Crowning of Coinage Metal Pyrazolates: Double-Decker Homo- and Heteronuclear Complexes with Synergic Emissive Properties

A new pyrazole ligand with flexible
thioether chelate arms was synthesized and was used to obtain an unprecedented
class of hexanuclear coinage metal complexes of general formula [MM′L]3Y3 (M, M′ = Cu, Ag, Au; Y = OTf, BF4). Three of them were characterized by X-ray crystallography,
namely, homometallic [Ag2L]3(OTf)3 and [Ag2L]3(BF4)3 as
well as heterometallic [CuAgL]3(OTf)3, revealing
that the classical [M­(μ-pz)]3 core is crowned by
a second deck of S-bound M′ ions. Depending on the solvent,
these oligonuclear systems undergo rapid dynamics and show cation–anion
aggregation in solution, which has been investigated by DOSY and temperature
dependent NMR spectroscopy. Preliminary luminescence data for selected
hexametallic [MM′L]3Y3 complexes show
that the combination of ligand-directed intramolecular and supramolecular
d10 metal ion interactions in the solid state gives rise
to synergic emissive properties that allow for a selective addressing
of different emission wavelengths.