Construction of an Artificial Ferrimagnetic Lattice by Lithium Ion Insertion into a Neutral Donor/Acceptor Metal–Organic Framework

Abstract

Construction of am olecular system in which the magnetic lattice exhibits long-range order is one of the fundamental goals in materials science.I nt his study,w e demonstrate the artificial construction of aferrimagnetic lattice by doping electrons into acceptor sites of an eutral donor/ acceptor metal-organic framework (D/A-MOF). This doping was achieved by the insertion of Li-ions into the D/A-MOF, which was used as the cathode of aL i-ion battery cell. The neutral D/A-MOF is al ayered system composed of ac arboxylate-bridged paddlewheel-type diruthenium(II,II) complex as the donor and aTCNQ derivative as the acceptor.The ground state of the neutral form was am agnetically disordered paramagnetic state.U pon dischargeo ft he cell, spontaneous magnetization was induced;t he transition temperature was variable.T he stability of the magnetically ordered lattice depended on the equilibrium electric potential of the D/A-MOF cathode,which reflected the electron-filling level.Over the past few decades,t he design of molecule-based magnets with long-range magnetic order has attracted much interest in the field of molecular functional materials.[1] One route to achieve such long-range magnetic order is to construct lattices using only paramagnetic metal ions and/or molecules with the help of superexchange coupling between paramagnetic centers via ab ridging ligand. Charge-transfer (CT) framework systems comprising electron donor (D) and electron acceptor (A) + located between layers.[4]Focusing on the generation of the radical AC À in the D 0 2 A 0 system, electron-filling control of the system should be an effective approach for the construction of an artificial magnetically ordered lattice without intra-lattice ET.T aking into account that the present "MOFs" are also characterized as atype of porous frameworks,the electrochemical insertion of ionic guests such as Li + and Na + into host frameworks is potentially applicable for electron-filling control of D/AMOFs.[5] In the process of electrochemical cation insertion, acation and electron pair is introduced into the host material and the valence of the redox-active species (that is,t he acceptor A 0 )i nt he material is directly modulated from A À -filled forms are expected to be paramagnetic, ferrimagnetic, and paramagnetic, respectively.