A Holstein-Peierls Approach to Excimer Spectra: The Evolution from Vibronically Structured to Unstructured Emission
A Holstein-Peierls Approach to Excimer Spectra: The Evolution from Vibronically Structured to Unstructured Emission
复制标题
DOI：
10.1021/acs.jpcc.1c10255
复制
发表时间：
2022-03-03
影响因子：
3.7
通讯作者：
Spano, Frank C.
中科院分区：
文献类型：
--
作者：
Bialas, April L.;Spano, Frank C.
准分子的存在，如广泛的、无结构的和红移的发射所揭示的，在许多有机溶液和固相体系中是相当普遍的。多年来，对准分子产生和松弛的基本理论解释引起了极大的兴趣。在这里，一个基于荷尔斯坦-佩尔斯哈密顿量的模型被提出来解释分子二聚体的吸收和光致发光。该模型扩展了Frenkel-charge transfer (CT)-Holstein模型，以便将局部和非局部耦合解释为慢分子间振动模式。模型表明，准分子发射可以通过(1)局部分子间耦合到二聚体CT态或通过(2)非局部Frenkel-CT耦合项诱导。最后，通过结合局部和非局部分子间耦合，成功地再现了两种不同的双（苝二亚胺）共价连接二聚体的测量吸收和准分子发射光谱。从结构化到非结构化准分子发射的演变可能是通过非局部耦合的增加发生的，但也可能是由非绝热CT态的稳定引起的。
The presence of excimers, as revealed by broad, structureless, and red-shifted emission, is quite common in a great many organic solution-and solid-phase systems. A fundamental theoretical account of excimer creation and relaxation has generated enormous interest over the years. Here, a model based on a Holstein-Peierls Hamiltonian is presented to account for absorption and photoluminescence in molecular dimers. The model extends the Frenkel-charge transfer (CT)-Holstein model in order to account for both local and nonlocal coupling to a slow intermolecular vibrational mode. The model shows that excimer emission can be induced either through (1) local intermolecular coupling to the dimer CT states or through (2) the nonlocal Frenkel-CT coupling terms. Finally, by incorporating both the local and nonlocal intermolecular coupling, the measured absorption and excimer emission spectra for a set of two different bis(perylene diimide) covalently linked dimers are successfully reproduced. The evolution from structured to unstructured excimer emission likely occurs via an increase in the nonlocal coupling, but it can also be induced by the stabilization of the diabatic CT state.