Self-assembly of metallomacrocycles with dipyrazole ligands and anion sensing of [Pd4Fe2] macrocycle with ferrocene-based dipyrazole ligand

Abstract

By employing dipalladium corners [(bpy)₂Pd₂(NO₃)₂](NO₃)₂ or [(phen)₂Pd₂(NO₃)₂](NO₃)₂ (where bpy = 2,2′-bipyridine and phen = 1,10-phenanthroline) to bridge ferrocene-based dipyrazole ligand (L¹1) and m-phenylene-based dipyrazole ligands (L^2–32–3) in aqueous solution, a series of positively-charged [M₄L₂]⁴⁺ metallomacrocycles were obtained. Their structures were characterized by ¹H NMR, electrospray ionization mass spectrometry (ESI-MS), elemental analysis, and single crystal X-ray diffraction analysis for 1·4NO₃ ({[(bpy)Pd]₄L¹1₂}(NO₃)₄) and 4·4NO₃ ({[(phen)Pd]₄L²2₂}(NO₃)₄). In their single crystal structures, NO₃⁻ anions are located at the dipalladium corners by C–H⋯O hydrogen bonds. Importantly, the anion-sensing properties of ferrocene functionalized [Pd₄Fe₂] hetero-metallomacrocycle 1 were investigated in acetonitrile by SWV, CV and NMR analysis, showing promise for Br⁻ sensing.