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

Abstract

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.