Just Add the Gold: Aggregation-Induced-Emission Properties of Alkynylphosphinegold(I) Complexes Functionalized with Phenylene–Terpyridine Subunits

A series
of organometallic complexes containing an alkynylphosphinegold­(I)
fragment and a phenylene–terpyridine moiety connected together
by flexible linker have been prepared using the specially designed
terpyridine ligands. The compounds were studied crystallographically
to reveal that all of them contain a linearly coordinated Au­(I) atom
and a free terpyridine moiety. The different orientations of the molecules
relative to each other in the solid state determine the multiple noncovalent
interactions such as antiparallel ππ stacking, CH−π,
and CH–Au, but no aurophilic interactions are realized. The
organometallic Au­(I) complexes obtained show fluorescence in the solution
and dual singlet–triplet emission in the solid state. This
means that their photophysical behavior is determined by both intermolecular
lattice-defined interactions and Au­(I) atom introduction. Density
functional theory computational analysis supported the assignment
of emission to intraligand electronic transitions only inside the
phenylene–terpyridine part with no Au­(I) involved. In addition,
a study of the nature of the excited states for the “dimer”
with an antiparallel orientation of the terpyridine fragment showed
that this orientation leads to the generation of abstracted singlet
and triplet states, lowering their energy in comparison with the monomer
complex. Thus, the complexes obtained can be qualified as examples
of Au­(I)-containing organometallic aggregation-induced-emission luminogens.