Single-Carbon Bridged Pentacene Dimers Enable Efficient Singlet Fission and Quintet State Stabilization
Journal
Journal of the American Chemical Society
Journal Volume
148
Journal Issue
4
Start Page
4062
End Page
4073
ISSN
0002-7863
1520-5126
Date Issued
2026-01-23
Author(s)
Hsu, Chao-Hsien
Liao, Yi-Ching
Cheng, Chu-Chun
Wu, Bo-Han
Yang, Chou-Hsun
Hsu, Chao-Ping
Chen, Bo-Han
Yang, Shang-Da
Hsu, Yuling
Chu, Li-Kang
Chiang, Yun-Wei
Abstract
Singlet fission (SF) offers a promising avenue for quantum information science, as it generates spin-entangled triplet pairs with quintet character (5TT) upon photoexcitation, enabling access to multilevel spin qubit states beyond the traditional two-level systems. However, the 5TT state often decays via several pathways: (1) dissociation into isolated triplets; (2) triplet–triplet annihilation back into the singlet manifold; or (3) spin conversion to lower-multiplicity triplet pair states. These competing relaxation channels pose a major challenge for stabilizing 5TT. Here, we introduce a novel molecular design that prolongs 5TT lifetime by anchoring two pentacene chromophores to the same carbon (C9) position of a fluorene bridge, yielding FlePc2 and FlePhPc2. This single-point attachment enforces a near-parallel intramolecular geometry, promoting strong through-space spin interactions that hinder dissociation. Field-swept electron spin echo (FS-ESE) measurements reveal dominant 5TT signals, indicative of suppressed relaxation pathways. Theoretical calculations predict a substantial binding energy for the reported dimers, accompanied by significant spin density delocalization across both pentacenes, thereby rationalizing 5TT stabilization. These findings establish a molecular design principle for kinetically trapping high-spin multiexciton states, paving the way for spin-based quantum technologies.
Publisher
American Chemical Society (ACS)
Type
journal article