OFF/ON switching of circularly polarized luminescence by oxophilic interaction of homochiral sulfoxide-containing o-OPEs with metal cations

CPL switches with high g_lum and Φ are described.

Aggregation-induced emission of [3]cumulenes functionalized with heptagon-containing polyphenylenes

[3]Cumulenes became luminescent upon aggregation at room temperature by protection with heptagon-containing polyphenylenes as endgroups.

Versatile synthesis and enlargement of functionalized distorted heptagon-containing nanographenes

Highly distorted polycyclic aromatic hydrocarbons (PAHs) are predicted to be attractive goals in nanoscience owing to the new properties they can exhibit. We have shown that a variety of functionalized distorted heptagon-containing nanographenes can be easily prepared from simple building blocks by a sequence of Co-catalyzed cyclotrimerization and cyclodehydrogenation reactions. The versatility of this strategy allows easy subsequent enlargement of these nanostructures by Ni-catalyzed cross-coupling and final cyclodehydrogenation reactions. Soluble extended distorted nanographenes 1 and 2 containing heptagon and an edge-shared pentagon-heptagon combination have been synthesized. High distortion of the polycyclic backbone of 2 caused by non-hexagonal rings and a helicene moiety was confirmed by X-ray crystallography. Experimental data reveal promising optical and electronic properties for distorted PAHs with long fluorescence lifetimes (up to 14.5 ns) and low band gaps (down to 2.27 eV). This straightforward and versatile synthetic strategy, the observed long fluorescence lifetimes and the small optical and electrochemical band gaps for the presented compounds may promote the future implementation of distorted graphene molecules in electronic devices.

Stapled helical o-OPE foldamers as new circularly polarized luminescence emitters based on carbophilic interactions with Ag(i)-sensitivity

ortho-Oligo(phenylene)ethynylenes (o-OPEs) stapled with enantiopure 2,3-dihydroxybutane diethers have highly intense circular dichroism (CD) spectra and excellent circular polarized luminescence (CPL) responses (glum values up to 1.1 × 10-2), which are consistent with homochiral helically folded structures. In the presence of Ag(i), a change in the CPL emission is observed, representing the first example of CPL active small organic molecular emitters, which can be modulated by carbophilic interactions in a reversible manner.

Synthesis of substituted γ- and δ-lactams based on titanocene(iii)-catalysed radical cyclisations of trichloroacetamides

Straightforward synthesis of dehalogenated γ- and δ-lactams based on a Cp₂TiCl-catalysed radical cyclisation of trichloroacetamides under mild conditions.

Two-dimensional carbon-based conductive materials with dynamically controlled asymmetric Dirac cones

The design of two dimensional graphene-type materials with an anisotropic electron flow direction in the X- and Y-axes opens the door for the development of novel electronic materials with multiple functions in nanoelectronics. In the present work, we have studied the electronic transport properties of a new family of 2D graphene-graphyne hybrids presenting conformationally free phenylethylene subunits. This system ensures two different conductive pathways that are perpendicular to each other: an acene nanoribbon subunit, in the X-axis, with graphene-type conduction, and a free to rotate phenylethylene subunit, in the Y-axis, in which the magnitude of the conduction depends dynamically on the corresponding torsion angle. Our calculations have confirmed that this system presents two different conduction pathways, which are related to the presence of asymmetric Dirac-type cones. Moreover, the Dirac cones can be dynamically modified in the presence of an external gate electrode, which is unprecedented in the literature.

Influence of the chirality of short peptide supramolecular hydrogels in protein crystallogenesis

For the first time the influence of the chirality of the gel fibers in protein crystallogenesis has been studied. Enantiomeric hydrogels 1 and 2 were tested with model proteins lysozyme and glucose isomerase and a formamidase extracted from B. cereus. Crystallization behaviour and crystal quality of these proteins in both hydrogels are presented and compared.

Ti(III)-catalyzed cyclizations of ketoepoxypolyprenes: control over the number of rings and unexpected stereoselectivities

We describe a new strategy to control the number of cyclization steps in bioinspired radical (poly)cyclizations involving epoxypolyenes containing keto units positioned along the polyene chain. This approach provides an unprecedentedly straightforward access to natural terpenoids with pendant unsaturated side chains. Additionally, in the case of bi- and tricyclizations, decalins with cis stereochemistry have been obtained as a consequence of the presence of the ketone. The preferential formation of cis-fused adducts was rationalized using DFT calculations. This result is completely unprecedented in biomimetic cyclizations and permits the access to natural terpenoids with this stereochemistry, as well as to non-natural analogues.

Cp2TiCl-catalyzed highly stereoselective intramolecular epoxide allylation using allyl carbonates

Diastereoselective synthesis of vinyl substituted carbo- and heterocyclic products is achieved by intramolecular radical cyclization of epoxy allyl carbonates.

Novel ortho-OPE metallofoldamers: binding-induced folding promoted by nucleating Ag(i)–alkyne interactions

Ag(i)–alkyne interactions induce the folding of o-OPE foldamers, yielding a new class of metallofoldamers.

Highly regioselective and chemoselective titanocene mediated Barbier-type allylation reactions

New titanocene(iii) has been developed for chemoselective α-regioselective Barbier-type reactions, constituting the first titanocene(iii) able to tolerate epoxides and readily reduced carbonyl compounds.

Recent applications of Cp2TiCl in natural product synthesis

Titanocene(iii)-based approaches have been demonstrated to be useful in the straightforward syntheses of many natural products from readily available starting materials.

The role of water-based hydrogen atom wires in long-range electron-transfer reactions in aqueous media for the FeII-FeIII self-exchange and related systems

Extended reach: A calculated mechanism for long-range proton-coupled electron transfer (PCET, see picture) through an array of structured water molecules between Fe(III)-Fe(III) complexes accounts for the reaction enthalpy and kinetic isotope effect previously measured for this reaction. This mechanism may be general and occur for other hydroxo-metal complexes.

Influence of the number of anchoring groups on the electronic and mechanical properties of benzene-, anthracene- and pentacene-based molecular devices

One of the central issues of molecular electronics (ME) is the study of the molecule-metal electrode contacts, and their implications for the conductivity, charge-transport mechanism, and mechanical stability. In fact, stochastic on/off switching (blinking) reported in STM experiments is a major problem of single-molecule devices, and challenges the stability and reliability of these systems. Surprisingly, the ambiguous STM results all originate from devices that bind to the metallic electrode through a one-atom connection. In the present work, DFT is employed to study and compare the properties of a set of simple acenes that bind to metallic electrodes with an increasing number of connections, in order to determine whether the increasing numbers of anchoring groups have a direct repercussion on the stability of these systems. The conductivities of the three polycyclic aromatic hydrocarbons are calculated, as well as their transmission spectra and current profiles. The thermal and mechanical stability of these systems is studied by pulling and pushing the metal-molecule connection. The results show that molecules with more than one connection per electrode exhibit greater electrical efficiency and current stability.

Organic-based molecular switches for molecular electronics

In a general sense, molecular electronics (ME) is the branch of nanotechnology which studies the application of molecular building blocks for the fabrication of electronic components. Among the different types of molecules, organic compounds have been revealed as promising candidates for ME, due to the easy access, great structural diversity and suitable electronic and mechanical properties. Thanks to these useful capabilities, organic molecules have been used to emulate electronic devices at the nanoscopic scale. In this feature article, we present the diverse strategies used to develop organic switches towards ME with special attention to non-volatile systems.

Ti/Pd-promoted intramolecular Michael-type addition of allylic carboxylates to activated alkenes

An interesting protocol for the synthesis of different vinyl substituted carbo- and heterocycles based on a new intramolecular Michael-type reaction using allylic carboxylates as pronucleophiles is reported. The success of the catalytic process is based on the excellent cooperation between the late transition metal (palladium) and the radical reagent (titanium).

Mn(0)-mediated chemoselective reduction of aldehydes. Application to the synthesis of α-deuterioalcohols

A mild, simple, safe, chemoselective reduction of different kinds of aldehydes to the corresponding alcohols mediated by the Mn dust/water system is described. In addition to this, the use of D(2)O leads to the synthesis of α-deuterated alcohols and constitutes an efficient, inexpensive alternative for the preparation of these compounds.

Titanocene(III)-promoted Barbier-type crotylation of carbonyl compounds

A mild, highly regio- and stereoselective method for the crotylation of aldehydes and ketones mediated/catalyzed by titanocene(III) is described. Optimized conditions permit the selective generation of γ-adducts in high yields together with high stereoselectivity, with a predominance of anti stereoisomers.

Unexpected Ti(III)/Mn-promoted pinacol coupling of ketones

Titanocene(III) chemistry has emerged in the last decades as an indispensable tool in C-C bond-forming reactions. In this context, pinacol and related reactions allow the stereoselective synthesis of vicinal diols. In this work, we present new applications of these reactions using as starting materials aromatic ketones. Simple and smooth reaction conditions have been developed and have been applied for inter- and intramolecular processes. We also describe that although Cp(2)TiCl is usually used as a monoelectronic reducing agent, it can be also used as an efficient Lewis acid.

Ti-catalyzed reformatsky-type coupling between alpha-halo ketones and aldehydes

We describe the first Ti-catalyzed Reformatsky-type coupling between alpha-halo ketones and aldehydes. The reaction affords beta-hydroxy ketones under mild, neutral conditions compatible with ketones and other electrophiles. The catalytic cycle possibly proceeds via bis(cyclopentadienyl)titanium enolates.

Sodium Tetramethoxyborate: An Efficient Catalyst for Michael Additions of Stabilized Carbon Nucleophiles

Sodium tetramethoxyborate, easily prepared by reaction of inexpensive sodium borohydride with methanol, possesses a suitable combination of a Lewis base and a Lewis acid to catalyze Michael reactions at room temperature under practically neutral conditions. This reaction provides good to excellent yields of Michael addition products from a broad scope of Michael donor and Michael acceptor reagents.