Loïc Toupet

Phosphole‐Containing π‐Conjugated Systems: From Model Molecules to Polymer Films on Electrodes

Two series of 2,5-dipyridyl- and 2,5-dithienylphosphole derivatives containing sigma3- or sigma4-P atoms were prepared, and their optical (UV/Vis absorption, fluorescence spectra) and electrochemical properties were systematically evaluated. These physical properties depend mainly on the natures of the 2,5-substituents and of the phosphorus moiety, and they revealed that these compounds contain extended pi-conjugated systems. Structure-property relationships were established on the basis of these experimental data and ab initio calculations on the parent molecules. The limited aromatic character and low-lying LUMO of the phosphole ring appear to be crucial for achieving a highly delocalised pi system. Electrooxidation of 2,5-dithienylphosphole derivatives affords electroactive films with low optical band gaps. As observed for the corresponding monomers, the optical and electrochemical properties of the polymers can be varied over a wide range by modifying the nature of the phosphorus moiety.

Bis-aminals: efficient tools for bis-macrocycle synthesis

Tetraazamacrocyclic bis-aminals prove to be excellent tools for the synthesis of symmetrical, dissymmetrical or functionalized bis-tetraazamacrocycles. The key feature of the process is the separation of insoluble mono- or bis-quaternary ammonium salts from solution during the course of the alkylation reaction.

First ruthenium complexes with a chelating arene carbene ligand as catalytic precursors for alkene metathesis and cycloisomerisation

Electron-rich carbene precursors 2 and 3, containing the imidazolidin-2-ylidene moiety with one (2) and two (3) pendent N-(2,4,6-trimethylbenzyl) groups, on reaction with [RuCl2(arene)]2 lead to ruthenium(II) complexes 5 and 6 containing the chelating 8-electron mixed arene–carbene ligand; the X-ray diffraction crystal structure of RuCl2{η1-CN[CH2( η6-2,4,6-Me3C6H2)]CH2CH2N(CH2CH2OMe)} 6, was established. These complexes are precursors of the unstable ruthenium-allenylidene intermediates 7 and 8, but are active catalysts either for selective catalytic alkene metathesis or cycloisomerization, depending on the nature of the 1,6-diene.

Ruthenium(IV) Complexes Featuring P,O‐Chelating Ligands: Regioselective Substitution Directly from Allylic Alcohols

Branching out: A new ruthenium(IV) complex (1), containing a P,O-chelating ligand, is an efficient precatalyst for regioselective allylations starting from various allylic alcohol derivatives.

On/Off Photoswitching in a Cyanide-Bridged {Fe2Co2} Magnetic Molecular Square

A repeatable bidirectional paramagnetic ↔ diamagnetic photomagnetic effect has been observed in the cyanide-bridged Fe-Co square complex {[Fe{B(pz)(4)}(CN)(3)](2)[Co(bik)(2)](2)}(ClO(4))(2)·3H(2)O [B(pz)(4) = tetrapyrazolylborate, bik = bis(1-methylimidazol-2-yl)ketone]. Magnetic measurements and low-temperature single-crystal X-ray diffraction experiments have shown that a complete electron transfer from the diamagnetic Fe(II)-Co(III) state to the paramagnetic Fe(III)-Co(II) metastable state is induced by 808 nm laser light irradiation, whereas the diamagnetic state is recovered in an almost quantitative yield under irradiation at 532 nm.

Concerted Spin Crossover and Symmetry Breaking Yield Three Thermally and One Light‐Induced Crystallographic Phases of a Molecular Material

Among switchable molecular materials, Fe spin-crossover (SC) complexes have been widely studied over the last decades. Their reversible low-spin (LS)Ðhigh-spin (HS) switching triggered by a change in temperature or pressure, or by light irradiation, has attracted much interest for both basic scientific understanding and potential technological applications in information storage or visual displays. In these materials, the coexistence of shortand long-range interactions between molecules yields cooperative effects such as hysteresis and/or two-step transitions. Usually, the SC phenomenon is isostructural, but in a few cases symmetry breaking occurs in the LS phase, alongside intermolecular reorganization. 5] Few examples of mononuclear molecular materials that undergo two-step SC associated with intermolecular reorganization in the broken-symmetry phase, the socalled intermediate (INT) phase, involving fractional population of the HS state, have been reported. 7] To date, the INT phase has been fully described only in very few cases by diffraction techniques, which evidenced HS–LS 9] or LS–HS– LS longor short-range ordering. Over the last ten years, we have investigated supramolecular Fe SC materials including imidazolyl groups. 8, 9,11] In view of the first-order SC evidenced in [FeH2L ](ClO4)2, [5] where H2L 2Me denotes the acyclic hexadentate N6 Schiff base bis[N-(2-methylimidazol-4-yl)methylidene-3-aminopropyl]ethylenediamine, the new SC material [FeH2L ](PF6)2, 1 has been synthesized. Here we report on its two rare types of behavior: long-range LS– HS–HS–LS ordering in the INT phase, and structural symmetry breaking in the LS phase. In addition, another symmetry-breaking process occurs on generating the photoinduced HS phase (PIHS): in the emerging field of photoinduced phase transitions, this result opens a new subject of debate, that is, the possibility of reaching different types of false ground states through light irradiation. Figure 1 shows the thermal variation of the cM T product of 1 (cM is the molar magnetic susceptibility), in the cooling and warming modes, evidencing a two-step SC process. The

Synthesis, structure and reactivity of new yttrium bis(dimethylsilyl)amido and bis(trimethylsilyl)methyl complexes of a tetradentate bis(phenoxide) ligand

Abstract The reactions of a bulky amino-methoxy bis(phenolate) ligand H2L with Y(CH2SiMe3)3(THF)2 and Y[N(SiHMe2)2]3(THF)2 under mild condition leads to the selective formation of the thermally stable complexes [L]Y(CH2SiMe3)(THF) (1) and [L]Y[N(SiHMe2)2](THF) (2). The X-ray structures revealed very similar binding of the [ONOO] ligand core to the metal for both complexes, which feature an octahedral geometry involving coordination of the methoxy side-arm of the ligand and of a remaining THF molecule. 1H-NMR spectroscopy indicates that the solid state structure of 1 and 2 is retained in hydrocarbon solutions with THF coordinated to yttrium. Alkyl complex 1 showed no activity in ethylene polymerization, presumably due to the presence of coordinated THF. The amido complex 2 catalyzed sluggishly the polymerization of methyl methacrylate to give isotactic-rich PMMA but is very active for the ring-opening polymerization of e-caprolactone.

Design and synthesis of 4,4′-π-conjugated[2,2′]-bipyridines: a versatile class of tunable chromophores and fluorophores

A series of 4,4′-disubstituted[2,2′]-bipyridines, featuring π-conjugated substituents such as donor-(acceptor-) substituted styryl, thienylvinyl, phenylimino and phenylazo groups, have been synthesized. X-Ray structures are provided for three ligands containing –CC–, –CN– and –NN– linkers, respectively. These chromophores display good to excellent thermal stabilities with decomposition temperatures of up to 350°C. The strong influence of the nature of the endgroups and π-linkers on the optical properties is discussed. The stepwise protonation of 4,4′-dibutylaminostyryl-[2,2′]-bipyridine and its coordination behavior to different metallic moieties [Zn(II), Hg(II), Pd(II), Re(I), Re(VII)] have also been investigated. It is found that the absorption and emission maxima can be easily tuned by these exogenous additives over a wide range of wavelengths (360

Novel Infinite Three‐Dimensional Networks with Highly Conjugated Polynitrile Ligands: Syntheses, Crystal Structures, and Magnetic Properties of [Cu{C[C(CN)2]3}(H2O)2]n and [Cu{C[C(CN)2]3}(en)]n (en=NH2CH2CH2NH2)

An unprecedented coordination mode for the highly conjugated cyanocarbanion [C{C(CN)2}3]2− (1) is observed in the title complexes. This ligand employs four of its six CN groups in a μ4-η4 bridging mode to form two unique three-dimensional polymers.

Electron‐Rich Iron/Ruthenium Arylalkynyl Complexes for Third‐Order Nonlinear Optics: Redox‐Switching between Three States

The new [(η(2)-dppe)(η(5)-C(5)Me(5))Fe(C≡C-1,4-C(6)H(4)C≡C)Ru(η(2) -dppe)(2) C≡C(C(6)H(5))] complex (3-H) and its hexanuclear relative [{(η(2)-dppe)(η(5)-C(5) Me(5))Fe(C≡C-1,4-C(6)H(4)-C≡C)Ru(η(2)-dppe)(2)(C≡C-1,4-C(6)H(4)C≡C)(3)(1,3,5-C(6)H(3))] (4) have been synthesized and characterized. The linear and cubic nonlinear optical properties of these compounds in their various redox states have been studied along with those of the analogous complexes [(η(2)-dppe)(η(5)-C(5)Me(5))Fe(C≡C-1,4-C(6)H(4)C≡C)Ru(η(2)-dppe)(2)R][PF(6)](n) (n=0-2; R=Cl, 2-Cl; R=C≡C(4-C(6)H(4)NO(2)),3-NO(2)). We show that molecules exhibiting large third-order nonlinearities can be obtained by assembling such dinuclear Fe/Ru units around a central 1,3,5-substituted C(6)H(3) core. These data are discussed with a particular emphasis on the large changes in their nonlinear (third-order) optical properties brought about by oxidation. Experimental and computational (DFT) evidence for the electronic structures of these compounds in their various redox states is presented using 3-H(n+) as a prototypical model. Single crystals of this complex in its mono-oxidized state (3-H[PF(6)]) provide the first structural data for such carbon-rich Fe(III) /Ru(II) heteronuclear mixed-valent (MV) systems. Although experimental evidence for the structure of the dioxidized states was more difficult to obtain, the theoretical study reveals that 3-H(2+) can be considered to have a biradical structure with two independent spins. The low-lying absorptions that appear in the near-infrared (NIR) range for all these compounds following oxidation correspond to intervalence charge-transfer (IVCT) bands for the mono-oxidized states and to ligand-to-metal charge-transfer (LMCT) transitions for the dioxidized states. These play a crucial role in the strong optical modulation achieved. The possibility of accessing additional states with distinct linear or nonlinear optical properties is also briefly discussed.