Sample-size dependence of the fluorescence of 2-(N-acetylamino)-6-methylpyridine and its Zinc(II).chloride complex

Zinc(II) chloride complex with 2-(N-acetylarnino)-6-methylpyridine (L) [ZnLCl2] has been obtained by the reaction between ethanol solutions of L and ZnCl2. The complex has been characterized by a set of methods including elemental analysis, IR-spectroscopy, single-crystal X-ray diffraction analysis, and powder diffraction data. The crystal structure of [ZnLCl2] revealed distorted tetrahedral coordination geometries around the Zn2+ ion, where L acts as a bidentate chelate ligand bound to the metal center through the pyridine N atom and the acetyl O atom. Comprehensive studies of photoluminescence for the ligand and complex were carried out. Two observable photoluminescence bands in the UV region of the polycrystalline ligand spectrum exist due to the intramolecular transitions and intermolecular pi-pi interactions. The electronic states of the ligand give the main contribution in. photoluminescence spectra of the complex. There are two luminescence bands in the UV and visible regions for polycrystalline [ZnLCl2]. It was detected that the effect of the quantum yield increasing of luminescence in comparison with polycrystalline [ZnLCl2] (4%) for film samples - up to 8%, for mesoporous structures up to 14%. Changing the position of the energy levels has been observed at transition from the bulk samples to films and nanoparticles in mesoporous structures.