Supramolecular Light-Harvesting Antennas of Metal-Coordinated Bis(8-Hydroxyquinoline)-Substituted Porphyrin Networks.

Artificial antenna complexes of metal-coordinated bis(8-hydroxyquinoline)-substituted porphyrin networks that mimic antenna chromophores in plants were organized on titanium dioxide electrodes in photoelectrochemical cells. The generated photocurrents can be optimized according to the two ways of porphyrin self-assembly due to the "antenna effect": changing the number of assembled porphyrin monolayers and the number of generations of the metal-coordinated porphyrin networks.

Strapped and other topographically nonplanar calixpyrrole analogues. Improved anion receptors.

Calixpyrroles and related macrocycles are non-aromatic synthetic anion receptors that have attracted considerable attention in recent years. The unfunctionalized, parent calix[4]pyrrole system, also known as octamethylporphyrinogen, may be prepared in one step and in high yield from pyrrole and acetone, and is an effective anion receptor, showing a preference for fluoride, phosphate, carboxylate and chloride anions in organic media. Efforts to improve the anion binding affinity of calix[4]pyrrole and to modify its inherent selectivity have led to the synthesis of a variety of new, modified calixpyrroles. Among the most effective of these are derivatives that contain bridging "straps". In this Feature Article, the preparation and properties of these and other topographically nonplanar calixpyrrole analogues are reviewed from the perspective of the anion recognition chemist.

Highly cooperative ion-pair recognition of potassium cyanide using a heteroditopic ferrocene-based crown ether-trifluoroacetylcarboxanilide receptor.

A heteroditopic receptor having crown ether and trifluoroacetylcarboxanilide groups selectively recognizes both potassium and cyanide ions in acetonitrile with an association constant of as high as Ka = 1.9 x 10(7) M(-1) through a highly cooperative ion-pair interaction, resulting in two orders of magnitude enhancement in the binding affinity.

Selective recognition and electrochemical sensing of dicarboxylates with a ferrocene-based bis(o-trifluoroacetylcarboxanilide) receptor.

A ferrocene-based bis(o-trifluoroacetylcarboxanilide) receptor selectively recognizes m-phenylene diacetate through cooperative binding; the receptor also displays a significant negative shift in the oxidation potential of ferrocene upon the guest binding.

Selective electrochemical sensing of acidic organic molecules via a novel guest-to-host proton transfer reaction.

Ferrocene-containing amidopyridine receptors bind carboxylic acids and the amino acid phenylalanine in acetonitrile via a novel proton transfer process that enables guests to be electrochemically sensed by positive shifts in the ferrocene-centred redox potentials.

Asymmetric synthesis of chiral alpha-ferrocenylalkylamines and their use in the preparation of chiral redox-active receptors.

A new strategy for the asymmetric synthesis of chiral primary alpha-ferrocenylalkylamines has been utilized to generate homochiral redox-active receptors that bind chiral carboxylate anions with moderate enantioselectivity and undergo a redox response to complexation. [structure: see text]

A ditopic ferrocene receptor for anions and cations that functions as a chromogenic molecular switch.

A ferrocene-based ditopic receptor containing a urea and a benzocrown ether unit shows a remarkable colour switching (ON-and-OFF) function induced by anion and cation recognition.

Cis- and trans-strapped calix[4]pyrroles bearing phthalamide linkers: synthesis and anion-binding properties.

[reaction: see text] New cis-strapped calix[4]pyrrole derivatives 12, 13, and 19 and trans-strapped systems 14 and 15 bearing isophthalate-derived diamide spacers linked to the tetrapyrrolic core have been synthesized and characterized by spectroscopic means. The anion-binding behavior of these receptors was investigated by proton NMR spectroscopy and isothermal titration calorimetry (ITC). A 2:1 binding stoichiometry was observed under the conditions of NMR analysis but not at the lower concentration regime used for ITC. As gauged from both sets of analyses, these new strapped systems display affinities for halide anions that are enhanced compared to those of normal, unstrapped calix[4]pyrrole. However, contrary to expectations, no size-dependent selectivity for anions is observed as the length of the bridging strap is varied. Such results are interpreted in terms of anion-binding processes that occur outside the central pocket defined by the strap but that still favor strong associations as the result of the increased number of hydrogen-bonding donors the amide groups provide.

Coumarin-strapped calix[4]pyrrole: a fluorogenic anion receptor modulated by cation and anion binding.

A new strapped calix[4]pyrrole containing a fluorophore as part of the strap has been synthesized and characterized. Association constants with various anions have been determined using both fluorescence titration and isothermal titrations calorimetry (ITC). The two sets of association constants were found to be in good agreement with one another. The fluorescence emission properties of this new receptor could be controlled by addition of Na+ (or H2O) and anions. However, the fluorescence quenching by anions is only observed in the presence of Na+ (or H2O). All the experimental evidence is consistent with the notion that independent PET processes are modulated by separate cation and anion recognition events. As such, this system operates as an elementary logic gate wherein anion and cation concentrations serve as the input and fluorescence intensity changes provide the output.

A heterodifunctionalised ferrocene derivative that self-assembles in solution through complementary hydrogen-bonding interactions.

A heterodifunctionalised ferrocene, containing a carboxylic acid and an amidopyridine unit, self-assembles in organic solvents through complementary hydrogen bonds.