Two-electron redox-active tricyano iron(ii) complex with 2,4,6-tris(2-pyrimidyl)-1,3,5-triazine as a building block for coordination polymers

Abstract

A new tricyano iron(II) building unit, [{K(H₂O)₄}{Fe^II(CN)₃(L)}]·3H₂O (1), was synthesized by the reaction of Moor's salts with 2,4,6-tris(2-pyrimidyl)-1,3,5-triazine (L) as a capping ligand. X-ray structural analysis reveals that the mononuclear iron(II) tricyano complex consists of one ligand and three cyanide groups, with K⁺ ions coordinated between neighboring units to form a one-dimensional chain network structure. 1 shows two reversible redox waves at +0.713 and −0.849 V vs. SCE, which are assigned as Fe(II)/Fe(III) and L/L˙⁻ processes, respectively. One-dimensional 4,2-ribbon chain type coordination polymers, [M^II(H₂O)₂{Fe^II(CN)₃(L)}₂]·6H₂O (M = Fe (2) and Mn (3)), were synthesized by using 1 as a building unit. Cryomagnetic studies reveals that 2 and 3 show paramagnetic behaviour of S = 2 and 5/2, respectively. On the other hand, reaction of 1 and Gd(NO₃)₃·6H₂O forms another one-dimensional chain, [Gd^III(NO₃)₂(H₂O)₃{Fe^II(CN)₃(L)}]·0.5H₂O·2CH₃OH (4), showing S = 7/2 paramagnetic behaviour.