Benzodifuran‐containing well‐defined π‐conjugated polymers for photovoltaic cells

Two well‐defined alternating π‐conjugated polymers containing a soluble electroactive benzo[1,2‐b:4,5‐b′]difuran (BDF) chromophore, poly(BDF‐(9‐phenylcarbazole)) (PBDFC), and poly(BDF‐benzothiadiazole) (PBDFBTD) were synthesized via Sonogashira copolymerizations. Their optical, electrochemical, and field‐effect charge transport properties were characterized and compared with those of the corresponding homopolymer PBDF and random copolymers of the same overall composition. All these polymers cover broad optical absorption ranges from 250 to 750 nm with narrow optical band gaps of 1.78–2.35 eV. Both PBDF and PBDFBTD show ambipolar redox properties with HOMO levels of ?5.38 and ?5.09 eV, respectively. The field‐effect mobility of holes varies from 2.9 × 10^?8 cm² V^?1 s^?1 in PBDF to 1.0 × 10^?5 cm² V^?1 s^?1 in PBDFBTD. Bulk heterojunction solar cell devices were fabricated using the polymers as the electron donor and [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester as the electron acceptor, leading to power conversion efficiencies of 0.24–0.57% under air mass 1.5 illumination (100 mW cm^?2). These results indicate that their band gaps, molecular electronic energy levels, charge mobilities, and molecular weights are readily tuned by copolymerizing the BDF core with different π‐conjugated units. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

A tin-containing liquid crystalline polymer with two glass temperatures

A tin-containing liquid crystalline side group polymer was synthesized and characterized. Two glass transitions were detected by calorimetric investigations. The X-ray pattern corresponds to a smectic C order of the side groups and a disordered isotropic main chain. Dielectric measurements show two relaxation ranges which are influenced by the glass transitions and a fast local process. The low frequency mechanism can be related to the reorientation of the side groups and the higher glass transition temperature. The second is connected with the α-relaxation of the main chain and freezes in at lower temperatures.     

Triggering the Directional Selectivity of a Ring‐Closure Reaction Leads to Pyridoazacarbazoles with Anticancer Properties

We herein describe a facile and versatile synthetic route to the tetracyclic system of 6‐substituted 5,6‐dihydro‐11H‐pyrido[3,2‐i]‐1‐azacarbazoles with promising anticancer properties. These derivatives are built up by an elegant one‐step base‐catalyzed synthetic procedure from commercially available building blocks. One additional step provides the corresponding skeleton hitherto unknown in the literature. The possibility to synthesize a large library of compounds with various substitution patterns utilizing this method underlines the importance of this synthetic procedure.     

Sensitive detection of drug vapors using an ion funnel interface for secondary electrospray ionization mass spectrometry

In this study, we use an ion funnel (IF) at ambient pressure to enhance the sensitivity of secondary electrospray ionization (SESI). Atenolol, salbutamol and cocaine as test compounds are delivered to the SESI interface in the gas phase and are charged with three nano electrosprays. In our experiments, we show that the compounds can be detected at concentrations in the low pptv range, which is an increase of two orders of magnitude compared with the results without the IF. With a standard SESI interface, the compounds could not be detected at all. With the use of the SESI IF interface for the headspace analysis of bananas and limes, we can detect many more compounds and at higher intensities than with a standard SESI interface. Copyright © 2012 John Wiley & Sons, Ltd.