Synthesis of a Black Dye with Absorption Capabilities Across the Visible-to-Near-Infrared Region: A MO-Mixing Approach via Heterometal Coordination of Expanded Porphyrinoid

An
expanded metalloporphyrin-based “black dye” Au–Pd
oxohexaphyrin (AuPd-1) with absorption capabilities across
the visible-to-near-infrared (NIR) range was synthesized. This black
dye, AuPd-1, possessed efficient light-harvesting and
photostable capabilities, which were indicative of superior photothermal
(PT) conversion abilities. Encapsulation of AuPd-1 with
a micellar nanocapsule resulted in a compound that demonstrated intense
photoacoustic (PA) properties in the NIR region in water. This finding
indicated how metal (d)–ligand (π) molecular orbital
interactions in metalloporphyrins could aid in the design of visible-to-NIR
light-harvesting black dyes for PT and PA applications.