Department of Chemistry, University of South Alabama, Mobile, Alabama 36688, United States.
Inorg Chem. 2011 Mar 21;50(6):2199-206. doi: 10.1021/ic101836a. Epub 2011 Feb 9.
The syntheses are reported for two novel Tb(3+) heterotrimetallic cyanometallates, K(2)[Tb(H(2)O)(4)(Pt(CN)(4))(2)]Au(CN)(2)·2H(2)O (1) and [Tb(C(10)N(2)H(8))(H(2)O)(4)(Pt(CN)(4))(Au(CN)(2))]·1.5C(10)N(2)H(8)·2H(2)O (2) (C(10)N(2)H(8) = 2,2'-bipyridine). Both compounds have been isolated as colorless crystals, and single-crystal X-ray diffraction has been used to investigate their structural features. Crystallographic data (MoKα, λ = 0.71073 Å, T = 290 K): 1, tetragonal, space group P4(2)/nnm, a = 11.9706(2) Å, c = 17.8224(3) Å, V = 2553.85(7) Å(3), Z = 4; 2, triclinic, space group P1, a = 10.0646(2) Å, b = 10.7649(2) Å, c = 17.6655(3) Å, α = 101.410(2)°, β = 92.067(2)°, γ = 91.196(2)°, V = 1874.14(6) Å(3), Z = 2. For the case of 1, the structure contains Au(2)Pt(4) hexameric noble metal clusters, while 2 includes Au(2)Pt(2) tetrameric clusters. The clusters are alike in that they contain Au-Au and Au-Pt, but not Pt-Pt, metallophilic interactions. Also, the discrete clusters are directly coordinated to Tb(3+) and sensitize its emission in both solid-state compounds, 1 and 2. The Photoluminescence (PL) spectra of 1 show broad excitation bands corresponding to donor groups when monitored at the Tb(3+) ion f-f transitions, which is typical of donor/acceptor energy transfer (ET) behavior in the system. The compound also displays a broad emission band at ∼445 nm, assignable to a donor metal centered (MC) emission of the Au(2)Pt(4) clusters. The PL properties of 2 show a similar Tb(3+) emission in the visible region and a lack of donor-based emission at room temperature; however, at 77 K a weak, broad emission occurs at 400 nm, indicative of uncoordinated 2,2'-bipyridine, along with strong Tb(3+) transitions. The absolute quantum yield (QY) for the Tb(3+) emission ((5)D(4) → (7)F(J (J = 6-3))) in 1 is 16.3% with a lifetime of 616 μs when excited at 325 nm. In contrast the weak MC emission at 445 nm has a quantum yield of 0.9% with a significantly shorter lifetime of 0.61 μs. For 2 the QY value decreases to 9.3% with a slightly shorter lifetime of 562 μs. The reduced QY in 2 is considered to be a consequence of (1) the slightly increased donor-acceptor excited energy gap relative to the optimal gap suggested for Tb(3+) and (2) Tb(3+) emission quenching via a bpy ligand-to-metal charge transfer (LMCT) excited state.
报告了两种新型 Tb(3+) 杂三聚氰根合金属配合物的合成，K(2)[Tb(H(2)O)(4)(Pt(CN)(4))(2)]Au(CN)(2)·2H(2)O(1)和[Tb(C(10)N(2)H(8))(H(2)O)(4)(Pt(CN)(4))(Au(CN)(2))]·1.5C(10)N(2)H(8)·2H(2)O(2)(C(10)N(2)H(8)=2,2'-联吡啶)。这两种化合物都被分离为无色晶体，并使用单晶 X 射线衍射来研究它们的结构特征。晶体学数据（MoKα，λ=0.71073 Å，T=290 K）：1，四方晶系，空间群 P4(2)/nnm，a=11.9706(2)Å，c=17.8224(3)Å，V=2553.85(7)Å(3)，Z=4；2，三斜晶系，空间群 P1，a=10.0646(2)Å，b=10.7649(2)Å，c=17.6655(3)Å，α=101.410(2)°，β=92.067(2)°，γ=91.196(2)°，V=1874.14(6)Å(3)，Z=2。对于 1，结构包含 Au(2)Pt(4) 六聚体贵金属簇，而 2 包含 Au(2)Pt(2) 四聚体簇。这些簇相似之处在于它们包含 Au-Au 和 Au-Pt，但不包含 Pt-Pt，金属亲合相互作用。此外，离散的簇直接与 Tb(3+)配位，并在固态化合物 1 和 2 中敏化其发射。1 的光致发光（PL）光谱显示出与供体基团相对应的宽激发带，当在 Tb(3+)离子 f-f 跃迁处监测时，这是系统中供体/受体能量转移（ET）行为的典型特征。该化合物还在约 445nm 处显示出宽发射带，可归因于 Au(2)Pt(4)簇的供体金属中心（MC）发射。2 的 PL 性质在可见光区域显示出相似的 Tb(3+)发射，并且在室温下缺乏基于供体的发射；然而，在 77 K 时，在 400nm 处发生弱的、宽的发射，表明存在未配位的 2,2'-联吡啶，以及强的 Tb(3+)跃迁。1 中 Tb(3+)发射（(5)D(4)→(7)F(J(J=6-3)))的绝对量子产率（QY）为 16.3%，寿命为 616μs，激发波长为 325nm。相比之下，在 445nm 处的弱 MC 发射具有 0.9%的量子产率，寿命明显更短，为 0.61μs。对于 2，QY 值降低到 9.3%，寿命略短于 562μs。认为 2 中的 QY 降低是由于（1）相对于建议的 Tb(3+)最佳能隙，供体-受体激发能隙略有增加，（2）Tb(3+)通过 bpy 配体到金属电荷转移（LMCT）激发态发射猝灭。
