Synthetic ion channels and pores attract current attention as multicomponent sensors in complex matrixes. This application requires the availability of reactive signal amplifiers that covalently capture analytes and drag them into the pore. pi-Basic 1,5-dialkoxynaphthalenes (1,5-DAN) are attractive amplifiers because aromatic electron donor-acceptor (AEDA) interactions account for their recognition within pi-acidic naphthalenediimide (NDI) rich synthetic pores. Focusing on amplifier design, we report here the synthesis of a complete collection of DAN and dialkoxyanthracene amplifiers, determine their oxidation potentials by cyclic voltammetry, and calculate their quadrupole moments. Blockage experiments reveal that subtle structural changes in regioisomeric DAN amplifiers can be registered within NDI pores. Frontier orbital overlap in AEDA complexes, oxidation potentials, and, to a lesser extent, quadrupole moments are shown to contribute to isomer recognition by synthetic pores. Particularly important with regard to practical applications of synthetic pores as multianalyte sensors, we further demonstrate that application of the lessons learned with DAN regioisomers to the expansion to dialkoxyanthracenes provides access to privileged amplifiers with submicromolar activity.

Not a cop out: The copper-catalyzed asymmetric conjugate addition of organometallic reagents to Michael acceptors is an important methodology for forming a CC bond in an enantioselective manner. Such an addition of Me3Al to β,γ-unsaturated α-ketoesters is described to proceed in high yield and selectivity. CuTC=copper(I) thiophene-2-carboxylate

Dedicated to Professor Andre Merbach on the occasion of his 65th birthday Complexes [ML 3 ] 2 of the bidentate ligand 2-(1H-imidazol-2-yl)pyridine were prepared with iron(II), cobalt(II), and ruthenium(II). The electronic spectra suggest the ligand to be a weaker s-donor and p-acceptor than the closely related 2,2'-bipyridine. The complexes are readily deprotonated by addition of base, and the effect of the deprotonation is to lower the M III /M II redox potential by roughly 900 mV. This is roughly 75% of the drop observed for related complexes of 2,6-di-1H-imidazol-2-ylpyridine, and suggests the effect to be largely coulombic in origin.Introduction. ± Although 1H-imidazole is easily the most important N-containing ligand in biological systems, 1H-imidazole-containing ligands have been much less studied in abiotic coordination chemistry than the related pyridine ligands. However, 1H-imidazole is naturally a bifunctional ligand, possessing a pyrrolic N-atom in addition to the pyridinic N-atom, which acts as a donor to transition metals. This NH functionality is available for H-bonding, and may also be deprotonated. The H-bonding property has been intensively studied in connection with metalloporphyrins [1], and Hbonding of 1H-imidazole coordinated to an iron porphyrin has been shown to shift the redox potential of the metal center by some 60 mV [2], stabilizing the iron(III) oxidation state. Coordination of 1H-imidazole significantly lowers the pK a value of the pyrrolic H-atom [3 ± 7] by ca. 5 ± 7 log units, allowing deprotonation to occur in weakly basic solution (pH 8 ± 10). The resulting imidazolate can act as a bridging ligand, as is well known in superoxide dismutase [8] and in many synthetic systems [9 ± 12]. A less explicitly studied effect of deprotonation is the change in the metal redox potential. We have shown recently [13] [14] that the ligand 2,6-di-1H-imidazol-2-ylpyridine (1) forms stable complexes [M (1) 2 ] 2 with a number of transition metals, and that these complexes are readily deprotonated in basic solution. For M Co, Fe, and Ru, the potential of the M

The chemistry of the ligand 1, 2,6-bis(imidazol-2-yl)pyridine with manganese, cobalt, nickel and ruthenium has been investigated. The ligand binds as a meridional tridentate ligand as shown by the crystal structures of [Mn(1)2](CF3SO3)2 x Et2O and [Ru(1)2](PF6)2 x 2CH3CN x H2O. The coordinated ligand is deprotonated in mildly basic solution, and this leads to a drop in the metal M(III)/M(II) reduction potential for cobalt and ruthenium of roughly 1.3 V. The crystal structure of Na2(PPN)[Co(1 - 2H)2]2(OH) x MeOH x 2H2O confirms the deprotonation and shows sodium to bind to the deprotonated nitrogen atoms. No stabilisation of the M(III) oxidation state was observed for nickel and manganese.