Photophysical properties of molecules: From biological imaging to new materials

计算研究允许解释现代实验测量。重要的是，可以开发模型来概括观察到的行为，理解相关系统，并设计改进的分子或材料。我们的研究开发并使用理论和计算方法来理解和预测分子的结构和性质。最重要的重点是激发态，它与实验观察（例如，单光子或多光子吸收，光发射，光化学……）有关。然而，研究的问题和应用是多种多样的：(1)在生物成像中，重点是荧光蛋白和荧光核碱基类似物，它们模拟了天然DNA和RNA核碱基构建块的结构和功能。荧光蛋白是分子和细胞生物学中研究生物机制、功能和结构的有用探针。同时，由于天然的核碱基类似物不具有荧光性，不能直接用于观察DNA和RNA的结构、功能和动力学，因此需要荧光核碱基类似物。对于这两类探针，研究正在迅速发展，从单光子吸收转向双光子或三光子吸收，因为使用的波长较长，可以更深地穿透，更好地聚焦，这是活细胞或生物体成像的关键需求。然而，相应的计算研究滞后于实验研究。拟议中的研究旨在填补这一空白。总的来说，为了更好地理解潜在的光物理，理顺结构和光物理性质之间的联系，并协助设计专门用于多光子应用的新型改进探针，我们将研究生物探针中多光子过程的多样性。(2)最近合成并表征了许多新的含碲和铋的磷光化合物，而不是昂贵的过渡金属。磷光是许多技术的基础，包括发光器件（led）。虽然已经通过计算获得了对光物理学的基本理解，包括关于化合物为什么会发出磷光和不发出磷光的定性想法，但要详细了解，需要使用比迄今为止使用的更复杂的量子化学方法。此外，为了理解相对量子产率，将开发新的工具并用于绘制光激发后的弛豫路径，这将有助于更好地理解导致更高（或更低）量子产率的因素，即更好或更差的材料。通过这些已知化合物性质的模拟，我们可以合理地设计具有改进光谱特性的新材料。(3)开发和应用大气化学和天体化学小分子量子动力学研究方法。

Computational study allows the interpretation of modern experimental measurements. Importantly, models can be developed to generalize observed behaviour, understand related systems, and design improved molecules or materials. Our research develops and uses theoretical and computational methods for understanding and predicting molecular structure and properties. The over-arching emphasis is on excited electronic states, which are connected to experimental observables (e.g., 1- or multi-photon absorption, light emission, photochemistry...). However, the problems and applications studied are diverse: (1) In biological imaging, the focus is on both fluorescent proteins and fluorescent nucleobase analogues, which mimic the structure and function of the natural nucleobase building blocks of DNA and RNA. Fluorescent proteins are useful probes of biological mechanisms, functions, and structures in molecular and cell biology. Meanwhile, fluorescent nucleobase analogues are needed because their natural counterparts are non-fluorescent, and thus cannot be used to observe DNA and RNA structure, function, and dynamics directly. For both classes of probes, there is rapidly developing research moving beyond one-photon absorption to two- or three-photon absorption, as the longer wavelengths used permit deeper penetration and allow better focus, which are critical needs for live cell or organism imaging. However, corresponding computational study is lagging behind experimental development. The proposed research aims to fill that gap. Overall, a diversity of multi-photon processes in biological probes will be examined with the goals of a better understanding of the underlying photophysics, rationalizing the connections between structure and photophysical properties, and assisting with the design of new improved probes specifically for multi-photon applications. (2) A number of new phosphorescent compounds containing tellurium and bismuth, rather than expensive transition metals, have recently been synthesized and characterized. Phosphorescence is the basis for many technologies, including light-emitting devices (LEDs). While a basic understanding of the photophysics has been obtained computationally, including qualitative ideas on why compounds are phosphorescent versus non-phosphorescent, a detailed understanding requires the use of more sophisticated quantum chemistry approaches than have been used to-date. Moreover, to understand the relative quantum yields, new tools will be developed and used to map the relaxation pathways following photoexcitation, which will lead to an improved understanding of the factors leading to higher (or lower) quantum yields, i.e., better or worse materials. Through these simulations of the properties of known compounds, we can rationally design new materials with improved spectral characteristics. (3) We will develop and apply methods for studying quantum dynamics in small molecules for atmospheric chemistry and astrochemistry.