Two-dimensional zinc(II) and copper(I) coordination polymers for photoluminescence

Two-dimensional (2-D) coordination polymers [Zn₂(bpab)(CH₃CO₂)₄]·H₂O (1), [Zn(bpab)(H₂O)₂](NO₃)₂ (2), [Cu₂(bpab)I₂]·CH₃OH (3), and [Cu₂(tpmd)I₂] (4) have been synthesized by the reaction of zinc(II)/copper(I) ions and tetradentate polypyridine ligands (bpab = bis-1,4-(di-4-pyridylaminomethyl)benzene and tpmd = N,N,N',N'-tetrakis(pyridine-4-yl)methanediamine). The zinc(II) ions of 1 and 2 have distorted tetrahedral and trigonal bipyramidal geometries, respectively. By coordinating zinc(II) ions and bpab ligands, 1 and 2 formed a brick wall and puckered 2-D networks, respectively. The copper(I) ions of 3 and 4 are both tetrahedral structures with Cu₂I₂ rhomboidal geometry. By linking the Cu₂I₂ cores and bpab/tpmd ligands, 3 and 4 exhibited interwoven and interconnected bilayered 2-D networks, respectively. Compared to free bpab and tpmd ligands, polymers 1 and 2 show strongly blue-shifted emissions, whereas polymers 3 and 4 show strongly red-shifted emissions. Therefore, the shifts of emission wavelengths are strongly dependent on the zinc(II) and copper(I) ions that linked the bpab/tpmd tetradentate ligands, respectively.