Backbone-integrated triplet radicals in linear 2p-3d-4f heterometallic chains and magnetic hysteresis

Abstract

Radical-based heterometallic systems provide a powerful platform for exploring cooperative magnetic phenomena arising from well-defined spin networks. In particular, linear 2p–3d–4f architectures are attractive because they combine strong radical-mediated exchange with the pronounced magnetic anisotropy of rare-earth ions. However, examples in which all spin centers are fully integrated into the polymer backbone remain extremely rare, and the factors governing the emergence of cooperative magnetic behavior in such systems are still poorly understood. Here we report the single-step synthesis and magnetic characterization of a family of radical-bridged linear 2p–3d–4f coordination polymers constructed from an air-stable triplet biradical. In these coordination polymers, the biradical units function both as efficient bridges and as intrinsic high-spin carriers, enforcing a strictly alternating heterospin architecture along the chain. Magnetic analyses and simulations reveal strong intraligand ferromagnetic coupling within the biradical and dominant antiferromagnetic exchange between the radical and metal ions, leading to ferrimagnetic ground states. A comparison between Mn- and Co-based derivatives demonstrates that cooperative magnetic behavior is highly sensitive to the 3d component. While Mn-containing chains show no slow magnetic relaxation, the Tb–Co derivative exhibits clear magnetic hysteresis below 0.9 K. These findings show that slow magnetic relaxation in 2p–3d–4f radical chains is not governed solely by rare-earth anisotropy but is decisively influenced by the transition-metal ion, providing a new guideline for the design of radical-based magnetic polymers.