Air-Stable Cyclohexasulfur as Cocrystal

A new stable cyclohexasulfur (cyclo-S₆) was discovered in the crystal of 3,5-diphenyl-1,2,4-dithiazol-1-ium (dpdti); dpdti was synthesized via an oxidation reaction of thiobenzamide with iodine in benzene, under reflux. Two kinds of crystal habitsbrick-shaped (crystal-<b>A</b>) and needle-shaped (crystal-<b>B</b>)were obtained following recrystallization from acetonitrile solvent. Single-crystal structure analysis using synchrotron X-ray radiation showed that both crystal-<b>A</b> and -<b>B</b> consist of a dpdti cation and an iodine anion. Furthermore, neutral cyclo-S₆ molecules are present in crystal-<b>A</b> as cocrystals, enclosed by the dpdti cation and the iodide anion. This is akin to cyclosulfur of <i>S</i>_<i>n</i> in zeolites and sodalities, suggesting a contribution to the stabilization of cyclo-S₆ molecules. The results show that crystal engineering of cocrystals may be used as a method to control the stability and activity of sulfur, for improved utilization

Magnetic Sponge Behavior via Electronic State Modulations

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 D₂A-type layered magnet, [{Ru₂(O₂CPh-2,3,5-Cl₃)₄}₂(TCNQMe₂)]·4DCM (<b>1</b>; 2,3,5-Cl₃PhCO₂^– = 2,3,5-trichlorobenzoate; TCNQMe₂ = 2,5-dimethyl-7,7,8,8-tetracyanoquinodimethane; DCM = dichloromethane), where [Ru₂(O₂CPh-2,3,5-Cl₃)₄] ([Ru₂^II,II]) is an electron donor (D) and TCNQMe₂ is an electron acceptor (A). Compound <b>1</b> had a one-electron-transferred, charge-ordered state with a [{Ru₂^II,II}–TCNQMe₂^•––{Ru₂^II,III}⁺] (1e-I) formula. Strong intralayer antiferromagnetic couplings between [Ru₂^II,II] with <i>S</i> = 1 or [Ru₂^II,III]⁺ with <i>S</i> = 3/2 and TCNQMe₂^•– with <i>S</i> = 1/2, as well as ferromagnetic interlayer interactions, induced long-range ferrimagnetic ordering at <i>T</i>_c = 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 (<b>1-dry</b>) without loss of crystallinity. The electronic state of <b>1-dry</b> thermally fluctuated and eventually provided a charge-disproportionate disordered state, with a [{Ru₂}^0.5+–TCNQMe₂^1.5––{Ru₂^II,III}⁺] (1.5e-I) formula as the ground state. The <i>T</i>_c in <b>1-dry</b> was 34 K because of the presence of diamagnetic TCNQMe₂^2– in some parts of the framework. A large <i>T</i>_c variation with Δ<i>T</i>_c ≈ 70 K was switchable; switching was achieved by charge-state modulations accompanied by subtle structural modifications in solvation/desolvation treatments

Triply Stacked Heterogeneous Array of Porphyrins and Phthalocyanine through Stepwise Formation of a Fourfold Rotaxane and an Ionic Complex

We report the preparation and crystal structure of a triply stacked metal complex array in which a Cu–phthalocyanine is sandwiched between different Cu–porphyrins. The discrete heterogeneous assembly was prepared through formation of a fourfold rotaxane from a tetradactyl porphyrin with alkylammonium moieties and a phthalocyanine bearing four crown ethers and the subsequent formation of an ionic complex between the fourfold rotaxane and a tetraanionic porphyrin. The tetraanionic porphyrin, Cu–TPPS^4–, is selectively bound to the fourfold rotaxane through cooperative π–π and ionic interactions. The crystal structure revealed the columnar stacked array of the three planar building components in a precise order and spatial arrangement that promote intermolecular electronic communication

Variable-Rung Design for a Mixed-Valence Two-Legged Ladder System Situated in a Dimensional Crossover Region

Ladder systems situated in a crossover from one dimensionality to two dimensionalities have been an attractive research target, because the physical properties, which are associated with dimensionality, are strongly dependent on the number of constituent legs. However, control of the intraladder configuration and electronic properties based on the substitution of structural components remain challenging tasks in materials science. On the other hand, structural design using coordination chemistry offers crucial advantages for architectural and electronic variations through substitutions of metal–organic building blocks. Here, we show the rational design and electronic properties of novel metal complex-based two-legged ladder compounds with several organic rung units: 4,4′-bipyridine, trans-1,4-diaminocyclohexane, and 4,4′-azopyridine. Single-crystal X-ray studies show that these two-legged ladder compounds are composed of halogen-bridged mixed-valence one-dimensional chains (MX chains) as their constituent legs. Depending on the molecular shape of the organic rung units, unique configurations of two-legged ladder lattices with periodic distortion of the legs are achieved. In addition, the electronic absorption spectra show that intervalence charge-transfer (IVCT) band gap of the two-legged ladder system increases with increasing degree of distortion of the leg. We have demonstrated for the first time that a two-legged ladder system shows a unique relationship between IVCT energy and the distortion parameter of the leg, as distinct from a single MX chain system. These systematic investigations, not only of configurations based on the rung variation but also of electronic states in metal–organic ladder system, provide the possibility for wide and rational tunings of physical and electronic properties of metal complex-based functional materials

Neutral-Type One-Dimensional Mixed-Valence Halogen-Bridged Platinum Chain Complexes with Large Charge-Transfer Band Gaps

One-dimensional (1D) electronic systems have attracted significant attention for a long time because of their various physical properties. Among 1D electronic systems, 1D halogen-bridged mixed-valence transition-metal complexes (the so-called MX chains) have been thoroughly studied owing to designable structures and electronic states. Here, we report the syntheses, structures, and electronic properties of three kinds of novel neutral MX-chain complexes. The crystal structures consist of 1D chains of Pt–X repeating units with (1<i>R</i>,2<i>R</i>)-(−)-diaminocychlohexane and CN^– in-plane ligands. Because of the absence of a counteranion, the neutral MX chains have short interchain distances, so that strong interchain electronic interaction is expected. Resonance Raman spectra and diffuse-reflectance UV–vis spectra indicate that their electronic states are mixed-valence states (charge-density-wave state: Pt²⁺···X–Pt⁴⁺–X···Pt²⁺···X–Pt⁴⁺–X···). In addition, the relationship between the intervalence charge-transfer (IVCT) band gap and the degree of distortion of the 1D chain shows that the neutral MX chains have a larger IVCT band gap than that of cationic MX-chain complexes. These results provide new insight into the physical and electronic properties of 1D chain compounds

Porous Coordination Polymer Polymorphs with Different Flexible Pores Using a Structurally Flexible and Bent 1,3-Bis(4-pyridyl)propane Ligand

Porous coordination polymer (PCP) polymorphs with the formula [Cu­(CF₃SO₃)₂(bpp)₂]_<i>n</i> [<b>1</b> and <b>2</b>, where bpp = 1,3-bis­(4-pyridyl)­propane] have been synthesized and crystallographically characterized, and their distinguishable porous properties have been investigated. <b>1</b> was obtained by the removal of guest acetone molecules from one-dimensional PCP {[Cu­(CF₃SO₃)­(bpp)₂]·CF₃SO₃·2acetone}_<i>n</i> (<b>1</b>⊃2acetone), while <b>2</b> was derived from two-dimensional PCP {[Cu­(CF₃SO₃)₂(bpp)₂]·H₂O}_<i>n</i> (<b>2</b>⊃H₂O) by the loss of guest H₂O molecules. The desolvated PCPs <b>1</b> and <b>2</b> with the same formula [Cu­(CF₃SO₃)₂(bpp)₂] showed distinguishable structures, suggesting PCP polymorphs. In addition, their adsorption behaviors were completely different: <b>1</b> showed adsorption with the structural transformation from closed to open forms, while <b>2</b> appeared to expand its framework for only as long as was required for the passage of guest molecules. To the best of our knowledge, PCP polymorphs showing either of two different types of flexible pores are very rare

Porous Coordination Polymer Polymorphs with Different Flexible Pores Using a Structurally Flexible and Bent 1,3-Bis(4-pyridyl)propane Ligand

Porous coordination polymer (PCP) polymorphs with the formula [Cu­(CF₃SO₃)₂(bpp)₂]_<i>n</i> [<b>1</b> and <b>2</b>, where bpp = 1,3-bis­(4-pyridyl)­propane] have been synthesized and crystallographically characterized, and their distinguishable porous properties have been investigated. <b>1</b> was obtained by the removal of guest acetone molecules from one-dimensional PCP {[Cu­(CF₃SO₃)­(bpp)₂]·CF₃SO₃·2acetone}_<i>n</i> (<b>1</b>⊃2acetone), while <b>2</b> was derived from two-dimensional PCP {[Cu­(CF₃SO₃)₂(bpp)₂]·H₂O}_<i>n</i> (<b>2</b>⊃H₂O) by the loss of guest H₂O molecules. The desolvated PCPs <b>1</b> and <b>2</b> with the same formula [Cu­(CF₃SO₃)₂(bpp)₂] showed distinguishable structures, suggesting PCP polymorphs. In addition, their adsorption behaviors were completely different: <b>1</b> showed adsorption with the structural transformation from closed to open forms, while <b>2</b> appeared to expand its framework for only as long as was required for the passage of guest molecules. To the best of our knowledge, PCP polymorphs showing either of two different types of flexible pores are very rare

Porous Coordination Polymer Polymorphs with Different Flexible Pores Using a Structurally Flexible and Bent 1,3-Bis(4-pyridyl)propane Ligand

Porous coordination polymer (PCP) polymorphs with the formula [Cu­(CF₃SO₃)₂(bpp)₂]_<i>n</i> [<b>1</b> and <b>2</b>, where bpp = 1,3-bis­(4-pyridyl)­propane] have been synthesized and crystallographically characterized, and their distinguishable porous properties have been investigated. <b>1</b> was obtained by the removal of guest acetone molecules from one-dimensional PCP {[Cu­(CF₃SO₃)­(bpp)₂]·CF₃SO₃·2acetone}_<i>n</i> (<b>1</b>⊃2acetone), while <b>2</b> was derived from two-dimensional PCP {[Cu­(CF₃SO₃)₂(bpp)₂]·H₂O}_<i>n</i> (<b>2</b>⊃H₂O) by the loss of guest H₂O molecules. The desolvated PCPs <b>1</b> and <b>2</b> with the same formula [Cu­(CF₃SO₃)₂(bpp)₂] showed distinguishable structures, suggesting PCP polymorphs. In addition, their adsorption behaviors were completely different: <b>1</b> showed adsorption with the structural transformation from closed to open forms, while <b>2</b> appeared to expand its framework for only as long as was required for the passage of guest molecules. To the best of our knowledge, PCP polymorphs showing either of two different types of flexible pores are very rare

An Electrically Conductive Single-Component Donor–Acceptor–Donor Aggregate with Hydrogen-Bonding Lattice

An electrically conductive D–A–D aggregate composed of a single component was first constructed by use of a protonated bimetal dithiolate (complex <b>1H</b>_<b>2</b>). The crystal structure of complex <b>1H</b>_<b>2</b> has one-dimensional (1-D) π-stacking columns where the D and A moieties are placed in a segregated-stacking manner. In addition, these segregated-stacking 1-D columns are stabilized by hydrogen bonds. The result of a theoretical band calculation suggests that a conduction pathway forms along these 1-D columns. The transport property of complex <b>1H</b>_<b>2</b> is semiconducting (<i>E</i>_a = 0.29 eV, ρ_rt = 9.1 × 10⁴ Ω cm) at ambient pressure; however, the resistivity becomes much lower upon applying high pressure up to 8.8 GPa (<i>E</i>_a = 0.13 eV, ρ_rt = 6.2 × 10 Ω cm at 8.8 GPa). The pressure dependence of structural and optical changes indicates that the enhancement of conductivity is attributed to not only an increase of π–π overlapping but also a unique pressure-induced intramolecular charge transfer from D to A moieties in this D–A–D aggregate

An Electrically Conductive Single-Component Donor–Acceptor–Donor Aggregate with Hydrogen-Bonding Lattice

An electrically conductive D–A–D aggregate composed of a single component was first constructed by use of a protonated bimetal dithiolate (complex <b>1H</b>_<b>2</b>). The crystal structure of complex <b>1H</b>_<b>2</b> has one-dimensional (1-D) π-stacking columns where the D and A moieties are placed in a segregated-stacking manner. In addition, these segregated-stacking 1-D columns are stabilized by hydrogen bonds. The result of a theoretical band calculation suggests that a conduction pathway forms along these 1-D columns. The transport property of complex <b>1H</b>_<b>2</b> is semiconducting (<i>E</i>_a = 0.29 eV, ρ_rt = 9.1 × 10⁴ Ω cm) at ambient pressure; however, the resistivity becomes much lower upon applying high pressure up to 8.8 GPa (<i>E</i>_a = 0.13 eV, ρ_rt = 6.2 × 10 Ω cm at 8.8 GPa). The pressure dependence of structural and optical changes indicates that the enhancement of conductivity is attributed to not only an increase of π–π overlapping but also a unique pressure-induced intramolecular charge transfer from D to A moieties in this D–A–D aggregate