4f → 3d sensitization: a luminescent Eu II -Mn II heteronuclear complex with a near-unity quantum yield.

A new heteronuclear Eu II -Mn II complex [Eu(N2O6)]MnBr4 (N2O6 = 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane) is designed and synthesized, which shows an intense green emission from Mn II with a near-unity photoluminescence quantum yield. Measurement of excited-state dynamics demonstrated the sensitization process from Eu II to Mn II , which represents the first example of f → d molecular sensitization. Due to the large optical absorption cross-section of the Eu II center, [Eu(N2O6)]MnBr4 shows an emission intensity 7 to 2500 times stronger than that of the Sr II -Mn II control complex [Sr(N2O6)]MnBr4 upon the excitation of near ultraviolet to blue light.