First Direct Evidence of an ortho-Lithiated Aryloxetane: Solid and Solution Structure, and Dynamics

Oxetanes are key synthons for asymmetric synthesis and also effective in directing ortho-lithiation. This work first reports the solution and the solid-state structure of an ortho-lithiated aryloxetane (1-Li) in the presence/absence of a bidentate ligand such as N,N,N′,N′-tetramethylethylenediamine (TMEDA). Single crystal X-ray diffraction analysis of 1-Li revealed a singular crystallographic structure in which the asymmetric unit comprises a core where the lithium atom is coordinated to the nitrogen atom of half a molecule of TMEDA and intramolecularly stabilised by the oxetane ring oxygen. This aggregation state is unprecedented in ortho-lithiated arenes. Variable temperatures multinuclear magnetic resonance (1H, 7Li, 13C) mono- and two-dimensional NMR studies and DFT computations supported the coexistence in solution of three chelated bridged dimeric aggregates, in slow equilibration at 180 K. The major isomer is an heterochiral aggregate on the basis of 1H,7Li-HOESY and 1H,1H-NOESY experiments. Conclusions were supported by the preparation of enantiomerically enriched (S)-1-Li. The privileged formation of homochiral aggregates from racemic mixtures may also have implications for the development of chiral resolution processes

Functionalization of mono- and bimetallic MIL-100(Al,Fe) MOFs by ethylenediamine: post-functionalization, Brønsted acido-basicity and unique CO2 sorption behaviour

The metal sites of MIL-100(Fe), MIL-100(Fe,Al) and MIL-100(Al) MOFs were decorated with ethylenediamine (EN). Interestingly, the Al-containing MOFs presented hierachized porosity, and their structural integrity was maintained upon functionalization. Solution and solid-state NMR confirmed the grafting efficiency in the case of MIL-100(Al) and the presence of a free amine group. It was shown that MIL-100(Al) can be functionalized by only one EN molecule by trimeric Al3O cluster unit, whereas the two other aluminium sites are occupied by an hydroxyl and a water molecule. The -NH2 sites of the grafted ethylenediamine can be used for further post-functionalization through amine chemistry and is responsible for basicity of the functionalized material. Furthermore, the presence of coordinated water molecules on the Al-MOF is responsible for simultaneous Brønsted acidity and for a unique carbon dioxide sorption mecanism, that distinguishes this material from its iron and chromium counterparts

Organic chromophores based on a fused Bis-Thiazole core and their application in Dye-Sensitized Solar Cells

Four new D-π-A organic dyes incorporating either a thiazolo[ 5,4-d]thiazole bicyclic system (TTZ1–2) or a benzo[1,2- d:4,5-d]bisthiazole tricyclic unit (BBZ1–2) have been synthesized and fully characterized. The key steps of the synthesis include an efficient MW-assisted preparation of the thiazolo-[5,4-d]thiazole core and selective functionalization of two different dihalothienyl derivatives through Suzuki coupling. All the compounds showed photo- and electrochemical properties compatible with their employment in dye-sensitized solar cells. In addition, their electronic structure and transitions were investigated by means of TD-DFT calculations. Dye-sensitized solar cells fabricated with dye TTZ1 yielded an average power conversion efficiency corresponding to 43 and 60% of the performances recorded under the same conditions for cells containing reference dyes N3 and D5, respectively. Efficiency measurements and electrochemical impedance spectroscopy (EIS) experiments indicated that use of chenodeoxycholic acid (CDCA) as a co-adsorbent was beneficial to disrupt dye-dye interactions and slow down recombination processes within the cells, thus allowing power conversion efficiencies up to 3.53% to be obtained

Recent Advances in Synthesis of P-BH3 Compounds

International audienceThis chapter is dedicated to the main achievements since 2007 regarding the synthesis of BH3-phosphorus complexes. Among this class of compounds, phosphine-boranes are the most studied derivatives, mainly as valuable surrogates of phosphines, enabling easy handling and purification. Contrarily, metal phosphido-boranes were so far only considered as in situ intermediates in the P-functionalization of secondary phosphine-boranes. Thorough investigations of their structures as well as their chemical properties have been recently reported. Besides, phosphine-boranes and their phosphides, new families of phosphorus-BH3 complexes, have emerged as useful precursors of new structures in the asymmetric series. New routes toward optically active phosphinous-acid boranes and their esters were developed and applied to the synthesis of enantiopure P-stereogenic secondary and tertiary phosphine-boranes. The stereoselective synthesis of P-stereogenic aminophosphine-boranes, precursors of a new class of chiral ligands has been shortly reported. Studies dealing with the synthesis and reactivity of phosphonite-boranes were successfully applied to the development of efficient syntheses of functionalized H-phosphinates, compounds difficult to access by other routes