Identification of Zr(iv)-based architectures generated from ligands incorporating the 2,2′-biphenolato unit

Abstract

The structural identification in solution of the Zr(IV) complexes involving two 2,2-biphenol-based proligands is reported. The proligand L¹H₂ contains one 2,2-biphenol unit whereas L²H₄ incorporates two 2,2-biphenol units linked by a para-phenylene bridge. Diffusion Ordered Spectroscopy (DOSY) combined with electrospray mass spectrometry analysis and density functional theory (DFT) allowed for determining the molecular structures of such Zr(IV)-based architectures. It is proposed that [Zr(OPrⁱ)₄(HOPrⁱ)] in the presence of L¹H₂ generates an octahedral complex formulated as [ZrL¹₃H₂]. Concerning the self-assembled architecture incorporating the L² ligand, the analytical data highlight the formation of an unprecedented neutral Zr(IV) triple-stranded helicate ([Zr₂L²₃H₄]). Insight into the geometry of these complexes is obtained via DFT calculations. Remarkably, the helicate structure characterized in solution strongly contrasts with the triple-stranded structure of the complex that crystallizes.