Experimental and theoretical studies on the structure and spectroscopic properties of N-scorpionate complexes obtained from metallic cobalt in a one pot synthesis

Abstract

Experimental and theoretical studies on the structure and spectroscopic properties of the new Co(II) complexes [CoL1(NCS)2] (1) and [CoL2(NCS)2]·DMF (2), where L1=N,N-bis(3,5-dimethylpyrazol-1-ymethyl)amine and L2=N,N,N-tris(3,5-dimethylpyrazol-1-ylmethyl)amine, have been reported. The two N-scorpionate complexes were obtained in a one pot synthesis from a system containing zerovalent cobalt, 1-hydroxymethyl-3,5-dimethylpyrazole and NH4NCS, in the presence of MoO3 (1) and ZnCl2 (2). The most essential feature was the in situ formation of the two new multipodal organic ligands L1 and L2 in a condensation reaction between the starting ligand (1-hydroxymethyl-3,5-dimethylpyrazole) and ammonia. The crystal structures and electronic (UV–Vis), infrared (IR) and Raman spectra of the isolated complexes have been analyzed and discussed. The combined use of experiments and computations allowed a firm assignment of the majority of the observed electronic and vibrational transitions. Moreover, theoretical (DFT) calculations at the B3LYP/6–31G and B3LYP/LanL2DZ levels have been carried out to investigate the geometry of 1 and the in situ obtained ligands L1 and L2. Both experimental and theoretical methods provided results of reasonable compatibility.