Star-shaped molecules as functional materials based on 1,3,5-benzenetriesters with pendant 1,3,4-thiadiazole groups: liquid crystals, optical, solvatofluorochromic and electrochemical properties

New molecular structures consisting of a C3 star-shaped 1,3,5-benzene unit as a central core, and three pendant 2-phenyl-5-(di-, and/or tri-n-alkoxyphenyl)-1,3,4-thiadiazole arms, containing ester connecting groups, variable number and positions of linear alkoxy chains (2an, 2b10 and 2c10) were synthesised. The mesomorphic properties were studied by differential scanning calorimetry, polarised optical microscopy and X-ray diffraction. Compounds bearing nine peripheral n-decyloxy chains (2a10) and nine peripheral n-dodecyloxy chains (2a12) form an enantiotropic hexagonal columnar phase, whereas their homologue 2a14, bearing nine peripheral n-tetradecyloxy chains, does not show mesomorphic behaviour. Compound bearing six peripheral n-decyloxy chains, which are in the 3,4-positions of the terminal benzene rings (2c10) does not show mesomorphic properties, whereas its analogous compound 2b10, bearing six n-decyloxy chains in the 3,5-positions of the terminal benzene rings, is liquid. The electrochemical behaviour of the liquid crystalline compounds 2a10 and 2a12 was investigated by cyclic voltammetry which revealed the hole-blocker character of these compounds. The ultraviolet–visible absorption and emission properties of the compounds 2an, 2b10 and 2c10 have been investigated. Photophysical studies were carried out in solution and in film. In addition, solvatofluorochromism studies were performed with compound 2a12 as a representative member of the compounds of series 2.This research was supported by FONDECYT (1100140), ‘Vicerrectoría de Investigación’ of the University of Concepción, and the Spanish project CTQ2015-70174-P.Peer reviewe

Synthesis of new benzobisthiazole materials and a study of their mesomorphic and luminescence properties

Novel tetra- and hexacatenar materials based on benzobisthiazole derivatives have been synthesised (4a-c, 5a-c and 6a-c) and their mesomorphic properties have been studied by differential scanning calorimetry, polarised optical microscopy and X-ray diffraction. All compounds in series 4a-c display an enantiotropic hexagonal columnar phase, whereas their analogous compounds in series 5a-c did not show mesomorphic behaviour. Compound 6a displays an unidentified monotropic columnar phase, whereas compounds 6b and 6c show an enantiotropic rectangular columnar mesophase. The mesomorphic properties were found to be dependent on the length, position and number of alkoxy chains attached at the end of the rigid core. These compounds also show photoluminescence properties in the visible region and have good quantum yields. A thermogravimetric analysis was also performed. © 2013 Taylor & Francis.This research was supported by FONDECYT (1100140), CONICYT, ‘Dirección de Investigación’ of the University of Concepción, the Spanish project CTQ2012-35692 and FEDER funds.Peer Reviewe

New polycatenar Schiff bases derived from 1,3,4-thiadiazole: synthesis, mesomorphism and luminescence behaviour

Two new series of columnar liquid crystal materials based on tetra- and hexacatenar Schiff bases were synthesised by reaction of 4-aminophenyl-1,3,4-thiadiazole derivatives with terephthalaldehyde (series 2a–f) and with 2,5-thiophenedicarbaldehyde (series 3a–f). The mesomorphic properties of these compounds were studied by differential scanning calorimetry (DSC), polarised optical microscopy (POM) and X-ray diffraction (XRD). The mesomorphic behaviour was found to be dependent on the nature of the central ring (benzene in series 2a–f, thiophene in series 3a–f), on length and on number of alkoxy chains. Both tetra- and hexacatenar compounds in series 2a–f display an enantiotropic hexagonal columnar phase. Whereas, in the case of the series 3, only the tetracatenar Schiff bases (3a, 3c and 3e) display enantiotropic hexagonal columnar mesomorphism, hexacatenar Schiff bases (3b, 3d and 3f) do not show mesomorphic properties. Photophysical studies were realised in solution and in solid state. Also, a thermogravimetric analysis was performed. A fibre obtained from compound 3b was analysed by POM showing that the mesophase is maintained in the fibre.This research was supported by FONDECYT [grant number 1100140], CONICYT, ‘Vicerrectoría de Investigación of the University of Concepción, the Spanish project CTQ2015-70174-P, Conicyt-Regional Basal project R08C1002 Chile and CIPA, CONICYT Regional, GORE BIO BIO PRFC0002.Peer Reviewe

Catalytic study of heterobimetallic rhodium complexes derived from partially alkylated s-indacene in dehydrogenative silylation of olefins

International audienceThis work describes the catalytic study of heterobimetallic rhodium compounds derived from partially alkylated s-indacene in dehydrogenative silylation of olefins in order to elucidate as much as possible the effects of: solvent, temperature, chemical substrates, olefin effect, silane effect, and secondary metallic fragment. The rhodium complexes, anti-[Cp*Fe-s-Ic′-Rh(COD)] 1, anti-[Cp*Ru-s-Ic′-Rh(COD)] 2, and syn-[Cp*Ru-s-Ic′-Rh(COD)] 2′ (with s-Ic′: 2,6-diethyl-4,8-dimethyl-s-indaceneiide) were previously synthesized and characterized, and were compared with the catalytic activity of the complexes previously reported; monometallic [(COD)Rh-s-Ic′H] 3, and homobimetallic anti-[{(COD)Rh}2-s-Ic′] 4, and syn-[{(COD)Rh}2-s-Ic′] 4′.The heterobimetallic complexes show a high activity and selectivity for the dehydrogenative silylation of styrene and these complexes show also the presence of a cooperative effect between both metallic centers, which is evidenced when compared with monometallic complex

Obtention of biocompatible hydrogels containing PEGs/silicon fatty blocks with potential use as A controlled release system

Novel crosslinked polyesters were designed to obtain hydrogels friendly with the environment and able to display potential biologic applications. Through polycondensation reactions, the synthesis used polyethylene glycols (PEGs) of different molecular weights and a silylated fatty methyl ester obtained from methyl 10-undecenoate, a derivative of castor oil. Depending on the PEGs molecular weights, a series of crosslinked polyesters were obtained and characterized by spectroscopic methods. Thanks to double quantum coherence (DQ) proton experiments, the synthesis was optimized by determining the highest crosslink density achieved from the parameter “Constant residual dipole coupling” (D), which is proportional to the crosslink density. These amphiphilic polyesters showed biocompatible properties according to ISO 10993-5. Besides, they could form hydrogels structurally confirmed by scanning electron microscopy. The swelling capacity was remarkable, depending on the PEGs molecular weights. The studies of encapsulation and release using rhodamine as host molecules revealed very conclusive and promising results, demonstrating that it was possible to control the releasing time by modifying the molar mass of the PEGs used in the synthesis. This critical outcome could be considered an essential parameter for tailoring materials for different drug or fertilizer release applications.The authors thank the project VRID 216.023.052-1.0, “Universidad de Concepción”,Chile for their academic support, and Dr. Mar Fernán- dez for biocompatibility analysis carried out in the “Departamento de Nanomateriales y Biomateriales Polimericos ICTP (CSIC)” España

Hybrid photoluminescent materials containing a benzobisthiazole core for liquid crystal and gel applications

Tetra- and hexacatenar amide compounds containing a linear centrosymmetric benzobisthiazole core were synthesized with good yields. These compounds were characterized and their structures confirmed by elemental analysis, and FT-IR, Maldi mass and NMR spectroscopy. All compounds exhibited excellent thermal stability up to 330 °C. The tetracatenar series containing a double substitution in the meta positions did not show mesomorphic behaviour, whereas the hexacatenar and tetracatenar series having a double substitution in the meta and para positions showed liquid crystal properties with optical textures typical of columnar mesophases corroborated by POM analysis. The mesomorphic properties were dependent on the length, number and position of alkoxy chains attached at the end of the rigid core. XRD studies of the hexacatenar series showed the hexagonal columnar structure of the mesophases. Photoluminescence properties in solution were observed in the visible region, with good quantum yields. In the solid state, these compounds behave as blue emitters and they are able to change colour with acid or base addition. The hexacatenar benzobisthiazole compound with an alkoxy chain of 14 carbons presented properties of a supergelator in chloroform, leading to the formation of a fluorescent organogel material with fluorescence emission in the blue region.The authors thank the Projects ‘‘Fondecyt No. 1100140 (M. P.) and 1140454 (S. A. S.)’’ and the ‘‘Vice-Rectoria de Investigacion’’ of Concepcion University (Chile) for their financial support. J. Barbera acknowledges financial support from MINECO, Spain (project CTQ2015-70174-P).Peer reviewe