Spectral-Fluorescence Properties of Zn(II)-Octaphenyltetraazaporphyrins

Zn(II)-octa-(4-chlorophenyl)- and Zn(II)-octa-(4-bromophenyl)tetraazaporphyrins were synthesized by the reaction of cyclotetramerization of di-(4-chlorophenyl)- and di-(4-bromophenyl)maleonitriles with zinc(II) chloride. The obtained compounds were identified by UV-vis, IR, NMR 1 H spectroscopy and mass spectrometry. Geometry optimization of the series of halogenated Zn(II)-octaaryltetraazaporphyrins was performed using the density functional method with the BP86 functional and the def2-TZVP basis set. An analysis of the distribution of molecular orbital energies in the neighborhood of highest occupied molecular orbitals (HOMO and HOMO-1) and lowest unoccupied molecular orbitals (LUMO and LUMO+1) and the width of the HOMO – LUMO energy gaps (E H-L ) was performed for the studied compounds. Fluorimetric measurements of the Zn(II)-octaphenyltetraazaporphyrins in toluene were carried out and fluorescence quantum yields of studied compounds were determined and analyzed. It has been shown that the halogen on the para-position of the phenyl groups significantly affects the value of the obtained quantum yields of fluorescence emission but does not significantly affect the Stokes shifts.