Deterministic Preparation of Intermolecular Spin States Through Collective Light Emission in Copper Porphyrin Aggregates
Year: 2026
Type: preprint
Abstract: The coupling of electron spins in open shell systems drives formation of distinct singlet and triplet states whose transitions possess unique coherence properties relative to those of doublets. Here we show that exchange interactions couple the electron spins on neighboring Cu cations within porphyrins macrocycles that participate in aggregate formation. Following photoexcitation, we find a ‘low field’ EPR signal whose peak position and shape are reproduced by simulations of anti-ferromagnetically coupled electron spins. We use time-resolved light emission and EPR results to propose that this ‘low field’ peak appears due to a singlet to triplet transition that results in selective, deterministic population of the lowest energy state in the coupled spin system. Our results highlight how enhanced radiative relaxation in molecular aggregates ligated with open shell transition metal cations can be used to design the coupled spin states that participate in EPR transitions. This design principle could be used to further extend the use of molecular chromophores in quantum information science and technology applications.
Source: ChemRxiv
Institutions: Argonne National Laboratory, Wayne State University
Language: English
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7223176894