Lehnert Nicolai, Cornelissen Ursula, Neese Frank, Ono Tetsuya, Noguchi Yuki, Okamoto Ken-Ichi, Fujisawa Kiyoshi
Department of Chemistry, The University of Michigan, 930 North University, Ann Arbor, Michigan 48109, USA.
Inorg Chem. 2007 May 14;46(10):3916-33. doi: 10.1021/ic0619355. Epub 2007 Apr 21.
This study focuses on the geometric (molecular) structures, spectroscopic properties, and electronic structures of copper(II)-nitrito complexes as a function of second coordination sphere effects using a set of closely related coligands. With anionic hydrotris(pyrazolyl)borate ligands, one nitrite is bound to copper(II). Depending on the steric demand of the coligand, the coordination mode is either symmetric or asymmetric bidentate, which leads to different ground states of the resulting complexes as evident from EPR spectroscopy. The vibrational spectra of these compounds are assigned using isotope substitution and DFT calculations. The results demonstrate that nu sym(N-O) occurs at higher energy than nu asym(N-O), which is different from the literature assignments for related compounds. UV-vis absorption and MCD spectra are presented and analyzed with the help of TD-DFT calculations. The principal binding modes of nitrite to Cu(II) and Cu(I) are also investigated applying DFT. Using a neutral tris(pyrazolyl)methane ligand, two nitrite ligands are bound to copper. In this case, a very unusual binding mode is observed where one nitrite is eta1-O and the other one is eta1-N bound. This allows to study the properties of coordinated nitrite as a function of binding mode in one complex. The N-coordination mode is easily identified from vibrational spectroscopy, where N-bound nitrite shows a large shift of nu asym(N-O) to >1400 cm-1, which is a unique spectroscopic feature. The optical spectra of this compound exhibit an intense band around 300 nm, which might be attributable to a nitrite to Cu(II) CT transition. Finally, using a bidentate neutral bis(pyrazolyl)methane ligand, two eta1-O coordinated nitrite ligands are observed. The vibrational and optical (UV-vis and MCD) spectra of this compound are presented and analyzed.
本研究利用一组密切相关的共配体，重点研究了铜（II）-亚硝酸根配合物的几何（分子）结构、光谱性质和电子结构与第二配位层效应的关系。对于阴离子三（吡唑基）硼酸氢配体，一个亚硝酸根与铜（II）配位。根据共配体的空间需求，配位模式为对称或不对称双齿，这导致了所得配合物不同的基态，电子顺磁共振光谱表明了这一点。这些化合物的振动光谱通过同位素取代和密度泛函理论计算进行归属。结果表明，对称（N-O）振动出现在比不对称（N-O）振动更高的能量处，这与相关化合物的文献归属不同。紫外可见吸收光谱和磁圆二色光谱在含时密度泛函理论计算的帮助下进行了呈现和分析。还应用密度泛函理论研究了亚硝酸根与Cu（II）和Cu（I）的主要结合模式。使用中性三（吡唑基）甲烷配体时，两个亚硝酸根配体与铜配位。在这种情况下，观察到一种非常不寻常的结合模式，其中一个亚硝酸根以η1-O配位，另一个以η1-N配位。这使得能够在一个配合物中研究配位亚硝酸根的性质与结合模式的关系。从振动光谱中很容易识别出N配位模式，其中N配位的亚硝酸根的不对称（N-O）振动有很大位移，大于1400 cm-1，这是一个独特的光谱特征。该化合物的光谱在300 nm左右有一个强吸收带，这可能归因于亚硝酸根到Cu（II）的电荷转移跃迁。最后，使用双齿中性双（吡唑基）甲烷配体时，观察到两个η1-O配位的亚硝酸根配体。给出并分析了该化合物的振动光谱和光学（紫外可见和磁圆二色）光谱。
