Electron paramagnetic resonance studies of radical pairs [M(CO) ? 5 ]2(M = Cr, Mo, W) trapped in single crystals of PPh + 4 HM(CO) ? 5
作者:Rosemary C. Hynes、Keith F. Preston、Jerry J. Springs、John S. Tse、Antony J. Williams
DOI:10.1039/ft9918703121
日期:——
γ-Irradiated single crystals of PPh+4HM(CO)–5(M = Cr, Mo, W) exhibit powerful EPR spectra due to two distinct interacting pairs of M(CO)–5 radicals. g- and fine-structure (D) matrices were determined from measurements at 77 K of EPR spectra obtained as a function of angle in the ac and aa′ planes of crystallographically aligned single crystals of the Mo and W compounds. The data are compared with those
γ射线辐照的PPh + 4 HM(CO)– 5(M = Cr,Mo,W)单晶具有强大的EPR光谱,这是由于M(CO)– 5自由基有两个相互作用的对。g和精细结构(D)矩阵是根据EPR光谱在77 K处的测量结果确定的,这些测量结果是Mo和W化合物的晶体排列单晶的ac和aa '平面中的角度的函数。将数据与先前针对Cr化合物获得的数据进行比较。在所有三种情况下,g和一个D-张量与四边形c对齐的晶体轴和主要的g值适用于d 7方形锥体M(CO)– 5自由基。经典的偶极子计算表明,这两个自由基对对应于晶体中最接近和最接近的一对未损坏的阴离子,前者沿c方向,后者沿偏斜方向。Mo和W最接近的对的D值表明各向异性交换对两个未成对电子的耦合有很大贡献。