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。我们的研究开发和使用理论和计算方法来理解和预测分子结构和性质。过度强调的是激发的电子态，它与实验观测值有关（例如，1-或多光子吸收、光发射、光化学.）。然而，研究的问题和应用是多样的：（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DNA和RNA的天然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，需要荧光核碱基类似物，因为它们的天然对应物是非荧光的，因此不能用于直接观察DNA和RNA的结构、功能和动力学。对于这两类探针，有迅速发展的研究超越单光子吸收到双光子或三光子吸收，因为使用的波长更长，可以更深的穿透，并允许更好的聚焦，这是活细胞或生物体成像的关键需求。然而，相应的计算研究却滞后于实验发展。这项研究旨在填补这一空白。总体而言，生物探针中的多光子过程的多样性将被检查，以更好地理解潜在的生物物理学，合理化结构和生物物理学性质之间的联系，并协助设计新的改进的探针专门用于多光子应用的目标。(2)最近合成了一些新的含碲和铋的磷光化合物，而不是昂贵的过渡金属，并进行了表征。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量子物理学的基本理解，包括关于为什么化合物是磷光的定性想法，但详细的理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，这将导致对导致更高（或更低）量子产率的因素的更好理解，即，更好或更差的材料。通过对已知化合物性质的这些模拟，我们可以合理地设计具有改进的光谱特性的新材料。(3)我们将开发和应用研究大气化学和天体化学小分子量子动力学的方法。

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.