Models for the lower S states of photosystem II: A trinuclear mixed-valent Mn-II/Mn-IV/Mn-II complex

Alexiou M; Dendrinou-Samara C; Karagianni A; Biswas S; Zaleski CM; Kampf J; Yoder D; Penner-Hahn JE; Pecoraro VL; Kessissoglou DP

Inorganic Chemistry, Vol.42, No.7, 2185-2187, 2003

Alexiou M, Dendrinou-Samara C, Karagianni A, Biswas S, Zaleski CM, Kampf J, Yoder D, Penner-Hahn JE, Pecoraro VL, Kessissoglou DP

The trinuclear complex Mn-3(pko)(4)(CH3O)(2)(SCN)(2).CH3OH, 1, where Hpko is 2,2'-dipyridylketonoxime, is a rare example of a complex simultaneously containing Mn-II and Mn-IV. X-ray crystallography and XANES spectroscopy clearly distinguish the (Mn2MnIV)-Mn-II valence isomer from the more commonly observed (Mn2MnIV)-Mn-III formulation. Fits to variable-temperature magnetic susceptibility data indicate that the Mn-II and Mn-IV are ferromagnetically coupled (J = +6.13 cm(-1)) and that 1 has an S = 13/2 ground state.