Stamos Nikolaos-Angelos, Ferentinos Eleftherios, Chrysina Maria, Raptopoulou Catherine P, Psycharis Vassilis, Sanakis Yiannis, Pantazis Dimitrios A, Kyritsis Panayotis, Mitrikas George
Institute of Nanoscience and Nanotechnology, N.C.S.R. "Demokritos", 15310 Athens, Greece.
Inorganic Chemistry Laboratory, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis, 15771 Athens, Greece.
Inorg Chem. 2020 Mar 16;59(6):3666-3676. doi: 10.1021/acs.inorgchem.9b03237. Epub 2020 Feb 20.
Strain effects on and metal hyperfine coupling tensors, , are often manifested in Electron Paramagnetic Resonance (EPR) spectra of transition metal complexes, as a result of their intrinsic and/or solvent-mediated structural variations. Although distributions of these tensors are quite common and well understood in continuous-wave (cw) EPR spectroscopy, reported strain effects on ligand hyperfine coupling constants are rather scarce. Here we explore the case of a conformationally flexible Cu(II) complex, [Cu{PhP(O)NP(O)Ph-κ'}], bearing P atoms in its second coordination sphere and exhibiting two structurally distinct CuO coordination spheres, namely a square planar and a tetrahedrally distorted one, as revealed by X-ray crystallography. The Hyperfine Sublevel Correlation (HYSCORE) spectra of this complex exhibit P correlation ridges that have unusual inverse or so-called "boomerang" shapes and features that cannot be reproduced by standard simulation procedures assuming only one set of magnetic parameters. Our work shows that a distribution of isotropic hyperfine coupling constants (hfc) spanning a range between negative and positive values is necessary in order to describe in detail the unusual shapes of HYSCORE spectra. By employing DFT calculations we show that these hfc correspond to molecules showing variable distortions from square planar to tetrahedral geometry, and we demonstrate that line shape analysis of such HYSCORE spectra provides new insight into the conformation-dependent spectroscopic response of the spin system under investigation.
应变对[具体符号]和金属超精细耦合张量的影响通常在过渡金属配合物的电子顺磁共振（EPR）光谱中表现出来，这是由于其内在的和/或溶剂介导的结构变化。尽管这些张量的分布在连续波（cw）EPR光谱中相当常见且已被充分理解，但关于应变对配体超精细耦合常数影响的报道却相当稀少。在这里，我们探讨了一种构象灵活的Cu（II）配合物[Cu{PhP（O）NP（O）Ph - κ'}]的情况，该配合物在其第二配位层中含有P原子，并且如X射线晶体学所示，呈现出两个结构不同的CuO配位层，即一个平面正方形和一个四面体畸变的配位层。该配合物的超精细子能级相关（HYSCORE）光谱显示出具有不寻常的反向或所谓“回旋镖”形状的P相关脊线，以及仅假设一组磁参数的标准模拟程序无法再现的特征。我们的工作表明，为了详细描述HYSCORE光谱的异常形状，需要一个跨越正负值范围的各向同性超精细耦合常数（hfc）分布。通过采用密度泛函理论（DFT）计算，我们表明这些hfc对应于从平面正方形到四面体几何形状呈现可变畸变的分子，并且我们证明这种HYSCORE光谱的线形分析为所研究的自旋系统的构象依赖性光谱响应提供了新的见解。
