Multiphonon Relaxation in Molecular Lanthanoid Luminescence

分子化合物中激发能级的非辐射失活是由电子态和振动泛音（=多声子弛豫，MR）的相互作用引起的，是发光系统光物理中最基本的现象之一。最有趣的一类发光体，通过非谐，高能振荡器严重阻碍MR是分子镧系元素复合物，发射光谱的近红外区（约。650-2000 nm）。尽管近红外发光在生物医学成像或光学电信等领域具有巨大的技术潜力，但对这些物种中确定MR的复杂性的详细经验和理论理解仍处于起步阶段。目前的建议旨在缓解这种情况，通过发展一个全面的了解MR分子镧系元素发光。其实现的关键使能方法是立体化学上明确定义的镧系元素络合物的有机合成，所述镧系元素络合物用较重的同位素系统地标记（例如C-D而不是C-H）。这些量身定制的同位素模型系统允许定量的关键参数MR诱导的配体中的典型结构基序。特别是，该项目需要确定溶液中的3D复杂结构（顺磁1H NMR），非辐射失活率（时间分辨发光光谱）和各种耦合振荡器片段的振动泛音特性（近红外吸收光谱），然后在非辐射跃迁的感应共振机制的已知理论框架下整合所有经验数据。所期望的突破性的，统一的理解MR的高能量，非谐振子将远远超出目前的最先进的和补充的谐波，低能量振荡器在分子电子物理学的所有领域的众所周知的能隙定律。

Non-radiative deactivation of excited levels in molecular compounds by the interaction of electronic states and vibrational overtones (= multiphonon relaxation, MR) is one of the most fundamental phenomena in the photophysics of light-emitting systems. One of the most interesting class of luminophores that are severely hampered by MR via anharmonic, high-energy oscillators are molecular lanthanoid complexes that emit in the near-infrared region of the spectrum (ca. 650-2000 nm). A detailed empirical and theoretical understanding of the intricacies determining MR in these species is still in its very infancy despite of the great technological potential of near-IR luminescence in areas like biomedical imaging or optical telecommunication. The current proposal aims at alleviating this situation by developing a comprehensive understanding of MR in molecular lanthanoid luminescence. The key enabling methodology for its realization is the organic synthesis of stereochemically well defined lanthanoid complexes which are systematically labeled with heavier isotopes (e.g. C-D instead of C-H). These tailor-made, isotopologic model systems allow the quantification of critical parameters for MR induced by typical structural motifs in the ligands. In particular, the project entails the determinations of the 3D complex structures in solution (paramagnetic 1H NMR), the non-radiative deactivation rates (time-resolved luminescence spectroscopy) and the vibrational overtone properties (near-IR absorption spectroscopy) of various coupled oscillator fragments, followed by integration of all empirical data under the known theoretical framework of the inductive-resonant mechanism of non-radiative transitions. The desired groundbreaking, unified understanding of MR for high-energy, anharmonic oscillators would go far beyond the current state-of-the-art and complement the well-known energy gap law for harmonic, low-energy oscillators in all areas of molecular photophysics.