Assembly of surface-confined homochiral helicates: chiral discrimination of DOPA and unidirectional charge transfer.

Surface-confined double-helical polymers are generated by dynamic covalent assembly with preservation of chirality, metal coordination environment, and oxidation state of the precursor complexes. This one-step procedure involves both in solution and solution-to-surface assembly and resulted in chiral interfaces where pairs of ligands are wrapped around arrays of metal ions. In-plane XRD experiments revealed the formation of a highly ordered structure along the substrate surface. The chirality of the surfaces is expressed by the selective recognition of 3,4-dihydroxyphenylalanine (DOPA). The CD measurements show a response of the Δ-polymer-modified quartz substrates toward D-DOPA, whereas no change was observed after treatment with L-DOPA. These coordination-based interfaces assembled on metal-oxide substrates in combination with a redox-probe, [Os(bpy)3](PF6)2, in solution can resemble the behavior of a rectifier.

Fascinating role of the number of f electrons in dipolar and octupolar contributions to quadratic hyperpolarizability of trinuclear lanthanides-biscopper Schiff base complexes.

The trinuclear [Ln(NO3)3(CuL)2] complexes (Ln = La, Ce, Sm, Eu and Er, L = N,N'-1,3-propylen-bis(salicylideniminato) have been investigated by a combination of HLS and EFISH techniques to evaluate both the dipolar and octupolar contributions to their significant quadratic hyperpolarizability and to confirm that f electrons may tune their second-order NLO response. In the complexes investigated, the major contribution to the total quadratic hyperpolarizability is largely controlled by the octupolar contribution, but the values of both ßEFISH and [parallel]ß(J=1)[parallel], that is the dipolar part, are significantly influenced by the number of f electrons, confirming that the unexpected polarizable character of f electrons may be the origin of such fascinating evidence.

Linear vs exponential formation of molecular-based assemblies.

Here we present the critical role of the molecular structure and reaction parameters on the nature of thin-film growth, using a versatile two-step assembly method with organic and metal-organic chromophores cross-linked with palladium. It was found that the polypyridyl complexes exhibit exponential growth, whereas, under identical conditions, the organic systems exhibit linear behavior. The internal film morphology plays a pivotal role in the storage and usage of the palladium, where a more porous structure results in exponential growth. Interestingly, through proper tuning of the reaction conditions, the growth of the molecular assemblies can be controlled, resulting in a changeover from exponential to linear growth. These findings unequivocally demonstrate the importance of both the internal film structure and deposition conditions on the assembly of molecular-based films.

Viable route for switching of an engineered silica surface using Cu2+ ions at sub-ppm levels.

Quartz substrates were functionalized with a covalent 4-ClCH(2)C(6)H(4)SiCl(3) monolayer. To this, N-(4-hydroxyphenethyl)-4,5-di[(2-picolyl)amino]-1,8-naphthalimide molecules were then covalently bonded, producing a new monolayer of these molecules on silica substrates. The surface chemical characterization of this hybrid material was carried out by X-ray photoelectron spectroscopy. The switching properties of this monolayer were studied at room temperature by UV-vis and XPS measurements. The system has reversible recognition properties for Cu(2+) ions at sub-ppm levels and, therefore, can be reversibly switched using Cu ions as input and the absorbance intensity as output between two states represented by the free base and its copper complex. The adopted synthetic procedure has proven effective to transfer molecular properties to a solid state device.

Self-propagating assembly of a molecular-based multilayer.

Accelerated growth of a molecular-based material that is an active participant in its continuing self-propagated assembly has been demonstrated. This nonlinear growth process involves diffusion of palladium into a network consisting of metal-based chromophores linked via palladium.

In situ metalation of free base phthalocyanine covalently bonded to silicon surfaces.

Free 4-undecenoxyphthalocyanine molecules were covalently bonded to Si(100) and porous silicon through thermic hydrosilylation of the terminal double bonds of the undecenyl chains. The success of the anchoring strategy on both surfaces was demonstrated by the combination of X-ray photoelectron spectroscopy with control experiments performed adopting the commercially available 2,3,9,10,16,17,23,24-octakis(octyloxy)-29H,31H-phthalocyanine, which is not suited for silicon anchoring. Moreover, the study of the shape of the XPS N 1s band gave relevant information on the interactions occurring between the anchored molecules and the substrates. The spectra suggest that the phthalocyanine ring interacts significantly with the flat Si surface, whilst ring-surface interactions are less relevant on porous Si. The surface-bonded molecules were then metalated in situ with Co by using wet chemistry. The efficiency of the metalation process was evaluated by XPS measurements and, in particular, on porous silicon, the complexation of cobalt was confirmed by the disappearance in the FTIR spectra of the band at 3290 cm(-1) due to -NH stretches. Finally, XPS results revealed that the different surface-phthalocyanine interactions observed for flat and porous substrates affect the efficiency of the in situ metalation process.

Blood lead levels, clinico-pathological findings and erythrocyte metabolism in dogs from different habitats.

Biological markers of lead exposure were measured in 20 dogs from five different habitats chosen on the basis of the degree of anthropogenic influence. None of the dogs had clinical signs of lead poisoning. Compared to controls, blood lead concentrations were significantly higher in dogs from industrial areas, confirming the role of lead emissions in environmental pollution and the possible role of dogs as biomonitors of lead exposure in these areas. Whole blood lead concentrations were similar in dogs living in urban and rural areas, probably due to "indirect" lead sources and due to decreased urban lead contamination. As in humans, individual variability was detected. No significant correlation between clinico-pathological changes (hematology, clinical chemistry, Delta-aminolevulinic acid dehydratase activity and other intra-erythrocytic metabolic parameters) and lead concentration were observed. Our findings suggest dogs can be useful as sentinels of environmental lead exposure.