Karl J. Wallace

Oxo-anion binding by metal containing molecular 'clefts'

Abstract A simple but effective route has been developed to produce a series of molecular clefts, [(η6-p-cymene)RuCl(1)2]PF6 (4a), [(dppe)Pd(1)2](BF4)2 (5a), [(dppe)Pd(2)2](BF4)2 (5b), [(dppe)Pt(1)2](BF4)2 (6a) and [(dppe)Pt(2)2](BF4)2 (6b), that contain either a redox active ferrocenyl or a photoactive anthracenyl side arm, attached to a ruthenium(II), palladium(II) or platinum(II) backbone. Compounds 4a, 5a, 5b and 6a act as hosts for oxo-anions. Anion recognition is achieved via convergent hydrogen bond interactions from secondary amine functionality on the side arms. The binding is also enhanced by the positive charge of the metal centres. The X-ray crystal structure of the related [PdCl2(1)2] (7) shows it to possess a trans geometry. The X-ray crystal structures of the monoadducts [(η6-p-cymene)RuCl2(1)] (3a) and [(η6-p-cymene)RuCl2(2)] (3b), which show contrasting behaviour in their hydrogen bonding to coordinated chloride, are also reported.

A lanthanide-based chemosensor for bioavailable Fe3+ using a fluorescent siderophore: an assay displacement approach.

The measurement of trace analytes in aqueous systems has become increasingly important for understanding ocean primary productivity. In oceanography, iron (Fe) is a key element in regulating ocean productivity, microplankton assemblages and has been identified as a causative element in the development of some harmful algal blooms. The chemosenor developed in this study is based on an indicator displacement approach that utilizes time-resolved fluorescence and fluorescence resonance energy transfer as the sensing mechanism to achieve detection of Fe3+ ions as low as 5 nM. This novel approach holds promise for the development of photoactive chemosensors for ocean deployment.

Molecular dyes used for the detection of biological and environmental heavy metals: Highlights from 2004 to 2008

The coordination chemistry of heavy metals, for example, Fe3 + , Pb2 + , Cd2 + , Hg2 + , Cu2 + and Zn2 + , is of interest, in part because of their hazards and toxicity in biological, industrial and agricultural applications. Additionally, there is much interest in the detection and quantification of trace metals in the products of chemical synthesis, in particular sensors for detecting Pd2 + . There has been plethora of new molecular sensors for the detection of heavy metals, which utilise colorimetric or fluorescence mechanisms. This mini-review covers recent advances (2004–2008) in the development of molecular sensors that is restricted to molecular dyes. Other methods for the detection of heavy metals, for example, conjugated polymers and gold nanoparticles are omitted.

An activated coumarin-enamine Michael acceptor for CN−

Two coumarin-enamine chemodosimeters have been synthesized in three steps. They have been shown to selectively detect the cyanide ion with a fluorescent response (t1/2 = 20 s) and a limit of detection approximately 4.2 ppb in DMSO. The X-ray crystal structure of the thermodynamically stable E-(keto) enamine isomer of one compound was obtained and exhibited offset π-stacking.

Conformational and configurational analysis of an N,N carbonyl dipyrrinone-derived oximate and nitrone by NMR and quantum chemical calculations.

The geometries and relative energies of new N,N carbonyl dipyrrinone‐derived oxime molecules (E/Z‐s‐cis 4a and E/Z‐s‐cis 4b) have been investigated. The calculated energies, molecular geometries, and 1H/13C NMR chemical shifts agree with experimental data, and the results are presented herein. The E‐s‐cis conformations of 4a and 4b and the Z‐s‐cis conformation of 5b were found to be the thermodynamically most stable isomers with the oxime hydrogen atom or the methyl functional group adopting an anti‐orientation with respect to the dipyrrinone group. This conformation was unambiguously supported by a number of 2D NMR experiments. Copyright

Chemodosimeters and Chemoreactands For Sensing Ferric Ions

Abstract The role of iron (+2 and +3 oxidation states) in biological and medical applications and the environment is pivotal. Supramolecular analytical approaches to monitor and remediate iron, in particular, ferric ions (Fe3+) are an area of interest. The development of fluorescence chemosensors using supramolecular chemistry seems to have exponentially grown since the beginning of the twenty-first century. This article will focus on the chemodosimeter and chemoreactand approach which have been developed to target ferric ions. This review will focus on two broad areas; the first section will discuss the ‘traditional’ approach, i.e. small molecule recognition, in organic, mixed organic-aqueous and buffer-aqueous solutions. The second section will highlight the molecular sensors that have been either doped or attached to surfaces to prepare nano-chemical sensors.

Binding of Mono- and Dianions within Silver Thiazolylurea Tweezers and Capsules

A silver thiazolylurea complex, [Ag(TUTh)2]+, has been used as a host species for geometrically differently shaped mono- and dianions: trigonal planar (NO3-), tetrahedral (SO42-), and octahedral (SiF62-). In the presence of nitrate a 1:1 near-planar tweezer host-guest species is formed, with poor binding in solution despite excellent geometric complementarity being found between the host and the anion in the solid state. In the presence of either SO42- or SiF62- a 2:1 host-guest species is formed, whereby the guest is held in a capsulelike arrangement stabilized by an array of eight NH hydrogen-bond donors, as confirmed by X-ray crystallographic studies. Solution studies in DMSO-d6 support the host-guest stoichiometry seen in the solid state. The binding constant between SO42- and [Ag(TUTh)2]+ was calculated to be K21 = 2511 M-2 and was shown to be the dominant species in solution, in excellent agreement with the solid-state studies. However, upon the addition of SiF62- ions different speciation is observed: H2·G (capsule), H·G (tweezer), and H·G2 during the course of the study.

Crystal structure of di­aqua­bis­(7-di­ethyl­amino-3-formyl-2-oxo-2H-chromen-4-olato-κ2O3,O4)zinc(II) dimethyl sulfoxide disolvate

A near-perfect octahedral zinc(II) complex coordinated to two coumarin fluorophores.