Hydrogen bonds promoted formation of Eu(III)-based host-guest complex and luminescence properties.

[Display omitted] Eu(III) host-guest complex: A host-guest complex 1 was controllably self-assembled using hydrogen bonding directed encapsulation strategy. In this host-guest inclusion systems, a reversible structure transformation between two complexes can be controlled exactly via sequentially changing different guest molecules (hydroxides and solvated lanthanide ions). In this interconversion process, the host molecular conformation motion, EuIII–centered emission enhancement and fluorescence imaging behavior were also observed. • Eu(III)-based host-guest complex is self-assembled via multiple hydrogen bonds. • The host conformation motion and emission enhancement behavior are also observed. • Emissive complex could be used as an imaging regent in living cell potentially. Host-guest interaction is widely employed as a powerful tool to create supramolecular assembles with multicomponent units. In this work, an emissive quinoline-based tripodal acceptor L1 with tunable syn and anti -conformers was synthesized and used as host. Upon binding with guest species, Eu(III)-based host–guest complex 1 (L1 ⊃ [Eu(NO 3) 3 (H 2 O)(CH 3 OH) 2 ]) was constructed via host–guest interaction driven by multiple hydrogen bonds. Furthermore, in this complex, host conformation motion and Eu(III)–centered emission enhancement behavior are also observed by X-ray single crystal diffraction and fluorescence spectrometer. Theoretically, Density Functional Theory (DFT) calculations revealed that the anti and syn -conformations are stabilized by complexation of solvated lanthanide ions within cavity of tripodal host L1 , respectively. The calculations were in good agreement with the experimental data. Moreover, emissive host–guest complex 1 could be used as an imaging regent in living cell potentially. [ABSTRACT FROM AUTHOR]