Variable dual luminescence in d/f hybrid complexes by control of energy transfer

通过控制能量转移实现 d/f 杂化复合物的可变双发光

• 批准号: EP/H004645/1
• 负责人: Mike Ward
• 金额: $ 39.39万
• 依托单位: University of Sheffield
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2009
• 资助国家: 英国
• 起止时间: 2009 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FH004645%2F1
• 关键词: Variable; dual; luminescence; hybrid; complexes

Luminescent molecules (i.e. that emit light) are used in a wide variety of applications, two of the most important being display devices (organic light-emitting diodes, or OLEDS) and as sensors (where the intensity / colour of the emitted light is sensitive to the presence of a particular species being analysed). In virtually all cases the luminescent compounds contain one slight-emitting centre such that a single colour of light is emitted. This means, for example, that white-light displays need to contain a mixture of red/blue/green-emitting compounds which may slowly degrade at different rates or have different sensitivity to temperature, making it very difficult to get clear white luminescence.This proposal is to make a series of complexes that contain (i) a blue- or green-emissive transition metal fragment based on Ir(III) or Pt(II); (ii) a red-emissive lanthanide fragment based on Eu(III); and (iii) a conjugated bridge connecting them. The principle of operation will be that light is absorbed selectively by the transition metal fragment, which will have the usual intense charge-transfer absorptions in the UV and visible region, whereas the Eu(III) fragment does not absorb light. This will generate the excited state of the transition metal unit which will collapse partly with emission of blue/green light (radiative decay) and partly by transferring its excitation energy through the bridging ligand to the Eu(III) unit which will in turn generate red luminescence. The balance between the two luminescence components (blue/green and red) will depend very precisely on how efficient the energy-transfer step is: if it is slow, blue/green luminescence from the transition metal will dominate because only a small proportion of the Eu(III) centres will be excited by energy-transfer. If energy-transfer is fast, there will be little blue/green luminescence but mostly red luminescence as nearly all of the excitation energy will be transferred to the Eu(III) centre. Thus the colour of the luminescence can be fine-tuned by controlling the degree of energy-transfer along the bridging ligand. This can be done by one of two mechanisms: controlling the degree of twist between two phenyl rings, which will modify the electronic coupling between the metal termini; or altering the excited-state energy of the transition metal component using the phenomena of solvatochromism or metallochromism. Such control and variability of the colour of luminescence from a single molecule in this way is in itself novel and has many possible applications. For example, carefully-balanced contribution from the two components will allow white-light generation (combination of red and blue/green in the correct proportions) form a single molecule, a result which offers substantial advantages in the preparaton of white-luminescent display devices. In addition, the ability to modulate the blue/green and red luminescence components will allow the complexes to be used as ratiometric sensors, in which the balance between the components at different wavelengths depends on the presence or absence of a metal ion which either varies the twist angle of the conformationally flexible bridge, or alters the energy of the transition metal component via the metallochromic effect, in either case controlling the energy-transfer event. The result will be that the presence of specific metal ions results in an obvious colour change over a wide range from blue to red in the visible region of the spectrum, which is exceptionally easy to detect.In conclusion a combination of synthesis, detailed photophysical studies, and computational studies on energy-transfer will be used to develop switchable dual-emissive complexes with potential applications as both white-light emitters in OLEDS, and two-colour ratiometric sensors, based on the same underlying control of transition-metal to lanthanide energy-transfer through the bridging ligand.

发光分子（即发光分子）用于各种各样的应用，其中最重要的两个是显示设备（有机发光二极管或oled）和传感器（其中发射光的强度/颜色对被分析的特定物种的存在很敏感）。在几乎所有的情况下，发光化合物都含有一个轻微的发光中心，这样就发出了一种颜色的光。这意味着，例如，白光显示器需要包含红/蓝/绿发射化合物的混合物，这些化合物可能会以不同的速度缓慢降解，或者对温度的敏感度不同，因此很难获得清晰的白光。本提案是制作一系列包含(i)基于Ir（III）或Pt（II）的蓝色或绿色发射过渡金属碎片的配合物；（ii）基于Eu（III）的红色发射镧系元素碎片；(3)连接它们的共轭桥。其工作原理是过渡金属碎片选择性地吸收光，它在紫外和可见光区具有通常的强烈的电荷转移吸收，而Eu（III）碎片不吸收光。这将产生过渡金属单元的激发态，该单元的坍塌部分是通过发射蓝/绿光（辐射衰变），部分是通过将其激发能通过桥接配体转移到Eu（III）单元，从而产生红光。两种发光成分（蓝/绿和红）之间的平衡将非常精确地取决于能量转移步骤的效率：如果它缓慢，过渡金属发出的蓝/绿色发光将占主导地位，因为只有一小部分Eu（III）中心会被能量转移激发。如果能量转移快，则很少有蓝色/绿色发光，而主要是红色发光，因为几乎所有的激发能都将转移到Eu（III）中心。因此，可以通过控制沿桥接配体的能量转移程度来微调发光的颜色。这可以通过以下两种机制之一来实现：控制两个苯环之间的扭转程度，这将改变金属端之间的电子耦合；或利用溶剂变色或金属变色现象改变过渡金属组分的激发态能。这种对单个分子发光颜色的控制和变化本身是新颖的，并且有许多可能的应用。例如，仔细平衡两种成分的贡献将允许白光产生（红和蓝/绿以正确的比例组合）形成单个分子，这一结果在制备白光显示设备方面提供了实质性的优势。此外，调节蓝/绿和红发光组分的能力将允许配合物用作比率传感器，其中不同波长组分之间的平衡取决于金属离子的存在或不存在，金属离子要么改变构象柔性桥的扭曲角度，要么通过金属致变色效应改变过渡金属组分的能量，在任何一种情况下控制能量转移事件。结果是，特定金属离子的存在将导致光谱可见区域从蓝色到红色的广泛范围内的明显颜色变化，这是非常容易检测到的。总之，结合合成、详细的光物理研究和能量转移的计算研究将用于开发可切换的双发射配合物，这些配合物具有潜在的应用，既可以作为oled中的白光发射器，也可以作为双色比例传感器，其基础是通过桥接配体对过渡金属到镧系元素的能量转移进行相同的潜在控制。

项目成果

Sensitisation of Eu(III)- and Tb(III)-based luminescence by Ir(III) units in Ir/lanthanide dyads: evidence for parallel energy-transfer and electron-transfer based mechanisms.

• DOI: 10.1039/c4dt00292j
• 发表时间: 2014-04
• 期刊: Dalton transactions
• 影响因子: 4
• 作者: Daniel Sykes;Ahmet J. Cankut;N. M. Ali;A. Stephenson;Steven J. P. Spall;S. Parker;J. Weinstein;M. Ward