A Gold(I) Mononuclear Complex and Its Association into Binuclear and Cluster Compounds by Hydrogen Bonding or Metal Ion Coordination

The mononuclear Au(I) complex, Au(Spy)(PPh2py) (1), has been synthesized and characterized structurally. The
complex possesses the expected linear coordination geometry with a S−Au−P bond angle of 176.03(6)° and no
evidence of aurophilic interactions between nearest neighbor Au(I) ions in the solid state. Protonation of the
pendant pyridyl groups of 1 leads to the formation of the H-bonded dimer [{Au(SpyH)(PPh2py)}2](PF6)2 (2),
which has also been structurally characterized. A linear coordination geometry at the Au(I) ions in 2 with a
S−Au−P bond angle of 173.7(2)° is augmented by evidence of a strong aurophilic interaction with a Au···Au
distance of 2.979(1) Å. The pendant pyridyl groups of 1 have also been used to bind Cu(I) by reactions with
[Cu(NCMe)4](PF6) and Cu(P(p-tolyl)3)2(NO3) leading to the formation of the heterobimetallic complexes [{AuCu(μ-Spy)(μ-PPh2py)}2](PF6)2 (3) and [AuCu(P(p-tolyl)3)2(μ-Spy)(μ-PPh2py)](NO3) (4), respectively. A structure
determination of 3 reveals a tetranuclear complex composed of two AuCu(μ-Spy)(μ-PPh2py)+ units held together
by bridging thiolate ligands. A strong metal−metal interaction is noted between the two different d10 ions with
nearest Au−Cu distances averaging 2.6395 Å. The S−Au−P bond angles in 3 deviate slightly from linearity due
to the Au···Cu interactions, while the coordination geometries at Cu(I) are distorted tetrahedral consisting of the
two pyridyl nitrogen atoms, a bridging thiolate sulfur, and the interacting Au(I) ion. While mononuclear complex
1 is only weakly emissive in the solid state and in fluid solution, complexes 2−4 show stronger photoluminescence
in the solid state and rigid media at 77 K, and in fluid solution. The emission maxima for 2−4 in ambient
temperature fluid solution are 470, 635, and 510 nm, respectively. A tentative assignment of the emitting state as
a S(pπ) → Au LMCT transition is made on the basis of previous studies of Au(I) thiolate phosphine complexes.
Shifts of λem result from the influence of H bonding or Cu(I) coordination on the filled thiolate orbital energy, or
on the effect of metal−metal interaction on the Au(I) acceptor orbital energy. Crystal data for Au(Spy)(PPh2py)
(1):  triclinic, space group P1̄ (No. 2), with a = 8.3975(4) Å, b = 11.0237(5) Å, c = 12.4105(6) Å, α = 98.6740(10)°, β = 105.3540(10)°, γ = 110.9620(10)°, V = 995.33(8) Å3, Z = 2, R1 = 3.66% (I > 2σ(I)), wR2 = 9.04%
(I > 2σ(I)) for 2617 unique reflections. Crystal data for [{Au(SpyH)(PPh2py)}2](PF6)2 (2):  triclinic, space group
P1̄ (No. 2), with a = 14.0284(3) Å, b = 14.1093(3) Å, c = 15.7027(2) Å, α = 97.1870(10)°, β = 96.5310(10)°,
γ = 117.1420(10)°, V = 2692.21(9) Å3, Z = 2, R1 = 7.72% (I > 2σ(I)), wR2 = 15.34% (I > 2σ(I)) for 5596
unique reflections. Crystal data for [{AuCu(μ-Spy)(μ-PPh2py)}2](PF6)2 (3):  monoclinic, space group P21/c (No.
14), with a = 19.6388(6) Å, b = 16.3788(4) Å, c = 17.2294(5) Å, β = 91.48°, V = 5540.2(3) Å3, Z = 4, R1 =
3.99% (I > 2σ(I)), wR2 = 8.38% (I > 2σ(I)) for 10597 unique reflections.

单核Au(I)配合物Au(Spy)(PPh₂py)（1）已被合成并完成结构表征。该配合物呈现预期的直线型配位几何构型，S−Au−P键角为176.03(6)°，固态下未观测到邻近Au(I)离子间存在亲金相互作用（aurophilic interactions）。

对配合物1的悬挂吡啶基进行质子化，得到氢键结合的二聚体[{Au(SpyH)(PPh₂py)}₂](PF₆)₂（2），该产物同样完成了结构表征。配合物2中的Au(I)离子仍保持直线型配位几何构型，S−Au−P键角为173.7(2)°，同时存在强亲金相互作用，Au···Au间距为2.979(1) Å。

配合物1的悬挂吡啶基还可通过与[Cu(NCMe)₄](PF₆)和Cu(P(p-甲苯基)₃)₂(NO₃)反应，分别结合Cu(I)，得到异双金属配合物[{AuCu(μ-Spy)(μ-PPh₂py)}₂](PF₆)₂（3）和[AuCu(P(p-甲苯基)₃)₂(μ-Spy)(μ-PPh₂py)](NO₃)（4）。

对配合物3的结构解析表明，其为四核配合物，由两个AuCu(μ-Spy)(μ-PPh₂py)⁺单元通过桥联硫配体桥联形成。两种不同的d¹⁰离子间存在强金属-金属相互作用，邻近Au−Cu的平均间距为2.6395 Å。

由于Au···Cu相互作用，配合物3中的S−Au−P键角略微偏离直线型；而Cu(I)的配位几何为扭曲四面体构型，由两个吡啶氮原子、一个桥联硫配体的硫原子以及与之相互作用的Au(I)离子共同构成。

尽管单核配合物1在固态和流体溶液中仅表现出弱发光，但配合物2~4在固态、77 K下的刚性介质以及流体溶液中均展现出更强的光致发光（photoluminescence）性能。

配合物2~4在室温流体溶液中的发射峰波长分别为470 nm、635 nm和510 nm。基于此前对Au(I)硫醇膦配合物的研究，我们将其发射态初步归属为S(pπ)→Au LMCT（配体到金属电荷转移，ligand-to-metal charge transfer）跃迁。发射波长λem的位移源于氢键或Cu(I)配位对硫醇盐填充轨道能级的影响，或是金属-金属相互作用对Au(I)受体轨道能级的影响。

配合物Au(Spy)(PPh₂py)（1）的晶体学数据：三斜晶系，空间群P1̄（编号2），晶胞参数a=8.3975(4) Å，b=11.0237(5) Å，c=12.4105(6) Å，α=98.6740(10)°，β=105.3540(10)°，γ=110.9620(10)°，晶胞体积V=995.33(8) ų，Z=2；对于2617个独立衍射点，R1=3.66%（I>2σ(I)），wR2=9.04%（I>2σ(I)）。

配合物[{Au(SpyH)(PPh₂py)}₂](PF₆)₂（2）的晶体学数据：三斜晶系，空间群P1̄（编号2），晶胞参数a=14.0284(3) Å，b=14.1093(3) Å，c=15.7027(2) Å，α=97.1870(10)°，β=96.5310(10)°，γ=117.1420(10)°，晶胞体积V=2692.21(9) ų，Z=2；对于5596个独立衍射点，R1=7.72%（I>2σ(I)），wR2=15.34%（I>2σ(I)）。

配合物[{AuCu(μ-Spy)(μ-PPh₂py)}₂](PF₆)₂（3）的晶体学数据：单斜晶系，空间群P21/c（编号14），晶胞参数a=19.6388(6) Å，b=16.3788(4) Å，c=17.2294(5) Å，β=91.48°，晶胞体积V=5540.2(3) ų，Z=4；对于10597个独立衍射点，R1=3.99%（I>2σ(I)），wR2=8.38%（I>2σ(I)）。