Novel linear hexanuclear cobalt string complexes (Co612+) and one-electron reduction products (Co611+) supported by four bpyany2−ligands

Abstract

The new ligand, 2,7-bis(α-pyridylamino)-1,8-naphthyridine (H₂bpyany), was synthesized by the reaction of 2,7-dichloro-1,8-naphthyridine with 2-aminopyridine in the presence of t-BuOK under palladium(0)-catalyzed conditions. The preparation and characterization of novel hexacobalt string complexes, [Co₆(µ₆-bpyany)₄(NCS)₂](PF₆)_n (n = 1 (1); n = 2 (2)) and [Co₆(µ₆-bpyany)₄(OTf)₂](OTf)_n (n = 2 (3); n = 1 (4)) are presented. The crystal structures for compounds 1–4 have been determined by X-ray crystallography. Compounds 1 and 4 have the Co₆¹¹⁺ configurations and are air-stable. Compounds 2 and 3 with Co₆¹²⁺ configurations are structurally similar to 1 and 4, respectively. The electrochemistry of 1 displays four redox couples at E_1/2 = −0.55, +0.38, +0.91, and +1.18 V (vs. Ag/AgCl). The magnetic data show that compounds 1 and 4 are in a spin state of S = 1/2, and 2 and 3 in a spin state of S = 1. The results of the EHMO calculations on compounds 1 and 2 are in agreement with their magnetic measurements.