Role of charge transfer in hybridization-induced spin transition in metal-organic molecules

The spin crossover in organometallic molecules constitutes one of the most promising routes towards the realization of molecular spintronic devices. In this paper, we explore the hybridization-induced spin crossover in metal-organic complexes. We propose a minimal many-body model that captures the essence of the spin-state switching, thus providing insight into the underlying physics. Combining the model with density functional theory (DFT), we then study the spin crossover in isomeric structures of Ni-porphyrin (Ni-TPP). We show that metal-ligand charge transfer plays a crucial role in the determination of the spin state in Ni-TPP. Finally, we propose a spin-crossover mechanism based on mechanical strain, which does not require a switch between isomeric structures.