Synthesis, spectroscopic, thermal, and structural properties of cyanobridged metal complexes containing tetracyanonickelate(II) building blocks with 4-aminomethylpyridine

Abstract

New cyano-bridged metal complexes with chemical formulas [Fe(NH3)2(ampy)Ni(CN)4]n, [Co(H2O)2(ampy)Ni(CN)4]n and [Ni(NH3)2(ampy)Ni(CN)4]n (ampy = 4-aminomethylpyridine, hereafter abbreviated as Fe -Ni-ampy, Co-Ni-ampy and Ni-Ni-ampy) were obtained in the form of powders and examined by vibrational (infrared and Raman) spectroscopy, thermal (TG, DTG and DTA), and elemental analysis techniques. The infrared and Raman spectra of the complexes were performed in the range of 4000-400 cm -1 and 4000-250 cm -1 , respectively. General information about the structural features of synthesized complexes was obtained by considering the changes in the cyano group and characteristic peaks of ampy. The cleavage of the (CN) stretching bands in the infrared spectrum of the complexes shows that the terminal and bridge cyano groups are in the structure. Considering the variations in the vibrational frequencies of the cyano group and ampy ligand in the spectrum of the complexes, the Ni atom is in a square plane geometry with four cyano groups and two of these cyano groups are the bridge and the other two are terminal. In addition, the metal atoms [Fe(II), Co(II) or Ni(II)] are linked to the ring and amino nitrogen atoms of two symmetric ampy ligands, the two ammonia (two aqua ligands for Co-Ni-ampy) ligands and the two bridging cyano groups, and show a distorted octahedral geometry. The thermal degradation of the complexes was also studied between 30 and 950 ºC using TG, DTG, and DTA techniques.