Magnetic Properties of Some Triangular Trinuclear Complexes of [Ru2M(μ-CH3COO)6(μ3-O)(py)3]n+ with a Paramagnetic Ion M

Abstract

Magnetic susceptibilities and electron paramagnetic resonances (EPRs) of coordination compounds of triangular trinuclear [Ru2M(μ-CH3COO)6(μ3-O)(py)3]n+, M = Mn(II), Fe(III), Cr(III), Ni(II), or Co(II) ions, were observed. The results were analysed by the spin vector model. Effective Bohr magneton numbers showed that the main superexchange interaction within each cluster was of the order of J/k = −300 K. This was considered to be working through μ3-O. Together with some weaker superexchange interactions through μ-CH3COO paths, fittings with the susceptibilities of the model were tried. EPR signals at temperatures of a few K were characteristic of each M ion. M = Mn(II) and M = Fe(III) were at high spin states of S = 5/2 and M = Co(II) was at a low spin state of S = 1/2. Temperature dependences of EPR signals are discussed.

Large Zero‐Field Splittings of the Ground Spin State Arising from Antisymmetric Exchange Effects in Heterometallic Triangles

“…[10] Belinsky [11] and Tsukerblat et al [12] have calculated the effects of the ASE on the maximum S = 3 / 2 state (as ground or excited state) in Cu II 3 and V IV 3 triangles. The acetate analogues of these complexes have been reported, [14,15] and we find similar magnetic susceptibility (c) behavior. However, in-plane components are symmetry forbidden when the M 3 triangle lies on a mirror plane.…”

“…They have the classic structure of basic metal carboxylate triangles, [13] with bridging pivalate and terminal pyridine groups ( Figure 1). The acetate analogues of these complexes have been reported, [14,15] and we find similar magnetic susceptibility (c) behavior. {Ru 2 Mn} has c T = 4.42 cm 3 K mol À1 (Figure 2), the .…”

“…This is much larger than estimated previously for the acetate analogue by low-frequency EPR spectroscopy; [15] therefore, we have measured the value of D directly by high-frequency EPR spectroscopy. [18] Spectra at low frequencies are those of an axial effective spin 1 / 2 with g eff,?…”

Propriedades e aplicações de clusters trinucleares de carboxilatos de rutênio

“…Essa equivalência é quebrada nos clusters assimétricos e mistos gerando mais de um sinal, permitindo uma diferenciação entre estes e os simétri-cos. Também observa-se que os paramagnéticos (compostos 1 a 6) apresentam os sinais dos grupos metila em frequência mais alta que os diamagnéticos (compostos 7, 9 a 13), com exceção do cluster [Ru 2 CoO(CH 3 CO 2 ) 6 46 . A atribuição do espectro não é direta e interpretações errôneas podem ocorrer se técnicas bidimensionais (como 1 H x 13 C HETCOR e HMBC) não forem utilizadas, visto que nem todos os efeitos observados para hidrogênio são notados no espectro de carbono 60 . Nos últimos anos, a técnica de espectroscopia vibracional na região do infravermelho tem sido utilizada de forma rotineira na 64 .…”

“…A proximidade dos ions metálicos propicia a ocorrência de interações magnéti-cas e eletrônicas entre os sítios metálicos, tanto em compostos homonucleares, como em compostos heteronucleares do tipo [Ru 2 MO(CH 3 CO 2 ) 6 L 3 ] (M (II) = Mg [10][11][12] , Mn 8,11,13 , Co 8,11,[13][14][15] , Ni 8,11,13 , Zn 8,10-12 e M (III) = Cr 13,16 , Fe 13 , Co 14 , Rh 12,[17][18][19] ). A variedade de estados de oxidação leva a uma extensa química de valência mista.…”