title: Zeolite framework stabilized copper complex inspired by the 2-His-1-carboxylate facial triad motif yielding oxidation catalysts.
abstract: The stabilization of a mononuclear copper(II) complex with one MIm2Pr ligand [MIm2Pr = 3,3-bis(1-methylimidazol-2-yl)propionate] in the supercages of zeolite Y was attempted, and the resulting materials were tested for their activity in oxidation catalysis. The preparation procedure yielded initially two species (labeled 1 and 2) within the pore system of the zeolite material, which differ in molecular structure and chemical composition as determined by UV/vis, ESR, IR, and XAFS spectroscopy. In species 1, the copper was found to be five-coordinated, with one MIm2Pr ligand in a facial-type NNO coordination toward copper, the other two coordination sites being occupied by oxygen atoms from either the zeolite framework and/or a water molecule. The total charge of this complex is 1+. In species 2, the copper is surrounded by two MIm2Pr ligands, both in a facial-type coordination mode, identical to the homogeneous Cu(MIm2Pr)2 complex. This neutral species 2 is easily washed out of the zeolite, whereas the mononuclear species 1 remains inside the zeolite material upon washing. The spectroscopic characteristics and activity for 3,5-di-tert-butylcatechol and benzyl alcohol oxidation of species 1 compared closely with that of the zeolite-immobilized Cu(histidine) complexes but differed from that of the homogeneous Cu(MIm2Pr)2 complex. It was therefore found that encapsulation in zeolite offers a route to stabilize a 5-fold-coordinated copper complex with novel catalytic properties. This 1:1 Cu(MIm2Pr) complex is not formed in solution.
authors.affiliation: Department of Inorganic Chemistry and Catalysis, Utrecht University, Debye Institute, Sorbonnelaan 16, 3584 CA Utrecht, The Netherlands.
authors.forename: Kaisa
authors.initials: K
authors.lastname: Kervinen
authors.forename: Pieter C A
authors.initials: PC
authors.lastname: Bruijnincx
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Beale
authors.forename: J Gerbrand
authors.initials: JG
authors.lastname: Mesu
authors.forename: Gerard
authors.initials: G
authors.lastname: van Koten
authors.forename: Robertus J M
authors.initials: RJ
authors.lastname: Klein Gebbink
authors.forename: Bert M
authors.initials: BM
authors.lastname: Weckhuysen
mesh_terms: D040761:Biomimetic Materials / Q000737:chemistry; D002264:Carboxylic Acids / Q000737:chemistry*; D002384:Catalysis; D003300:Copper / Q000737:chemistry*; D006639:Histidine / Q000031:analogs & derivatives*; D007093:Imidazoles / Q000737:chemistry*; D008958:Models, Molecular; D019159:Nonheme Iron Proteins / Q000737:chemistry; D009942:Organometallic Compounds / Q000737:chemistry; D010084:Oxidation-Reduction; D011422:Propionates / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D019265:Spectroscopy, Near-Infrared; D017641:Zeolites / Q000737:chemistry*
chemical_list: D002264:Carboxylic Acids; D007093:Imidazoles; D019159:Nonheme Iron Proteins; D009942:Organometallic Compounds; D011422:Propionates; D017641:Zeolites; D006639:Histidine; D003300:Copper; C018100:1-methylimidazole