Linear hexanuclear nickel complexes with rich electrochemical features and facility to reduction

Abstract Two novel linear hexanuclear nickel complexes [Ni 6 ( μ 6 -dpznda) 4 Cl 2 ](PF 6 ) 2 (1) and [Ni 6 ( μ 6 -dpznda) 4 (NCS) 2 ](PF 6 ) 2 (2) (H 2 dpznda =  N 2 , N 7 -di(pyrazin-2-yl)-1,8-naphthyridine-2,7-diamine) were synthesized and structurally characterized. Both the two complexes consist of a linear metal chain and four supporting ligands which are helically wrapped around the metal core. The single crystal X-ray structural analysis showed that the complex 1 belonged to rhombohedral system, space group R -3 with a  =  b  = 34.2051(8), c  = 20.7751(5) A, V  = 21050.2(9) A 3 and Z  = 9. Direct-current magnetic susceptibility measurements showed weak antiferromagnetic interactions with coupling parameters of g  = 2.04 and J  = −8.27 cm −1 for 1 and g  = 2.02 and J  = −12.62 cm −1 for 2 , respectively ( Ĥ  =  –JŜ 1 Ŝ 2 , S 1  =  S 2  = 1). The decrease of magnetic moments at low temperature was partly attributed to ZFS. The electrochemical study on complex 1 shows rich features and facility to reduction in its cyclic voltammogram by displaying four reversible redox couples at E 1/2  = +0.01, −0.29, −0.64 and −0.73 V ( vs. Ag/AgCl).