Crystallization and Magnetic Behavior of Manganese(II) 4,4′-Benzophenone Dicarboxylates and a Comparison of Its Structural Landscape with 2,4′-Benzophenone Dicarboxylate

Exploration of the structural landscape of the system Mn(II) salt–4,4′-benzophenone dicarboxylic acid–N-donor based auxiliary ligand–solvent using high-throughput solvothermal reaction led to the isolation of seven new coordination polymers (CPs): [Mn(phen)(H2O)(4,4′-bpdc)2] 1, [Mn3(2,2′-bipy)2(4,4′-bpdc)3]·solvent (solvent = DMA, DMF, and DMSO for 2, 3, and 4, respectively), [Mn3(4,4′-dimethyl-2,2′-bipy)2(4,4′-bpdc)3] 5, {Mn(5,5′-dimethyl-2,2′-bipy)(H2O)4}[Mn(5,5′-dimethyl-2,2′-bipy)(4,4′-bpdc)2]·H2O 6, and [Mn2(4,4′-bipy)(DMA)2(4,4′-bpdc)2] DMA 7 (4,4′-bpdc = benzophenone-4,4′-dicarboxylate, phen = 1,10 phenanthroline, 2,2′-bipy = 2,2′-bipyridine, 4,4′-dimethyl-2,2′-bipy = 4,4′-dimethyl-2,2′-bipyridine, 5,5′-dimethyl-2,2′-bipy = 5,5′-dimethyl-2,2′-bipyridine, 4,4′-bipy = 4,4′-bipyridine). A single-crystal X-ray diffraction study revealed that the presence of phen led to solid 1 that contained 1D chains made of Mn(II)-carboxylate dimers. The auxiliary ligand 2,2′-bipy and its 4,4′-dimethyl derivatives in a suitable solvent led to the growth of the solids 2 and 5 with a trimeric manganese cluster, where the building block, 1:1 manganese carboxylate got extended into 2D sheet and 3D network, respectively. The ligand 2,2′-bipy with 5,5′-dimethyl substitution led to 1D anionic chains of the composition, [Mn(5,5′-dimethyl-2,2′-bipy)(4,4′-bpdc)2]2–, stabilized by the cationic complex, {Mn(5,5′-dimethyl-2,2′-bipy)(H2O)4}2+ in 6. As expected, the auxiliary ligand, 4,4′-bipy acted as a bridging unit to pillar 1D chains of manganese-carboxylate forming a 2D sheet in 7. Retro analysis of the various structures reported here provided a mechanistic approach not only to rationalize the crystal packing of manganese(II) 4,4′-benzophenone dicarboxylates but also to enhance the understanding of crystallization of manganese(II) 2,4′-benzophenone dicarboxylates and other related solids. We have also discussed the antiferromagnetic behavior of 1, 2, 5, and 7 in the context of other structurally related manganese(II) dicarboxylates.