The goal of the proposed research is to develop synthetic inorganic copper complexes to understand the
fundamental aspects of structure and function in Cu-dependent monooxygenase enzymes. These
metalloenzymes contain 1 or 2 Cu ions in their active center and they couple the reduction of O2 with the
oxidation of substrates via formation of transient Cun/O2 reactive intermediates. We are particularly interested
in inspecting the reactivity of mononuclear Cu/O2 species since they have been proposed as active oxidants in
the hydroxylation of C-H bonds (in peptidylglycine a-hydroxylating monooxygenase and lytic polysaccharide
monooxygenase). Many questions concerning the identity of the active Cu/O2 species remain unanswered,
including: i) oxidation state of Cu (i.e. CuI, CuII, CuIII); ii) reduction/protonation state of O2 (O2¿-,(H)O22-,
(H)O2-) and the pKa and redox potentials associated with these Cu/O2 species; iii) mechanism by which the
Cu/O2 intermediates carry out C-H hydroxylations (e.g. O-O cleavage mechanism, possible generation of high-
valent Cu-oxyl species before C-H oxidation). In this research project, we tackle this problem in an
unprecedented fashion: we utilize ligand scaffolds (L) that contain C-H substrates covalently attached to their
structure (imino-pyridine substrate-containing ligands synthesized from condensation of ketones and amines).
This will permit us to generate and characterize LCu/O2 species and evaluate their reactivity towards
intramolecular C-H hydroxylation of the substrate-ligands. Research subprojects include:
(1) Substrate-ligand scaffold modifications will permit us to: i) evaluate the ability of the Cu/O2 species to
oxidize sp3 C-H bonds and sp2 C-H bonds; ii) control the stereo-electronic properties of the Cu complexes by
the use of different ligand donors (i.e. N2, N3, N4) that will lead to the generation of mononuclear LCuO2 and
dinuclear L2Cu2O2 species, and analyze their reactivity towards intramolecular C-H hydroxylation; iii) develop
bioinspired synthetic protocols (amine/Cu/oxidant) for the hydroxylation of a wide variety of substrate-ketones.
(2) The proposed Cu complexes bearing substrate-ligand scaffolds offer a unique opportunity to study the
chemical properties of LCuII(OOR) since their structure can be modified in three ways: by changing the ligand
denticity (N2, N3 and N4), substrate (sp3 vs. sp2) and oxidant (H2O2, tBuOOH or CumOOH). The generation of
LCuII(OOR) species (metastable at low temperatures) will lead to: i) understanding the mechanism by which
LCuII(OOR) oxidize C-H bonds by tracking the decay of LCuII(OOR) and the evolution of the intramolecular
hydroxylation yields; ii) analyzing the reactivity of LCuII(OOR) towards H+ and e- sources that could lead to
reductive O-O cleavage; iii) studying the reactivity of LCuII(OOR) towards biologically relevant external
substrates such as C-H bonds, phenols, and sulfides.
Overall, these studies will contribute to a broader understanding of the biochemical role of Cu ions involved in
O2 reduction and biologically relevant oxidations.