Redox-configurable ambidextrous catalysis: structural and mechanistic insight.

A ligand capable of adopting two pseudo-enantiomeric helically chiral states when bound to copper has been applied as an asymmetric catalyst in the Michael addition of malonate substrates to nitrostyrenes. The absolute configuration of the helically chiral ligand is inverted upon oxidation/reduction of the copper center. In this way, the handedness of the Michael addition product (/) can be selected based on the handedness of the catalyst (Λ/Δ).

Tailored Polymeric Membranes for Mycobacterium Smegmatis Porin A (MspA) Based Biosensors.

Nanopores based on protein channels inserted into lipid membranes have paved the way towards a wide-range of inexpensive biosensors, especially for DNA sequencing. A key obstacle in using these biological ion channels as nanodevices is the poor stability of lipid bilayer membranes. Amphiphilic block copolymer membranes have emerged as a robust alternative to lipid membranes.

A redox-reconfigurable, ambidextrous asymmetric catalyst.

A redox-reconfigurable catalyst derived from L-methionine and incorporating catalytic urea groups has been synthesized. This copper complex catalyzes the enantioselective addition of diethyl malonate to trans-β-nitrostyrene. Either enantiomer of the product can be predetermined by selection of the oxidation state of the copper ion.

Redox-reconfigurable tripodal coordination complexes: stereodynamic molecular switches.

Ligand design principles based on acyclic conformational analysis, dynamic stereochemistry, and hard-soft ligand-metal coordination have led to the development of several redox-triggered chiroptical molecular switches. Factors controlling the helicity of copper(I) and copper(II) coordination complexes were explored and exploited to create a series of stereodynamic complexes that exhibit remarkable chiroptical properties. In some systems, strong circular dichroic signal could be modulated between on and off states, while in others, it was possible to invert the ellipticity by one-electron oxidation/reduction.

Structural and co-conformational effects of alkyne-derived subunits in charged donor-acceptor [2]catenanes.

Four donor-acceptor [2]catenanes with cyclobis(paraquat-p-phenylene) (CBPQT4+) as the pi-electron-accepting cyclophane and 1,5-dioxynaphthalene (DNP)-containing macrocyclic polyethers as pi-electron donor rings have been synthesized under mild conditions, employing Cu+-catalyzed Huisgen 1,3-dipolar cycloaddition and Cu2+-mediated Eglinton coupling in the final steps of their syntheses. Oligoether chains carrying terminal alkynes or azides were used as the key structural features in template-directed cyclizations of [2]pseudorotaxanes to give the [2]catenanes. Both reactions proceed well with precursors of appropriate oligoether chain lengths but fail when there are only three oxygen atoms in the oligoether chains between the DNP units and the reactive functional groups.

Cyclobis(paraquat-p-phenylene)-based [2]catenanes prepared by kinetically controlled reactions involving alkynes.

[reaction: see text] Charged donor-acceptor [2]catenanes, in which the pi-accepting cyclobis(paraquat-p-phenylene) acts as a tetracationic template for the threading-followed-by-clipping of acyclic oligoethers, incorporating centrally a pi-donating 1,5-dioxynaphthalene ring system and terminated either by acetylene units or by acetylene and azide functions, are the products of copper-mediated Eglinton coupling and Huisgen 1,3-dipolar cycloaddition, respectively.