The phase behavior of a polymer‐fullerene bulk heterojunction system that contains bimolecular crystals

Polymer:fullerene blends have been widely studied as an inexpensive alternative to traditional silicon solar cells. Some polymer:fullerene blends, such as blends of poly(2,5‐bis(3‐tetradecylthiophen‐2‐yl)thieno[3,2‐b]thiophene (pBTTT) with phenyl‐c71‐butyric acid methyl ester (PC₇₁BM), form bimolecular crystals due to fullerene intercalation between the polymer side chains. Here we present the determination of the eutectic pBTTT:PC₇₁BM phase diagram using differential scanning calorimetry (DSC) and two‐dimensional grazing incidence X‐ray scattering (2D GIXS) with in‐situ thermal annealing. The phase diagram explains why the most efficient pBTTT:PC₇₁BM solar cells have 75–80 wt % PC₇₁BM since these blends lie in the center of the only room‐temperature phase region containing both electron‐conducting (PC₇₁BM) and hole‐conducting (bimolecular crystal) phases. We show that intercalation can be suppressed in 50:50 pBTTT:PC₇₁BM blends by using rapid thermal annealing to heat the blends above the eutectic temperature, which forces PC₇₁BM out of the bimolecular crystal, followed by quick cooling to kinetically trap the pure PC₇₁BM phase. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Naphthopyranone synthesis via the tandem Michael-Dieckmann reaction of ortho-toluates with 5,6-dihydropyran-2-ones

The tandem Michael-Dieckmann reaction between a series of ortho-toluates and the α,β-unsaturated lactone 25 is described. The tandem reaction delivers substituted naphthopyranones in moderate (20-49%) yields, whilst limitations in the tolerance of this reaction for different substituents on the ortho-toluate are identified.     

Total synthesis of natural and unnatural lamellarins with saturated and unsaturated D-rings

Twenty-eight natural and unnatural lamellarins with either a saturated or an unsaturated D-ring were synthesized according to our developed synthetic route. The key step involved the Michael addition/ring closure (Mi-RC) of the benzyldihydroisoquinoline and alpha-nitrocinnamate derivatives, which provided the 2-carboethoxypyrrole intermediates in moderate to good yields (up to 78% yield). Subsequent hydrogenolysis/lactonization furnished lamellarins with a saturated D-ring in excellent yields (up to 93% yield). DDQ oxidation of the saturated lamellarin acetates led directly to the corresponding unsaturated analogues in 54-95% yield. In addition, only two steps in our developed strategy require column chromatography.     

Ruthenium complexes of the general formula [RuCl2(PHOX)2] and their catalytic activity in the Mukaiyama aldol reaction

New ruthenium phosphinooxazoline (PHOX) complexes were synthesized and applied in the Mukaiyama aldol reaction. Four ruthenium complexes of the general formula [RuCl₂(PHOX)₂] were synthesized from [RuCl₂(dmso)₄] and the corresponding PHOX ligands through thermal ligand exchange. Two of the complexes were characterized structurally. Achiral PHOX ligands gave the ruthenium complexes as single isomers, whereas chiral PHOX ligands gave a mixture of isomers and also some incomplete substitution. After activation by chloride abstraction, one of the new ruthenium complexes was applied as catalyst in the Mukaiyama aldol reaction to give silyl-protected β-hydroxyl alcohols in 74–92% isolated yields (room temperature, 18–24 h reaction time, 1 mol % catalyst loading).     

Analysis of 25 underivatized amino acids in human plasma using ion-pairing reversed-phase liquid chromatography/time-of-flight mass spectrometry

Amino acids in biological fluids have previously been shown to be detectable using liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) with perfluorinated acids as ion-pairing agents. To date, these studies have used precursor mass, retention time and tandem mass spectrometry (MS/MS) to identify and quantify amino acids. While this is a potentially powerful technique, we sought to adapt the method to time-of-flight (TOF)MS. A new application of a recently described liquid chromatographic separation method was coupled with TOFMS to employ accurate mass for qualitative identification; resulting in additional qualitative data not available with standard single quadrupole data. In the current study, we evaluated 25 physiological amino acids and one dipeptide that are routinely quantified in human plasma. Accuracy and precision of the method was evaluated by spiking human plasma with a mix of the 25 amino acids; in addition, the inclusion of a cation-exchange cleanup step was evaluated. The calibration curves were linear over a range from 1.56 to 400 microM. The dynamic range was found to be within physiological levels for all amino acids analyzed. Accuracy and precision for most of the amino acids was between 80-120% spike recovery and <10% relative standard deviation (RSD). The LC/MS technique described in this study relies on mass accuracy and is suitable for the quantitation of free amino acids in plasma.     

Tandem free-radical addition/substitution chemistry and its application to the preparation of novel AT1 receptor antagonists

Benzothiophene and benzoselenophene analogues of the thiophene-containing antihypertensives milfasartan and eprosartan were prepared and tested for AT(1) receptor antagonist properties. While the sulfur-containing systems were prepared following existing methodology, the selenium-containing analogues required the development of novel, tandem free-radical chemistry involving addition of aryl radicals to alkynes, followed by intramolecular homolytic substitution at the higher heteroatom. All four compounds prepared proved to be excellent AT(1) receptor antagonists, with pK(B) estimates of 7.2-9.5.     

Total synthesis and confirmation of the absolute stereochemistry of semiviriditoxin, a naphthopyranone metabolite from the fungus Paecilomyces variotii

The first total synthesis of (S)-semiviriditoxin 2 is described. The approach utilizes a tandem Michael-Dieckmann reaction between ortho-toluate 5 and dihydropyran-2-one 6 to construct the naphthopyranone core, the dihydropyran-2-one 6 being prepared from (R)-1,2-epoxy-4-butanol. Spectroscopic comparison of synthetic (S)-semiviriditoxin 2 with (R)-semivioxanthin 3, prepared in four steps from (R)-propylene oxide, confirmed the (S)-stereochemistry of natural semiviriditoxin from Paecilomyces variotii.     

Using liquid crystals to report membrane proteins captured by affinity microcontact printing from cell lysates and membrane extracts

The chemical heterogeneity of proteins makes development of general and facile surface-based methods for protein analysis a substantial challenge, particularly when analyzing transmembrane proteins. Here, we report a simple surface-based procedure that permits detection of transmembrane proteins from crude cell lysates and cell membrane extracts. The method relies on the use of thermotropic liquid crystals to amplify and report the presence of the transmembrane proteins captured by an affinity ligand on the surface of an elastomeric stamp. A merit of this approach is that the proteins can be imaged on surfaces without requiring the use of matched pairs of antibodies, labels, or complex instrumentation. Detection of epidermal growth factor receptor, a transmembrane glycoprotein, is demonstrated.