Molecular and supramolecular structures of manganese(II) and cobalt(II) complexes with 1-carboxymethylpyridinium-4-carboxylate

Two complexes with a zwitterionic dicarboxylate ligand, Mn(L) ₂(H₂O)₄ 1 and Co(L)₂(H ₂O)₄ 2 (L = 1-carboxymethylpyridinium-4-carboxylate), were synthesized and structurally characterized. Complex 1 crystallizes in monoclinic, space group P2₁ with a = 6.490(2), b = 19.210(7), c = 7.813(3) Å, β = 92.716(5)°, V = 972.9(6) ų, Z = 2, M_r = 487.28, D_c = 1.663 g/cm³, F(000) = 502, μ = 0.749 mm^-1, S = 1.060, the final R = 0.0377 and wR = 0.0893 for 3292 observed reflections with I > 2σ(I). Complex 2 is isomorphous with 1, with a = 6.478(2), b = 19.052(7), c = 7.742(3) Å, β = 92.690(4)°, V = 954.6(6) ų, Z = 2, M_r = 491.28, D_c = 1.709 g/cm³, F(000) = 506, μ = 0.971 mm^-1, S = 1.035, the final R = 0.0425 and wR = 0.0809 for 3289 observed reflections with I > 2σ(I). In the compounds, the mononuclear [M(L)₂(H₂O)₄] units with trans-octahedral coordination geometry are linked into 3D architectures via hydrogen bonding (or second-sphere coordination) involving carboxylate groups and coordinated water molecules. The 3D networks illustrate a 3,8-connected net with Schläfli symbol (4·6²)₂(4²·6 ²³·8³).