No abstract

No abstract

Recognition of enantiomers is one of the most arduous challenges in chemical sensor development. Although several chiral systems exist, their effective exploitation as the sensitive layer in chemical sensors is hampered by several practical implications that hinder stereoselective recognition in solid state. In this paper, we report a new methodology to efficiently prepare chiral solid films, by using a hybrid material approach where chiral porphyrin derivatives are grafted onto zinc oxide nanoparticles. Circular dichroism (CD) evidences that the solid-state film of the material retains supramolecular chirality due to porphyrin interactions, besides an additional CD feature in correspondence of the absorbance of ZnO (375 nm), suggesting the induction of chirality in the underlying zinc oxide nanoparticles. The capability of hybrid material to detect and recognize vapors of enantiomer pairs was evaluated by fabricating gas sensors based on quartz microbalances. Chiral films of porphyrin on its own were used for comparison. The sensor based on functionalized nanostructures presented a remarkable stereoselectivity in the recognition of limonene enantiomers, whose ability to intercalate in the porphyrin layers makes this terpene an optimal chiral probe. The chiroptical and stereoselective properties of the hybrid material confirm that the use of porphyrin-capped ZnO nanostructures is a viable route for the formation of chiral selective surfaces.

Aims This work reports on one of the first attempts to use biofilm‐forming cyanobacteria for biomass and lipid production. Methods and Results Three isolates of filamentous cyanobacteria were obtained from biofilms at different Italian sites and characterized by a polyphasic approach, involving microscopic observations, ecology and genetic diversity (studying the 16S rRNA gene). The isolates were grown in batch systems and in a semi‐continuous flow incubator, specifically designed for biofilms development. Culture system affected biomass and lipid production, but did not influence the fatty acid profile. The composition of fatty acids was mainly palmitic acid (>50%) and less amounts of other saturated and monounsaturated fatty acids. Only two isolates contained two polyunsaturated fatty acids. Conclusions Data obtained from the flow‐lane incubator system would support a more economical and sustainable use of the benthic micro‐organisms for biomass production. The produced lipids contained fatty acids suitable for a high‐quality biodiesel production, showing high proportions of saturated and monounsaturated fatty acids. Significance and Impact of the Study Data seem promising when taking into account the savings in cost and time derived from easy procedures for biomass harvesting, especially when being able to obtain the co‐production of other valuable by‐products.

The solution behavior of the cationic complexes [Pd(η3-allyl)(P−N)]+ (P−N = o-(PPh2)C6H4CHNR (R = C6H4OMe-4, Me, CMe3, (R)-bornyl); allyl = propenyl (1a−4a) and 3-methyl-2-butenyl (1b−4b)) consists essentially of three dynamic processes:  (i) a very fast conformational change of the P−N chelate ring, which moves above and below the P−Pd−N coordination plane, (ii) a relatively fast η3−η1−η3 interconversion which brings about a syn−anti exchange only for the allylic protons cis to phosphorus; (iii) a slower apparent rotation of the η3-allyl ligand around its bond axis. For 1b−3b, two geometrical isomers are observed, the predominant one having the allyl CMe2 group trans to phosphorus. The complexes 4a and 4b, containing the chiral (R)-bornyl group, are present in solution with two and four diastereomeric species, respectively. The X-ray structural analysis of 4b(ClO4) shows the presence of two diastereomeric molecules in the unit cell, both having distorted-square-planar coordination geometries, characterized by rather elongated Pd−CMe2 bonds trans to phosphorus and by a marked distortion of the allyl ligand, which is rotated away from the PPh2 group. The complexes [Pd(η3-allyl)(P−N)]+ react with secondary amines HY in the presence of fumaronitrile, yielding [Pd(η2-fn)(P−N)] and allylamines. Under pseudo-first-order conditions the amination rates obey the laws k obs = k 2[HY] + k 3[HY]2 for 1a−4a and k obs = k 2[HY] for 1b, 3b, and 4b. The k 2 term is related to direct bimolecular attack on a terminal allyl carbon of the substrate, whereas the k 3 term is ascribed to parallel attack by a further amine molecule on the intermediate [Pd(allyl)(P−N)(HY)]+. The k 2 values increase with increasing basicity and decreasing steric hindrance of the amine, and with increasing electron-withdrawing ability and increasing bulkiness of the P−N nitrogen substituent. The higher amination rates for [Pd(η3-allyl)(P−N)]+, compared to [Pd(η3-allyl)(α-diimine)]+, are essentially due to lack of displacement equilibria of the P−N ligand by amines.