Solution‐State Cooperative Luminescence Upconversion in Molecular Ytterbium Dimers

Abstract

Abstract Two homometallic ytterbium dimers are prepared and their solution‐state photoluminescence and upconversion properties are investigated. Both complexes exhibit two‐photon cooperative luminescence upconversion in the visible region (λ em ≈ 510 nm) upon excitation into the near‐infrared Yb 2 F 5/2 ← 2 F 7/2 absorption band at 980 nm. This miniaturization of the cooperative luminescence phenomenon down to just two Yb ions unequivocally proves the mechanistic origins of this process. Time‐resolved measurements and excited‐state modeling indicate the presence of a slow recombination of two singly excited ions Yb*Yb* into a virtual excited state, which ultimately gives rise to the observed emission at ≈510 nm.