Near-infrared chiro-optical effects in metallogels

A series of novel metallogelators containing near-IR nickel-bis(dithiolene) absorbers were rationally designed and synthesized. Robust gel networks are formed by right handed helical 1D-nanofibers which generate strong and remarkable chiro-optical effects in the near-infrared region.     

Synthesis and structure resolution of RbLaF4

The synthesis and structure resolution of RbLaF(4) are described. RbLaF(4) is synthesized by solid-state reaction between RbF and LaF(3) at 425 °C under a nonoxidizing atmosphere. Its crystal structure has been resolved by combining neutron and synchrotron powder diffraction data refinements (Pnma,a = 6.46281(2) ?, b = 3.86498(1) ?, c = 16.17629(4) ?, Z = 4). One-dimensional (87)Rb, (139)La, and (19)F MAS NMR spectra have been recorded and are in agreement with the proposed structural model. Assignment of the (19)F resonances is performed on the basis of both (19)F-(139)La J-coupling multiplet patterns observed in a heteronuclear DQ-filtered J-resolved spectrum and (19)F-(87)Rb HMQC MAS experiments. DFT calculations of both the (19)F isotropic chemical shieldings and the (87)Rb, (139)La electric field gradient tensors using the GIPAW and PAW methods implemented in the CASTEP code are in good agreement with the experimental values and support the proposed structural model. Finally, the conductivity of RbLaF(4) and luminescence properties of Eu-doped LaRbF(4) are investigated.     

Optimized Liebeskind–Srogl coupling reaction between dihydropyrimidines and tributyltin compounds

We developed an optimized Liebeskind–Srogl reaction in order to synthesize potentially biologically active 2-aryl-1,4-dihydropyrimidines. The pallado-catalyzed cross-coupling reaction between dihydropyrimidines and tributyltin derivatives appears particularly efficient (67–95% yields) when using CuBr·Me₂S as the copper cofactor.     

Effects of DNA on the growth and optical properties of luminescent organic microcrystals

The reprecipitation method, which is a solvent-exchange process, was used to prepare free-standing microcrystals from an organic fluorescent dye, 4-n-octylamino-7-nitrobenz-2-oxa-1,3-diazole. Calf thymus DNA was introduced as an additive into the reprecipitation medium, strongly accelerating the process. The reprecipitation kinetics was monitored by UV/vis absorption spectroscopy, and the analysis of the rate constants allowed the role played by the additive to be clarified. DNA was also found to affect the shape and size of the dye microcrystals obtained. In particular, its presence induced the formation of a new type of microcrystal that displays original two-color fluorescence. The emission properties were first analyzed on the suspensions, using a traditional fluorimeter, and then on individual microcrystals by means of a space- and time-correlated photon-counting photomutiplier installed on a microscope. The study on single microcrystals suggests that the dual coloration observed originates from the reabsorption of the blue component of the emitted light, whereas the remaining red component propagates through the microcrystal body and is scattered by the edges. However, the color of the other types of microcrystals can be explained only by specific arrangements of molecules at the surface of the crystal.     

Through-bond homonuclear correlation experiments in solid-state NMR applied to quadrupolar nuclei in Al-O-P-O-Al chains

Through-bond homonuclear correlation experiments can be realised in solids between spins of type X, separated by four chemical bonds, in X-O-Y-O-X motifs, provided a J coupling between X and Y exists: central transitions of quadrupolar 27Al spins can be correlated via the J2 scalar coupling between 27Al (X) and 31P (Y) in materials featuring Al-O-P-O-Al motifs.     

An EXAFS study of the formation of a nanoporous metal-organic framework: evidence for the retention of secondary building units during synthesis

EXAFS data measured from amorphous intermediates and crystallisation solutions provides the first evidence that trimeric iron oxide secondary building units remain intact during crystallisation of the metal-organic framework MIL-89 from starting materials to products.     

Microalga Chlorella sorokiniana: a new sulfoxidation biocatalyst

Whole cells of the microalga Chlorella sorokiniana were evaluated in the oxidation of prochiral thioethers as regards conversion, enantiomeric excess and enantioselectivity.     

Acetogenins in Annona muricata L. (annonaceae) leaves are potent molluscicides

An ethanolic extract of the leaves of Annona muricata was shown to be toxic to adult forms of the snail Biomphalaria glabrata (LC50 9.32 microg mL(-1)) and to larvae of the brine shrimp Artemia salina (LC50 0.49 microg mL(-1)). Activity-guided fractionation of the extract gave rise to a sample with high molluscicidal activity that contained the acetogenins, annonacin (90%), isoannonacin (6%) and goniothalamicin (4%).     

Versatile precursors of functional RAFT agents. Application to the synthesis of bio-related end-functionalized polymers

Biomolecule-polymer conjugates are widely used in bio-related fields, but their synthesis is often tricky, especially the introduction of a single biomolecule at one chain end. This paper describes a new straightforward approach to prepare such conjugates via RAFT polymerization. By designing appropriate bio-related RAFT agents, polymer chains of controlled chain length (Mn = 10 000-40 000 and PDI < 1.1) carrying a single biomolecule as an alpha-end group (a sugar or a biotin) linked by a stable amide bond are obtained. Considering the versatility of the RAFT process, this strategy appears to be very attractive for the design of a variety of conjugates.     

An easy route towards regioselectively difunctionalized cyclens and new cryptands

Reductive amination of various aldehydes with cyclen represents a very convenient method for the synthesis of a wide range of 1,7-difunctionalized cyclens, as well as new cryptands.