Quenching of the fluorescence of ditolyl aminoacridine solutions by tetrabromomethane

It has been shown that fluorescence quenching of 2,7-dimethyl-N,N-di-p-tolylacridine-9-amine (9-DTAA) solutions in hexane and acetone by tetrabromomethane (TBM) was dynamic in nature with the quenching rate constants of 1.5 × 10¹⁰ and 0.6 × 10¹⁰ M⁻¹s⁻¹, respectively. The difference in the constants was explained by the possibility of competition between the processes of the formation of solvation shell around the excited singlet 9-DTAA* molecule and the formation of the 9-DTAA*/TBM encounter complex.     

Synthesis and Photophysical Properties of Alkoxysilyl Derivatives of Dibenzoylmethanatoboron Difluoride

Alkoxysilyl derivatives of dibenzoylmethanatoboron difluoride (DBMBF₂) are synthesized by the hydrosilylation reaction of the corresponding O‐allyl derivatives of DBMBF₂ with triethoxysilane. The photophysical properties of the synthesized O‐allyl and alkoxysilyl derivatives are investigated. It is found that the absorption and fluorescence spectra of the DBMBF₂ derivatives essentially depend on the position of the O‐allyl or O‐propyl alkoxysilyl substituent. The highest fluorescence quantum yield is obtained for the para‐position, whereas the substitution at the meta‐position gives the largest bathochromic shift in the fluorescence spectrum. Density functional theory calculations of the structures and time‐dependent density functional theory calculations of the gas‐phase excitation and emission energies of alkoxysilyl derivatives are performed at the PBE0/SVP level of theory. Some spectral features of para‐, ortho‐, and meta‐substituted derivatives can be adequately explained by the overlapping of two absorption bands.     

Higher order symmetrizer and application to an unusual transport equation

We study a class of stationary transport equation with nonlocal low-order tems We obtain the existence and uniqueness of a solution in sobolev spaces     

求解复杂湍流的非线性涡黏性系数模型和代数应力模型

非线性涡黏性系数模型和代数应力模型联系了线性涡黏性系数湍流模型和完整的微分 雷诺应力模型.随着它们受到日益关注,其形式也越来越多样化.本篇综述的目的是对这些模 型加以总结并比较它们之间的共同点及不同之处,指出它们与完整微分雷诺应力模型之间的 关系,以及相对于线性涡黏性系数模型而言它们在预报流场上所具有的优势.     

A combined theoretical and experimental study on molecular photonics

A detailed account of quantum chemical procedures for estimating the rate constants of the photophysical processes at work in polyatomic organic molecules is given. The results obtained from combined experimental and theoretical research into the spectral-luminescent properties of acridine, 9-aminoacridine, 2,7-dimethyl-9-diphenylaminoacridine, and of their protonated forms are reported. The electronic absorption and fluorescence spectra of acridine have been investigated at room temperature in ethanol solution of varying pH and in other solvents of different chemical nature and polarity. The energy of excited states, the rate constants of the deactivation of the excited states, and the dipole moments obtained by quantum chemical methods for the examined compounds are presented. The findings of the investigations are discussed. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 93–107, October, 2008.     

Density functional calculations of 9-diphenylaminoacridine fluorescent indicator and its interactions with analyte molecules: I. Structures of complexes in the ground electronic states and absorption spectra

The interaction of 9-diphenylaminoacridine dye (indicator) with several small analyte molecules (methanol, acetonitrile, acetone, tetrahydrofuran, benzene, ammonia, formaldehyde, and acetaldehyde) has been theoretically studied in relation to the problem of the development of optical chemosensors based on organic dyes. The structures of the resulting complexes and the absorption spectra of 9-diphenylaminoacridine and its complexes with analytes were calculated using density functional theory (DFT) with the PBE0 functional and the 6-31G(d,p) basis set. It was demonstrated that complexes of two types with different mutual arrangements of molecules corresponding to the lateral and stacking structures can be formed for each analyte. The calculated absorption spectrum only weakly changes upon complex formation, which is in agreement with experimental data on the absorption spectra of 2,7-dimethyl-9-ditolylaminoacridine in solutions of corresponding solvents. The method for the calculation of excited states that was used in this work can be applied to the calculation of the fluorescence spectra of 9-diphenylaminoacridine complexes.     

Determination of electron affinity of carbonyl radicals by means of negative ion mass spectrometry

Appearance energies of [M-H](-) ions from carbonyl compounds R-CO-R' (R,R' = H, CH(3), NH(2), OH) have been measured by means of negative ion mass spectrometry in resonant electron capture mode. Values of electron affinity of the corresponding radicals, CH(2)&dbond;C(X)O, NH&dbond;C(X)O and O&dbond;C(X)O, have been determined. Copyright 1999 John Wiley & Sons, Ltd.