Synthesis, Structure, and Magnetic Properties of Bithiophene- and Terthiophene-Linked Manganese Metal–Organic Frameworks

A series of metal–organic frameworks (MOFs) containing manganese centers and oligothiophene dicarboxylate linkers have been synthesized: [Mn­(3PhT2DC)­(DMF)0.45(H2O)2.55·1.55DMF]n (1), [Mn6­(3HT2­DC)6­(DMF)3­(H2O)5·xDMF·yH2O]n (2), [Mn­(T3DC)­(H2O)2]n (3), [Mn­(T3DC)­(H2O)1.5]n (4), and [Mn­(Ph2T3DC)­(DMF)2]n (5) (H23PhT2DC = 3,3′-diphenyl-2,2-bithiophene-5,5′-dicarboxylic acid; H23HT2DC= 3,3′-dihexyl-2,2′-bithiophene-5,5′-dicarboxylic acid; H2T3DC = 2,2′:5′,2″-terthiophene-5,5″-dicarboxylic acid; H2Ph2T3DC = 3′,4′-diphenyl-2,2′:5′,2″-terthiophene-5,5″-dicarboxylic acid, DMF = N,N-dimethylformamide). Compound 1 exists as a 2D sheet, 2–4 are 3D frameworks, and 5 is a 1D chain. Compounds 3 and 4 are isomers, and 3–5 are the first examples of crystallographically characterized terthiophene coordination polymers. In the case of 1, 2, and 5, the extended structure is sensitive to β substitution of the oligothiophene linkers. Compounds 1–3 and 5 show antiferromagnetic behavior with typical values of g and J, and 3 exhibits a spin canting transition at 40 K.