From interwoven to noninterpenetration: Crystal structural motifs of two new manganese-organic frameworks mediated by the substituted group of the bridging ligand

The respective reactions of the Mn-II ion with the homologous ligands 2-aminoterephthalic acid and terephthalic acid afforded two novel manganese-organic compounds, [Mn(2-atp)(bipy-eta)(0.5)](n) (1) and {[Mn(tp)(bipy-eta)(1.5)]center dot 2H(2)O}(n) (2). These two compounds were characterized by IR spectroscopy, elemental analysis, and single-crystal X-ray diffraction. Compound 1 (C14H11MnN2O4) belongs to the monoclinic C2 space group, Z = 4 [a = 11.9355(9) angstrom, b = 15.522(1) angstrom, c = 7.9542(6) angstrom, beta = 112.591(2)degrees], whereas compound 2 (C26H26MnN3O6) belongs to the monoclinic P2(1)/c space group, Z = 4 [a = 10.0330(3) angstrom, b = 11.9454(1) angstrom, c = 21.8640(5) angstrom, beta = 92.842(2)degrees]. Both compounds have bimetallic blocks as basic units. With two bridging carboxylate groups, the Mn center dot center dot center dot Mn separation in compound 2 is 4.841 angstrom. By contrast, the distance of the Mn center dot center dot center dot Mn centers in compound 1 (with the first paddle-like manganese core) is shortened to 3.058 angstrom by the bridging of four carboxylate groups, which suggests the existence of a Mn-Mn single bond. The paddle-wheel clusters in compound 1 aggregate into a 3D modular framework that interpenetrates in a threefold manner. The binuclear units in 2 extend to a 3D network with a novel bilayer structural motif. The inclusion of the bipy-eta molecules prevents the structure of 2 from being interwoven, and it thus adopts a noninterpenetrating arrangement. The results indicate that variations in the molecular self-assembly are influenced by the substituted group in the bridging ligand. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).