Syntheses, structures and magnetic properties of μ1,5-dicyanamide bridged di- and polynuclear manganese(II) complexes containing neutral N-donor Schiff bases: Control of coordination number and nuclearity by varying denticity

Two hexacoordinated dinuclear compounds [Mn(L1)(dca)]2(ClO4/PF6)2·CH3OH (1/2) and two heptacoordinated coordination polymers [Mn(L2)(dca)]n(ClO4/PF6)n (3/4) [L1 = N,N′-(bis-(pyridin-2-yl)benzylidene)-1,3-propanediamine; L2 = N,N′-(bis-(pyridin-2-yl)benzylidene)diethylenetriamine; dca = dicyanamide] are synthesized and characterized. Structures of 1–3 have been solved by X-ray diffraction measurements. Each manganese(II) center in 1/2 is located in a distorted octahedral environment with an MnN6 chromophore coordinated by the four N atoms of L1 and two nitrile N atoms of bibridged μ1,5 dca. Interestingly, the coordination polymer 3 forms a 1D chain through single Mn–(NCNCN)–Mn units in which each manganese(II) center adopts a pentagonal bipyramidal geometry with an MnN7 chromophore occupied with five N atoms of L2 and two nitrile N atoms of monobridged μ1,5 dca. Magnetic susceptibility measurements of 1–3 in the 2–300 K temperature range reveal weak antiferromagnetic interactions.

Two double μ1,5 dca bridged hexacoordinated dinuclear compounds [Mn(L1)(dca)]2(ClO4/PF6)2·CH3OH (1/2) and two single μ1,5 dca bridged heptacoordinated coordination polymers [Mn(L2)(dca)]n(ClO4/PF6)n (3/4) [L1 = N,N′-(bis-(pyridin-2-yl)benzylidene)-1,3-propanediamine; L2 = N,N′-(bis-(pyridin-2-yl)benzylidene)diethylene triamine; dca = dicyanamide] have been synthesized just by changing denticity of the Schiff base from 4 in L1 to 5 in L2 and 1–3 are characterized structurally and magneto-structurally.Figure optionsDownload as PowerPoint slide