Room-Temperature Optical Spin Polarization of an Electron Spin Qudit in a Vanadyl-Free Base Porphyrin Dimer
Alberto Privitera, Alessandro Chiesa, Fabio Santanni, Angelo Carella, Davide Ranieri, Andréa Caneschi, Matthew D. Krzyaniak, Ryan M. Young, Michael R. Wasielewski, Stefano Carretta, Roberta Sessoli
Abstract
High Resolution Image Download MS PowerPoint Slide Photoexcited organic chromophores appended to molecular qubits can serve as a source of spin initialization or multilevel qudit generation for quantum information applications. So far, this approach has been primarily investigated in chromophore–stable radical systems. Here, we extend this concept to a meso-meso linked oxovanadium(IV) porphyrin–free-base porphyrin dimer. Femtosecond transient absorption experiments reveal that photoexcitation of the free-base porphyrin leads to picosecond triplet state formation via enhanced intersystem crossing. Time-resolved electron paramagnetic resonance (TREPR) experiments carried out at both 85 K and room temperature reveal the formation of a long-lived spin-polarized quartet state through triplet–doublet spin mixing. Notably, a distinct hyperfine structure arising from the interaction between the electron spin quartet state and the vanadyl nucleus ( 51 V, I = 7/2) is evident, with the quartet state showing long-lived spin polarization even at room temperature. Theoretical simulations of the TREPR spectra confirm the photogenerated quartet state and provide insights into the non-Boltzmann spin populations. Exploiting this phenomenon affords the possibility of using photoinduced triplet states in porphyrins for quantum information as a resource to polarize and magnetically couple molecular electronic or nuclear spin qubits and qudits.