X-ray absorption edge spectroscopy and computational studies on LCuO2 species:: Superoxide-CuII versus peroxide-CuIII bonding
X-ray absorption edge spectroscopy and computational studies on LCuO2 species:: Superoxide-CuII versus peroxide-CuIII bonding
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DOI：
10.1021/ja0615223
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发表时间：
2006-06-28
影响因子：
15
通讯作者：
Solomon, Edward I.
中科院分区：
文献类型：
--
作者：
Sarangi, Ritimukta;Aboelella, Nermeen;Solomon, Edward I.
研究了两种单核CuO_2配合物[Cu（O-2）{HB（3-Ad-5-（i）Prpz）（3）}]（1）和[Cu（O-2）（β-二酮亚胺）]（2），已经使用Cu K-和L-边X射线吸收光谱（XAS）研究结合价键构型相互作用（VBCI）模拟和自旋不受限制的对称性破缺密度泛函理论（DFT）进行了评估。计算。Cu K-和L-边XAS数据分别表明1和2的Cu（II）和Cu（III）性质。在L-边下的总积分强度显示，1和2中的Psi（*）（LUMO）分别含有20%和28%的Cu特征，表明两种络合物中的非常共价的基态，尽管在1中更是如此。两态VBCI模拟也表明2的基态具有更多的Cu（竖线3d（8）>）特征。密度泛函理论计算表明，两种配合物的Psi（*）（LUMO）均以O-2（n-）特征为主，而1的O-2（n-）特征较高.结果表明，配体L在调节LCuO_2体系中的Cu-O-2键中起着重要作用，并使1和2的基态分别具有Cu（II）-过氧化氢和Cu（III）-过氧化氢的特征.利用密度泛函理论和含时密度泛函理论计算了配位场（LF）和分子中吸收原子上的电荷（Q（mol）（M））对L边和K边能移的贡献。结果表明，LF对边能移动的贡献最大，而Q（mol）（M）的影响较小.在Cu（III）络合物中的Cu上的电荷被发现与Cu（II）络合物中的电荷类似，这表明与配体的相互作用强得多，导致广泛的电荷转移。
The geometric and electronic structures of two mononuclear CuO2 complexes, [Cu(O-2){HB(3-Ad-5-(i)Prpz)(3)}] (1) and [Cu(O-2)(beta-diketiminate)] (2), have been evaluated using Cu K- and L-edge X-ray absorption spectroscopy (XAS) studies in combination with valence bond configuration interaction (VBCI) simulations and spin-unrestricted broken symmetry density functional theory (DFT) calculations. Cu K- and L-edge XAS data indicate the Cu(II) and Cu(III) nature of 1 and 2, respectively. The total integrated intensity under the L-edges shows that the Psi(*)(LUMO)'s in 1 and 2 contain 20% and 28% Cu character, respectively, indicative of very covalent ground states in both complexes, although more so in 1. Two-state VBCI simulations also indicate that the ground state in 2 has more Cu (vertical bar 3d(8)>) character. DFT calculations show that the Psi(*)(LUMO)'s in both complexes is dominated by O-2(n-) character, although the O-2(n-) character is higher in 1. It is shown that the ligand L plays an important role in modulating Cu-O-2 bonding in these LCuO2 systems and tunes the ground states of 1 and 2 to have dominant Cu(II)-superoxide- like and Cu(III)-peroxide-like character, respectively. The contributions of ligand field (LF) and the charge on the absorbing atom in the molecule (Q(mol)(M)) to L- and K-edge energy shifts are evaluated using DFT and time-dependent DFT calculations. It is found that LF makes a dominant contribution to the edge energy shift, while the effect of Q(mol)(M) is minor. The charge on the Cu in the Cu(III) complex is found to be similar to that in Cu(II) complexes, which indicates a much stronger interaction with the ligand, leading to extensive charge transfer.