Two Water-Stable Zn(II) Coordination Polymers as Luminescent Sensors for Detection of Uric Acid in Serum, MnO₄^–, and Cr(VI) Oxo-Anions in Tap Water

Abstract

Two novel coordination polymers (CPs), [Zn2(μ-OH)2(μ-1,5-NDS-κ2 O:O′)(μ-Mbimb-κ2 N:N′)] n (1) and {[Zn(CH3COO-κ1 O)(μ-bbimb-κ2 N:N′)1.5](1,5-NDS)0.5} n (2), were synthesized by hydrothermal reaction of Zn(Ac)2·2H2O with 1,5-naphthalenedisulfonate (1,5-NDS2–), 1,4-bis(2-methyl-1H-imidazole-1-yl)butane (Mbimb), or 1,4-bis(1H-benzimidazol-1-yl)butane (bbimb). In the crystal structure of 1, the Zn(II) centers are connected by μ-OH– anions into an infinite –[Zn(OH)] n – chain, which is further linked by Mbimb and 1,5-NDS2– to form a 3D dia network. In 2, the Zn(II) centers are linked by bbimb ligands into a 2D (6,3) brick wall layer with Ac– as dangling arms threaded into the space of adjacent layers, resulting in a 2D → 3D polythreading structure. Luminescent studies reveal that both CPs have excellent luminescence stability and can selectively detect uric acid (UA), MnO4 –, and Cr(VI) oxo-anions in aqueous solutions with high quenching efficiency. The limits of detection toward UA, MnO4 –, CrO4 2–, and Cr2O7 2– are 0.46, 4.33, 5.50, and 1.60 μM for CP 1 and 5.63, 2.84, 7.60, and 2.90 μM for CP 2, respectively. Moreover, the two CPs can also serve as luminescence sensors to detect UA in serum and MnO4 – and Cr(VI) oxo-anions in tap water. The luminescent films of the CPs were also prepared for visual detection of UA, MnO4 –, CrO4 2–, and Cr2O7 2– with the naked eye.