Long chain defective metal string complex with modulated oligo-α-pyridylamino ligand: Synthesis, crystal structure and properties

Through a pyrimidine and naphthyridine-containing triamine ligand, N2-(pyrimidin-2-yl)-N7-(2-(pyrimidin-2-ylamino)-1,8-naphthyridin-7-yl)-1,8-naphthyridine-2,7-diamine (H3N9-2pm), defective metal string complex [Ni8.33(N9-2pm)4(NCS)2](PF6)2 (1) was successfully synthesized and structurally characterized. The complex consists of a linear metal chain and four deprotonated supporting ligands which are helically wrapped around the metal score. X-Ray crystallographic studies revealed that the complex (1) crystallizes in space group P21/c of the monoclinic system. The small J value (J = −2.90 cm−1) suggests quite a weak magnetic interaction throughout the molecule of complex (1). The weak magnetic interaction in the defective complex indicates that the spin exchange in metal string occurs through the metal core rather than the bridging ligands. The electrochemical study on complex 1 shows abundant redox properties and facility to the reduction in its cyclic voltammogram by displaying three reversible redox couples at E1/2 = - 0.35, - 0.69 and – 0.88 V. [Display omitted] •Through naphthyridine and pyrimidine modulated pentapyridyltetraamine ligand, H3N9-2pm, stable, long-chain defective nickel metal string complex 1 was successfully obtained and structurally characterized.•It is assumed that the steric force from four helical wrapping ligands is responsible for the formation of the metal chain.•The defective complex has revealed weak antiferromagnetic coupling of ca. −2.90 cm−1 between two terminal nickel(II) ions of high-spin states (S = 1) and consistent to our previous reports on the multi nickel complexes.•It is shown that the metal strings based on pyrimidine modulated ligands, can be easily reduced and retards oxidation because of the electron-withdrawing effect of pyrimidine.