Correction: Perylene-derivative singlet exciton fission in water solution.

[This corrects the article DOI: 10.1039/D4SC04732J.].

Perylene-derivative singlet exciton fission in water solution.

We provide direct evidence of singlet fission occurring with water-soluble compounds. We show that perylene-3,4,9,10-tetracarboxylate forms dynamic dimers in aqueous solution, with lifetimes long enough to allow intermolecular processes such as singlet fission. As these are transient dimers rather than stable aggregates, they retain a significant degree of disorder.

Enhanced Light Trapping in GaAs/TiO-Based Photocathodes for Hydrogen Production.

Photoelectrochemical cells (PEC) are appealing devices for the production of renewable energy carriers. In this context, III-V semiconductors such as GaAs are very promising materials due to their tunable band gaps, which can be appropriately adjusted for sunlight harvesting. Because of the high cost of these semiconductors, the nanostructuring of the photoactive layer can help to improve the device efficiency as well as drastically reduce the amount of material needed.

A covalent cobalt diimine-dioxime - fullerene assembly for photoelectrochemical hydrogen production from near-neutral aqueous media.

The covalent assembly between a cobalt diimine-dioxime complex and a fullerenic moiety results in enhanced catalytic properties in terms of overpotential requirement for H evolution. The interaction between the fullerene moiety and PCBM heterojunction further allows for the easy integration of the cobalt diimine-dioxime - fullerene catalyst with a poly-3-hexylthiophene (P3HT):[6,6]-phenyl-C-butyric acid methyl ester (PCBM) bulk heterojunction, yielding hybrid photoelectrodes for H evolution from near-neutral aqueous solutions.

Phosphine Oxide Porous Organic Polymers Incorporating Cobalt(II) Ions: Synthesis, Characterization, and Investigation of H Production.

Suitably functionalized porous matrices represent versatile platforms to support well-dispersed catalytic centers. In the present study, porous organic polymers (POPs) containing phosphine oxide groups were fabricated to bind transition metals and to be investigated for potential electrocatalytic applications. Cross-linking of mono- and di-phosphine monomers with multiple phenyl substituents was subject to the Friedel-Crafts (F-C) reaction and the oxidation process, which generated phosphine oxide porous polymers with pore capacity up to 0.

Electrocatalytic reduction of protons to dihydrogen by the cobalt tetraazamacrocyclic complex [Co(NH)Cl]: mechanism and benchmarking of performances.

The cobalt tetraazamacrocyclic [Co(NH)Cl] complex is becoming a popular and versatile catalyst for the electrocatalytic evolution of hydrogen, because of its stability and superior activity in aqueous conditions. We present here a benchmarking of its performances based on the thorough analysis of cyclic voltammograms recorded under various catalytic regimes in non-aqueous conditions allowing control of the proton concentration. This allowed a detailed mechanism to be proposed with quantitative determination of the rate-constants for the various protonation steps, as well as identification of the amine function of the tetraazamacrocyclic ligand to act as a proton relay during H evolution.

Revisiting amorphous molybdenum sulfide's activity for the electro-driven reduction of dinitrogen and N-containing substrates.

Ammonia (NH) is a major feedstock of the chemical industry. The imperious need to decarbonize its production has stimulated a quest for efficient catalysts able to drive the direct electro-reduction of dinitrogen (N) into NH. A large number of materials have now been proposed for this reaction, including bioinspired molybdenum sulfide derivatives.

Design of porphyrin-based ligands for the assembly of [d-block metal : calcium] bimetallic centers.

The association of different metals in stable, well-defined molecular assemblies remains a great challenge of supramolecular chemistry. In such constructs, the emergence of synergism, or cooperative effects between the different metal centers is particularly intriguing. These effects can lead to uncommon reactivity or remarkable physico-chemical properties that are not otherwise achievable.

Controlling the rectification properties of molecular junctions through molecule-electrode coupling.

The development of molecular components functioning as switches, rectifiers or amplifiers is a great challenge in molecular electronics. A desirable property of such components is functional robustness, meaning that the intrinsic functionality of components must be preserved regardless of the strategy used to integrate them into the final assemblies. Here, this issue is investigated for molecular diodes based on N-phenylbenzamide (NPBA) backbones.

Nanoscale Study of Polymer Dynamics.

The thermal motion of polymer chains in a crowded environment is anisotropic and highly confined. Whereas theoretical and experimental progress has been made, typically only indirect evidence of polymer dynamics is obtained either from scattering or mechanical response. Toward a complete understanding of the complicated polymer dynamics in crowded media such as biological cells, it is of great importance to unravel the role of heterogeneity and molecular individualism.

Computational Design of Intrinsic Molecular Rectifiers Based on Asymmetric Functionalization of N-Phenylbenzamide.

We report a systematic computational search of molecular frameworks for intrinsic rectification of electron transport. The screening of molecular rectifiers includes 52 molecules and conformers spanning over 9 series of structural motifs. N-Phenylbenzamide is found to be a promising framework with both suitable conductance and rectification properties.

Preparation of Halogenated Fluorescent Diaminophenazine Building Blocks.

A short, convenient, and scalable protocol for the one-pot synthesis of a series of fluorescent 7,8-dihalo-2,3-diaminophenazines is introduced. The synthetic route is based on the oxidative condensation of 4,5-dihalo-1,2-diaminobenzenes in aqueous conditions. The resulting diaminophenazines could be attractive intermediates for the preparation of polyfunctional phenazines and extended polyheteroacenes.

Trapping Nanostructures on Surfaces through Weak Interactions.

The assembly of imidazole-functionalized phenanthroline-strapped zinc porphyrins (ZnPorphen) with alkyl or polyethylene glycol (PEG) side chains was studied in solution and by AFM after casting on highly oriented pyrolytic graphite (HOPG) or mica. The nature of the solvent and its evaporation time influenced the morphology of the objects observed. On HOPG, short rods of about 100 nm were observed after fast evaporation of solutions of the alkyl derivatives in CHCl3 , THF, or pyridine, whereas islands of aligned rows of longer wires were obtained from methylcyclohexane (MCH).

Towards multielectron photocatalysis: a porphyrin array for lateral hole transfer and capture on a metal oxide surface.

Current molecular water-oxidation photoelectrocatalytic cells have substantial kinetic limitations under normal solar photon flux where electron-hole recombination processes may outcompete charge buildup on the catalytic centers. One method of overcoming these limitations is to design a system where multiple light-harvesting dyes work cooperatively with a single catalyst. We report a porphyrin monomer/dyad array for analysis of lateral hole transfer on a SnO2 surface consisting of a free-base porphyrin that functions to absorb light and initiate charge injection into the conduction band of SnO2, which leaves a positive charge on the organic moiety, and a free-base porphyrin/Zn-porphyrin dyad molecule that functions as a thermodynamic trap for the photoinduced holes.

Beta sheets with a twist: the conformation of helical polyisocyanopeptides determined by using vibrational circular dichroism.

Detailed information on the architecture of polyisocyanopeptides based on vibrational circular dichroism (VCD) spectroscopy in combination with DFT calculations is presented. It is demonstrated that the screw sense of the helical polyisocyanides can be determined directly from the C=N-stretch vibrational region of the VCD spectrum. Analysis of the VCD signals associated with the amide I and amide II modes provides detailed information on the peptide side-chain arrangement in the polymer and indicates the presence of a helical β-sheet architecture, in which the dihedral angles are slightly different to those of natural β-sheet helices.

Responsive biomimetic networks from polyisocyanopeptide hydrogels.

Mechanical responsiveness is essential to all biological systems down to the level of tissues and cells. The intra- and extracellular mechanics of such systems are governed by a series of proteins, such as microtubules, actin, intermediate filaments and collagen. As a general design motif, these proteins self-assemble into helical structures and superstructures that differ in diameter and persistence length to cover the full mechanical spectrum.

Highly linear self-assembled porphyrin wires.

An efficient noncovalent assembly process involving high geometrical control was applied to a linear bis(imidazolyl zinc porphyrin) 7Zn, bearing C(18) substitutents, to generate linear multiporphyrin wires. The association process is based on imidazole recognition within the cavity of the phenanthroline-strapped zinc porphyrin. In chlorinated solvents, discrete soluble oligomers were obtained after (7Zn)(n) was end-capped with a terminal single imidazolyl zinc porphyrin derivative 4Zn.

Sequential energy and electron transfer in polyisocyanopeptide-based multichromophoric arrays.

We report on the synthesis and detailed photo-physical investigation of four model chromophore side chain polyisocyanopeptides: two homopolymers of platinum-porphyrin functionalized polyisocyanopeptides (Pt-porphyrin-PIC) and perylene-bis(dicarboximide) functionalized polyisocyanopeptides (PDI-PIC), and two statistical copolymers with different ratios of Pt-porphyrin and PDI molecules attached to a rigid, helical polyisocyanopeptide backbone. (1)H NMR and circular dichroism measurements confirm that our model compounds retain a chiral architecture in the presence of the chromophores. The combination of Pt-porphyrin and PDI chromophores allows charge- and/or energy transfer to happen.

Cysteine-containing polyisocyanides as versatile nanoplatforms for chromophoric and bioscaffolding.

The straightforward syntheses of polyisocyanides containing the alanine-cysteine motif in their side chains have been achieved. Detailed characterization of the polymers revealed a well-defined and highly stable helical conformation of the polyimine backbone responsible for the formation of rodlike structures of over one hundred nanometers. The 4(1) helix is further stabilized by beta-sheet-like interactions between the peptide arms.

Vibrational self-trapping in beta-sheet structures observed with femtosecond nonlinear infrared spectroscopy.

Self-trapping of NH-stretch vibrational excitations in synthetic beta-sheet helices is observed using femtosecond infrared pump-probe spectroscopy. In a dialanine-based beta-sheet helix, the transient-absorption change upon exciting the NH-stretch mode exhibits a negative absorption change at the fundamental frequency and two positive peaks at lower frequencies. These two induced-absorption peaks are characteristic for a state in which the vibrational excitation is self-trapped on essentially a single NH-group in the hydrogen-bonded NH.

Self-trapped vibrational states in synthetic beta-sheet helices.

Femtosecond vibrational pump-probe spectroscopy on beta-helical polyisocyanopeptides reveals vibrational self-trapping in the well-defined hydrogen-bonded side groups that is absent when non-hydrogen bonded monomers are mixed in.

Molecular tools for the self-assembly of bisporphyrin photodyads: a comprehensive physicochemical and photophysical study.

Accessible and hindered phenanthroline-strapped Zn(II) porphyrin receptors exhibited suitable topography tailored to strongly and selectively bind N(1)-unsubstituted imidazoles and imidazoles appended to free-base porphyrins. Distal binding was clearly driven by the formation of strong bifurcated hydrogen bonds with the phenanthroline unit of the receptors. An extensive physicochemical study emphasized the influence of bulkiness of the substrate and of the porphyrin receptor on the binding and self-assembly mechanism.

Surface-tuned assembly of porphyrin coordination oligomers.

Two self-complementary phenanthroline-strapped porphyrins bearing imidazole arms and C 12 or C 18 alkyl chains were synthesized, and their surface self-assembly was investigated by atomic force microscopy (AFM) on mica and highly ordered pyrrolitic graphite (HOPG). Upon zinc(II) complexation, stable porphyrin dimers formed, as confirmed by DOSY (1)H NMR and UV-visible spectroscopy. In solution, the dimers formed J-aggregates.

Photodynamics of excitation energy transfer in self-assembled dyads. Evidence for back transfer.

Three self-assembled photonic dyads comprising a zinc porphyrin donor and a free base acceptor have been studied by time-resolved fluorescence spectroscopy. The driving force of the assembly is the site selective binding of an imidazole connected to a free base porphyrin. Three spacers have been incorporated between the imidazole connector and the free base porphyrin, providing three different distances separating the donor and the acceptor.

Design and synthesis of a self-assembled photochemical dyad based on selective imidazole recognition.

The unique recognition properties of phenanthroline-strapped zinc porphyrin 1, which displays extremely high affinity for N-unsubstituted imidazoles, has been used as the driving force for the assembly of a photochemical dyad involving a zinc(II) porphyrin as energy donor and a free base porphyrin as energy acceptor. The synthesis of the imidazole-substituted porphyrin is described together with the assembly of the dyad. (1)H NMR titrations confirm the formation of a 1/1 complex between 1 and 6, as well as insertion of the imidazole of the acceptor within the phenanthroline strap of the donor.