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Title: High-spin tetranuclear Mn(II)(2)Mn(IV)(2) clusters with unique Mn(ii)-Mn(iv) magnetic exchange: synthesis, structures and magnetism.
Author: Zhou AJ, Liu JL, Herchel R, Leng JD, Tong ML.
Journal: Dalton Trans; 2009 May 07; (17):3182-92. PubMed ID: 19421620.
Abstract:
Reactions of N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine (H(4)edte) with MnCl(2).4H(2)O or FeCl(3).6H(2)O in MeOH or MeCN with different bases yield four butterfly-like tetranuclear clusters with fused defective dicubane M(4)O(6) cores: [Mn(II)(2)Mn(IV)(2)(mu(4)-Hedte)(2)(thme)(2)].MeCN () (H(4)edte = N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine, H(3)thme = 1,1,1-tris(hydroxymethyl)ethane), [Mn(II)(2)Mn(IV)(2)(mu(4)-Hedte)(2)(thme)(2)].2MeOH (), [Fe(III)(4)(mu(4)-Hedte)(2)(N(3))(6)].2MeCN () and [Fe(III)(4)(mu(4)-edte)(2)(N(3))(4)(MeOH)(2)] (). Both and crystallize in the triclinic space group P1[combining macron], while and crystallize in the monoclinic space group P2(1)/c and P2(1)/n, respectively. The hexadentate Hedte(3-) ligand in , and the edte(4-) ligand in acts in a similar mu(4):eta(1):eta(1):eta(1):eta(2):eta(2):eta(3) coordination mode to bridge four metal ions into butterfly-like tetranuclear clusters with fused defective dicubane M(4)O(6) cores. Magnetic studies show that has the spin ground state S(T) = 8 while has the spin ground state S(T) = 0. Within the Mn(4)O(6) cluster core of , both Mn(iv)Mn(ii) and Mn(ii)Mn(ii) ferromagnetic interactions (J(Mn(iv)Mn(ii)) = +2.91 cm(-1) and J(Mn(ii)Mn(ii)) = +7.94 cm(-1)) occur contrary to the Fe(4)O(6) core, where antiferromagnetic exchange exists (J(aptical-Fe(iii)central-Fe(iii)) = -15.4 cm(-1) and J(central-Fe(iii)central-Fe(iii)) = -4.5 cm(-1)).

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