Isabelle Ledoux-Rak

Push–pull chromophores based on 2,2′-bi(3,4-ethylenedioxythiophene) (BEDOT) π-conjugating spacer

Abstract Replacement of 2,2′-bithiophene by BEDOT in push–pull NLO-phores produces a red shift of the absorption maximum accompanied with a large increase of the quadratic nonlinear optical susceptibility.

Synthesis, spectral, structural, second-order nonlinear optical properties and theoretical studies on new organometallic donor-acceptor substituted nickel(II) and copper(II) unsymmetrical Schiff-base complexes.

The synthesis, spectroscopic and structural characterization, linear and nonlinear optical properties, as well as the electrochemical behavior of a series of robust neutral binuclear M[Fc-C(O)CH=C(CH(3))N-X-N=CH-(2-O,5-R-C(6)H(3))] (M = Ni (4), Cu (5), X = o-C(6)H(4), R = H; M = Ni (9), X = CH(2)CH(2), R = OH), and their corresponding ionic trinuclear [M{Fc-C(O)CH=C(CH(3))N-X-N=CH-(eta(6)-2-O,5-R-C(6)H(3))RuCp*}][PF(6)] (6, 7, 10), M[ONNO]-type unsymmetrical Salophen and salen complexes featuring ferrocenyl (Fc) donor and the mixed sandwich acceptor [Cp*Ru(eta(6)- salicylidene)](+) as a push-pull moiety are reported in this paper (Fc = CpFe(eta(5)-C(5)H(4)); Cp = eta(5)-C(5)H(5); Cp* = eta(5)-C(5)Me(5)). The single-crystal X-ray structure of the bimetallic iron-nickel derivative 4 indicates a bowed structure of the unsymmetrical Schiff base skeleton. The Ni(II) ion is tetracoordinated in a square planar environment, with two nitrogen atoms and two oxygen atoms as donors. The new metalloligand [Fc-C(O)CH=C(CH(3))N(H)CH(2)CH(2)N=CH-(2,5-(OH)(2)C(6)H(3))] (8) obtained from the Schiff base condensation of 2,5-dihydroxobenzaldehyde with the half-unit precursor, Fc-C(O)CH=C(CH(3))N(H)CH(2)CH(2)NH(2) (2), is reported with its crystal structure showing partial delocalization of the heteroconjugated [O-C-C-C-N] frameworks with a dihedral angle between the respective planes of 60.76 degrees. Second order nonlinear optical (NLO) measurements were achieved using the Harmonic Light Scattering technique to probe the role of the M[ONNO] chromophores and of the pi-complexation of the salicylidene ring in the nonlinearity. All the complexes exhibit a second-order nonlinear response increasing with the nuclearity, the hyperpolarizability (beta) value of the trinuclear complex 10 being 1.5 time larger than that of the metalloligand 8 (beta = 155 x 10(-30) esu). A rationalization of the structural, electronic, and redox properties of the title compounds is provided, based on a theoretical investigation at the density functional theory (DFT) level. Their UV-visible spectra has been assigned with the help of time-dependent (TD) DFT calculations. They are dominated by LMCT, MLCT, and pi-pi* transitions.

ABAB homoleptic bis(phthalocyaninato)lutetium(III) complex: toward the real octupolar cube and giant quadratic hyperpolarizability.

The concept of octupolar molecules has considerably enlarged the engineering of second-order nonlinear optical materials by giving access to 2D and 3D architectures. However, if the archetype of octupolar symmetry is a cube with alternating donor and acceptor groups at the corners, no translation of this ideal structure into a real molecule has been realized to date. This may be achieved by designing a bis(phthalocyaninato)lutetium(III) double-decker complex with a crosswise ABAB phthalocyanine bearing alternating electron-donor and electron-acceptor groups. In this communication, we present the first step toward this goal with the synthesis, crystal structure determination, and measurement of the molecular first-order hyperpolarizability β by harmonic light diffusion, of an original lutetium(III) sandwich complex displaying the required ABAB-type alternation for one face of the cube. This structure is characterized by an intense absorption in the near-IR due to an intervalence transition and exhibits the highest quadratic hyperpolarizability ever reported for an octupolar molecule, √ = 5750 × 10(-30) esu.

NIR to visible up-conversion, infrared luminescence, thermoluminescence and defect centres in Y2O3?:?Er phosphor

Er3+ doped Y2O3 phosphor was prepared by the solution combustion method and characterized using powder x-ray diffraction and energy-dispersive analysis of x-ray mapping studies. Room temperature near infrared (NIR) to green up-conversion (UC) emissions in the region 520–580 nm {(2H11/2, 4S3/2) →4I15/2} and red UC emissions in the region 650–700 nm (4F9/2 →4I15/2) of Er3+ ions have been observed upon direct excitation to the 4I11/2 level using ~972 nm laser radiation of nanosecond pulses. The possible mechanisms for the UC processes have been discussed on the basis of the energy level scheme, the pump power dependence as well as based on the temporal evolution. The excited state absorption is observed to be the dominant mechanism for the UC process. Y2O3 : Er exhibits one thermally stimulated luminescence (TSL) peak around 367 °C. Electron spin resonance (ESR) studies were carried out to study the defect centres induced in the phosphor by gamma irradiation and also to identify the centres responsible for the TSL peak. Room temperature ESR spectrum of irradiated phosphor appears to be a superposition of at least three distinct centres. One of them (centre I) with principal g-values g|| = 2.0415 and g⊥ = 2.0056 is identified as centre while centre II with an isotropic g-factor 2.0096 is assigned to an F+-centre (singly ionized oxygen vacancy). Centre III is also assigned to an F+-centre with a small g-factor anisotropy (g|| = 1.974 and g⊥ = 1.967). Additional defect centres are observed during thermal annealing experiments and one of them appearing around 330 °C grows with the annealing temperature. This centre (assigned to an F+-centre) seems to originate from an F-centre (oxygen vacancy with two electrons) and the F-centre appears to correlate with the observed TSL peak in Y2O3 : Er phosphor. The trap depth for this peak has been determined to be 0.97 eV from TSL data.

Fluorinated β-Diketonate Diglyme Lanthanide Complexes as New Second-Order Nonlinear Optical Chromophores: The Role of f Electrons in the Dipolar and Octupolar Contribution to Quadratic Hyperpolarizability

The second-order nonlinear optical (NLO) properties of [Ln(hfac)(3)(diglyme)] (hfac = hexafluoroacetylacetonate; diglyme = bis(2-methoxyethyl)ether; Ln = La, Ce, Pr, Sm, Eu, Gd, Er, Lu) complexes have been investigated by a combination of electric-field second harmonic generation (EFISH) and harmonic light scattering (HLS) techniques, providing evidence for the relevant role of f electrons in tuning the second-order NLO response dominated by the octupolar contribution. These lanthanide NLO chromophores allow a clean valuation of the influence of f electrons on the quadratic hyperpolarizability and on its dipolar and octupolar contributions. Molecular quadratic hyperpolarizability values measured by the EFISH method, beta(EFISH), initially increase rapidly with the number of f electrons, the value for the Gd complex being 11 times that of the La complex, whereas this increase is much lower for the last seven f electrons, the beta(EFISH) value of the Lu complex being only 1.2 times that of the Gd complex. The increase of beta(HLS), which is dominated by an octupolar contribution, is much lower along the Ln series. Remarkably, the good beta(HLS) values of these simple systems, well known for their luminescence properties, are reached at no cost of transparency.

Submicrometer 3D structures fabrication enabled by one-photon absorption direct laser writing

We demonstrate a new 3D fabrication method to achieve the same results as those obtained by the two-photon excitation technique, by using a simple one-photon elaboration method in a very low absorption regime. Desirable 2D and 3D submicrometric structures, such as spiral, chiral, and woodpile architectures, with feature size as small as 190 nm have been fabricated, by using just a few milliwatts of a continuous-wave laser at 532 nm and a commercial SU8 photoresist. Different aspects of the direct laser writing based on ultralow one-photon absorption (LOPA) technique are investigated and compared with the TPA technique, showing several advantages, such as simplicity and low cost.

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.

Vertically Coupled Polymer Microracetrack Resonators for Label-Free Biochemical Sensors

We report on the efficient design and fabrication of polymeric microracetrack optical resonators for label-free biosensing purposes. Vertically-coupled microresonators immersed in deionised water display high Q-factors (>;35000)and finesses up to 25. A surface sensing experiment performed with these microresonators using 5-TAMRA cadaverine as a test molecule demonstrated both the high sensitivity and low detection limit of our device.

Electrochemical, linear optical, and nonlinear optical properties and interpretation by density functional theory calculations of (4-N,N-dimethylaminostyryl)-pyridinium pendant group associated with polypyridinic ligands and respective multifunctional metal complexes (Ru(II) or Zn(II)).

The synthesis, linear optical and nonlinear optical properties, as well as the electrochemical behavior of a series of pro-ligands containing the 4-(4-N,N-dimethylaminostyryl)-1-methyl pyridinium (DASP(+)) group as a push-pull moiety covalently linked to terpyridine or bipyridine as chelating ligands are reported in this full paper. The corresponding multifunctional Ru(II) and Zn(II) complexes were prepared and investigated. The structural, electronic, and optical properties of the pro-ligands and the ruthenium complexes were investigated using density functional theory (DFT) and time-dependent (TD) DFT calculations. A fairly good agreement was observed between the experimental and the calculated electronic spectra of the pro-ligands and their corresponding ruthenium complexes. A quenching of luminescence was evidenced in all ruthenium complexes compared with the free pro-ligands but even the terpyridine-functionalized metal complexes exhibited detectable luminescence at room temperature. Second order nonlinear optical (NLO) measurements were performed by Harmonic Light Scattering and the contribution of the DASP(+) moieties (and their relative ordering) and the metal-polypyridyl core need to be considered to explain the nonlinear optical properties of the metal complexes.

Tuning the Dipolar Second‐Order Nonlinear Optical Properties of Cyclometalated Platinum(II) Complexes with Tridentate N^C^N Binding Ligands

Appropriate functionalization of the cyclometalated ligand, L, and the choice of the ancillary ligand, X, allows the dipolar second-order nonlinear optical response of luminescent [PtLX] complexes--in which L is an N^C^N-coordinated 1,3-di(2-pyridyl)benzene ligand and X is a monodentate halide or acetylide ligand--to be controlled. The complementary use of electric-field-induced second-harmonic (EFISH) generation and harmonic light scattering (HLS) measurements demonstrates how the quadratic hyperpolarizability of this appealing family of multifunctional chromophores, characterized by a good transparency throughout much of the visible region, is dominated by an octupolar contribution.