Absolute Asymmetric Synthesis of a Tetrahedral Silver Complex

Even though the isolation of tetrahedral stereoisomers usually presents a synthetic challenge, a highly enantioenriched tetrahedral silver complex could be easily accessed by either crystallization or Viedma ripening. The overall preparation may be regarded as an example of absolute asymmetric synthesis. Experimental results indicate that both crystallization and Viedma ripening follow a similar cluster‐controlled mechanism.     

Identification of Structure–Activity Relationships from Screening a Structurally Compact DNA‐Encoded Chemical Library

Methods for the rapid and inexpensive discovery of hit compounds are essential for pharmaceutical research and DNA‐encoded chemical libraries represent promising tools for this purpose. We here report on the design and synthesis of DAL‐100K, a DNA‐encoded chemical library containing 103 200 structurally compact compounds. Affinity screening experiments and DNA‐sequencing analysis provided ligands with nanomolar affinities to several proteins, including prostate‐specific membrane antigen and tankyrase 1. Correlations of sequence counts with binding affinities and potencies of enzyme inhibition were observed and enabled the identification of structural features critical for activity. These results indicate that libraries of this type represent a useful source of small‐molecule binders for target proteins of pharmaceutical interest and information on structural features important for binding.     

Naphthalenebisimides as photofunctional surfactants for SWCNTs – towards water-soluble electron donor–acceptor hybrids

A water soluble naphthalenebisimide derivative (NBI) was synthesized and probed to individualize, suspend, and stabilize single wall carbon nanotubes (SWCNTs). Besides a comprehensive photophysical and electrochemical characterization of NBI, stable suspensions of SWCNTs were realized in buffered D₂O. Overall, the dispersion efficiency of the NBI surfactant was determined by comparison with naphthalene based references. Successful individualization of SWCNTs was corroborated in several microscopic assays. In addition, emission spectroscopy points to the strong quenching of SWCNT centered band gap emission, when NBIs are immobilized onto SWCNTs. The origin of the quenching was found to be strong electronic communication, which leads to charge separation between NBIs and photoexcited SWCNTs, and, which yields reduced NBIs as well oxidized SWCNTs. Notably, electrochemical considerations revealed that the energy content of these charge separated states is one of the highest reported for SWCNT based electron donor–acceptor hybrids so far.     

Fluorinated Azobenzenes Switchable with Red Light

Molecular photoswitches triggered with red or NIR light are optimal for photomodulation of complex biological systems, including efficient penetration of the human body for therapeutic purposes (“therapeutic window”). Yet, they are rarely reported, and even more rarely functional under aqueous conditions. In this work, fluorinated azobenzenes are shown to exhibit efficient E→Z photoisomerization with red light (PSS_660nm >75 % Z) upon conjugation with unsaturated substituents. Initially demonstrated for aldehyde groups, this effect was also observed in a more complex structure by incorporating the chromophore into a cyclic dipeptide with propensity for self-assembly. Under physiological conditions, the latter molecule formed a supramolecular material that reversibly changed its viscosity upon irradiation with red light. Our observation can lead to design of new photopharmacology agents or phototriggered materials for in vivo use.     

Tetrahalidometallate(II) Ionic Liquids with More than One Metal: The Effect of Bromide versus Chloride

Fifteen N-butylpyridinium salts – five monometallic [C₄Py]₂[MBr₄] and ten bimetallic [C₄Py]₂[M_0.5^aM_0.5^bBr₄] (M=Co, Cu, Mn, Ni, Zn) – were synthesized, and their structures and thermal and electrochemical properties were studied. All the compounds are ionic liquids (ILs) with melting points between 64 and 101 °C. Powder and single-crystal X-ray diffraction show that all ILs are isostructural. The electrochemical stability windows of the ILs are between 2 and 3 V. The conductivities at room temperature are between 10⁻⁵ and 10⁻⁶ S cm⁻¹. At elevated temperatures, the conductivities reach up to 10⁻⁴ S cm⁻¹ at 70 °C. The structures and properties of the current bromide-based ILs were also compared with those of previous examples using chloride ligands, which illustrated differences and similarities between the two groups of ILs.     

Adamantyl Side Chains as Anti-Aggregating Moieties in Dyes for Dye-Sensitized Solar Cells

Designing and evaluating novel dye concepts is crucial for the development of the field of dye-sensitized solar cells (DSSCs). In our recent report, the novel concept of tethering the anti-aggregation additive chenodeoxycholic acid (CDCA) to dyes for DSSC was introduced. Based on the performance improvements seen for this modification, the aim of this study is to see if a simplified anti-aggregation unit could achieve similar results. The following study reports the synthesis and photovoltaic characterization of two novel dyes decorated with the steric ethyladamantyl moiety on the π-spacer, and on the triarylamine donor. This modification is demonstrated to be successful in increasing the photovoltages in devices employing copper-based electrolytes compared to the non-modified reference dye. The best photovoltaic performance is achieved by a device prepared with the adamantyl decorated donor dye and CDCA, this device achieves a power conversion efficiency of 6.1 % (Short-circuit current=8.3 mA cm⁻², Open-circuit voltage=1054 mV, Fill factor=0.69). The improved photovoltaic performance seen for the adamantyl decorated donor demonstrate the potential of ethyladamantyl side chains as a tool to ensure surface protection of TiO₂.