Quantum spin coherence and electron spin distribution channels in vanadyl-containing lantern complexes

Abstract

We herein investigate the heterobimetallic lantern complexes [PtVO(SOCR)₄] as charge neutral electronic qubits based on vanadyl complexes (S = 1/2) with nuclear spin-free donor atoms. The derivatives with R = Me (1) and Ph (2) give highly resolved X-band EPR spectra in frozen CH₂Cl₂/toluene solution, which evidence the usual hyperfine coupling with the ⁵¹V nucleus (I = 7/2) and an additional superhyperfine interaction with the I = 1/2 nucleus of the ¹⁹⁵Pt isotope (natural abundance ca. 34%). DFT calculations ascribe the spin density delocalization on the Pt²⁺ ion to a combination of π and δ pathways, with the former representing the predominant channel. Spin relaxation measurements in frozen CD₂Cl₂/toluene-d₈ solution between 90 and 10 K yield T_m values (1–6 μs in 1 and 2–11 μs in 2) which compare favorably with those of known vanadyl-based qubits in similar matrices. Coherent spin manipulations indeed prove possible at 70 K, as shown by the observation of Rabi oscillations in nutation experiments. The results indicate that the heavy Group 10 metal ion is not detrimental to the coherence properties of the vanadyl moiety and that Pt–VO lanterns can be used as robust spin-coherent building blocks in materials science and quantum technologies.