Spin dynamics and quantum coherence in vanadium(IV) sandwich complexes

This work investigates the spin dynamics and quantum coherence of three vanadium(IV) sandwich complexes as prospective molecular spin qubits. Using single-crystal X-ray diffraction, continuous-wave and pulsed EPR, ENDOR spectroscopy, and DFT calculations, we examine how ⁵¹V hyperfine coupling and restricted ring rotation affect their relaxation behavior. All three complexes display robust quantum coherence, with phase-memory and spin-lattice relaxation times at 5 K comparable to those previously reported for titanium(III) analogues. Their structural differences have only a limited influence on spin relaxation. In addition, the vanadium compounds are air-stable in the solid state, easier to handle, sublimable, and redox-robust. These properties should favor preservation of the V(IV) oxidation state during deposition on surfaces, making the complexes promising candidates for single-molecule addressing and future molecular quantum technologies.