Synthesis, structure and photoluminescence properties of copper(II) and cobalt(III) complexes with pyridoxalaminoguanidine

Abstract The synthesis, physico-chemical characterization and crystal structure of two new transition metal complexes with the Schiff base of pyridoxal and aminoguanidine, i.e. pyridoxalaminoguanidine (PLAG) of the formulas [Co(PLAG–2H)(NH3)3]NO3·MeOH (complex 1) and [Cu(PLAG–H)N3] (complex 2) are described. The X-ray analysis showed that in complex 1 Co(III) is situated in an octahedral environment, while in complex 2 Cu(II) has square-planar surroundings. In both complexes PLAG is coordinated as usual, through the oxygen atom of the deprotonated phenolic OH-group and nitrogen atoms of the azomethine and imino groups of the aminoguanidine fragment. These compounds, as well as [Cu(PLAG)MeOH](NO3)2 (complex 3) were tested using photoluminescence spectroscopy upon 325, 458 and 488 nm laser excitation. Photoluminescence spectra had been measured and discussed for all three obtained compounds. Peak positions and their intensities were distinguished using Lorentzian multipeak technique. The results indicate that complex 1 gives significantly (for about two to three orders of magnitude) higher photoluminescence than the other two analyzed complexes. A scheme of energy levels and transitions is proposed to explain the obtained experimental results.