In situ ligand formation-driven synthesis of two acylhydrazide compounds: Synthesis, structure and photoluminescence properties

In situ ligand synthesis has evolved as an effective method for the preparation of novel organic molecules and coordination polymers. In this report, one novel acylhydrazidate-based coordination polymer [Pb(PMDH)] 1 and a new organic acylhydrazide molecule [PMDH] 2 (PMDH = pyromellitdihydrazide) have been isolated, in which the PMDH molecule was generated via in situ acylation reaction between pyromellitic acid and N2H4. X-ray single-crystal diffraction analysis reveals that in compound 1, PMDH I molecules link the Pb2+ centers into a two-dimensional (2-D) layer, and then PMDH II molecules extend these layers into a three-dimensional (3-D) network with the point (Schläfli) symbol of (412·63). Compound 2 selfassembles into a 3-D supramolecular network through weak interactions as hydrogen-bonding and π⋯π stacking. The structures, CHN analysis, IR analysis of both compounds were researched. Thermal stability and solid-state photoluminescence property of 1 were intensively investigated. Compound 1 emits orange-red phosphorescence in the solid state at ambient conditions, with a quantum yield of 3% and a double exponential functioned phosphorescence lifetime of τ1 = 23.2 μs (36%), τ2 = 81.4 μs (64%). Compound 2 has a blue light fluorescence emission with a quantum yield of 2%.