Application of d- and f-Block Fluorescent Cell Imaging Agents - The Chemistry of Molecular Imaging - page 294

O

O

NH N HN

HN

O

O

O

O

FigUre 12.28 Top left: Free ligand. Bottom: Multi-photon confocal microscopy images of the terbium complexes. Hoechst
33342-labelled nuclei (blue) in the HONE1 cells with excitation at 800 nm, Filter BP = 400-480 nm (left); (middle) terbium complexes
loaded into the cell for 1 hour (Figure 2c) with nuclei labelled, filter BP = 400-615 nm; (right) bright field image of the HONE1 cells. ( See insert
for colour representation of the figure.) )

O

O

N

3-

O

O

O

O

O

N

O

O

O

N

Eu

O

O

NH

O

O

O

O

O O

O

N

O

O

O

O

O

O

O

O

OMe

OMe

MeO

FigUre 12.29 The tris picolinate Ln(III) complex core (left) and free ligand (inset).

The utility of two-photon sensitisation of water-soluble Eu III complexes of the form [Eu(L) 3 ] 3- has also been demonstrated
by Maury, with ligands derived from 2,6-pyridine dicarboxylic acid (Figure 12.29). Additional functionality was achieved
via an alkylphenylacetylene bridge, which serves dually to extend the π-conjugation and provide improved hydrophilicity
through terminating tris(triethyleneglycol)phenyl groups. The absorption properties of the Eu III complex are dominated by
ligand-centred transitions, with the longest wavelength contribution (332 nm) assigned to a CT (alkoxy-to-pyridine) type
electronic absorption. The complex was strongly emissive (Φ ~16%) with a long lifetime in water (1.06 ms) characteristic of