A metallo-supramolecular network undergoes reversible redox chemistry on indium-tin oxide (ITO) coated glass substrates with concurrent color change. The switching time, long-term stability, and coloration efficiency are competitive with polymeric materials such as the industrially important PEDOT.

Activation of a strong aryl-Br bond of a halogenated vinylarene by nickel(0) is demonstrated in the presence of aryl-I containing substrates. eta2-Coordination of Ni(PEt3)2 to the C=C moiety of halogenated vinylarenes is kinetically preferable and is followed by an intramolecular aryl-halide bond activation process. This "ring-walking" process is quantitative and proceeds under mild reaction conditions in solution. Mechanistic studies indicate that the metal insertion into the aryl-halide bond is not the rate-determining step. The reaction obeys first-order kinetics in the eta2-coordination complexes with almost identical activation parameters for Br and I derivatives. The ring-walking process is kinetically accessible as shown by density functional theory (DFT) calculations at the PBE0/SDB-cc-pVDZ//PBE0/SDD level of theory.

The internalization mechanism and subcellular distribution of hypericin (Hyp), hypericin tetrasulfonic acid (HypS4) and 1,3,4,6-tetrahydroxyhelianthrone (Hel) were studied in murine colon carcinoma CT26 cells, in protein-free medium or in the presence of serum proteins. The correlation between the extent of uptake of the sensitizers by cells that were incubated in the presence of different serum components, and the internalization mechanisms, was studied. The results indicate that sensitizer internalization may be a result of three mechanisms: partitioning, pinocytosis and endocytosis, and as a direct consequence is targeted to specific subcellular sites. While Hyp and Hel, the two lipophilic sensitizers, were localized in the endoplasmic reticulum after protein-free internalization, the hydrophilic HypS4 was localized in the cytoplasmic membrane and in lysosomes. An endolysosomal internalization route was revealed for Hyp and Hel under serum-enriched conditions showing lysosomal localization, as for HypS4. The lysosomal accumulation of Hyp-serum and specifically Hyp-LDL points to an endocytotic mechanism which is supported by its higher uptake parameter in an LDL-enriched medium, compared to the medium with 10% serum. The different uptake parameters of Hyp to cells, with or without serum, reflect the different mechanisms. Smaller differences in the uptake parameter for HypS4 reflect the distinction between partitioning and endocytosis, which, in this case, are both targeted to the lysosomes. The same uptake parameter of Hel to cells incubated in media with or without serum indicates the absence of the endocytotic mechanism. The interrelationship between subcellular targeting and photodynamic treatment was shown for the three sensitizers Hyp was found to be the most efficient sensitizer for PDT under our illumination protocol and it was dependent on internalization and localization sites.

Polycrystalline halogen-bonded assemblies fabricated by physical vapor deposition (PVD) exhibit controllable morphologies and microstructures. Although the solid-state packing may vary going from a solution crystal growth process (used for chromophore single-crystal determination) to a vapor-phase deposition process (used for PVD film fabrication), the corresponding film microstructures are independent of the substrate surface chemistry.

pH dependent absorption and fluorescence spectra of hypericin 1 and its octahydroxy analogue 3 demonstrate their acidic properties, their deprotonation occurring in the ground and excited states from OH in the bay region and in the peri position to the carbonyl, respectively; the presence of the anion of 1 in the crystalline state is established by X-ray diffraction.Hypericin 1, an antiviral agent and potential anti-AIDS drug,192 has been recently found to be photoactive, light being presumably responsible for most of its antiviral activity.3-4 We show here that 1 is an acid and is present in the pH range between ca. 4 and 11 only as a monoanion.1 obtained by synthesisst was crystallized as needles from pyridine. A single crystal X-ray diffraction study$ reveals a structure which contains one molecule of 1, two molecules of pyridine and one of water [Fig. l(a)]. All hydrogen atoms were found from a difference Fourier map and were refined in the free manner. The hypericin molecule is distorted, showing a helical twist, the torsion angles of C(3)-C(3a), C(3b)-C( 4) and of C(l0)-C(lOa), C(l0b)-C(11) bonds being 19.2 and 32.4 O respectively, [Fig. l(b)]. Relevant intramolecular distances between bonded H atoms and neighbouring 0 and H atoms are listed in the caption to Fig. 1. The distance between O(3) and O( 4) atoms appears to be remarkably short, 2.36 A,

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Chemical addressing of the metal oxidation state of an osmium-based chromophore monolayer results in modulation of the optical properties in the entire visible region (400−750 nm). The monolayers are thermally robust, and 25 Os2+/Os3+ redox cycles are demonstrated.

A new series of stilbene-based chromophores have been used to prepare structurally related siloxane-based monolayers in order to determine which factors control the intermolecular chromophore-chromophore interactions in the solid state. The reaction of chromophore precursors 4-styrylpyridine (1), 4-[2-(4bromophenyl)-vinyl]-pyridine (2), 4-(2-naphthalen-1-ylvinyl)-pyridine (3), 4-(2-anthracen-9-ylvinyl)-pyridine (4), and 4-(2-pyren-2-ylvinyl)-pyridine ( 5) with excess 3-iodo-n-propyl-1-trimethoxysilane resulted in the corresponding salts 6-10 in quantitative yield. The assembly of chromophores 6-10 on hydrophilic substrates from solution resulted in the formation of densely packed monolayers with a film thickness of ∼1 nm. The average chromophore density (∼1 chromophore/50 Å 2 ) is well within the range that allows π-π stacking to occur. Transmission UV-vis spectroscopy of the siloxane-based films shows that the intermolecular interactions are a function of the aryl groups (e.g., phenyl, bromophenyl, naphthalene, anthracene, and pyrene). Relatively weak electronic interactions occur between the surface-bound chromophores 6, 7, and 10, whereas strong electronic interactions occur between surface-bound chromophores 8 and 9. The series of monolayers on sodium lime glass and polished silicon is characterized by a combination of physicochemical methods including X-ray photoelectron spectroscopy, advancing aqueous contact angle measurements, optical spectroscopy, atomic force microscopy, and synchrotron X-ray reflectivity.