Effi cient Energy Transfer under Two-Photon Excitation in a 3D, Supramolecular, Zn(II)-Coordinated, Self-Assembled Organic Network

Organic chromophores or crystals with large two-photon absorption (TPA) in the solid state are very much demanded for applications in optical limiting, frequency-upconversion lasing, laser pulse stabilization and reshaping etc. [ 1,2 ] In particular, effi cient two-photon excited fl uorescence emission or absorption that can be achieved at low optical intensity with the near infrared wavelengths is very important in practical nonlinear optical devices or biomedical imaging. [ 3,4 ] To obtain large TPA cross-sections, various molecular structures have been designed. Unfortunately, these strategies are usually only valid in organic solvents. [ 5 ] They suffer from poor photostability and serious fl uorescence quenching in aqueous media or solid state due to aggregation to different extents, [ 6 ] which is especially unfavourable for the applications in biological imaging and solid state devices. [ 7 ] Therefore, developing organic chromophores with strong two-photon excited fl uorescence and high photostability in the solid state remains challenging for various practical applications. [ 8 ]