Light: A Very Peculiar Reactant and Product

See the light of day: Light is the fastest way of transferring energy and information through space, and in chemistry it can perform the dual role of reactant and product. Sunlight, a really unique reactant, represents our ultimate energy source. Chemists are engaged in designing systems for the conversion of light into electrical or chemical energy and vice versa to create a more sustainable way of life

Divergent Terpyridine-Based Coordination for the Construction of Photoactive Supramolecular Structures

Exploring new materials to manipulate luminescent radiation and investigate the interaction of light and matter is one of the most compelling prospects of our century. Supramolecular chemistry has unraveled the opportunity to synergistically combine the chemical and optoelectronic properties of the most diverse classes of compounds. Among these, terpyridines have acted as pivotal ligand units that enable self-assembly of multicomponent chromophoric systems. In this review we therefore elucidate the metal-coordinating ability of these materials, that promote a plethora of aggregation-induced phenomena. In particular, fluorescence tuning, reversible stimuli-responsive phosphorescence enhancement and low-dimensional complexation have been demonstrated for carbon and sulfur based terpyridine oligomeric structures. Common thread of such processes is the versatile application of light as a trigger for spectroscopic investigation and output for superior optical, medical and sensing devices

RuO2 Nanostructure as an Efficient and Versatile Catalyst for H2 Photosynthesis

Photocatalytic H-2 generation holds promisein the greenproduction of alternative fuels and valuable chemicals. Seeking alternative,cost-effective, stable, and possibly reusable catalysts representsa timeless challenge for scientists working in the field. Herein,commercial RuO2 nanostructures were found to be a robust,versatile, and competitive catalyst in H-2 photoproductionin several conditions. We employed it in a classic three-componentsystem and compared its activities with those of the widely used platinumnanoparticle catalyst. We observed a hydrogen evolution rate of 0.137mol h(-1) g(-1) and an apparent quantumefficiency (AQE) of 6.8% in water using EDTA as an electron donor.Moreover, the favorable employment of l-cysteine as the electronsource opens possibilities precluded to other noble metal catalyst.The versatility of the system has also been demonstrated in organicmedia with impressive H-2 production in acetonitrile. Therobustness has been proved by the recovery of the catalyst by centrifugationand reusage alternatively in different media

The rational search for selective anticancer derivatives of the peptide Trichogin GA IV: a multi-technique biophysical approach

Peptaibols are peculiar peptides produced by fungi as weapons against other microorganisms. Previous studies showed that peptaibols are promising peptide-based drugs because they act against cell membranes rather than a specific target, thus lowering the possibility of the onset of multi-drug resistance, and they possess non-coded alpha-amino acid residues that confer proteolytic resistance. Trichogin GA IV (TG) is a short peptaibol displaying antimicrobial and cytotoxic activity. In the present work, we studied thirteen TG analogues, adopting a multidisciplinary approach. We showed that the cytotoxicity is tuneable by single amino-acids substitutions. Many analogues maintain the same level of non-selective cytotoxicity of TG and three analogues are completely non-toxic. Two promising lead compounds, characterized by the introduction of a positively charged unnatural amino-acid in the hydrophobic face of the helix, selectively kill T67 cancer cells without affecting healthy cells. To explain the determinants of the cytotoxicity, we investigated the structural parameters of the peptides, their cell-binding properties, cell localization, and dynamics in the membrane, as well as the cell membrane composition. We show that, while cytotoxicity is governed by the fine balance between the amphipathicity and hydrophobicity, the selectivity depends also on the expression of negatively charged phospholipids on the cell surface

Benzothiazolium-functionalized NU-1000 : a versatile material for carbon dioxide adsorption and cyanide luminescence sensing

The benzothiazolium-decorated NU-1000-BzTz MOF is a versatile material for carbon dioxide storage and cyanide luminescence sensing in aqueous solutions

A high-sensitivity long-lifetime phosphorescent RIE additive to probe free volume-related phenomena in polymers

The photophysical behaviour of phosphorescent rigidification-induced emission (RIE) dyes is highly affected by their micro- and nanoenvironment. The lifetime measure of RIE dyes dispersed in polymers represents an effective approach to gain valuable information on polymer free volume and thus develop materials potentially able to self-monitor physical ageing and mechanical stresses

Giant Shape-Persistent Tetrahedral Porphyrin System: Light-Induced Charge Separation

Tetraphenylmethane appended with four pyridylpyridinium units works as a scaffold to self-assemble four ruthenium porphyrins in a tetrahedral shape-persistent giant architecture. The resulting supramolecular structure has been characterised in the solid state by X-ray single crystal analysis and in solution by various techniques. Multinuclear NMR spectroscopy confirms the 1 : 4 stoichiometry with the formation of a highly symmetric structure. The self-assembly process can be monitored by changes of the redox potentials, as well as by modifications in the visible absorption spectrum of the ruthenium porphyrin and by a complete quenching of both the bright fluorescence of the tetracationic scaffold and the weak phosphorescence of the ruthenium porphyrin. An ultrafast photoinduced electron transfer is responsible for this quenching process. The lifetime of the resulting charge separated state (800 ps) is about four times longer in the giant supramolecular structure compared to the model 1 : 1 complex formed by the ruthenium porphyrin and a single pyridylpyridinium unit. Electron delocalization over the tetrameric pyridinium structure is likely to be responsible for this effect

Poly(3-hexylthiophene) Nanoparticles Containing Thiophene-S,S-dioxide: Tuning of Dimensions, Optical and Redox Properties, and Charge Separation under Illumination

We describe the preparation of poly(3-hexylthiophene-S,S-dioxide) nanoparticles using Rozen's reagent, HOF·CH3CN, either on poly(3-hexylthiophene) (P3HT) or on preformed P3HT nanoparticles (P3HT-NPs). In the latter case, core-shell nanoparticles (P3HT@PTDO-NPs) are formed, as confirmed by X-ray photoelectron spectroscopy measurements, indicating the presence of oxygen on the outer shell. The different preparation modalities lead to a fine-tuning of the chemical-physical properties of the nanoparticles. We show that absorption and photoluminescence features, electrochemical properties, size, and stability of colloidal solutions can be finely modulated by controlling the amount of oxygen present. Atomic force microscopy measurements on the nanoparticles obtained by a nanoprecipitation method from preoxidized P3HT (PTDO-NPs) display spherical morphology and dimensions down to 5 nm. Finally, Kelvin probe measurements show that the coexistence of p- and n-type charge carriers in all types of oxygenated nanoparticles makes them capable of generating and separating charge under illumination. Furthermore, in core-shell nanoparticles, the nanosegregation of the two materials, in different regions of the nanoparticles, allows a more efficient charge separation

Tailoring colors by O-annulation of polycyclic aromatic hydrocarbons

The synthesis of O-doped polyaromatic hydrocarbons, in which two polycyclic aromatic hydrocarbon subunits are bridged through one or two O atoms, has been achieved. This includes high-yielding ring-closure key steps that, depending on the reaction conditions, yield the formation of either furanyl or pyranopyranyl linkages through intramolecular C-O bond formation. Comprehensive photophysical measurements in solution showed that these molecules feature exceptionally high emission yields and tunable absorption properties throughout the UV-vis spectral region. Electrochemical investigations showed that in all cases the O-annulation increases the electron donor capabilities by raising the HOMO energy level with the LUMO energy level being less affected. Moreover, third-order NLO measurements of solutions or thin films containing the dyes displayed very good second hyperpolarizibility values. Importantly, PMMA films containing the pyranopyranyl derivatives displayed weak linear absorption and NLO absorption compared to the nonlinearity and NLO refraction, respectively, revealing to be exceptional organic materials for photonic devices