Discrete and Infinite Metallacyclic Coordination Architectures Based on a Conformationally Flexible Tripodal Aminotriazine-Derived Polypyridyl Ligand

[[abstract]]A novel tripodal semi-rigid ligand, 2,4,6-tris(3-picolylamino)-1,3,5-triazine (m-H(3)tpat), consisting of a triazine central core and three pyridine donating functions attached to flexible NHCH2- arms has been designed and synthesized. The self-assembly reactions of m-H(3)tpat with copper(II) chloride and cobalt(II) chloride yielded discrete Cu-II complex [Cu2Cl4(m-H(3)tpat)(2)]center dot 2H(2)O center dot 2EtOH (1 center dot 2H(2)O center dot 2EtOH) and polymeric Co-II complex [Co(m-H(3)tpat)(2)(H2O)(2)]Cl-2 (2), respectively. Complex 1 has a metallacyclophane structure with a metal-to-ligand ratio of 2:2. Each copper(II) ion adopts a pentacoordinate square-pyramidal geometry with a N3Cl2 coordination sphere. Complex 2 exhibits an extended chain structure based on {Co-2(m-H(3)tpat)(2)} metallacyclic repeating units. Each cobalt(II) ion adopts a hexacoordinate octahedral geometry with a N2O4 coordination environment. Note that the m-H(3)tpat ligand exists in a cis-cis-cis conformation in 1 and a cis-trans-trans conformation in 2, with the central aminotriazine moiety appearing to be an asymmetric-configured allamino tautomer in both conformers. The stabilities of the two coordination-directed structures may be enhanced by intramolecular p-p interactions between two pyridine rings from two different m-H(3)tpat ligands within the metallacyclophane structure of 1 and by a set of complementary double hydrogen bonds (DA-AD arrays) between two aminotriazine moieties of two m-H(3)tpat ligands within a metallacyclic unit for 2.[[note]]SC