Fluorosolvatochromism of Platinum Supramolecular Coordination Complexes: Stepwise Synthesis and Photophysical Properties of Organometallic Tetranuclear Pt(II) Squares

The stepwise synthesis and characterization of three new mixed-ligand organometallic tetranuclear platinum squares were achieved. All of the complexes were constituted by the conjunction of two (2,2′-bpy)Pt-terph-Pt(2,2′-bpy) (terph = p-terphenyl) fragments linked by a variety of N^N ligands (4,4′-bipyridine (4,4′-bpy), 1,4-di(pyridin-4-yl)benzene (dpbz), and 4,4′-di(pyridin-4-yl)-1,1′-biphenyl (dpbph)), which occupied the fourth coordination site of each metal center, giving rise to square-shaped molecules of the general formula [Pt2(2,2′-bpy)2(terph)(N^N)]2. Consequently, the tetranuclear complexes, {[Pt(2,2′-bpy)]4(μ-terph)2(μ-4,4′-bpy)2}{PF6}4 (7), {[Pt(2,2′-bpy)]4(μ-terph)2(μ-dpbz)2}{PF6}4 (8), and {[Pt(2,2′-bpy)]4(μ-terph)2(μ-dpbph)2}{PF6}4 (9) were constructed. The photophysical properties of these complexes were studied both in the solid state and in various solvents, revealing fluorosolvatochromism.