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Fancy a copper? A sensing system for copper(I) ions, based on the interplay between a “classical” chemosensor and a fluorescent silica nanoparticle, is presented (see scheme). The occurrence of properly designed energy transfer processes and the observed increase of the affinity of the nanosystem towards Cu+ improve sensor performance at low metal ion concentrations in living cells.

A new turn-on Cu 2+ fluorescent sensor (CST) having a trehalose moiety, which confers a relatively large solubility in water, has been synthesized. The chemosensor is therefore suitable for studies in aqueous solution. Full potentiometric and UV-vis characterization evidence that at physiological pH CST forms with Cu 2+ a species with a 1 : 1 stoichiometry allowing for a straightforward correlation between CST response and copper(II) concentration. The presence of the trehalose unit does not negatively affect the selectivity of CST for Cu 2+ over a series of metal ions of interest as proven by fluorescence measurements. The novel chemosensor, tested in differentiated neuroblastoma SH-SY5Y cells, is able to detect Cu 2+ in the extracellular region, as well as to track copper transfer processes upon cell stimulation induced by cellular depolarization.

A mononuclear (M20) and a dinuclear (M40) uranyl chiral macrocyclic complex, incorporating both a salen unit containing two phenyl rings linked to a chiral diimine bridge and the (R)-BINOL unit, behaves as an efficient ditopic receptor for achiral and chiral quaternary ammonium salts. Binding affinities in chloroform solution have been measured for 1:1 complexes of many quaternary salts encompassing tetramethylammonium (TMA), tetraethylammonium (TEA), tetrabutylammonium (TBA), and acetylcholine (ACh), as well as trimethylanilinium (TriMAn), benzyltrimethylammonium (BnTriMA), (alpha-methylbenzyl)trimethylammonium and pyrrolidinium cations. The anion of the salt is bound by the hard Lewis acidic uranyl site, with an increasing binding efficiency on increasing the anion hardness (I(-) < Br(-) < Cl(-)), whereas CH-pi or pi-pi attractions by binapthyl moiety, or the salicylaldehyde unit, or the phenyl rings of diimine bridge ensure the recognition of the cation partner. Optimized structures of receptor-anion-cation ternary complexes obtained by MM calculations are supported by 2D-ROESY NMR measurements.

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.

M40 is a four-fold symmetry macrocyclic ligand endowed with axial and central chiral elements, all of R configuration. It promptly binds late lanthanides (Yb(III) and Lu(III) ) yielding a negative helicity, as witnessed by NIR-electronic circular dichroism. In the course of a few hours, a new conformation of the complex takes over, which has opposite helicity and allows for a dynamic free-bound equilibrium. Upon slow solvent evaporation, the original conformation is retrieved and the whole dynamic process can be started again, as in a sandclock, allowing one to envisage applications as a time-marker chiral switch.

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