In this work we report that covalent postsynthetic modification can be used for the preparation of a class of bis-cylometalated iridium complexes featuring Chugaev-type chelating dicarbene ligands. Bis-cyclometalated iridium complexes with electron deficient aryl isocyanide ancillary ligands react smoothly with hydrazine to form neutral dicarbene complexes. The neutral iridium carbene complexes have a basic site which can be protonated by strong acid, permitting access to complexes in two protonation states and allowing an additional layer of control over the key properties. Compared to their bis-isocyanide precursors, the electrochemical and photophysical properties of these new complexes are substantially perturbed, demonstrating the concept that the electronic structure and excited state dynamics can be controlled by ancillary ligand modification. Furthermore, the emission spectra and excited-state dynamics are dependent on the protonation state of the dicarbene ancillary ligand, which provides an additional means of controlling these properties. This work demonstrates a conceptual advance in the design of new bis-cyclometalated iridium phosphors, where inherent ligand-based reactivity can be leveraged to give rise to new structures that cannot be prepared using typical synthetic approaches.

Bis-cyclometalated iridium complexes with chelating dicarbene ancillary ligands

255th National Meeting (2018)

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