Ligand-Mediated Pseudohypersensitivity of Some 4f–4f Transitions in Neodymium(III) Interaction with Fluorinated Nucleic Acid Components
作者:Sudhindra N. Misra、Surendra B. Mehta
DOI:10.1246/bcsj.64.3653
日期:1991.12
Absorption difference and comparative absorption spectrophotometry of the systems containing Nd(III) and fluorinated nucleic bases (fluoroadenine, fluorocytosine, fluorothymine, and fluorouracil) and fluorinated nucleosides (fluoroadenosine, fluorocytidine, fluorothymidine, and fluorouridine) in ethyl acetate–water (90:10), have shown that certain 4f–4f transitions (4I9⁄2→4G7⁄2, 4F7⁄2, 4F5⁄2, and 4F3⁄2), which are generally considered to be insensitive, have been found to exhibit substantial sensitivity towards even minor changes in the coordination environment around neodymium(III). The observation has been referred to as “Ligand-Mediated Pseudohypersensitivity.” The magnitude of various spectral parameters (energy interaction, Slater-Condon interelectronic repulsion Fk, spin–orbit interaction ξ4f, nephelauxetic \barβ, b, δ, and Judd–Ofelt Tλ intensity and oscillator strength (P)), computed using regression analysis, has been used in exploring the degree of inner and outer sphere coordination, incidence of covalency and extent of involvement of metal 4f orbitals in bonding. The isolation of solid complexes and their characterization by elemental analysis, infrared spectral, and Karl Fischer titration suggested octa and nona coordinated environment around neodymium and some probable structures for these complexes have been proposed.
对含有 Nd(III)和氟化核酸(氟腺嘌呤、氟胞嘧啶、氟胸腺嘧啶和氟尿嘧啶)以及氟化核苷(氟腺苷、氟胞嘧啶、氟胸腺嘧啶和氟尿苷)的体系在乙酸乙酯-水(90:10)中的某些 4f-4f 转变(4I9⁄2→4G7⁄2、4F7⁄2、4F5⁄2 和 4F3⁄2)通常被认为是不敏感的,但我们发现它们对钕(III)周围配位环境的微小变化也非常敏感。这一观察结果被称为 "配体介导的伪超敏感性"。利用回归分析计算出的各种光谱参数(能量相互作用、斯莱特-康顿电子间斥力 Fk、自旋轨道相互作用 ξ4f、nephelauxetic bar\β、b、δ 以及 Judd-Ofelt Tλ 强度和振荡器强度 (P))的大小,已被用于探索内外球配位程度、共价发生率以及金属 4f 轨道参与成键的程度。固体配合物的分离及其通过元素分析、红外光谱和卡尔费休滴定法进行的表征表明,钕周围存在八配位和九配位环境,并提出了这些配合物的一些可能结构。