Deposition of an Addressable Molecular Spin Qubit with Built-In Decoupling Structure

The integration of molecular spin qubits in the next generation of quantum devices requires magnetic centers that can be individually addressed while remaining decoupled from the substrate. Envisioning this future perspective here, we introduce a heterobimetallic molecular design strategy that integrates a paramagnetic vanadyl spin center with a built-in inorganic decoupling unit within a single coordination complex, overcoming conventional approaches that rely on inorganic buffer layers such as MgO and thereby limit versatility and scalability. The lantern complex [PtVO(SOCPh)₄] (PtVO) embeds a VO²⁺ qubit spatially shielded by a square-planar PtS₄ moiety eliminating the need for external decoupling layers. A submonolayer of PtVO was successfully deposited on a highly oriented pyrolytic graphite substrate via electrospray deposition, yielding a chemically intact and well-defined molecular interface. Combining element and polarization-resolved synchrotron spectroscopies, supported by density functional theory calculations, demonstrates that the vanadyl center remains magnetically isolated at the submonolayer limit. Polarization- and angular-dependent X-ray absorption spectroscopy, flanked by multiplet ligand field theory simulations, provided detailed insight into the adsorption geometry and the electronic structure of PtVO upon deposition. Angular-dependent X-ray magnetic circular dichroism further reveals how the molecular coordination geometry governs the orbital contributions and magnetic anisotropy of square-pyramidal vanadyl systems. These results establish a built-in molecular decoupling system as a viable chemical principle for the scalable integration of addressable molecular spin qubits on low-dimensional materials, paving the way to new routes toward surface-based quantum architectures.