Coordination polymers constructed from bis-pyridyl-bis-amides and 1,4,5,8-naphthalenetetracarboxylic acid: ligand transformation and metal ion sensing†

Abstract

Hydrothermal reactions of 1,4,5,8-naphthalenetetracarboxylic acid (1,4,5,8-H₄NTC) with various bis-pyridyl-bis-amides, N,N′-di(pyridin-3-yl)adipamide (L¹), N,N′-di(pyridin-3-yl)succinamide (L²), N,N′-di(pyridin-3-yl)oxalamide (L³) or N,N′-bis(pyridin-3-ylmethyl)oxalamide (L⁴) and transition metal salt afforded seven coordination polymers (CPs) and one dinuclear complex, including [Cd(L¹)_0.5(1,4,5,8-NTC′)(H₂O)₂]_n (1,4,5,8-H₂NTC′ = 1,4,5,8-naphthalenetetracarboxylic acid 1,8-monoanhydride), 1, {[Zn(L²)_0.5(1,4,5,8-NTC′)(H₂O)₂]·H₂O}_n, 2, {[Cd(L²)_0.5(1,4,5,8-NTC′)(H₂O)₂]·H₂O}_n, 3, {[Zn(L⁵)(1,4,5,8-NTC′)(H₂O)]·0.5OA}_n, {L⁵ = 2,7-di(pyridin-3-yl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone}, 4, [Cd(L⁵)(1,4,5,8-NTC′)(H₂O)]_n, 5a, {[Cd(L⁵)(1,4,5,8-NTC′)(H₂O)]·2H₂O}_n, 5b, [Zn₂(L⁴)(1,4,5,8-NTC′)₂(H₂O)₆], 6, and {[Cd(L⁴)(1,4,5,8-NTC)_0.5(H₂O)]·0.5H₂O}_n (1,4,5,8-H₄NTC = 1,4,5,8-naphthalenetetracarboxylic acid), 7. These CPs and the dinuclear complex were structurally characterized by using X-ray single-crystal diffraction. CPs 1, 2, and 3 exhibit one-dimensional (1D) structures with the 2,3C2 topology and 4 and 5 display two-dimensional (2D) structures with the 2,4L1 topology, whereas 6 is a dinuclear complex and 7 shows a three-dimensional (3D) framework with the mog topology. Ligand transformations from 1,4,5,8-H₄NTC to 1,4,5,8-NTC′²⁻ and L³ to L⁵ are observed. The evaluation of the metal ion sensing properties of 1, 2, 3, 6, and 7 shows that 7 has the highest potential for detecting Fe³⁺ ions in aqueous solution with 1.06 × 10³ M⁻¹ and 1.99 × 10⁻⁴ M for the Stern–Volmer constant (K_SV) and the limit of detection (LOD), respectively.