Visible-light Excited Luminescent Trigonal Prismatic Metallocages from Template-directed Assembly

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 (λmaxex = 460 nm) responsive red emissions (λmaxem = 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.