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

Rapid Prototyping of Polymeric Nanopillars by 3D Direct Laser Writing for Controlling Cell Behavior

Mammalian cells have been widely shown to respond to nano-and microtopography that mimics the extracellular matrix. Synthetic nano-and micron-sized structures are therefore of great interest in the field of tissue engineering, where polymers are particularly attractive due to excellent biocompatibility and versatile fabrication methods. Ordered arrays of polymeric pillars provide a controlled topographical environment to study and manipulate cells, but processing methods are typically either optimized for the nano-or microscale. Here, we demonstrate polymeric nanopillar (NP) fabrication using 3D direct laser writing (3D DLW), which offers a rapid prototyping across both size regimes. The NPs are interfaced with NIH3T3 cells and the effect of tuning geometrical parameters of the NP array is investigated. Cells are found to adhere on a wide range of geometries, but the interface depends on NP density and length. The Cell Interface with Nanostructure Arrays (CINA) model is successfully extended to predict the type of interface formed on different NP geometries, which is found to correlate with the efficiency of cell alignment along the NPs. The combination of the CINA model with the highly versatile 3D DLW fabrication thus holds the promise of improved design of polymeric NP arrays for controlling cell growth

Theoretical evidence of metal-induced structural distortions in a series of bipyrimidine-based ligands.

International audienceHerein, we report theoretical evidence of the geometric changes occurring upon complexation, for a series of octupolar bipyrimidine-based ligands incorporating the NPh2 terminal donor group. It is shown that ligands 1 and 2 (4,4',6,6'-tetrakis(N,N-diphenylaminostyryl)-[2,2']bipyrimidine and 4,4',6,6'-tetrakis((N,N-diphenyl)-9,9'-dioctyl-9H-fluorene-2-amine)-2,2'-bipyrimidine) exhibit a non-planar geometry with a torsion angle between both pyrimidine moieties of ∼25° and 50° respectively. 1a (complex of 1) becomes planar upon addition of ZnCl2 to the bipyrimidine moiety whereas 2a remains distorted. Furthermore, an assignment of the absorption bands for all compounds is presented

Polypyridyl Ruthenium Complexes: Versatile Tools for Linear and Non-Linear Optics

International audienceCoordination complexes have been attracting considerable interest due to their potential nonlinear optical (NLO) properties and applications in optoelectronic and photonic devices. Incorporation of metal atoms into π-conjugated systems allows many variables to be adjusted, such as the nature of ligands and metal ions as well as the symmetry of the complexes. In this paper, new ruthenium(II) complexes of formula [Ru(bpy)2(L)][PF6] and [Ru (L)3][PF6]2 are reported. We studied the influence of the nature of ligands, structural features and symmetry of these complexes on their two-photon absorption properties to provide useful physical and chemical insights for similar ruthenium complexes

Natural biopolymer surface of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)-photoinduced modification with triarylsulfonium salts

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