Department of Chemistry , Mississippi State University , Mississippi State , Mississippi 39762 , United States.
Department of Chemistry , Xihua University , Chengdu 610039 , China.
J Phys Chem B. 2018 Sep 6;122(35):8429-8438. doi: 10.1021/acs.jpcb.8b05965. Epub 2018 Aug 28.
With their unique photochemical properties, porphyrins have remained for decades the most interested chemicals as photonic materials for applications ranging from chemistry, biology, medicine, to photovoltaic. Porphyrins can self-assemble into higher order structures. However, information has been scant on the kinetics and structural evolution during porphyrin assembly and disassembly. Furthermore, quantitative understanding of the porphyrin optical activities is complicated by the complex interplay of photon absorption, scattering, and fluorescence emission that can concurrently occur in porphyrin samples. Using meso-tetrakis(4-sulfonatophenyl)porphyrin as the model molecule, reported herein is a combined UV-vis extinction, polarized Stokes-shifted fluorescence, and polarized resonance synchronous spectroscopic (PRS2) study of porphyrin assembly and disassembly in acidic solutions. Although porphyrin assembly and disassembly occur instantaneously upon the sample preparation, both processes last at least a few months before reaching their approximate equilibrium states. The two processes were monitored in situ by quantifying the porphyrin fluorescence and scattering depolarizations as well as its extinction, absorption, scattering, and fluorescence emission cross sections. In addition to a series of new insights to the porphyrin assembly and disassembly, the methodology described in this work opens the door for the in situ study of the structural and optical properties of photonic materials comprising molecular assembly.
卟啉因其独特的光化学性质，几十年来一直是最受关注的光子材料化学物质，其应用范围涵盖化学、生物、医学和光伏等领域。卟啉可以自组装成更高阶的结构。然而，关于卟啉组装和拆卸过程中的动力学和结构演变的信息仍然很少。此外，由于卟啉样品中可能同时发生光子吸收、散射和荧光发射等复杂的相互作用，定量理解卟啉的光学活性变得很复杂。本文以间四(4-磺酸钠苯基)卟啉为模型分子，报道了在酸性溶液中卟啉组装和拆卸的紫外可见消光、偏振斯托克斯位移荧光和偏振共振同步光谱（PR2S）的联合研究。尽管卟啉组装和拆卸在样品制备后瞬间发生，但这两个过程至少需要几个月才能达到其近似平衡状态。通过定量测定卟啉荧光和散射去偏振以及消光、吸收、散射和荧光发射截面，对这两个过程进行了原位监测。除了对卟啉组装和拆卸的一系列新见解外，本工作中描述的方法为包括分子组装在内的光子材料的结构和光学性质的原位研究开辟了道路。
