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Multiphoton excited fluorescence of organic molecules is promising in the applications of efficient nonlinear optical devices and bioimaging. However, they usually have disadvantages of poor photostability and serious fluorescence quenching in aqueous media or solid state, which seriously limit their related applications. In this work, for the first time, the two‐photon excited Förster resonance energy transfer (FRET) process is used to enhance the solid‐state fluorescence of the supramolecular centre (acceptor) in an artificial 3D metal–organic complex (MLC), in which a 3D Zn (II)‐coordinated tetrahedral core is utilized as the donor. More interestingly, the two‐photon light harvesting system, which can be pumped with an optical intensity as low as 1 MW/cm2, exhibits an ultrafast energy transfer rate (∼6.9 × 108 s−1) and ultrahigh photostability. The underlying physical mechanisms are revealed through comprehensive steady‐state and time‐resolved spectroscopic analysis. This work demonstrates that the 3D MLC can be directly used in two‐photon bioimaging and also sheds light on developing other multiphoton harvesting systems, such as metal–organic frameworks. [ABSTRACT FROM AUTHOR]

Developing organic chromophores with large two-photon absorption (TPA) in both organic solvents and aqueous media is crucial owing to their applications in solid-state photonic devices and biological imaging. Herein, a series of novel terpyridine-based quadrupolar derivatives have been synthesized. The influences of electron-donating group, type of conjugated bridge, as well as solvent polarity on the molecular TPA properties have been investigated in detail. In contrast to the case in organic solvents, bis(thienyl)-benzothiadiazole as a rigid conjugated bridge will completely quench molecular two-photon emission in aqueous media. However, the combination of alkylcarbazole as the donor and bis(styryl)benzene as a conjugation bridge can enlarge molecular TPA cross-sections in both organic solvent and aqueous media. The reasonable two-photon emission brightness for the organic nanoparticles of chromophores 3- 5 in the aqueous media, prepared by the reprecipitation method, enables them to be used as probes for in vivo biological imaging. [ABSTRACT FROM AUTHOR]

Developing organic chromophores with large two-photon absorption (TPA) in both organic solvents and aqueous media is crucial owing to their applications in solid-state photonic devices and biological imaging. Herein, a series of novel terpyridine-based quadrupolar derivatives have been synthesized. The influences of electron-donating group, type of conjugated bridge, as well as solvent polarity on the molecular TPA properties have been investigated in detail. In contrast to the case in organic solvents, bis(thienyl)-benzothiadiazole as a rigid conjugated bridge will completely quench molecular two-photon emission in aqueous media. However, the combination of alkylcarbazole as the donor and bis(styryl)benzene as a conjugation bridge can enlarge molecular TPA cross-sections in both organic solvent and aqueous media. The reasonable two-photon emission brightness for the organic nanoparticles of chromophores 3-5 in the aqueous media, prepared by the reprecipitation method, enables them to be used as probes for in vivo biological imaging., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)