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201.
Sang Woo Kwak Ju Hyun Hong Sang Hoon Lee Min Kim Yongseog Chung Kang Mun Lee Youngjo Kim Myung Hwan Park 《Molecules (Basel, Switzerland)》2021,26(1)
A novel class of quinolinol-based dimeric indium complexes (1–6) was synthesized and characterized using 1H and 13C(1H) NMR spectroscopy and elemental analysis. Compounds 1–6 exhibited typical low-energy absorption bands assignable to quinolinol-centered π–π* charge transfer (CT) transition. The emission spectra of 1–6 exhibited slight bathochromic shifts with increasing solvent polarity (p-xylene < tetrahydrofuran (THF) < dichloromethane (DCM)). The emission bands also showed a gradual redshift, with an increase in the electron-donating effect of substituents at the C5 position of the quinoline groups. The absolute emission quantum yields (ΦPL) of compounds 1 (11.2% in THF and 17.2% in film) and 4 (17.8% in THF and 36.2% in film) with methyl substituents at the C5 position of the quinoline moieties were higher than those of the indium complexes with other substituents. 相似文献
202.
Seok Ho Lee Ji Hye Lee Min Sik Mun Sanghee Yi Eunji Yoo Hyonseok Hwang Kang Mun Lee 《Molecules (Basel, Switzerland)》2021,26(6)
The photophysical properties of closo-ortho-carboranyl-based donor–acceptor dyads are known to be affected by the electronic environment of the carborane cage but the influence of the electronic environment of the donor moiety remains unclear. Herein, four 9-phenyl-9H-carbazole-based closo-ortho-carboranyl compounds (1F, 2P, 3M, and 4T), in which an o-carborane cage was appended at the C3-position of a 9-phenyl-9H-carbazole moiety bearing various functional groups, were synthesized and fully characterized using multinuclear nuclear magnetic resonance spectroscopy and elemental analysis. Furthermore, the solid-state molecular structures of 1F and 4T were determined by X-ray diffraction crystallography. For all the compounds, the lowest-energy absorption band exhibited a tail extending to 350 nm, attributable to the spin-allowed π–π* transition of the 9-phenyl-9H-carbazole moiety and weak intramolecular charge transfer (ICT) between the o-carborane and the carbazole group. These compounds showed intense yellowish emission (λem = ~540 nm) in rigid states (in tetrahydrofuran (THF) at 77 K and in films), whereas considerably weak emission was observed in THF at 298 K. Theoretical calculations on the first excited states (S1) of the compounds suggested that the strong emission bands can be assigned to the ICT transition involving the o-carborane. Furthermore, photoluminescence experiments in THF‒water mixtures demonstrated that aggregation-induced emission was responsible for the emission in rigid states. Intriguingly, the quantum yields and radiative decay constants in the film state were gradually enhanced with the increasing electron-donating ability of the substituent on the 9-phenyl group (‒F for 1F < ‒H for 2P < ‒CH3 for 3M < ‒C(CH3)3 for 4T). These features indicate that the ICT-based radiative decay process in rigid states is affected by the electronic environment of the 9-phenyl-9H-carbazole group. Consequently, the efficient ICT-based radiative decay of o-carboranyl compounds can be achieved by appending the o-carborane cage with electron-rich aromatic systems. 相似文献
203.
204.
Quantitative analysis of the self-absorption and reemission effects on the emission spectrum of photoluminescence in right-angle excitation–detection configuration
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A theoretical approach based on differential radiative transport is proposed to quantitatively analyze the selfabsorption and reemission effects on the emission spectrum for right angle excitation–detection photoluminescence measurements,and the wavelength dependence of the reemission effect is taken into account.Simulations and experiments are performed using rhodamine 6G solutions in ethanol as model samples.It is shown that the self-absorption effect is the dominant effect on the detected spectrum by inducing pseudo red-shift and reducing total intensity;whereas the reemission effect partly compensates for signal decrease and also results in an apparent signal gain at the wavelengths without absorption.Both effects decrease with the decrease in the sample concentration and the propagation distance of the emission light inside the sample.We therefore suggest that diluted solutions are required for accurate photoluminescence spectrum measurements and photoluminescence-based measurements. 相似文献
205.
Robinson I. Roacho Alejandro J. Metta‐Magaña Eduardo Peña‐Cabrera Keith H. Pannell 《Journal of Physical Organic Chemistry》2013,26(4):345-351
Fluorescent members of the 4, 4‐difluoro‐4‐bora‐3a, 4a‐diaza‐s‐indacene (BODIPY) family are widely used for a range of markers, dyes, and sensors. The capacity to substitute the basic framework is an attractive feature permitting a range of differently substituted materials to be formed. New isomeric BODIPYs, o‐, m‐, and p‐8‐[R‐C6H4]‐BODIPY (R = CH2OH, 2a (o), 2b (m), 2c (p); R = OMe, 3a (o), 3b (m), 3c (p)), have been synthesized and characterized by nuclear magnetic resonance, absorbance and emission spectroscopy, and single crystal X‐ray diffraction. The o‐isomers have a very high quantum yield emission in non‐polar solvents, while the m‐ and p‐ analogs showed weak fluorescence under the same conditions. Spectroscopic analysis, as well as X‐ray structural characterization, suggested that substitution in the ortho‐position of the phenyl ring is sufficient to increase the steric hindrance and hence impede the rotation of the phenyl moiety about the 8C‐C axis, thereby favoring radiative compared to non‐radiative relaxation. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
206.
The suppression of high pT hadron production in heavy ion collisions is thought to be due to energy loss by gluon radiation off hard partons in a QCD medium. Existing models of QCD radiative energy loss in a color-charged medium give estimates of the coupling strength of the parton to the medium which differ by a factor of 5. We will present a side-by-side comparison of two different formalisms to calculate the energy loss of light quarks and gluons: the multiple soft scattering approximation (ASW-MS) and the opacity expansion formalism (ASW-SH and WHDG-rad). A common time-temperature profile is used to characterize the medium. The results are compared to the single hadron suppression RAA at RHIC energies. 相似文献
207.
208.
Relativistic calculations on the transition electric dipole moments and radiative lifetimes of the spin-forbidden transitions in the antimony hydride molecule
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Calculations on the spectroscopic constants and transition properties of the first three states (${\rm a}^{1}\Delta $, ${\rm b}^{1}\Sigma^{+}$, and X$^{3}\Sigma^-$) of the SbH molecule were performed under the relativistic framework using the exact two-component Hamiltonian (X2C). The potential energy curves in the Franck-Condon region were computed and compared with the previous values. Furthermore, the transition dipole moments for the weak spin-forbidden transitions (${\rm b}0^{+}$-X$_{1}0^{+}$, ${\rm b}0^{+}$-X$_{2}$1, X$_{1}0^{+}$-X$_{2}$1, and X$_{2}$1-${\rm a}$2) were reported. The spontaneous radiative lifetime of the ${\rm b}^{1}\Sigma^{+}$ ($\upsilon '=0$) state was calculated as 163.5 $\pm$ 7.5 μs, which is in reasonable agreement with the latest experimental value of 173 $\pm$ 3 μs. The spontaneous radiative lifetimes of the X$_{2}$1 ($\upsilon '=0$) state and the ${\rm a}$2 ($\upsilon '=0$) state were calculated to be 48.6 s and $\sim 8 $ ms, respectively. Our study is expected to be a benchmark transition property computation for comparison with other theoretical and experimental results. The datasets presented in this paper, including the transition dipole moments, are openly available at https://dx.doi.org/10.11922/sciencedb.j00113.00018. 相似文献
209.
210.
The numerical simulation of radiative heat transfer is now well established. Key ingredients in such a simulation model are calculated view factors that are used to describe the exchange of radiated energy between different surfaces. Several methods for the calculation of these geometrical factors are available, including Integration, Monte Carlo, and the Hemi-cube methods. Several analytical test cases are also available, such as the well-known “parallel plates” case, which allow modelers to validate their view factor routines. However, there is much less information available that combines both view factor information and heat transfer effects simultaneously. This article describes the construction of a simple testing rig that allows experiments to be performed that combine view factor effects with measured heat transfer exchanged between surfaces only. The equipment has been used to consider simple cases, such as the parallel plates test case, and also cases where shadowing is important. The results of these experiments are presented as experimental benchmarking data for model users and developers. 相似文献