Chromo- and Fluorogenic Organometallic Sensors

Compounds that change their absorption and/or emission properties in the presence of a target ion or molecule have been studied for many years as the basis for optical sensing. Within this group of compounds, a variety of organometallic complexes have been proposed for the detection of a wide range of analytes such as cations (including H+), anions, gases (e.g. O 2, SO2, organic vapours), small organic molecules, and large biomolecules (e.g. proteins, DNA). This chapter focuses on work reported within the last few years in the area of organometallic sensors. Some of the most extensively studied systems incorporate metal moieties with intense long-lived metal-to-ligand charge transfer (MLCT) excited states as the reporter or indicator unit, such as fac-tricarbonyl Re(I) complexes, cyclometallated Ir(III) species, and diimine Ru(II) or Os(II) derivatives. Other commonly used organometallic sensors are based on Pt-alkynyls and ferrocene fragments. To these reporters, an appropriate recognition or analyte-binding unit is usually attached so that a detectable modification on the colour and/or the emission of the complex occurs upon binding of the analyte. Examples of recognition sites include macrocycles for the binding of cations, H-bonding units selective to specific anions, and DNA intercalating fragments. A different approach is used for the detection of some gases or vapours, where the sensor's response is associated with changes in the crystal packing of the complex on absorption of the gas, or to direct coordination of the analyte to the metal centre

Metal-directed self-assembly of terphenyl based dithiocarbamate ligands

The synthesis of dithiocarbamate ligands based on an m-terphenyl scaffold is reported. These ligands self-assemble with zinc(II), nickel(II) and copper(II) ions to afford neutral, dinuclear metallomacrocycles in varied yields. The assemblies have been characterised by a range of techniques, including 1H NMR,13C NMR and UV-vis spectroscopy, elemental analysis, mass spectrometry and cyclic voltammetry. Intramolecular coordination of bipyridyl guests has been investigated with the zinc(II) containing macrocycles. NMR spectroscopy and FAB mass spectrometry demonstrate the formation of 1 : 1 inclusion complexes with 4,4′-bipyridyl

Anion selectivity properties of ruthenium(II) tris(5,5 '-diamide-2,2 '-bipyridine) receptors dictated by solvent and amide substituent

The ratio of the dichloromethane-methanol solvent mixture medium and nature of the receptor amide substituent critically dictates chloride vs. nitrate selectivity properties of new ruthenium(II) tris(5,5′-diamide-2,2′-bipyridine) receptors

Ion pair cooperative binding of potassium salts by new rhenium(I) bipyridine crown ether receptors.

The new rhenium(I) bipyridine crown ether receptors 1-4 have been prepared and their ion pair recognition properties examined. The crystal structure of [1.KCl](2).2H(2)O demonstrates that potassium is coordinated by benzo-18-crown-6 and chloride is hydrogen bonded to the amide groups. Receptor 3 extracts solid KCl and KOAc into chloroform via ion pair complexation. NMR and emission titration studies with receptors 1-4 and KCl/KOAc show that cobound potassium enhances anion binding strength by electrostatic and conformational effects. Significant cooperative interactions are observed between the anion and cation sites for host 4 in CH(3)CN. This molecule coordinates potassium to form a 1:1 intramolecular sandwich complex, which preorganizes the host for acetate binding