| Abstrakt: |
The structural, photophysical, and photochemical properties of Ln(depma)(hmpa)2(NO3)3(Ln = La, Ce, Nd, Sm, Eu, Tb, Ho, Er, and Yb) complexes 1-Lnwere investigated with a multidisciplinary approach involving synthesis, photocycloaddition-based crystal engineering, spectroscopic analytical techniques and quantum chemical ab initio calculations. Depending on the Ln3+ion the isostructural 1-Lncomplexes exhibit quite different behavior upon excitation at 350–400 nm. Some 1-Lncomplexes (Ln = La, Ce, Sm, Tb, Yb) emit a broad and strong band near 533 nm arising from paired anthracene moieties, whereas others (Ln = Nd, Eu, Ho, Er) do not. 1-Euis not emissive at all, whereas 1-Nd, 1-Ho, and 1-Erexhibit a Ln3+based luminescence. Upon irradiation with 365 nm ultraviolet (UV) light 1-Ln(Ln = La, Ce, Sm, Tb, Yb) dimerize by means of a photochemically induced [4 + 4] cycloaddition of the anthracene moieties, whereas 1-Ln(Ln = Nd, Eu, Ho, Er) remain monomers. We propose three models, based on the matching of the energy levels between the Ln3+ion and the paired or dimerized anthracene units in the energy-resonance crossing region, as well as on internal conversion-driven and intersystem crossing-driven energy transfer, which explain the Ln3+ion regulated photophysics and photochemistry of the 1-Lncomplexes. |
