Light Modulation of Charge Transfer Processes in Inorganic-Organic Materials

在外界刺激(光、电场或磁场)的作用下，磁性、光学和导电性能发生变化的功能材料是非易失性存储技术、自旋电子器件和传感器发展的核心。目前的挑战包括开发可在两种功能状态之间切换的材料，以及用于可扩展存储器和传感器开发的光。我们开发了一种新的策略，通过光学双稳态光致变色的功能化来制备光驱动功能材料。光致变色化合物在基态和亚稳态的电子结构不同的两个态之间进行光诱导异构化。我们已经开发了光致变色螺恶嗪配体，这些配体可以结合到金属中心或结合到有机多发色分子阵列中。一旦结合，光诱导的螺恶嗪结构的变化会导致功能靶成分(金属中心或生色团)的氧化还原电位、基态能量和激发态能量的变化。这样的结构变化可以触发两个有机生色团、有机配体和金属中心之间的能量转移和电荷转移过程，或者两个处于混合价状态的金属中心之间的能量转移和电荷转移过程。我们实验室以前的工作已经证明了电子双稳钴络合物、荧光共轭聚合物纳米粒子和荧光有机二元体中光致色素诱导的电荷转移或能量转移过程的原理证明。在这项建议中，我们描述了旨在了解支配这些现象的基本结构和电子因素、光致变色门控过程的限制以及调节信噪比以优化传感器和存储器应用的光感应门的动力学和热力学因素的实验。

Functional materials that undergo changes in magnetic, optical, and conducting properties upon application of external stimuli (light, electric field, or magnetic field) are central to the development of non-volatile memory technologies, spintronics devices, and sensors. Current challenges involve developing materials that switch between two functional states with light for scalable memory and sensor development. We have developed a novel strategy for light-driven functional materials through functionalization with optically bistable photochromes. Photochromes undergo light-induced isomerization between two states that differ in the electronic structures of their ground and metastable states. We have developed photochromic spirooxazine ligands that can be bound to metal centers or incorporated into organic multichromophoric arrays. Once bound, light-induced changes in spirooxazine structure lead to changes in the redox potential, ground state energies, and excited state energies at the functional target component (metal center or chromophore). Such structural changes can then trigger energy-transfer, and charge-transfer processes between two organic chromophores, organic ligands, and metal centers, or between two metal centers in a mixed valence state. Previous work in our lab has demonstrated proof-of-principle for photochrome-induced charge transfer or energy transfer processes in an electronically bistable cobalt complex, fluorescent conjugated polymer nanoparticles, and fluorescent organic dyads. In this proposal, we describe experiments designed to understand the fundamental structural and electronic factors that govern these phenomena, the limits of photochrome-gated processes, and the kinetic and thermodynamic factors that regulate signal-to-noise ratios for optimizing light-induced gating for sensors and memory applications.