Transition-Metal Phthalocyanines as Versatile Building Blocks for Molecular Qubits on Surfaces

The search for molecular or colloidal building units capable of autonomously organized configurations has been a long-standing endeavor that has resulted in the development of innovative material categories, such as metal-organic and covalent organic or long-range molecular networks. In particular, the possibility of using molecules on surfaces to create specific architectures, for example, those containing nanostructures of <i>S</i> = 1/2 molecular spin, can enable versatile quantum materials and the exploration of future quantum devices. Transition-metal phthalocyanines are particularly attractive candidates as they are stable molecules that can host spin-bearing transition-metal ions in a planar conjugated ring. Here, we use density functional theory calculations to systematically study electronic and magnetic properties and hyperfine parameters for the whole series of 3<i>d</i> transition-metal atoms. We perform transport simulations of selected qubit candidates to further elucidate their suitability for molecular spin qubits on a surface.