Rigidly Tethered Bis-phosphoric Acids: Generation of Tunable Chiral Fluorescent Frameworks and Unexpected Selectivity for the Detection of Ferric Ions.

We describe the straightforward synthesis of a series of bis-phosphoric acids (R,R)-1 a-d, featuring two chiral 1,1'-binaphthyl-phosphoric acid units that are tethered by rigid, π-conjugated linkers. The nature of the linker has a profound influence on the properties of the bis-phosphoric acids, such as their self-association behavior and their interaction with metal ions. This led to the identification of one preferred bis-phosphoric acid (R,R)-1 d, which shows selective fluorescence quenching in the presence of ferric ions (Fe3+ ). Thus, (R,R)-1 d could be applied for the detection of Fe3+ , even in the presence of a variety of other metal ions. The chiral nature of the bis-phosphoric acid enables the interaction with Fe3+ to be followed by CD spectroscopy, providing a complementary detection mode with the same probe.

Turn-On Fluorescence in Tetra-NHC Ligands by Rigidification through Metal Complexation: An Alternative to Aggregation-Induced Emission.

Two tetraphenylethylene (TPE) bridged tetraimidazolium salts, [H4 L-Et](PF6 )4 and [H4 L-Bu](PF6 )4 , were used as precursors for the synthesis of the dinuclear AgI and AuI tetracarbene complexes [Ag2 (L-Et)](PF6 )2 , [Ag2 (L-Bu)](PF6 )2 , [Au2 (L-Et)](PF6 )2 , and [Au2 (L-Bu)](PF6 )2 . The tetraimidazolium salts show almost no fluorescence (ΦF <1 %) in dilute solution while their NHC complexes display fluorescence "turn-on" (ΦF up to 47 %). This can be ascribed to rigidification mediated by the restriction of intramolecular rotation within the TPE moiety upon complexation. DFT calculations confirm that the metals are not involved in the lowest excited singlet and triplet states, thus explaining the lack of phosphorescence and fast intersystem crossing as a result of heavy atom effects. The rigidification upon complexation for fluorescence turn-on constitutes an alternative to the known aggregation-induced emission (AIE).

Fluorescence quenching in ß-cyclodextrin vesicles: membrane confinement and host-guest interactions.

Fluorescent ß-cyclodextrin vesicles (ß-CDV) that display host cavities available for host-guest interactions at the vesicle surface were prepared by incorporation of the hydrophobic spirobifluorene-based dye 1 into the membrane of unilamellar vesicles. Fluorescence quenching of dye 1 was observed in the presence of different quenchers. Methyl viologen 2 does not quench dye 1 because it does not bind to ß-CDV. 4-Nitrophenol 3 and 4-nitrophenol covalently connected to adamantane 4 quench the fluorescence of dye 1 in neutral solution, but by different mechanisms according to lifetime measurements. The quenching efficiency of 3 is pH dependent due to the presence of the phenolate form. Competition experiments with excess host and guest showed that 3 is likely to diffuse in and out of the membrane, while 4 forms an inclusion complex with ß-CDV leading to close contact and efficient quenching. Our findings confirm that this dynamic supramolecular system is a versatile model to investigate quenching and recognition processes in bilayer membranes.

Effect of the C(3)-Substituent in Verdazyl Radicals on their Profluorescent Behavior.

Methods for the detection of reactive intermediates such as transient radicals are important in organic chemistry, polymer chemistry, biology or medicine. Along these lines we recently reported that 1,5-diphenyl-6-oxo verdazyl radicals can be used as fluorescent spin sensors. In situ generated C-centered radicals are efficiently trapped by the verdazyls, which in turn undergo transformation from a paramagnetic non-fluorescent state to a diamagnetic fluorescent state. Whereas the N-phenyl substituent in the spin probes is of high importance for obtaining profluorescent behavior, the effect of the C(3)-substituent has not been investigated to date. We herein present the synthesis and characterization of various 1,5-diphenyl-6-oxo-verdazyl radicals bearing differently hybridized C-substituents at the C(3) position. Steady-state and time-resolved fluorescence spectroscopy in solution and in the solid state along with time-dependent density functional theory (TDDFT) calculations reveal that a C(3)-aryl substituent is crucial for obtaining fluorescence after spin trapping. In addition, it is shown that the emission wavelength of the C(3)-aryl substituted verdazyl derivatives can be tuned by selective destabilization of the HOMO and the LUMO.

Cobalt(III)-catalyzed directed C-H coupling with diazo compounds: straightforward access towards extended π-systems.

The first highly efficient and scalable cobalt-catalyzed directed C-H functionalization with carbene precursors is presented. This methodology provides a modular route towards a new class of conjugated polycyclic hydrocarbons with tunable emission wavelengths both in solution and in the solid state.

Rh(III) -Catalyzed C-H Activation with Pyridotriazoles: Direct Access to Fluorophores for Metal-Ion Detection.

The first C-H bond activation with pyridotriazoles as coupling partners is presented using a Rh(III) catalyst. The pyridotriazoles can be used as new carbene precursors in C-H activation for direct access to novel fluorescent scaffolds. These tunable fluorophores can be applied for the detection of metal ions.

Scanning-tunneling-spectroscopy-directed design of tailored deep-blue emitters.

Frontier molecular orbitals can be visualized and selectively set to achieve blue phosphorescent metal complexes. For this purpose, the HOMOs and LUMOs of tridentate Pt(II) complexes were measured using scanning tunneling microscopy and spectroscopy. The introduction of electron-accepting or -donating moieties enables independent tuning of the frontier orbital energies, and the measured HOMO-LUMO gaps are reproduced by DFT calculations. The energy gaps correlate with the measured and the calculated energies of the emissive triplet states and the experimental luminescence wavelengths. This synergetic interplay between synthesis, microscopy, and spectroscopy enabled the design and realization of a deep-blue triplet emitter. Finding and tuning the electronic "set screws" at molecular level constitutes a useful experimental method towards an in-depth understanding and rational design of optoelectronic materials with tailored excited state energies and defined frontier-orbital properties.

Phosphorescent Pt(ii) complexes spatially arrayed in micellar polymeric nanoparticles providing dual readout for multimodal imaging.

In this paper we report phosphorescent Pt(ii) complexes as monomers which can be directly incorporated into growing polymers. Due to the amphiphilic nature of the polymers they can self-assemble into micellar nanoparticles, where the phosphorescent Pt(ii) complexes can arrange selectively in the core or shell of the nanoparticles. The complexes enable dual orthogonal imaging, made possible by the heavy metal, which enhances the contrast for these micelles in electron microscopy and facilitates spin-orbit coupling that turns on microsecond lifetime luminescence.

Corrigendum to "Formation of Silver Nanoclusters from a DNA Template Containing Ag(I)-Mediated Base Pairs".

[This corrects the article DOI: 10.1155/2016/7485125.].

Toward Tunable Electroluminescent Devices by Correlating Function and Submolecular Structure in 3D Crystals, 2D-Confined Monolayers, and Dimers.

The synthesis of new Pt(II) complexes bearing tailored cyclometalated C^N*N^C luminophores is reported along with their photophysical properties. The emission of the monomeric species can be blue shifted upon formal isosteric replacement of two C-H units by N atoms at the two cyclometalating rings. Their remarkable stability upon sublimation was demonstrated by means of scanning tunneling microscopy, which also revealed a defined self-assembly behavior leading to supramolecular arrays, showing a 3-fold symmetry in 2D-confined monolayers. The supramolecular organization is driven by van der Waals interactions of the side chains and does not depend on the nature of the luminophores, as also observed in the crystalline phases showing no significant Pt-Pt interactions in 3D. Conversely, the luminescence properties in glassy matrices at 77 K and in amorphous solids are indicative of intermolecular interactions with sizable intermetallic coupling, which was demonstrated by reproducing the emission spectra of dimeric species by means of (TD)DFT calculations. The tendency toward aggregation was also traceable by cyclic voltammetry, whereas thermogravimetric analyses confirmed their stability. Solution-processed and vacuum-deposited OLED devices showed a concentration-dependent electroluminescence that red shifts with increasing doping ratios. Due to the stability of the complexes, solution-processed and vacuum-deposited devices showed identical electroluminescence spectra. Besides favoring aggregation, introduction of two N atoms has a detrimental effect on the device performance, due to the prolonged excited-state lifetimes favoring triplet-triplet annihilation.

Phosphorescent Pt(ii) complexes bearing a monoanionic C

A versatile design strategy is presented towards new monoanionic pincer luminophores, showing that cyclometallating C^N^N ligands can yield phosphorescent Pt(ii) complexes even if a neutral 1,2,3-triazole ring is inserted by click chemistry. The overall charge, intermolecular interactions and excited state properties can be manipulated and controlled by varying the nature of the ancillary ligand, and its effect on the structural and the triplet state characteristics can be thoroughly investigated and correlated by means of theory and spectroscopy.

Solid Solution Quantum Dots with Tunable Dual or Ultrabroadband Emission for LEDs.

Quantum dots that efficiently emit white light directly or feature a "candle-like" orange photoluminescence with a high Stokes shift are presented. The key to obtaining these unique emission properties is through controlled annealing of the core Cu-In-Ga-S quantum dots in the presence of zinc ions, thus forming Zn-Cu-In-Ga-S solid solutions with different distributions of the substitution and dopant elements. The as-obtained nanocrystals feature excellent quantum yields of up to 82% with limited or even eliminated reabsorption and a color rendering index of bare particles of up to 88, enabling the production of high-quality white LEDs using a single color converter layer. Furthermore, the color properties can be tuned by changing the experimental conditions as well as by varying the excitation wavelength. The multicomponent luminescence mechanism is discussed in detail based on similar literature reports. White LEDs with unparalleled color quality and competitive luminous efficacies are presented herein.

Formation of Silver Nanoclusters from a DNA Template Containing Ag(I)-Mediated Base Pairs.

A series of DNA double helices containing different numbers of silver(I)-mediated base pairs involving the artificial nucleobases imidazole or 2-methylimidazole has been applied for the generation of DNA-templated silver nanoclusters. The original Ag(I)-containing nucleic acids as well as the resulting nanoclusters and nanoparticles have been characterized by means of UV/Vis spectroscopy, circular dichroism (CD) spectroscopy, fluorescence spectroscopy, and transmission electron microscopy (TEM). The results show for the first time that metal-mediated base pairs can be used for the templated growth of metal nanoclusters.

Agglutination of bacteria using polyvalent nanoparticles of aggregation-induced emissive thiophthalonitrile dyes.

A novel class of aggregation-induced emissive bis(phenylthio)phthalonitrile dyes were synthesized. These dyes assembled into nanoparticles that were equipped with mannose units. The nanoparticles underwent selective interactions with lectins and bacteria. The bright fluorescent aggregates aid in the visualization of the agglutination of bacteria.

Photofunctional surfaces for quantitative fluorescence microscopy: monitoring the effects of photogenerated reactive oxygen species at single cell level with spatiotemporal resolution.

Herein, we report on the implementation of photofunctional surfaces for the investigation of cellular responses by means of quantitative fluorescence microscopy. The developed substrates are able to produce reactive oxygen species under the fluorescence microscope upon irradiation with visible light, and the behavior of cells grown on these surfaces can be consequently investigated in situ and in real time. Moreover, a suitable methodology is presented to simultaneously monitor phototriggered morphological changes and the associated molecular pathways with spatiotemporal resolution employing time-resolved fluorescence anisotropy at the single cell level. The results showed that morphological changes can be complemented with a quantitative evaluation of the associated molecular signaling cascades for the unambiguous assignment of reactive oxygen species-related photoinduced apoptosis. Indeed, similar phenotypes are associated with different cellular processes. Our methodology facilitates the in vitro design and evaluation of photosensitizers for the treatment of cancer and infectious diseases with the aid of functional fluorescence microscopy.

Profluorescent verdazyl radicals - synthesis and characterization.

The synthesis and characterization of various 6-oxo-verdazyl radicals and their diamagnetic styryl radical trapping products are presented. It is shown that styryl radical trapping products derived from N-phenyl verdazyls show fluorescence whereas the N-methyl congeners are non-fluorescent. In the parent N-phenyl verdazyls fluorescence is fully quenched which renders these compounds highly valuable profluorescent radical probes.

Photophysical efficiency-boost of aqueous aluminium phthalocyanine by hybrid formation with nano-clays.

Novel organic-inorganic hybrid materials comprising nanoscaled layered silicates and native aluminium hydroxide phthalocyanine (Al(OH)Pc) allowed for the first time the exploitation of their unique photophysical properties in aqueous ambience. In particular, we were able to observe the efficient emission of Al(OH)Pc-nanoclay hybrids and generation of singlet oxygen in aqueous solution.

Facile synthesis of a peptidic Au(I)-metalloamphiphile and its self-assembly into luminescent micelles in water.

We report a short synthetic route for the preparation of a peptidic Au(I)-metalloamphiphile which, in buffered environments of physiological ionic strength, self-assembles into luminescent micellar nanostructures of 14 nm in diameter.

Near-field photochemical and radiation-induced chemical fabrication of nanopatterns of a self-assembled silane monolayer.

A general concept for parallel near-field photochemical and radiation-induced chemical processes for the fabrication of nanopatterns of a self-assembled monolayer (SAM) of (3-aminopropyl)triethoxysilane (APTES) is explored with three different processes: 1) a near-field photochemical process by photochemical bleaching of a monomolecular layer of dye molecules chemically bound to an APTES SAM, 2) a chemical process induced by oxygen plasma etching as well as 3) a combined near-field UV-photochemical and ozone-induced chemical process, which is applied directly to an APTES SAM. All approaches employ a sandwich configuration of the surface-supported SAM, and a lithographic mask in form of gold nanostructures fabricated through colloidal sphere lithography (CL), which is either exposed to visible light, oxygen plasma or an UV-ozone atmosphere. The gold mask has the function to inhibit the photochemical reactions by highly localized near-field interactions between metal mask and SAM and to inhibit the radiation-induced chemical reactions by casting a highly localized shadow. The removal of the gold mask reveals the SAM nanopattern.