Marrazzini Gioia, Gabbiani Chiara, Ciancaleoni Gianluca
Dipartimento di Chimica e Chimica Industriale, Università degli Studi di Pisa, via Giuseppe Moruzzi 13, Pisa 56124, Italy.
ACS Omega. 2019 Jan 16;4(1):1344-1353. doi: 10.1021/acsomega.8b03330. eCollection 2019 Jan 31.
The influence of weak interactions on the donation/back-donation bond components in the complex [(NHC)Au()] (NHC = N-heterocyclic carbene; = selenourea) has been studied by coupling experimental and theoretical techniques. In particular, NMR H and pulsed-field gradient spin-echo titrations allowed us to characterize the hydrogen bond (HB) between the -NH moieties of and the anions PF and ClO , whereas Se NMR spectroscopy allowed us to characterize the Au-Se bond. Theoretically, the Au-Se and Au-C orbital interactions have been decomposed using the natural orbital for the chemical valence framework and the bond components quantified through the charge displacement analysis. This methodology provides the quantification of the Dewar-Chatt-Duncanson (DCD) components for the Au-C and Au-Se bonds in the absence and presence of the second-sphere HB. The results presented here show that the anion has a dual mode action: it modifies the conformation of the cation by ion pairing (and this already influences the DCD components) and it induces new polarization effects that depend on the relative anion/cation relative orientation. The perchlorate polarizes , enhancing the Se → Au σ donation and the Au → C back-donation and depressing the C → Au σ donation. On the contrary, the hexafluorophosphate depresses both the Se → Au and C → Au σ donations.
通过结合实验和理论技术，研究了弱相互作用对配合物[(NHC)Au()]（NHC = N - 杂环卡宾； = 硒脲）中给体/反馈给体键成分的影响。具体而言，核磁共振氢谱和脉冲场梯度自旋回波滴定使我们能够表征 中 -NH部分与阴离子PF 和ClO 之间的氢键（HB），而硒核磁共振光谱使我们能够表征Au - Se键。从理论上讲，利用化学价框架的自然轨道对Au - Se和Au - C轨道相互作用进行了分解，并通过电荷位移分析对键成分进行了量化。这种方法提供了在不存在和存在第二配位层氢键的情况下，Au - C和Au - Se键的杜瓦 - 查特 - 邓卡森（DCD）成分的量化。此处给出的结果表明，阴离子具有双重作用模式：它通过离子配对改变阳离子的构象（这已经影响了DCD成分），并且它会诱导取决于阴离子/阳离子相对取向的新的极化效应。高氯酸盐使 极化，增强了Se→Au的σ给体作用和Au→C的反馈给体作用，并抑制了C→Au的σ给体作用。相反，六氟磷酸盐抑制了Se→Au和C→Au的σ给体作用。
