Giant Electroactive M₄L₆ Tetrahedral Host Self-Assembled with Fe(II) Vertices and Perylene Bisimide Dye Edges

Abstract

Self-assembly of octahedral Fe­(II) ions and linear perylene bisimide (PBI) dyes with 2,2′-bipyridine groups covalently attached at the imide positions quantitatively yields an Fe₄(PBI)₆ tetrahedron by the directional bonding approach. With an edge length of 3.9 nm and estimated internal volume >950 ų, tetrahedron <b>T</b> is one of the largest M₄L₆ tetrahedra ever reported. Importantly, many of the desirable photo- and electroactive properties of the PBI ligands are transferred to the nanoscale metallo­supra­molecule. Tetrahedron <b>T</b> absorbs strongly across the visible spectrum out to 650 nm and exhibits a total of 7 highly reversible electrochemical oxidation and reduction waves spanning a 3.0 V range. This facile cycling of 34 electrons between +18 and −16 charged species is likely enabled due to the porous nature of the tetrahedron that allows the necessary counterions to freely flow in and out of the host. Host–guest encapsulation of C₆₀ by <b>T</b> in acetonitrile was studied by ¹³C NMR spectroscopy, UV–vis spectroscopy, and ESI-MS, confirming that the tetrahedron is a suitable host for large, functional guest molecules