Kapil Tomar

Cd(II) coordination polymers constructed with a flexible carboxylate linker and pyridyl co-linkers: variation in the network topologies and photoluminescence properties

Six new coordination polymers (CPs) of Cd(II), {[Cd3(L)2(H2O)5(μ-H2O)]·6H2O}n (1), {[Cd3(L)2(4,4′-bpy)3(H2O)2]·4(H2O)·(DEF)}n (2), {[Cd(HL)(dpe)0.5(H2O)]2·(H2O)}n (3), {[Cd(HL)(dpd)0.5(H2O)]}n (4), {[Cd(HL)(1,2-dpe)0.5]}n (5), and {[Cd3(L)2(1,3-dpp)2]·3H2O}n (6) (where H3L = 5-(2-carboxybenzyloxy)isophthalic acid, 1,3-dpp = 1,3-di(4-pyridyl)propane, 1,2-dpe = 1,2-di(4-pyridyl)ethane, dpd = 1,2-di(pyridin-4-yl)diazene, dpe = 1,2-di(4 pyridyl)ethylene, and 4,4′-bpy = 4,4′-bipyridyl), were synthesized under solvothermal/hydrothermal conditions and structurally characterized via elemental analysis, IR spectroscopy, and single-crystal and powder X-ray diffraction. Compound 1 displays infinite 2D sheets, which stack upon each other to form a supramolecular 3D network. Topologically, the network can be viewed as a 3,3,3,5-connected four nodal net, which was assigned to a novel topological type, pkb9. Compound 2 shows a 3D assembly with the 3,4,6-connected topology sqc130. Compound 3 and 4 form interdigitated 3D supramolecular networks with a 4-connected sql/Shubnikov topology. Compound 5 shows an unusual 2D → 3D framework with a 3,8-connected tfz-d; UO3 topology. In compound 6, 2D → 3D packing was observed due to weak C–H⋯O interactions that aided in the formation of a 3D network with a 4-connected sql/Shubnikov topology. The luminescence properties of all the compounds in their solid state and as emulsions in various solvents were investigated using nitroaromatic compounds.

Structural diversity of Zn(II) based coordination polymers constructed from a flexible carboxylate linker and pyridyl co-linkers: fluorescence sensing of nitroaromatics

The flexible carboxylate linker, H3L = 5-(2-carboxybenzyloxy)isophthalic acid, and a group of N-donor co-linkers such as 1,2-di(4-pyridyl)ethylene (dpe), 1,2-di(4-pyridyl)ethane (1,2-dpe), 1,2-di(pyridin-4-yl)diazene (dpd), and 1,3-di(4-pyridyl)propane (1,3-dpp), give rise to five new coordination polymers (CPs) with Zn(II) ions. These are {[Zn2(L)(μ-OH)(dpe)(H2O)]}n (1), {[Zn(L)(1,2-dpe)1.5]·H2O}n (2), {[Zn(HL)(dpd)1.5]2·2(H2O)}n (3), {[Zn(HL)(1,3-dpp)]}n (4), and {[Zn5(L)4(H2O)2]·8(H2O) (1,2-dpe)}n (5). CP 1 forms a densely packed 3D framework with a rare topological type, ose; 7/3/o5; sqc59. Both CP 2 and 3 form [2+2] metallacyclic units which form a 1D chain that links other chains by strong O–H⋯N type H-bonding to result in a 3D supramolecular network. CP 4 forms a 2D sheet structure stacking over each other by C–H⋯π and π⋯π interactions, to give rise to a 3D H-bonded supramolecular structure with topological type, sql/Shubnikov. CP 5 has two types of SBUs with a 3D anionic network where channels are filled up with the cationic 1,2-dpe ligands and water molecules which shows rare topological type, 6,10T9. The photoluminescence sensing of nitroaromatic compounds, especially 2,4,6-trinitrophenol (TNP), by 1–5 indicates that these CPs could be potential candidates for developing luminescent sensors for selective sensing of these species.