As a result of the different degrees of stabilization experienced by the 4f, 5d, and 6s orbitals occurring upon ionization of the neutral metal, the lanthanides (La-Lu, Z ) 57-71) exist almost exclusively in their trivalent state Ln(III) ([Xe]4fn, n ) 0-14) in coordination complexes or supramolecular assemblies.1 Except for some arene compounds involving bulky substituted benzenes or cyclo-octatetraenes,2 covalence plays a minor role in Ln-ligand dative bonds and the nature of the coordination sphere is controlled by a subtle interplay between electrostatic interactions and interligand steric constraints.3 Variable coordination numbers (6 e CN e 12) and geometries are thus observed in lanthanide complexes, leading to limited success in the design of molecular architectures with predetermined structures.3,4 Although rigid or semirigid receptors may help to control the coordination sphere according to the lock-and-key and induced fit concepts,5 detailed studies of lanthanide solvates with water or acetonitrile suggest that trivalent lanthanides display a tendency to adopt nine-coordinate tricapped trigonal prismatic (TTP) arrangements around the metal ion in the solid state. In solution, the picture is a little more subtle:6 in water, for instance, large Ln(III) ions at the beginning of the series (Ln ) La-Nd) adopt TTP geometries, which are gradually transformed into eight-coordinate square antiprismatic (SAP) arrangements for small Ln(III) ions (Ln ) Tb-Lu), equilibria between CN ) 8 and CN ) 9 being observed for Ln ) Nd-Tb.7 The systematic contraction of the ionic radii observed when going from Ln ) La to Lu (often referred to as the lanthanide contraction)8 explains this trend and increases electrostatic bonding for heavier lanthanides, but this variation is so smooth and limited (15% contraction between La and Lu and ≈1% between two successive lanthanides) that selective recognition and incorporation into organized supramolecular architectures remains challenging.5 A rational access to extended polymetallic lanthanide-containing assemblies with predictable and controlled geometries is consequently very limited, and pioneer work in this field has focused on poorly characterized intricate mixtures of complexes in solution which are ‘transformed’ into well-defined solid-state clusters or networks through crystallization processes involving a rich palette of † Institute of Molecular and Biological Chemistry, Lausanne. E-mail: Jean-Claude.Bunzli@epfl.ch. ‡ Department of Inorganic, Analytical and Applied Chemistry, Geneva. E-mail: Claude.Piguet@chiam.unige.ch.

/pdf/lanthanide-containing-molecular-and-supramolecular-ul4kv6ev9m.pdf

Lanthanide-containing molecular and supramolecular polymetallic functional assemblies.

Digital information processing in molecular systems.

Bioinorganic photochemistry: frontiers and mechanisms.

Green and yellow-emitting 1,6- and 1,8-bis(phenylethynyl) pyrenes (dyes 7, 8, 9, and 10) with different intramolecular charge transfer (ICT) feature were synthesized and the effect of ICT on the photophysical properties of these derivatives were studied by UV−vis absorption spectra, fluorescence emission spectra, and DFT/TDDFT calculations. For the dyes with electron-pushing group (e.g., -dimethylamino, dye 8 and dye 10), structureless and solvent polarity-sensitive fluorescence emission spectra were observed. Conversely, dye with electron-withdrawing group (e.g., −CN, dye 7) shows structured and solvent polarity-independent emission spectra. OFF−ON fluorescent thiol probes 11 and 12 with 2,4-dinitrobenzenesulfonyl protected ethynylpyrene fluorophore were designed based on DFT/TDDFT calculations, which predicts dark state (S1) for these thiol probes (e.g., oscillator strength f = 0.0086 for S1←S0 transition of the probe 11). This dark state is induced by the ICT effect with ethynylated pyrene fluorophore ...

Tuning the intramolecular charge transfer of alkynylpyrenes: effect on photophysical properties and its application in design of OFF-ON fluorescent thiol probes.

Dual responsive chemosensors for anions: the combination of fluorescent PET (Photoinduced Electron Transfer) and colorimetric chemosensors in a single molecule

Juliette Roiron

Papers

Metal complexes as components of luminescent signalling systems