Self-assembly of a Pd8 macrocycle and Pd12 homochiral tetrahedral cages using poly(tetrazolate) linkers

Abstract

A two-dimensional molecular square () was obtained by the self-assembly of a bis(tetrazole) linker, 4,4'-bis(1-tetrazol-5-yl)-1,1'-biphenyl (H), with a square-planar metal acceptor [ = (tmeda)Pd(NO), where tmeda = ,,','-tetramethylethane-1,2-diamine] in dimethyl sulfoxide (DMSO) followed by crystallization. The uncommon 2,3-binding mode through N atoms of the tetrazole rings in this assembly leads to the formation of an octanuclear molecular square. The molecular square [Pd()(NO)] is unstable in DMSO and slowly converts to a dynamic mixture of a 3D tetrahedral cage [Pd()(NO)] and the macrocycle . A tetrahedral cage () is formed by the usual 1,3-binding mode of the tetrazole rings. However, self-assembly of the [Pd()(PF)] was possible to access in the pure form in a less polar solvent like acetonitrile. The pure [Pd()(PF)] also converts to a mixture of and in DMSO. Interestingly, when a tris(tetrazole) linker, tris(4-(1-tetrazol-5-yl)phenyl)amine (H), was treated with the acceptor , it produced a tetrahedral nanocage [Pd()(NO)] through 1,3-binding mode of the tetrazole rings without any trace of an octahedral cage through 2,3-binding mode of the tetrazole moieties