caa a22 4500 475843770 CHVBK 20180406123908.0 cr unu---uuuuu 170329e20000401xx s 000 0 eng 10.1023/A:1027277831603 doi (NATIONALLICENCE)springer-10.1023/A:1027277831603 The structural basis for the enhanced oxygenase activity of copper acetate dimers encapsulated in zeolites [Elektronische Daten] [Suhas Chavan, D. Srinivas, Paul Ratnasamy] The oxygenase mimicking activity of copper acetate dimers in the regioselective ortho-hydroxylation of L-tyrosine to L-dopa is enhanced on encapsulation in zeolite Y. The structure and magnetic properties of the catalytic active site were characterized by EPR spectroscopy. The spectra of this "zeozyme” reveal the presence of (1) copper acetate dimers in the supercages and (2) isolated Cu(II) ions in the sodalite cages of the zeolite. There are significant differences in the EPR spectra of the "neat” and encapsulated complexes: on encapsulation in zeolite, the Cu-Cu exchange coupling constant, −, increases to 310 from 259 cm−1 for the "neat” complex (i.e., by about 19.7%). Simultaneously the Cu-Cu separation in the dimer, estimated indirectly from the exchange coupling constant, shortens to 2.40 Å in the encapsulated state from 2.64 Å in the "neat” complex. There is, hence, a relatively greater overlap of the metal orbitals of the dimer copper atoms inside the restricted confines of the zeolite cages. The consequent, enhanced, trans axial lability of the phenolate and dioxygen ligands promotes the catalytic oxygenase activity of copper acetate dimers on encapsulation in zeolites. A causal relationship between changes in the structural features of an active site on encapsulation in the zeolite and the corresponding catalytic activity has, thus, been established. Kluwer Academic Publishers, 2000 zeozyme nationallicence encapsulated complexes nationallicence copper acetate nationallicence copper dimers nationallicence enzyme mimic nationallicence EPR of copper nationallicence tyrosinase nationallicence oxidation nationallicence oxygenase nationallicence tyrosine oxidation nationallicence phenol oxidation nationallicence hydroxylation nationallicence Chavan Suhas National Chemical Laboratory, 411 008, Pune, India aut Srinivas D. National Chemical Laboratory, 411 008, Pune, India aut Ratnasamy Paul National Chemical Laboratory, 411 008, Pune, India aut Topics in Catalysis Kluwer Academic Publishers-Plenum Publishers 11-12/1-4(2000-04-01), 359-367 1022-5528 11-12:1-4<359 2000 11-12 11244 https://doi.org/10.1023/A:1027277831603 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1023/A:1027277831603 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Chavan Suhas National Chemical Laboratory, 411 008, Pune, India aut NATIONALLICENCE 700 1- Srinivas D. National Chemical Laboratory, 411 008, Pune, India aut NATIONALLICENCE 700 1- Ratnasamy Paul National Chemical Laboratory, 411 008, Pune, India aut NATIONALLICENCE 773 0- Topics in Catalysis Kluwer Academic Publishers-Plenum Publishers 11-12/1-4(2000-04-01), 359-367 1022-5528 11-12:1-4<359 2000 11-12 11244 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer