Near-Infrared-III-Absorbing and -Emitting Dyes: Energy-Gap Engineering of Expanded Porphyrinoids via Metallation.

The synthesis of organometallic complexes of modified 26π-conjugated hexaphyrins with absorption and emission capabilities in the third near-infrared region (NIR-III) is described. Symmetry alteration of the frontier molecular orbitals (MOs) of bis-Pd and bis-Pt complexes of hexaphyrin via N-confusion modification led to substantial metal d -p interactions. This MO mixing, in turn, resulted in a significantly narrower HOMO-LUMO energy gap.