The paramagnetic trigonal-planar copper complexes {K(18C6)}-[Cu II (OC(CH 3 )(CF 3 ) 2 ) 3 ] (2) and K[Cu II (OC(C 6 H 5 )(CF 3 ) 2 ) 3 ] (3) have been prepared and characterized, including X-ray crystallography, in 61% and 3% yields, respectively. The latter complex does not form preferentially, because CuBr 2 and KOC(C 6 H 5 )(CF 3 ) 2 ) 3 also form the diamagnetic complexes {K(18C6)}-[K 2 {Cu I (OC(C 6 H 5 )(CF 3 ) 2 ) 2 } 3 ] (4) and {K(18C6)}[Cu III (OC(C 6 H 4 )(CF 3 ) 2 ) 2 ] (5). These species were characterized by X-ray crystallography, UV−vis spectroscopy, 1 H, 13 C{ 1 H}, and 19 F{ 1 H} NMR spectroscopy, and elemental analysis. The unique organocuprate Cu(III) species with {O 2 C 2 } coordination was formed by ortho metalation of two phenyl rings, resulting in trans-{O 2 C 2 } coordination of Cu(III), and is stable at room temperature in the solid state and in dark solutions of THF.

Cu complexes of the form K[(R P)Cu(pin )], in which (pin ) is the bidentate, oxygen-donating ligand perfluoropinacolate, were synthesized and characterized. Low-temperature oxygenation of the K[(R P)Cu(pin )(PR )] species resulted in a trisanionic bis(μ -oxo) trinuclear copper(II,II,III) core characterized by UV/Vis spectroscopy (λ [nm] = 330, 535, 630), cryospray-ionization mass spectrometry, and X-band electron paramagnetic resonance spectroscopy (derivative resonance at 3300 G, Δm =2 at 1500 G). The kinetic behavior of the trimeric {Cu O } species was quantified by stopped-flow spectroscopy and the associated electronic structures were investigated by DFT calculations. An asymmetric {Cu O } species, T , which bears a structure similar to multicopper oxidases, forms prior to full formation of the symmetric trinuclear core, T . The trimer catalytically oxidizes para-hydroquinone to benzoquinone (a form of oxidase chemistry).

Isotope-edited FT-IR spectroscopy is a combined synthetic and spectroscopic method used to characterize local (e.g., residue-level) vibrational environments of biomolecules. We have prepared the 3(10) helical peptide Z-Aib6-OtBu and seven (13)C-enriched analogues that vary only in the number and position(s) of (13)C═O isotopic enrichment. FT-IR spectra of these eight peptides solvated in the nonpolar aprotic solvent dichloromethane have been collected and compared to frequency, intensity, and normal mode results of DFT calculations. Single (13)C enrichment of amide functional groups tends to localize amide I vibrational eigenmodes, providing residue-specific information regarding the local environment (e.g., hydrogen bonding or solvent exposure) of the peptide bond. Double (13)C enrichment of Z-Aib6-OtBu allows for examination of interamide coupling between two labeled amide functional groups, providing experimental evidence of interamide coupling in the context of 3(10) helical structure. Although the calculated and observed interamide couplings of Z-Aib6-OtBu are a few cm(-1) and less, the eight peptides exhibit distinct infrared spectra, revealing details of interamide coupling and residue level vibrational environments.

A mechanism for the formation of O-donor trinuclear {Cu3O2} moiety is reported.