Switching of excited states in cyclometalated platinum complexes incorporating pyridyl-acetylide ligands (Pt-C[triple bond, length as m-dash]C-py): a combined experimental and theoretical study

International audienceThis article presents the design of cyclometalated platinum(II) complexes incorporating pyridyl-appended acetylide ligands of the form Pt-C[triple bond, length as m-dash]C-py, acting either as sites for protonation or methylation reactions or as a host receptor for binding metal cations. The complexes studied are Pt(t-Bu2phbpy)(-C[triple bond, length as m-dash]C-py), 2, which can undergo protonation at the pyridyl N; its cationic N-methylated derivative [Pt(t-Bu2phbpy)(-C[triple bond, length as m-dash]C-pyMe)]+, 4, which serves as a model of the N-protonated species; and a derivative in which the pyridyl ring is incorporated into a macrocyclic diamide-crown ether ligand (3). The co-ligand t-Bu2phbpy is a cyclometalated, N[caret]N[caret]C-coordinated phenylbipyridine ligand carrying tert-butyl groups at the 4-positions of the pyridyl rings. The photophysical properties of the neutral compounds 2 and 3 have been compared to those of the pyridinium, methyl-pyridinium or metal-complexed species (namely 2-H+, 4 and 3-Pb2+). Detailed TD-DFT calculations provide a theoretical basis to account for the experimentally-observed changes upon protonation/methylation/complexation. The joint TD-DFT and experimental studies provide evidence for an unprecedented molecular switch in the nature of the excited state (from mixed L′LCT/MLCT to ML′CT) in which the acceptor ligand in the CT process switches from being the N[caret]N[caret]C ligand to the pyridyl acetylide

Cyclometallated platinum(II) complexes containing pyridyl-acetylide ligands: the selective influence of lead binding on luminescence

International audienceThe design, synthesis, photophysical properties, and the ion-binding properties of cyclometallated platinum(II) complexes containing pyridyl-appended alkynyl ligands are described. When the pyridyl group is incorporated into an azamacrocycle, a specific response towards lead(II) cations involves a change in the nature of the excited charge transfer state, resulting in the appearance of a low-energy absorption band and a partial quenching of luminescence

A new Holocene relative sea-level curve for western Brittany (France): Insights on isostatic dynamics along the Atlantic coasts of north-western Europe

International audienceThis study presents new Relative Sea Level (RSL) data that were obtained in the Finistère region (Western tip of Brittany, France) and the implications those data have for the understanding of the isostatic dynamics across north-western Europe, and more specifically along the Atlantic and Channel coasts. New stratigraphic sequences were obtained and analyzed to derive 24 new Sea-level Index Points, in which 6 are basal. These new data considerably increase the knowledge we have of the RSL evolution along the coasts of Western Brittany since the last 8 kyr B.P. From this new dataset, RSL was estimated to rise continuously over the last 8 kyr with a major inflection at ca. 6 kyr cal. BP. Our results show large vertical discrepancies between the RSL records of Brittany and South-Western UK, with the latter plotting several meters below the new data. From this comparison we suggest that the two regions underwent a very different pattern and/or amplitude of subsidence during the last 8 kyr which has implications for the spatial and temporal pattern of the peripheral bulge of the European ice sheets. We compared our data against predictions from Glacio-Isostatic Adjustment models (GIA models). There are large misfits between RSL observations and the predictions of the global (ICE-5G (VM2a) – Peltier, 2004, GLAC1-b – Tarasov and Peltier, 2002; Tarasov et al., 2012, Briggs et al., 2014) and regional UK models (“BIIS” – Bradley et al., 2009; Bradley et al., 2011; “Kuchar”- Kuchar et al., 2012), which can't be resolved through significant changes to the deglaciation history and size of the British–Irish Ice sheet. Paleo-tidal modelling corrections indicate regional changes in the tidal ranges played a negligible role in the data-model misfits. Hence, we propose that the misfits are due to some combination of: (i) unaccounted mass-loss of far-field ice-sheets (Antarctic ice-Sheet or Laurentide Ice-Sheet), (ii) unresolved differences in the deglaciation history and size of the Fennoscandian Ice sheet or, more likely, (iii) significant lateral variations in the Earth's structure across the English Channel

Flavonol based ruthenium acetylides as fluorescent chemosensors for lead ions

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Cyclometallated platinium(II) complexes incorporating ethynyl-flavone ligands : switching between triplet and singlet emission induced by selective binding of Pb2+ ions

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