Isocyanide Ligands Promote Ligand-to-Metal Charge Transfer Excited States in a Rhenium(II) Complex
Isocyanide Ligands Promote Ligand-to-Metal Charge Transfer Excited States in a Rhenium(II) Complex
复制标题
异氰化物配体促进铼(II)配合物中配体到金属的电荷转移激发态
DOI：
10.1021/acs.inorgchem.2c03193
复制
发表时间：
2023
影响因子：
4.6
通讯作者：
Dempsey, Jillian L.
中科院分区：
文献类型：
--
作者：
Rodriguez, Tayliz M.;Deegbey, Mawuli;Chen, Chun-Hsing;Jakubikova, Elena;Dempsey, Jillian L.
研究了六芳基异氰配合物[Re（CNAr）6] PF 6（CNAr = 2，6-二甲基苯异氰，λmax= 300 nm）的金属-配体电荷转移.在氧化为[Re（CNAr）6]（PF 6）2时，主要的低能光学跃迁是配体-金属电荷转移（LMCT）和配体内跃迁（λmax= 650 nm）。TD-DFT被用来确定参与LMCT过渡的配体为基础的轨道，揭示了大部分的供体轨道是基于芳基环（85%），而不是CN键（14%）。对于[Re（CNAr）6]+和[Re（CNAr）6]2+，通过X射线衍射的结构表征揭示了在中心Re离子处偏离Ohgeometry，对于Re（II）观察到更大的对称性降低。对于[Re（CNAr）6]+，这些结构变化导致了强ν（C <$N）伸缩（2065 cm-1）的加宽，因为T1 uIR活性模的简并被打破。此外，观察到这种ν（C <$N）拉伸的肩部，这是由于C-N-Ar键偏离线性。而[Re（CNAr）6]2+在ν（C <$N）区有两个弱带（2065和2121 cm-1）。密度泛函理论计算表明，中心离子对称性的降低表现在强度的降低和观察到的ν（C <$N）带的分裂。这两种配合物的稳定性受到光诱导分解的限制，其中Re（I）在照射时解离异氰化物配体，并且Re（II）吸光度在环境光下衰减。这些数据为[Re（CNAr）6]2+的电子结构提供了新的见解，增强了我们对LMCT激发态和异腈配体多功能性的理解。
A metal-to-ligand charge transfer with mixed intraligand character is observed for the rhenium hexakisarylisocyanide complex [Re(CNAr)6]PF6(CNAr = 2,6-dimethylphenylisocyanide, λmax= 300 nm). Upon oxidation to [Re(CNAr)6](PF6)2, the dominant low energy optical transition is a ligand-to-metal charge transfer (LMCT) mixed with intraligand transitions (λmax= 650 nm). TD-DFT was used to identify the participating ligand-based orbitals in the LMCT transition, revealing that the majority of the donor orbital is based on the aryl ring (85%) as opposed to the CN bond (14%). For both [Re(CNAr)6]+and [Re(CNAr)6]2+, structural characterization by X-ray diffraction reveals deviations from Ohgeometry at the central Re ion, with larger reduction in symmetry observed for Re(II). For [Re(CNAr)6]+, these structural changes lead to a broadening of the strong ν(C≡N) stretch (2065 cm–1), as the degeneracy of the T1uIR-active mode is broken. Furthermore, a shoulder is observed for this ν(C≡N) stretch, resulting from deviation of the C–N–Ar bond from linearity. By contrast, [Re(CNAr)6]2+has two weak bands in the ν(C≡N) region (2065 and 2121 cm–1). DFT calculations indicate that reduction of symmetry at the central rhenium ion manifests in the decrease in intensity and the observed split of the ν(C≡N) band. Stability of both complexes are limited by light-induced decomposition where Re(I) dissociates a isocyanide ligand upon irradiation and Re(II) absorbance decays under ambient light. These data provide new insights to the electronic structure of [Re(CNAr)6]2+, enhancing our understanding of LMCT excited states and the versatility of isocyanide ligands.