Cyclometalated platinum(II) with ethynyl-linked azobenzene ligands: an original switching mode.

International audienceThe photophysical properties of 6-phenyl-2,2'-bipyridyl platinum(ii) complexes bearing different σ-alkynyl-linked azobenzene ancillary ligands were investigated. These complexes exhibited strong, broad, structureless charge-transfer bands in the visible region, which were red-shifted when the electron-donating ability of the para substituent on the azo-acetylide ligand increased. When excited at the charge-transfer absorption band, the complexes exhibited weak green emission, which was assigned to a triplet metal-to-ligand charge transfer/interligand charge transfer emission ((3)MLCT/(3)L'LCT). The presence of an amino substituent in the azobenzene moiety opened the possibility of protonation, which led to the formation of an azonium based derivative and resulted in drastic perturbations of the molecular orbitals and photophysical properties of the Pt-acetylide complex. These studies are fully supported by DFT and TD-DFT calculations

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

Absorption and Fluorescence Signatures of 1,2,3-Triazole Based Regioisomers : Challenging Compounds for TD-DFT

International audienceIn the continuous quest for improving TD-DFT methodologies as a tool to predict the photophysical features of solvated chro- mophores, we herein investigate two model regioisomers based on the 1,2,3-triazole moiety. Starting from their experimental absorption and emission spectra, key energy differences highlighting the main trends between the two isomers are extracted and used to gauge the accuracy of several levels of theory. RI-CC2 and EOM-CCSD calculations allow us to ascertain that the low energy spectra is not linked to double excitations. In vacuum, neither these methods nor any of the implemented TD-DFT levels of theory, ranging from global hybrids (PBE0, B3LYP) to range-separated functionals without (CAM-B3LYP, ωB97X) or with dispersion corrections (ωB97X-D), is able to capture the key features that differentiate the two chromophores. Accounting for solvent within a specific PCM model allows to recover experimental trends, but the dramatic changes occurring when moving from toluene to THF and/or for different PCM approaches (LR, cLR, SS) suggest that this agreement is probably fortuitous. Even so the ωB97X-D functional combined to the SS-PCM scheme leads to quantitative agreement with experiment, TD-DFT results obtained for 1,2,3-triazole based chromophores need to be treated with caution. We also show that the SS-PCM approach may be useful to test current and novel exchange-correlation functionals against the charge transfer failure

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

Photoisomerisation in Aminoazobenzene-Substituted Ruthenium(II) Tris(bipyridine) Complexes: Influence of the Conjugation Pathway.

International audienceTransition-metal complexes containing stimuli-responsive systems are attractive for applications in optical devices, photonic memory, photosensing, as well as luminescence imaging. Amongst them, photochromic metal complexes offer the possibility of combining the specific properties of the metal centre and the optical response of the photochromic group. The synthesis, the electrochemical properties and the photophysical characterisation of a series of donor-acceptor azobenzene derivatives that possess bipyridine groups connected to a 4-dialkylaminoazobenzene moiety through various linkers are presented. DFT and TD-DFT calculations were performed to complement the experimental findings and contribute to their interpretation. The position and nature of the linker (ethynyl, triazolyl, none) were engineered and shown to induce different electronic coupling between donor and acceptor in ligands and complexes. This in turn led to strong modulations in terms of photoisomerisation of the ligands and complexes

Synthesis, photophysics and nonlinear optical properties of stilbenoid pyrimidine-based dyes bearing methylenepyran donor groups.

International audienceThe nonlinear properties and the photophysical behavior of two π-conjugated chromophores that incorporate an electron-deficient pyrimidine core (A) and γ-methylenepyrans as terminal donor (D) groups have been thoroughly investigated. Both dipolar and quadrupolar branching strategies are explored and rationalized on the basis of the Frenkel exciton model. Even though a cooperative effect is clearly observed if the dimensionality is increased, the nonlinear optical (NLO) response of this series is moderate if one considers the nature of the D/A couple and the size of the chromophores (as measured by the number of π electrons). This effect was attributed to a disruption in the electronic conjugation within the dyes' scaffold for which the geometry deviates from planarity owing to a noticeable twisting of the pyranylidene end-groups. This latter structural parameter also has a strong influence on the excited-state dynamics, which leads to a very efficient fluorescence quenching

Nonlinear optical properties of intriguing Ru σ-acetylide complexes and the use of a photocrosslinked polymer as a springboard to obtain SHG active thin films

This work reports on the design, synthesis and photo-physical properties of two ruthenium σ-alkynyl complexes. It is shown that, despite similar optical absorption features recorded in solution, the introduction of a benzaldehyde moiety leads to an improved non-linear optical (NLO) response as measured by Electric Field Induced Second Harmonic (EFISH) generation and Third Harmonic Generation (THG) at 1.907 μm, both related to the second order hyperpolarizability. These structure–property relationships are rationalized based on few state modelling. Complex 2 is subsequently processed to afford composite films that demonstrate a χ2 of 1.4 pm V−1, quite remarkable given the ease of film processing implemented in this work

Selectivite de processus organometalliques induite par des ligands phosphores : synthese de nouveaux complexes soufres du fer

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Design of ruthenium-alkynyl complexes as nonlinear optical chromophores

International audienceThis review paper focuses on the design and non linear optical properties of trans-Ru(dppe)2 (dppe = 1,2-bis(diphenylphosphino)ethane) alkynyl complexes and their derivatives. These systems constitute remarkable second and third-order non linear optical active chromophores. Furthermore, modifying the environment around the ruthenium affords the possibility of tuning their non linear optical performances and accessing facile non linear optical switching. The coverage is focused on quadratic (second-order) and cubic (third-order) non linear optical properties measured at molecular level from solution studies as well as on non linear optical properties of bulk material

Sensory luminescent iridium(III) and platinum(II) complexes for cation recognition

International audienceThis article presents the design and photophysical properties of platinum and iridium complexes incorporating a host receptor for metal cations, with particular attention to the changes in their luminescence properties upon addition of these ions in solution. Selected examples on cationic and neutral complexes within the families of Pt and Ir complexes will be presented. A series of platinum acetylide complexes incorporating a crown ether unit have been designed and prepared for the detection of alkali and alkaline-earth cations. Similarly, Ir complexes, cationic and neutral species, have been used as luminophores using the same receptor units. Metal-based chemosensors for transition- and heavy-metal ions have been also developed. The detection of divalent metal cations such as Zn2+, Cd2+ and Cu2+, has been achieved thanks to the interesting chelating properties of di(2-picolyl)amine (2,2′-DPA) ionophore. Introducing appropriate substituents (flavone, macrocyclic pyridine) on the ancillary acetylide ligand of cyclometalated platinum(II) allows the recognition of Pb2+ ions. Mercury(II), a thiophilic metal ion, interacts with the sulfur atom of cyclometalated ligands of iridium complexes inducing remarkable emission spectral changes. These luminescent metal-based sensors give rise to phosphorescence turn-on or turn-off effects as well as changes in the emission wavelength and/or emission lifetime