Synthesis, spectral and crystallographic characterization of manganese(II) coordination polymers based on aliphatic dicarboxylate and flexible bis(imidazolyl) derivatives

Abstract

Two structurally related flexible imidazolyl ligands, bis( N-imidazolyl)methane (L 1) and 1,4-bis( N-imidazolyl)butane (L 2) reacted with Mn(II) salts of aliphatic dicarboxylic acids resulted in the formation of a number of novel metal-organic coordination architectures. All complexes have been structurally characterized by X-ray diffraction analysis. The different coordination modes of dicarboxylate anions due to their chain length, rigidity and diimidazolyl functionality lead to a range of different coordination structures. The coordination polymers exhibit 1D single chain, 2D sheet and 3D network structures. The aliphatic dicarboxylates can adopt chelating μ 2, bridging μ 2, and chelating–bridging μ 3 coordination modes, or act as uncoordinated counter anions. The central metal ions are coordinated in N 2O 4 and N 4O 2 fashions depending on the ancillary ligands. The topology of [Mn(male)(L 1)(H 2O) 2] ( 1, male = maleate) gives rise to singly bridged 1D chains, whereas compound [Mn(mal)(L 1)(H 2O)] · H 2O ( 2, mal = malonate) exhibits 2D sheets in which the metal centers are bridged by both imidazolyl ligands and dicarboxylates. Compounds [Mn(L 1) 2(H 2O) 2](suc) · 6H 2O ( 3, suc = succinate) and [Mn(L 1) 2(H 2O) 2](fum) · 6H 2O ( 4, fum = fumarate) show doubly bridged 1D chains, and the dicarboxylate groups are not coordinated but form 2D corrugated sheets with water molecules intercalated between the cationic layers. Compound [Mn(suc)(L 2)(H 2O) 2] ( 5, suc = succinate) was built from very flexible succinate and 1,4-bis( N-imidazolyl)butane which yielded three-dimensional interpenetrate networks, both succinate anion and the imidazolyl ligand act as bidentate bridging.