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Spectroscopic behavior, FMO, NLO and NBO analysis of two novel aryl boronic acid derivatives: Experimental and theoretical insights
摘要： Here we report, experimental and theoretical determination of ground and excited state dipole moments of aryl boronic acid derivatives, 2-Bromophenyl boronic acid (2BPBA) and 2-Isopropylphenyl boronic acid (2IPBA). In both the compounds, Bathochromicshift is observed with increasing solvent polarity indicating π →π* transition due to intermolecular charge transfer interactions. For both the compounds, the ground and excited sate dipole moments are parallel to each other. The excited state dipole moment (μe) is greater than ground state dipole moment (μg) for the compound 2IPBA where as for 2BPBA, excited state dipole moment (μe) is less than ground state dipole moment (μg). Further, experimentally obtained Δμ are compared with those using microscopic empirical solvent polarity (??????). In parallel, the use of Kamlet-Taft parameters to the solvent effect on spectral properties of 2BPBA and 2IPBA are also discussed. The molecular structure, Frontier Molecular Orbitals (FMO), Natural Bond Orbital (NBO) analysis, Non-Linear Optical (NLO) properties of 2BPBA and 2IPBA have been investigated using the (DFT) calculations with B3LYP/6?311++G (d, p) basis set. The chemical reactivity and kinetic stability of the compounds is shown by differences between the energy levels by analyses of Frontier molecular orbitals. The polarizability and hyperpolarizability computations determine the NLO properties, whereas Natural bond orbital (NBO) analysis showed proton transfer within the selected donor-acceptor depicting large energy of stabilization for the compounds under study.
关键词： Kamlet-Taft,FMO,MEP,ground and excited state dipole moments,Solvatochromic shift method,NBO and NLO
更新于2025-09-23 15:23:52
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Exploring the spectral features and quantum chemical computations of a novel biologically active heterocyclic class of compound 2MEFPBA dye: Experimental and theoretical approach
摘要： Here we report, experimental and theoretical determination of ground and excited state dipole moments of the class of heterocyclic compound namely 2-Methoxy-5-fluoro phenyl boronic acid (2MEFPBA) dye. Bathochromic shift with increasing solvent polarity is observed indicating π →π* transition due to intermolecular charge transfer interactions. The ground and excited state dipole moments are found to be parallel to each other. The molecular structure, Frontier molecular orbital (FMO), Natural bond orbital (NBO) analysis and Nonlinear optical (NLO) properties of 2MEFPBA have been investigated using the Density Functional Theory with B3LYP/6?31 ++ g(d, p) basis set. Chemical reactivity and kinetic stability of 2MEFPBA are analyzed using F M O energy. Polarizability and hyperpolarizability computations are used to determine the NLO properties, whereas Natural bond orbital (NBO) analysis showed the proton transfer within the selected donor-acceptor depicting large energy of stabilization for the compound under study.
关键词： MEP,NBO,FMO,Solvatochromic ground and excited state dipole moments,and NLO.
更新于2025-09-23 15:22:29
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Photo-Annealing of Merocyanine Aggregates
摘要： In this work we elucidate the fundamental difference between aggregate formation of donor-π-acceptor merocyanines in their electronic ground and excited states. While increasing the π-bridge size favors formation of π-stacked aggregates in the dark, irradiation with visible light causes reorientation of the dyes to form prototype H-aggregates with compensating dipole moments. This photo-annealing changes the supramolecular structure and its UV-vis spectroscopic properties dramatically, thus being of importance for the function of active layers composed of these dyes. Aggregates of the ground state dyes are bound cooperatively through ππ-London dispersion interactions and hydrogen bonds between the polar α-cyano-carboxylic acid groups. However, charge transfer upon photoexcitation leads to repulsion of the polar acid groups. Electronic excitation of the dyes approximately doubles the ground state dipole moment, thus driving molecular reorientation into prototype H-aggregate structures. We show that this photo-induced supramolecular rearrangement can disrupt the large polymeric aggregates formed in the dark. The photo-induced supramolecular structural changes reported in this work will influence the performance of optoelectronic devices composed of these structures and must be controlled to avoid morphological decomposition of active layers upon operation.
关键词： merocyanines,photo-annealing,H-aggregates,supramolecular structure,UV-vis spectroscopy,dipole moments,aggregate formation
更新于2025-09-23 15:21:21
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Effects of 1,2-ethanedithiol concentration on performance improvement of quantum-dot LEDs
摘要： We report systematic e?ciency variations of green-emitting CdSe@ZnS quantum-dot (QD) LEDs (QLEDs) in response to in situ treatments with 1,2-ethanedithiol (EDT) solutions at various concentrations. The main e?ect of in situ EDT treatment on a QD layer spin-coated onto a ZnO layer was vacuum-level shift due to dipole moments on the surface of the QD layer and at the interface between QD and ZnO layers. Competing contributions of these dipole moments were responsible for changes in energy level con?gurations and, accordingly, electron and hole barriers that resulted in discrepancies in electron- and hole-current variations. QLED e?ciency was best when treated with an EDT solution of 4 mM, attributable to the largest increase in the hole- to electron current ratio. The maximum luminous yield of the 4 mM EDT-treated QLED was 5.43 cd A(cid:1)1, which is 10 times higher than that of an untreated device. Furthermore, the luminous yield of this treated device remained as high as 2.56 cd A(cid:1)1 at a luminance of 500 cd m(cid:1)2.
关键词： efficiency improvement,vacuum-level shift,dipole moments,quantum-dot LEDs,1,2-ethanedithiol
更新于2025-09-16 10:30:52
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Polarizability of germanium quantum dots with spatially separated electrons and holes in Ge/Si heterostructures
摘要： In the framework of dipole approximation, it is shown that the quantities (the oscillator strengths of transitions, the dipole moments for transitions, and the polarizability) describing optical absorption on surface exciton states with spatially separated electrons and holes (the hole moves in the germanium quantum dot and the electron is localised over the spherical interface of the silicon quantum dot matrix) assume giant values considerably exceeding the typical values of the corresponding quantities for semiconductors under the action of low-intensity light.
关键词： transition dipole moments,polarizability,oscillator strength,Spatially indirect excitons,quantum dots,polarization interaction,Coulomb interaction
更新于2025-09-16 10:30:52
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Self-Assembled Monolayers with Distributed Dipole Moments Originating from Bipyrimidine Units
摘要： The concept of distributed dipoles in monomolecular self-assembly on solid substrates was tested for the example of thiolate self-assembled monolayers (SAMs) on Au(111) containing dipolar 2,5?-bipyrimidine units. These were attached to a thiol anchoring group either directly or via a phenylene-methylene spacer, with the spacer decoupling the dipolar moiety from the substrate and promoting layer formation. As expected, the SAMs containing spacer groups exhibited a higher quality, including a higher packing density and nearly upright molecular orientation. The electrostatic effects of the dipolar bipyrimidine moieties were tested through C 1s and N 1s photoemission spectra, where electrostatic core-level shifts impact the shapes of the spectra. Additionally, changing the orientation of the dipoles allows a variation of the work function over a range of ~1.35 eV. The experiments were complemented by density-functional theory calculations. The work function tuning range was reasonably high, but smaller than expected considering that for SAMs with a single embedded pyrimidine group per molecule work-function changes already amounted to ~1.0 eV. This behavior is rooted in an asymmetry of the studied SAMs: For dipoles pointing away from the substrate, the expected doubling of the work function change between monopyrimidine and bipyrimidine SAMs essentially occurs. Conversely, for the downward-oriented pyrimidine dipoles, the second polar ring has hardly any effect. Consistent observations were made for the core-level shifts. We discuss several factors, which are potentially responsible for this asymmetry, like disorder, depolarization, or Fermi-level pinning. Of these, the most likely explanation is the adsorption of airborne contaminants interacting with the nitrogen atoms in the immediate vicinity of the outer surface, which are present only in films with downward oriented dipoles. In spite of these complications, some of the introduced distributed dipole SAMs serve as important model systems for understanding electrostatic effects at interfaces. They are also of interest for controlling carrier-injection barriers in organic (opto)electronic devices.
关键词： Bipyrimidine Units,Distributed Dipole Moments,Self-Assembled Monolayers,Organic (Opto)electronic Devices,Work Function Tuning
更新于2025-09-12 10:27:22
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[IEEE 2019 URSI International Symposium on Electromagnetic Theory (EMTS) - San Diego, CA, USA (2019.5.27-2019.5.31)] 2019 URSI International Symposium on Electromagnetic Theory (EMTS) - Modeling Metamaterial Element in Dielectric-filled Waveguide-fed Metasurface Antennas
摘要： We study the modeling of metamaterial elements etched into planar, dielectric-filled waveguides for metasurface antennas. Metamaterial elements in these devices are subwavelength-sized, resonant openings embedded in waveguide walls—that can be modeled as the electric and magnetic dipoles—and couple to waveguide modes and radiate into free space. Due to a dielectric filling the waveguide, the dipole moments representing the element can contribute unequally to the scattered fields into the waveguide and the radiated fields into free space. Such different dipole strengths need to be considered for analytic modeling of metasurfaces. In this work, we present a retrieval of dipole moments of a metamaterial element by applying the law of power conservation and demonstrate its utility in the analytic model for the metasurface antennas.
关键词： dielectric-filled waveguides,dipole moments,power conservation,metamaterial elements,metasurface antennas
更新于2025-09-12 10:27:22
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Transition probabilities of the seven lowest–lying singlet states of the AlN radical
摘要： In this study, the potential energy curves are calculated for the a1Σ+, b1Π, c1Δ, d1Σ+, e1Π, f1Δ, and g1Σ- states of the AlN radical. The transition dipole moments between them are computed. The rotationless radiative lifetimes of the vibrational levels are found to be approximately several μs for the d1Σ+ and g1Σ- states, on the order of several hundred ns for the e1Π state, and one-tenth to several μs for the deep well of the f1Δ state. These results suggest that the spontaneous emissions originated from these states occur readily. The rotationless radiative lifetimes of the vibrational levels are on the order of 10–100 μs for the c1Δ state, 1000 μs for the vdW minimum of the f1Δ state, and 10–1000 μs for the b1Π state. In addition, the rotationless radiative lifetimes of these states decrease with the increasing vibrational level. This result suggests that the spontaneous emissions generated from these states at lower levels should be difficult to occur. The Einstein coefficients of spontaneous emissions from the d1Σ+–a1Σ+, d1Σ+–b1Π, e1Π–a1Σ+, e1Π–b1Π, and g1Σ-–b1Π systems, as well as from the f1Δ state to the b1Π and c1Δ states are large, indicating that the emissions of these systems can be measured readily via spectroscopy. The Einstein coefficients of the e1Π–d1Σ+ transition are very small and the emissions originating from the vdW minimum of the f1Δ state are very weak, predicting that these transitions are very difficult to be detected in spectroscopy experiments.
关键词： Franck–Condon factors,transition probabilities,potential energy curves,transition dipole moments,rotationless radiative lifetimes
更新于2025-09-10 09:29:36
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) method
摘要： Absolute optical oscillator strengths of the Lyman and Werner bands of molecular deuterium are determined by a dipole(γ , γ ) method with the high energy resolution of 25 meV. A comprehensive comparison shows that an excellent agreement between the present experimental results and the earlier theoretical calculations is achieved for both Lyman and Werner bands. In addition, the electronic transition dipole moments of D2 are derived. The absolute optical oscillator strengths of the Lyman and Werner bands of D2 reported in this work can serve as the benchmark to test calculations with different theoretical models and calculational codes and, also, be used in thermonuclear fusion plasma and other ?elds.
关键词： γ ) method,dipole (γ,electronic transition dipole moments,molecular deuterium,Lyman and Werner bands,optical oscillator strengths
更新于2025-09-09 09:28:46
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Dipole Moment and Electronic Structure Calculations of the Electronic States of the Molecule SiC below 97000cm-1
摘要： Beside its importance in the astrophysics, the silicon carbide has a great importance in the industry of semiconductors and ceramics. Because of the absence of theoretical data, extensive ab initio calculations of dipole moment and higher excited electronic state have been done for this molecule. These calculations have been performed by using the Complete Active Space Self Consistent Field (CASSCF) with Multireference Configuration Interaction MRCI+Q (singly and doubly excitation with Davidson corrections). The potential energy and the dipole moment curves for the 47 low-lying singlet, triplet and quintet electronic states in the representation 2s+1Λ(+/-) of the molecule SiC have been calculated. The harmonic frequency ωe, the internuclear distance Re, the electronic energy with respect to the ground state Te, the rotational constants Be and the permanent dipole moment have been obtained for these electronic states. The comparison between the values of the present work and those available in the literature, for several electronic states, shows a good agreement. In the present work thirteen new electronic states have been investigated here for the first time. These new results may leads to more investigation of new experimental works on this molecule.
关键词： electronic structure,spectroscopic constants,permanent dipole moments,potential energy curves,ab initio calculation
更新于2025-09-09 09:28:46