Photophysical Properties and Applications of Lanthanoid Helicates - Metallofoldamers: Supramolecular Architectures from Helicates to Biomimetics - page 196

Scheme 6.2 Ditopic bis(tridentate) ligands for homometallic dinuclear lanthanoid helicates.

which provides a hexacoordinate environment to the Ln III ions in [Ln 2 (L16) 3 ] so that the
coordination sphere is completed either with bound water molecules or with an additional
ligand strand leading to an anionic quadruple-stranded [Eu(L16) 4 ] helicate [43]. The coor-
dination environments provided by the ditopic ligands are either N 9 (L3) or N 3 O 6 (all the
other ligands, except H 2 L16), which allows a systematic discussion of essential photophys-
ical parameters. Sections 6.2.1-6.2.5 focus on triple-stranded dinuclear helicates for which
extensive photophysical data are at hand. Other helicates are dealt with in Section 6.2.6.

6.2.1 Influence of the Triplet-State Energy on Quantum Yields
Typical photophysical parameters for the [Eu 2 (L) 3 ] n þ helicates are reported in Table 6.1.
They include the energy of 0-phonon component of the triplet state of the bonded ligands,
E 0-0 ( T ), which often plays a decisive role in the energy transfer process, the lifetime of