Electrical-field-induced structural change and charge transfer of lanthanide-salophen complexes assembled on carbon nanotube field effect transistor devices.

International audienceThe application of a negative gate voltage on a carbon nanotube field effect transistor decorated by a binuclear Tb(III) complex leads to the generation of a negatively charged mononuclear one, presenting an electron density transfer to the nanotube and ambipolar behaviour

Double threading through DNA: NMR structural study of a bis-naphthalene macrocycle bound to a thymine–thymine mismatch

The macrocyclic bis-naphthalene macrocycle (2,7-BisNP), belonging to the cyclobisintercalator family of DNA ligands, recognizes T–T mismatch sites in duplex DNA with high affinity and selectivity, as evidenced by thermal denaturation experiments and NMR titrations. The binding of this macrocycle to an 11-mer DNA oligonucleotide containing a T–T mismatch was studied using NMR spectroscopy and NMR-restrained molecular modeling. The ligand forms a single type of complex with the DNA, in which one of the naphthalene rings of the ligand occupies the place of one of the mismatched thymines, which is flipped out of the duplex. The second naphthalene unit of the ligand intercalates at the A-T base pair flanking the mismatch site, leading to encapsulation of its thymine residue via double stacking. The polyammonium linking chains of the macrocycle are located in the minor and the major grooves of the oligonucleotide and participate in the stabilization of the complex by formation of hydrogen bonds with the encapsulated thymine base and the mismatched thymine remaining inside the helix. The study highlights the uniqueness of this cyclobisintercalation binding mode and its importance for recognition of DNA lesion sites by small molecules

Bio‐Inspired Bimetallic Cooperativity Through a Hydrogen Bonding Spacer in CO 2 Reduction: Bio-Inspired Bimetallic Cooperativity Through a Hydrogen Bonding Spacer in CO2 Reduction

Abstract At the core of carbon monoxide dehydrogenase (CODH) active site two metal ions together with hydrogen bonding scheme from amino acids orchestrate the interconversion between CO 2 and CO. We have designed a molecular catalyst implementing a bimetallic iron complex with an embarked second coordination sphere with multi‐point hydrogen‐bonding interactions. We found that, when immobilized on carbon paper electrode, the dinuclear catalyst enhances up to four fold the heterogeneous CO 2 reduction to CO in water with an improved selectivity and stability compared to the mononuclear analogue. Interestingly, quasi‐identical catalytic performances are obtained when one of the two iron centers was replaced by a redox inactive Zn metal, questioning the cooperative action of the two metals. Snapshots of X‐ray structures indicate that the two metalloporphyrin units tethered by a urea group is a good compromise between rigidity and flexibility to accommodate CO 2 capture, activation, and reduction

Sonocrystallization Induced Thermally Activated Delayed Fluorescence via Distortion of Molecular Geometry

In this work we present three donor-acceptor thermally activated delayed fluorescence (TADF) molecules comprising a 2,3,5,6-tetrafluorobenzonitrile acceptor with various electron donor units: phenoxazine (Phx-BzN), phenothiazine (Pht-BzN), and carbazole (Cz-BzN). These molecules have been studied using steady-state and time-resolved photophysical techniques in solution, film and in crystal state. While Cz-BzN displays TADF in solution and PMMA films, Phx-BzN and Pht-BzN are non-emissive in solution and somewhat emissive in polymer films. More interestingly, while Pht-BzN remains virtually non-emissive in all studied solvents, it exhibits strong photoluminescence and TADF in crystal state, attributed to Crystallization Induced Emission (CIE). We demonstrate through computational studies that the CIE properties arise due to intermolecular interactions in the crystal structure that result in locking the ground state molecular geometry and blocking relaxation in the excited state. As a result, the oscillator strength in the crystal form is enhanced leading to a highly luminescent behaviour, while in solution it equals nearly zero due to the molecule adopting a perfectly orthogonal D-A orientation in the excited state

Acid-catalyzed reaction of 2-hydroxycyclobutanone with benzylic alcohols

The acid-promoted syntheses of 2-(benzyloxy)cyclobutanones and bis(benzyloxy)dioxatricyclo decanes were achieved starting from 2-hydroxycyclobutanone and variously functionalized benzyl alcohols. The reaction sequences afforded the desired products in good to high yields and in a solvent-dependent chemoselective fashion

Synthesis of 2,2-bis(pyridin-2-yl amino)cyclobutanols and their conversion into 5-(pyridin-2-ylamino)dihydrofuran-2(3: H)-ones

A two-step protocol is presented for the preparation of 5-(pyridin-2-ylamino)dihydrofuran-2(3H)-ones from 2-hydroxycyclobutanone and some 2-aminopyridines via a catalyst-free synthesis of 2,2-bis(pyridin-2-ylamino)cyclobutanols followed by Dess-Martin periodinane mediated ring expansion

Acid-catalyzed synthesis of functionalized arylthio cyclopropane carbaldehydes and ketones

A general strategy for the synthesis of arylthio cyclopropyl carbaldehydes and ketones via a Brønsted acid catalyzed arylthiol addition/ring contraction reaction sequence has been exploited. The procedure led to a wide panel of cyclopropyl carbaldehydes in generally high yields and with broad substrate scope. Mechanistic aspects and synthetic applications of this procedure were investigated