Ten polytorsional-amide-induced helical-based coordination polymers with difunctional electrochemical activities

Abstract

To investigate the synergistic coordination ability of a polytorsional-amide ligand to construct new coordination polymers (CPs), N,N′-bis(4-methylpyridin-4-yl)-1,4-naphthalenediamide (L) was selected as the main ligand. Ni²⁺ and Cu²⁺ with electrochemical activity and different carboxylates [2-nitrobenzoic acid (2-HNBA), 4-nitrobenzoic acid (4-HNBA), p-toluic acid (HPTA), 1,2-benzenedicarboxylic acid (1,2-H₂BDC), pimelic acid (H₂PIM), 1,3-phenylenediacetic acid (H₂PDA), o-methylsalicylic acid (HOMSA), propanedioic acid (H₂PRO) and azelaic acid (H₂AZE)] have been selected, and ten new CPs were obtained: [Ni(L)₂(2-NBA)₂] (1), [Ni(L)(4-NBA)₂(H₂O)₂] (2), [Ni(L)(PTA)₂(H₂O)₂] (3), [Ni(L)(1,2-BDC)(H₂O)₃]·H₂O (4), [Ni(L)(PDA)]·0.5H₂O (5), [Ni(L)(PIM)]·0.5H₂O (6), [Cu(L)(4-NBA)₂] (7), [Cu(L)(OMSA)₂(H₂O)] (8), [Cu(L)(PRO)(H₂O)]·3H₂O (9) and [Cu(L)(AZE)(H₂O)] (10). The ten CPs were structurally determined through single-crystal X-ray diffraction analyses, PXRD and IR spectra. 1, 5, 6 and 10 are the 4-connected 2D networks. 2 and 3 are similar racemic chains. 4 and 7 are 1D helical structures. 8 is a zigzag chain and 9 is a “U” type chain. The effects of the twist degrees of the amide ligands and the coordination features of the carboxylates/metal ions on the structures and properties of the target CPs were investigated. 1–10 modified carbon paste electrodes (n-CPEs) display a quasi-reversible oxidation–reduction process at the surface of the n-CPE. Representative CPs (2, 5, 7 and 10) show good electrochemical sensing properties for ascorbic acid (AA) and chloramphenicol (CAP).