Synthesis and crystal structure of a polymeric Mn(II) coordination complex based on 3,4-pyridinecarboxylate

In this study, a polymeric coordination compound with the composition C₁₀H₁₀MnN₂O₅ has been structurally characterised. The results indicate that the compound crystallises in the monoclinic crystal system with the space group P2₁/c. The unit cell parameters are a = 7.7002(6) Å, b = 10.2149(6) Å, c = 15.0286(12) Å, and β = 104.102(8)°, with a cell volume of 1146.48(15) ų.

The manganese(II) centre exhibits a coordination number of six, being surrounded by five oxygen atoms and one nitrogen atom, thereby forming a distorted octahedral geometry. The Mn–O bond lengths are in the range 2.154–2.176 Å, whereas the Mn–N bond length is 2.320 Å. These distances are consistent with those typically observed for Mn(II) coordination environments, confirming the expected bonding characteristics.

The organic ligand fragment contains an aromatic ring system that is essentially planar. The C–C bond lengths lie in the range 1.377(4)–1.400(4) Å, while the C–N bond lengths are 1.334(4)–1.345(4) Å, indicating the presence of a delocalised π-conjugated system. The carbonyl C–O bond distances, ranging from 1.226(5) to 1.254(4) Å, are in good agreement with expected values.

The crystal structure is primarily stabilised by metal–ligand coordination bonds together with weak supramolecular interactions, including C–H···O and C–H···π contacts. No significant solvent-accessible voids were observed within the lattice.

In the crystal packing, weak supramolecular interactions further contribute to stabilisation. In particular, weak C–H···π interactions are observed between aromatic rings, such as the C2A–H2AC···Cg1 contact with a distance of 2.839 Å. In addition, the centroid–centroid separation between adjacent aromatic rings is 5.456 Å, indicating weak π–π stacking interactions. Although no classical hydrogen bonds are present, weak C–H···O interactions also play a role in stabilising the crystal packing.