Electrochemical, Computational, And Reactivity Studies Of Strongly Stabilized Cerium(iv) Hydroxylaminato Coordination Complexes And Pyrroloquinoline Quinone Cofactor Surrogates

A series of electron rich, air-stable hydroxylamine ligands and their strongly stabilized cerium(IV) hydroxylaminato complexes are described. Monotopic, ditopic, and tetratopic hydroxylaminato ligands are described. The synthesis and characterization of HLNOx, H2ODiNOx, H2PhNDiNOx, and H4TetraNOx were accomplished through modified literature procedures from their parent aryl bromides. The cerium(IV) complexes Ce(LNOx)4, Ce(ODiNOx)2 were synthesized by protonolysis reactions, crystallized, and characterized electrochemically and computationally. The cerium(IV) complexes exhibited significant stabilization of the Ce(III/IV) couple as observed in their cyclic voltammetry data. The pyrroloquinoline quinone (PQQ) is an important cofactor that shuttles redox equivalents in diverse metalloproteins. Quinoline 7,8-quinones have been synthesized and characterized as surrogates for PQQ to elucidate redox energetics within metalloenzyme active sites. The quinoline 7,8-quinones were synthesized, and the compounds were evaluated using solution electrochemistry. Together with a family of quinones, the products were evaluated computationally and used to generate a predictive correlation between a computed ΔG and the experimental reduction potentials. The methoxy substituted derivative exhibited catalytic activity in the dehydrogenation of benzylamines. The stoichiometric dehydrogenation of benzyl alcohols was also achieved with irradiation.