Life and How to Live It

The reaction of Mn^III salen-type complexes with di- and tetraanionic α-Keggin-type polyoxometalates (POMs) was performed, and three types of Coulombic aggregations containing Mn^III out-of-plane dimeric units (abbreviated as [Mn₂]²⁺) that are potentially single-molecule magnets (SMMs) with an <i>S</i>_T = 4 ground state were synthesized: [Mn₂(5-MeOsaltmen)₂(acetone)₂]­[SW₁₂O₄₀] (<b>1</b>), [Mn₂(salen)₂(H₂O)₂]₂[SiW₁₂O₄₀] (<b>2</b>), and [Mn­(5-Brsaltmen)­(H₂O)­(acetone)]₂[{Mn₂(5-Brsaltmen)₂}­(SiW₁₂O₄₀)] (<b>3</b>), where 5-Rsaltmen^2– = <i>N</i>,<i>N</i>′-(1,1,2,2-tetramethylethylene)­bis­(5-R-salicylideneiminate) with R = MeO (methoxy), Br (bromo) and salen^2– = <i>N</i>,<i>N</i>′-ethylenebis­(salicylideneiminate). Compound <b>1</b> with a dianionic POM, [SW₁₂O₄₀]^2–, is composed of a 1:1 aggregating set of [Mn₂]²⁺/POM, and <b>2</b>, with a tetraanionic POM, [SiW₁₂O₄₀]^4–, is a 2:1 set. Compound <b>3</b> with [SiW₁₂O₄₀]^4– forms a unique 1D coordinating chain with a [−{Mn₂}–POM−]^2– repeating unit, for which a hydrogen-bonded dimeric unit ([Mn­(5-Brsaltmen)­(H₂O)­(acetone)]₂²⁺) is present as a countercation. Independent of the formula ratio of [Mn₂]²⁺/POM, Mn^III dimers and POM units in <b>1</b>–<b>3</b> form respective segregated columns along a direction of the unit cell, which make an alternate packing to separate evenly identical species in a crystal. The nearest intermolecular Mn···Mn distance is found in the order <b>2</b> < <b>3</b> < <b>1</b>. The segregation of the [Mn₂]²⁺ dimer resulted in interdimer distances long enough to effectively reduce the intermolecular magnetic interaction, in particular in <b>1</b> and <b>3</b>. Consequently, an intrinsic property, SMM behavior, of Mn^III dimers has been characterized in this system, even though the interdimer interactions are still crucial in the case of <b>2</b>, where a long-range magnetic order competitively affects slow relaxation of the magnetization at low ac frequencies

Magnetic Sponge Phenomena Associated with Interchain Dipole–Dipole Interactions in a Series of Ferrimagnetic Chain Compounds Doped with Minor Diamagnetic Species

The donor/acceptor ionic chain (i.e., the D⁺A^– chain) [Ru₂(2-MeO-4-ClPhCO₂)₄(BTDA-TCNQ)]·2.5­(benzene) (<b>1</b>; 2-MeO-4-ClPhCO₂^– = 2-methoxy-4-chlorobenzoate; BTDA-TCNQ = bis­(1,2,5-thiadiazolo)­tetracyanoquinodimethane) is a ferrimagnetic chain with <i>S</i> = 3/2 from [Ru₂^II,III]⁺ (i.e., D⁺) and <i>S</i> = 1/2 from BTDA-TCNQ^•– (i.e., A^–), with <i>J</i> ≈ −100 K, in which long-range antiferromagnetic ordering at <i>T</i>_N = 11 K occurs because interchain antiferromagnetic interactions are critical. Compound <b>1</b> undergoes a reversible crystal-to-crystal structural transformation with the elimination/absorption of the crystallization solvent to form the dried compound [Ru₂(2-MeO-4-ClPhCO₂)₄(BTDA-TCNQ)] (<b>1</b>′), which has a higher <i>T</i>_N (14 K). This change is clearly caused by the shortening of the interchain distances because the exchange coupling parameter for the chain is the same in both <b>1</b> and <b>1</b>′. The chain compounds in <b>1</b> can be doped with minor diamagnetic [Rh₂^II,II] species, [{(Ru₂)_1–<i>x</i>(Rh₂)_<i>x</i>(2-MeO-4-ClPhCO₂)₄}­(BTDA-TCNQ)]·2.5­(benzene) (<i>x</i> = 0.03 for <b>Rh-3%</b>; <i>x</i> = 0.05 for <b>Rh-5%</b>; <i>x</i> = 0.16 for <b>Rh-16%</b>), which shifts the <i>T</i>_N to lower temperatures, the magnitude of the shift being dependent on the doping ratio <i>x</i> (<i>T</i>_N = 5.9 K for <b>Rh-3%</b>, <i>T</i>_N = 3.7 K for <b>Rh-5%</b>, and <i>T</i>_N was not observed above 1.8 K for <b>Rh-16%</b>). Drying a doped compound increased its <i>T</i>_N, as was found for <b>1</b>′: <i>T</i>_N = 9.9 K for <b>Rh-3%</b>′, <i>T</i>_N = 9.2 K for <b>Rh-5%</b>′, and <i>T</i>_N was not observed above 1.8 K for <b>Rh-16%</b>′. <i>T</i>_N had a linear relationship with the doping ratio <i>x</i> of the [Rh₂] species in both the fresh and dried compounds. The <i>T</i>_N linear relationship is associated with the magnitude of the effective magnetic dipole (i.e., the average correlation length) in the chains caused by the [Rh₂] defects as well as naturally generated defects in the synthetic process and with the interchain distances affected by the crystal-to-crystal transformations. These results demonstrate that slightly modifying the short-range correlation lengths, which changes the magnetic dipole magnitudes, strongly affects the bulk antiferromagnetic transition, with key dipole–dipole interactions, in low-dimensional anisotropic systems

Axial-Site Modifications of Paddlewheel Diruthenium(II, II) Complexes Supported by Hydrogen Bonding

The reactions of paddlewheel-type diruthenium­(II, II) complexes, [Ru₂^II,II(<i>x</i>-FPhCO₂)₄(THF)₂] (<i>x</i>-FPhCO₂^– = <i>x</i>-fluorobenzoate with <i>x</i>- = <i>o</i>-, <i>m</i>-, <i>p</i>-), with 2,6-diaminopyridine (dapy) and 7-azaindole (azain) afford axially capped discrete compounds, [Ru₂^II,II(<i>x</i>-FPhCO₂)₄(dapy)₂] (<i>x</i> = <i>o</i>-, <b>1</b>; <i>m</i>-, <b>2</b>; <i>p</i>-, <b>3</b>) and [Ru₂^II,II(<i>o</i>-FPhCO₂)₄(azain)₂] (<b>4</b>), respectively. In these compounds, intramolecular hydrogen bonds are observed between NH₂ groups for <b>1</b>–<b>3</b> or imine NH groups for <b>4</b> and oxygen atoms of carboxylate groups. In addition, hydrogen bonds of NH₂···F are also observed for <b>1</b> and <b>4</b> with an <i>o</i>-positioned F atom on benzoate. This coordination mode, i.e., a dual bonding mode with σ-bonding and hydrogen bonding, should assist ligand coordination to the axial position of the [Ru₂] unit. The Ru–N bond distance in <b>1</b>–<b>4</b> is shorter than that observed in related compounds reported previously. In a similar fashion, reactions with planar M^II dithiobiuret (dtb) complexes, [M^II(dtb)₂] (M^II = Pd^II and Pt^II), were carried out. One-dimensional alternating chains, [{Ru₂^II,II(<i>o</i>-FPhCO₂)₄}­{M^II(dtb)₂}] (M^II = Pd^II, <b>5</b>; Pt^II, <b>6</b>), were obtained, in which the hydrogen-bonding modes of NH₂···O and NH₂···F are present, as expected. DFT calculations for the [M^II(dtb)₂] unit revealed that the LUMO of [M^II(dtb)₂] lies at −2.159 and −1.781 eV for M = Pd and Pt, respectively, which is much higher than HOMO energy at −4.184 eV calculated for [Ru₂^II,II(<i>o</i>-FPhCO₂)­(THF)₂], proving that the respective units are essentially electronically isolated in the chains

Tuning of Stepwise Neutral–Ionic Transitions by Acceptor Site Doping in Alternating Donor/Acceptor Chains

The stepwise neutral–ionic (N–I) phase transition found in the alternating donor/acceptor (DA) chain [Ru₂(2,3,5,6-F₄PhCO₂)₄(DMDCNQI)]·2­(<i>p</i>-xylene) (<b>0</b>; 2,3,5,6-F₄PhCO₂^– = 2,3,5,6-tetrafluorobenzoate; DMDCNQI = 2,5-dimethyl-<i>N</i>,<i>N</i>′-dicyanoquinonediimine) was tuned by partly substituting the acceptor DMDCNQI with 2,5-dimethoxy-<i>N</i>,<i>N</i>′-dicyanoquinonediimine (DMeODCNQI), which displays a poorer electron affinity in an isostructural series. The site-doped series comprised [Ru₂(2,3,5,6-F₄PhCO₂)₄(DMDCNQI)_1–<i>x</i>(DMeODCNQI)_<i>x</i>]·2­(<i>p</i>-xylene) for doping rates (<i>x</i>) = 0.05 (<b>0.05-MeO</b>), 0.10 (<b>0.10-MeO</b>), 0.15 (<b>0.15-MeO</b>), and 0.20 (<b>0.20-MeO</b>). The neutral chain [Ru₂(2,3,5,6-F₄PhCO₂)₄(DMeODCNQI)]·4­(<i>p</i>-xylene) (<b>1</b>), which only contained DMeODCNQI, was also characterized. All site-doped compounds were isostructural to <b>0</b> except <b>1</b> despite their identical DA chain motif. Except at an <i>x</i> value of 0.20, they displayed a two-step N–I transition involving an intermediate phase. This transition occurred at high temperatures in <b>0</b> but shifted to lower temperatures in a parallel manner with increasing doping rate. Simultaneously, each transition broadened with increasing doping rate, leading to a convergence of two transitions at an <i>x</i> value approximating 0.2. Donor/acceptor-site-doping techniques present somewhat different impacts in terms of interchain Coulomb effects

Axial-Site Modifications of Paddlewheel Diruthenium(II, II) Complexes Supported by Hydrogen Bonding

The reactions of paddlewheel-type diruthenium­(II, II) complexes, [Ru₂^II,II(<i>x</i>-FPhCO₂)₄(THF)₂] (<i>x</i>-FPhCO₂^– = <i>x</i>-fluorobenzoate with <i>x</i>- = <i>o</i>-, <i>m</i>-, <i>p</i>-), with 2,6-diaminopyridine (dapy) and 7-azaindole (azain) afford axially capped discrete compounds, [Ru₂^II,II(<i>x</i>-FPhCO₂)₄(dapy)₂] (<i>x</i> = <i>o</i>-, <b>1</b>; <i>m</i>-, <b>2</b>; <i>p</i>-, <b>3</b>) and [Ru₂^II,II(<i>o</i>-FPhCO₂)₄(azain)₂] (<b>4</b>), respectively. In these compounds, intramolecular hydrogen bonds are observed between NH₂ groups for <b>1</b>–<b>3</b> or imine NH groups for <b>4</b> and oxygen atoms of carboxylate groups. In addition, hydrogen bonds of NH₂···F are also observed for <b>1</b> and <b>4</b> with an <i>o</i>-positioned F atom on benzoate. This coordination mode, i.e., a dual bonding mode with σ-bonding and hydrogen bonding, should assist ligand coordination to the axial position of the [Ru₂] unit. The Ru–N bond distance in <b>1</b>–<b>4</b> is shorter than that observed in related compounds reported previously. In a similar fashion, reactions with planar M^II dithiobiuret (dtb) complexes, [M^II(dtb)₂] (M^II = Pd^II and Pt^II), were carried out. One-dimensional alternating chains, [{Ru₂^II,II(<i>o</i>-FPhCO₂)₄}­{M^II(dtb)₂}] (M^II = Pd^II, <b>5</b>; Pt^II, <b>6</b>), were obtained, in which the hydrogen-bonding modes of NH₂···O and NH₂···F are present, as expected. DFT calculations for the [M^II(dtb)₂] unit revealed that the LUMO of [M^II(dtb)₂] lies at −2.159 and −1.781 eV for M = Pd and Pt, respectively, which is much higher than HOMO energy at −4.184 eV calculated for [Ru₂^II,II(<i>o</i>-FPhCO₂)­(THF)₂], proving that the respective units are essentially electronically isolated in the chains

Electron-Transferred Donor/Acceptor Ferrimagnet with <i>T</i>_C = 91 K in a Layered Assembly of Paddlewheel [Ru₂] Units and TCNQ

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-<i>p</i>-quinodimethane (TCNQ) in a <i>p</i>-xylene/CH₂Cl₂ solvent system led to the formation of a two-dimensional layered compound, [{Ru₂(2,4,6-F₃PhCO₂)₄}₂(TCNQ)]·2­(<i>p</i>-xylene)·2CH₂Cl₂ (<b>1</b>). As expected from this D/A combination, <b>1</b> has a one-electron-transfer ionic state with the D^0.5+₂A^– formulation. This state formally derives a heterospin state composed of <i>S</i> = 1 for [Ru^II,II₂], <i>S</i> = ³/₂ for [Ru^II,III₂]⁺, and <i>S</i> = ¹/₂ 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, <b>1</b> became a three-dimensional ferrimagnet with <i>T</i>_C = 91 K because of the presence of interlayer ferromagnetic interactions

Axial-Site Modifications of Paddlewheel Diruthenium(II, II) Complexes Supported by Hydrogen Bonding

The reactions of paddlewheel-type diruthenium­(II, II) complexes, [Ru₂^II,II(<i>x</i>-FPhCO₂)₄(THF)₂] (<i>x</i>-FPhCO₂^– = <i>x</i>-fluorobenzoate with <i>x</i>- = <i>o</i>-, <i>m</i>-, <i>p</i>-), with 2,6-diaminopyridine (dapy) and 7-azaindole (azain) afford axially capped discrete compounds, [Ru₂^II,II(<i>x</i>-FPhCO₂)₄(dapy)₂] (<i>x</i> = <i>o</i>-, <b>1</b>; <i>m</i>-, <b>2</b>; <i>p</i>-, <b>3</b>) and [Ru₂^II,II(<i>o</i>-FPhCO₂)₄(azain)₂] (<b>4</b>), respectively. In these compounds, intramolecular hydrogen bonds are observed between NH₂ groups for <b>1</b>–<b>3</b> or imine NH groups for <b>4</b> and oxygen atoms of carboxylate groups. In addition, hydrogen bonds of NH₂···F are also observed for <b>1</b> and <b>4</b> with an <i>o</i>-positioned F atom on benzoate. This coordination mode, i.e., a dual bonding mode with σ-bonding and hydrogen bonding, should assist ligand coordination to the axial position of the [Ru₂] unit. The Ru–N bond distance in <b>1</b>–<b>4</b> is shorter than that observed in related compounds reported previously. In a similar fashion, reactions with planar M^II dithiobiuret (dtb) complexes, [M^II(dtb)₂] (M^II = Pd^II and Pt^II), were carried out. One-dimensional alternating chains, [{Ru₂^II,II(<i>o</i>-FPhCO₂)₄}­{M^II(dtb)₂}] (M^II = Pd^II, <b>5</b>; Pt^II, <b>6</b>), were obtained, in which the hydrogen-bonding modes of NH₂···O and NH₂···F are present, as expected. DFT calculations for the [M^II(dtb)₂] unit revealed that the LUMO of [M^II(dtb)₂] lies at −2.159 and −1.781 eV for M = Pd and Pt, respectively, which is much higher than HOMO energy at −4.184 eV calculated for [Ru₂^II,II(<i>o</i>-FPhCO₂)­(THF)₂], proving that the respective units are essentially electronically isolated in the chains

Axial-Site Modifications of Paddlewheel Diruthenium(II, II) Complexes Supported by Hydrogen Bonding

The reactions of paddlewheel-type diruthenium­(II, II) complexes, [Ru₂^II,II(<i>x</i>-FPhCO₂)₄(THF)₂] (<i>x</i>-FPhCO₂^– = <i>x</i>-fluorobenzoate with <i>x</i>- = <i>o</i>-, <i>m</i>-, <i>p</i>-), with 2,6-diaminopyridine (dapy) and 7-azaindole (azain) afford axially capped discrete compounds, [Ru₂^II,II(<i>x</i>-FPhCO₂)₄(dapy)₂] (<i>x</i> = <i>o</i>-, <b>1</b>; <i>m</i>-, <b>2</b>; <i>p</i>-, <b>3</b>) and [Ru₂^II,II(<i>o</i>-FPhCO₂)₄(azain)₂] (<b>4</b>), respectively. In these compounds, intramolecular hydrogen bonds are observed between NH₂ groups for <b>1</b>–<b>3</b> or imine NH groups for <b>4</b> and oxygen atoms of carboxylate groups. In addition, hydrogen bonds of NH₂···F are also observed for <b>1</b> and <b>4</b> with an <i>o</i>-positioned F atom on benzoate. This coordination mode, i.e., a dual bonding mode with σ-bonding and hydrogen bonding, should assist ligand coordination to the axial position of the [Ru₂] unit. The Ru–N bond distance in <b>1</b>–<b>4</b> is shorter than that observed in related compounds reported previously. In a similar fashion, reactions with planar M^II dithiobiuret (dtb) complexes, [M^II(dtb)₂] (M^II = Pd^II and Pt^II), were carried out. One-dimensional alternating chains, [{Ru₂^II,II(<i>o</i>-FPhCO₂)₄}­{M^II(dtb)₂}] (M^II = Pd^II, <b>5</b>; Pt^II, <b>6</b>), were obtained, in which the hydrogen-bonding modes of NH₂···O and NH₂···F are present, as expected. DFT calculations for the [M^II(dtb)₂] unit revealed that the LUMO of [M^II(dtb)₂] lies at −2.159 and −1.781 eV for M = Pd and Pt, respectively, which is much higher than HOMO energy at −4.184 eV calculated for [Ru₂^II,II(<i>o</i>-FPhCO₂)­(THF)₂], proving that the respective units are essentially electronically isolated in the chains

Axial-Site Modifications of Paddlewheel Diruthenium(II, II) Complexes Supported by Hydrogen Bonding

The reactions of paddlewheel-type diruthenium­(II, II) complexes, [Ru₂^II,II(<i>x</i>-FPhCO₂)₄(THF)₂] (<i>x</i>-FPhCO₂^– = <i>x</i>-fluorobenzoate with <i>x</i>- = <i>o</i>-, <i>m</i>-, <i>p</i>-), with 2,6-diaminopyridine (dapy) and 7-azaindole (azain) afford axially capped discrete compounds, [Ru₂^II,II(<i>x</i>-FPhCO₂)₄(dapy)₂] (<i>x</i> = <i>o</i>-, <b>1</b>; <i>m</i>-, <b>2</b>; <i>p</i>-, <b>3</b>) and [Ru₂^II,II(<i>o</i>-FPhCO₂)₄(azain)₂] (<b>4</b>), respectively. In these compounds, intramolecular hydrogen bonds are observed between NH₂ groups for <b>1</b>–<b>3</b> or imine NH groups for <b>4</b> and oxygen atoms of carboxylate groups. In addition, hydrogen bonds of NH₂···F are also observed for <b>1</b> and <b>4</b> with an <i>o</i>-positioned F atom on benzoate. This coordination mode, i.e., a dual bonding mode with σ-bonding and hydrogen bonding, should assist ligand coordination to the axial position of the [Ru₂] unit. The Ru–N bond distance in <b>1</b>–<b>4</b> is shorter than that observed in related compounds reported previously. In a similar fashion, reactions with planar M^II dithiobiuret (dtb) complexes, [M^II(dtb)₂] (M^II = Pd^II and Pt^II), were carried out. One-dimensional alternating chains, [{Ru₂^II,II(<i>o</i>-FPhCO₂)₄}­{M^II(dtb)₂}] (M^II = Pd^II, <b>5</b>; Pt^II, <b>6</b>), were obtained, in which the hydrogen-bonding modes of NH₂···O and NH₂···F are present, as expected. DFT calculations for the [M^II(dtb)₂] unit revealed that the LUMO of [M^II(dtb)₂] lies at −2.159 and −1.781 eV for M = Pd and Pt, respectively, which is much higher than HOMO energy at −4.184 eV calculated for [Ru₂^II,II(<i>o</i>-FPhCO₂)­(THF)₂], proving that the respective units are essentially electronically isolated in the chains

Tuning of Stepwise Neutral–Ionic Transitions by Acceptor Site Doping in Alternating Donor/Acceptor Chains

The stepwise neutral–ionic (N–I) phase transition found in the alternating donor/acceptor (DA) chain [Ru₂(2,3,5,6-F₄PhCO₂)₄(DMDCNQI)]·2­(<i>p</i>-xylene) (<b>0</b>; 2,3,5,6-F₄PhCO₂^– = 2,3,5,6-tetrafluorobenzoate; DMDCNQI = 2,5-dimethyl-<i>N</i>,<i>N</i>′-dicyanoquinonediimine) was tuned by partly substituting the acceptor DMDCNQI with 2,5-dimethoxy-<i>N</i>,<i>N</i>′-dicyanoquinonediimine (DMeODCNQI), which displays a poorer electron affinity in an isostructural series. The site-doped series comprised [Ru₂(2,3,5,6-F₄PhCO₂)₄(DMDCNQI)_1–<i>x</i>(DMeODCNQI)_<i>x</i>]·2­(<i>p</i>-xylene) for doping rates (<i>x</i>) = 0.05 (<b>0.05-MeO</b>), 0.10 (<b>0.10-MeO</b>), 0.15 (<b>0.15-MeO</b>), and 0.20 (<b>0.20-MeO</b>). The neutral chain [Ru₂(2,3,5,6-F₄PhCO₂)₄(DMeODCNQI)]·4­(<i>p</i>-xylene) (<b>1</b>), which only contained DMeODCNQI, was also characterized. All site-doped compounds were isostructural to <b>0</b> except <b>1</b> despite their identical DA chain motif. Except at an <i>x</i> value of 0.20, they displayed a two-step N–I transition involving an intermediate phase. This transition occurred at high temperatures in <b>0</b> but shifted to lower temperatures in a parallel manner with increasing doping rate. Simultaneously, each transition broadened with increasing doping rate, leading to a convergence of two transitions at an <i>x</i> value approximating 0.2. Donor/acceptor-site-doping techniques present somewhat different impacts in terms of interchain Coulomb effects