Highly Sensitive Fluorescent Sensing for Nitrobenzene of Cd II Complexes Based on Three Isomers and a Bis-Imidazole Ligand.

Detection of nitro pollutants is an important topic in environmental protection. A total of 3 Cd (II) complexes ( 1 - 3 ) based on 3 soft organic isomers, n-(3,5-dicarboxylato benzyloxy) benzoic acid ( n = 2, 3 or 4-H 3 DBB), and a linear N-donor ligand, 3-bis(imidazole-l-ylmethyl) benzene (3-bibz), have been synthesized hydrothermally. Structural diversity of Complexes 1 - 3 displays the architectural 2D or 3D change: Complex 1 exhibits a 2D network featuring tri-nuclear metal units, Complex 2 is a 3D framework based on similar tri-nuclear metal units, and Complex 3 shows a 3D network with binuclear units. Fluorescent sensing properties exhibited in all these complexes have been discovered to detect nitrobenzene (NB) selectively and sensitively. In particular, Complex 3 possesses high sensitivity for NB with the lowest detection limit of 1.15 × 10 -10 M. The results of the theoretical calculation verified the fluorescence detection mechanism of NB by these Cd-based complexes. Therefore, these Cd-based complexes might be used as excellent luminescent sensors for NB.