<i>o</i>‑Carboranyl–Phosphine
as a New Class of Strong-Field Ancillary Ligand in Cyclometalated
Iridium(III) Complexes: Toward Blue Phosphorescence
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Abstract
Heteroleptic
tris-cyclometalated Ir(III) complexes supported by
the <i>o</i>-carboranyl–phosphine ligand (<i>CBP</i>), (C<sup>∧</sup>N)<sub>2</sub>Ir(<i>CBP</i>) (C<sup>∧</sup>N = <i>ppy</i> (<b>1</b>), <i>dfppy</i> (<b>2</b>)), have been synthesized and characterized.
The PL spectra of <b>1</b> and <b>2</b> displayed substantially
blue shifted phosphorescence relative to the corresponding Ir(C<sup>∧</sup>N)<sub>3</sub> complexes. Electrochemical and theoretical
studies showed that the <i>CBP</i> ligand functioned as
a strong-field ancillary ligand, and the greater HOMO stabilization
in comparison to that of the LUMO by the <i>CBP</i> ligand
was responsible for the increase in band gap, leading to a large blue
shift in phosphorescence