Dioxygen binding to immobilized Co^II complexes in porous organic hosts: evidence for site isolation

Abstract

To model channel motifs and site isolation properties found in metalloproteins, a series of Co^II Schiff base complexes have been immobilized in porous organic hosts which stabilize Co–O₂ species at room temperature.

References

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12. The concentration of cobalt in P-1[Co(dmap)₂] ranges from 180 to 200 µmol g^–1 in samples prepared independently.
13. P-1[Co]: [Co]= 170 µmol g^–1; EPR parameters: g= 1.98 and a broad feature centered at g= 3.28. P-1[Cu]: EPR parameters: g_∥= 2.21; g_⊥= 2.04; A_∥= 202 G at 77 K.
14. EPR spectra recorded on samples of polymer suspended in toluene for 1 h after exposure to O₂.
15. X-Band EPR parameters for: P-1[Co(py)] at 77 K: g₁= 2.48; g₂= 2.26; g₃= 2.01; A₃= 99 G; a^N₃= 16 G; P-1[Co(py)(O₂)] at 77 K: g_∥= 2.08; g_⊥= 2.02; A_⊥= 16 G; P-1[Co(py)(O₂)] at 298 K: g_iso= 2.02.
16. Exposure of O₂ to P-1[Co(dmap)] results in an immediate color change (orange–brown to purple) and formation of P-1[Co(dmap)(O₂)] is completed in < 4 min (the concentration of dioxygen is saturating at ca. 0.009 M in toluene). Similar results were observed for P-1[Co(py)] and P-2[Co].
17. T. J. Kristenmacher, L. G. Marzilli and P. A. Marzilli, Inorg. Chem., 1974, 13, 2089.
18. P-2[Co] was synthesized by same procedure used for P-1[Co](Scheme 1) substituting 3,3′-diamino-N-methyldipropylamine for ethylenediamine.
19. The EPR spectrum of P-2[Co-O₂] obtained 125 h after initial O₂ exposure was identical to that measured after 40 h.
20. P-1[Co(py)] also reversibly binds O₂ at room temperature.