Photophysical Properties of Pt(II) Polypyridines with Five-versus Six Membered Chelate Rings: Trade-Offs in Angle Strain
Photophysical Properties of Pt(II) Polypyridines with Five-versus Six Membered Chelate Rings: Trade-Offs in Angle Strain
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DOI：
10.1021/acs.inorgchem.8b00636
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发表时间：
2018-06-04
影响因子：
4.6
通讯作者：
McMillin, David R.
中科院分区：
文献类型：
--
作者：
Natoli, Sean N.;Hight, Lauren M.;McMillin, David R.
本文报道了八个[铂(NNN)X](+)配合物的合成和表征，其中三齿NNN配体为(2，2‘-联吡啶-6-基)(吡啶-N-基)硫化物(BTP)或甲基(2，2’-联吡啶-6-y1)(吡啶-2-基)胺(BMAP)，X为OMe、Cl、苯乙炔(C2Ph)或环己基乙炔(C2Cy)。人们期望在2，2‘：6’，2“-三联吡啶(TrPy)的主链上插入一个杂原子，可以扩大其整体的排列和咬合角，将ILCT特性引入激发态，并改善其光物理性质。[PT(BMAP)C_2Ph]+和[PT(BTP)C_1](+)的晶体结构表明，原子插入TrPy主链后，配体的咬合角增加了8-10。然而，对光物理的影响是微乎其微的。事实上，在所研究的八个体系中，只有[Pt(BMAP)C，Ph]+和[Pt(Btp)C2Ph](+)配合物在流体溶液中显示出明显的发射，并且它们的发射寿命比[Pt(Trpy)C2Ph](+)短。一个原因是铂和插入的杂原子的键角偏好导致六元环偏离平面性，采用船形构象，削弱了配体内的电荷离域。此外，角应变导致铂周围的施主原子呈伪四面体排列，通过d-d激发态促进失活，抵消了由于总咬合角增加而带来的任何好处。结果表明，为了提高[Pt(Nnn)X](+)体系的发光性能，必须注意避免用一种角应变来换取另一种角应变。
This report describes the synthesis and characterization of a series of eight [Pt(NNN)X](+) complexes where the tridentate NNN ligand is (2,2'-bipyrid-6-yl)(pyrid- N 2-yl)sulfide (btp) or methyl(2,2'-bipyrid-6-y1)(pyrid-2-yl)amine (bmap) and X is OMe, Cl, phenylethynyl (C2Ph), or cyclohexylethynyl (C2Cy). The expectation was that inserting a heteroatom into the backbone of 2,2':6',2"-terpyridine (trpy) would expand the overall intraligand bite angle, introduce ILCT character into the excited states, and improve the photophysical properties. Crystal structures of [Pt(bmap)C2Ph]+ and [Pt(btp) C1](+) reveal that atom insertion into the trpy backbone successfully expands the bite angle of the ligand by 8-10. However, the impact on the photophysics is minimal. Indeed, of the eight systems investigated, only the [Pt(bmap)C,Ph]+ and [Pt(btp) C2Ph](+) complexes display appreciable emission in fluid solution, and they exhibit shorter emission lifetimes than [Pt(trpy)C2Ph](+). One reason is that the bond angle preferences of platinum and the inserted heteroatom induce the six membered rings to deviate from planarity and adopt a boat -like conformation, impairing charge delocalization within the ligand. In addition, angle strain induces the donor atoms about platinum to assume a pseudotetrahedral arrangement, which offsets any benefit due to the increase in overall bite angle by promoting deactivation via d d excited states. The results reveal that, in order to improve the luminescence of a [Pt(NNN)X](+) system, one must take care to avoid trading one kind of angle strain for another.