Fine-Tuning of Linear Hexa-Cobalt and Defective Penta-Cobalt Metal-String Complexes
Journal
Zeitschrift fur Anorganische und Allgemeine Chemie
Journal Volume
641
Journal Issue
12-13
Pages
2258-2265
Date Issued
2015
Author(s)
Abstract
The ligand, 2, 7-bis(α-5-phenylpyrazinamino)-1, 8-naphthyridine (H2bphpzany), was synthesized by the reaction of 2, 7-dichloro-1, 8-naphthyridine with 2-amino-5-phenylpyrazine in the presence of potassium tert-butoxide under palladium(0)-catalyzed conditions. Linear defective penta-cobalt metal-string complex [Co5(bphpzany)4(NCS)2] (1) and hexa-cobalt Co611+ complex [Co6(bphpzany)4(NCS)2](PF6) (2) each containing four bphpzany2- ligands were synthesized, and their structure was determined using single-crystal X-ray diffraction. The structure of complex 1 consists of two lantern-type dinuclear Co2 fragments at the terminal positions and one rare octacoordinated cobalt at the center forming a linear [Co2···Co···Co2] chain. The magnetic susceptibility measurement of 1 shows a quartet ground state with a significant spin-orbital contribution of the central CoII ion. Complex 2 consists of a linear Co611+ configuration wrapped by four bphpzany2- ligands and its magnetic susceptibility measurement reveals a two-stages magnetic behavior with spin-states of S = 1/2 at 2 K, and S = 3/2 at 300 K. The cyclic voltammograms display three redox waves at E1/2 = +0.97, E1/2 = +0.71 and E1/2 = -1.02 V for 1, and four waves at E1/2 = +1.32, E1/2 = +0.99, E1/2 = +0.64, and E1/2 = -0.14 V for 2, respectively. The values of single-molecular resistance for 1 and 2 are 15.5 (±4.84) and 16.1 (±10.4) MΩ, respectively.
Type
journal article