Neutral and cationic palladium(II) and platinum(II) complexes of 2,2′-dipyridylamine with saccharinate: Syntheses, spectroscopic, structural, fluorescent and thermal studies

Four palladium(II) and platinum(II) complexes of 2,2′-dipyridylamine (dpya) with saccharinate (sac), cis-[Pd(dpya)(sac)2]·H2O (1), cis-[Pt(dpya)(sac)2]·H2O (2), [Pd(dpya)2](sac)2·2H2O (3) and [Pt(dpya)2](sac)2·2H2O (4), have been synthesized and characterized by elemental analysis, IR, NMR, TG-DTA and X-ray diffraction. In 1 and 2, the metal ions are coordinated by two N-bonded sac ligands, and two nitrogen atoms of dpya, resulting in a neutral square-planar coordination sphere, while in 3 and 4, the metal ions are coordinated by two dpya ligands to generate square-planar cationic species, which are stabilized by two sac counter-ions. The mononuclear species of 1 and 2 interact each other through weak intermolecular N–H⋯O, C–H⋯O and π⋯π interactions to form a three-dimensional network, while the ions of 3 and 4 are connected by N–H⋯N and OW–H⋯O hydrogen bonds into one-dimensional chains. On heating at 250 °C, the solid cationic complexes of 3 and 4 convert to corresponding anhydrous neutral complexes of 1 and 2 after elimination of a dpya ligand. In addition, all complexes 1–4 are luminescent at room temperature and their emissions seem to be attributed to the MLCT fluorescence.