Polymers or supramolecules generated from a new V-shaped bis-monodentate ligand and the effect of steric hindrance on coordination modes of the ligand

A new V-shaped bis-monodentate ligand L (L = 2,3'-dipyridylamine) (1) has been designed and synthesized by alkylation reaction of pyridylamine. An investigation of the charge distributions of the coordination atoms and single-point energy calculations of four conformers of ligand L based on the geometry of conformers optimized by the DFT (density functional theory) method was carried out. The results show that the four conformers of ligand L take on two stable and two less stable configurations. Theory forecasts that two relatively stable configurations present in complexes as probable coordination motifs of the ligand, and that steric hindrance of pyridine nitrogen atoms in isomers will affect its coordination ability together with the electronic factor. This forecast has been demonstrated by the coordination chemistry of ligand L, that is, configuration (a) and (b) of the ligand occur in the following reported complexes, which combines with Ag-I or Cu-II through two coordination modes (bidentate bridging or a monodentate mode) resulting in coordination polymers {[Ag (L)(2)]NO3}(n) (2), [Cu-2(L)(2)(Maa)(4)](n) (maa = methacrylic acid) (3), and the mononuclear molecule [Cu(L)(4)](ClO4)(2)(.)2CH(3)CH(2)OH (4). The ligand assumes different coordination modes in the three complexes because of different levels of steric hindrance of the pyridine nitrogen atoms in the conformers. Interestingly, polymers 2 and 3 assume a 1D helical structure and a linear framework, respectively, and 4 has a 2D supramolecular architecture induced from hydrogen bond interactions. In addition, the magnetic proper-ties of 3 have been explored, which shows a strong antiferromagnetic interaction.