Highly Emissive and Stable Five‐Coordinated Manganese(II) Complex for X‐Ray Imaging

Abstract Nowadays, the development of X‐ray imaging has promoted the demand for new‐type scintillators, among which low‐toxic manganese(II) complexes have attracted burgeoning research interest. Herein, a highly stable manganese(II) complex with peculiar five‐coordinated modes is reported, which exhibits strong yellow emission peaked at 583 nm originating from d‐d transition of Mn 2+ with high photoluminescence quantum yield (PLQY) up to 93%. The five‐coordinated manganese(II) complex has been rarely reported so far which is an innovative spot in the field of photofunctional metal complex. Thanks to the high PLQY and relatively large stokes shift, the manganese(II) complex yields bright yellow emission under low‐dose X‐ray irradiation and delivers excellent linear response to X‐ray, highlighting its suitability for X‐ray contrast imaging. Based on this, highly resolved X‐ray imaging is successfully achieved that can meet the requirements of many application scenarios. In addition, this manganese(II) complex demonstrates excellent radiation hardness, humidity resistance, and heat stability, indicating the application potential of scintillators in harsh environments. This research not only provides guidance for the design and fabrication of highly luminescent manganese(II)‐based complexes, but also demonstrates the potential of manganese(II)‐based complexes as scintillators for X‐ray imaging technology.