Synthesis and Photothermal Properties of Mn(III) Complexes with Carbazole-Bridged Bis-NHC Ligands

Photothermal conversion has found broad applications ranging from biomedicine to chemical synthesis; however, the development of stable, non-noble metal photothermal agents remains a significant challenge. Herein, we report a class of mononuclear Mn(III) complexes bearing carbazole-bridged N-heterocyclic carbene (NHC) ligands (Mn-1–Mn-3). The carbazole-bridged bis-NHC framework affords tunable visible-light absorption, with Mn-3 exhibiting the most pronounced absorption in the long-wavelength visible region. Mn-3 shows good photothermal performance, reaching a temperature of 76 °C under 635 nm irradiation. Furthermore, we demonstrate the utility of Mn-3 as a photothermal catalyst for the C–N coupling of bromobenzene and pyrrolidine. This work not only presents a rare example of manganese-based molecular photothermal agents but also highlights a viable strategy for utilizing earth-abundant manganese complexes in photothermally driven organic synthesis.