Biasing the Formation of Solution‐Unstable Intermediates in Coordination Self‐Assembly by Mechanochemistry

Abstract

Abstract Due to the reversible nature of coordination bonds and solvation effect, coordination self‐assembly pathways are often difficult to elucidate experimentally in solution, as intermediates and products are in constant equilibration. The present study shows that some of these transient and high‐energy self‐assembly intermediates can be accessed by means of ball‐milling approaches. Among them, highly aqueous‐unstable Pd 3 L1 1 and Pd 6 L1 4 open‐cage intermediates of the framed Fujita Pd 6 L1 4 cage and Pd 2 L2 2 , Pd 3 L2 1 and Pd 4 L2 2 intermediates of Mukherjee Pd 6 L2 4 capsule are successfully trapped in solid‐state, where Pd =tmedaPd 2+ , L1 =2,4,6‐tris(4‐pyridyl)‐1,3,5‐triazine and L2 =1,3,5‐tris(1‐imidazolyl)benzene). Their structures are assigned by a combination of solution‐based characterization tools such as standard NMR spectroscopy, DOSY NMR, ESI‐MS and X‐ray diffraction. Collectively, these results highlight the opportunity of using mechanochemistry to access unique chemical space with vastly different reactivity compared to conventional solution‐based supramolecular self‐assembly reactions.