O'Shea Joseph M, Yun Young Ju, Jamhawi Abdelqader M, Peccati Francesca, Jiménez-Osés Gonzalo, Ayitou Anoklase Jean-Luc
Department of Chemistry, University of Illinois Chicago, Chicago, Illinois 60607, United States.
Center for Cooperative Research in Biosciences (CIC bioGUNE), Basque Research and Technology Alliance (BRTA), Bizkaia Technology Park, Building 800, Derio 48160, Spain.
J Am Chem Soc. 2025 Jan 8;147(1):1017-1027. doi: 10.1021/jacs.4c14303. Epub 2024 Dec 19.
Donor-acceptor dyads are promising materials for improving triplet-sensitized photon upconversion due to faster intramolecular energy transfer (ET), which unfortunately competes with charge transfer (CT) dynamics. To circumvent the issue associated with CT, we propose a novel purely organic donor-acceptor dyad, where the CT character is confined within the donor moiety. In this work, we report the synthesis and characterization of a stable organic radical donor-triplet acceptor dyad () consisting of the acceptor perylene () linked to the donor (4--carbazolyl-2,6-dichlorophenyl)-bis(2,4,6-trichlorophenyl)methyl radical (). Upon red-excitation of , the doublet emission of the donor () is significantly quenched, and a recorded delayed emission centered at ca. 490 nm was attributed to the fluorescence emission from the acceptor. Time-resolved transient absorption spectroscopy suggests doublet-to-triplet energy transfer (DTET) dynamics from the donor to the acceptor as the time constant τ for the donor transient species decreases from 21.47 ns for the sensitizer to 8.73 ns for dyad. This process is accompanied by the appearance of a long-lived component with τ = 97.06 ns, which we ascribe to the triplet transient of the acceptor . Furthermore, computational results indicate that the DTET is intramolecular as computed spin densities of the quartet state show unpaired electrons of ρ ≈ 1 on the donor and of ρ ≈ 2 on the acceptor . The present study highlights the possibility to employ doublet chromophoric systems for light-harvesting and energy upconversion, which can be further tailored for several optoelectronic applications.
给体-受体二元体系是用于改善三重态敏化光子上转换的有前景的材料，因为其分子内能量转移（ET）更快，不幸的是，这与电荷转移（CT）动力学相互竞争。为了规避与CT相关的问题，我们提出了一种新型的纯有机给体-受体二元体系，其中CT特性被限制在给体部分内。在这项工作中，我们报道了一种稳定的有机自由基给体-三重态受体二元体系（）的合成与表征，该二元体系由与给体（4--咔唑基-2,6-二氯苯基）-双（2,4,6-三氯苯基）甲基自由基（）相连的受体苝（）组成。在对进行红色激发时，给体（）的双重态发射显著猝灭，记录到的以约490 nm为中心的延迟发射归因于受体的荧光发射。时间分辨瞬态吸收光谱表明，从给体到受体存在双重态到三重态的能量转移（DTET）动力学，因为给体瞬态物种的时间常数τ从敏化剂的21.47 ns降至二元体系的8.73 ns。这个过程伴随着出现一个τ = 97.06 ns的长寿命组分，我们将其归因于受体的三重态瞬态。此外，计算结果表明DTET是分子内的，因为四重态态的计算自旋密度显示在给体上ρ ≈ 1的未成对电子和在受体上ρ ≈ 2的未成对电子。本研究突出了采用双重态发色体系进行光捕获和能量上转换的可能性，这可以进一步针对多种光电子应用进行定制。
