Visible-light excited luminescent trigonal prismatic metallocages from a template-directed assembly

Abstract

Six trigonal prismatic metallocages (TPMs) composed of 24 components, namely {(Cu₃L₃)(Cu₂X₂)₃(Cu₃L₃)}·xG (HL = 4-(quinoline-8-thio)-3,5-dimethyl-1H-pyrazole, G = benzene (B), methylbenzene (MB), 1,3,5-triphenylbenzene (TPB), x = 3 for B, MB and 1 for TPB), are reported. They were constructed by three rhombic Cu₂X₂ units as columns connecting two planar syn-Cu₃L₃ faces, templated by G molecules. The structural analysis and EDA calculations reveal that C–H⋯π dominate their host–guest interactions. They show rare visible-light (λ^max_ex = 460 nm) responsive red emissions (λ^max_em = 675–680 nm). The low-lying π* orbitals in a quinoline-8-thio (QT) chromophore triggers ³MLCT/³XLCT in Cu₂X₂(QT)₂, resulting into visible-light excited red emissions based on Cu₂I₂(QT)₂ but not Cu₃Pz₃ coordination units, as revealed by DFT and TDDFT calculations.