Structure and Spectroscopy of Copper−Dioxygen Complexes

Theoretical Characterization of End-On and Side-On Peroxide Coordination in Ligated Cu2O2 Models

“…Moreover, large variations in relative energies were observed when four, five, or six roots were employed in multistate calculations (see Table 2). Interestingly, reducing the symmetry to C i (which permits a greater mixing of the active and inactive orbitals in the CAS) leads to a smooth convergence and good agreement between active spaces of (12,12), (12,14), and (16,14) and also to good agreement between CASPT2 and MS-CASPT2 (i.e., interactions between multiple roots are rendered negligible). However, the converged energy of 1 0 relative to that of 1 100 is predicted to be -16.7 kcal mol -1 , which is very far from the CR-CC results.…”

“…[1][2][3][4][5][6][7][8] Tyrosinase 1,5,6,9 is one example of an enzyme whose active site incorporates a Cu 2 O 2 core, and substantial effort has also been devoted to the characterization of smaller inorganic models characterized by the same core. 2, [10][11][12][13][14][15][16][17][18] There are several motifs for the binding of molecular O 2 to two supported copper(I) atoms ( Figure 1). 12,19 Best characterized experimentally (because they have been observed for many different supporting ligand sets) are the side-on µ-η 2 :η 2 peroxo and the bis(µ-oxo).…”

“…2, [10][11][12][13][14][15][16][17][18] There are several motifs for the binding of molecular O 2 to two supported copper(I) atoms ( Figure 1). 12,19 Best characterized experimentally (because they have been observed for many different supporting ligand sets) are the side-on µ-η 2 :η 2 peroxo and the bis(µ-oxo). The trans end-on µ-η 1 :η 1 peroxo motif was first described by Jacobson et al 20 This binding mode is preferred when the copper atoms are supported by tripodal tetradentate ligands, [21][22][23][24][25] although when such ligands become too sterically demanding for trigonal bipyramidal coordination of copper a preference for the bis(µ-oxo) motif with concomitant loss of two ligand-copper interactions has been documented.…”

Hiking on the potential energy surface of a functional tyrosinase model – implications of singlet, broken-symmetry and triplet description

“…2,3 Besides the biologically occurring side-on-bonded peroxide, the isomeric bis(m-oxo) dicopper(III) core (O core) has often been found in model complexes. 3,4 The most accepted mechanism, based on both theory and experimental data, proposes that a P core species performs the hydroxylation reaction through an electrophilic aromatic substitution reaction and that the cleavage of the O-O bond occurs either concerted with or after the C-O bond formation. 5 However, radical mechanisms have been proposed 6 and several examples of highly active pure O core complexes kept the discussion about the truly hydroxylating species in tyrosinase alive.…”

“…1) between O and P cores can be shifted by the choice of the ligands, temperature and counteranions. 3 Moreover this equilibrium is theoretically regarded as a torture track for computational chemistry, 8,9 since the amount of exact exchange heavily influences the predicted energies for the O/P equilibrium. 9 Several studies with multi-reference (MR) calculations based on a wave functional theory (WFT) method such as CASPT2, 10 MRCI + Q, 11 DMRG, 12 and RASPT2 13 have been carried out with ammonia ligands as a substitution for histidine residues.…”