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International audience; This work deals with the development of ultra-thin film nanosensors for selective and sensitive detection of toxic Hg2+ cations in aqueous media. 1,8-Bis[(2-aminoethyl)amino]anthraquinone D0 was functionalized by alkoxy groups of different length to prepare ligands D3 and D12 with linear arrangement of two polyamine receptors and two lipophilic alkyl chains. Chemosensor D0 only binds copper(II) and mercury(II) cations in water/methanol (1:1 v/v) solutions with no interference by other metal cations. The introduction of alkoxy groups to the anthraquinone scaffold, which are required to form Langmuir monolayers and ultra-thin films on solid supports, does not change the sensing properties of the anthraquinone D0. In contrast to systems without specific molecular order (i.e. solutions and drop-cast films), Langmuir monolayers and ultra-thin Langmuir-Blodgett films of alkoxy-substituted ligands selectively bind only mercury(II) cations, even in the presence of copper(II) ions and 10 other interfering cations. Selective binding of mercury(II) cations was confirmed by the UV–vis absorption and X-ray fluorescence spectroscopies. Thus, ultra-thin films, in which chemosensor molecules are assembled in highly ordered supramolecular systems, display a higher selectivity as compared to that of disordered molecular systems. Ultra-thin sensory film allows for the selective detection of Hg2+ ions in water when their concentration is exceeded 0.01 μM, which corresponds to the action level for Hg2+ ions in drinking water recommended by the U.S. Environmental Protection Agency. Chemosensor D12 is also suitable for the fabrication of electrochemical sensors for mercury(II) cations that show similar sensitivity.

An ultrathin film, wherein a resonance energy transfer (FRET) from the energy donor monolayer to the analyte sensitive acceptor monolayer is controlled by definable cation binding, was produced, thus proving the feasible concept of non-covalently linked FRET couple based sensors.

Herein we report the synthesis and characterization of a series of new dyads – imidazo-fused Ni(II) porphyrinates, containing polycyclic aromatic hydrocarbons (PAH) at the C-2 position of the imidazole ring, including pyrene – 1Pyr, anthracene – 1An, and diphenylanthracene – 1Ph2An. Electronic communication between the tetrapyrrolic macrocycles and PAH moieties was comprehensively studied by UV–Vis and fluorescence spectra together with quantum-chemical modelling. DFT calculations, including geometry optimization and analysis of the frontier orbitals, has revealed the efficient conjugation of pyrene and anthracene with porphyrin π-system, while 1Ph2An dyad possessed two isolated non-conjugated π-systems. Interestingly, these conclusions could not be unambiguously ruled out of UV–Vis spectroscopy data alone. Finally, the presence or absence of conjugation was confirmed using the analysis of ellipticities of bond critical points, thus proving this method to be a convenient tool to study the conjugation in multichromophoric porphyrin-based systems.

Di- n -octylated tetranitrothiacalix[4]arene, a new multidipolar D-π-A chromophore has been synthesized and the dependence of its aggregation in solution and at the air–water interface on the concentration of solution and spreading solvent has been evaluated.

Nucleophilic substitution of the bis-α-benzyldioximate clathrochelate precursor with ortho-phenylenediamine hydrochloride in the presence of triethylamine as an organic base under mild conditions afforded the macrobicyclic iron(II) complex with an annelated ribbed quinoxaline fragment. This complex easily underwent oxidation in solution with air oxygen leading to its oxidized macrobicyclic derivative with the quinoid ribbed system. Such cage complex with a heterocyclic fragment annelated to its quasi-aromatic polyazomethine electron-withdrawing macrobicyclic framework possesses pronounced oxidative properties and undergoes both the chemical (with metallic lithium) and electrochemical stepwise reduction to the corresponding radical anion macrobicyclic species, registered by EPR, and, then, to the diamagnetic dianionic clathrochelate complex. Such reductions were found to be accompanied by dramatic changes in coloration from blue–violet to yellow (that is characteristic of the macrobicyclic anion radical) and orange–red (that is characteristic of the clathrochelate dianion); these redox and electrochromic properties were studied using cyclic voltammetry and spectroelectrochemistry in solution and in a thin film. The clathrochelates obtained were characterized using elemental analysis, MALDI-TOF mass spectrometry, IR, UV–vis, EPR, 1H, 11B, 19F and 13C{1H} NMR spectroscopy, and by X-ray diffraction; their FeN6-coordination polyhedra possess a distorted trigonal prismatic–trigonal antiprismatic geometry with the distortion angles of approximately 24°. The Fe–N distances vary from 1.89 to 1.94 A, and the heights h of such polyhedra are 2.33 and 2.36 A, respectively. So, the first clathrochelates with redox-innocent encapsulated metal ion and redox-active macrobicycle ligand systems have been prepared and characterized. For the first time, a quasi-aromatic polyazomethine cage metal complex with an annelated redox-active heterocyclic fragment, having an extended π-conjugated system, has been shown to undergo a reversible 2-electron reduction accompanied with electrochromism both in solution and as a thin film.

In the present work, we demonstrate that transversal conductivity and, consequently, electrochemical activity of ultrathin solid films of two structurally similar octa-butoxy and tetra-crown-ether substituted europium bisphthalocyaninates are quite different. It is shown that presence of the crown moieties allows excellent transfer of charge through monomolecular ultrathin films of respectively substituted complex. This enables their redox-multistability, which can be utilized in molecular logic and information storage devices. On the other hand, transversal charge transfer is inhibited in the films of octa-butoxy-substituted bisphthalocyaninate, which might be promising for organic field-effect transistor applications.

In the multilayer systems where monolayers of donor and acceptor fluorophores of different chemical structure are separated by an inert layer, the dependence of nonradiative energy transfer efficiency on the distance between the planar components of a donor–acceptor couple has a maximum at a finite nonzero thickness of the separating layer.