School of Science and Technology, Chemistry Division, University of Camerino, Camerino I-62032, Italy;
Department of Chemistry, University of North Texas, Denton, TX 76203.
Proc Natl Acad Sci U S A. 2017 Jun 27;114(26):E5042-E5051. doi: 10.1073/pnas.1700890114. Epub 2017 Jun 14.
Outer-shell s/p orbital mixing with d orbitals and symmetry reduction upon cupriphication of cyclic trinuclear trigonal-planar gold(I) complexes are found to sensitize ground-state Cu(I)-Au(I) covalent bonds and near-unity phosphorescence quantum yields. Heterobimetallic AuCu {[Au(μ-C,N-EtIm)Cu(µ-3,5-(CF)Pz)], (4a)}, AuCu {[Au(μ-C,N-BzIm)Cu(µ-3,5-(CF)Pz)], (1) and [Au(μ-C,N-MeIm)Cu(µ-3,5-(CF)Pz)], (3a)}, AuCu {[Au(μ-C,N-MeIm)Cu(µ-3,5-(CF)Pz)], (3b) and [Au(μ-C,N-EtIm)Cu(µ-3,5-(CF)Pz)], (4b)} and stacked Au/Cu {[Au(μ-C,N-BzIm)][Cu(µ-3,5-(CF)Pz)], (2)} form upon reacting Au {[Au(μ-C,N-(N-R)Im)] ((N-R)Im = imidazolate; R = benzyl/methyl/ethyl = BzIm/MeIm/EtIm)} with Cu {[Cu(μ-3,5-(CF)Pz)] (3,5-(CF)Pz = 3,5-bis(trifluoromethyl)pyrazolate)}. The crystal structures of 1 and 3a reveal stair-step infinite chains whereby adjacent dimer-of-trimer units are noncovalently packed via two Au(I)⋯Cu(I) metallophilic interactions, whereas 4a exhibits a hexanuclear cluster structure wherein two monomer-of-trimer units are linked by a genuine d-d polar-covalent bond with ligand-unassisted Cu(I)-Au(I) distances of 2.8750(8) Å each-the shortest such an intermolecular distance ever reported between any two d centers so as to deem it a "metal-metal bond" vis-à-vis "metallophilic interaction." Density-functional calculations estimate 35-43 kcal/mol binding energy, akin to typical M-M single-bond energies. Congruently, FTIR spectra of 4a show multiple far-IR bands within 65-200 cm, assignable to as validated by both the Harvey-Gray method of crystallographic-distance-to-force-constant correlation and dispersive density functional theory computations. Notably, the heterobimetallic complexes herein exhibit photophysical properties that are favorable to those for their homometallic congeners, due to threefold-to-twofold symmetry reduction, resulting in cuprophilic sensitization in extinction coefficient and solid-state photoluminescence quantum yields approaching unity (Φ = 0.90-0.97 vs. 0-0.83 for Au and Cu precursors), which bodes well for potential future utilization in inorganic and/or organic LED applications.
外环 s/p 轨道与 d 轨道杂化以及三核三角平面金（I）配合物铜化后的对称性降低被发现可以敏化基态 Cu（I）-Au（I）共价键，并实现近 1 的磷光量子产率。杂金属 AuCu {[Au(μ-C,N-EtIm)Cu(µ-3,5-(CF)Pz)], (4a)}、AuCu {[Au(μ-C,N-BzIm)Cu(µ-3,5-(CF)Pz)], (1) 和 [Au(μ-C,N-MeIm)Cu(µ-3,5-(CF)Pz)], (3a)}、AuCu {[Au(μ-C,N-MeIm)Cu(µ-3,5-(CF)Pz)], (3b) 和 [Au(μ-C,N-EtIm)Cu(µ-3,5-(CF)Pz)], (4b)} 和堆叠的 Au/Cu {[Au(μ-C,N-BzIm)][Cu(µ-3,5-(CF)Pz)], (2)} 通过将 Au {[Au(μ-C,N-(N-R)Im)] ((N-R)Im = 咪唑盐；R = 苄基/甲基/乙基 = BzIm/MeIm/EtIm)} 与 Cu {[Cu(μ-3,5-(CF)Pz)] (3,5-(CF)Pz = 3,5-双（三氟甲基）吡唑盐)} 反应形成。1 和 3a 的晶体结构揭示了阶梯状的无限链，其中相邻的二聚体-of-三聚体单元通过两个 Au（I）⋯Cu（I）金属键合相互作用非共价组装，而 4a 表现出六核簇结构，其中两个单体-of-三聚体单元通过真正的 d-d 极性共价键连接，配体辅助的 Cu（I）-Au（I）距离均为 2.8750(8) Å，这是迄今为止报道的任何两个 d 中心之间最短的此类分子间距离，因此被认为是“金属-金属键”，而不是“金属键合相互作用”。密度泛函计算估计结合能为 35-43 kcal/mol，类似于典型的 M-M 单键能。同样，4a 的 FTIR 光谱在 65-200 cm 内显示出多个远红外带，可归因于 ，这通过晶体距离-力常数相关的 Harvey-Gray 方法和弥散密度泛函理论计算得到了验证。值得注意的是，由于三重态到二重态的对称性降低，这些杂金属配合物表现出有利于其同金属类似物的光物理性质，导致消光系数中的铜亲合敏化和固态光致发光量子产率接近 1（Φ = 0.90-0.97 与 Au 和 Cu 前体的 0-0.83），这为未来在无机和/或有机 LED 应用中的潜在应用提供了良好的前景。
