Photophysical Properties of Oligophenylene Ethynylenes Modified by Donor and/or Acceptor Groups

Amino-OPE glycosides and blue light: a powerful synergy in photodynamic therapy

Herein we report the synthesis and biological properties of sugar-conjugated oligophenylene ethynylene (OPE) dyes, used as novel photosensitizers (PSs) for photodynamic treatment (PDT) under blue light. The OPE-bearing glycosides at both ends are successfully prepared by a Pd-catalyzed Sonogashira cross-coupling reaction. The live-cell imaging studies have shown that these OPE glycosides (including glucose, mannose and maltose derivatives) efficiently penetrate the cytoplasm of cultured HeLa cancer cells. No dark toxicity was observed, but upon irradiating the cells under blue light an extraordinary photodynamic effect was observed at low concentrations (10^-6-10^-8 M). The localization studies indicate that OPE-glucose 1 and OPE-mannose 2 have Golgi patterns, whereas OPE-maltose 3 could be in lysosomes. The PDT and morphological studies in HeLa cells treated with sublethal doses of PS 1-3 revealed that cell death occurs by necrosis.

Rise of Conjugated Poly-ynes and Poly(Metalla-ynes): From Design Through Synthesis to Structure-Property Relationships and Applications

Conjugated poly-ynes and poly(metalla-ynes) constitute an important class of new materials with potential application in various domains of science. The key factors responsible for the diverse usage of these materials is their intriguing and tunable chemical and photophysical properties. This review highlights fascinating advances made in the field of conjugated organic poly-ynes and poly(metalla-ynes) incorporating group 4-11 metals. This includes several important aspects of conjugated poly-ynes viz. synthetic protocols, bonding, electronic structure, nature of luminescence, structure-property relationships, diverse applications, and concluding remarks. Furthermore, we delineated the future directions and challenges in this particular area of research.

Shape-persistent fluorescent tetraphenylmethane dendrimers

We report the first examples of a new class of rigid dendrimers made of three-dimensional tetraphenylmethane units connected by ethynylene linkers.

Oligo(phenylene ethynylene) glucosides: modulation of cellular uptake capacity preserving light ON

A new family of oligo(phenylene ethynylene) (OPE) glucosides has been prepared and characterized. Our results demonstrate that fine-tuning of their photophysical properties can be obtained by acting on the electronics of the core and molecular skeleton. Modulation of the hydrophobic chain length and substituents on the central moieties influences the bioaffinity too. In particular, introducing a NMe2 group on the aromatic central core affords a highly efficient biocompatible fluorescent probe that can be taken up in cytoplasmic vesicles of HEp-2 cells (cells from epidermoid carcinoma larynx tissue). The photophysical behavior, high quantum yield, and stability open the way to the use of the OPE family as stains for cellular imaging analysis by fluorescence microscopy.

Twisting and piezochromism of phenylene-ethynylenes with aromatic interactions between side chains and main chains

This paper describes a series of three-ring phenylene-ethynylenes (PEs) in which specific, non-covalent arene–arene interactions control conformation in the solid-state.

Experimental and theoretical study of the n-doped successive polyanions of oligocruciform molecular wires: up to five units of charge

The electronic structure of polyanions of sterically encumbered triisopropylsilyl-substituted linear and cyclic oligo(phenyleneethynylene)s (Monomer, Trimer, Pentamer, and Triangle) is investigated by electron paramagnetic resonance (EPR), electron nuclear double resonance (ENDOR), and UV/Vis-near-infrared (NIR) spectroscopies, cyclic voltammetry, and theoretical calculations (DFT). Increasing anion orders are generated sequentially in vacuo at room temperature by chemical reaction with potassium metal up to the pentaanion. The relevance of these compounds acting as electron reservoirs is thus demonstrated. Even-order anions are EPR silent, whereas the odd species exhibit different signatures, which are identified after comparison of the measured hyperfine couplings by ENDOR spectroscopy with those predicted by DFT calculations. With increasing size of the oligomers the electron spin density is first distributed over the backbone carbon atoms for the monoanions, and then further localized at the outer phenyl rings for the trianion species. Examination of the UV/Vis-NIR spectra indicates that the monoanions (T(.-) , P(.-) ) exhibit two transitions in the Vis-NIR region, whereas a strong absorption in the IR region is solely observed for higher reduced states. Electronic transitions of the neutral monoanions and trianions are redshifted with increasing oligomer size, whereas for a given oligomer a blueshift is observed upon increasing the charge, which suggests a localization of the spin density.

Fluorescence of 5-arylvinyl-5'-methyl-2,2'-bipyridyl ligands and their zinc complexes

The photophysical properties of 5-arylvinyl-5'-methyl-2,2'-bipyridyls (AVMBs, 1-9, 11) and their zinc complexes were studied. Similar 2,2'-bipyridyl-based ligands have been applied as optical sensors for metal ions and sensitizers for solar energy conversion. The goal of this investigation is to reveal the factors that determine the emission band shift and fluorescence quantum yield change of the title ligand system upon zinc binding. The outcome of this study will not only advance the fundamental understanding of the coordination-driven photophysical processes embodied in the AVMB platform but facilitate the rational design of fluorescent probes for metal ions, particularly zinc. The AVMB ligands were synthesized using the Horner-Wadsworth-Emmons reaction. AVMBs containing electron-donating aryl groups show absorption and emission in the visible region, which can be assigned to charge-transfer transitions as supported by solvent-dependency and computational studies. The binding between AVMB ligands and zinc ion in acetonitrile was studied using isothermal titration calorimetry (ITC). A multicomponent equilibrium model is suggested that explains the multiple transitions evidenced in fluorescence titration isotherms. Coordination to zinc ion stabilizes the charge-transfer excited state of an AVMB ligand with an electron-donating aryl substituent, consequently results in bathochromic shifts in both absorption and emission. However, unlike the emission band shift, the fluorescence quantum yield change upon zinc complex formation does not have an intuitive correlation with the electronic nature of the aryl group. Lifetime measurements using the Time-Correlated Single Photon Counting method enabled the determination of nonradiative and radiative decay rate constants. Both rates of an AVMB ligand decrease upon zinc binding. The collective effect gives rise to the change in fluorescence quantum yield with the apparent lack of correlation with the electronic property of the aryl group.