Phonon assisted charge transfer in complexes of Zn(II) and Cd(II) with 2-acetylpyridine-aminoguanidine

Metal complexes with some Schiff bases, as one of the most widely used groups of ligands, have a wide field of application. In order to find a material with the required optical properties, it is very important to examine the material characteristics as a function of the type of chelating ligand, metal, and the ions present as coligands. In this paper, the synthesis of two new complexes of 2-acetylpyridine-aminoguanidine (L) with zinc(II) and cadmium(II), viz. [Zn(L)(NCO)2] and [{Cd(L)Cl(μ-NCO)}2] is described. Their structural characterization was provided by using SC-XRD. Spectroscopic characterization of these two new complexes and two previously synthesized complexes - [Zn(L)(NSC)2] and [Cd(L)Cl2] are performed. Their phonon structure was determined based on the IR transmission and Raman spectra. The range of Raman modes with significantly increased intensities was registered (1000-1700 cm−1), the same range for all four samples. Also, the registered photoluminescence and energy transfers were analyzed and three photoluminescence peaks (E1, E2, E3) were determined. It was concluded that phonons with significantly increased intensities participate in transitions from the E1 state to the energy levels in the range from E2 to E3. The strength of the peaks was significantly affected by replacing one [Cl]- with the [NCO]- ligand. The addition of the second [NCO]- ligand increases the photoluminescence over the entire measured range. The analysis performed helps to understand the issues related to the electron-phonon interaction. Also, the perspectives for the application of metal complexes with various ligands are expanding.