Syntheses, structures and luminescent properties of four zinc(II) coordination polymers constructed from mixed isophthalic acid and flexible unsymmetrical bis(pyridyl) ligands

The reaction of zinc(II) salts, isophthalic acid, and four flexible unsymmetrical bis(pyridyl) ligands, namely, N-(pyridin-2-ylmethyl)pyridin-2-amine (L1), N-(pyridin-2-ylmethyl)pyridin-3-amine (L2), N-(pyridin-4-ylmethyl)pyridin-2-amine (1.3), and N-(pyridin-4-ylmethyl)pyridin-3-amine (L4), gives rise to four compounds, [Zn(ip)(L1)](n) (1), [Zn(ip)(L2)](n) (2), [Zn-3(ip)(3)(L-3)(2)](n) (3), and [Zn(ip)(L4)](n) (4), which have been characterized by elemental analysis, IR, TG, PL, powder and single-crystal X-ray diffraction. Adjacent four- and five-coordinated Zn(II) cations in compounds 1 and 2 are joined by the ip dianions in mu(2) (kappa O-1:kappa O-1) and mu(3) (kappa O-1:kappa O-1:kappa O-1:kappa O-1) modes to form single and double chains. In contrast, the ip dianions in compound 3 act in mu(3) (kappa O-1:kappa O-1:kappa O-1:kappa O-1) and mu(4) (kappa O-1:kappa O-1:kappa O-1:kappa O-1) modes to bridge three types of zinc(II) polyhedra (four-, five- and six-coordinated), thus generating layer motif with (4.6(4).8)(2)(4(2).6(4)) topology. Compound 4 presents (4,4) layer motif which is formed by the interconnection of zinc(II) tetrahedral through mu(2) (kappa O-1:kappa O-1) ip dianions and anti-L4 ligands. The four bis(pyridyl) ligands in these compounds present diverse syn- and anti-conformations, which are responsible for the diversities of supramolecular networks. Moreover, solid-state luminescent properties demonstrate that the four compounds exhibit stronger emission intensities from 383 to 527 nm at room temperature. (C) 2015 Elsevier Ltd. All rights reserved.