Hexa- and heptacoordinated manganese(II) dicyanamide complexes containing a tetradentate N-donor Schiff base: Syntheses, composition tailored architectures and magnetic properties

Two 1D coordination polymers [Mn(L)(μ_1,5-dca)(MeOH)] _n(ClO₄)_n (1) and [Mn(L)(μ_1,5-dca) ]_n(PF₆)_n (2) and a dinuclear compound [Mn ₂(L)₂(μ_1,5-dca)₂(dca) ₂]×H₂O (3) [L = N,N′-(bis-(pyridin-2-yl) benzylidene)-ethane-1,2-diamine; dca = dicyanamide] have been isolated using one-pot synthesis of the building components in appropriate molar ratios and characterized. X-ray structural studies reveal that 1 forms a zigzag 1D chain through single Mn-(NCNCN)-Mn units in which each heptacoordinated manganese(II) center adopts a distorted pentagonal bipyramidal geometry with an MnN ₆O chromophore occupied with four N atoms of L, two nitrile N atoms of monobridged μ_1,5-dca and one O atom of MeOH. In 2, each hexacoordinated metal(II) center has a distorted octahedral coordination environment with an MnN₆ chromophore bound by four N atoms of L and two nitrile N atoms of two different single bridged μ_1,5-dca units; the latter connects other neighboring metal centers in a non-ending fashion affording a linear 1D chain. Complex 3 is dinuclear where two [Mn(L)]²⁺ units are connected by double μ_1,5-dca bridges with a distorted pentagonal bipyramidal environment. Variable-temperature magnetic susceptibility measurements of 1-3 show weak antiferromagnetic interactions among the metal centers through μ_1,5-dca bridges.