Optical and electron spin resonance studies of copper(II), nickel(II) and oxovanadium(IV) complexes of water-soluble phthalocyanine and porphyrazine chelates absorbed on sephadex resins, and the effect of added dithionite

Abstract

Electronic and e.s.r. spectral data show that the solute-solute interactions which prevail in aqueous solutions containing copper(I1) and oxovanadium(1v) chelates of tetrasulphophthalocyanines persist when the chelates are absorbed onto the anion exchanger Sephadex DEAE. The distribution of the copper(r1) and oxovanadium(1v) into polymeric, dimeric and monomeric species may be adjusted by equilibration of the resin with aqueous solutions containing various amounts of dimethylformamide, which when present in high proportions effects a distribution largely of the monomeric forms. The tetracationic copper(II), cobalt(@ and oxovanadium(1v) tetra-N-methyl-2,3-tetrapyridinoporphyrazine chelates, which are free of solute-solute interactions in aqueous solutions, are absorbed in a monomeric distribution on the cation sites of the cation exchanger Sephadex CM. A two-electron reduction of the copper(I1) and oxovanadium(1v) tetrasulphophthalocyanine chelates occurs in their aqueous solution and while absorbed on the resin as a result of reaction with an aqueous solution of dithionite, whereafter the vanadyl complex has a gll value of 2.024. Reduction occurs by electron addition to the macrocyclic ring system.

Spectroscopic Signature and Structure of Active Centers in Ziegler-Natta Polymerization Catalysts revealed by Electron Paramagnetic Resonance

“…Three mean sets of principal g values contributing to the 340-390 mT band are g1 = [1.8167 1.8657 1.9156], g2 = [1.8910 1.9402 1.9621], g3 = [1.9642 1.9716 1.9902]. They are consistent with previously estimated g tensor parameters for the three different conformations of TiCl3 on the different MgCl2 surfaces (26).…”

Spectroscopic Signature and Structure of Active Sites in Ziegler-Natta Polymerization Catalysts revealed by Electron Paramagnetic Resonance

“…On the other hand, the large g anisotropy makes assignment to an organic radical very unlikely. The g tensor with unexpectedly large principal values is reminiscent of a previous observation for the 3d 1 3,10,17,24tetrasulphonatophthalocyanin (tspc) complex of V(IV)O, in particular, with its g|| > ge (27), which indicates that the g > ge values for d 1 species are indeed possible (see also SM g tensor calculations). This, together with the large anisotropy, led us to attribute the observed species to a Ti(III) complex with a distinct electronic structure rather than to an organic radical.…”

“…The unexpectedly large experimental g values are reminiscent to an observation by Skorobogaty et al for the 3,10,17,24-tetrasulphonatophthalocyanin (tspc) complex of V(IV)O in a water/DMF solution after two-electron reduction of the macrocycle (26). These authors also observed shifts in the g values when substituting DMF by pyridine, with g|| still being unusually large for a V(IV)O species, and a change to g values common for V(IV)O and g^ > g|| when the complex was adsorbed on a Sephadex column.…”

Spectroscopic Signature and Structure of Active Sites in Ziegler-Natta Polymerization Catalysts revealed by Electron Paramagnetic Resonance

“…These spectra reveal two paramagnetic species, characterized by a broad line around 340-390 mT and a narrower line at 320-340 mT that corresponds to an axially symmetric species. A species with a signal very similar to the 340-390 mT band has been observed before and has been assigned to Ti(III) surface species on MgCl2(110) (26). Only the 320-340 mT band grows with increasing amount of added BCl3, but is already present as a weak signal without addition of BCl3 (see Fig.…”

“…This, together with the large anisotropy, led us to attribute the observed species to a Ti(III) complex with a distinct electronic structure rather than to an organic radical. A similar species can be recognized as a weak contribution to Q-band EPR spectra that were obtained in previous work on catalysts that were not activated by BCl3 (26), but this species has not been further discussed. We found that it was strongly suppressed in 35.7 GHz pulse EPR echo-detected spectra (Fig.…”