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

Abstract

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(NO3)3(H2O)(CH3OH)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.