Enhanced Fluorescence Properties of Poly(phenylene ethynylene)-Conjugated Polyelectrolytes Designed to Avoid Aggregation.

A new class of nonaggregating conjugated polyelectrolytes exhibits efficient fluorescence in aqueous solution. Analysis by optical spectroscopy and transmission electron microscopy reveals a unique structure-property correlation between oxygen substitution and aggregation.

trans-thionate derivatives of Pt(II) and Pd(II) with water-soluble phosphane PTA and DAPTA ligands: antiproliferative activity against human ovarian cancer cell lines.

A series of PTA and DAPTA platinum(II) and palladium(II) thionate complexes of the type trans-[M(SN)2P2] were prepared from the reaction of cis-[MCl2P2] [M = Pt, Pd; P = PTA (1,3,5-triaza-7-phosphaadamantane), DAPTA (3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane)] with the in situ generated sodium salts of the heterocyclic thiones S-m-methylpyrimidine-2-thione, S-4,6-dimethylpyrimidine-2-thione, S-4,6-dihydroxypyrimidine-2-thione, benzothiazole-2-thione, benzoxazole-2-thione, S-1,3,4,-thiadiazole-2-thione, S-4,5-H-thiazolan-2-thione, and S-pyrimidine-4(1H)-one-2-thione. The X-ray structures of six of the compounds confirm the trans disposition and, only in the case of [Pd2Cl2(S-pyrimidine-4(1H)-one-2-thionate)2(PTA)2], a dinuclear structure with a Pd-Pd distance of 3.0265(14)Å was observed. In vitro cytotoxicities against human ovarian cancer cell lines A2780 and A2780cisR were evaluated for ten complexes showing a high inhibition of cellular growth with a comparable inhibitory potency (IC50) against A2780 cells to that of cisplatin. Notably, the compounds also show significant (up to 7-fold higher) activity in cisplatin-resistant A2780cisR cell lines.

Does conjugation help exciton dissociation? a study on poly(p-phenylene)s in planar heterojunctions with C60 or TNF.

Internal photocurrent quantum yields near 100% can be obtained from the separation of loosely bound geminate pairs when sufficiently large electric fields are applied to organic heterojunctions. The fields needed for complete electron-hole dissociation decrease to those prevailing in organic solar cells under operating conditions when well-conjugated polymers are employed.

Dye-terminated, hyperbranched polytruxenes and polytruxene-block-polythiophene multiblock copolymers made in an "AB2 + A" approach.

Novel dye-terminated, hyperbranched polytruxenes and polytruxene-block-polythiophene multiblock copolymers have been synthesized in a simple "AB(2) + A" approach. Photoexcitation into the higher energy polytruxene absorption band results in an efficient excitation energy transfer to the peripheral dye or polythiophene blocks.

Fluorescent nanoparticles based on a microporous organic polymer network: fabrication and efficient energy transfer to surface-bound dyes.

Well-defined nanoparticles composed of a tetraphenylmethane-based microporous polymer network with an average particle diameter of 30-60 nm were fabricated by a miniemulsion polymerization technique. Strong green emission was observed and efficient excitation energy transfer from nanoparticles to surface-bound dye molecules was explored.

Triplet-triplet annihilation in a series of poly(p-phenylene) derivatives.

We have studied the temperature dependence of phosphorescence (Ph) and delayed fluorescence (DF) in two series of poly(p-phenylene) derivatives within a temperature range from 10 to 300 K under quasi-stationary conditions. One set of materials consists of the dimer, trimer, and polymer of ethylhexyl-substituted poly(fluorene) (PF2/6) and thus allows us to assess the effects of oligomer length. The second series addresses the influence of energetic disorder and conjugation length by being composed of the polymers alkoxy-substituted poly(p-phenylene) (DOO-PPP), poly(indenofluorene) (PIF), and ladder-type poly(p-phenylene) (MeLPPP). Under low light intensities, the DF features a maximum at a certain temperature T(max). For the dimer and trimer, the T(max) coincides with the temperature at which the phosphorescence has decayed to 1/2 of the value at 10 K, while T(max) shifts to lower temperature values along the series DOO-PPP, PIF, and MeLPPP and approaches T = 0 K for MeLPPP. By applying conventional kinetic equations we show that the occurrence of a maximum in the DF intensity is the consequence of generalized thermally activated triplet exciton transport toward quenching sites. We find the quenching rates at 0 K to be in the range of 1 s(-1) for the polymers, while they are more than an order of magnitude lower for the oligomers.

Unexpected side chain oxidation in a swivel cruciform oligothiophene.

Two swivel cruciform oligothiophenes are investigated for the occurrence of oxidative ring closure reactions. Surprisingly, instead of intramolecular cyclizations, a regioselective side chain oxidation of two of the four alpha-methylene groups next to the terminal thiophene rings is detected for one of the oligomers. Such side chain oxidations may be one unintended degradation pathway in oligothiophene-based organic semiconductors used as the active layer of organic field effect transistors (OFETs), organic light emitting diodes (OLEDs), and organic solar cells (OSCs).