Grieco Christopher, Kennehan Eric R, Rimshaw Adam, Payne Marcia M, Anthony John E, Asbury John B
Department of Chemistry, The Pennsylvania State University , State College, Pennsylvania 16801, United States.
Department of Chemistry, University of Kentucky , Lexington, Kentucky 40506, United States.
J Phys Chem Lett. 2017 Dec 7;8(23):5700-5706. doi: 10.1021/acs.jpclett.7b02434. Epub 2017 Nov 9.
Ultrafast vibrational spectroscopy in the mid-infrared spectral range provides the opportunity to probe the dynamics of electronic states involved in all stages of the singlet fission reaction through their unique vibrational frequencies. This capability is demonstrated using a model singlet fission chromophore, 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-Pn). The alkyne groups of the TIPS side chains are coupled to the conjugated framework of the pentacene cores, enabling direct examination of the dynamics of triplet excitons that have successfully separated from correlated triplet pair states in crystalline films of TIPS-Pn. Relaxation processes during the separation of triplet excitons and triplet-triplet annihilation after their separation result in the formation of hot ground state molecules that also exhibit unique vibrational frequencies. Because all organic molecules possess native vibrational modes, ultrafast vibrational spectroscopy offers a new approach to examine the dynamics of electronic intermediates that may inform ongoing efforts to utilize singlet fission to overcome thermalization losses in photovoltaic applications.
中红外光谱范围内的超快振动光谱提供了一个机会，通过其独特的振动频率来探测单重态裂变反应各个阶段所涉及的电子态动力学。使用模型单重态裂变发色团6,13-双（三异丙基甲硅烷基乙炔基）并五苯（TIPS-Pn）证明了这种能力。TIPS侧链的炔基与并五苯核心的共轭骨架相连，从而能够直接研究在TIPS-Pn晶体薄膜中已成功从相关三重态对态分离的三重态激子的动力学。三重态激子分离过程中的弛豫过程以及它们分离后的三重态-三重态湮灭导致形成也具有独特振动频率的热基态分子。由于所有有机分子都具有固有振动模式，超快振动光谱提供了一种新方法来研究电子中间体的动力学，这可能为目前利用单重态裂变来克服光伏应用中的热化损失的努力提供信息。
