Stepwise Increase of NdIII‐Based Phosphorescence by AIE‐Active Sensitizer: Broadening the AIPE Family from Transition Metals to Discrete Near‐Infrared Lanthanide Complexes

We designed two near‐infrared (NIR) lanthanide complexes [(L)2‐Nd(NO3)3] (L=TPE2‐BPY for 1, TPE‐BPY for 2) by employing aggregation‐induced emission (AIE)‐active tetraphenylethylene (TPE) derivatives as sensitizers, which possessed matched energy to NdIII, prevented competitive deactivation under aggregation, even shifted the excitation window toward 600 nm by twisted intramolecular charge transfer. Furthermore, benefiting from the 4 f electron shielding effect and antenna effect, the enhanced excitation energies of the AIE‐active sensitizers by structural rigidification transferred into the inert NdIII excited state through 3LMCT, affording the first aggregation‐induced phosphorescence enhancement (AIPE)‐active discrete NIR‐emitting lanthanide complexes. As 1 equipped with more AIE‐active TPE than 2, L→Nd energy transfer efficiency in the former was higher than that in the latter under the same conditions. Consequently, the crystal of 1 exhibited one of the longest lifetimes (9.69 μs) among NdIII‐based complexes containing C−H bonds. With help of antenna effect, the excitation energies of the AIE‐active sensitizers are enhanced while transferring into the inert NdIII excited state through 3LMCT. Further beneficial from the structural rigidification, AIE‐active L as sensitizers possessed matched energy to NdIII, less non‐radiative process, and low excitation window by twisted intramolecular charge transfer (TICT), thus affording the first AIPE‐active discrete NIR‐emitting lanthanide complexes with the longest lifetimes among NdIII‐based complexes containing C−H bonds.