Alkoxy Chain Engineering Enables Dual‐Mode Temperature‐Activated Phosphorescence in Neutral Manganese(II) Complexes

ABSTRACT Temperature‐responsive luminescent materials hold great potential for applications in various advanced photoelectronic fields. However, realizing dual‐mode, temperature‐activated luminescence within a single molecular system remains a significant challenge. Here, two neutral Mn(II) complexes with dual‐mode temperature‐activated luminescent properties have been successfully synthesized by an alkoxy chain engineering strategy. At room temperature, these complexes are strongly emission‐quenched. Reducing or increasing temperature triggers pronounced luminescence enhancement, due to the prohibition of thermal population to the upper lying quenching state or the removal of trace water molecules. Notably, this study provides the first definitive evidence of the dual‐mode temperature‐activated photoluminescent behavior in quartet excited states. Furthermore, simple digit‐display patterns and anti‐counterfeiting applications are demonstrated in this work.