Programmed Molecular Construction: Driving the Self-Assembly by Coordination and Hydrogen Bonds Using 6-(Pyridin-2-yl)-1,3,5-triazine-2,4-diamine with M(NO₃)₂ Salts

A new series of hydrogen-bonded metallotecton networks 6-9 of the general formula [M(2)2(NO3)2] were obtained from the reaction of 6-pyridin-2-yl-[1,3,5]-triazine-2,4-diamine 2 with transition-metal ions [M: Co(II), Ni(II), Cu(II), and Zn(II)]. Their supramolecular networks and associated properties were characterized by single-crystal and powder X-ray diffraction, IR, solid-state UV-vis spectroscopy, and thermogravimetric analysis associated with differential scanning calorimetry. On the basis of standard patterns of coordination involving 2,2'-bipyridine and simple derivatives, compound 2 binds transition-metal ions with predictable constitution and the diaminotriazinyl (DAT) groups serve orthogonally to ensure the intermetallotecton interactions by hydrogen bonding according to well-established motifs I-III. As expected, compound 2 formed octahedral 2:1 metallotectons with M(NO3)2, and further self-assembled by hydrogen bonding of the DAT groups to produce pure, crystalline, homogeneous, and thermally stable materials. In these structures, nitrate counterions also play an important role in the cohesion of intermetallotectons to form two-dimensional and three-dimensional networks. These results illustrated the effectiveness of the synthetic approach to create a wide range of novel ordered materials with controllable architectures and tunable properties achieved by varying the central metal ion. Crystal morphologies of 6-9 were also investigated by scanning electron microscopy and calculation using Bravais-Friedel-Donnay-Harker method from their single-crystal structure.