A Doughnut-Like (Mn^III)₁₂ Metallocycle Formed by a Rigid Angular Bis-Catecholate with a Nanometer-Sized Central Hole

Abstract

Reaction of the rigid angular ligand tetrahydroxy-9,10-dimethyl-9,10-dihydro-9,10-ethanoanthracene, hereafter LH4, with Mn(CH3CO2)2·2H2O in a basic aqueous medium, in air, affords a crystalline product of composition Na12{[Mn(H2O)]12L12}·xH2O. Single-crystal X-ray diffraction reveals the presence of large [MnIII12L12]12− metallocycles of roughly hexagonal appearance, somewhat resembling a doughnut in which the central hole (van der Waals surface to surface) is roughly a nanometer across. This is the first example of a metal derivative of the fully deprotonated form, L4−. Associations with aquated Na+ counterions lead to a pleasingly symmetrical packing arrangement resembling honeycomb, with the central holes of individual metallocycles lined up one above the other. The ligand L4−, on account of its rigid angularity and its strong metal binding properties, promises to provide a rich source of unusual metal-containing structures, in particular cages, in future studies