Syntheses, structures and properties of four second-sphere coordination complexes via metal halide anion and naphthalene-based ligand

<div><p>Second-sphere coordination refers to any intermolecular interactions with the ligands directly bound to the primary coordination sphere of a metal ion. Four supramolecular complexes, 0.5[L·2H]²⁺·0.5[MCl₄]²⁻·[CH₃OH]·0.5[CH₂Cl₂] (M = Co, crystal <b>1</b>; M = Mn, crystal <b>2</b>), 0.5[L·2H]²⁺·0.5[ZnBr₄]²⁻·[CH₃OH]·0.5[CH₂Cl₂] (crystal <b>3</b>), and 0.5[L·2H]²⁺·0.5[Cu₂Br₄]²⁻·H₂O (crystal <b>4</b>), based on naphthalene-based ligand N,N,N′,N′-tetra-p-methylnaphthyl-ethanediamine (<b>L</b>), have been synthesized. X-ray analysis reveals that <b>1–3</b> are isostructural, in which the methanol molecules are bridges, connecting the protonated <b>L</b> and metal chloride anions via N–H⋯O and O–H⋯Cl (Br) interactions to construct the host framework, and forming X-shaped cavity accessible for the inclusion of weakly polar guest molecules of dichloromethane. Dichloromethane is connected with the host framework through van der Waals forces. In <b>4</b>, a dinuclear anion [Cu₂Br₄]²⁻ is connected with the ligand through N–H⋯Br interactions, in which the water molecules are accommodated between chains formed by the ligand and [Cu₂Br₄]²⁻. Structure stability, thermal analysis, and photoluminescent properties were studied for <b>1–4</b>.</p>