1 research outputs found
Dynamic Motions of Ligands around the Metal Centers Afford a Fidget Spinner-Type AIE Luminogen
A new type of aggregation-induced emission (AIE) luminogen
containing
a dimeric metal fragment and two or three phthalazine ligands is described,
which shows dynamic motions of ligands around the metal centers in
solution. Based on the variable-temperature and EXSY NMR spectroscopy
data, X-ray crystallography structures, and computational results,
three different pathways (i.e., reversible exchange with haptotropic
shifts, circulation of ligands around the dimeric metal fragment,
and walking on the spot of ligands on the metal centers) were considered
for this dynamic behavior. Restriction of these dynamic processes
in the aggregate forms of the compounds (in H2O/CH3CN solvent mixtures) contributes to their AIE. DFT calculations
and NMR analysis showed that bright excited states for these molecules
are not localized on isolated molecules, and the emission of them
stemmed from π-dimers or π-oligomers. The morphologies
and the mode of associations in the solvent mixtures were determined
by using transmission electron microscopy (TEM) and concentration-dependent
NMR spectroscopy. The computational results showed the presence of
a conical intersection (CI) between the S0 and S1 excited state, which provides an accessible pathway for nonradiative
decay in these systems