Magnet Creation by Guest Insertion into a Paramagnetic Charge-Flexible Layered Metal-Organic Framework.

Changing nonmagnetic materials to spontaneous magnets is an alchemy-inspiring concept in materials science; however, it is not impossible. Here, we demonstrate chemical modification from a nonmagnet to a bulk magnet of either a ferrimagnet or antiferromagnet, depending on the adsorbed guest molecule, in an electronic-state-flexible layered metal-organic framework, [{Ru ₂ (2,4-F ₂ PhCO ₂ ) ₄ } ₂ TCNQ(EtO) ₂ ] ( 1 ; 2,4-F ₂ PhCO ₂ ^- = 2,4-difluorobenzoate; TCNQ(EtO) ₂ = 2,5-diethoxy-7,7,8,8-tetracyanoquinodimethane). The guest-free paramagnet 1 undergoes a thermally driven intralattice electron transfer involving a structural transition at 380 K. This charge modification can also be implemented by guest accommodations at room temperature; 1 adsorbs several organic molecules, such as benzene (PhH), p -xylene (PX), 1,2-dichloroethane (DCE), dichloromethane (DCM), and carbon disulfide (CS ₂ ), forming 1-solv with intact crystallinity. This induces an intralattice electron transfer to produce a ferrimagnetically ordered magnetic layer. According to the interlayer environment tuned by the corresponding guest molecule, the magnetic phase is consequently altered to a ferrimagnet for the guests PhH, PX, DCE, and DCM or an antiferromagnet for CS ₂ . This is the first demonstration of the postsynthesis of bulk magnets using guest-molecule accommodations.