4,5-Diamino-1,2-dihydropyridazine-3,6-dione-based layered Zn2+ coordination polymer and sensing properties on 2,4,6-trinitrophenol and Cr2O7 2

Highlights: • Structure of acylhydrazide-based Zn²⁺ coordination polymer was reported. • Acylhydrazide originated from in situ acylation of organic acid with N₂H₄. • It can selectively sensing 2,4,6-trinitrophenol. • (vi) It can also selectively sensing Cr₂O₇^2-. -- Abstract: By employing the hydrothermal in situ acylation of organic acid with N₂H₄, we constructed a new acylhydrazidate-based Zn²⁺ coordination polymer [Zn₂(apo)₂]·H₂O (H₂(apo) = 4,5-diamino-1,2-dihydropyridazine-3,6-diol) 1. Interestingly, besides the acylation of 2,3-pyrazinedicarboxylic acid (pca) with N₂H₄, the breaking of partial C-(=)N bonds in the pyrazine ring also occurred, creating a new bridging-type acylhydrazide molecule H₂(apo). In 1, the apo^2- molecules exhibit a μ₄ coordination mode, linking the tetrahedral Zn²⁺ centers into a 2-D layer network with a 4⁴ topology. The photoluminescence analysis indicates that the title compound 1 emit the green light with the maximum at 490 nm upon excitation (λ_ex = 380 nm, τ = 12.6 μs). Based on the better photoluminescence behavior of 1, the sensing ability of 1 on nitroaromatic explosives and inorganic anions were investigated. The results suggest that 1 can selectively detect 2,4,6-trinitrophenol (TNP) and Cr₂O₇^2-. This should be associated with the larger light adsorption at 380 nm for TNP and Cr₂O₇^2-. The light adsorption at 380 nm for the other nitroaromatic explosives and inorganic anions is weak.