Two supramolecular isomers of dimeric cobalt(II) 5-aminoisophthalate: 2D (4,63) vs 3D Rutile nets

The hydrothermal preparation via variations of the solvent conditions of Co(NO3)2·6H2O with 5-aminoisophthalic dianion (5-NH2-bdc) exhibits two new supramolecular isomerism of [Co(C8NH5O4)(H2O)]n·2nH2O (1) and [Co(C8NH5O4)(H2O)]n (2). The reaction in EtOH/H2O resulted in a layered structure of 1 featuring an unusual zigzag water chain between adjacent sheets, and that in H2O led to an open 3D framework structure of 2. The structural data suggest that both the relative orientations in the ligand placement and the donor groups arrangement around the cobalt center are the key factor affecting the patterns of conformational supramolecular isomerism of 1 and 2. More interestingly, simplified by considering the cobalt dimer and NH2-bdc ligand represented an octahedronal node and a triangular node, respectively, structural diversity of 1 and 2 exhibits a structure evidence of 3,6-connecting building blocks with different topologies from 2D (4,63) net to 3D Rutile net. Two Complexes exhibit the excellent thermal stability with the tolerate temperature ca. 440 °C for 1 and 410 °C for 2, respectively, which attribute to the presence of abundant coordination bonds of the μ4 bridging mode dianion, and the chelate effect of carboxylate groups in the dimer SBUs.