Water dispersible supramolecular assemblies built from luminescent hexarhenium clusters and silver(I) complex with pyridine-2-ylphospholane for sensorics

The work introduces regularities and driving forces of self-assembly of hexarhenium clusters [{Re6S8}L6]n− (L = SO32−, CN−, OH−) with [AgL′]+ (L′ = pyridine-2-ylphospholane) produced by dissociation of [Ag2L′2]2+ in aqueous solutions. The formation of nano-sized Re6 Ag assemblies is detected by the spectral measurements in the solutions and by the solid-state analysis of the separated colloids. The nature of L is highlighted as the main factor affecting the assembly. The poor affinity of the SO32− ligands to Ag+ restricts the assembly of [{Re6S8}(SO3)6]10− with the silver(I) complexes. [{Re6S8}(OH)6]4− is more promising candidate for the heterometallic assembly contributed by both counter-ion binding and coordination bonds, while the efficient coordination of Ag+ via the nitrogen of the cyanide ligands of [{Re6S8}(CN)6]4− is the main driving force for the Re6 Ag assembly. The stronger impact of [Ag2L′2]2+ relative to Ag+ cations on the formation of Re6 Ag assemblies in aqueous solutions, as well as the presence of L′ in the separated colloidal phase, indicate the important role of the L′ ligand in the studied supramolecular systems. The cluster-centered luminescence serves as signaling system at the binding of glutathione, cysteine and dithiothreitol with Ag+ ions of the heterometallic assemblies. The assemblies based on [{Re6S8}(CN)6]4− are able to discriminate glutathione versus cysteine, while the assemblies formed by [{Re6S8}(OH)6]4− give the unselective luminescence response on the both biothiols at the concentration level of 2 μM.