Triangulene-based diradicals as a blueprint for molecular quantum platforms with optical addressability and long spin coherence times

• URL: http://arxiv.org/abs/2607.08634v1
• Date: Thu, 09 Jul 2026 16:04:38 GMT
• Title: Triangulene-based diradicals as a blueprint for molecular quantum platforms with optical addressability and long spin coherence times
• Abstract summary: We unravel the electronic structure for triangulene, its aza-cation derivative, and the crystal of 2,6,10-tri-tert-butyl-4,8,12-trimesityl-triangulene.<n>Results advance a unified first-principles theoretical foundation of spin decoherence and spin-selective excited-state processes.
• Score: 38.329708057847306
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: The identification of molecules that combine long spin coherence times and efficient spin-optical interfaces, ideally at room temperature, is pivotal towards the development of molecular quantum technology. By means of advanced first-principles methods, we here unravel the electronic structure for triangulene (1), its aza-cation derivative (2), and the crystal of 2,6,10-tri-tert-butyl-4,8,12-trimesityl-triangulene (3), and show that these organic diradicals possess a triplet ground state well separated from the first singlet excited state approaching 0.5 eV, closely resembling solid-state defects like nitrogen vacancy centers. In addition, we compute spin decoherence times due to the interaction with phonons and surrounding nuclear spins, showing that a deuterated molecule of 3 in a nuclear spin-free environment would support $T_2 = 0.21$ ms at 10 K. Importantly, we show that the engineering of specific low-energy vibrations could significantly improve $T_2$ toward the limit imposed by the molecular core spin relaxation, here estimated to be as long as $T_1=27$ ms at 300 K for 2. Finally, we compute two-phonon contributions to inter-system crossing at 300 K for2 as a luminescent prototype, and find that it is highly spin-selective, supporting the possibility to engineer optical read out and spin initialization. These results advance a unified first-principles theoretical foundation of spin decoherence and spin-selective excited-state processes and point to novel chemical design strategies for optically addressable, highly coherent molecular qubits.

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