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本实验测定了单立方烷固氮模拟物(Et_4N)[MoFe_3S_4(Et_2dtc)_3]·CH_3CN的穆斯堡尔谱。它是由两组对称的四极分裂双峰叠加而成。实验数据用最小二乘法计算机程序拟合。经计算机拟合后的穆斯堡尔参数为(在15.5℃时):对于Fe_Ⅰ,δ=0.406±0.04mm/s;ΔE_Q=1.107±0.04mm/s;线宽为0.296±0.04mm/s;对于Fe_Ⅱ,δ=0.266±0.04mm/s;ΔE_Q=0.395±0.04mm/s;线宽为0.462±0.04mm/s。化学位移δ值是相对于α-Fe的。这两组四极分裂双峰的面积比约为3:1。由Fe_r的化学位移和四极裂距可确定它是高自旋态,价态在+2至+3之间。利用四面体FeS_4中铁原子的化学位移δ与价态S的经验公式δ=1.44—0.43S可得出Fe_Ⅰ的平均价态为高自旋+2.5价。从穆斯堡尔参数可确定Fe_(Ⅱ)属于高自旋+3价。
In this experiment, the Mossbauer spectrum of mono-cubic nitrogen-fixing mimic (Et_4N) [MoFe_3S_4 (Et_2dtc) _3] · CH_3CN was determined. It is composed of two symmetrical quadrupole bimodal superimposed. The experimental data were fitted by least square computer program. The computer-fitted Mössbauer parameters are (at 15.5 ° C): δ = 0.406 ± 0.04 mm / s for Fe_Ⅰ; ΔE_Q = 1.107 ± 0.04 mm / s; line width is 0.296 ± 0.04 mm / s; For Fe_II, δ = 0.266 ± 0.04 mm / s; ΔE_Q = 0.395 ± 0.04 mm / s; line width is 0.462 ± 0.04 mm / s. The chemical shift δ value is relative to α-Fe. The area ratio of these two sets of quadrupole bimodal peaks is about 3: 1. From the chemical shift of Fe_r and quadrupole crack can be determined that it is a high spin state, valence between +2 to +3. The empirical formula δ = 1.44-0.43S of iron atom in tetrahedral FeS_4 and the empirical formula of valence S can be obtained that the average valence of Fe_Ⅰ is high spin +2.5 valence. From the Mossbauer parameters, Fe_ (Ⅱ) belongs to the high spin +3 valence.