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The oxygen in Earth’s atmosphere is there primarily because of water oxidation performed by photosynthetic organisms using solar light and one specialized protein complex, photosystem II (PSII). High-resolution imaging of the PSII ‘core’ complex shows the ideal co-localization of multi-chromophore light-harvesting antennas with the functional reaction centre. Man-made systems are still far from replicating the complexity of PSII, as the majority of PSII mimetics have been limited to photocatalytic dyads based on a 1:1 ratio of a light absorber, generally a Ru–polypyridine complex, with a water oxidation catalyst. Here we report the self-assembly of multi-perylene-bisimide chromophores (PBI) shaped to function by interaction with a polyoxometalate water-oxidation catalyst (Ru4POM). The resulting [PBI]5Ru4POM complex shows a robust amphiphilic structure and dynamic aggregation into large two-dimensional paracrystalline domains, a redshifted light-harvesting efficiency of >40% and favourable exciton accumulation, with a peak quantum efficiency using ‘green’ photons (λ > 500 nm). The modularity of the building blocks and the simplicity of the non-covalent chemistry offer opportunities for innovation in artificial photosynthesis.

The achiral, nitroxyl-contg. a-amino acid TOAC (TOAC = 2,2,6,6- tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid), in combination with the chiral a-amino acid Ca-Me valine [(aMe)Val], was used to prep. short peptides (from di- to hexa-) that induced the enantioselective oxidn. of racemic 1-phenylethanol to acetophenone. The best catalyst was an Na-acylated dipeptide alkylamide with the -TOAC-(aMe)Val- sequence folded in a stable, intramolecularly hydrogen-bonded b-turn conformation with large, lipophilic (hydrophobic) N- and C-terminal blocking groups. We rationalized our findings by proposing models for the diastereomeric intermediates between (R)-[and (S)]-1-phenylethanol and the catalyst Fmoc- TOAC-L-(aMe)Val-NHiPr, based on the X-ray diffraction structure of the latter.

La fotosintesi artificiale, ovvero la conversione diretta di energia solare in energia chimica attraverso la sintesi fotoindotta di specie chimiche ad alta energia, quali idrogeno e altri combustibili, a partire da specie a bassa energia come acqua e anidride carbonica, un processo ispirato alla fotosintesi naturale, è stato per lungo tempo un sogno inseguito dalla comunità scientifica internazionale. Gli sviluppi degli ultimi anni permettono adesso di affrontare il problema con buone speranze di successo. L’articolo presenta una breve panoramica delle problematiche relative alla fotosintesi artificiale, delle strutture e dei progetti di ricerca nel settore attualmente presenti nei vari Paesi, con particolare attenzione per gli studi che vengono portati avanti dai ricercatori del SOLAR-CHEM, centro interuniversitario italiano per la conversione chimica dell’energia solare.

Ionic Liquid Crystals Based on Viologen and Viologen Dimers

Chitosan and its derivates continue to attract considerable research interest as effective drug carriers with good biocompatibility and high cellular uptake rates. We used these versatile features to tap the considerable biomedical potential of polyoxometalates (POMs) through their encapsulation into a carboxymethyl chitosan (CMC) matrix. The nanocapsules were prepared by ionic gelification with Ca(2+); their size distribution ranges from 60 to 150 nm. Because [Co(4)(H(2)O)(2)(PW(9)O(34))(2)](10-) is well known for its manifold properties, such as antiviral activity, it was selected as a model POM. The resulting composites were characterised with a wide range of analytical methods, which pointed to quantitative encapsulation of intact POMs within the CMC matrix. We studied the biocompatibility of the POM/CMC nanocomposites on HeLa cells through MTT and proliferation assays. Even after prolonged incubation times at high concentrations, the composites did not display cytotoxicity, thereby drastically reducing the side effects of the pristine POMs. This opens up new avenues for designing novel inorganic drug prototypes from bioactive POMs.

The assisted catalysis in heterogeneous phase represents a friendly environmental tool for chemical transformations turned to the strategy of advanced process intensification. The idea to disperse a catalyst into a polymer matrix offers the attractive opportunity to overcome drawbacks concerned with the recovery, reuse, disposal and life of the compound to overcome with catalytic activity. Molecular conversion and separation steps can be further coupled in a unique selective catalytic process, resulting in high efficiency/cost ratio.

ESI-MS analysis provides a straightforward tool for the solution characterization of highly charged mono-lacunary Keggin-type polyoxotungstates Ą-[XW11O39]p- (X = Si, P; p = 8, 7). Double and triple charged quasi-molecular ion peaks were identified on the bases of both the theoretical simulation of the isotopic cluster distributions and the fragmentation modes observed with MS/MS technique. This approach allows to characterize the inorganic polyanions transferred into the gas-phase with associated alkali metal cations (Li+, Na+).

Oxidation of p-XC6H4SOMe (X = NC, F3C) by (alkylperoxo){tris[(2R)-2-hydroxy-2-phenylethyl]amine}titanium (2b ) has been shown to follow Michaelis-Menten kinetics demonstrating the occurrence of an intramolecular nucleophilic oxygen transfer to the TiIV-coordinated sulfoxide. The reaction of the titanium(IV) precursors 1 with sulfoxides has been studied by ESI-MS techniques together with ab initio calculations.

Mapping an uncharted territory: The good correlation between experimental and calculated 183W NMR chemical shifts of polyoxotungstates may allow the prediction and assignment of the spectra of unstable or unknown species, and also allow the counterion effect to be addressed.

Organoruthenium polyoxometalates with general formula [{Ru(C6Me6)}3M5O18], M=Mo, W, serve as catalyst precursors, together with 2,6-dichloropyridine N-oxide, to effect the hydroxylation of adamantane with conversion up to 94%, and C3-H/C2-H selectivity >100. Under analogous conditions, hydroxylation of cis-decalin occurred with complete stereoretention. Control experiments and kinetic evidence suggest the in-situ formation of a high valent Ru-oxo species as the competent oxidant.

The nuclear shielding of 99Ru in several complexes has been investigated computationally by DFT methods with effective core potential and all- electron basis sets. Shieldings calculated with ECP bases correlate very satisfactorily with available experimental data, even though they are ca. one order of magnitude lower than the experimental values. The influence of molecular geometry (semiempirical vs. DFT) on the nuclear shielding is also examined and discussed, particularly in the case of species containing Ru S bonds (RuCl2(DMSO)4 and PW11O39Ru(DMSO)5). It is shown that such calculations can greatly help signal assignment in 99Ru NMR spectra of mono- and polynuclear complexes.

The 2:1 inclusion complex between (2,3,6-tri-O-methyl)-b-cyclodextrin (TMbCD) and 5,10,15,20-tetrakis(4-sulfonatophenyl)-porphyrin (TPPS4 ) behaves as a supramolecular sensitizer in water providing photooxygenation with turnover numbers up to 30 000 with a very minor sensitizer bleaching (