Construction of zirconium/hafnium-oxo clusters based on a new protection-calix[8]arene

Abstract

Calix[8]arene has been used as a promising type of macrocyclic ligand for the construction of multinuclear metal-oxo clusters (MOCs), but not for zirconium/hafnium-oxo clusters (Zr/HfOCs). In this paper, we report the first series of ZrOCs (HfOCs) based on calix[8]arene: Zr₄, Zr₈, Hf₄, and Hf₈. Zr₈/Hf₈ has a rhombohedral conformation and can be regarded as a derivative of the octahedral Zr₆ cluster. Remarkably, I₂ adsorption experiments indicate that Zr₄ (Zr₈) adsorbs much faster than Hf₄ (Hf₈). Density functional theory (DFT) calculations show that metallic Zr atoms interact more strongly with I₂ than metallic Hf atoms. The successful application of calix[8]arene for the synthesis of well-defined ZrOCs (HfOCs) shows a bright future for MOCs protected by macrocyclic ligands.