Mimicking of the histidine brace structural motif in molecular copper(I) compounds

L-Nτ-methylhistidine methyl ester, MeHisOMe, has been employed as a potential ligand to mimic the histidine brace-type coordination of copper ions in enzymes such particulate methane monoxygenase or lytic polysaccharide monooxygenases. MeHisOMe was prepared by double-methylation ester. Subsequently, its complexation diphosphine copper(I) precursors [Cu(P^P)(MeCN)2]BF4 tested, which led complexes [Cu(P^P)(MeHisOMe)]BF4 (P^P=dpePhos: 1, P^P=XantPhos: 2, P^P=dppf: 3). 1–3 were fully characterized, also single crystal X-ray analysis, thus providing first structural data for with synthetic, authentic brace. The proved inert contact dioxygen. To improve biomimetic character attempts made formally replace ligands bis(pyrazolyl)methanes, Bpm. Correspondingly, [BpmCu(NCMe)x]BF4 synthesized, different substituents at 3-positions pyrazolyl (i. e. Bpm=di(3-(phenyl)-1H-pyrazol-1-yl)diphenylmethane, di(3-(mesityl)-1H-pyrazol-1-yl)methane and di(3-(tert-butyl)-1H-pyrazol-1-yl)diphenylmethane). Addition these products that so sensitive towards oxidation environment they eluded isolation. One experiment provided blue crystals product reaction. They belonged salt complex cation consisting Cu(μ-OH)2Cu core ligated two ligands, dimerises solid state give [Cu4(OH)4(MeHisOMe)4]4+.