Electrochemical exfoliation of graphite using aqueous ammonium hydrogen carbonate solution and the ability of the exfoliated product as a hydrogen production electrocatalyst support.

Electrochemical exfoliation of graphite has attracted much attention as a practical mass production of two-dimensional graphene-like materials. There is an increasing desire to find new and improved methods to create unique exfoliated products with excellent functionality. We used aqueous ammonium hydrogen carbonate solution as a new electrolyte for anodic oxidative exfoliation of graphite.

Jahn-Teller Switching of a Redox-Active Nickel(III) Center in a Homoleptic Thiolato Metalloligand Environment.

Treatment of nickel(II) nitrate with the iridium(III) metalloligand -[Ir(apt)] (apt = 3-aminopropanethiolate) gave the trinuclear complex [Ni{Ir(apt)}](NO) ([](NO)), in which the nickel center has a formal oxidation state of +III. Chemical or electrochemical oxidation and reduction of [](NO) generated the corresponding trinuclear complexes [Ni{Ir(apt)}](NO) ([](NO)) and [Ni{Ir(apt)}](NO) ([](NO)) with one-electron oxidated and reduced states, respectively. Single-crystal X-ray crystallography revealed that the nickel center in [](NO) is situated in a highly distorted octahedron due to Jahn-Teller effect, while the nickel center in each of [](NO) and [](NO) adopts a normal octahedral geometry.

Serendipitous formation of oxygen-bridged CuII6M (M = Mn, Co) double cubanes showing electrocatalytic water oxidation.

Hydroxido-bridged CuII6M double-cubane clusters (M = Mn, Co) supported by D-penicillaminedisulfide were unexpectedly formed by treating a D-penicillaminato CuII2PtII2 complex with MBr in water. The clusters displayed heterogeneous electrocatalytic activities for water oxidation dependent on the central M shared by two Cu cubane units.

A chromotropic PtPdCo coordination polymer with dual electrocatalytic activity for water reduction and oxidation.

Here, we present a heterometallic coordination polymer that exhibits heterogeneous electrocatalytic activities for both water reduction and water oxidation. Treatment of the PtII2PdII2 tetranuclear complex [Pd{Pt(NH)(D-pen)}] ([1]; D-Hpen = D-penicillamine) with CoX (X = Cl, Br) provided (PtII2PdII2CoII2) coordination polymers [Co(HO)(1)]X ([2]X), in which the PtII2PdII2 units of [1] are linked by [Co(μ-HO)(HO)] moieties in a 3D network structure. [2]X showed a colour change from orange to dark green upon dehydration, reflecting the geometrical conversion of the Co centres in [Co(μ-HO)(HO)] from an octahedron to a tetrahedron by the removal of aqua ligands.

A Pseudorotaxane System Containing γ-Cyclodextrin Formed via Chiral Recognition with an Au Ag Cu Molecular Cap.

Solvent-mediated crystal-to-crystal transformations of [Au Ag Cu (H O) (d-pen) (tdme) ] (d-[1(H O) ] ; pen =penicillaminate, tdme=1,1,1-tris(diphenylphosphinomethyl)ethane) to form unique supramolecular species are reported. Soaking crystals of d-[1(H O) ] in aqueous Na bdc (bdc =1,4-benzenedicarboxylate) yielded crystals containing d-[1(bdc)(H O) ] due to the replacement of a terminal aqua ligand in d-[1(H O) ] by a monodentate bdc ligand. When γ-cyclodextrin (γ-CD) was added to aqueous Na bdc, d-[1(H O) ] was transformed to d-[1(bdc@γ-CD)(H O) ] , where a γ-CD ring was threaded by a bdc molecule to construct a pseudorotaxane structure.

Self-assembly of cyclic hexamers of γ-cyclodextrin in a metallosupramolecular framework with d-penicillamine.

Cyclodextrins are widely used cyclic oligosaccharides of d-glucose whose hydrophilic exterior is covered by hydroxyl groups and whose hydrophobic interior is surrounded by lipophilic moieties. Because of this structural feature, cyclodextrin molecules commonly aggregate into dimensional structures intermolecular hydrogen bonds, and their aggregation into closed oligomeric architectures has been achieved only the attachment of functional substituent groups to the cyclodextrin rings. Here, we report the first structurally characterized self-assembly of non-substituted γ-cyclodextrin molecules into cyclic hexamers, which was realized in a chiral coordination framework composed of complex-anions with d-penicillamine rather than l- or dl-penicillamine.

Racemic Tartrate/Malate Anions Combine with Racemic Complex Cations to Form Optically Active Ionic Crystals.

Spontaneous resolution has attracted continuing attention in various research fields since Pasteur's work on the crystallization behavior of racemic tartrate. Here, a unique example of this phenomenon is reported, involving ionic crystals generated from racemic RR/SS- tartrate or R/S-malate and racemic ΔΔ/ΛΛ-[Ag Rh (2-aminoethanethiolato) ] (ΔΔ/ΛΛ-[1] ) in water. RR- and SS-tartrate selectively recognize the ΛΛ and ΔΔ isomers of [1] to produce ionic crystals of (ΛΛ-[1]) (RR-tartrate) and (ΔΔ-[1]) (SS-tartrate) , respectively, which can undergo spontaneous resolution.

Interconversion between square-planar palladium(ii) and octahedral palladium(iv) centres in a sulfur-bridged trinuclear structure.

Treatment of fac-[Rh(apt)] (apt = 3-aminopropanethiolate) with Pd gives an S-bridged trinuclear complex, [Pd{Rh(apt)}] ([1]), which is interconvertible with [Pd{Rh(apt)}] ([2]). This interconversion is accompanied by a drastic change between the Pd centre with an S octahedral geometry in [1] and the Pd centre with an S square-planar geometry in [2].

Dimensional Structures and Electrocatalytic Activities of Platinum(II)-Palladium(II)-Manganese(II) Coordination Polymers Controlled by Chloride versus Bromide.

Here we report the synthesis and structural characterization of heterotrimetallic (PtPdMn) coordination polymers that show different dimensionalities and electrocatalytic activities depending on chloride and bromide employed in the system. The reaction of the PtPd tetranuclear complex [PdPt(NH)(d-pen)] (), bearing free carboxylate groups, with Mn in the presence of chloride produced the (PtPdMn) coordination polymer [MnCl(HO)()]Cl (), in which the PtPd units of are linked by [MnCl(HO)] moieties in a 1:2 ratio to form a 2D sheetlike structure. The corresponding reaction in the presence of bromide also gave the (PtPdMn) coordination polymer [Mn(HO)()]Br (), but adopted a 3D network structure via a 1:1 linkage of the PtPd units with [Mn(HO)] moieties.

Charge-Separation-Type Ionic Crystals with Mixed AuCo and AuNiCo Hexanuclear Complexes.

Treatment of a digold(I) metalloligand, [Au(dppe)(d-Hpen)] (HL; d-Hpen = d-penicillamine, dppe = 1,2-bis(diphenylphosphino)ethane), with a 1:1 mixture of Co(OAc) and Ni(OAc) under aerobic conditions resulted in the formation of three types of hexanuclear complexes: [Co(L)], [NiCo(L)], and [Ni(L)]. The addition of NaNO, MNO (M = K, Rb, Cs), and M(NO) (M = Ca, Sr, Ba) to the reaction mixture led to co-crystallization of [Co(L)] and [NiCo(L)] as a solid solution to form the charge-separation (CS)-type ionic crystals , , and , respectively, while [Ni(L)] independently crystallized as a single species (). In , [Co(L)] and [NiCo(L)] cations assemble in a 1:2 ratio to form a cationic supramolecular octahedron accommodating 4 HO ions, while 10 nitrate ions are packed in each hydrophilic tetrahedral interstice of the crystal to form an anionic adamantane cluster.

Heterochiral-to-Homochiral Structural Transformation in Metallosupramolecular Ionic Crystals.

Here, we report a unique transformation from heterochiral to homochiral structures in ionic crystals composed of complex cations and complex anions. Treatment of an anionic AuCo complex, ΛΛ-[AuCo(d-pen)] ([]; Hpen = penicillamine), with M = Mn, Co, Ni, Zn in water in the presence of 1,10-phenanthroline (phen) commonly gave ionic crystals formulated as [M(phen)(HO)][Na(HO)][{M(phen)(HO)}()] (), in which [M(phen)(HO)] and [M(phen)(HO)] adopt Δ and Λ configurations, respectively. While , , and were all stable in each mother liquor, was converted to [Mn(phen)][]·phen () containing the Λ configurational [Mn(phen)] under the same conditions.

Influence of catalyst nuclearity on copper-catalyzed aerobic alcohol oxidation.

Reactions of CuX with the bis(triazolyl) ligand Hbtm [bis(1-benzyl-1H-1,2,3-triazol-4-yl)phenylmethanol] in CH2Cl2 afforded trinuclear copper(ii) complexes with a core structure (μ-X)Cu3(μ-κ3-N,O,N-btm)3(L)2+ [X = Cl, L = CH3OH (1); X = Br, L = H2O (2)], while a similar reaction of [Cu(CH3CN)4](PF6) with the mono(triazolyl) ligand HPhtm [(1-benzyl-1H-1,2,3-triazol-4-yl)diphenylmethanol] resulted in the mononuclear complex [Cu(κ2-N,O-Phtm)(κ2-N,O-HPhtm)(κ1-N-HPhtm)][PF6] (3). The structural characterization of these complexes was made by single-crystal X-ray crystallography in combination with elemental and ESI mass analyses. Catalytic studies toward aerobic oxidation of benzyl alcohol to benzaldehyde revealed that the trinuclear 1 and 2 exhibited higher activities than the mononuclear 3 in both CH3CN and EtOH/H2O solvent systems.

Controlled Formation of Thiol-Thiolate Hydrogen versus Disulfide Bonds between Two Iridium(III) Centers.

Here, we report an iridium(III) coordination system with 2-aminoethanethiolate (aet), which shows the formation of S-H⋅⋅⋅S hydrogen and S-S disulfide bonds in a controlled manner. Treatment of fac-[Ir(aet) ] with aqueous HBF under aerobic conditions gave dinuclear [Ir (aet) (cysta)] ([1] ; cysta=cystamine) with a single S-S disulfide bond, while dimeric [Ir (aet) (Haet) ](BF ) ([2](BF ) ) with a triple S-H⋅⋅⋅S hydrogen bond was formed by similar treatment under anaerobic conditions. Upon exposure to air, [2] was converted to dinuclear [Ir (aet) (Haet) (cysta)] ([3] ), in which two Ir centers are spanned by a double S-H⋅⋅⋅S hydrogen bond and a single S-S disulfide bond.

Complex Phase Behaviour and Structural Transformations of Metal-Organic Frameworks with Mixed Rigid and Flexible Bridging Ligands.

Two new heteroleptic metal-organic framework materials show strong adsorption of H and ethanol. [Co (L1)(bdc) ], where L1=N ,N -bis(4-pyridinylmethyl)-2,5-dimethylbenzene-1,4-diamine and bdc is benzene-1,4-dicarboxylate, has a twofold interpenetrating pillared layer structure with pcu topology. It has a stepped, hysteretic EtOH adsorption that can be related to complicated phase and structural transformation behaviour that occurs on de-solvation and re-solvation, including major conformational changes to the geometry of the flexible L1 ligand.

Heterogeneous catalytic water oxidation controlled by coordination geometries of copper(ii) centers with thiolato donors.

Treatment of a penicillaminato platinum(ii) metalloligand with Cu2+ gave an S-bridged PtII2CuII2 complex, which reacted with Zn2+ to produce 1D and 3D (PtII2CuII2ZnII)n coordination polymers, depending on the counter anions. These compounds increased heterogeneous electrocatalytic activities for water oxidation in proportion to the number of vacant coordination sites at thiolato dicopper(ii) cores.

A stable thiolato-Cu-thiolato triple linkage that bridges two cobalt(iii) centres.

Treatment of Λ-fac-[Co(d-pen-N,S)] (d-Hpen = d-penicillamine) with Cu in water gave a stable CoCu complex, ΛΛ-[CoCu(d-pen)] ([1]), having three thiolato-copper(i)-thiolato moieties that bridge two cobalt(iii) centres. Complex [1] was isolated as a coordination polymer of Na[1], which was converted to a complex salt of [Cr(HO)][1] by treatment with Cr(NO).

Creation of Optically Pure Crystals from a Meso-Type Gold(I) Metalloligand with d- and l-Amino Acids: A Coordination Trick.

A unique example of a coordination system that creates optically pure crystals from a meso compound with d- and l-amino acids is reported. The 1:1 reaction of a newly prepared meso digold(I) complex, [Au (dcpe)(d-Hpen)(l-Hpen)] ([H 1]), with Co(OAc) under aerobic conditions yielded a cationic Au Co trinuclear complex, [Au Co(dcpe)(d-pen)(l-pen)] [2] , in which [1] acts as a hexadentate-N ,O ,S metalloligand to a Co center. Similar reactions with M(OAc) (M=Ni and Zn) produced analogous but neutral Au M complexes, [Au M(dcpe)(d-pen)(l-pen)] ([3 ]).

Heterogeneous catalase-like activity of gold(i)-cobalt(iii) metallosupramolecular ionic crystals.

Unique heterogeneous catalase-like activity was observed for metallosupramolecular ionic crystals [AuCo(dppe)(d-pen)]X ([]X ; dppe = 1,2-bis(diphenylphosphino)ethane; d-pen = d-penicillaminate; X = (Cl), (ClO), (NO) or SO) consisting of AuCo complex cations, [], and inorganic anions, X or X. Treatment of the ionic crystals with an aqueous HO solution led to considerable O evolution with a high turnover frequency of 1.4 × 10 h for the heterogeneous cobalt complexes, which was dependent on their size and shape as well as the arrangement of cationic and anionic species.

A platinum(ii)-palladium(ii)-nickel(ii) heterotrimetallic coordination polymer showing a cooperative effect on catalytic hydrogen evolution.

Stepwise construction of a 1D heterotrimetallic coordination polymer containing all three group 10 metal ions via an ammineplatinum(ii) metalloligand with d-penicillamine is reported. This system showed a significant enhancement in heterogeneous catalytic activity for electrochemical hydrogen evolution by the stepwise introduction of Pd and Ni into the Pt metalloligand.

Chiral scrambling and independent crystallization of D4, L4, and D2L2 isomers of an Au(I)4Co(III)2 hexanuclear complex with mixed penicillaminate and bis(diphenylphosphino)ethane.

The 1:1 mixing of a pair of enantiomers of a cyclic Au(I)4Co(III)2 hexanuclear complex having penicillaminate (pen) and 1,2-bis(diphenylphosphino)ethane (dppe), [Au4Co2(dppe)2(d-pen)4](2+) (d4-[1](2+)) and [Au4Co2(dppe)2(l-pen)4](2+) (l4-[1](2+)), in solution produced an additional stereoisomer, [Au4Co2(dppe)2(d-pen)2(l-pen)2](2+) (d2l2-[1](2+)), because of the scrambling of [Co(d-pen)2](-) and [Co(l-pen)2](-) units between d4-[1](2+) and l4-[1](2+). Upon crystallization with NO3(-), the three stereoisomers were independently crystallized to form three different kinds of crystals, homochiral crystals of d4-[1](NO3)2, homochiral crystals of l4-[1](NO3)2, and heterochiral crystals of d2l2-[1](NO3)2, showing a unique example of the self-recognition and organization of three stereoisomers upon crystallization.

Crystal structure of (2S,4S)-5,5-dimethyl-2-(pyridin-2-yl)-1,3-thia-zolidine-4-carb-oxy-lic acid.

In the title compound, C11H14N2O2S, the thia-zolidine ring has an envelope conformation with the C atom bonded to the carb-oxy-lic acid group at the flap. Two C atoms of the thia-zolidine ring adopt S conformations. In the crystal, O-H⋯N hydrogen bonds between the amine and carb-oxy-lic acid groups construct a helical chain structure along the a-axis direction.

Counteranion-dependent mechanochromism of a photoluminescent platinum(II) complex with mixed terpyridine and thioglucose.

Mechanical grinding of the ClO4(-) salt of [Pt(H4tg-S)(terpy)](+) (H5tg = 1-thio-β-D-glucose, terpy = 2,2':6',2''-terpyridine), newly prepared from [PtCl(terpy)](+) and H4tg(-), caused its emission band at 630 nm to shift to 667 nm, while such mechanochromism was not observed for the PF6(-) salt that shows an emission band at 670 nm.

pH-controlled multiple chiral inversion that induces molecular dimerization in a gold(I)-cobalt(III) coordination system with L-cysteinate.

Herein, a unique coordination system that exhibits multiple chiral inversions and molecular dimerization in response to a subtle pH change is reported. Treatment of (Δ)2-H3[Au3Co2(L-cys)6] (H3[1 a]) with [Co3(aet)6](NO3)3 (aet=2-aminoethanethiolate) in water at pH 7 gave a 1:1 complex salt of [Co3(aet)6](3+) and [1 a](3-), retaining the Au(I)3Co(III)2 structure and chiral configurations of [1 a](3-). Similar treatment at pH 9 led to not only the inversion of all of the chiral Co(III) and S centers but also the dimerization of [1 a](3-), giving a 2:1 complex salt of [Co3(aet)6](3+) and (Λ)4(R)12-[Au6Co4(L-cys)12](6-) ([2](6-)).