Hybrid polyoxometalate materials for photo(electro-) chemical applications

A variety of functional nanostructured organic/inorganic hybrid materials from the europium-exchanged derivative of a Preyssler-type polyoxometalate (POM), [EuP5W30O110]12−, and functional organic surfactants were prepared by the ionic self-assembly (ISA) route. The effect of organic surfactants on the structure, photoluminescent, electrochemical and electrochromic properties of the POM anions was investigated in detail. All obtained hybrid materials are amphotropic, i.e., exhibit both thermotropic and lyotropic liquid-crystalline phase behaviour. Investigations of their photophysical properties have shown that the interactions of the various surfactants with the polyanions influence the coordination environments and site symmetry of Eu3+ in different ways. The functional groups in the organic surfactants significantly influence the electrochromic properties and photoluminescence of POMs. Different from normal and pyridine-containing complexes, no photoluminescence and no electrochromism were observed from the ferrocene-containing complexes. This may be explained in view of charge transfer between the POM anion and the ferrocenyl group.

Organized Nanostructured Complexes of Polyoxometalates and Surfactants that Exhibit Photoluminescence and Electrochromism

A series of metal bis-mnt complexes (mnt = 1,2-dithiolatomaleonitrile) with the trimethylammonium methylferrocene cation have been synthesized and characterized using X-ray diffraction, magnetic su...

Structural and Magnetic Properties of M(mnt)(2) Salts (M = Ni, Pt, Cu) with a Ferrocene-Based Cation, [FcCH(2)N(CH(3))(3)](+). Interplay between M.M and M.S Intermolecular Interactions.

Transient 1:1 precursor complexes for intermolecular self-exchange between various organic electron donors (D) and their paramagnetic cation radicals (D+*), as well as between different electron acceptors (A) paired with their anion radicals (A-*), are spectrally (UV-NIR) observed and structurally (X-ray) identified as the cofacial (pi-stacked) associates [D, D+*] and [A-*, A], respectively. Mulliken-Hush (two-state) analysis of their diagnostic intervalence bands affords the electronic coupling elements (HDA), which together with the Marcus reorganization energies (lambda) from the NIR spectral data are confirmed by molecular-orbital computations. The HDA values are found to be a sensitive function of the bulky substituents surrounding the redox centers. As a result, the steric modulation of the donor/acceptor separation (rDA) leads to distinctive electron-transfer rates between sterically hindered donors/acceptors and their more open (unsubstituted) parents. The latter is discussed in the context of a continuous series of outer- and inner-sphere mechanisms for organic electron-transfer processes in a manner originally formulated by Taube and co-workers for inorganic (coordination) donor/acceptor dyads-with conciliatory attention paid to traditional organic versus inorganic concepts.

Continuum of outer-and inner-sphere mechanisms for organic electron transfer. steric modulation of the precursor complex in paramagnetic (ion-radical) self-exchanges

Patrick L. Veya

Papers

Structural and spectral characterization of novel charge-transfer salts of polyoxometalates and the cationic ferrocenyl donor