Journal of the American Chemical Society, Vol.118, No.11, 2669-2678, 1996
Chemical Modeling of the Oxygen-Evolving Center in Plants - Synthesis, Structure, and Electronic and Redox Properties of a New Mixed-Valence Mn-Oxo Cluster - ((Mn2O2)-O-III,IV(Bisimme(2)en)(2))(3+) (Bisimme(2)En=n,N’-Dimethyl-N,N’-bis(Imidazol-4-Ylmethyl)Ethane-1,2-Diamine) - EPR Detection of an Imidazole Radical-Induced by UV Irradiation at Low-Temperature
The compound [(Mn2O2)-O-III.IV(bisimMe(2)en)(2)](ClO4)(3) . H(2)0 (bisimMe(2)en = N,N’-dimethyl-N,N’-bis(imidazol-4-ylmethyl)ethane-1,2-diamine) was synthesized. It crystallizes in the monoclinic space group C2/C with a = 18.139(8) Angstrom, b = 12.694(5) Angstrom, c = 17.694(8) Angstrom, beta = 107.5(6)degrees, V = 3885(6) Angstrom(3), and Z = 4. The cation [(Mn2O2)-O-III.IV(bisimMe(2)en)(2)](3+) contains a di-manganese di-mu-oxo unit. The Mn-Mn axis is a C-2 axis. The Mn-Mn axis is a C-2 imidazole distances for Mn-III or Mn-IV are distinct : respectively, 2.208(9) and 2.004(8) Angstrom. The ground state is a S-A=2,S-B=3/2,S=1/2] state separated by 420 cm(-1) from the S = 3/2 state. The EPR spectrum has been simulated with A(lxy) = 160 10(-4) cm(-1), A(1z) = 1.36.10(-4) cm(-1), A(2xy) = 72.10(-4) cm(-1), A(2z) = 71.10(-4) cm(-1), g(xy) = 1.997, g(z) = 1.993. : respectively, 2.208(9) and 2.004(8) Angstrom. The ground state is a S-A=2,S-B=3/2,S=1/2] state separated by 420 cm(-1) from the S = 3/2 state. The EPR spectrum has been simulated with A(lxy) = 160 10(-4) cm(-1), A(1z) = 1.36.10(-4) cm(-1), A(2xy) = 72.10(-4) cm(-1), A(2z) = 71.10(-4) cm(-1), g(xy) = 1.997, g(z) = 1.993. : respectively, 2.208(9) and 2.004(8) Angstrom. The ground state is a S-A=2,S-B=3/2,S=1/2] state separated by 420 cm(-1) from the S = 3/2 state. The EPR spectrum has been simulated with A(lxy) = 160 10(-4) cm(-1), A(1z) = 1.36.10(-4) cm(-1), A(2xy) = 72.10(-4) cm(-1), A(2z) = 71.10(-4) cm(-1), g(xy) = 1.997, g(z) = 1.993.
Keywords:PHOTOSYNTHETIC WATER OXIDATION;PHOTOSYSTEM-II;MANGANESE CENTER;ACTIVE-SITE;PARAMAGNETIC-RES;COMPLEXES;STATE;CALCIUM;LIGANDS;ENZYME