Véronique Guerchais

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

Platinum-ethynylflavone complexes featuring various polyether arms display 3IL phosphorescence associated with the appended flavone perturbed by the platinum centre (tau approximately 20 micros), but switch dramatically to flavone-localised 1IL fluorescence (tau approximately 2 ns) upon selective binding of Pb2+.

Modulating the luminescence of an iridium(III) complex incorporating a di(2-picolyl)anilino-appended bipyridine ligand with Zn2+ cations

A novel iridium complex incorporating a di(2-picolyl)anilino-appended bipyridine ligand was synthesized and its optical properties studied. The presence of Zn2+ ions specifically perturbs the excited state, giving rise to a blue-shifted absorption and emission, and a shorter luminescence lifetime.

Photoswitching of the second-order nonlinearity of a tetrahedral octupolar multi DTE-based copper(I) complex

The modulation of the quadratic NLO response of an octupolar metal-based chromophore featuring four photochromic dithienylethene units is reported. Quantum mechanical simulations are consistent with a full switching of the DTE units and reproduce the strong enhancement of the NLO response.

Metal Complexes for Two-Photon Photodynamic Therapy: A Cyclometallated Iridium Complex Induces Two-Photon Photosensitization of Cancer Cells under Near-IR Light

Abstract Photodynamic therapy (PDT) uses photosensitizers (PS) which only become cytotoxic upon light‐irradiation. Transition‐metal complexes are highly promising PS due to long excited‐state lifetimes, and high photo‐stabilities. However, these complexes usually absorb higher‐energy UV/Vis light, whereas the optimal tissue transparency is in the lower‐energy NIR region. Two‐photon excitation (TPE) can overcome this dichotomy, with simultaneous absorption of two lower‐energy NIR‐photons populating the same PS‐active excited state as one higher‐energy photon. We introduce two low‐molecular weight, long‐lived and photo‐stable iridium complexes of the [Ir(N^C)2(N^N)]+ family with high TP‐absorption, which localise to mitochondria and lysosomal structures in live cells. The compounds are efficient PS under 1‐photon irradiation (405 nm) resulting in apoptotic cell death in diverse cancer cell lines at low light doses (3.6 J cm−2), low concentrations, and photo‐indexes greater than 555. Remarkably 1 also displays high PS activity killing cancer cells under NIR two‐photon excitation (760 nm), which along with its photo‐stability indicates potential future clinical application.

Linear and nonlinear optical properties of tris-cyclometalated phenylpyridine Ir(III) complexes incorporating π-conjugated substituents.

The synthesis, luminescence, and nonlinear optical properties of a new series of Ir(ppy)3 (ppy = 2-phenylpyridine) complexes incorporating π-extended vinyl-aryl substituents at the para positions of their pyridine rings are reported. Appropriate substitution of the pyridyl rings allows the tuning of the luminescence properties and the second-order nonlinear optical response of this unusual family of three-dimensional chromophores. Theoretical calculations were performed to evaluate the dipole moments, to gain insight into the electronic structure, and to rationalize the observed optical properties of the investigated complexes.

The first hexadithienylethene-substituted tris(bipyridine)metal complexes as quadratic NLO photoswitches: combined experimental and DFT studies.

Flip the NLO switch! A straightforward access to hexadithienylethene-based photochromes by using a coordination-chemistry approach through the combination of bis(dithienylethene)bipyridyl ligands and metal ions (M = Zn, Fe) is reported. The photostability of the isomeric forms of the iron(II) complexes allows the photoswitching of second-order nonlinear optical (NLO) responses (see figure), and the results are rationalized with the help of time-dependent density functional theory.

A straightforward access to photochromic diarylethene derivatives via palladium-catalysed direct heteroarylation of 1,2-dichloroperfluorocyclopentene

A novel and efficient palladium-catalysed direct di-heteroarylation of 1,2-dichloroperfluorocyclopentene with a variety of heteroarenes is reported, giving rise to 1,2-di(heteroaryl)ylperfluorocyclopentene photochromic compounds. The reaction proceeds with thiazoles, thiophenes or furan derivatives and tolerates various substituents.

Rapid and convenient sonochemically-assisted alkyl-metal synthesis

Abstract Sonochemically-activated potassium metal is a powerful and stoicheiometric reducing reagent and quickly produces the metallates [M(C 5 Me 5 )(CO) n ] − K + from the dimers [M(C 5 Me 5 )(CO) n ] 2 (M = Fe, Ru, n = 2; M = Mo, n = 3). The reductions were carried out on a scale of 1 to 20 mmol with a 100 or 600 W acoustic power generator and a titanium horn directly immersed in the solution, and were complete in 15–20 min. In situ alkylation with one equivalent of a electrophile RX (CH 3 I, CH 3 CH 2 I, CH 3 OCH 2 Cl, CH 3 OCH 2 Br) reagent provides a facile synthesis of metal alkyl M(C 5 Me 5 )(CO) n R.

σ versus π bonding in polymethylthiophene complexes of iron

Abstract The mode of bonding of polymethylthiophenes has been found to depend on the source of (CpFe II ) + used in the ligand exchange reaction. The reaction of ferrocene containing AlCl 3 and H 2 O at 90°C with polymethylthiophenes gives the pure π complexes [CpFe II (η 5 -polymethylthiophene)] + , whereas treatment of CpFe(CO) 2 Cl with 2,5-dimethylthiophene yields the S -bonded complex [CpFe II (CO) 2 (η 1 -SC 4 Me 2 H 2 )] + ( 4 + ). One-electron reduction of [CpFe II (η 5 -SC 4 Me 4 )] + ( 1 + ) by LiAlH 4 gives the new air-sensitive complex CpFe I (η 5 -SC 4 Me 4 ) ( 1 ) which has been characterized by EPR, Mossbauer, and optical spectroscopies.

Palladium-Catalyzed Direct Arylation of Luminescent Bis-Cyclometalated Iridium(III) Complexes Incorporating C^N- or O^O-Coordinating Thiophene-Based Ligands: an Efficient Method for Color Tuning.

We report the palladium-catalyzed direct 5-arylation of both metalated and nonmetalated thiophene moieties of iridium complexes 2, 3, and 4 with aryl halides via C-H bond functionalization. This method opens new routes to varieties of Ir complexes in only one step, allowing easy modification of the nature of the ligand. The photophysical properties of the new functionalized complexes have been studied by means of absorption and emission spectroscopy. The extension of the π-conjugated system induces a bathochromic and hyperchromic shift of the absorption spectra, an effect reproduced by first principle calculations. Indeed, the bathochromic shifts are related to a more delocalized nature of the excited-states. All complexes are photoluminescent in the red region of the spectrum. This study establishes that arylation of the thienyl ring affects strongly the electronic properties of the resulting complexes, even when the thienyl ring is remote and not directly metalated to the iridium center, as in the thienyltrifluoroacetonate complex 4.