EPR Characterisation of Bis(dimethylglyoximato)-Cobalt(II) Complexes and Their Oxygen Adducts Synthesised in an X-Zeolite Matrix

Abstract

The synthesis o f bis(dim ethylglyoxim ato)-cobalt(II) (C oH(dm gH )2) in the a-cages o f a cobalt-exchang ed sodium X-zeolite is described. A sim ple hydration/oxygenation sequence culm inating in a superoxo com plex, C oni(dm gH )2-H 20 -0^ has been studied using X-band EPR spectroscopy. The identification o f the precursor species: square-planar C on (dm gH )2, distorted C o H(dm gH )2 and C o M (dm gH)2-2 H20 was aided by com parison o f their g-and 59C o hyperfine tensor principal values with those o f model com plexes. On the basis o f this identification the reaction sequence is discussed.

Probing the surrounding of a cobalt(II) porphyrin and its superoxo complex by EPR techniques

“…EPR spectra were simulated with a computer program on the basis of a spin Hamiltonian, containing the electronic Zeeman and metal hf interaction [52,53]:…”

“…Convenient expressions relating the principal values of the g and 59Co hf tensors to 3d and 4s spin densities, and the energies of the low-lying doublet and quartet excited states for the more general (C2 ) case, have been described previously [53]. The C 4" case is simpler; in terms of the notation of ref.…”

“…To circumvent the first of these difficulties, we have already described a successful alternative [53] embodying a more rigorous assessment of the 3d 22 and 4s polarization. This approach is now elaborated upon, with a view to tackling the two remaining difficulties.…”

“…The zero-order energy of this state, relative to 2 B, may be related to AE" and AE v [53,65], the corresponding energies of the simpler doublet excitations, la -lb and lb -2a, respectively:…”

Molecular sieve encapsulated organic dyes and metal chelates

“…"~] The photoreactivity of the isomerization of azanaphthylene is influenced by the kind of metal ion in zeolite. [' 31 Zeolites containing small cations like Lie and Nae influence the behavior of guests due to their high charge density/electrostatic potential. The interaction of small cations with polar groups like the carbonyl group in ketones enhances the triplet lifetime and favors a regioselective Norrish type process.…”