The solution structure of a lasalocid A metal complex in lipophilic solvents

Toxicity of the ionophore antibiotic lasalocid to soil-dwelling invertebrates: avoidance tests in comparison to classic sublethal tests

Lasalocid is a veterinary ionophore antibiotic used for prevention and treatment of coccidiosis in poultry. It enters the environment with the use of contaminated manure on agricultural land. Despite its extensive use, the effects of lasalocid on non-target soil organisms are poorly explored. We used classical subleathal ecotoxicity tests to assess the effects of lasalocid on earthworms (Eisenia andrei) and isopods (Porcellio scaber) and compared the results with tests using avoidance behaviour as the endpoint. The results showed that avoidance is a much more sensitive endpoint. For earthworms, EC50 for avoidance (12.3 mg kg(-1) dry soil) was more than five times lower than EC50 for reproduction (69.6 mg kg(-1) dry soil). In isopods the sensitivity of the behavioural response test was even higher. While the highest lasalocid concentration 202 mg kg(-1) had no significant effects on isopod growth or survival, already the lowest used concentration in the behavioural assay (4.51 mg kg(-1)) caused significant impact on isopod behaviour. Using the avoidance test results for calculating the predicted no-effect concentration (PNEC) of lasalocid to soil invertebrates, the value is close to the predicted environmental concentration (PEC). This indicates that the use of lasalocid-contaminated manure could potentially impair the habitat function of agricultural soils.

The structure of MLn(hfbc)4 and a key to high circularly polarized luminescence

The heterobimetallic complex CsEu[(+)-hfbc](4) (hfbc = 3-heptafluorobutyryl camphorate), prepared by Kaizaki and co-workers, displays the highest ratio of polarization versus total luminescence (measured by the g(lum) factor), i.e., ~85% of the emitted photons at 595 nm are left-circularly polarized. We present a detailed structural analysis in solution, based on paramagnetic nuclear magnetic resonance (NMR), and discuss the possible dynamic processes, where its analogues are involved. We demonstrate that the first coordination sphere is very close to the achiral regular square antiprism (SAPR) with D(4d) symmetry, which rules out the intrinsic dissymmetry of the Eu environment for rationalizing the g(lum). In contrast, the dynamic coupling between the f-f transitions, responsible for the emission, to the ligand-centered π-π* transition at 310 nm displays almost ideal geometry to justify g(lum) and discloses a key to high circularly polarized emission.

[Ln(binolam)3]·(OTf)3, a new class of propeller-shaped lanthanide(III) salt complexes as enantioselective catalysts: structure, dynamics and mechanistic insight

The ligand 3,3'-bis(diethylaminomethyl)-1,1'-bi-2-naphthol (binolam) contains an arrayed Brønsted acid-Brønsted base (BABB) system, which is responsible for the original shape of its lanthanide compounds. The solution structure of Pr, Nd and Yb compounds is solved by means of paramagnetic NMR spectroscopy and it is demonstrated that they are substantially isostructural, but with a completely new fold compared to the apparently similar heterobimetallic systems based on 1,1'-bis(2-naphthol) (binol) and alkali cations. The aromatic nuclei lie in a region equatorial with respect to the C(3) symmetry axis, whereas the alkylamine chain stretches almost parallel to C(3), above (and below) Ln(3+). This is also found in the crystal structure of the binolamo-scandium complex. A detailed study of the proton-exchange processes within the network of BABBs present in the complex is reported, which provides insight into the mechanism of the enantioselective Henry reaction promoted by these systems.