Ru–Zn Heteropolynuclear Complexes Containing a Dinucleating Bridging Ligand: Synthesis, Structure, and Isomerism

Mononuclear complexes in- and out-[Ru­(Cl)­(trpy)­(Hbpp)]+ (in-0, out-0; Hbpp is 2,2′-(1H-pyrazole-3,5-diyl)­dipyridine and trpy is 2,2′:6′,2″-terpyridine)
are used as starting materials for preparation of Ru–Zn heterodinuclear out-{[Ru­(Cl)­(trpy)]­[ZnCl2]­(μ-bpp)} (out-2) and heterotrinuclear in,in- and out,out-{[Ru­(Cl)­(trpy)]2(μ-[Zn­(bpp)2])}2+ (in-3, out-3) constitutional isomers. Further substitution of
the Cl ligand from the former complexes leads to Ru–aqua out,out-{[Ru­(trpy)­(H2O)]2(μ-[Zn­(bpp)2])}4+ (out-4) and the oxo-bridged Ru–O–Ru complex in,in-{[RuIII(trpy)]2(μ-[Zn­(bpp)2(H2O)]­μ-(O)}4+ (in-5). All complexes are thoroughly characterized
by the usual analytical techniques as well as by spectroscopy by means
of UV–vis, MS, and when diamagnetic NMR. CV and DPV are used
to extract electrochemical information and monocrystal X-ray diffraction
to characterize complexes out-2, in-3, out-3, and in-5 in the solid state. Complex out-3 photochemically isomerizes toward in-3, as can be observed by NMR
spectroscopy and rationalized by density functional theory based
calculations.

以内外两种构型的单核配合物[Ru(Cl)(trpy)(Hbpp)]+（分别记为in-0、out-0；其中trpy为2,2′:6′,2″-三联吡啶（2,2′:6′,2″-terpyridine），Hbpp为2,2′-(1H-吡唑-3,5-二基)二吡啶（2,2′-(1H-pyrazole-3,5-diyl)dipyridine)）作为起始原料，用于制备Ru-Zn异双核配合物out-{[Ru(Cl)(trpy)][ZnCl₂](μ-bpp)}（out-2）以及异三核构造异构体in,in-和out,out-{[Ru(Cl)(trpy)]₂(μ-[Zn(bpp)₂])}²⁺（in-3、out-3）。将前述配合物中的Cl配体进一步取代，可得到Ru-水合配合物out,out-{[Ru(trpy)(H₂O)]₂(μ-[Zn(bpp)₂])}⁴⁺（out-4）以及氧桥联Ru-O-Ru配合物in,in-{[Ru(III)(trpy)]₂(μ-[Zn(bpp)₂(H₂O)]μ-(O)}⁴⁺（in-5）。所有配合物均通过常规分析技术，结合紫外-可见（UV–vis）光谱、质谱（MS）及反磁性样品的核磁共振（NMR）光谱进行了全面表征。采用循环伏安法（Cyclic Voltammetry, CV）与差分脉冲伏安法（Differential Pulse Voltammetry, DPV）获取电化学信息，并通过单晶X射线衍射对固态下的out-2、in-3、out-3及in-5配合物进行结构表征。配合物out-3可发生光化学异构化转化为in-3，该过程可通过核磁共振光谱观测到，并可通过基于密度泛函理论（Density Functional Theory, DFT）的计算进行合理解释。