Metalation-induced skeletal rearrangement of N-confused bilatriene analogs exhibiting intense near-infrared absorption

Using aerobic conditions, a hitherto unknown N-confused bilatrienone analog (1-o) was synthesized through the metal-induced oxidative rearrangement of the N-confused bilatriene (1). The resulting metal complexes (Pd1-o; M = Pd and Pt1-o; M = Pt) were characterized by NMR spectroscopies, mass spectrometry, and single crystal X-ray diffraction analysis, showing the regioselective oxygenation and 2,3-shift of the methylene linkage of the terminal indole moiety. Due to the helically [Formula: see text]-conjugated structure of the complexes, Pd1-o and Pt1-o, uniquely intense absorption bands in the near-infrared (NIR) region have emerged, respectively, which were assigned to be HOMO-LUMO transitions based on the time-dependent DFT calculations. Along with the non-emissive nature of the complexes, the efficient photothermal conversion capabilities were demonstrated in the toluene solution. Therefore, these complexes could potentially be used in photothermal therapies for biological tissues.