Syntheses and Luminescent Properties of 3,5-Diphenylpyrazolato-Bridged Heteropolynuclear Platinum Complexes. The Influence of Chloride Ligands on the Emission Energy Revealed by the Systematic Replacement of Chloride Ligands by 3,5-Dimethylpyrazolate

Heteropolynuclear PtII complexes with 3,5-diphenylpyrazolate
[Pt2Ag4(μ-Cl)2(μ-Ph2pz)6] (3), [Pt2Ag2Cl2(μ-Ph2pz)4(Ph2pzH)2] (4), [Pt2Cu2Cl2(μ-Ph2pz)4(Ph2pzH)2] (5), [Pt2Ag4(μ-Cl)­(μ-Me2pz)­(μ-Ph2pz)6] (7), and [Pt2Ag4(μ-Me2pz)2(μ-Ph2pz)6] (8) have been prepared and structurally characterized. These
complexes are luminescent except for 5 in the solid state
at an ambient temperature with emissions of red-orange (3), orange (4), yellow-orange (7), and green
(8) light, respectively. Systematic red shift of the
emission energies with the number of chloride ligands was observed
for 3, 7, and 8. DFT calculations
indicate that the highest occupied molecular orbital (HOMO) as well
as HOMO-1 of the heterohexanuclear complexes, 3, 7, and 8, having Pt2Ag4 core, mainly consist of dδ orbital of PtII and
π orbitals of Ph2pz ligands, while the lowest unoccupied
molecular orbital (LUMO) of these complexes mainly consists of in-phase
combination of 6p of two PtII centers and 5p of four AgI centers. It is likely that the emissions of 3, 7, and 8 are attributed to emissive states
derived from the Pt2(d)/π → Pt2Ag4 transitions, the emission energy of which depends
on the ratio of chloride ligands to pyrazolate ligands.

以3,5-二苯基吡唑根（3,5-diphenylpyrazolate）为配体的异多核铂(II)配合物：[Pt₂Ag₄(μ-Cl)₂(μ-Ph₂pz)₆] (3)、[Pt₂Ag₂Cl₂(μ-Ph₂pz)₄(Ph₂pzH)₂] (4)、[Pt₂Cu₂Cl₂(μ-Ph₂pz)₄(Ph₂pzH)₂] (5)、[Pt₂Ag₄(μ-Cl)(μ-Me₂pz)(μ-Ph₂pz)₆] (7) 以及 [Pt₂Ag₄(μ-Me₂pz)₂(μ-Ph₂pz)₆] (8) 已被成功合成并完成结构表征。在室温固态条件下，除配合物5外，其余配合物均表现出发光特性：配合物3发射红橙色光、配合物4发射橙色光、配合物7发射黄橙色光、配合物8发射绿色光。针对配合物3、7、8的观测显示，其发射能量随氯离子配体数目增加呈现系统性红移现象。密度泛函理论（Density Functional Theory, DFT）计算结果表明，带有Pt₂Ag₄金属核的异六核配合物3、7、8的最高占据分子轨道（Highest Occupied Molecular Orbital, HOMO）及HOMO-1主要由铂(II)的dδ轨道与Ph₂pz配体的π轨道构成；而该类配合物的最低未占据分子轨道（Lowest Unoccupied Molecular Orbital, LUMO）则主要由两个铂(II)中心的6p轨道与四个银(I)中心的5p轨道经同相组合而成。推测配合物3、7、8的发光源于Pt₂(d)/π → Pt₂Ag₄的跃迁发射态，其发射能量取决于氯离子配体与吡唑根配体的比例。