James H. R. Tucker

Recent developments in the redox-switched binding of organic compounds

This review summarizes and puts into context recent advances in the field of redox-switched binding processes, with particular reference to the interaction between redox-active compounds and organic compounds, both charged and neutral. Simple homogeneous, two-component systems are discussed at first as a precursor to sections on more advanced systems (e.g. multi-component and multi-pole) and binding processes involving components attached to a surface.

Electrochemical method for the determination of enantiomeric excess of binol using redox-active boronic acids as chiral sensors

A chiral ferrocene-based boronic acid interacts with (R)- and (S)-Binol to form two complexes that exhibit significantly different ferrocene-based electrode potentials. This difference in redox behavior can be exploited to demonstrate in principle how high levels of enantiomeric excess in a mixture of enantiomers can be quantified and read-out using an electrochemical method.

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.

An Exploration of Ferrocenyl Ureas as Enantioselective Electrochemical Sensors for Chiral Carboxylate Anions

The syntheses of a series of chiral ureas containing the redox-active ferrocene group are described. Each of these bind chiral carboxylates in organic solvents through hydrogen-bonding interactions, as evidenced by spectroscopic and cyclic voltammetry measurements, the latter allowing these guests to be electrochemically sensed in solution. The enantioselectivity in the complexation of the protected amino acid N-benzenesulfonylproline by a ferrocenylbenzyl host is high enough to allow opposite enantiomers to be distinguished by electrochemical means.

Anion complexation via C–H⋯X interactions using a palladacyclic receptor

A novel organometallic receptor binds anions in solution and in the solid state, with complexes stabilised through a series of C-HX interactions, as evidenced by 1H NMR spectroscopy, X-ray crystallography and computational models.

Photoinduced formation of a cryptand from a coronand: an unexpected switch in cation binding affinity

Aza-crown ethers 2 and 3 with anthracene-containing pendant arms have been synthesised and characterised. Both compounds bind Group 1 metal cations in solution, forming complexes of 1:1 stoichiometry. The properties of compound 2 and its complexes have been studied by a range of techniques, including NMR, UV and fluorescence spectroscopy and X-ray crystallography. The pendant arms can adopt either a cis or a trans geometry, the cis geometry favoured with larger cations. The geometry of the complex affects the fluorescence properties of the system, with larger cations giving higher excimer/monomer ratios. Upon irradiation at lambda>300 nm, coronand 2 forms the cryptand 5 through a reversible intramolecular [4pi+4pi] cycloaddition reaction. The rates of the forward and reverse reactions of this photochromic process are cation dependent; in particular the rate of the thermal reverse reaction is decreased by smaller cations and increased by larger cations, especially Rb(+). The metal binding constants in methanol for 2 and 5 have been determined, revealing that the cryptand 5 binds Na(+) and Rb(+) more weakly than crown ether 2 by over two orders of magnitude.

Bis(amidopyridine)-linked calix 4 arenes: a novel type of receptor for dicarboxylic acids

Calix[4]arenes 1 and 2, functionalised on their upper rim with amidopyridine groups, have been synthesised. In the case of 1, a detailed binding study with a range of aliphatic and aromatic dicarboxylic acids has been carried out using H-1 NMR spectroscopy. The binding affinities are largely dependent upon the length of the alkyl spacer group, with the highest binding constant observed for dodecanedioic acid. The X-ray crystal structures of 1 and 2 reveal chain structures formed through intermolecular hydrogen bonds between amidopyridine moieties.

Novel electrochemical sensors for neutral molecules

Two new ferrocene receptors bind to a series of neutral carboxylic acid guests via hydrogen bonding interactions; complexation induces a significant change in the electronic properties of the proximate ferrocene units, as evidenced by the recognition of these neutral guests by cyclic voltammetry.

Organometallic nucleoside analogues with ferrocenyl linker groups: synthesis and cancer cell line studies

Examples of organometallic compounds as nucleoside analogues are rare within the field of medicinal bioorganometallic chemistry. We report on the synthesis and properties of two chiral ferrocene derivatives containing a nucleobase and a hydroxyalkyl group. These so-called ferronucleosides show promising anticancer activity, with cytostatic studies on five different cancer cell lines indicating that both functional groups are required for optimal activity.

The effect of d-block metal complexation on the spectroscopic and redox properties of ferrocene derivatives containing pyridine ligands

Three ferrocene derivatives 1-3, each containing two pyridine ligands, form complexes with a variety of d-block metals, as evidenced by NMR and UV-vis spectroscopy and cyclic voltammetry. The X-ray crystal structures of 1 and its Mo(0) complex are reported. The Zn(II) and Cu(I) complexes of 1-3 have a 2/1 (ligand/metal) stoichiometry. The factors influencing the changes in the redox and chromogenic properties of these ligands upon complexation are discussed.