Exploring the sensing behavior in the detection of nitroaromatics using coordination complexes based on 4,4′-(1,3-phenylenedioxy)-dianiline ligand

The aromatic ligand 4,4'-(1,3-phenylenedioxy)-dianiline (L), has been used to explore its coordination chemistry behaviour and nitroaromatic sensing ability by crystallizing it with a variety of transition metals. The supra molecular structures [CuCl2(L)] (1), [Mn(H2O)(2)Cl-2(L)2] (2), [Ni(H2O)(2) (L)(2)] Cl-2 (3) and [Co(H2O)(2) (L)(2)] Cl-2 (4) have been characterized by single crystal X-ray diffraction (SC-XRD) and X-ray powder diffraction (XRPD) analysis. While 1 and 2 do not form polymeric structures but discrete (0D) arrays, 3 and 4 resulted in extended isostructural 2D coordination polymers. The solid-state fluorescence properties of the reported crystals have been investigated. Interestingly, coordination polymers 3 and 4 showed a better solid-state fluorescence emission compared to that of complexes 1 and 2. Coordination polymer 3 has been successfully used as a sensor for the detection of trace amounts of nitrobenzene, 2-nitrotoluene and 3-nitrotoluene with a high quenching efficiency of 96% for 3-nitrotoluene. The quenching efficiency of 3 is better than that of the free ligand L. The polymeric nature of 3 is maintained after the sensing experiment and thus can be used in a recyclable manner. Due to the fact that 3 is a nonporous and its structure does not change in the presence of the quenchers, the quenching effect occurs in the surface of the solids when is in a suspension.