Pyrene-fluorene hybrids containing acetylene linkage as color-tunable emitting materials for organic light-emitting diodes

New blue- to yellow-emitting materials have been developed by incorporating fluorene-based chromophores on pyrene core with acetylene linkage and using multifold palladium-catalyzed cross-coupling reactions. Both mono- and tetrasubstituted derivatives have been synthesized and characterized. The tetrasubstituted derivatives displayed red-shifted emission when compared to the monosubstituted derivative indicative of an extended conjugation in the former. End-capping with a diphenylamine unit further red-shifted the absorption and emission profiles and imparted a weak dipolar character to the molecules. Amine-containing derivatives displayed positive solvatochromism in the fluorescence spectra indicating a more polar excited state due to an efficient charge migration from the diphenylamine donor to the pyrene π-acceptor. All of the derivatives were tested as emitting dopants with host material 4,4'-bis(9H-carbazol-9-yl)biphenyl (CBP) in a multilayered OLED and found to exhibit bright blue or yellow electroluminescence. The device utilizing 1,3,6,8-tetrasubstituted pyrene derivative as a dopant emitter displayed highest maximum luminescence 4630 cd/m(2) with power efficiency 3.8 lm/W and current efficiency 7.1 cd/A at 100 cd/m(2) attributable to the proper alignment of energy levels that led to the efficient harvesting of excitons. All of the devices exhibited color purity over a wide range of operating voltages.     

Fully functionalized small-molecule probes for integrated phenotypic screening and target identification

Phenotypic screening offers a powerful approach to identify small molecules that perturb complex biological processes in cells and organisms. The tendency of small molecules, however, to interact with multiple protein targets, often with moderate to weak affinities, along with the lack of straightforward technologies to characterize these interactions in living systems, has hindered efforts to understand the mechanistic basis for pharmacological activity. Here we address this challenge by creating a fully functionalized small-molecule library whose membership is endowed with: (1) one or more diversity elements to promote interactions with different protein targets in cells, (2) a photoreactive group for UV light-induced covalent cross-linking to interacting proteins, and (3) an alkyne handle for reporter tag conjugation to visualize and identify cross-linked proteins. A library member was found to inhibit cancer cell proliferation selectively under nutrient-limiting (low glucose) conditions. Quantitative chemoproteomics identified MT-ND1, an integral membrane subunit of the ～1 MDa NADH:ubiquinone oxidoreductase (complex 1) involved in oxidative phosphorylation, as a specific target of the active probe. We further demonstrated that the active probe inhibits complex 1 activity in vitro (IC(50) = 720 nM), an effect that is known to induce cell death in low-glucose conditions. Based on this proof of principle study, we anticipate that the generation and integration of fully functionalized compound libraries into phenotypic screening programs should facilitate the discovery of bioactive probes that are amenable to accelerated target identification and mechanistic characterization using advanced chemoproteomic technologies.     

Using an electrical potential to reversibly switch surfaces between two states for dynamically controlling cell adhesion

Smart surfaces presenting both antifouling molecules with a charged functional group at their distal end, and molecules that are terminated by RGD peptides for cell adhesion, were fabricated and characterized (see picture). By applying potentials of +300 or -300?mV, the surfaces could be dynamically switched to make the peptide accessible or inaccessible to cells.     

Small molecule control of bacterial biofilms

Bacterial biofilms are defined as a surface attached community of bacteria embedded in a matrix of extracellular polymeric substances that they have produced. When in the biofilm state, bacteria are more resistant to antibiotics and the host immune response than are their planktonic counterparts. Biofilms are increasingly recognized as being significant in human disease, accounting for 80% of bacterial infections in the body and diseases associated with bacterial biofilms include: lung infections of cystic fibrosis patients, colitis, urethritis, conjunctivitis, otitis, endocarditis and periodontitis. Additionally, biofilm infections of indwelling medical devices are of particular concern, as once the device is colonized infection is virtually impossible to eradicate. Given the prominence of biofilms in infectious diseases, there has been an increased effort toward the development of small molecules that will modulate bacterial biofilm development and maintenance. In this review, we highlight the development of small molecules that inhibit and/or disperse bacterial biofilms through non-microbicidal mechanisms. The review discuses the numerous approaches that have been applied to the discovery of lead small molecules that mediate biofilm development. These approaches are grouped into: (1) the identification and development of small molecules that target one of the bacterial signaling pathways involved in biofilm regulation, (2) chemical library screening for compounds with anti-biofilm activity, and (3) the identification of natural products that possess anti-biofilm activity, and the chemical manipulation of these natural products to obtain analogues with increased activity.     

Effects of large halides on the structures of lanthanide(III) and plutonium(III) borates

Reactions of LnBr(3) or LnOI with molten boric acid result in formation of Ln[B(5)O(8)(OH)(H(2)O)(2)Br] (Ln = La-Pr), Nd(4)[B(18)O(25)(OH)(13)Br(3)], or Ln[B(5)O(8)(OH)(H(2)O)(2)I] (Ln = La-Nd). Reaction of PuOI with molten boric acid yields Pu[B(7)O(11)(OH)(H(2)O)(2)I]. The Ln(III) and Pu(III) centers in these compounds are found as nine-coordinate hula-hoop or 10-coordinate capped triangular cupola geometries where there are six approximately coplanar oxygen donors provided by triangular holes in the polyborate sheets. The borate sheets are connected into three-dimensional networks by additional BO(3) triangles and/or BO(4) tetrahedra that are roughly perpendicular to the layers. The room-temperature absorption spectrum of single crystals of Pu[B(7)O(11)(OH)(H(2)O)(2)I] shows characteristic f-f transitions for Pu(III) that are essentially indistinguishable from Pu(III) in other compounds with alternative ligands and different coordination environments.     

Regioselective Reduction of 1H-1,2,3-Triazole Diesters

Regioselective reactions can play pivotal roles in synthetic organic chemistry. The reduction of several 1-substituted 1,2,3-triazole 4,5-diesters by sodium borohydride has been found to be regioselective, with the C(5) ester groups being more reactive towards reduction than the C(4) ester groups. The amount of sodium borohydride and reaction time required for reduction varied greatly depending on the N(1)-substituent. The presence of a β-hydroxyl group on the N(1)-substituent was seen to have a rate enhancing effect on the reduction of the C(5) ester group. The regioselective reduction was attributed to the lower electron densities of the C(5) and the C(5) ester carbonyl carbon of the 1,2,3-triazole, which were further lowered in cases involving intramolecular hydrogen bonding.     

Novel Copolymers of Styrene. 15. Phenoxy Ring-Substituted Methyl 2-Cyano-3-Phenyl-2-Propenoates

Electrophilic trisubstituted ethylenes, phenoxy ring-substituted methyl 2-cyano-3-phenyl-2-propenoates, RPhCH=C(CN)CO₂CH₃, where R is 4-(4-BrC₆H₅O), 2-(4-ClC₆H₅O), 3-(4-ClC₆H₅O), 4-(3-ClC₆H₅O), 4-(4-ClC₆H₅O), 4-(4-FC₆H₅O), 2-(3-CH₃OC₆H₅O), 2-(4-CH₃OC₆H₅O), 3-(4-CH₃OC₆H₅O), 4-(4-CH₃OC₆H₅O), 3-(4-CH₃C₆H₅O) were prepared and copolymerized with styrene. The monomers were synthesized by the piperidine catalyzed Knoevenagel condensation of phenoxy ring-substituted benzaldehydes and methyl cyanoacetate, and characterized by CHN analysis, IR, ¹H and ¹³C-NMR. All the ethylenes were copolymerized with styrene (M₁) in solution with radical initiation (ABCN) at 70°C. The compositions of the copolymers were calculated from nitrogen analysis and the structures were analyzed by IR, ¹H and ¹³C-NMR. The order of relative reactivity (1/r₁) for the monomers is 4-(4-CH₃OC₆H₅O) (6.07) > 3-(4-ClC₆H₅O) (3.38) > 3-(4-CH₃OC₆H₅O) (2.78) > 4-(3-ClC₆H₅O) (2.77) > 2-(4-ClC₆H₅O) (2.29) > 3-(4-CH₃C₆H₅O) (1.98) > 4-(4-FC₆H₅O) (1.92) > 4-(4-ClC₆H₅O) (1.89) > 2-(3-CH₃OC₆H₅O) (1.39) > 2-(4-CH₃OC₆H₅O) (0.90) > 4-(4-BrC₆H₅O) (0.77). Relatively high T_g of the copolymers in comparison with that of polystyrene indicates a decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 200-500°C range with residue (2.5-8.0% wt), which then decomposed in the 500-800°C range.     

Copper‐Mediated Deoxygenative Trifluoromethylation of Benzylic Xanthates: Generation of a C?CF3 Bond from an O‐Based Electrophile

The conversion of an alcohol‐based functional group, into a trifluoromethyl analogue is a desirable transformation. However, few methods are capable of converting O‐based electrophiles into trifluoromethanes. The copper‐mediated trifluoromethylation of benzylic xanthates using Umemoto’s reagent as the source of CF₃ to form C? CF₃ bonds is described. The method is compatible with an array of benzylic xanthates bearing useful functional groups. A preliminary mechanistic investigation suggests that the C? CF₃ bond forms by reaction of the substrate with in situ generated CuCF₃ and CuOTf. Further evidence suggests that the reaction could proceed via a radical cation intermediate.