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ABSTRACT: The introduction of cyano groups into lumazine (pteridine-2,4(1H,3H)dione) at the C6 and C7 positions enhances its electron affinity, proton acidity, and solubility in solvents. As a result, 6,7-dicyanolumazine (H2DCNLm) forms charge transfer (CT) complexes with donors such as tetrathiafulvalene, 2,3,5,6-tetramethyl-1,4-phenylenediamine, and 3,3',5,5'-tetramethylbenzidine, and readily dissociates a proton from the N1 nitrogen to form a monoanionic salt with tetrabutylammonium (TBA). Crystal structures of the CT complexes consist of mixed stacks in which H2DCNLm interacts with donors in face-to-face configurations, but they form intermolecular hydrogen bonds differently depending on the donor type. In the TBA salt, two HDCNLm monoanions form a unique dianionic dimer connected by two centrosymmetric hydrogen bonds, N3-H•••O-C2, which is electronically isolated by the presence of bulky TBA countercations and the absence of a proton at the N1 hydrogen-bonding site. This dimer fluoresces yellow (fluorescence quantum yield Φ = 0.04). Because the HDCNLm anion only shows weak blue fluorescence in aqueous solution (Φ < 0.01), we suggest that the dimer formation is responsible for the fluorescence enhancement with a large emission band shift to the low energy side.
The Journal of Physical Chemistry A 04/2013; · 2.95 Impact Factor
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ABSTRACT: Porous coordination polymer (PCP) polymorphs with the formula [Cu(CF3SO3)2(bpp)2]n [1 and 2, where bpp = 1,3-bis(4-pyridyl)propane] have been synthesized and crystallographically characterized, and their distinguishable porous properties have been investigated. 1 was obtained by the removal of guest acetone molecules from one-dimensional PCP {[Cu(CF3SO3)(bpp)2]·CF3SO3·2acetone}n (1⊃2acetone), while 2 was derived from two-dimensional PCP {[Cu(CF3SO3)2(bpp)2]·H2O}n (2⊃H2O) by the loss of guest H2O molecules. The desolvated PCPs 1 and 2 with the same formula [Cu(CF3SO3)2(bpp)2] showed distinguishable structures, suggesting PCP polymorphs. In addition, their adsorption behaviors were completely different: 1 showed adsorption with the structural transformation from closed to open forms, while 2 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.
Inorganic Chemistry 03/2013; · 4.60 Impact Factor
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ABSTRACT: Two new single molecule magnets (SMMs), [Mn(12)O(12)(CHF(2)COO)(16)(H(2)O)(4)]·2CH(2)Cl(2)·4H(2)O () and [Mn(12)O(12)(m-FPhCOO)(16)(H(2)O)(4)]·2(m-FPhCOOH)·7CH(2)Cl(2) (), based on a disc-shaped {Mn(12)O(12)}-framework with difluoromethylacetate (CHF(2)COO(-)) and m-fluorobenzoate (m-FPhCOO(-)) as polar ligands were prepared in CH(2)Cl(2). Structural analyses by X-ray diffraction at 100 K showed orientationally disordered fluorine atoms in the CHF(2)COO(-) and m-FPhCOO(-) ligands of crystals and , respectively. In crystal , the fluorine atoms at the axial coordination sites of the disc-like {Mn(12)O(12)}-framework exhibited large thermal parameters even at 100 K, suggesting that thermally activated rotation of the -CHF(2) groups along the C-COO axis occurred in the CHF(2)COO(-) ligands. The SMMs behaviors of crystals and showed magnetization hysteresis at 1.8 K and frequency-dependent in-phase and out-of-phase ac magnetic susceptibilities, characteristic of SMMs. Frequency-dependent dielectric responses as well as two Debye-type relaxation processes at ∼100 and ∼220 K were observed in crystal , while such responses were not observed in crystal . The activation energy and blocking temperature of the relaxation process for were 12 kJ mol(-1) and 48 K, respectively, at ∼100 K, whereas those at ∼220 K were 66 kJ mol(-1) and 153 K, respectively. In , the two polarization types at ∼100 and ∼220 K were associated with thermally activated fluctuations of the hydrogen-bonded crystalline H(2)O molecules and rotation of the -CHF(2) group in the CHF(2)COO(-) ligand.
Dalton Transactions 12/2012; · 3.84 Impact Factor
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ABSTRACT: 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)](-) () 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)](-)(H(2)O)(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(+)∼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 . 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 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 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 , whose magnetic behaviour followed the Bonner-Fisher model.
Dalton Transactions 12/2012; · 3.84 Impact Factor
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ABSTRACT: High selectivity and low-energy regeneration for adsorption of CO(2) gas were achieved concurrently in a two-dimensional Cu(II) porous coordination polymer, [Cu(PF(6))(2)(4,4'-bpy)(2)](n) (4,4'-bpy = 4,4'-bipyridine), containing inorganic fluorinated PF(6)(-) anions that can act as moderate interaction sites for CO(2) molecules.
Inorganic Chemistry 12/2012; · 4.60 Impact Factor
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ABSTRACT: Supramolecular assemblies of anilinium (Ani(+)) and fluoroanilinium derivatives (FAni(+)) with [18]crown-6 were introduced into electrically conducting [Ni(dmit)(2)] crystals (dmit(2-) is 2-thioxo-1,3-dithiole-4,5-dithiolate). The crystal structures, electrical conductivities, and magnetic susceptibilities of four new crystals of (Ani(+))([18]crown-6)[Ni(dmit)(2)](3) (1), (o-FAni(+))([18]crown-6)[Ni(dmit)(2)](3) (2), (m-FAni(+))([18]crown-6)[Ni(dmit)(2)](3) (3), and (p-FAni(+))([18]crown-6)[Ni(dmit)(2)](3) (4) were examined from the viewpoint of dynamic supramolecular rotator structures within the crystals. The crystal structures, electrical conduction, and magnetic properties were classified into group-I (crystals 1 and 4) and group-II (crystals 2 and 3). The hydrogen-bonding interaction between -NH(3)(+) and the oxygen atoms of [18]crown-6 formed the stand-up configuration of rotator-stator structures of (Ani(+))([18]crown-6) and (FAni(+))([18]crown-6) supramolecules. The potential energy barriers for the 2-fold flip-flop motion of phenyl- and p-fluorophenyl-rings in crystals 1 and 4 had a relatively small magnitude of ∼150 kJmol(-1), suggesting that rotations of Ani(+) and p-FAni(+) cations around the C-NH(3)(+) axis occurred in the crystals. In contrast, a large magnitude of the potential energy barriers for the rotations of o-FAni(+) and m-FAni(+) cations in crystals 2 and 3 (>600 kJmol(-1)) resulted in static supramolecular cationic structures. The cation:anion ratio of 1:3 in these crystals yielded a trimer π-stack of [Ni(dmit)(2)] with a semiconductor-like temperature dependence. The magnetic susceptibilities of the static crystals 2 and 3 were reproduced by the one-dimensional antiferromagnetic linear Heisenberg chain through the one-dimensional linear trimer arrangement. The magnetic susceptibilities of dynamic crystals 1 and 4 enhanced electron delocalization through the intratrimer and intertrimer interactions within the trimer stack, where the molecular rotations of Ani(+) and p-FAni(+) cations played an important role.
Inorganic Chemistry 11/2012; · 4.60 Impact Factor
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ABSTRACT: Sandwich-type hydrogen-bonded supramolecular dications (DAAz(2+))([18]crown-6)(2) and (DAAz(2+))(dicyclohexane[18]crown-6)(2) (DAAz(2+) = 4,4'-(phenylazophenyl)diammonium) were introduced into [Ni(dmit)(2)](-) anions via a diffusion method to form novel single crystals (DAAz(2+))([18]crown-6)(2)[Ni(dmit)(2)](2) (1) and (DAAz(2+))(dicyclohexane[18]crown-6)(2)[Ni(dmit)(2)](2) (2), respectively, which were characterized based on their crystal structures and magnetic susceptibilities. The molecular assembly structures and its physical properties were expanded in the use of a three component molecular network system. The two ammonium groups (-NH(3)(+)) of the DAAz(2+) dication formed N-H(+)-O hydrogen-bonding interactions with the oxygen atoms of [18]crown-6 and dicyclohexane[18]crown-6. In the case of crystal 1, an alternating π-stacking interaction was observed for the [Ni(dmit)(2)](-) anions, whereas orthogonal linear π-S interactions were detected for crystal 2. Temperature-dependent magnetic susceptibilities of crystals 1 and 2 followed the alternate Heisenberg antiferromagnetic chain (J = -15.8 K) and linear Heisenberg antiferromagnetic chain (J = -13.7 K) models, respectively.
Dalton Transactions 06/2012; 41(31):9297-303. · 3.84 Impact Factor
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Ryo Tsunashima,
Takumi Matsumoto,
Norihisa Hoshino,
Wataru Niiho,
Mizuki Kimura,
Kei Kondo,
Yoshihiko Suyama,
Yukihiro Nishioka,
Jun Kawamata,
Shin-ichiro Noro,
Takayoshi Nakamura, Tomoyuki Akutagawa,
Katsuya Ishiguro
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ABSTRACT: A new salt-[Ni(II)(DMSO)(5)(TTFPy)](2)[α-SiW(12)O(40)] (1)-based on polyoxometalates was prepared by coordinating a cationic electron donor of pyridyltetrathiafulvalene (TTFPy) with Ni(II). Although the TTFPy molecule did not form a salt with the anionic α-[SiW(VI)(12)O(40)](4-) because of the weak charge-transfer (CT) interaction, the coordination of Ni with the pyridyl moiety permitted salt formation driven by electrostatic interaction, giving a single crystal of 1. Crystallographic analysis, UV-vis and IR spectroscopy and electrochemical characterization revealed that the fully oxidized α-[SiW(VI)(12)O(40)](4-) was crystallized with the neutral TTFPy moiety from the acetonitrile solution because of the low electron-withdrawing ability of α-[SiW(VI)(12)O(40)](4-), forming a brown-orange crystal. The crystal colour quickly turned to black by immersing in methanol, due to CT from TTF moiety to α-[SiW(VI)(12)O(40)](4-), which was caused by the solvent effect. Increase in the solvent acceptor number from 18.9 for acetonitrile to 41.3 for methanol resulted in the enhancement of the electron withdrawing ability of α-[SiW(VI)(12)O(40)](4-) by 0.317 V in methanol.
Dalton Transactions 06/2012; 41(33):10060-4. · 3.84 Impact Factor
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ABSTRACT: The temperature-dependent dynamic properties of [Cu(II)(2)(ADCOO)(4)(DMF)(2)]⋅(DMF)(2) (1) and [Cu(II)(2)(ADCOO)(4)(AcOEt)(2)] (2) crystals were examined by X-ray crystallography, (1)H NMR spectroscopy, and measurements of the dielectric constants and magnetic susceptibilities (ADCOO = adamantane carboxylate, DMF = N,N-dimethylformamide, and AcOEt = ethyl acetate). In both crystals, four ADCOO groups bridged a binuclear Cu(II)-Cu(II) bond, forming a paddle-wheel [Cu(II)(2)(ADCOO)(4)] structure. The oxygen atoms of two DMF molecules in crystal 1 and two AcOEt molecules in crystal 2 were coordinated at axial positions of the [Cu(II)(2)(ADCOO)(4)] moiety, forming [Cu(II)(2)(ADCOO)(4)(DMF)(2)] and [Cu(II)(2)(ADCOO)(4)(AcOEt)(2)], respectively. Two additional DMF molecules were included in the unit cell of crystal 1, whereas AcOEt was not included in the unit cell of crystal 2. The structural analyses of crystal 1 at 300 K showed three-fold rotation of the adamantyl groups, whereas rotation of the adamantyl groups of crystal 2 at 300 K was not observed. Thermogravimetric measurements of crystal 1 indicated a gradual elimination of DMF upon increasing the temperature above 300 K. The dynamic behavior of the crystallized DMF yielded significant temperature-dependent dielectric responses in crystal 1, which showed a huge dielectric peak at 358 K in the heating process. In contrast, only small frequency-dependent dielectric responses were observed in crystal 2 because of the freezing of the molecular rotation of the adamantyl groups. The magnetic behavior was dominated by the strong antiferromagnetic coupling between the two S = 1/2 spins of the Cu(II)-Cu(II) site, with magnetic exchange energies (J) of -265 K (crystal 1) and -277 K (crystal 2).
Chemistry 11/2011; 17(51):14442-9. · 5.93 Impact Factor
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ABSTRACT: Structurally flexible trans-cyclohexane-1,4-diammonium (CHDA2+) forms a hydrogen-bonded sandwich-type supramolecule with benzo[18]crown-6 in (CHDA2+)(benzo[18]crown-6)2[Ni(dmit)2]2 (1) (dmit2–: 2-thioxo-1,3-dithiole-4,5-dithiolate). During the crystallization, the three crystal polymorphs 1a, 1b, and 1c were obtained in the space groups P21/c, P1̅, and P1̅, in which the orientation of the benzene rings of benzo[18]crown-6 in the sandwich-type supramolecular cations and the [Ni(dmit)2]− arrangements were different. Crystal 1c had a structural phase transition at 200 K, at which the unit cell volume of the low-temperature phase (1d) became twice that of the high-temperature phase (1c). The [Ni(dmit)2] π-dimer was observed in crystals 1a, 1b, 1c, and 1d. A double-minimum-type potential energy profile was observed for the rigid rotation of CHDA2+ around the N–N axis. Among four new crystals, the relatively low potential energy barrier of 120 kJ mol–1 for crystal 1b was consistent with the temperature- and frequency-dependent dielectric constants. The crystal polymorph and structural phase transition were coupled in (CHDA2+)(benzo[18]crown-6)2[Ni(dmit)2]−2.
08/2011;
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ABSTRACT: Hydrogen-bonded assemblies of the two-electron reduced mixed-valence Keggin clusters [PMo(12)O(40)](5-) and [SiMo(12)O(40)](6-) were obtained by the one-pot electron-transfer reactions between p-phenylenediamine (PPD) or 2,3,5,6-tetramethyl-PPD (TMPPD) (donors) and H(+)(3)[PMo(12)O(40)](3-) or H(+)(4)[SiMo(12)O(40)](4-) (acceptors) in CH(3)CN. The redox states of the [PMo(12)O(40)](5-) and [SiMo(12)O(40)](6-) clusters were confirmed by the redox titrations and electronic absorption measurements. In (HPPD(+))(3)(H(+))(2)[PMo(12)O(40)](5-)(CH(3)CN)(3-6) (1), the N-H ~ O hydrogen-bonded interactions between the monoprotonated HPPD(+) (or diprotonated H2PPD(2+)) and the [PMo(12)O(40)](5-) resulted in a windmill-like assembly and hydrophilic one-dimensional channels are formed with a cross-sectional area of 0.065 nm(2), and these are filled by the CH(3)CN molecules. Also, the CH(3)CN molecules in salt 1 were removed by immersing the single crystals of 1 into H(2)O, CH(3)OH, and C(2)H(5)OH solvents. In the compound, (HTMPPD(+))(6)[SiMo(12)O(40)](6-)(CH(3)CN)(6) (2), the N-H ~ O hydrogen-bonded interactions between the monoprotonated HTMPPD(+) molecules and the [SiMo(12)O(40)](6-) formed a "Saturn-ring"-like assembly. Each Saturn-ring was arranged into an hexagonally packed array via hydrogen-bonded and π-stacking interactions of HTMPPD(+), while the CH(3)CN solvent present in salt 2 are only found in the zero-dimensional isolated cavities.
Inorganic Chemistry 06/2011; 50(14):6711-8. · 4.60 Impact Factor
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ABSTRACT: The Dawson-type polyanion [α-Mo(18)O(54)(SO(3))(2)](4-), with two SO(3)(2-) templates embedded inside a polyoxomolybdate(vi) cage, exhibits thermochromism over an exceptionally wide temperature range (∼500 K). The temperature dependence of the cluster structure, established from X-ray crystallography, IR and Raman spectroscopy and DFT calculations, is related to a decreasing HOMO-LUMO gap in the near UV with increasing temperature. We postulate this is due to geometrical changes that affect both the occupied and unoccupied frontier molecular orbitals of this cluster anion.
Physical Chemistry Chemical Physics 03/2011; 13(16):7295-7. · 3.57 Impact Factor
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ABSTRACT: A supramolecular cation of (m-FAni(+))(DB[18]crown-6), where m-FAni(+) and DB[18]crown-6 denote m-fluoroanilinium(+) and dibenzo[18]crown-6, respectively, which is the polar unit rotating in the ferroelectric crystal of (m-FAni(+))(DB[18]crown-6)[Ni(dmit)(2)](-), was introduced into a ferromagnetic [MnCr(oxalate)(3)](-) salt as the counter cation. The crystal structure of (m-FAni(+))(DB[18]crown-6)[MnCr(oxalate)(3)](-)(CH(3)OH)(CH(3)CN) (1) is constructed from alternating layers of a two-dimensional honeycomb layer of [MnCr(oxalate)(3)](-) and (m-FAni(+))(DB[18]crown-6) supramolecular cations. The anionic layer is composed of Mn(II) and Cr(III) ions with S = 5/2 and S = 3/2 spins, respectively, bridged by the oxalate anions, which show ferromagnetic ordering at 5.5 K. The supramolecular structure is formed through the formation of hydrogen bonds between the ammonium hydrogen atoms of the m-FAni(+) cations and the oxygen atoms of the DB[18]crown-6 cavity. No orientational disorder of the fluorine atoms was observed in our X-ray structural analysis, suggesting that a two-fold flip-flop motion of the m-FAni(+) cations does not occur in the salt. The rotational freedom of the m-FAni(+) cations in the salt is restricted by the steric hindrance from neighbouring DB[18]crown-6 molecules. A design strategy for the rotation in a salt is discussed, based on the volume that the supramolecular cations occupy in the unit cell.
Dalton Transactions 02/2011; 40(7):1491-6. · 3.84 Impact Factor
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ABSTRACT: The quasi-Werner-type copper(II) complex, [Cu(PF(6))(2)(4-mepy)(4)] (1), in which 4-mepy is the 4-methylpyridine ligand, has flexible and polar axial bonds of Cu-PF(6). Flexibility of the Cu-PF(6) bonds induces diverse and unprecedented guest-inclusion structures, such as {[Cu(PF(6))(2)(4-mepy)(4)][Cu(PF(6))(4-mepy)(4)(acetone)]·PF(6)·4acetone} (γ-1⊃2.5acetone), {[Cu(PF(6))(2)(4-mepy)(4)][Cu(PF(6))(4-mepy)(4)(2-butanone)]·PF(6)·3.5(2-butanone)} (γ-1⊃2.25(2-butanone)), {[Cu(PF(6))(2)(4-mepy)(4)][Cu(PF(6))(4-mepy)(4)(H(2)O)]·PF(6)·4benzene} (γ-1⊃0.5H(2)O·2benzene), and {[Cu(PF(6))(2)(4-mepy)(4)]·2benzene} (γ-1⊃2benzene). Exposure of the dense form, α-1, to benzene vapor affords the benzene-inclusion complex {[Cu(PF(6))(2)(4-mepy)(4)]·2benzene} (γ-1⊃2benzene), all benzene guests of which are easily removed by vacuum drying, reforming guest-free, dense α-1' with smaller sized crystals than α-1. In contrast to α-1, which shows almost no CO(2) adsorption, α-1' adsorbs CO(2) gas with structural transformations, this being the first example that exhibits adsorption of gas in a dense Werner-type complex and a drastic change in adsorption properties depending on the size of the crystals.
Dalton Transactions 01/2011; 40(10):2268-74. · 3.84 Impact Factor
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Berichte der deutschen chemischen Gesellschaft 11/2010; 2011(1):116 - 120. · 2.94 Impact Factor
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ABSTRACT: Supramolecular cationic structures of (CHDA2+)(DCH[18]crown-6)2 were introduced into [Ni(dmit)2]− salts (where CHDA2+, DCH[18]crown-6, and dmit2− represent cis-cyclohexane-1,4-diammonium, meso-dicyclohexano[18]crown-6, and 2-thioxo-1,3-dithiole-4,5-dithiolate, respectively). The crystal polymorphs of (CHDA2+)(DCH[18]crown-6)2[Ni(dmit)2]2 (crystals 1 and 2) within the same crystallization batch were classified in the space groups P21/n (1) and P1̅ (2). The N−H+O hydrogen-bonding interactions between the axial- and equatorial-ammonium moieties of the CHDA2+ cation and the oxygen atoms of DCH[18]crown-6 yielded a sandwich-type 1:2 adduct of the supramolecular cation in 1 and 2. Although the overall cationic structures in 1 and 2 resembled one another, the [Ni(dmit)2]− anion arrangements were distinctively different from each other. The lateral [Ni(dmit)2]− dimer along the short axis of the anion was observed in 1, whereas two types of [Ni(dmit)2]− π-dimer existed independently in 2. The weak intermolecular interactions between the [Ni(dmit)2]− anions in 1 was reflected by the temperature dependent magnetic susceptibility, which followed the Curie−Weiss model. For 2, two different magnetic exchange energies arising from the different strengths of the π-dimer units dominated the magnetic properties.
10/2010;
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ABSTRACT: A new metal phosphonate Zn(3)(4-OOCC(6)H(4)PO(3))(2) (1) is reported which crystallizes in orthorhombic space group Pca2(1). It shows a pillared layered structure in which the {ZnO(4)}, {ZnO(5)} and {PO(3)C} polyhedra are connected through corner- or edge-sharing to form an inorganic layer in the ab plane which contains 4- and 5-member rings. These layers are pillared by the uni-oriented 4-carboxylatephenylphosphonate ligands, thus leading to a polar 3D architecture. The dielectric anisotropy measurements of a single crystal of 1 reveal that dielectric constant along the inter-layer is larger than that along the intra-layer with a ratio of about 2.3. Second harmonic generation (SHG) activity is observed.
Dalton Transactions 10/2010; 39(37):8606-8. · 3.84 Impact Factor
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ABSTRACT: Supramolecular cations of HOPD+([18]crown-6) and HMPD+([18]crown-6) were introduced into [Ni(dmit)2]- salts (HOPD+: o-aminoanilinium, HMPD+: m-aminoanilinium, and dmit2-: 2-thioxo-1,3-dithiole-4,5-dithiolate). Alternate layers of cations and anions were observed in the two new salts of (HOPD+)([18]crown-6)[Ni(dmit)2]- (1) and (HMPD+)([18]crown-6)[Ni(dmit)2]- (2). From X-ray crystal structural analyses, solid state 1H nuclear magnetic resonance (NMR) spectra, and dielectric constants, the thermal rotations of [18]crown-6 in both of the (HOPD+)([18]crown-6) and (HMPD+)([18]crown-6) supramolecules occurred at temperatures above approximately 200 K based on the orientational disorder in the crystal structures. The two-fold flip-flop motions of HOPD+ and HMPD+ cations in salts 1 and 2 were suppressed, due to the relatively large potential energy barriers. The [Ni(dmit)2]- anion formed pi-dimer arrangements in both salts, with a layer structure by lateral sulfur-sulfur interatomic contacts. Although the simple dimer model reproduced the magnetic properties of salt 1, the ladder arrangement of the pi-dimer in salt 2 yielded the magnetic behavior of a spin-ladder with a spin-gap of 92.5 K. The temperature dependent magnetic susceptibility of salt 2 was well reproduced by the magnetic anisotropy of J1/J2 approximately = 8 between the ladder-leg (J1: intra-dimer interaction) and ladder-rung (J2: inter-dimer interaction). The [18]crown-6 supramolecular rotator of (HMPD+)([18]crown-6) was coexistent with the spin-ladder chain of [Ni(dmit)2]- anions in salt 2.
Dalton Transactions 09/2010; 39(35):8219-27. · 3.84 Impact Factor
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ABSTRACT: Structurally flexible (1R,2R)-cyclohexanediammonium (CHDA(2+)) dication formed hydrogen-bonding supramolecules with [18]crown-6, benzo[18]crown-6 (B[18]crown-6), dibenzo[18]crown-6 (DB[18]crown-6), and dicyclohexano[18]crown-6 (DCH[18]crown-6) in [Ni(dmit)(2)](-) salts (dmit(2-) = 2-thioxo-1,3-dithiole-4,5-dithiolate). The two ammonium moieties of CHDA(2+) interacted with the crown ethers to form open-mouth-shaped sandwich-type cationic structures of (CHDA(2+))(crown ethers)(2), that is, (CHDA(2+))([18]crown-6)(2)[Ni(dmit)(2)](2)(-)() (1), (CHDA(2+))(B[18]crown-6)(2)[Ni(dmit)(2)](2)(-)() (2), (CHDA(2+))(DB[18]crown-6)(2)[Ni(dmit)(2)](2)(-)() (3), and (CHDA(2+))(DCH[18]crown-6)(2)[Ni(dmit)(2)](2)(-)() (4). The chiral structure of CHDA(2+) induced asymmetrical [Ni(dmit)(2)](-) arrangements in the crystals. A large frequency and temperature dependence of the dielectric response was observed in (CHDA(2+))(B[18]crown-6)(2), due to the pendulum motion of the cyclohexane ring along the nitrogen-nitrogen direction of CHDA(2+). Since the inversion center of the [Ni(dmit)(2)](-) arrangements was lost in the unit cell due to the chiral space group, the salts 1-4 showed rather complicated magnetic behaviors. The temperature-dependent magnetic properties of salts 3 and 4 were explained by the sum of the Curie-Weiss and singlet-triplet thermal excitation models, with positive (ferromagnetic) and negative (antiferromagnetic) magnetic exchange energies, respectively.
Inorganic Chemistry 09/2010; 49(18):8591-600. · 4.60 Impact Factor
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ABSTRACT: The dinuclear Cu(ii) complex bridged by a single F(-) anion has orthogonal Jahn-Teller axes, which induce a ferromagnetic interaction between the intramolecular Cu(ii) ions.
Chemical Communications 07/2010; 46(25):4619-21. · 6.17 Impact Factor
