Luminescence modulation in liquid crystalline phases containing a dispiro[fluorene-9,11′-indeno[1,2-b]fluorene-12′,9′′-fluorene] core

International audienceA luminescent liquid crystalline compound containing a bulky dispiro[fluorene-9,11′-indeno[1,2-b]fluorene-12′,9′′-fluorene] has been designed and synthesized by di-substitution of a bromo derivative with N-(4-ethynylphenyl)-3,4,5-tris(hexadecyloxy)benzamide fragments. This di-substituted 3π-2spiro derivative forms stable and well-organized mesophases over large temperature ranges. Combination of DSC, POM and SAXS analyses has revealed the formation of a lamellar mesophase between 60 and 150 °C followed by another mesophase with a 2-dimensional lattice of rectangular symmetry that remains up to the isotropization point near 225 °C. In the original molecular packing model deduced from SAXS, the tert-butyl terminal groups fill the centre of hollow columns constituted by both the dihydro(1,2-b)indenofluorene and benzamide fragments and separated from each other by the surrounding aliphatic tails. The merging of the columns yielding the lamellar phase turned out to be governed by the dynamics of both, the micro-phase segregation process and the network of hydrogen bonds. In the various mesomorphic states and in solution, a strong luminescence was observed. The emission spectrum however depends on temperature and drastically changes between both mesophases and the isotropic liquid. In particular, a strong modulation of the emission wavelength occurs at the isotropic to 2D phase transition. This luminescence modulation results from an enhanced contribution of the vibronic peaks at higher energies in the emission profile. The compound was also found to be soluble in 5CB and was integrated in a guest-host LC cell, allowing efficient modulation of the photoluminescence polarization, in the presence or absence of an electrical field

Redox-active proligands from the direct connection of 1,3-dithiol-2-one to tetrathiafulvalene (TTF): syntheses, characterizations and metal complexation

International audienceIn the search for novel tetrathiafulvalene-substituted dithiolene ligands, two tetrathiafulvalene (TTF) molecules directly connected to 1,3-dithiol-2-one fragments have been synthesized and characterized by single crystal X-ray diffraction, electrochemical and spectroscopic analyses. TTF1 was obtained, in moderate yield, by the cross-coupling of 4,5-bis(methylthio)-1,3-dithiole-2-one with 4,4′-bis(1,3-dithiole-2-one) in triethylphosphite, whereas for TTF2, the 1,3-dithiol-2-one fragment was introduced, in high yield, by an original reaction of the alkyne group of an ethynyl TTF (Me3TTF-C[triple bond, length as m-dash]CH) with xanthogen in the presence of a radical initiator. Opening of the 1,3-dithiol-2-one fragments with sodium methanolate leads to the formation of two new 1,2-dithiolate ligands functionalized with redox-active TTF moieties, which can efficiently coordinate metals. As an illustration, two original heteroleptic bis(cyclopentadienyl)dithiolene titanium complexes were isolated and characterized

New difluoro-boradiazaindacene shaped with gallate platforms

International audienc

Cis and trans-bis(tetrathiafulvalene-acetylide) platinum(II) complexes: syntheses, crystal structures, and influence of the ancillary ligands on their electronic properties.

International audienceA series of four platinum(II) complexes bearing two tetrathiafulvalene acetylide ligands coordinated either cis or trans to the metal center are reported: cis-Pt(bipy)(C≡CMe(3)TTF)(2), cis-Pt(tBu(2)bipy)(C≡CMe(3)TTF)(2), cis-Pt(dppe)(C≡CMe(3)TTF)(2) and trans-Pt(PPh(3))(2)(C≡CMe(3)TTF)(2). The X-ray diffraction studies of the four complexes are reported and discussed. The electrochemical investigations carried out by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) evidenced different redox behavior as a function of the ancillary ligand. Only for the cis-Pt(dppe)(C≡CMe(3)TTF)(2) complex is the first oxidation wave resolved (ΔE = 70 mV) into two one-electron processes. Spectroelectrochemical investigations performed on the four complexes did not evidence any electronic interactions between the two organic electrophores. The splitting of the first oxidation wave observed in cis-Pt(dppe)(C≡CMe(3)TTF)(2) is mainly explained by the non-equivalence of the two TTF moieties induced by the geometrical constraint imposed by the ancillary dppe ligand as found by density functional theory calculations

Probing magnetic interactions in columnar phases of a paramagnetic gold dithiolene complex

International audienceA novel radical gold dithiolene complex exhibits a hexagonal columnar mesophase, as confirmed by optical microscopy , DSC analysis and X-ray diffraction . The extent of delocalization of the spin density in such a complex was analyzed by EPR . Temperature dependent magnetization measurements reveal that the global magnetic moment is remarkably affected at the liquid-crystalline phase transition with a marked hysteresis signature, rare behavior among the few described paramagnetic discotic phases. In addition, these molecules were found to strongly aggregate in solution into one-dimensional fibers with a mean diameter of 60 nm extending over micrometres, leading to the formation of gel-like structures. These fibers are stable and can be isolated on surfaces. The gelation of the system can also be detected by temperature-dependent magnetic measurements

NOUVEAUX FLUIDES COMPLEXES MINERAUX (ASPECTS STRUCTURAUX, ORGANISATION MACROSCOPIQUE, ASPECTS SYNTHETIQUES)

NANTES-BU Sciences (441092104) / SudocSudocFranceF

Ionic self-assembly and red-phosphorescence properties of a charged platinum(II) 8-quinolinol complex associated with ammonium-based amphiphiles

A series of ionic associates based on the platinum(II) chelate of 5-sulfo-8-quinolinol, [Pt(qS)], and ammonium-based amphiphiles is described. At variance with the prototypical neutral complex Pt(q) (q=8-quinolinol), these dianionic fluorophores, functionalized at the periphery with sulfonate groups, can be associated by the ionic self-assembly approach with various ammonium cations, such as (HC)MeN (n=12, 16, 18) or complex ammonium cations carrying three C carbon chains (n=12, 14, 16) and an additional amide group. Investigations of their luminescence properties in solution, in the solid state, and, when possible, in thin films revealed that the phosphorescence properties in condensed phases are directly correlated to intermolecular interactions between the luminescent [Pt(qS)] centers. Of particular interest is also the formation of a columnar liquid-crystalline phase around room temperature (between -25 and +180 C), as well as the very good film-forming ability of some of these fluorophores from organic solvents.The CNRS and the University of Rennes 1 are gratefully acknowledgedfor financial support. J.B. thanks financial support by the MINECO, Spain, under the projectCTQ2012-35692, which included FEDER funding.Peer Reviewe

(Photo)Thermal Stimulation of Functional Dithiolene Complexes in Soft Matter

International audienceSquare-planar bis(dithiolene) complexes are characterized with a planar delocalized structure and a strong and tunable near infrared (NIR) absorption; they are highly stable under laser irradiation, and their conversion efficiency (light to heat) reaches up to 40-50 %. Their involvement in soft matter, namely liquid crystals, gels, and nanoparticles, opens many possibilities to control the actual state of a material, particularly under light irradiation. Thus, liquid crystalline phases can easily be modified, (i) with temperature to modulate the extended magnetic interactions of paramagnetic complexes, or (ii) under laser irradiation to unravel these remarkable photothermal properties, toward the development of light-responsive materials. Dithiolene complexes can be also functionalized to produce very effective gelation agents, while the photothermal effect can be used to destabilize at will their supramolecular organization. Besides photothermal therapy, new therapeutic agents were also developed for photo-controlled drug delivery and bioimaging, combining chemotherapy and phototherapy. Hydrophobic complexes were accordingly designed for their encapsulation in block copolymer nanoparticles for photothermal therapy and photo-controlled drug delivery under laser irradiation. This class of complexes can be also used as exogenous contrast agents for photoacoustic bioimaging