An Unprecedented Family of Luminescent Iridium(III) Complexes Bearing a Six-Membered Chelated Tridentate C^N^C Ligand

A new family consisting
of three luminescent neutral Ir­(III) complexes
with the unprecedented [Ir­(C^N^C)­(N^N)­Cl] architecture, where C^N^C
is a bis­(six-membered) chelating tridentate tripod ligand derived
from 2-benzhydrylpyridine (bnpy) and N^N is 4,4′-di-tert-butyl-2,2′-bipyridine (dtBubpy),
is reported. X-ray crystallography reveals an unexpected and unusual
double C–H bond activation of the two distal nonconjugated
phenyl rings of the bnpy coupled with a very short Ir–Cl bond trans to the pyridine of the bnpy ligand. Depending on the
substitution on the bnpy ligand, phosphorescence, ranging from yellow
to red, is observed in dichloromethane solution. A combined study
using density functional theory (DFT) and time-dependent DFT (TD-DFT)
corroborates the mixed charge-transfer nature of the related excited
states.