Kazuya Kubo

Coordination polymers based on oxalate-bridged {[(MnCrIII)-Cr-II- (oxalate)(3)](-)}(infinity) complexes of (DAT-2H(2+))(DCH[18]crown-6)(2)[Mn-II(CH3OH)Cr-III(oxalate)(3)](-)(2)(CH3OH)(3) and (DABCO-H+)(2)(DABCO-2H(2+))[Mn-II(CH3OH)(Cl-)Cr-III(oxalate)(3)](2-)(2-) (CH3OH), where DAT, DABCO, and DCH[18]crown-6 denote 2,5-diaminotoluene, 1,4-diazabicyclo[2.2.2]octane, and cis-syncis-dicyclohexano[18]crown-6, respectively, were synthesized. The crystal structure of the former complex was composed of [Mn-II(Lambda)(CH3OH)Cr-III(Lambda)(oxalate)(3)](-) units, whereas that of the latter crystal was composed of [Mn-II(Lambda)(CH3OH)(Cl-)-Cr-III (Delta)(oxalate)(3)](2-) units. The large flexible supramolecular cation in the former provided the two-dimensional structure of [Mn-II(Lambda)(CH3OH)Cr-III(Lambda)(oxalate)(3)](-), although the two-dimensional honeycomb structure of the {[Mn-II(Delta)Cr-III(Lambda)-(oxalate)(3)](-)}infinity and {[Mn-II(Lambda)Cr-III(Delta)(oxalate)(3)](-)}(infinity) networks are often observed for the oxalate complexes. The round-shaped DABCO molecule in the latter induced a one-dimensional chain structure of [Mn-II(Lambda)(CH3OH)Cr-III(Delta)(oxalate)(3)](-). The former crystal showed a magnetic field dependence of magnetization typical for a spin-canting system.

Supramolecular crystals having one-dimensional (1d) columnar structures were constructed by using supramolecules based on tst-DCH[18]crown-6 (tst-DCH = trans-syn-trans-dicyclohexano). In the crystal of (Ani(+))(tst-DCH[18]crown-6)[Ni(dmit)(2)](-) (1) and (m-FAni(+))(tst-DCH[18]crown-6)[Ni(dmit)(2)](-) (2) (Ani(+) = anilinium(+), m-FAni(+) = m-fluoroanilinium(+), dmit(2-) = 2-thioxo-1,3-dithiole-4,5-dithiolate), the tst-DCH[18]crown-6 formed supramolecular cations with Ani(+) and m-FAni(+), respectively, through N-H center dot center dot center dot O hydrogen bonds. The planar conformation of tst-DCH[18]crown-6 molecules in the crystals provided bidirectional hydrogen bonding from the upper and lower side of the molecule that were the driving forces for the construction of the 1d supramolecular architecture. The results provided a method to control arrangements of crown ether-based supramolecules in 1d columns that could be used for channels and/or molecular nanomachines such as molecular rotators.

Metalorganic network structure based on oxalate bridges {[(MnCrIII)-Cr-II(oxalate)(3)]-}(infinity) and supramolecular cations (H2PPD2+)(benzo[18]crown-6)(2)[MnCr(oxalate)(3)](CH3OH)(CH3CN)(2) (1) and (o-FAni(+))(2)(DCH[18]crown-6)(2)[Mn(CH3OH)Cr(oxalate)(3)][MnCr(oxalate)(3)](CH3OH) (2), where H2PPD(2+), o-FAni(+), and DCH[18]crown-6 denote p-phenylenediammonium(2+), o-fluoroanilinium+, and cis-syn-cis-dicyclohexano[18]crown-6, respectively, were synthesized. The crystal structure of 1 was the combination of [Mn(boolean AND)Cr(boolean AND)(oxalate)(3)]- and [Mn(boolean AND)Cr(Delta)(oxalate)(3)]-, whereas that of crystal 2 was the combination of [Mn(boolean AND)(CH3OH)Cr(Delta)(oxalate)(3)] and [Mn(boolean AND)Cr(Delta)(oxalate)(3)]. Large flexible supramolecular cations provide the three-dimensional structure of {[(MnCrIII)-Cr-II(oxalate)(3)]-}(infinity), which is different from the two-dimensional honeycomb structure often observed for {[(MnCrIII)-Cr-II(oxalate)(3)]-}(infinity) complexes. Temperature-dependent magnetic susceptibilities of the complexes 1 and 2 exhibited ferromagnetic behaviors following the CurieWeiss law (C = 11.5 cm(3) K mol(-1), theta = 13.0 K for 1; C = 4.14 cm(-3) K mol(-1), theta = 12.3 K for 2).

Four supramolecular cations (m-XAni(+))(DB[18]crown-6) (X = F, Cl, Br or I; Ani(+) = anilinium ion; DB[18]crown-6 = dibenzo[18]crown-6) were introduced into crystals of a Keggin [SMo12O402-] polyanion to form [(m-XAni(+))(DB[18]crown-6)](2)[SMo12O402-]center dot 4CH(3)CN (1, 2, 3 or 4 for X = F, Cl, Br or I) through a hydrogen-bonding interaction. Crystals 1, 2, 3 and 4, which were isomorphous to each other, crystallized in the monoclinic space group P2(1)/(n). Supramolecular cations (m-XAni(+))(DB[18]crown-6) were constructed by a N-H+center dot center dot center dot O hydrogen-bonding interaction. [SMo12O402-] polyoxoanions were infinitely extended in three dimensions through a weak C-H center dot center dot center dot O hydrogen-bonding interaction with DB[18] crown-6. Disorder of the halogen atoms at the meta-position was observed in crystals 1, 2 and 3. The rotational freedom of the (m-XAni(+)) cations was suppressed because of weak interactions with surrounding molecules.

Supramolecular cation salt of adamantane rotator with a dithiolene complex, (fluoroadamantylammonium(+))([18]-crown-6)[Ni(dmit)(2)](-) (1) was synthesized. The fluorine atom of the adamantane unit showed a large thermal factor elongated latitudinally, suggesting molecular rotation in the solid state. Crystal 1 exhibited a large dielectric response by applying an AC field along the a axis.

4-Methylanilinium derivatives were used to introduce spaces for molecular rotation in crystals. The [Ni(dmit)(2)](-) (dmit(2-) = 2-thioxo-1,3-dithiole-4,5-dithiolate) salts with supramolecular cations of dibenzo[18]crown-6 (DB[18]crown-6) and 4-methylanilinium derivatives, (4-methylanilinium(+))(DB[18]crown-6)[Ni(dmit)(2)](-) (1), (2-fluoro-4-methylanilinium(+))(DB[18]crown-6)[Ni(dmit)(2)](-) (2), and (3-fluoro-4-methylanilinium(+))(DB[18]crown-6)[Ni(dmit)(2)](-) (3) were synthesized. The potential energy curves for the molecular rotations of the cations in the crystals had double minimum shapes with maxima of 100, 210, and 230 kJ mol(-1) for crystals 1, 2, and 3, respectively. Introduction of a methyl substituent at the p-position was effective in reducing the potential energy maxima. For crystals 2 and 3, large dielectric responses originating from the flip-flop motions of the cationic molecules were observed upon applying an AC voltage. The temperature-dependent magnetic susceptibilities of complexes 1, 2, and 3 followed the Curie-Weiss law, showing weak antiferromagnetic interactions.

A single crystal of (3-fluoro-4-methoxyanilinium)(+)([18]crown-6)[(MnCrIII)-Cr-II(oxalate)(3)](-)(CH3OH)(2) had the space group C-c owing to the arrangement of the 3-fluoro-4-methoxyanilinium(+) cation with C-1 symmetry and, therefore, was pyroelectric. A ferromagnetic transition at 5.5K was observed, which originated from the two-dimensional honeycomb structure of the [(MnCrIII)-Cr-II(oxalate)(3)](-) anion.

Supramolecular cations formed by monoprotonated pyridazinium cations and cis-anti-cis-dicyclohexano-[18]-crown-6 (DCH[18]-crown-6) or dibenzo[18]-crown-6 (DB[18]-crown-6) were introduced into [Ni(dmit)(2)](-) salts (where dmit(2-) = 2-thione-1,3-dithiole-4,5-dithiolate). X-ray crystal structure analysis of (pyridazinium(+))(DCH[18]-crown-6)[Ni(dmit)(2)](-) (1) revealed a chair-type conformation of the DCH[18]-crown-6 moiety. A V-shaped conformation of the DB[18]-crown-6 moiety was observed in (pyridazinium(+))(DB[18]-crown-6)(2)[Ni(dmit)(2)](-)(H2O)(2) (2). Nitrogen atoms in the pyridazinium cations interacted with the oxygen atoms of the DCH[18]-crown-6 and DB[18]-crown-6 through N-H+similar to O hydrogen bonds, forming 1 : 1 and 1 : 2 supramolecular structures, respectively. Sufficient space for molecular motions of the pyridazinium cations, namely flip-flop and in-plane rotations, exists in salt 1. Disorder in nitrogen atoms was observed by X-ray analysis, indicating dynamic motion of the pyridazinium cation, namely flip-flop motion and in-plane motion. A potential energy calculation further supported the possibility of dynamic motion of cations in the crystal. By contrast, the flip-flop motion of the pyridazinium group in salt 2 is restricted by the two nearest-neighbouring DB[18]-crown-6 molecules. Weak antiferromagnetic intermolecular interactions between the [Ni(dmit)(2)](-) anions in the two-dimensional layers of salt 1 were observed, resulting in alternating antiferromagnetic Heisenberg chain-type magnetic susceptibility. Quasi-one-dimensional intermolecular interactions between the [Ni(dmit)(2)](-) anions were observed in salt 2, whose magnetic behaviour followed the Bonner-Fisher model.

Single crystal of supramolecuar cation salt (adamantylammonium +)2(benzo[18]crown-6)2[Pd(dmit) 2]2-(- acetone)2 were synthesized by an electrochemical crystallization. In the crystal, two supramolecular cations and two acetones and one [Pd(dmit)2]2- dianion were crystallographically asymmetric. Molecular rotation of adamantyl groups was suggested from anisotropic thermal factors in the X-ray analysis at 173 K. © 2013 Elsevier B.V.

A new mixed-anion crystal composed of BEDT-TTF radical cation salt [BEDT-TTF]2(CuBr2)0.4(CuCl2)0.6 with an α'-type donor arrangement with a formal charge of +0.5 per BEDT-TTF was prepared by using a chemical oxidation method and characterized by using X-ray diffraction, four-probe electrical resistivity measurements (semiconductor: ρrt = 2 × 102 Ω cm, Ea = 0.2 eV), and energy band calculations. The results showed that this system had a quasi-one dimensional Fermi surface. © 2011 by the authors; licensee MDPI, Basel, Switzerland.

The electrochemical oxidation of an acetone solution containing [Mn-III (5-MeOsaltmen)(H2O)](2)(PF6)(2) (5-MeOsaltmen(2-) = N,N'-(1,1,2,2-tetramethylethylen e)bis (5-methoxysalicylideneiminate)) and (NBu4)[Ni(dmit)(2)] (dmit(2-) = 2-thioxo-1,3-dithiole-4,5-dithiolate) afforded a hybrid material, [Mn(5-MeOsaltmen)(acetone)](2)[Ni(dmit)(2)](6) (1), in which [Mn-2](2+) single-molecule magnets (SMMs) with an S-T = 4 ground state and [Ni(dmit)(2)](n-) molecules in a charge-ordered state (n = 0 or 1) are assembled in a layer-by-layer structure. Compound 1 crystallizes in the triclinic space group P (1) over bar with an inversion center at the midpoint of the Mn center dot center dot center dot Mn dimer. The [Mn-2](2+) unit has a typical nonplanar Mn(III) dimeric core and is structurally consistent with previously reported [Mn2] SMMs. The six [Ni(dmit)(2)](n-) (n = 0 or 1) units have a square-planar coordination geometry, and the charge ordering among them was assigned on the basis of v(C=C) in IR reflectance spectra (1386, 1356, 1327, and 1296 cm(-1)). The [Mn-2](2+) SMM and [Ni(dmit)(2)](n-) units aggregate independently to form hybrid frames. Electronic conductivity measurements revealed that 1 behaved as a semiconductor (rho(rt) = 2.1 x 10(-1) Omega.cm(-1), E-a = 97 meV) at ambient pressure and as an insulator at 1.7 GPa (rho(1.7GPa) = 4.5 Omega.cm(-1), E-a = 76 meV). Magnetic measurements indicated that the [Mn-2](2+) units in 1 behaved as S-T = 4 SMMs at low temperatures.

A new non-integer valence salt based on bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) with a dianionic dinuclear cupper(I) complex alpha' -[BEDT-TTF](12)((Cu2Br4)-Br-1)3 was selectively synthesized by a diffusion of BEDT-TTF in tetrahydrofurane (THF) and a mixture of (CuX2)-X-II (X = Br or Cl) in methanol An alternating stacking arrangement of the BEDT-TTF layers and inorganic layers of the (Cu2Br42)-Br-1 anions is formed where the BEDT-TTF layer Involves six crystallographically Independent molecules Overlap integral calculation among BEDT-TTF donors in the salt suggests the existence of two-dimensional interactions among the donors The compound exhibits semiconducting behavior in the wide range of temperature of room temperature to 2 K (rho(r t) = 0 3 Omega cm E-a = 0 08 eV in a crystal) without structural phase transition at ambient pressure (C) 2009 Elsevier B V All rights reserved

A new hybridized molecular crystal [Mn(5-MeOsaltmen)(acetone)](2)[Ni(dmit)(2)](6) (5-MeOsaltmen(2-) = N N'-(1 1 2 2-tetramethylethylene)bis(5-methoxysalicylideneiminate) dmit(2-) =2-thioxo-1 3-dtthiole-4 5-dithiolate) based on [Mn](2)(2+) dimer as a single molecule magnet (SMM) and the dithiolene complex [Ni(dmit)(2)] as a conducting part was prepared by electrochemical crystallization of (Bu4N)[Ni(dmit)(2)] in acetone with [Mn(5-MeOsalmen)(H2O)](PF6) An segregating stacking arrangement of the SMM layers and conducting layers is formed where the magnetic and conducting layers involve one crystallographically independent [Mn](+) monomer and three [Ni(dmit)(2)] molecules The SMM units were formed by dimerization of the Mn complex Ferromagnetic exchange parameter J(F) in the dimeric core (1 85 cm(-1)) can be estimated by Mn-O distance (2298A) in the out-of-plane dimeric core For conducting part overlap integral calculation between [Ni(dmit)(2)] acceptors in the salt suggests the existence of quasi one-dimensional interactions among the acceptors The compound exhibits semiconducting behavior from room temperature to 50K (rho(rt) = 0 3 Omega cm E-a = 0 08 eV in a crystal) without structural phase transition at ambient pressure Then this is a new type of conducting SMM (C) 2009 Elsevier B V All rights reserved

New molecular architecture for highly conducting molecular materials was developed with use of unsymmetrical organometallic-dithiolene complexes. The new architecture has various advantages including easy modification of their molecular and electronic features. Organometallic complexes based on unsymmetrical Au(III)-dithiolene complexes [(ppy)Au(C8H4S8 or C8 H4S6O2)] were prepared for new cationic components of molecular conductors. These unsymmetrical organometallic complexes can provide various cation radical salts [(ppy)Au(S-S)]2[anion][solvent]n(S-S = C8H4S8 or C8H4 S6O2, anion = PF6-, BF4-, AsF6-, TaF6-, solvent = PhCl, n = 0-0.5) by constant current electrolysis of their benzonitrile or chlorobenzene solutions containing (Bu4N)(anion) as electrolyte. [(ppy)Au(C8 H4S8)]2 [PF6] under pressure is the first molecular metal based on the organometallic component. In this review, principle of the molecular architecture based on the unsymmetrical organometallic-dithiolene complexes and physical properties of their cation radical salts are discussed. © 2009 Springer-Verlag Berlin Heidelberg.

Crystals of [Au(ppy)(S-S)](2)[Q][Solvent](n) [ppy(-) = C-deprotonated-2-phenylpyridine(-); S-S = C8H4S82-: 2-{(4,5-ethylenedithio)-1,3-dithiole-2-ylidene}-1,3-dihtiole-4,5-dithiolate(2-), C8H4S6O22- : 2-{(4,5-ethylenedioxy)-1,3-dithiole-2-ylidene}-1,3-dihtiole-4,5-dithiolate (2-); Q = PF6-, BF4-, AsF6- and TaF6-; solvent = PhCl and PhCN; n = 0-0.5] type cation radical salts were prepared by constant current electrolysis of benzonitrile or chlorobenzene solutions of unsymmetrical [Au(ppy)(S-S)] type metal complexes with [(Bu4N)-N-n][Q] as electrolyte. These salts exhibit two types of unique columnar structures. The one (S-S = C8H4S82-, Q = PF6-/S-S = C8H4S6O22-, Q = BF4-) contains the two-fold head-to-head stacking of cation radicals while the other (S-S = C8H4S82-, Q = AsF6-, TaF6-) is based on the stacking of tetramers of cation radicals. [Au(ppy)(C8H4S8)](2)[PF6] shows semiconductive behavior (E-a = 0.03 eV) under ambient pressure. Interestingly, it shows metallic behavior under high pressure (>0.8 GPa). To our knowledge, this is the first example of the metallic cation radical salt based on the unsymmetrical metal complex. Other radical cation salts show insulating or semiconducting behavior (E-a = 0.11-0.15 eV).

Crystals of [Au(ppy)(C8H4S8)](2)[PF6] [ppy(-) = C-deprotonated 2-phenylpyridine(-); C8H4S82- = 2-{(4,5-ethylenedithio)-1,3-dithiol-2-ylidene}-1,3-dithiole-4,5-dithiolate(2-)] were prepared by current-controlled electrolysis of a benzonitrile solution of [Au(ppy)(C8H4S8)] with [NEt4][PF6] as an electrolyte. The X-ray crystal structure analysis revealed the formation of a columnar stacking of two crystallographically independent cations in formally the 0.5-electron-oxidized state. Cation moieties with some S-S non-bonded contacts (< 3.7 Angstrom) along the a and b axes form a two-dimensional sheet, with the molecular interaction parallel to the ab plane. The electrical conductivities measured for a crystal at room temperature were 9.2 and 0.0028 S cm(-1) along the a and c axes, respectively. From the activation energy for the electron conduction determined by the conductivities measured for a compacted pellet the complex was estimated to be metallic from room temperature to 110 K. The energy-band calculation for the oxidized species showed two-dimensional electron conduction through the column.

[NEt4]0.9[Co(C8H4S8) 2] and [NEt4]x[Co(C6S8R2) 2] [C8H4S82-=2-{(4,5- ethylenedithio)-1,3-dithiole-2-ylidene}-1,3-dithiole-4,5-dithionate(2-) and C6S8R22-=2-{bis(alkylthio)-1,3- dithiole-2-ylidene}-1,3-dithiole-4,5-dithiolate(2-); R=C4H9, C6H13, C8H17, or C10H21; x=0.8-0.9] were prepared. They exhibited first oxidation potentials due to the dithiolate ligand-centered oxidation at -0.44∼-0.40 V (vs. Ag/Ag+) in tetrahydrofuran. They were reacted with iodine or 7,7,8,8-tetracyano-p-quinodimethane (TCNQ) to afford the oxidized species [Co(C8H4S8)2]0.3- and [Co(C6S8R2)2]n+ (0<n<1) salts. ESR spectra of the oxidized species are discussed based on molecular interactions in solution and in the solid state. Solids of them showed electrical conductivities of 10-2-10-6 S cm-1 measured for compacted pellets at room temperature. © 2002 Elsevier Science B.V. All rights reserved.

[Au(ppy)(C8H4S8)] [ppy(-) = C-deprotonated-2-phenylpyridine(1-), C8H4S82- = 2-{(4,5-ethylenedithio)-1,3-dithiole-2-ylidene}- 1,3-dithiole-4,5-ditholate(2-)] and [Au(ppy)(C-10-C6S8)] [C-10-C6S82- = 2-{bis(decylthio)-1,3-dithiole-2-ylidene}-1,3-dithiole-4,5-dithiolate(2-)] were prepared. They showed an intense electronic absorption band due to an intramolecular mixed metal/ligand-to-ligand charge transfer transition which is sensitive to a solvent. They exhibit first oxidation potentials of -0.06 to +0.20 V (vs. Ag/Ag+) due to the dithiolate ligand-centered oxidation. They were oxidized by iodine or TCNQ (7,7,8,8-tetracyano-p-quinodimethane) to afford [Au(ppy)(C8H4S8)](I-3) and [Au(ppy)(C-10-C6S8)](I-3) containing the I-3(-) ion, [Au(ppy)(C8H4S8)](TCNQ)(0.6) and [Au(ppy)(C-10-C6S8)](TCNQ)(0.5) containing the TCNQ(.-) radical anion. Their oxidized complexes behave as electrical conductors with electrical conductivities of 2.0 x 10(-2) - 4.0 x 10(-2) S cm(-1) measured for compacted pellets at room temperature. The X-ray crystal structure of [Au(ppy)(C8H4S8)].0.5DMF revealed a two-dimensional array of the molecules with some sulfur-sulfur non-bonded contacts. (C) 2003 Elsevier Science B.V. All rights reserved.

[Pt(bpy)(C8H4S8)][BF4] (bpy=2,2′-bipyridine C8H4S8 2-=2-{ (4,5-ethylenedithio)-1,3-dithiole-2-ylidene}-1,3-dithiole-4,5-dithionate(2-)) was prepared by current-controlled electrolysis of a dichloromethane solution of [Pt(bpy)(C8H4S8)] with [NEt4][BF4] as an electrolyte. The X-ray crystal structure analysis revealed a columnar stacking of the one-electron oxidized, cationic moieties with some S-S non-bonded contacts (&lt 3.7 Å) as well as an S-S layered interaction in another direction. The electrical conductivity measured for a compacted pellet was 5.0×10-3 S cm-1 at room temperature with activation energy of 0.05 eV. The energy band calculation of the oxidized species showed an essentially one-dimensional electron-conduction through the column. © 2002 Elsevier Science B.V. All rights reserved.

Pt(L)(C8H4S8) [L = 2,2′-bipyridine (bpy) and N-butyl-pyridine-2-carbaldimine (Bu-pya) C8H4S8/2- = 2-{4,5-ethylenedithio)-1,3-dithiol-2-ylidene}-1,3-dithiol-4,5-dithionate(2 -)], Pt(bpy)(C10-C6S8) [C10-C6S8/2- = 2-{bis(dodecylthio)-1,3-dithiol-2-ylidene}-1,3-dithiol-4,5-dithiolate (2-)], Pd(Bu-pya)(C8H4S8), and Pd(Bu-pya)(C3S5) [C3S5/2- = 4,5-disulfanyl-1,3-dithiol-2-thionate(2-)] were prepared. They showed intense electronic absorption bands due to an intramolecular mixed metal/ligand-to-ligand charge transfer transition which is sensitive to a solvent. They exhibit oxidation potentials of -0.18 and +0.35 V (versus Ag/Ag+) with oxidation of the dithiolate ligand. They were oxidized by iodine or TCNQ (7,7,8,8-tetracyano-p-quinodimethane) to afford [Pt(L)(C8H4S8)](I3)x (x = 0.9-1.0), [Pt(L)(C8H4S8)](TCNQ)y (y = 0.6-0.8) (L = bpy, Bu-pya and C10-C6S8) and [Pd(Bu-pya)(C8H4S8)]·I5.1 and [Pd(Bu-pya)(C8H4S8)](TCNQ)0.4. The [Pt(L)(C8H4S8)]-oxidized complexes behave as electrical conductors with conductivities of 1.4 × 10-5-6.5 × 10-3 S cm-1 measured for compacted pellets at room temperature, while the [Pd(Bu-pya)(C8H4S8)]-oxidized species exhibit conductivities of (1.4-3.2) × 10-3 S cm-1. The X-ray crystal structure of Pd(Bu-pya)(C3S5) revealed a one-dimensional array of the molecules constructed with some sulfur-sulfur non-bonded contacts. © 2000 Elsevier Science B.V.