Biomimetic copper catalysts

Zhang T, Wang C, Liu S, WangJL, Lin W. A biomimetic copper water oxidation catalyst with low overpotential. J Am Chem Soc. 2014 136 273-281. 

While only tyrosinase catalyzes the ortho-hydroxylation of phenol moieties, both tyrosinase and catechol oxidase mediate the subsequent oxidation of the resulting catechols to the corresponding quinones. Various mono- and dinu-clear copper coordination compounds have been investigated as biomimetic catalysts for catechol oxidation [21,194], in most cases using 3,5-di-tert-butylcatechol (DTBC) as the substrate (Eq. 16). The low redox potential of DTBC makes it easy to oxidize, and its bulky tert-butyl groups prevent un-... 

Sotomayor, M. D. P. T. Tanaka, A. A. Kubota, L. T., Development of an amperometric sensor for phenol compounds using a Nafion (R) membrane doped with copper dipyridyl complex as a biomimetic catalyst,./. Electroanal. Chem. 2002, 536, 71-81... 

The last example to be mentioned deals with the application of coordination compounds attached to polymers and their use as immobilized catalysts. This technique has been used for a long time in organometallic catalysis. Similar reactions with biomimetic catalysts, as with Cu(II) oxidases, are less well known, and a review for polymeric copper imidazole complexes used in oxidative phenol coupling is available. 

Diphenylglycoluryl receptors were developed in Nolte s group to design supramolecular biomimetic catalysts. Two bis(pyrazolylamine)copper sites were grafted onto the receptor, which is known to bind 1,3-diphenols (Figure 11). The system, tested in benzyl alcohol oxidation, displayed a massive increase (up to four orders of magnitude) of... 

In a study, Cacciapaglia et al. (2006) successfully synthesized a pseudo-biomimetic catalyst that worked as a phosphodiesterase enzyme [37]. For that purpose, 1,2-, 1,3-, and 1,2,3-positions of the upper rim of calix[4]arene were functionalized with 1,5,9-triazacyclododecane ([12]ane-N3) moieties, which were able to coordinate with several metals (see Fig. 27.15). These calix[4]arene derivatives were complexed with Zinc(II) and copper(II) to produce effective catalysts for the cleavage reaction of phosphodiester as RNA models. As seen in Fig. 27.16, the reaction takes place over the calixarene-metal complexes that indeed clarifies the importance of the substitution pattern of ligated metal ions (1,2-vicinal or 1,3-distal) along with cahx[4]arene skeleton. 

Biomimetic Cu(II) and Fe(II) complexes with bis- and tris-pyridyl amino and imino thioether ligands and vacant (or potentially so) coordination positions (Fig. y are active as catalyst precursors for the solvent- and halogen-free MW-assisted oxidation of 1-phenylethanol by TBHP, in the presence of pyridazine or other N-based additives. Maximum TOF of 5220 h (corresponding to 87% yield) was achieved just after 5 min of reaction time under the low power MW irradiation. The same authors reported" the catalytic activity of related copper, iron, and vanadium systems with mixed-N,S pyridine thioether hgands. The Cu and Fe complexes proved to be useful catalysts in various MW-assisted alcohol oxidations with TBHP, at 80 °C. Thus, 5-containing ligands can also be used to create effective catalyst precursors. 

---