Spectroscopy and quantum chemical modeling reveal a predominant contribution of excitonic interactions to the bathochromic shift in alpha-crustacyanin, the blue carotenoprotein in the carapace of the lobster Homarus gammarus

To resolve the molecular basis of the coloration mechanism of alpha-crustacyanin, we used (13)C-labeled astaxanthins as chromophores for solid-state (13)C NMR and resonance Raman spectroscopy of [6,6',7,7']-(13)C(4) alpha-crustacyanin and [8,8',9,9',10,10',11,11',20,20']-(13)C(10) alpha-crustacyanin. We complement the experimental data with time-dependent density functional theory calculations on several models based on the structural information available for beta-crustacyanin. The data rule out major changes and strong polarization effects in the ground-state electron density of astaxanthin upon binding to the protein. Conformational changes in the chromophore and hydrogen-bond interactions between the astaxanthin and the protein can account only for about one-third of the total bathochromic shift in alpha-crustacyanin. The exciton coupling due to the proximity of two astaxanthin chromophores is found to be large, suggesting that aggregation effects in the protein represent the primary source of the color change.     

Progress,highlights and perspectives on NiO in perovskite photovoltaics

The power conversion efficiency (PCE) of NiO based perovskite solar cells has recently hit a record 22.1% with a hybrid organic–inorganic perovskite composition and a PCE above 15% in a fully inorganic configuration was achieved. Moreover, NiO processing is a mature technology, with different industrially attractive processes demonstrated in the last few years. These considerations, along with the excellent stabilities reported, clearly point towards NiO as the most efficient inorganic hole selective layer for lead halide perovskite photovoltaics, which is the topic of this review. NiO optoelectronics is discussed by analysing the different doping mechanisms, with a focus on the case of alkaline and transition metal cation dopants. Doping allows tuning the conductivity and the energy levels of NiO, improving the overall performance and adapting the material to a variety of perovskite compositions. Furthermore, we summarise the main investigations on the NiO/perovskite interface stability. In fact, the surface of NiO is commonly oxidised and reactive with perovskite, also under the effect of light, thermal and electrical stress. Interface engineering strategies should be considered aiming at long term stability and the highest efficiency. Finally, we present the main achievements in flexible, fully printed and lead-free perovskite photovoltaics which employ NiO as a layer and provide our perspective to accelerate the improvement of these technologies. Overall, we show that adequately doped and passivated NiO might be an ideal hole selective layer in every possible application of perovskite solar cells.

The power conversion efficiency of NiO based perovskite solar cells has recently hit a record 22.1%. Here, the main advances are reviewed and the role of NiO in the next breakthroughs is discussed.     

Circular‐Dichroism Studies on Artemisinin and Epiartemisinin and Their β‐Cyclodextrin Complexes in Solution

The circular dichroism (CD) spectra of the powerful antimalarian active principle artemisinin (ART; 1 ) from Artemisia annua, and of epiartemisinin (EPI, 2), its C(7) epimer, were studied in solution in the presence and absence of β‐cyclodextrin (β‐cd). A significant inversion of sign in the region of the second electronic transition was detected. The rotational strengths were successfully calculated within the time‐dependent density functional theory (DFT), which enabled us to establish a correlation between the molecular recognition and the biological acitivities of the two isomers.     

Asymmetric Synthesis in the Presence of Cyclodextrins

Oxidative couplings of 2-naphthol, 6-bromo-2-naphthol and2-naphthylamine were achieved at room temperature in the presence of H₂O₂, horseradish peroxidase and a suitable cyclodextrin.2-Thionaphthol behaved differently, yielding the corresponding disulfide. Yields of binaphthyl derivatives were generally excellent, and a fairly good enantiomeric excess was observed. Under similar reaction conditions methyl 2-(6-methoxy-2-naphthyl) propanoate, when treated with esterase in the presence of cyclodextrin, yielded naproxen (a well-known anti-inflammatory drug) with a good enantiomeric excess. No reaction product was detected in the absence of cyclodextrin. Cyclodextrins do not act as simple transfer agents.     

1H-NMR,Ultraviolet and infrared spectra of some (Z)-α-(phenyl)-β-(2-furyl), -(2-pyrrolyl) and -(N-methyl-2-pyrrolyl)acrylonitriles

The ¹H-nmr data of some (Z)-α-(p-substituted-phenyl)-β-(2-furyl), -(2-pyrrolyl), and -(N-methyl-2-pyrrolyl)-acrylonitriles have been investigated to indicate the preferred conformation and to establish the conformational preferences of the β-heterocyclic ring. The ultraviolet spectra have been discussed in order to obtain information about the chromophores responsible for the absorption. The infrared spectra have been analyzed for the identification of the main absorption frequencies of cyano and ethylenic groups and to assign the characteristic absorption bands to specific normal vibrations of the heteroaromatic nuclei.     

A synthetic divalent cholera toxin glycocalix[4]arene ligand having higher affinity than natural GM1 oligosaccharide

A high-affinity ligand of cholera toxin, the divalent glycocalix[4]arene 1, was obtained by exploiting a combination of structure-based design of glycomimetic monovalent ligands and affinity enhancements by multivalent presentation through a calix[4]arene scaffold. It exhibits a slightly higher affinity for the toxin than its natural ligand, the GM1 oligosaccharide.     

An artificial ionophore based on a polyhydroxylated steroid dimer

The Na+ transporting properties of the first member of a new class of artificial ionophores, based on a C2-symmetric polyhydroxylated steroid dimer, are described.     

Mathematical model for the analytical signal of an herbicide sensor based on the reaction centre of Rhodobacter sphaeroides

This paper introduces a mathematical model which makes it possible both to determine the concentration of photosynthetic herbicides and to obtain a quantitative parameter in order to compare their activity using a previously described sensing system. The working principle involves the changes in absorption properties at 860 nm of the reaction centre (RC) isolated from the bacteria Rhodobacter sphaeroides when photosynthetic herbicides are present. The method has been used for the determination and activity comparison of five photosynthetic herbicides: diuron, atrazine, terbutryn, terbuthylazine and simazine. Detection limits obtained were 2.2, 0.75, 0.046, 0.25, and 1.4 μM, respectively. The resulting order for the different herbicides according to their action on RC was: terbutryn > terbuthylazine > atrazine > simazine > diuron.     

Relaxation processes of the liquid crystal ME6N in the isotropic phase studied by Raman scattering experiments

We have investigated the Raman profiles of the nu(C[Triple Bond]N) and nu(C=O) vibrational modes of the nematic liquid crystal ME6N (4-cyanophenyl-4(')-hexylbenzoate) in the isotropic phase at different temperatures and used them as probes of the dynamics and structural organization of this liquid. The vibrational time correlation functions of the nu(C[Triple Bond]N) mode, rather adequately interpreted within the assumption of exponential modulation function (the Kubo-Rothschild theory), indicate that the system experiences an intermediate dynamical regime that gets only slightly faster with increasing temperature. However, this theory fails in predicting the non-exponential behavior that the time correlation functions manifest in the long time range (t>3 ps). For this reason we have additionally approached the interpretation of vibrational correlation functions in terms of the theory formulated by Rothschild and co-workers for locally structured liquids. The application of this theory reveals that the molecular dynamics in this liquid crystal in the isotropic phase is that deriving from a distribution of differently sized clusters, which narrows as the temperature increases. Even at the highest temperature reached in this study (87 degrees C above the nematic-isotropic transition), the liquid has not yet achieved the structure of the simple liquid and the dynamics has not reached the limit of the single channel process. The vibrational and orientational relaxations occur in very different time scales. The temperature independence of the orientational dynamics in the whole range from 55 degrees C to 135 degrees C has been referred to the nonhydrodynamic behavior of the system, arising when local pseudonematic structures persist for times longer than the orientational relaxation. The occurrence of the process of resonant vibrational energy transfer between the C=O groups of adjacent molecules has been revealed in the isotropic phase by a slightly positive Raman noncoincidence effect in the band associated with the nu(C=O) mode. A qualitative interpretation is tentatively given in terms of partial cancellation of contributions deriving from structures having opposite orientations of their C=O groups.