Three metal-organic coordination compounds based on 4,6-dipyridyl-2-aminopyrimidine: Important role of hydrogen bonding in supramolecular assemblies

The reactions of divalent metal salts and 4,6-dipyridyl-2-aminopyrimidine ligands gave rise to three metal-organic coordination compounds: [ZnL1(OOCCH3)2] (1), [Co(L2)2(OH)2]·3H2O (2), and [Cu2(L2)2(OH)2(H2O)2](NO3)2·0.5H2O (3) [L1 = 4,6-bis(2-pyridyl)-2-aminopyrimidine; L2 = 4-(2-pyridyl)-6-(4-pyridyl)-2-aminopyrimidine] and their crystal structures were determined via single-crystal X-ray diffraction. In the three structures, L1 and L2 both exhibit terminal coordination mode. As the ligands contain both hydrogen bonding donors and acceptors, hydrogen bonding interactions play a crucial role in construction of supramolecular structures. In compound 1, the mono-nuclear complexes were connected to dimer structure by hydrogen bondings; in compound 2, dimer units were constructed through intermolecular hydrogen bondings and the crystallographic water molecules link the dimers into a 1-D supramolecular chain; and in compound 3, a complicated 3-D supramolecular architecture was formed via a series of hydrogen bondings. Moreover, the compounds 1-3 display room-temperature luminescent properties.