Syntheses, crystal structures, substituents steric effect, luminescent and moisture-stability studies of three two-dimensional zinc-organic frameworks

Three new 2D zinc-organic frameworks, [Zn3(L1)3(DMF)2]n (1), [Zn(L2)(BPP)]n (2) and [Zn2(L3)2(BPP)]n·nDMF (3), (L1 = 2,5-dimethylterephthalate, L2 = 2-aminoterephthalate, L3 = terephthalate, BPP = 1,3-bis(4-pyridyl)propane, DMF = N,N-dimethylformamide), have been prepared and characterized. Complex 1 consists of trinuclear zinc clusters connected to six L1 ligands, in which the trinuclear clusters act as pseudo-planar hexagonal nodes to give a 2D network. In complex 2, two 44-sql nets interlock in parallel and give rise to a polycatenated layer (2D → 2D). Complex 3 features a 2D (4,4) net when the dinuclear [Zn2(COO)2N2O2] unit is regarded as a quadruply-connected node. These results indicate that the steric effect of 1,4-benzenedicarboxylates substituents has an important effect on the structural topologies of such Zn(II) complexes. All of 1–3 emit the intense indigotin photoluminescence at room temperature, with lifetimes of 28.04, 3.08 and 2.43 ns, respectively. The moisture-stability analyses of 1–3 have also been investigated.