d -Orbital Orientation-Governed Room-Temperature Magnetism in Charge Transfer Cocrystals

Abstract The design of molecular magnets with programmable spin states at room temperature is challenging for quantum materials. Although organic charge transfer (CT) cocrystals offer a promising framework for tuning spin states through electronic coupling, the deliberate design of donor (D)-acceptor (A) pairs and based on orbital-regulation strategy to mediate effective magnetic interactions has remained unexplored. Here we prove that CT cocrystals provide a platform where metal orbital characteristics govern magnetic strength, while the ordered CT lattice mediates long-range exchange interactions to support collective magnetic ordering. We obtained C60-H2TPP, C60-CuTPP, C60-CoTPP with successively increasing ferromagnetism at 300 K. Through orbital-regulation strategy, the substitution of metal ion Cu2+ with Co2+ precisely reorients the unpaired electron orbital from an alignment parallel to the donor molecule plane to one that points directly toward the C60 molecule. This spatial orientation leads to a significant enhancement in saturation magnetization, revealing that the orbital orientation of the D and A molecules can systematically govern the ferromagnetic ground state in cocrystals. Our results support orbital-regulation strategy as an effective design principle for room-temperature molecular magnets, with implications for spintronic applications based on organic quantum materials.