-xO2 decreased with increased cobalt concentration. On the other hand at 0.0% cobalt concentration, the magnetization is zero and at 50.0% cobalt concentration, magnetization is 3.36 Bohr mag/cell. The density of states calculation for spins up and spins down are symmetric at 16.6% and 33.3% cobalt concentration. At 50.0% cobalt concentration the density of states shows asymmetric for spin up and spin down which indicates the ferromagnetic nature.
关键词： Band structure,Magnetization,Equilibrium lattice constant,Density function theory (DFT),Density of State (DOS)
更新于2025-09-23 15:21:01
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Enhancing interfacial charge transfer on novel 3D/1D multidimensional MoS2/TiO2 heterojunction toward efficient photoelectrocatalytic removal of levofloxacin
摘要： Structure-controlled visible light driven photo-anode with high catalytic performance, plays important roles in environmental pollutants treatment. In this work, a mild hydrothermal assisted anodization approach has been reported to design an integrated self-assembled 3D flower-like MoS2/1D TiO2 nanotube arrays (NTAs) hierarchical electrode. The constructed multidimensional electrode not only broadened the absorption spectrum response range but also promoted rapidly electron-hole pairs separation, exhibiting the excellent photoelectron catalytic (PEC) performance and stability in the degradation of target pollutants, which the photocurrent conversion efficiency was 6.5 times higher than that of pure TiO2. Furtherly, a comprehensive mechanism was proposed to explain the charge transfer on the interface of intimate integration of 3D/1D hybrid nanostructure towards PEC properties in terms of the energy band structures and DFT. Furthermore, the photo-generated active species (?OH and ?O2-) have been proved by electron paramagnetic resonance spectroscopy and fluorescence probe over the composites. Thus, this work could provide an effective strategy to design multidimensional coupled heterojunction materials toward solar energy conversion for environmental purification.
关键词： Interfacial charge transfer,Photoelectrocatalytic,Active radicals,DFT,3D/1D hybrid nanostructures
更新于2025-09-23 15:21:01
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Thina??Film Morphology Improvement and Density Functional Theorya??Driven Findings for the Photovoltaic Perovskite MAPI/MAPSI
摘要： The morphology of thin films of the mixed MAPI / MAPSI material has been studied, revealing that the addition of toluene in the synthesis stage markedly improves the porosity problem of the manufactured films. The presence of crystalline domains of the two materials is verified, as reported by the X-ray diffraction patterns. The calculated band gap values from the diffuse reflectance measurements using the Tauc plots with the Kubelka-Munk transformation function confirm the presence of the two materials in the mixture. On the other hand, the results of the DFT-based computational calculations give answers to the true geometry that the SCN groups adopt within the MAPSI unit cell. The COHP analysis suggests that the most stable structure has an axial geometry for the SCN groups, which is confirmed by the analysis of non-covalent interactions (NCI), in which it is established that there is a greater number of hydrogen bond interactions for the same axial configuration, and results for Electron Localization Functions were shown (ELF), where it is found that there is indeed electron localization (at the level at which a bonding interaction is expected, ELF > 0.8) both for the SCN groups and the methyl-ammonium cations, in the same way as seen in the results of the NCI analyses.
关键词： hybrid perovskites,solar cells,thin films,SEM,DFT calculations
更新于2025-09-23 15:19:57