English abstract
In this project we designed, synthesized and characterized some 2-pyrazoline based compounds containing naphthalene moiety and various substituents at N1 and C5 phenyl groups. These substituents vary between electron donating groups (methoxy and methyl) and electron withdrawing groups (chloro, fluoro and cyano). Studies of the photophysical characteristics of these compounds reveal the strong influence of substituent group in the fluorescence wavelength, quantum yield and fluorescence decay lifetime. Moreover, electrochemical properties were investigated in parallel with the theoretical calculations, in order to examine the potentiality of using these compounds as emissive layers in organic light emitting diodes by evaluating the hole/electron mobility and estimating the HOMO/LUMO values and the energy gap. A wide investigation on the influence of solvents polarities on the photophysical properties of pyrazoline compounds was conducted using solvents of different polarities and homogeneous solvents mixtures, by optical and theoretical measurements, which unraveled the critical influence of solvent polarity and hydrogen bonding ability on the charge transport in the excited state. The dipole moments of these compounds in the ground and excited state were also explored and compared using different methods, and the results showed greater stabilization of the studied pyrazoline molecules in the excited state.Additionally, one of the synthesized 2-pyrazoline compounds bearing carboxylic acid was used to label primary alcohols and biogenic amines. The labelling procedures were optimized and validated for the quantification of the two groups of analytes in high performance liquid chromatography with fluorescence detector, HPLC/FLD. The optimized methods proved their sensitivity and selectivity, with high photostability of the derivatives at room temperature. The method offered many advantages including high reproducibility, ease of derivatization in short time and the HPLC analysis directly from the reaction vial without need to extract the derivative. The limit of detection of as low as 0.6 mol L-1 for alcohols and 0.9 mol L-1 for biogenic amines was achieved. Conclusively, the synthesized pyrazoline label was designed to compete with the recently used labeling reagents.
