Jean-Luc Fillaut

Nonlinear optics and surface relief gratings in alkynyl–ruthenium complexes

Generally, the organometallic complexes rich in carbon and containing π-conjugated chains are materials interesting for the study of electronic transfer processes. Currently, the ruthenium–acetylide organometallic complexes form part of the most studied organometallic compounds in nonlinear optics. In this work, we highlight the nonlinear optical properties and the photo-induced structure of new organometallic complexes containing a ruthenium–acetylide donor fragment able to compete with the strongest organic donors. We determine, using various experimental techniques (degenerate four-wave mixing, second and third harmonic generation), the influence of the functionalization of these molecular structures on the improvement of their second-and third-order nonlinear optical properties exploiting in particular the nature of the acceptor fragment and the π-conjugated transmitter. Also we present the dynamics of formation of photo-induced surface relief gratings using a transmission holographic technique and the atomic force microscopy on ruthenium–acetylide complexes containing an azobenzene fragment.

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+.

Design and photoinduced surface relief grating formation of photoresponsive azobenzene based molecular materials with ruthenium acetylides

Novel photoresponsive materials based on ruthenium(II) σ-acetylides coupled to an azobenzene moiety in the main π-conjugated chain have been synthesized. The introduction of a metal acetylide fragment in the same conjugated chain as the azobenzene induces the trans-cis-trans isomerization of the azo unit, while the rate of the thermal cis → trans back isomerization increases with increasing overall electron richness of these compounds. These azobenzene-containing ruthenium(II) acetylides show satisfactory processability and give rise to spin-coated uniform thin films. Formation of surface-relief gratings on their amorphous thin films and in a PMMA polymer matrix using a picosecond pulsed laser at 532 nm results in instantaneous inscription: saturation of the first order diffraction efficiency and of the modulation amplitude of gratings were obtained in less than 1 s, while the orientation of these azodyes remains unchanged for up to 6 months.

Nonlinear refraction and absorption activity of dimethylaminostyryl substituted BODIPY dyes

Optical and nonlinear optical properties of difluoroboradiazaindacene (BODIPY) models with attached dimethylaminostyryl substituents were studied. The optical absorption and fluorescence emission of BODIPY compounds were found to be dependent on the number of dimethylaminostyryl substituents. In order to investigate the nonlinear refraction and absorption activity, the Z-scan technique was used employing a laser generating a wavelength at 532 nm with 30 ps pulse duration. The studied dimethylaminostyryl containing BODIPY compounds showed considerable nonlinear refraction and reverse saturable absorption. The BODIPY containing a pair of dimethylaminostyryl substituents demonstrated an increased third order nonlinear optical response mostly due to the extension of its conjugated length.

Synthesis and Structural Characterization of (Carbene)ruthenium Complexes Binding Nucleobases

The new (carbene)ruthenium(II) nucleobase derivatives fac,cis-[(PNP)RuCl{C(NHC4H3N2O2)(CH2Ph)}]Cl (5) and fac,cis-[(PNP)RuCl{C(NHC5H3N4)(CH2Ph)}]Cl (6) [PNP = CH3CH2CH2N(CH2CH2PPh2)2] were synthesised by treating (vinylidene)ruthenium(II) complex fac,cis-[(PNP)RuCl2{C=C(H)Ph}] (1) with 5-aminouracil or adenine, respectively. Both complexes were characterized by spectroscopic techniques (IR and NMR) and elemental analyses, which confirmed the formation of the aminocarbene moieties incorporating 1 equiv. of the nucleobase in the complex framework. Crystal and molecular structure determination by X-ray diffraction analysis of the uracil derivative 5 revealed a very unusual O-coordination of the exocyclic C=O group on the C(4) atom of the uracil ring to the ruthenium atom leading to an unprecedented six-membered aminocarbene metallacycle. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

A new route to iron(0) thiocarbonyl complex involving desulphurization of the Fe(η2-CS2R)+ cation with P-n-Bu3. Crystal structure of Fe(CS)(CO)2(PPh3)2

Abstract Reaction of [Fe(η 2 -CS 2 R)(CO) 2 (PPh 3 ) 2 ][X] (R = CH 3 , CH 2 Ph; X − = PF 6 − , I − ) with P-n-Bu 3 or PEt 3 gives Fe(CS)(CO) 2 (PPh 3 ) 2 ( 3a ); (ν(CS) 1235 cm −1 ; δ( 13 C) 324.28 ppm). The structure of 3a has been determined by X-ray diffraction. Crystal data are: a 18.821(5), b 12.113(3), c 18.149(5) A, β 117.76(6)°, monoclinic, space group P 2 1 , Z = 4. The structure is a trigonal-bypyramid with equatorial CS group, trans PPh 3 ligands, a FeC(S) bond distance of 1.768(8) and a CS bond distance of 1.563(8) A.

Switching of excited states in cyclometalated platinum complexes incorporating pyridyl-acetylide ligands (Pt–CC–py): a combined experimental and theoretical study

This article presents the design of cyclometalated platinum(II) complexes incorporating pyridyl-appended acetylide ligands of the form Pt–CC–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)(–CC–py), 2, which can undergo protonation at the pyridyl N; its cationic N-methylated derivative [Pt(t-Bu2phbpy)(–CC–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⁁N⁁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+2+). 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⁁N⁁C ligand to the pyridyl acetylide.

Metal-induced dimensionality tuning in a series of bipyrimidine-based ligands: a tool to enhance two-photon absorption

We report the synthesis, the photophysical and the two-photon absorption (2PA) properties of a series of octupolar bipyrimidine-based ligands incorporating N-substituted amines as terminal donor groups. The effect of replacing phenylvinylene π-conjugated linkers by fluorenylvinylene ones was also investigated. The linear absorption spectrum of these compounds is dominated by an intensive charge transfer band which is sensitive to N-substitution and the π-bridge nature. The excitation anisotropy spectrum indicates that this band encompasses multiple S0 → Sn transitions, whose occurrence is well rationalized on the basis of the Frenkel exciton model. The 2PA spectrum also corroborates the presence of several electronic transitions. In apolar or moderately polar medium, excited ligands mainly deactivate through a highly emissive intramolecular charge transfer (ICT) state localized within a single branch of the chromophore. In highly polar medium, the solvent-induced stabilization of the low emissive twisted intramolecular charge transfer (TICT) state leads to a severe quenching of the fluorescence. The same mechanism is observed upon complexation with Zn2+. According to single-crystal X-ray analyses, metal-induced planarization of the bipyrimidine chelating site was observed for the short length ligands. Such a dimensional change from D2d to D2h symmetry leads to a decrease of 2PA cross-sections with respect to the free ligands. A divergent effect is observed for the complex with the long length ligand since the three-dimensional structure is maintained which induces a sizeable increase of the 2PA cross-section with a maximum value of up to 2000 GM.

UV-Induced Micropatterning of Complex Functional Surfaces by Photopolymerization Controlled by Alkoxyamines

We report on the use of an alkoxyamine (AA) for fabrication of functional micropatterns with complex structures by UV mask lithography. The living character of the polymer surface and the vertical spatial control of the repolymerization reaction from few tens of nanometers to few micrometers were demonstrated. The impact of the main parameters governing the controlled polymerization and the reinitiation process activated by light or heat was investigated. Micropatterning is shown to be a powerful method to investigate the physicochemical molecular phenomena. It is possible to control the polymer microstructure thickness from few tens of nanometers to few micrometers. In the last section, some applications are provided showing the potential of the AA for generating covalently bonded hydrophilic/hydrophobic micropatterns or luminescent surfaces. This demonstrates the high versatility and interest of this route.

Study of surface relief gratings on azo organometallic films in picosecond regime.

Materials for optical data storage and optical information processing must exhibit good holographic properties. Many materials for these applications have been already proposed. Here we describe a grating inscription process characterized by short inscription time and long-time stability. A series of ruthenium-acetylide organometallic complexes containing an azobenzene fragment were synthesized. Photo-induced gratings were produced by short pulse (16 ps, 532 nm) laser irradiation. The surface relief gratings formed at the same time were observed by atomic force microscope. In this work, we highlight the short inscription times brought into play as well as the good temporal stability of these gratings stored at room temperature. We study the influence of the polarization states and the light intensity of writing beams on the dynamics of the surface relief gratings formation and we compare these results with those of a known representative of azobenzene derivative (Disperse Red 1). Lastly, we show that it is possible to write two-dimensional surface relief gratings.