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Sheet-like 2D Manganese(IV) Complex with High Photothermal Conversion Efficiency.

Ye XuChao LiXiaoyu WuMing-Xing LiYunsheng MaHong YangQing-Dao ZengJonathan L SesslerZhao-Xi Wang
Published in: Journal of the American Chemical Society (2022)
We report a stable, water-soluble, mononuclear manganese(IV) complex [Mn IV (H 2 L )]·5H 2 O (Mn-HDCL) that acts as an efficient photothermal material. This system is based on a hexahydrazide clathrochelate ligand ( L /HDCL) and is obtained via an efficient one-pot templated synthesis that avoids the need for harsh reaction conditions. Scanning tunneling microscopy images reveal that Mn-HDCL exists as a 2D sheet-like structure. In Mn-HDCL, the manganese(IV) ion is trapped within the cavity of the cage-like ligand. This effectively shields the Mn(IV) ion from the external environment while providing adequate water solubility. As a result of orbital transitions involving the coordinated manganese(IV) ion, as well as metal-to-ligand charge transfer effects, Mn-HDCL possesses a large extinction coefficient and displays a photothermal performance comparable to single-wall carbon nanotubes in the solid state. A high photothermal conversion efficiency (ca. 71%) was achieved in aqueous solution when subjected to near-infrared 730 nm laser photo-irradiation. Mn-HDCL is paramagnetic and provides a modest increase in the T 1 -weighted contrast of magnetic resonance images both in vitro and in vivo . Mn-HDCL was found to target tumors passively and allow tumor margins to be distinguished in vivo in a mouse model. In addition, it also exhibited an efficient laser-triggered photothermal therapy effect in vitro and in vivo . We thus propose that Mn-HDCL could have a role to play as a tumor-targeting photothermal sensitizer.
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