CAREER: Optically-Driven Spin Polarization of Coordination Complexes

Researchers from the University of Pittsburgh will develop new molecular systems capable of optically induced spin polarization for applications in quantum information science. A central challenge in deploying molecules as quantum bits (qubits) is the ability to reliably place a qubit into a well-defined initial state, a process called initialization. Conventional initialization of molecular spin relies on low temperatures and high magnetic fields, which are costly and technically demanding. The research team will design and synthesize transition metal coordination complexes whose interaction with circularly polarized light can be used to achieve spin polarization through a technique called optically induced magnetization (OIM). Their discoveries could establish general molecular design principles for optically initializable qubits, advancing the role of chemistry in quantum computing and sensing technologies. The project will also include development of freely accessible online educational resources on symmetry and magnetism for graduate and undergraduate students and thereby contribute to the development of quantum information science workforce. The research program pursues three coordinated aims. In the first aim, coordination complexes of d- and f-block metals will be synthesized and characterized, with the goal of maximizing their magnetic circular dichroism (MCD) responses as a predictor of OIM efficiency. Design criteria focus on molecules with axial symmetry, optical transitions involving orbitally degenerate excited states, and spin-orbit coupling (SOC) splittings comparable to or exceeding the electronic transition linewidth, while simultaneously avoiding ground-state orbital angular momentum to preserve spin coherence. In the second aim, hybrid metal-radical complexes will be prepared to spatially separate the locus of ground-state spin density from the heavy metal center responsible for SOC-driven excited-state splitting, offering a strategy to simultaneously optimize spin coherence and OIM response. In the third aim, time-resolved magnetic optical rotatory dispersion spectroscopy will be developed at the nanosecond timescale to directly observe and characterize OIM following circularly polarized optical excitation. Together, these aims will deliver fundamental insight into the interplay of molecular symmetry, spin-orbit coupling, and magneto-optical phenomena, and will advance OIM as a practical initialization method for molecular spin qubits. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.