Correlation between Radical and Quartet State Coherence Times in Photogenerated Triplet-Radical Conjugates.

Molecular quartet states, generated by photoexcitation of chromophore-radical conjugates, have been shown to exhibit attractive properties for applications in the field of molecular spintronics. Many of these applications, such as quantum sensing, require a coherent manipulation of the spin system, implying the need to control the quartet state spin coherence properties. By examining the influence of structural and matrix-related factors, we demonstrate a correlation between the coherence decay of the photogenerated quartet state and that of the tethered stable radical, paving the way for a rational design of photogenerated molecular three-spin systems with optimized coherence properties.

Influence of the substitution position on spin communication in photoexcited perylene-nitroxide dyads.

By virtue of the modularity of their structures, their tunable optical and magnetic properties, and versatile applications, photogenerated triplet-radical systems provide an ideal platform for the study of the factors controlling spin communication in molecular frameworks. Typically, these compounds consist of an organic chromophore covalently attached to a stable radical. After formation of the chromophore triplet state by photoexcitation, two spin centres are present in the molecule that will interact.

Shape-Assisted Self-Assembly of Hexa-Substituted Carpyridines into 1D Supramolecular Polymers.

The extent of the influence that molecular curvature plays on the self-assembly of supramolecular polymers remains an open question in the field. We began addressing this fundamental question with the introduction of "carpyridines", which are saddle-shaped monomers that can associate with one another through π-π interactions and in which the rotational and translational movements are restricted. The topography displayed by the monomers led, previously, to the assembly of highly ordered 2D materials even in the absence of strong directional interactions such as hydrogen bonding.

PDI-trityl dyads as photogenerated molecular spin qubit candidates.

Owing to their potential applications in the field of quantum information science, photogenerated organic triplet-radical conjugates have attracted an increasing amount of attention recently. Typically, these compounds are composed of a chromophore appended to a stable radical. After initialisation of the system by photoexcitation, a highly spin-polarised quartet state may be generated, which serves as a molecular spin qubit candidate.

Saddles as rotational locks within shape-assisted self-assembled nanosheets.

Two-dimensional (2D) materials are a key target for many applications in the modern day. Self-assembly is one approach that can bring us closer to this goal, which usually relies upon strong, directional interactions instead of covalent bonds. Control over less directional forces is more challenging and usually does not result in as well-defined materials.

Room Temperature Electron Spin Coherence in Photogenerated Molecular Spin Qubit Candidates.

One of the main challenges in the emerging field of molecular spintronics is the identification of new spin qubit materials for quantum information applications. In this regard, recent work has shown that photoexcited chromophore-radical systems are promising candidates to expand our repertoire of suitable candidate molecules. Here, we investigate a series of three chromophore-radical compounds composed of a perylene diimide (PDI) chromophore and a stable 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) radical by transient electron paramagnetic resonance (EPR) techniques.

Thermodynamics, morphology and molecular structure of molecular compounds in trisamide triarylamine organogels and pseudo-organogels.

In this paper, potentially-gelling binary systems are investigated by DSC, X-ray and Electron microscopy in order to assess their gel status and the role of the Hansen solubility parameter. The low molecular weight organogelator is a Triarylamine Trisamide (TATA) while the solvents consist of a series of halogeno-ethanes and of toluene. Temperature-concentration phase diagrams are mapped out from DSC traces.

Distance dependence of enhanced intersystem crossing in BODIPY-nitroxide dyads.

Photogenerated organic triplet-doublet systems have attracted an increasing amount of attention in recent years due to their versatility and suitability for a range of technological applications in the emerging field of molecular spintronics. Such systems are typically generated by enhanced intersystem crossing (EISC) preceded by photoexcitation of an organic chromophore covalently linked to a stable radical. After formation of the chromophore triplet state by EISC, triplet state and stable radical may interact, whereby the nature of the interaction depends on the exchange interaction between them.

Some Remarkable Rheological and Conducting Properties of Hybrid PVC Thermoreversible Gels/Organogels.

We report on investigations into the rheological properties of organogels prepared from triarylamine trisamide (TATA) and oligo phenylene vinylene (OPVOH) molecules in binary organogel gels and in ternary thermoreversible networks with poly vinyl chloride (PVC). In the case of OPVOH, we show that the modulus of the ternary gel is simply the sum of the modulus of each binary gel, corresponding to the so-called Voigt upper limit. In contrast, TATA/PVC ternary gels generally exceed the Voigt upper limit.

Shape-assisted self-assembly.

Self-assembly and molecular recognition are critical processes both in life and material sciences. They usually depend on strong, directional non-covalent interactions to gain specificity and to make long-range organization possible. Most supramolecular constructs are also at least partially governed by topography, whose role is hard to disentangle.

Light-Driven Molecular Whirligig.

A unidirectional light-driven rotary motor was looped in a figure-of-eight molecule by linking two polymer chains between its stator and rotor parts. By properly tuning the size of these linkers, clockwise rotation of the motor under UV light was shown to create conformationally strained twists between the polymer chains, and in this tensed conformation, the energy stored in the molecular object was sufficient to trigger the reverse rotation of the motor back to its fully relaxed state. The functioning principle of this motorized molecular device appears very similar to that of macroscopic whirligig crafts used by children for fun.

Super-resolution RESOLFT microscopy of lipid bilayers using a fluorophore-switch dyad.

Dyads consisting of a photochromic switch covalently linked to a fluorescent dye allow the emission from the dye to be controlled by reversible photoisomerization of the switch; one form of the switch quenches fluorescence by accepting energy from the dye. Here we investigate the use of dyads of this type for super-resolution imaging of lipid bilayers. Giant unilamellar vesicles stained with the dyads were imaged with about a two-fold resolution-enhancement compared with conventional confocal microscopy.

Supramolecular Polymerization of Triarylamine-Based Macrocycles into Electroactive Nanotubes.

A -symmetric triarylamine-based macrocycle (i.e., hexaaza[1]paracyclophane), decorated with six lateral amide functions, is synthesized by a convergent and modular strategy.

Covalently Trapped Triarylamine-Based Supramolecular Polymers.

C -Symmetric triarylamine trisamides (TATAs), decorated with three norbornene end groups, undergo supramolecular polymerization and further gelation by π-π stacking and hydrogen bonding of their TATA cores. By using subsequent ring-opening metathesis polymerization, these physical gels are permanently crosslinked into chemical gels. Detailed comparisons of the supramolecular stacks in solution, in the physical gel, and in the chemical gel states, are performed by optical spectroscopies, electronic spectroscopies, atomic force microscopy, electronic paramagnetic resonance spectroscopy, X-ray scattering, electronic transport measurements, and rheology.

Correction: Spironaphthoxazine switchable dyes for biological imaging.

[This corrects the article DOI: 10.1039/C8SC00130H.].

Spironaphthoxazine switchable dyes for biological imaging.

Recent developments in super-resolution microscopy have significantly expanded the requirements for switchable dyes, leading to demand for specially designed molecular switches. We report the synthesis and characterization of a spironaphthoxazine photochromic switch (a derivative of palatinate purple) displaying high photoconversion (85-95%) under readily accessible 405 nm light, broad absorption in the visible, and excellent fatigue resistance. The indole substituent on this spironaphthoxazine is twisted out of conjugation with the naphthalene unit, yet it is crucial for activation with visible light.

Single-Acetylene Linked Porphyrin Nanorings.

The synthesis of ethyne-linked porphyrin nanorings has been achieved by template-directed Sonogashira coupling. The cyclic hexamer and octamer are predicted by density functional theory to adopt low symmetry conformations, due to dihedral twists between neighboring porphyrin units, but their symmetries are effectively D and D, respectively, in solution by H NMR. The fluorescence spectra indicate that the singlet excited states of these nanorings are highly delocalized.

Control of Electrons' Spin Eliminates Hydrogen Peroxide Formation During Water Splitting.

The production of hydrogen through water splitting in a photoelectrochemical cell suffers from an overpotential that limits the efficiencies. In addition, hydrogen-peroxide formation is identified as a competing process affecting the oxidative stability of photoelectrodes. We impose spin-selectivity by coating the anode with chiral organic semiconductors from helically aggregated dyes as sensitizers; Zn-porphyrins and triarylamines.

Photoswitchable Spiropyran Dyads for Biological Imaging.

The synthesis of a small-molecule dyad consisting of a far-red-emitting silicon rhodamine dye that is covalently linked to a photochromic spironaphthothiopyran unit, which serves as a photoswitchable quencher, is reported. This system can be switched reversibly between the fluorescent and nonfluorescent states using visible light at wavelengths of 405 and 630 nm, respectively, and it works effectively in aqueous solution. Live-cell imaging demonstrates that this dyad has several desirable features, including excellent membrane permeability, fast and reversible modulation of fluorescence by visible light, and good contrast between the bright and dark states.

Imaging Nanostructures by Single-Molecule Localization Microscopy in Organic Solvents.

The introduction of super-resolution fluorescence microscopy (SRM) opened an unprecedented vista into nanoscopic length scales, unveiling a new degree of complexity in biological systems in aqueous environments. Regrettably, supramolecular chemistry and material science benefited far less from these recent developments. Here we expand the scope of SRM to photoactivated localization microscopy (PALM) imaging of synthetic nanostructures that are highly dynamic in organic solvents.

Anion transport with halogen bonds.

This review covers the application of halogen bonds to transport anions across lipid bilayer membranes. The introduction provides a brief description of biological and synthetic transport systems. Emphasis is on examples that explore interactions beyond the coordination with lone pairs or hydrogen bonds for the recognition of cations and anions, particularly cation-π and anion-π interactions, and on structural motifs that are relevant for transport studies with halogen bonds.

Quantification of nitrate-π interactions and selective transport of nitrate using calix[4]pyrroles with two aromatic walls.

Herein we disclose the results of our investigations regarding the interactions between the biologically relevant nitrate oxoanion and several "two-wall" aryl-extended calix[4]pyrroles. There exists a clear relationship between the electronic nature of the aromatic walls of the calix[4]pyrroles and the stability of the nitrate⊂calix[4]pyrrole complex. This suggests that NO3(-)-π interactions have an important electrostatic component.

Synthetic ion transporters that work with anion-π interactions, halogen bonds, and anion-macrodipole interactions.

The transport of ions and molecules across lipid bilayer membranes connects cells and cellular compartments with their environment. This biological process is central to a host of functions including signal transduction in neurons and the olfactory and gustatory sensing systems, the translocation of biosynthetic intermediates and products, and the uptake of nutrients, drugs, and probes. Biological transport systems are highly regulated and selectively respond to a broad range of physical and chemical stimulation.

Transmembrane halogen-bonding cascades.

Halogen bonds have recently been introduced as ideal to transport anions across lipid bilayer membranes. However, activities obtained with small transporters were not impressive, and cyclic arrays of strong halogen-bond donors above a calix[4]arene scaffold gave even weaker activities. Here, we report that their linear alignment for anion hopping along transmembrane rigid-rod scaffolds gives excellent activities with an unprecedented cooperativity coefficient m = 3.