Synthesis, Spectral-Luminescent Properties, and Photostability of Zn(II) Complexes With Dipyrrins Modified by the Periphery and meso-Spacer

A comparative spectral-luminescent characterization was performed for the homoleptic zinc(II) chelates with dipyrrins containing four methyl or aryl substituents in the pyrrole rings and methine group or nitrogen atom as meso-spacer. It was shown that zinc dipyrrinates with substituted pyrrole rings and a methene spacer exhibited an intense fluorescence in nonpolar media. The phenyl-substituted complex had an order of magnitude stronger fluorescence than the methyl-substituted analog. Changing from a methene spacer to a nitrogen atom caused a substantial (up to 64 nm) red shift of the electronic absorption spectrum, and the chelate completely lost its fluorescent properties. The effects of the chelate ligand structure on the photostability of zinc(II) complexes were established.