含类立方烷簇芯[MoFe_3S_4]~(n+)(n=4,5)钼铁硫原子簇化合物的电子顺磁共振谱

本文报道簇合物(Et_4N)(MoFe_3S_4(Et_2dtc)_5)CH_3CN(1)和(MoFe_3S_4(C_5H_10NCSS)_5)CH_2Cl_2(2)在室温和液氮温度(77K)测试的ESR谱。在77K簇合物(1)和(2)的ESR谱分别解释为来自具有双量子跃迁(△W=2hv_0)的S=1和菱形对称的S=1/2的自旋体系,基态自旋S值与根据反铁磁性自旋耦合模型和9N—L规则计算结果一致。 簇合物(1)出现gx=gy=gz=(15/7)g_0≈4.3(E》g_0βH,D≈0)的ESR谱可以确认为Fe~(2+)碎片信号,而具有~(95,97)Mo特征超精细结构(a_0(1)≈38G)的g_0(1)=1.9735±0.0002信号来自Mo~(5+)碎片。簇合物(2)亦出现Mo~(5+)碎片信号(g_(2)=1.9748±0.0002,a_0(2)≈38G)。上述事实说明在分子内发生Fe~(2+)→Mo~(6+)净电子密度转移自氧化还原作用,选种电子非定域化有利于簇骼的形成与稳定。

ESR STUDIES OF Mo-Fe-S CUBANE-LIKE CLUSTERS WITH (MoFe_3 s_4 )~(n+)(n=4 or 5) UNITS

The ESR spectra of (Et4N ) ( MoFe3S4(Et2dtc)5)CH3CN(1) and (MoFe3-S4(C5H10NCSS)5)CH2Cl2(2) were measured at room temperature ( 292 K) and liquid nitrogen temperature ( 77K). The spectra at 77 K for clusters(1) and (2) can be interpreted in terms of a spin system of S = 1 with double-quantum transition (△W = 2hv0 ) and a system of S = 1/2 with rhombic symmetry, respectively, and the spin numbers of ground states S are consistent with the results of calculation on the basis of antiferromagnetic coupling model and 9N - L rule.In the ESR spectra of compound (1),gx =gy =gz = ( 15/7 ) g0≈4.3( E>> g BH,D≈0) can be assigned as the signal of Fe3+ fragment, and the signal of g0(1) = 1.9735 ±0.0002 with the characteristic hype fine structure ( a (1)≈38G ) was caused by a Mo5+ fragment.ESR spectra of compound(2) gave g value of 1.9748 ±0.0002 with six hfs splitting (a°(2)≈38G ) . The aforementioned fact implies the occurrence of intramolecular self-redox with the net electron density transfer from Fe2+ to Mo6+. This delocalization of electrons is favorable for the formation and stabilization of the cluster core.