Hydrothermal Synthesis, Structures, and Physical Properties of Four New Flexible Multicarboxylate Ligands-Based Compounds

Four new compounds of partially or wholly deprotonated 5,5'-(1,4-phenylenebis(methylene))bis(oxy)diisophthalic acid (H(4)L1) and 5,5'-(1,3-phenylenebis(methylone))bis(oxy)diisophthalic acid (H(4)L2), namely {[Co(L1)(0.5)]center dot(H2O)(2)}(n) (1), {[Mn(L1)(0.5)]center dot(H2O)(2)}(n) (2), {[Cu(H(2)L1)](mu(2)-bipy)}(n) (bipy = 4, 4'-bipyridyl) (3), and {[Zn-2(L2)]center dot H2O}(n) (4) were synthesized in the presence or absence of auxiliary bipy ligand. Their structures have been determined by single-crystal X-ray diffraction analysis and further characterized by elemental analysis, IR spectra, and thermogravi metric analysis. Compounds 1 and 2 are isostructural and possess three-dimensional (3D) networks. In compound 3, multicarboxylate ligands and bipy ligands link Cu centers to generate a two-dimensional (2D) sheet structure which is further connected by intermolecular hydrogen bonds to form a 3D supramolecular structure. In compound 4, the Zn centers are connected by L2(4-) anions to generate a 3D framework. Magnetic susceptibility measurements indicate that compounds 1 and 2 exhibit antiferromagnetic coupling between adjacent Co(II) ions and Mn(II) ions. The photoluminescent properties of the free H(4)L1 and H(4)L2 ligands and compound 4 have been studied in the solid state at room temperature. Both ligands and compound 4 exhibit strong violet emissions. Compared with the fluorescent emission of the ligand, the emission of 4 is red-shifted and enhanced.