Visible-Light Excited Luminescent Trigonal Prismatic Metallocages From A Template-Directed Assembly

Six trigonal prismatic metallocages (TPMs) composed of 24 components, namely {(Cu3L3)(Cu2X2)(3)(Cu3L3)}center dot 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-HMIDLINE HORIZONTAL ELLIPSIS pi dominate their host-guest interactions. They show rare visible-light (lambda max(ex) = 460 nm) responsive red emissions (lambda max(ems) = 675-680 nm). The low-lying pi* orbitals in a quinoline-8-thio (QT) chromophore triggers (MLCT)-M-3/(XLCT)-X-3 in Cu2X2(QT)(2), resulting into visible-light excited red emissions based on Cu2I2(QT)(2) but not Cu(3)Pz(3) coordination units, as revealed by DFT and TDDFT calculations.