Realizing solution-phase room temperature quantum coherence in a tetrathiafulvalene-based diradicaloid complex

Molecular electron spins are promising candidates as scalable and tunable qubits but often suffer from undesirable decomposition pathways. Furthermore, significant spin-lattice relaxation and nuclear spin-mediated decoherence limit their applications. While advances in the synthesis of new molecular electron spin qubit candidates have led to improved coherence lifetimes, one key question is whether coherence can be maintained under conditions relevant for employment as quantum sensors. Here, we report a luminescent tetrathiafulvalene-based molecular qubit candidate with diradicaloid character centered on a nuclear-spin-free bridging ligand. This unique air- and water-stable scaffold exhibits a long electron spin decoherence time of hundreds of nanoseconds at ambient temperatures and in nuclear-spin-rich protonated solvents. These results distinguish this system as a promising candidate for the development of novel room temperature, solution-phase quantum sensing technologies and suggest that molecular electron spin qubits can be ideal candidates for these applications.