Living Supramolecular Polymerization of Ultrastable Kinetic Species of Ir(III) Complexes in Aqueous Media

Living supramolecular polymerization
(LSP) has become a key technology
for the progress of materials science. However, under the influence
of hydrophobic interaction, the precise kinetic control of LSP in
aqueous media is still challenging. In this work, we report a strategy
to realize the LSP of ultrastable kinetic species that is nearly impossible
to assemble spontaneously. Due to the strong hydrophobic interaction,
the kinetic species of Ir­(III) complex 2 (nanoparticles, 2NP) at 90 and 95% water contents can exist stably for more
than 50 days at room temperature. By mixing the seeds at an 85% water
content and the suspension of kinetic species at a 95% water content
in equal volume, LSP can be carried out at a 90% water content, and
multicycle LSP at a 90% water content can be performed successfully.
This LSP strategy broadens the practicality of LSP and is implemented
by structurally simple Ir­(III) complexes, which provides ideas for
broadening the monomer scope of LSP. Time-, temperature-, and concentration-dependent
spectroscopic results show that the formation of kinetic species 2NP and thermodynamic species 2NS (nanosheets)
follows the isodesmic model and the cooperative (nucleation–elongation)
model, respectively, and 2NP are the off-pathway intermediates
of 2NS. This study illustrates an ingenious and precise
kinetic control on the LSP in aqueous media.