Exploration of Zn(II) complexes for efficient phosphorescence and TADF

过渡金属配合物作为发光体的研究对于发展照明和显示技术的高度创新应用具有重要意义。由于电子-空穴-复合过程产生约75%的三重态，因此利用这些态来发光是非常可取的。在过去的十年里，发光的铜(I)配合物经历了凤凰式的崛起，在有机发光器件中有许多概念验证的应用。它们的吸引力主要是因为没有低能的d-d*态，这可能导致非常快的非辐射衰变，而且许多配合物都显示出热激活的延迟荧光，通过热重新布居具有次要荧光的单重态激发态S1→S0，提供了一种绕过自旋禁忌T1→S0跃迁的发射机制。这种机制的优点在于，它消除了强自旋轨道耦合(SOC)的必要性，并极大地增加了总辐射速率常数KR。有趣的是，同样表现出D10电子构型的锌(II)配合物，作为发光体利用磷光或TADF来开发三重态激子的关注很少。基于我们以前在光活性D10过渡金属卡宾配合物方面的研究成果和我们的初步结果，我们的目标是缩小这一差距。这项合作项目提案结合了Steffen小组的合成和光谱专业知识以及MARIAN小组的理论专业知识，通过在不同的配位几何结构中使用不同π受体强度的卡宾配体来开发高效发光的锌(II)配合物，利用三重态激子，通过磷光或TADF，从而使LLCT态和LMCT态具有较强的SOC。我们将研究环境对长寿命激发态性质的影响，建立它们的光动力学激发态行为的理论模型，并展示选定的候选者在第一个概念验证应用中的用途。

The investigation of transition metal complexes as emitters is of fundamental im¬portance for the development of highly innovative applications in lighting and display technology. Because the electron-hole-recombination process produces ca. 75% triplet states, it is highly desirable to exploit these states for luminescence. In the last decade, luminescent Cu(I) complexes have seen a phoenix-like rise, with many proof-of-concept applications in OLEDs. Their attractive¬ness is mainly due to the absence of low-energy d-d* states which could give rise to very fast non-radiative decay and to the fact that many of these complexes show thermally activated delayed fluorescence (TADF), providing an emission mecha¬nism bypassing the spin-forbidden T1→S0 transition by thermal re-population of the singlet excited state S1 with subse¬quent fluorescence S1→S0. The beauty of this mech¬anism is that it re¬moves the necessity of strong spin–orbit coupling (SOC) and greatly increases the overall radiative rate constant kr. Interestingly, Zn(II) complexes, which also exhibit a d10 electron configuration, have received very little attention as emitters to exploit triplet excitons by phosphorescence or TADF. Based on our previous achievements with regard to photoactive d10 transition metal carbene complexes and our preliminary results, we aim to close this gap. This collaborative project proposal combines the synthetic and spectroscopic expertise of the Steffen group and the theoretical expertise of the Marian group to develop Zn(II) complexes for efficient luminescence exploiting triplet excitons, either via phosphorescence or via TADF, by employing carbene ligands of varying π-acceptor strength in various coordination geometries to enable LLCT and LMCT states with strong SOC. We will study environmental influences on the properties of the long-lived excited states, establish theoretical models for their photokinetic excited state behavior, and demonstrate the use of selected candidates in first proof-of-concept applications.