Synthesis and EPR of oligomeric manganese(II) complexes of a tripodal ligand tris(2-benzimidazolyl methyl)amine and its N-ethyl derivative

Abstract

Three types ofmanganese(lI) complexes of N,N',N" -tris(2-benzimidazolyl methyl)amine (NTB) and its N-ethyl (Et-NTB) derivatives have been synthesised and characterised. <em>Type I </em>complexes analyse for the formula [Mn(NTB) (C1O₄)₂]. A magnetic moment of 5.94 B.M./Mn indicates a monomeric manganese complex. EPR data find good correlation with D = 0.15 cm^-¹ and λ = 0.067. The Et-NTB analogue shows a broad <em>g</em>_eff] = 2.0 signal superimposed on which are fifteen hyperfine lines with a coupling constant of :A: = 83 ± 5 gauss. <em>T</em><em>y</em><em>pe II </em>complexes analyse for the formula [Mn₃(L)X₅) where L = NTB and Et NTB, while X = CI^-. These complexes show a strong single EPR line at <em>g</em>_eff = 2.0. The complexes have slightly lowered magnetic moment of 5.56 B.M./Mn [μ_eff trimer = 9.82, L = NTB) and 5.36 B.M./Mn [μ_eff trimer = 9.26, L = Et NTB) at room temperature. <em>Type III </em>complexes analyse for the formula [Mn(NTB)OAc]₂ [OAc]₂ with a room temperature magnetic moment of 5.99 B.M./Mn. EPR transitions at fields less than 3200 gauss, show a slightly enhanced temperature dependence.