Magnetic Sponge Behavior via Electronic State Modulations

Abstract

A reversible magnetic change in response to external stimuli is a desired function of molecular magnetic materials. The magnetic change induced by a change in the intrinsic spin is significant because the magnetic change is inevitable and could become drastic. In this study, we demonstrate a reversible magnetic change closely associated with electronic state modulations, as well as structural modifications realized by solvation/desolvation cycles of a magnetic sponge. The compound was a DA-type layered magnet, [{Ru(OCPh-2,3,5-Cl)}(TCNQMe)]·4DCM (1; 2,3,5-ClPhCO = 2,3,5-trichlorobenzoate; TCNQMe = 2,5-dimethyl-7,7,8,8-tetracyanoquinodimethane; DCM = dichloromethane), where [Ru(OCPh-2,3,5-Cl)] ([Ru]) is an electron donor (D) and TCNQMe is an electron acceptor (A). Compound 1 had a one-electron-transferred, charge-ordered state with a [{Ru}-TCNQMe-{Ru}] (1e-I) formula. Strong intralayer antiferromagnetic couplings between [Ru] with S = 1 or [Ru] with S = 3/2 and TCNQMe with S = 1/2, as well as ferromagnetic interlayer interactions, induced long-range ferrimagnetic ordering at T = 101 K. Interstitial DCM molecules were located between layers, and these were gradually eliminated under vacuum at 80 °C to form a solvent-free compound (1-dry) without loss of crystallinity. The electronic state of 1-dry thermally fluctuated and eventually provided a charge-disproportionate disordered state, with a [{Ru}-TCNQMe-{Ru}] (1.5e-I) formula as the ground state. The T in 1-dry was 34 K because of the presence of diamagnetic TCNQMe in some parts of the framework. A large T variation with Δ T ≈ 70 K was switchable; switching was achieved by charge-state modulations accompanied by subtle structural modifications in solvation/desolvation treatments.

Host–Guest Hydrogen Bonding Varies the Charge‐State Behavior of Magnetic Sponges

“…[1][2][3][4][5] This is because molecular magnets possess acharacteristic flexibility not only in their structures [6,7] but also in their electronic/spin states and electronic/magnetic correlation. [10][11][12] To obtain such chargeflexible magnets,w eh ave focused on ac lass of magnetic metal-organic frameworks comprising electron-donor (D) and -acceptor (A) compositions (D/A-MOFs), [13,14] where the ET or charge transfer (CT) was regulated not only by the choice of the D/A units,but also by the bonding nature of the frameworks and/or the packing mode. [10][11][12] To obtain such chargeflexible magnets,w eh ave focused on ac lass of magnetic metal-organic frameworks comprising electron-donor (D) and -acceptor (A) compositions (D/A-MOFs), [13,14] where the ET or charge transfer (CT) was regulated not only by the choice of the D/A units,but also by the bonding nature of the frameworks and/or the packing mode.…”

“…[8,9] Hence,t he modulation of the intrinsic spin state in ac orrelated lattice would be an efficient strategy for adrastic and huge change of magnetism, which could be designed by controlling the intralattice electron transfer (ET). [12,15] In our molecular design, carboxylate-bridged paddlewheel-type diruthenium-(II,II) complexes ([Ru 2 II,II ]) and 7,7,8,8-tetracyano-p-quinodimethane derivatives (TCNQR x )h ave been employed as the Da nd A, respectively,tocontrol the degree of D!ACTby chemically modifying D/A units in several types of frameworks. [12,15] In our molecular design, carboxylate-bridged paddlewheel-type diruthenium-(II,II) complexes ([Ru 2 II,II ]) and 7,7,8,8-tetracyano-p-quinodimethane derivatives (TCNQR x )h ave been employed as the Da nd A, respectively,tocontrol the degree of D!ACTby chemically modifying D/A units in several types of frameworks.…”

“…[10][11][12] To obtain such chargeflexible magnets,w eh ave focused on ac lass of magnetic metal-organic frameworks comprising electron-donor (D) and -acceptor (A) compositions (D/A-MOFs), [13,14] where the ET or charge transfer (CT) was regulated not only by the choice of the D/A units,but also by the bonding nature of the frameworks and/or the packing mode. [16][17][18] In the family of D 2 A-type layers,f ive distinct types of charge-ordered states have been characterized so far; the neutral state (N;D 0 2 A 0 ), [19] the one-electron-transferred state (1e-I;D 0.5+ 2 A À ), [20] the two-electron-transferred state (2e-I;D + 2 A 2À ), [21] and two types of partial-electron-transferred state (1.5e-I;D 0.75+ 2 A 1.5À )w ith ac harge-disproportionated ordered form (1.5e-I o ) [22] and ad isordered form (1.5e-I d ) [12] (Scheme 1). [16][17][18] In the family of D 2 A-type layers,f ive distinct types of charge-ordered states have been characterized so far; the neutral state (N;D 0 2 A 0 ), [19] the one-electron-transferred state (1e-I;D 0.5+ 2 A À ), [20] the two-electron-transferred state (2e-I;D + 2 A 2À ), [21] and two types of partial-electron-transferred state (1.5e-I;D 0.75+ 2 A 1.5À )w ith ac harge-disproportionated ordered form (1.5e-I o ) [22] and ad isordered form (1.5e-I d ) [12] (Scheme 1).…”

“…[12,15] In our molecular design, carboxylate-bridged paddlewheel-type diruthenium-(II,II) complexes ([Ru 2 II,II ]) and 7,7,8,8-tetracyano-p-quinodimethane derivatives (TCNQR x )h ave been employed as the Da nd A, respectively,tocontrol the degree of D!ACTby chemically modifying D/A units in several types of frameworks. [12,15,23] Herein, we report au nique D 2 A-layered compound, [{Ru 2 (m-FPhCO 2 ) 4 } 2 TCNQ(OMe) 2 ]·nDCE (1-nDCE; m-FPhCO 2 À = m-fluorobenzoate;T CNQ(OMe) 2 = 2,5-dimethoxyl-7,7,8,8-tetracyanoquinodimethane;D CE = 1,2dichloroethane), which adopts three types of charge-ordered states depending on the degree of solvation of DCE, that is, nDCE:2e-I for the fully solvated compound (pristine form; 1-4DCE), 1.5e-I d for the solvent-free compound (1), and 1e-I for apartially solvated intermediate state (1-DCE with n 1) ( Figure 1a). Inspired by the superior flexibility of the charge state in our D/A-MOFs,the chemi-or physisorption of guest molecules into ap orous D/A-MOF (that is,p seudopolymorphs) could bring about amodulation of charge states in the host framework, consequently resulting in ad rastic magnetic change.…”

“…[8,9] Hence,t he modulation of the intrinsic spin state in ac orrelated lattice would be an efficient strategy for adrastic and huge change of magnetism, which could be designed by controlling the intralattice electron transfer (ET). [10][11][12] To obtain such chargeflexible magnets,w eh ave focused on ac lass of magnetic metal-organic frameworks comprising electron-donor (D) and -acceptor (A) compositions (D/A-MOFs), [13,14] where the ET or charge transfer (CT) was regulated not only by the choice of the D/A units,but also by the bonding nature of the frameworks and/or the packing mode. [12,15] In our molecular design, carboxylate-bridged paddlewheel-type diruthenium-(II,II) complexes ([Ru 2 II,II ]) and 7,7,8,8-tetracyano-p-quinodimethane derivatives (TCNQR x )h ave been employed as the Da nd A, respectively,tocontrol the degree of D!ACTby chemically modifying D/A units in several types of frameworks.…”