Institut für Physikalische und Theoretische Chemie, Universität Regensburg, Universitätstrasse 31, D-93040 Regensburg, Germany.
Inorg Chem. 2011 Sep 5;50(17):8293-301. doi: 10.1021/ic200811a. Epub 2011 Aug 3.
Strongly luminescent neutral copper(I) complexes of the type Cu(pop)(NN), with pop = bis(2-(diphenylphosphanyl)phenyl)ether and NN = bis(pyrazol-1-yl)borohydrate (pz(2)BH(2)), tetrakis(pyrazol-1-yl)borate (pz(4)B), or bis(pyrazol-1-yl)-biphenyl-borate (pz(2)Bph(2)), are readily accessible in reactions of Cu(acetonitrile)(4)(+) with equimolar amounts of the pop and NN ligands at ambient temperature. All products were characterized by means of single crystal X-ray diffractometry. The compounds exhibit very strong blue/white luminescence with emission quantum yields of up to 90%. Investigations of spectroscopic properties and the emission decay behavior in the temperature range between 1.6 K and ambient temperature allow us to assign the emitting electronic states. Below 100 K, the emission decay times are in the order of many hundreds of microseconds. Therefore, it is concluded that the emission stems from the lowest triplet state. This state is assigned to a metal-to-ligand charge-transfer state (3MLCT) involving Cu-3dand pop-π* orbitals. With temperature increase, the emission decay time is drastically reduced, e.g. to 13 μs [corrected] (Cu(pop)-(pz(2)Bph(2))), at ambient temperature. At this temperature, the complexes exhibit high emission quantum yields, as neat material or doped into poly(methyl methacrylate) (PMMA). This behavior is assigned to an efficient thermal population of a singlet state (being classified as (1)MLCT), which lies only 800 to 1300 cm(-1) above the triplet state, depending on the individual complex. Thus, the resulting emission at ambient temperature largely represents a fluorescence. For applications in OLEDs and LEECs, for example, this type of thermally activated delayed fluorescence (TADF) creates a new mechanism that allows to harvest both singlet and triplet excitons (excitations) in the lowest singlet state. This effect of singlet harvesting leads to drastically higher radiative rates than obtainable for emissions from triplet states of Cu(I) complexes.
易于获得的发光中性铜（I）配合物的类型 Cu（pop）（NN），其中 pop = 双（2-（二苯基膦基）苯基）醚和 NN = 双（吡唑-1-基）硼氢化钠（pz（2）BH（2）），四（吡唑-1-基）硼酸盐（pz（4）B），或双（吡唑-1-基）-联苯-硼酸酯（pz（2）Bph（2）），通过 Cu（乙腈）（4）（+）与当量的 pop 和 NN 配体在环境温度下反应。所有产物均通过单晶 X 射线衍射法进行了表征。这些化合物具有非常强的蓝色/白色发光，发射量子产率高达 90%。在 1.6 K 至环境温度范围内的光谱性质和发射衰减行为的研究使我们能够分配发射电子态。在 100 K 以下，发射衰减时间在数百微秒的范围内。因此，可以得出结论，发射源自最低三重态。该状态被分配给涉及 Cu-3d 和 pop-π*轨道的金属-配体电荷转移态（3MLCT）。随着温度的升高，发射衰减时间大大缩短，例如在环境温度下为 13 μs[更正]（Cu（pop）-（pz（2）Bph（2）））。在这个温度下，配合物表现出高的发射量子产率，无论是纯物质还是掺杂到聚甲基丙烯酸甲酯（PMMA）中。这种行为归因于单重态的有效热填充（被归类为（1）MLCT），其仅比三重态高出 800 至 1300 cm（-1），具体取决于单个配合物。因此，在环境温度下的发射主要代表荧光。例如，对于 OLED 和 LEEC 的应用，这种类型的热激活延迟荧光（TADF）创建了一种新的机制，允许在最低单重态中收集单重态和三重态激子（激发）。这种单重态收集的效果导致比从 Cu（I）配合物的三重态获得的辐射率高得多。
