title: Synthesis, characterization, and reactivity studies of heterodinuclear complexes modeling active sites in purple acid phospatases.
abstract: To model the heterodinuclear active sites in plant purple acid phosphatases, a mononuclear synthon, [Fe(III)(H(2)IPCPMP)(Cl(2))][PF(6)] (1), has been generated in situ from the ligand 2-(N-isopropyl-N-((2-pyridyl)methyl)aminomethyl)-6-(N-(carboxylmethyl)-N-((2-pyridyl)methyl)amino methyl)-4-methylphenol (IPCPMP) and used to synthesize heterodinuclear complexes of the formulas [Fe(III)M(II)(IPCPMP)(OAc)(2)(CH(3)OH)][PF(6)] (M = Zn (2), Co (3), Ni (4), Mn (5)), [Fe(III)Zn(II)(IPCPMP)(mpdp)][PF(6)] (6) (mpdp = meta-phenylene-dipropionate), and [Fe(III)Cu(II)(IPCPMP) (OAc)}(2)(μ-O)][PF(6)] (7). Complexes 2-4, 6, and 7 have been crystallographically characterized. The structure of 6 is a solid state coordination polymer with heterodinuclear monomeric units, and 7 is a tetranuclear complex consisting of two heterodinuclear phenolate-bridged Fe(III)Cu(II) units bridged through a μ-oxido group between the two Fe(III) ions. Mössbauer spectra confirm the presence of high spin Fe(III) in an octahedral environment for 1, 3, and 5 while 2 and 4 display relaxation effects. Magnetic susceptibility measurements indicate weak antiferromagnetic coupling for 3, 4, and 5 and confirm the assignment of the metal centers in 2-5 as high spin Fe(III)-M(II) (M = Zn, Co (high spin), Ni (high spin), Mn (high spin)). Complexes 2-5 are intact in acetonitrile solution as indicated by IR spectroscopy (for 2-4) and electrospray ionization mass spectrometry (ESI-MS) but partly dissociate to hydroxide species and a mononuclear complex in water/acetonitrile solutions. UV-vis spectroscopy reveal pH-dependent behavior, and species that form upon increasing the pH have been assigned to μ-hydroxido-bridged Fe(III)M(II) complexes for 2-5 although 2 and 3 is further transformed into what is propsed to be a μ-oxido-bridged tetranuclear complex similar to 7. Complexes 2-5 enhance phosphodiester cleavage of 2-hydroxy-propyl-p-nitrophenyl phosphate (HPNP) and bis(2,4-dinitrophenyl)phosphate (BDNPP), but the reactivities are different for different complexes and generally show strong pH dependence.
authors: Inorganic Chemistry Research Group, Chemical Physics, Center for Chemistry and Chemical Engineering, Lund University, Box 124, SE-221 00 Lund, Sweden. ebbe.nordlander@chemphys.lu.se
authors: Martin
authors: M
authors: Jarenmark
authors: Matti
authors: M
authors: Haukka
authors: Serhiy
authors: S
authors: Demeshko
authors: Felix
authors: F
authors: Tuczek
authors: Luca
authors: L
authors: Zuppiroli
authors: Franc
authors: F
authors: Meyer
authors: Ebbe
authors: E
authors: Nordlander
mesh_terms: D000135:Acid Phosphatase / Q000737:chemistry*; D040761:Biomimetic Materials / Q000138:chemical synthesis* / Q000737:chemistry*; D020134:Catalytic Domain; D004583:Electrons; D004951:Esterification; D006023:Glycoproteins / Q000737:chemistry*; D006868:Hydrolysis; D008280:Magnetics; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D010710:Phosphates / Q000737:chemistry; D010944:Plants / Q000201:enzymology; D013055:Spectrophotometry, Infrared; D015204:Spectroscopy, Mossbauer; D028561:Transition Elements / Q000737:chemistry
chemical_list: D006023:Glycoproteins; D009942:Organometallic Compounds; D010710:Phosphates; D028561:Transition Elements; C091137:purple acid phosphatase; D000135:Acid Phosphatase