Noel R. Russell

Cyclic voltammetry of ferrocene carboxylic acid cyclodextrin inclusion complexes

Abstract The cyclic voltammetry of ferrocene carboxylic acid (FcA − ) was studied in the presence of α, β and γ cyclodextrin (CD). CD affects the magnitude of the peak currents and the position of the peak potentials of the ferrocene carboxylic acid system. A model was set up to simulate the effect of CDs on the electrochemistry of the above species, and also to characterise the formation of the inclusion complexes. Formation constants for the complexes were evaluated in aqueous solution by comparing simulated voltammograms and practical results. It is found that the use of peak potentials ( E f , E b ) rather than formal potentials of FcA − ( E 0 1 ′), and the FcA − CD complex ( E 0 2 ′), in the simulation is more valid in the evaluation of the formation constants. The ability of the CD isomers to form complexes was found to follow the order β > γ > α. A brief study of the interactions of ferrocene dicarboxylic acid with CDs showed no evidence of second sphere complex formation. It was found also that cyclodextrins enhanced the solubility of unsubstituted ferrocene in water.

FT-IR and raman spectra of a series of metallo-β-cyclodextrin complexes

A series of metallo-β-CD complexes were prepared and formulated as [M2(OH)2β-CD·2 H2O]n−. Changes in the FT-IR and Raman Spectra ofβ-CD on coordination may be taken as evidence for complexation and support for a hydroxy bridged binuclear structure. Further support was obtained from uv/visible and magnetic moment measurements.

FT-IR and raman spectral evidence for metal complex formation withβ-cyclodextrin as a first sphere ligand

Changes occurring in the FT-IR and Raman spectra ofβ-CD when complexed to Mn(III), in a compound formulated as Mn2(OH)2CD, may be taken as indicating the formation of a complex in whichβ-CD is acting simultaneously as a first and second sphere ligand.

Polynuclear hydroxy-bridged Structure in metallo-β-cyclodextrin complexes: A study of magnetic susceptibility versus temperature

Data of the variation of magnetic susceptibility with temperature were obtained by the Gouy balance method for a series of metallo-/β-CD complexes. The results support the proposal for the presence of polynuclear hydroxy-bridged structures with interacting paramagnetic centres giving rise to an antiferromagnetic character for these complexes. In the case of the Cu(II) complex estimates of the Cu-Cu distance and the Cu-O-Cu bond angle were obtained from the data.

Enantioselective Complexation of Amino Acids by 6A-Deoxy-6A-hydroxyethylamino-β-Cyclodextr in and its Metallo-Derivatives in Aqueous Solution

Enantioselectivity towards several amino acids by metallo-6A-deoxy-6A-hydroxyethyl-amino-β-cyclodextrins (metallo-βCDeas) was investigated by potentiometric titration of the various amino acid/metallo-βCDea systems with NaOH solution. It was shown that the cyclodextrin derivative is capable of distinguishing between enantiomers of amino acid species in the presence of certain metal ions (Co2+, Ni2+, Cu2+and Zn2+). Ni2+-βCDea complexes show the most enantioselectivity, whereas for Cu2+- and Co2+-βCDea complexes less selectivity is observed. As expected, Zn2+-βCDea complexes exhibit no enantioselectivity. Stability and selectivity, however, do not go hand in hand, since the most stable complexes are formed with Cu2+. Several factors play a role in determining stability and selectivity in binary and ternary complexes and further study is required to gain a more comprehensive understanding of these.

Luminescence quenching of the excited tris-bipyridyl ruthenium(II) ion by copper(II)-cyclodextrin complexes

The quenching of the luminescence intensity and lifetime of the electronically excited species Ru(bipy)32+ by a series of copper (II) cyclodextrin complexes is studied. It is found that conventional Stern-Volmer behaviour is not followed. A modified version of the Stern-Volmer equation, one which assumes purely static quenching, is in good agreement with experimental data. Inclusion of the Ru(bipy)32+ by the metallo-cyclodextrin complex is observed to play a key role in the quenching mechanism.

Preparation of a novel β-CD–dimanganese complex with covalently bound photosensitizer

The synthesis and structure of a novel donor–acceptor complex comprised of a photosensitising ruthenium polypyridyl moiety covalently linked to a β-cyclodextrin unit bearing a hydroxy-bridged manganese(III) dimer 1 is described; the dimanganese complex undergoes a photoinduced electron transfer and may represent an attractive model system for elucidating aspects of photosystem II.