Laboratoire de Chimie de Coordination UPR 8241


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Thématiques

The design and characterization of new molecular photoactive materials are at the heart of our group. The materials currently under consideration have mainly interesting properties for nonlinear optical switching, optical storage (photochromic), and photodynamic therapy.


  • Ruthenium Nitrosyl Systems

The ruthenium nitrosyl complexes offer a large variety of physical-chemical properties. In particular, they are of great interest in optical data storage as well as for therapeutic applications.

• NO Photorelease

[RuIIL5NO]n+/- + solvent -> [RuIIIL5-(solvent)]n+/- + NO


The last three decades have witnessed an increasing interest for nitric oxide (NO·), which has been recognized to play a key role in numerous physiological and pathological. Nevertheless, the toxicological effects of NO· do not have to be unrecognized, and furthermore its therapeutic effects strongly depend on its concentration. Therefore, the search for suitable candidates capable of delivering NO· locally and quantitatively has become pressing in order to lead to optimized therapeutic applications.
Along this line ruthenium(II) nitrosyl complexes have gradually emerged as promising NO· donors, usually stable in the dark, and capable of releasing NO· under light irradiation in the wavelength range λ = 300 – 500 nm, exclusively. However, to be fully applicable, the photochemically induced NO· release should be achieved in the 600 to 1200 nm therapeutic window, of relative transparency of the biological media. Our strategy is based on the use of appropriate two photon absorption (TPA) systems.


An example of promising system obtained in the group is shown below. It is a complex in which the fluorenyl-terpyridine (FT) ligand is selected as a potential candidate for bringing the ruthenium complex with additional TPA capabilities.



• Photoinduced Linkage Isomerisation

[RuIIL5NO]n+/-->[RuIIL5ON]n+/-


These complexes are characterized by the existence of long-lived metastable states (t>107s) for specific irradiation at a temperature close to ambient temperature. The different states have different Ru-NO conformations which are responsible for a high change in the refractive index, a very important parameter for holographic data storage. [RuCl(py)4(NO)](PF6)2.1/2H2O (py=pyridine) complex studied previously in the group is high of interest because of its complete molecular photoswitching at the solid state.



Our results show that such photochromic composites could be obtained when the complexes are embedded in polymer or silica matrices.

Xerogel of [RuCl(py)4(NO)](PF6)2.1/2H2O
WO 2010/081977 A1 Patent, 22 juillet 2010



  • NLO Materials

Multi-functional materials and molecular switches have long been a traditional interest of our research. Along this line, the possibility to switch the NLO response of a molecule in an hybrid material by mean of any additional function (e.g. magnetic, conducting or photochromic properties) is investigated. Our expertise is based on computational chemistry, which has become an important tool for providing the efficient guidelines required by synthetic chemistry and physics, to target the microscopic origin of the NLO effects. Among various possibilities, switches can be obtained by :

- Optical effect through the total NLO extinction obtained after Ru-NO -> Ru-ON isomerization in specific molecules selected by computational methods.

- Magnetic effect through a spin crossover phenomenon, in Iron(II) metal complexes, like in the [Fe(Tren)]2+ system shown below, where the magnetic (χM) vs. NLO response (IHRS) correlation is clearly established.

The [Fe(Tren)]2+ cation subjected to a spin crossover phenomenon between 200 and 300 K



These investigations are based on a fruitful network of collaborations (Bordeaux, Valence, Kiev, Mexico).