Investigation of structural and photophysical properties of some oxazolone derivatives

In this thesis, crystal structures of some 4-arylidene-2-aryloxazolone derivatives were investigated by single crystal X-ray diffraction technique. Furthermore, investigated molecules were modeled by quantum mechanical calculations, ground state geometries were determined and compared to crystallographically determined geometries to investigate the effects of crystallization on the molecular conformation. In addition, photophysical properties of these structures were modeled. Variation of fluorescence properties were investigated in different media.Besides the crystallographically studied structures; dimethylamino, as electron donor, substituted on the para- position of benzylidene ring, nitro group, as electron acceptor, substituted to the para-, ortho- and meta- positions of phenyl ring of 4-benzylidene-2-phenyloxazolone to generate six molecular structures. Electrons transfer from the electron donor amino group at the benzylidene ring to the electron acceptor nitro group at the phenyl ring over the whole molecule, and effect on the photophysical properties of these molecules were modeled. In addition to the variation of nitro group position, to alter the dielectric property of the media of the molecule six different solvents were used on each molecule, and effects of these variations on the fluorescence properties of these molecules were investigated. The molecules exhibited positive and negative solvatochromism due to the nitro positions were observed. Solvatochromism of the molecules depend not only on the difference of the dipole moments between the ground and excited states, but LUMO - HOMO energy differences. Molecular fragment analysis were studied to investigate the effect of the position of nitro group, and the media of the molecules on the charge transfer along the molecules.