Heterometallic Coinage Metal Acetylenediide Clusters Showing Tailored Thermochromic Luminescence.

Acetelyenediide (C2 2- ) species have been encapsulated in bimetallic and trimetallic clusters: [(AuL)6 Ag7 (C≡C)3 ](BF4 )7 (2) and [(AuL)6 AgCu6 (C≡C)3 ](BF4 )7 (3), L=phenylbis(2-pyridyl)phosphine (PPhpy2 ). Single-crystal X-ray diffraction analysis revealed that they are isostructural and six silver atoms in 2 are replaced with copper in 3. Both clusters have a trefoil skeleton, which can be viewed as three trigonal bipyramidal (LAu-C≡C-AuL)M2 Ag (M=Ag/Cu) motifs sharing a common silver atom. TDDFT calculations showed Cu-doping significantly increases the energy level of (C2 -Cu)-involved occupied orbital, thus inducing interesting transition coupling of dual-emission at low temperature. This work not only provides a strategy for constructing heterometallic clusters, but also shows the prospect for pursuing novel thermochromic luminescent materials by incorporating multi-congeneric metal components.