A novel charge-disproportionation state with δ = 0.75 was observed in an electron-donor (D)/-acceptor (A) D(δ+)2A(2δ-) layered framework by chemically tuning the electron-donating affinity of D at the boundary between D(0.5+)2A(-) and D(+)2A(2-) phases, which was pressure-sensitive due to the formation of the D(+)2A(2-) oxidation state.

Phase transitions caused by the charge instability between the neutral and ionic phases of compounds, i.e., N–I phase transitions, provide avenues for switching the intrinsic properties of compounds related to electron/spin correlation and dipole generation as well as charge distribution. However, it is extremely difficult to control the transition temperature (T c) for the N–I phase transition, and only chemical modification based on the original material have been investigated. Here, a design overview of the tuning of N–I phase transition by interstitial guest molecules is presented. This study reports a new chain coordination‐polymer [Ru2(3,4‐Cl2PhCO2)4TCNQ(EtO)2]∙DCE (1‐DCE; 3,4‐Cl2PhCO2 − = 3,4‐dichlorobenzoate; TCNQ(EtO)2 2,5‐diethoxy‐7,7,8,8‐tetracyanoquinodimethane; and DCE = 1,2‐dichloroethane) that exhibits a one‐step N–I transition at 230 K (= T c) with the N‐ and I‐states possessing a simple paramagnetic state and a ferrimagnetically correlated state for the high‐ and low‐temperature phases, respectively. The T c continuously decreases depending on the content of DCE, which eventually disappears with the complete evacuation of DCE, affording solvent‐free compound 1 with the N‐state in the entire temperature range (this behavior is reversible). This is an example of tuning the in situ T c for the N–I phase transition via the control of the interstitial guest molecules.

The donor (D)/acceptor (A) assembly reaction of the paddlewheel-type diruthenium(II,II) complex [Ru2(2,4,6-F3PhCO2)4(THF)2] (2,4,6-F3PhCO2(-) = 2,4,6-trifluorobenzoate; abbreviated hereafter as [Ru2]) with 7,7,8,8-tetracyano-p-quinodimethane (TCNQ) in a p-xylene/CH2Cl2 solvent system led to the formation of a two-dimensional layered compound, [{Ru2(2,4,6-F3PhCO2)4}2(TCNQ)]·2(p-xylene)·2CH2Cl2 (1). As expected from this D/A combination, 1 has a one-electron-transfer ionic state with the D(0.5+)2A(-) formulation. This state formally derives a heterospin state composed of S = 1 for [Ru(II,II)2], S = 3/2 for [Ru(II,III)2](+), and S = ½ for TCNQ(•-), possibly causing intralayer ferrimagnetic spin ordering. Most of these types of compounds have an antiferromagnetic ground state because of the coupling of ferrimagnetically ordered layers in dipole antiferromagnetic interactions. However, 1 became a three-dimensional ferrimagnet with T(C) = 91 K because of the presence of interlayer ferromagnetic interactions.

The insertion of “sandwiched spins” between magnetic layers could efficiently affect the interlayer magnetic correlations, but doing so increases the complexity in the interlayer spin alignment because of competition between the inserted spin‐layer interaction JNNI and the interlayer through‐space interaction JNNNI if the magnitude of JNNI is of the same order as JNNNI with reciprocal signs of the respective interactions. Herein, systematic tuning of the magnetic phase variations by JNNI and JNNNI in two kinds of metal‐variable isostructural series of supramolecular pillared layer magnets [MCp*2][{Ru2II,II(2,3,5,6‐F4CO2)4}2(TCNQ)]⋅2 DCE (M=Co, Fe, Cr; 2,3,5,6‐F4PhCO2−=2,3,5,6‐tetrafluorobenzoate; TCNQ=7,7,8,8‐tetracyano‐p‐quinodimethane; DCE=1,2‐dichloroethane) and their DCE‐free series, in which [MCp*2]+ (Cp*=η5‐C5Me5) species with S=0, 1/2, and 3/2 for M=Co, Fe, Cr, respectively, are sandwiched between ferrimagnetic layers of [{Ru2}2(TCNQ)]−, is demonstrated. The results showed that the flexible magnetic natures of these magnets are changeable in dependence on JNNI and JNNNI, as well as on interlayer inserted spins M.

The control of inter-lattice magnetic interactions is a crucial issue when long-range ordered magnets that are based on low-dimensional magnetic frameworks are designed. A "pillared layer framework (PLF)" model could be an efficient system for this purpose. In this report, A magnet based on a π-stacked PLF with a phase transition temperature of 82 K, which can be increased to 107 K by applying a pressure of 12.5 kbar, is rationally constructed. Two types of low-dimensional magnetic framework systems, an electron donor/acceptor magnetic layer and a charge transfer [FeCp*2](+)TCNQ(.-) columnar magnet ([FeCp*2](+) = decamethylferrocenium; TCNQ = 7,7,8,8-tetracyano-p-quinodimethane), are integrated to fabricate the magnet. This synthetic strategy employing a combination of layers and chains is widely useful not only for magnet design, but also for the creation of multifunctional materials with pores and anisotropic frameworks.