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

A novel tripodal semi‐rigid ligand, 2,4,6‐tris(3‐picolylamino)‐1,3,5‐triazine (m‐H3tpat), 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‐H3tpat with copper(II) chloride and cobalt(II) chloride yielded discrete CuII complex [Cu2Cl4(m‐H3tpat)2]·2H2O·2EtOH (1·2H2O·2EtOH) and polymeric CoII complex [Co(m‐H3tpat)2(H2O)2]Cl2 (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 {Co2(m‐H3tpat)2} metallacyclic repeating units. Each cobalt(II) ion adopts a hexacoordinate octahedral geometry with a N2O4 coordination environment. Note that the m‐H3tpat 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 all‐amino tautomer in both conformers. The stabilities of the two coordination‐directed structures may be enhanced by intramolecular π–π interactions between two pyridine rings from two different m‐H3tpat 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‐H3tpat ligands within a metallacyclic unit for 2. Discrete and infinite metallacycles have been synthesized by self‐assembly from aconformationally flexible tripodal aminotriazine‐derived polypyridyl ligand.