Electronic structure, porphyrin core distortion, and fluxional behavior of bis-ligated low-spin iron(II) porphyrinates
Electronic structure, porphyrin core distortion, and fluxional behavior of bis-ligated low-spin iron(II) porphyrinates
复制标题
DOI：
10.1021/jp963039s
复制
发表时间：
1997-06-05
影响因子：
2.9
通讯作者：
Trautwein, AX
中科院分区：
文献类型：
--
作者：
Grodzicki, M;Flint, H;Trautwein, AX
用穆斯堡尔谱学研究了三种轴向双配位铁卟啉配合物[PFeL_2]在4.2-230 ℃温度范围内的结构。[TMEPFe（2-MeImH）（2）]（1）、[TMPFe（N-MeIm）（2）]（2）和[OEPFe-（PMe 3）（2）]（3）之间的四极分裂Δ E-Q存在较大差异（分别为1.61、1.07和0.38 mm/s）。化合物3在150 K以上表现出显著的谱线增宽，这表明流动畸变和/或配体旋转。在局域密度近似下的分子轨道计算产生的电场梯度（efg）与测量的四极分裂，Δ E-Q，和测量的efg的符号，观察到的四极分裂的差异可以归因于扭曲（皱）与2和3相比，1中的卟啉核的共价相互作用以及1和2的轴向氮供体与磷的共价相互作用的差异捐赠者3所观察到的温度依赖性谱线增宽3与计算的低旋转势垒相关。
Three axially bis-ligated Fe(II) porphyrinates, [PFeL2], have been investigated by Mossbauer spectroscopy over the temperature range 4.2-230 EC. and in an applied field of 6 rh( Relatively large differences in the quadrupole splitting Delta E-Q were found among [TMEPFe(2-MeImH)(2)] (1), [TMPFe(N-MeIm)(2)] (2), and [OEPFe-(PMe3)(2)] (3) (1.61, 1.07, and 0.38 mm/s, respectively). Compound 3 exhibits significant line broadening above 150 K that indicates fluxional distortion and/or ligand rotation. Molecular orbital calculations in the local density approximation yield electric field gradients (efg) in good agreement with the measured quadrupole splittings, Delta E-Q, and the measured sign of the efg, The observed differences in quadrupole splittings can be ascribed to distortions (ruffling) of the porphyrin core in 1 as compared to 2 and 3 and to the differences in covalent interactions of the axial nitrogen donors of 1 and 2 and phosphorous donors of 3. The observed temperature-dependent line broadening of 3 correlates with the low calculated rotational barrier.