Hintze Christian, Korf Patrick, Degen Frank, Schütze Friederike, Mecking Stefan, Steiner Ulrich E, Drescher Malte
Fachbereich Chemie, Universität Konstanz , 78457 Konstanz, Germany.
J Phys Chem Lett. 2017 Feb 2;8(3):690-695. doi: 10.1021/acs.jpclett.6b02869. Epub 2017 Jan 24.
In this work, the triplet state delocalization in a series of monodisperse oligo(p-phenyleneethynylene)s (OPEs) is studied by pulsed electron paramagnetic resonance (EPR) and pulsed electron nuclear double resonance (ENDOR) determining zero-field splitting, optical spin polarization, and proton hyperfine couplings. Neither the zero-field splitting parameters nor the optical spin polarization change significantly with OPE chain length, in contrast to the hyperfine coupling constants, which showed a systematic decrease with chain length n according to a 2/(1 + n) decay law. The results provide striking evidence for the Frenkel-type nature of the triplet excitons exhibiting full coherent delocalization in the OPEs under investigation with up to five OPE repeat units and with a spin density distribution described by a nodeless particle in the box wave function. The same model is successfully applied to recently published data on π-conjugated porphyrin oligomers.
在这项工作中，通过脉冲电子顺磁共振（EPR）和脉冲电子核双共振（ENDOR）研究了一系列单分散的聚对苯撑乙炔（OPE）中的三重态离域，确定了零场分裂、光自旋极化和质子超精细耦合。与超精细耦合常数不同，零场分裂参数和光自旋极化均不会随OPE链长而发生显著变化，超精细耦合常数根据2/(1 + n)衰减定律随链长n呈系统性下降。这些结果为三重态激子的弗伦克尔型性质提供了显著证据，在所研究的具有多达五个OPE重复单元且自旋密度分布由盒中无节点粒子波函数描述的OPE中，三重态激子表现出完全相干离域。同一模型成功应用于最近发表的关于π共轭卟啉低聚物的数据。
