Beldjoudi Yassine, Atilgan Ahmet, Weber Jacob A, Roy Indranil, Young Ryan M, Yu Jierui, Deria Pravas, Enciso Alan E, Wasielewski Michael R, Hupp Joseph T, Stoddart J Fraser
Department of Chemistry, Northwestern University, Evanston, IL, 60208, USA.
Institute for Sustainability and Energy, Northwestern University, Evanston, IL, 60208, USA.
Adv Mater. 2020 Aug;32(32):e2001592. doi: 10.1002/adma.202001592. Epub 2020 Jun 29.
Efficient heterogeneous photosensitizing materials require both large accessible surface areas and excitons of suitable energies and with well-defined spin structures. Confinement of the tetracationic cyclophane (ExBox ) within a nonporous anionic polystyrene sulfonate (PSS) matrix leads to a surface area increase of up to 225 m g in ExBox•PSS. Efficient intersystem crossing is achieved by combining the spin-orbit coupling associated to Br heavy atoms in 1,3,5,8-tetrabromopyrene (TBP), and the photoinduced electron transfer in a TBP⊂ExBox supramolecular dyad. The TBP⊂ExBox complex displays a charge transfer band at 450 nm and an exciplex emission at 520 nm, indicating the formation of new mixed-electronic states. The lowest triplet state (T , 1.89 eV) is localized on the TBP and is close in energy with the charge separated state (CT, 2.14 eV). The homogeneous and heterogeneous photocatalytic activities of the TBP⊂ExBox , for the elimination of a sulfur mustard simulant, has proved to be significantly more efficient than TBP and ExBox , confirming the importance of the newly formed excited-state manifold in TBP⊂ExBox for the population of the low-lying T state. The high stability, facile preparation, and high performance of the TBP⊂ExBox•PSS nanocomposites augur well for the future development of new supramolecular heterogeneous photosensitizers using host-guest chemistry.
高效的异质光敏材料既需要大的可及表面积，又需要具有合适能量且自旋结构明确的激子。将四阳离子环番（ExBox）限制在无孔阴离子聚苯乙烯磺酸盐（PSS）基质中，会使ExBox•PSS的表面积增加高达225 m²/g。通过结合1,3,5,8-四溴芘（TBP）中与Br重原子相关的自旋轨道耦合以及TBP⊂ExBox超分子二元体系中的光致电子转移，可实现高效的系间窜越。TBP⊂ExBox配合物在450 nm处显示电荷转移带，在520 nm处有激基复合物发射，表明形成了新的混合电子态。最低三重态（T₁，1.89 eV）定域在TBP上，且能量与电荷分离态（CT，2.14 eV）相近。TBP⊂ExBox对硫芥模拟物的均相和异相光催化活性已证明比TBP和ExBox显著更高效，这证实了TBP⊂ExBox中新形成的激发态多重态对低能T态布居的重要性。TBP⊂ExBox•PSS纳米复合材料的高稳定性、简便制备方法和高性能预示着利用主客体化学开发新型超分子异质光敏剂的良好前景。
