1,8-Diamidocarbazoles: an easily tuneable family of fluorescent anion sensors and transporters

The synthesis, structure and anion recognition properties of an extensive, rationally designed series of bisamide derivatives of 1,8-diaminocarbazole and 1,8-diamino-3,6-dichlorocarbazole are described. Despite simple structures and the presence of only three hydrogen bond donors, such compounds are remarkably strong and selective receptors for oxyanions in DMSO + 0.5%H2O. Owing to their carbazole fluorophore, they are also sensitive turn-on fluorescent sensors for H2PO4− and AcO−, with a more than 15-fold increase in fluorescence intensity upon binding. Despite relatively weak chloride affinity, some of the diamidocarbazoles have also been shown, for the first time, to be very active chloride transporters through lipid bilayers. The binding, sensing and transport properties of these receptors can be easily modulated by the usually overlooked variations in the length and degree of branching of their alkyl side arms. Overall, this study demonstrates that the 1,8-diamidocarbazole binding unit is a very promising and synthetically versatile platform for the development of fluorescent sensors and transporters for anions.Polish National Science Centre for grant OPUS (2011/01/B/ST5/03900). The study was carried out at the Biological and Chemical Research Centre, University of Warsaw, established within a project co-financed by the European Union through the European Regional Development Fund under the Operational Programme Innovative Economy 2007–2013. R. Q. thanks financial support provided by Consejería de Educación – Junta de Castilla y León (Project BU092U16

Sheep and Horse Grazing in a Large-Scale Protection Area and its Positive Impact on Chemical and Biological Soil Properties

This paper looks into the impact of free grazing by sheep and horses on the chemical and biological properties of soils in the partial protection zone of the Roztocze National Park. The study sampled three different types of pastureland in the area: pastures for sheep, horses and for combined grazing by sheep and horses. Compared to an ungrazed reference pasture, free grazing significantly stimulated the activity of enzymes which catalyze the transformation of organic matter (dehydrogenases, phosphatases and ureases) and it also positively influenced other chemical properties of the soils. Among the soils under free-grazing management, the pasture grazed to horses underwent the most advantageous changes in terms of the eco-chemical status of the soil

Anion-templated synthesis of a switchable fluorescent [2]catenane with sulfate sensing capability

Anion templation strategies have facilitated the synthesis of various catenane and rotaxane hosts capable of strong and selective binding of anions in competitive solvents. However, this approach has primarily relied on positively charged precursors, limiting the structural diversity and the range of potential applications of the anion-templated mechanically interlocked molecules. Here we demonstrate the synthesis of a rare electroneutral [2]catenane using a powerful, doubly charged sulfate template and a complementary diamidocarbazole-based hydrogen bonding precursor. Owing to the unique three-dimensional hydrogen bonding cavity and the embedded carbazole fluorophores, the resulting catenane receptor functions as a sensitive fluorescent turn-ON sensor for the highly hydrophilic sulfate, even in the presence of large excess of water. Importantly, the [2]catenane exhibits enhanced binding affinity and selectivity for sulfate over its parent macrocycle and other acyclic diamidocarbazole-based receptors. We demonstrate also, for the first time, that the co-conformation of the catenane may be controlled by reversible acid/base induced protonation and deprotonation of the sulfate anionic template. This approach pioneers a new strategy to induce molecular motion of interlocked components using switchable anionic templates

TEMPO-Appended Metal–Organic Frameworks as Highly Active, Selective, and Reusable Catalysts for Mild Aerobic Oxidation of Alcohols

Metal–organic frameworks (MOFs) decorated with stable organic radicals are highly promising materials for redox catalysis. Unfortunately however, the synthesis of chemically robust MOFs typically requires harsh solvothermal conditions, which are not compatible with organic radicals. Here, we describe the synthesis of two isoreticular families of stable, mixed component, zirconium MOFs with UiO-66 and UiO-67 structures and controlled amounts of covalently attached TEMPO radicals. The materials were obtained using a relatively low-temperature, HCl-modulated de novo method developed by Hupp and Farha and shown to contain large amounts of missing cluster defects, forming nanodomains of the reo phase with 8-connected clusters. In the extreme case of homoleptic UiO-67-TEMPO(100%), the material exists as an almost pure reo phase. Large voids due to missing clusters and linkers allowed these materials to accommodate up to 2 times more of bulky TEMPO substituents than theoretically predicted for the idealized structures and proved to be beneficial for catalytic activity. The TEMPO-appended MOFs were shown to be highly active and recyclable catalysts for selective aerobic oxidation of a broad range of primary and secondary alcohols under exceptionally mild conditions (room temperature, atmospheric pressure of air). The influence of various parameters, including the pore size and TEMPO content, on the catalytic activity was also comprehensively investigated

Transmembrane Anion Transport Promoted by Thioamides

Thioamide groups represent useful hydrogen-bonding motifs for the development of active transmembrane anion transporters. Using a 1,8-dithioamidocarbazole scaffold the superior performance of thioamides compared with the parent amides has been demonstrated.<br /

Preparation of Ruthenium Olefin Metathesis Catalysts Immobilized on MOF, SBA-15, and 13X for Probing Heterogeneous Boomerang Effect

Promoted by homogeneous Ru-benzylidene complexes, the olefin metathesis reaction is a powerful methodology for C-C double bonds formation that can find a number of applications in green chemical production. A set of heterogeneous olefin metathesis pre-catalysts composed of ammonium-tagged Ru-benzylidene complexes 4 (commercial FixCat&trade; catalyst) and 6 (in-house made) immobilized on solid supports such as 13X zeolite, metal-organic framework (MOF), and SBA-15 silica were obtained and tested in catalysis. These hybrid materials were doped with various amounts of ammonium-tagged styrene derivative 5&mdash;a precursor of a spare benzylidene ligand&mdash;in order to enhance pre-catalyst regeneration via the so-called release-return &ldquo;boomerang effect&rdquo;. Although this effect was for the first time observed inside the solid support, we discovered that non-doped systems gave better results in terms of the resulting turnover number (TON) values, and the most productive were hybrid catalysts composed of 4@MOF, 4@SBA-15, and 6@SBA-15

Transmembrane anion transport promoted by thioamides

Thioamide groups represent useful hydrogen-bonding motifs for the development of active transmembrane anion transporters. Using a 1,8-di(thioamido)carbazole scaffold the superior performance of thioamides compared with the parent amides has been demonstrated.Polish National Science Centre for grant OPUS (2011/01/B/ST5/03900) and Consejer´ıa de Educaci´on de la Junta de Castilla y Le´on (project BU067P20