Design and synthesis of polynuclear gold(I) clusters and gold(I) cluster cages : from cluster-to-cluster transformation to cluster-to-cage evolution

Abstract

A series of polynuclear gold(I) sulfido complexes with bis(diphenylphosphino)-amine (PNP) ligands has been synthesized and characterized. Intriguingly, a systematic decrease in the steric effect of the PNP ligands has dictated the nuclearity of the polynuclear gold(I) sulfido complexes, ranging from decanuclear to dodecanuclear gold(I) sulfido complexes. Moreover, one of the dodecanuclear gold(I) sulfido complexes showed reversible concentration-modulated cluster-to-cluster transformation between a hexanuclear gold(I) sulfido complex and a dodecanuclear gold(I) sulfido complex. The transformation process has been monitored not only by 1H and 31P{1H} NMR spectroscopy but also by UV−vis absorption spectroscopy and high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) in the solution state. The present work has offered a simple approach to achieve structural modulation of gold(I) sulfido complexes by fine-tuning the substituent groups on the PNP ligands. The occurrence of the interconversion has provided a system for the study and understanding of supramolecular transformations in polynuclear gold(I) systems under the application of external stimuli.

A novel series of luminescent polynuclear gold(I) sulfido complexes has been constructed by employing chlorogold(I) precursors based on 1,3-bis(diphenylphosphino)benzene ligands. These gold(I) sulfido complexes with distinct structures have been fully characterized. Interestingly, an unprecedented substituent-mediated transformation from pentagold(I) to octadecagold(I) complexes has been observed. The transformation process has been monitored by NMR spectroscopy in solution state. It was found that the electron-withdrawing substituent on the benzene core of 1,3-bis(diphenylphosphino)benzene was of vital importance for the regulation of the cluster transformation process. The present findings offered a simple and effective cluster-to-cluster transformation strategy for the development of novel luminescent gold(I) sulfido complexes with controlled structures by varying the electronic nature of the substituent on the phosphine ligand.

An unprecedented class of gold(I) cluster cages has been obtained through “de-aurophilic” interaction strategy by using the judiciously designed diphosphine ligand based on the V-shaped 1,3-bis(diphenylphosphino)benzene ligand with 2-phenyl substituent, as the organic building block. These gold(I) cluster cages adopted [(μ3-S)Au3]+ units as the vertices of a polyhedral architecture. The tetracosanuclear gold(I) cluster cages with PF6- or BF4- counter-ions were found to display structural transformation from a cube to a rhombic prism during the crystallization process. The structure could be recovered upon dissolution. More interestingly, a reversible thermally responsive structural interconversion between the cube and the triangular prism form was observed. The transformation process has been monitored by NMR and UV−vis spectroscopy as well as HR-ESI-MS in solution state. The present findings have paved the way to the development of novel classes of gold(I) cluster cages with distinct structure-related properties.