Synthesis and selective detection towards TNP of two coordination polymers based on ligand generated by in situ acylation reaction

Abstract

2,4,6-Trinitrophenol (TNP), compared with the other nitro compounds, not only has a strong electron-withdrawing ability, but also has a strong light absorption capacity at a large excitation wavelength. Therefore, the fluorescence material with a large excitation wavelength might be a potential probe for the detection of TNP. Here, by employing the in situ acylation of organic acid with N2H4, two acylhydrazinotetracarboxylate-based coordination polymers [Cd2(HL1)(phen)2(H2O)]·4.5H2O (H5L1 ​= ​5,5′-(1,4-dioxo-1,2,3,4-tetrahydrophthalazine-6,7-diyl)bis(oxy)diisophthalic acid; phen ​= ​1,10-phenanthroline) 1 and [Mn2(HL1)(phen)2]·7H2O 2 were obtained. Phen is used to prevent the formation of a dense network and many hydrogen bonds, which might quench any emission of material. As predicted, 1 only possesses a 1-D broad-ribbon structure, whereas 2 just has a 1-D tube-like structure. And both are found to emit the yellow light, corresponding to the charge transfer from benzene ring moiety to acylhydrazine ring moiety. It means that the acylation changes thoroughly the photoluminescence behavior of organic ligand. Based on their good photoluminescence properties, the sensing ability of both towards TNP was investigated. It is turned out that 1 is not an ideal sensor, even though it can also sense TNP. However, 2 can be considered as an excellent sensor for the detection of TNP. The emission of 2 is almost completely quenched by TNP, while only 20% quenching is observed for the potential interfering analyte 4-nitroaniline (4-NA). The related sensing mechanism is discussed in details.