Experimental and Theoretical Studies of the Spectroscopic Properties of Chalcone Derivatives.

Newly synthesized, differently substituted chalcones (1,3-diaryl-2-propen-1-ones) have been studied using steady-state and time-resolved techniques combined with quantum-chemical modelling. To explore spectroscopic structure - property relationships the substituent (acceptor moiety) was chosen according to systematic variation in the Hammett parameter. It was shown that photophysical properties of the studied donor-acceptor (D-A) molecules can be predicted in terms of a simple model from the properties of individual chromophores (composite-model of decoupled moieties: donor (D) and acceptor (A)).

Spectroscopic studies of inclusion complexes of methyl-p-dimethylaminobenzoate and its ortho derivative with α- and β-cyclodextrins.

The effects of α- and β-cyclodextrins (CDs) on the both emission modes (LE -locally excited and TICT -twisted intramolecular charge transfer) of the fluorescence spectrum of methyl-p-dimethylaminobenzoate (I) and its o-methoxy (II) derivative in aqueous solution have been investigated using steady-state and time-resolved fluorescence techniques. It is found that the intensity of both fluorescence bands increases with increasing concentration of α- and β-CD. The stoichiometries and equilibrium constants of the fluorophore-cyclodextrin inclusion complexes have been determined by steady-state fluorescence measurements.

Excitation-wavelength dependent fluorescence of ethyl 5-(4-aminophenyl)-3-amino-2,4-dicyanobenzoate.

The excitation wavelength dependence of the steady-state and time-resolved emission spectra of ethyl 5-(4-aminophenyl)-3-amino-2,4-dicyanobenzoate (EAADCy) in tetrahydrofuran (THF) at room temperature has been examined. It is found that the ratio of the fluorescence intensity of the long-wavelength and short-wavelength fluorescence bands strongly depends on the excitation wavelength, whereas the wavelengths of the fluorescence excitation and fluorescence bands maxima are independent on the observation/excitation wavelengths. The dynamic Stokes shift of fluorophore in locally excited (LE) and intramolecular charge transfer (ICT) states has been studied with a time resolution about 30 ps.

Determination of ground and excited state dipole moments of 4,5'-diamino[1,1':3',1''-terphenyl]-4',6'-dicarbonitrile using solvatochromic method and quantum-chemical calculations.

Electronic absorption and fluorescence spectra of 4,5'-diamino[1,1':3',1''-terphenyl]-4',6'-dicarbonitrile (1) were recorded at room temperature in several solvents of different polarity. The results of spectroscopic measurements are analyzed using the theory of solvatochromism, based on a dielectric continuum description of the solvent and the classical Onsager cavity model. The difference in the excited and ground state dipole moments (mu(e)-mu(g)) of the molecule under study was estimated using methods applied by Bayliss, Ooshika, McRae, Lippert, Mataga, Bakhshiev and Kawski.

Dipole moments studies of fluorenone and 4-hydroxyfluorenone.

Electronic absorption, excitation and fluorescence spectra of fluorenone and 4-hydroxyfluorenone were recorded at room temperature in several aprotic solvent of varying polarities. The ground (mu(g)) and excited (mu(e)) state dipole moments of both molecules were estimated from solvatochromic shifts of absorption and fluorescence spectra as a function of the dielectric constant (epsilon) and refractive index (n). These experimental results were completed with theoretical results of quantum chemical calculations (AM1).