Physical Chemistry Seminar: Luminescent Organic Triplet Diradicals as Optical-Spin Interfaces

Molecular optical-spin interfaces are emerging as promising alternatives to solid state defects such as diamond nitrogen vacancy (NV) centers for quantum information science applications. We will report on a new theory-guided approach to molecular optical-spin interfaces that utilizes two covalently linked luminescent tris(2,4,6-trichlorophenyl)methyl (TTM) radicals to produce a diradical with a triplet ground state. These diradicals have photophysics and spin properties very similar to those of NV centers yet can be spatially arranged at the atomic scale. We have examined these diradicals both in glassy solvents and doped into single crystals of their structurally isomorphous diamagnetic precursors. Optical polarization of the T₀ sublevel of the triplet ground state is achieved by spin-selective excited-state intersystem crossing from the T₊₁ and T_-1 sublevels of the triplet excited state. The triplet ground state as characterized by pulse electron paramagnetic resonance spectroscopy shows spin coherence times of 4 ms at 85 K increasing to 20 ms at 5 K. Also, coherent microwave manipulation of the spin-polarized ground state populations and coherences was demonstrated using optically detected Rabi nutations, Hahn echo formation, and echo decay measurements. This marks an important step towards leveraging the favorable spin relaxation times of organic molecules for applications as quantum sensors.

An apéro will be served after the seminar!