Synthesis, Structure, And Photophysical Properties Of Pt(Ⅱ) Complexes With Tetrazole-based Terdentate Chelates

In this thesis, we have designed and synthesized six terdentate chelating ligandscontaining the tetrazolyl group and twelve terdentate Pt(II) complexes by using the2,2′-bipyridine and4,4′-dimethyl-2,2′-bipyridine as two starting materials. The structuralfeatures and photophysical peoperties of these terdentate Pt(II) complexes have beencharacterized by single-crystal X-ray diffraction, UV-vis absorption spectroscopy, IRspectroscopy, HNMR spectroscopy, fluorescence spectroscopy, and TD-DFT caculations.1. Takeing the2,2′-bipyridine and4,4′-dimethyl-2,2′-bipyridine as raw materials, wedesigned and synthesized two NH-based terdentate chelating ligands (tbpyH=6-(1H-tetrazol-5-yl)-2,2′-bipyridine and tmbpyH=6-(1H-tetrazol-5-yl)-4,4′-dimethyl-2,2′-bipyridine) and their corresponding mononuclear platinum(II) chloride compounds,Pt(tbpy)Cl (1) and Pt(tmbpy)Cl (2). X-ray structural analysis of2reveales that the tbpyH andtmbpyH act as the mono-anionic ligands (N^N^N￣) via direct deprotonation of thetetrazolyl-NH, and adopts a distorted N3Cl square-planar geometry. Complex2presents azigzag head-to-tail stacking array along the a axis with weak intermolecular Pt···Pt and π···πinteractions. When introduceing substituents (methyl) on the2,2′-bipyridine fragment, notonly can significantly improve the solubilities of the resulting Pt(II) complexes, but also canmodulate their photophysical properties.2. Using the two tetrazole-based terdentate chelating ligands (tbpyH and tmbpyH) above,through the N-alkylation reaction, we designed and synthesized four N-alkylationtetrazole-based bipyridine terdentate chelating ligands:6-(1-ethyl-5-tetrazolyl)-4,4′-dimethyl-2,2′-bipyridine (etmbpy),6-(1-hexyl-5-tetrazolyl)-4,4′-dimethyl-2,2′-bipyridine (htmbpy),6-(1-hexyl-5-tetrazolyl)-2,2′-bipyridine (htbpy),6-(1-ethyl-5-tetrazolyl)-2,2′-bipyridine)(etbpy). Their corresponding cationic mono-platinum(II) chloride compounds,[Pt(etmbpy)Cl]BF4(3),[Pt(htmbpy)Cl]BF4(4),[Pt(htbpy)Cl]BF4(5),[Pt(etbpy)Cl]BF4(6)and [Pt(htbpy)Cl]PF6(7) have also been synthesized. It is revealed that the N-alkylation of thetetrazolyl ring can remarkably increased the solubilities of Pt(II) chloride complexes, thechange of outermost anion and alky group all have big influences on the photophysicalproperties of the Pt(II) chloride complexes.3. With the N-alkylation Pt(II) chloride complexes as building block units, and using the pyrazole ligands which not only can act as monodentate ligands but also have bidentatebridging function. We synthesized a mononuclear Pt(II) pyrazole compound,[Pt(etmbpy)(dbpzH)](BF4)2(8), and four dinuclear Pt(II) pyrazole compounds,{[Pt(etmbpy)]2(u-pz)}(BF4)3(9),{[(Pt(htmbpy)]2(u-pz)}(BF4)3(10),{[(Pt(htbpy)]2(u-pz)}(BF4)3(11),{[Pt(etbpy)]2(u-pz)}(BF4)3(12). The mononuclear complex8is non-emissive both in solutionand in the solid state, while the dinuclear complexes9–12are emissive in the solid state.