4,5-Diazafluorene-9-one Acylhydrazones and Their Lead(II) Complexes and the Crystal Structure of Hydrated 4,5-Diazafluorene-9-one 3-Methoxybenzoylhydrazone Supported by Extensive Hydrogen Bonds and Aromatic Ring Stacking Interactions

4,5-Diazafluorene-9-one acylhydrazone ligands: 4,5-diazafluorene-9-one 3-methoxy benzoylhydrazone (HL), 4,5-diazafluorene-9-one 2-thiopheneacetylhydrazone (HL) and 4,5-diazafluorene-9-one isonicotinoylhydrazone (HL) and their Pb(II) complexes PbL 2 1 2H2O 1, PbL (OAc) 2 and PbL 2 3 3 have been prepared and characterized by elemental analyses, molar conductivities, IR and H NMR spectroscopy. In all the complexes, the mononegative ligand chelates to the lead ion through the enolic oxygen and the azomethine nitrogen atoms forming a 5-membered chelate ring. An X-ray diffraction analysis on HL 2H2O shows that it exists in the keto form and each HL 1 molecule forms five hydrogen bonds with neighbouring four water molecules through two diazafluorene N, one carbonyl O, one azomethine N and one amide H atom. The hydrogen bonds together with aromatic stacking interactions between the phenyl and the diazafluroene ring and between the diazafluorene rings assemble the molecules into a two-dimensional network.