Metallosupramolecular Structures Derived from a Series of Diphosphine-bridged Digold(I) Metalloligands with Terminald-Penicillamine

Serendipitous formation of oxygen-bridged CuII6M (M = MnII, CoII) double cubanes showing electrocatalytic water oxidation

Hydroxido-bridged CuII6M double-cubane clusters (M = Mn^II, Co^II) supported by D-penicillaminedisulfide were unexpectedly formed by treating a D-penicillaminato CuII2PtII2 complex with MBr₂ in water. The clusters displayed heterogeneous electrocatalytic activities for water oxidation dependent on the central M shared by two Cu^II cubane units.

Digold(I) Thianthrenyl Complexes. Effect of Diphosphine Ligands on Molecular Structures in the Solid State and in Solution

A series of digold complexes possessing two thianthrenyl ligands, Au₂(Thi)₂(Ph₂P(CH₂) _n PPh₂) (Thi: 1-thianthrenyl; 1: n = 1, 2: n = 2, 3: n = 3, 4: n = 4), were prepared and characterized by crystallographic and spectroscopic measurements. X-ray crystallography of complexes 1 and 3 revealed U-shaped structures with short Au-Au distances [3.2171(3) Å and 3.0735(2) Å]. Complex 2 and three of the four structure-determined molecules of complex 4 showed structures without Au-Au contacts. UV-vis spectroscopic measurements of 1-4 and TD-DFT calculations of the two conformers of 1 revealed that complexes 1 and 3 in the solution phase contained conformers with Au(I)-Au(I) interactions in a much higher proportion than complexes 2 and 4. As a result, complexes with diphosphine ligands containing an odd number of methylene groups preferred structures with Au-Au interactions in the solid state and in solution. Oxidation of 1 with 2 equiv of PhICl₂ yielded a mixture of monomeric and dimeric thianthrenes and its dimer via ligand elimination and C-C coupling, respectively.

A mesoporous ionic solid with 272 AuI 6AgI 3CuII 3 complex cations in a super huge crystal lattice

Here, we report a unique mesoporous ionic solid (I) generated from a cationic Au^I₆Ag^I₃Cu^II₃ dodecanuclear complex with d-penicillamine depending on the homochirality and crystallization conditions. I crystallizes in the cubic space group of F4₁32 with an extremely large cell volume of 2 171 340 ų, containing 272 Au^I₆Ag^I₃Cu^II₃ complex cations in the unit cell. In I, the complex cations are connected to each other through CH⋯π interactions in a zeotype framework, the topology of which is the same as that of the metal–organic framework in MIL-101, with similar but much larger two types of polyhedral pores with internal diameters of 38.2 Å and 49.7 Å, which are occupied by counter-anions and water molecules. Due to the cationic nature of the framework, I undergoes quick, specific exchanges of counter-anions while retaining its single crystallinity. This study realized the creation of a non-covalent mesoporous framework from a single complex salt, providing a conceptual advance in solid chemistry and material science.

A non-MOF ionic solid having two types of polyhedral mesopores in a very large crystal lattice is generated from a cationic Au^I₆Ag^I₃Cu^II₃ complex with d-penicillamine, showing specific exchanges of counter-anions retaining its single crystallinity.

Intermediate snapshots of a 116-nuclear metallosupramolecular cage-of-cage in a homogeneous single-crystal-to-single-crystal transformation

Soaking crystals of an AuI72CdII40NaI4 cage-of-cage in aqueous Co(NO3)2 afforded an analogous AuI72CoII44 cage-of-cage, accompanied by the exchange of NaI and CdII by CoII with retention of the single crystallinity. The homogeneous progress of the transformation led to the direct observation of intermediate species by single-crystal X-ray crystallography.

Transformations of empty CuI4 core to CuI2CuII2O and CuI6S cores via oxide and sulfide insertions

A tetrahedral {CuI4}⁴⁺ core is reversibly transformed to a mixed-valent {CuI2CuII2O}⁴⁺ core via the oxidative insertion and the reductive elimination of an oxide ion.

Heterometallic coordination polymers as heterogeneous electrocatalysts

Heterometallic coordination polymers have been rapidly developed as heterogeneous electrocatalysts. This review highlights the synthesis strategies of these polymers and the relationships between structures and electrocatalytic performances.

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 (Pt^II₂Pd^II₂Mn^II₂)_n coordination polymers that show different dimensionalities and electrocatalytic activities depending on chloride and bromide employed in the system. The reaction of the Pt^II₂Pd^II₂ tetranuclear complex [Pd₂Pt₂(NH₃)₄(d-pen)₄] (1), bearing free carboxylate groups, with Mn²⁺ in the presence of chloride produced the (Pt^II₂Pd^II₂Mn^II₂)_n coordination polymer [Mn₂Cl₂(H₂O)₆(1)]Cl₂ (2^Cl), in which the Pt^II₂Pd^II₂ units of 1 are linked by [MnCl(H₂O)₃]⁺ moieties in a 1:2 ratio to form a 2D sheetlike structure. The corresponding reaction in the presence of bromide also gave the (Pt^II₂Pd^II₂Mn^II₂)_n coordination polymer [Mn₂(H₂O)₆(1)]Br₄ (3^Br), but 3^Br adopted a 3D network structure via a 1:1 linkage of the Pt^II₂Pd^II₂ units with [Mn₂(H₂O)₆]⁴⁺ moieties. These complexes showed appreciably different electrocatalytic activities for H₂ evolution.

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 via intermolecular hydrogen bonds, and their aggregation into closed oligomeric architectures has been achieved only via 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. The self-assembly is accompanied by the 3D-to-2D structural transformation of porous coordination frameworks to form helical hexagonal cavities that accommodate helical γ-cyclodextrin hexamers. This finding provides new insight into the development of cyclodextrin chemistry and host-guest chemistry based on chiral recognition and crystal engineering processes.

Charge-Separation-Type Ionic Crystals with Mixed AuI4CoIII2 and AuI4NiIICoIII Hexanuclear Complexes

Treatment of a digold(I) metalloligand, [Au^I₂(dppe)(d-Hpen)₂] (H₂L^Au; d-H₂pen = d-penicillamine, dppe = 1,2-bis(diphenylphosphino)ethane), with a 1:1 mixture of Co(OAc)₂ and Ni(OAc)₂ under aerobic conditions resulted in the formation of three types of hexanuclear complexes: [Co^III₂(L^Au)₂]²⁺, [Ni^IICo^III(L^Au)₂]⁺, and [Ni^II₂(L^Au)₂]. The addition of NaNO₃, M¹NO₃ (M¹ = K, Rb, Cs), and M²(NO₃)₂ (M² = Ca, Sr, Ba) to the reaction mixture led to co-crystallization of [Co^III₂(L^Au)₂]²⁺ and [Ni^IICo^III(L^Au)₂]⁺ as a solid solution to form the charge-separation (CS)-type ionic crystals 1_Na, 1_M1, and 1_M2, respectively, while [Ni^II₂(L^Au)₂] independently crystallized as a single species (2). In 1_Na, [Co^III₂(L^Au)₂]²⁺ and [Ni^IICo^III(L^Au)₂]⁺ cations assemble in a 1:2 ratio to form a cationic supramolecular octahedron accommodating 4 H₃O⁺ ions, while 10 nitrate ions are packed in each hydrophilic tetrahedral interstice of the crystal to form an anionic adamantane cluster. The overall structures of 1_M1 and 1_M2 are very similar to that of 1_Na, having a CS-type structure composed of cationic supramolecular octahedra with a +12 charge and anionic inorganic clusters with a -10 charge. However, 1_M1 contains M¹ ions in place of the H₃O⁺ ions in 1_Na, and furthermore, a novel rhombic dodecahedron cluster composed of 14 nitrate ions, which encapsulates two M² ions, is formed in each hydrophilic tetrahedral interstice in 1_M2.

A 116-Nuclear Metallosupramolecular Cage-of-Cage Showing Multistep Single-Crystal-to-Single-Crystal Transformation

Here a unique single-crystal-to-single-crystal (SCSC) transformation of a 116-nuclear Au^I ₇₂ Cd^II ₄₀ Na^I ₄ cage-of-cage (2_CdNa ) is reported, which was created from a trigold(I) metalloligand with d-penicillamine by way of a 9-nuclear Au^I ₆ Cd^II ₃ cage (1). Cage-of-cage 2_CdNa is composed of 12 cages of 1 that are linked by 4 Cd²⁺ and 4 Na⁺ ions, with its surface being covered by 12 NO₃ ^- ions to form a discrete, spherical molecule with a diameter ca. 4.7 nm. In crystal 2_CdNa , the cage-of-cage molecules are packed in a cubic lattice with a huge cell volume of ca. 4.5×10⁵  ų _, so as to have large interstices with diameters of more than 3 nm. Upon soaking crystals 2_CdNa in aqueous Cu(NO₃ )₂ , all Cd²⁺ and Na⁺ were quickly exchanged by Cu²⁺ to produce an analogous Au^I ₇₂ Cu^II ₄₄ cage-of-cage (2_Cu ) in a SCSC manner. Prolonged soaking led to the SCSC transformation to another supramolecular structure (2'_Cu ) consisting of 152-nuclear Au^I ₇₂ Cu^II ₈₀ cage-of-cages that are alternately H-bonded with the Au^I ₇₂ Cu^II ₄₄ cage-of-cages. 2'_Cu showed the accommodation of MoO₄ ^2- and the conversion of MoO₄ ^2- to β-Mo₈ O₂₆ ^4- in the crystal, with retention of single-crystallinity.

Homoleptic versus heteroleptic trinuclear systems with mixed l-cysteinate and d-penicillaminate regulated by a diphosphine linker

The generation of homoleptic versus heteroleptic coordination compounds was controlled by slight modification of the diphosphine linker in a digold(i) metalloligand.

Conversion of 12-membered d3- and l3-CoIII3CdII3 metallorings into a 24-membered d3l3-CoIII6CdII6 metalloring

A unique example of a heterometallic coordination system, in which metalloring sizes are controlled via homochirality vs. heterochirality, is reported.

Ring-to-Cage Structural Conversion via Template Effect in a Gold(I) Metallosupramolecular System

A unique example of a ring-to-cage structural conversion in a multinuclear gold(I) coordination system with d-penicillamine (d-H2 pen) is reported. The reaction of [Au2 Cl2 (dppe)] (dppe=1,2-bis(diphenylphosphino)ethane) with d-H2 pen in a 1:1 ratio gave [Au4 (dppe)2 (d-pen)2 ] ([1]), in which two [Au2 (dppe)]2+ units are linked by two d-pen S atoms in a cyclic form so as to have two bidentate-N,O coordination arms. The subsequent reaction of [1] with Cu(OTf)2 afforded [Au4 Cu(dppe)2 (d-pen)2 ]2+ ([2]2+ ), in which a CuII ion is chelated by the two coordination arms in [1] to form an AuI4 CuII bicyclic metallocage. A similar reaction using Cu(NO3 )2 was accompanied by the ring expansion of [1] to [Au8 (dppe)4 (d-pen)4 ], leading to the production of [Au8 Cu2 (dppe)4 (d-pen)4 ]4+ ([3]4+ ). In [3]4+ , two CuII ions are each chelated by the two coordination arms to form an AuI8 CuII2 tricyclic metallocage, accommodating a nitrate ion. The use of Ni(NO3 )2 or Ni(OAc)2 instead of Cu(NO3 )2 commonly gave a tricyclic metallocage of [Au8 Ni2 (dppe)4 (d-pen)4 ]4+ ([4]4+ ), but a water molecule was accommodated inside the AuI8 NiII2 metallocage.

Dielectric Jump and Negative Electrostriction in Metallosupramolecular Ionic Crystals

In natural ionic solids, cationic and anionic species are alternately arranged to minimize electrostatic energy. Aggregation of identical ionic species is commonly prohibited due to the repulsive, long-range nature of Coulombic interactions. Recently, we synthesized unique ionic solids, [Au^I₄Co^III₂(dppe)₂(d-pen)₄]X₂·nH₂O (dppe = 1,2-bis(diphenylphosphino)ethane, d-pen = d-penicillaminate), in which complex cations are self-assembled into a cationic supramolecular octahedron, while monovalent or divalent inorganic anions are aggregated into an anomalous anionic cluster accommodating several water molecules. This quite unusual aggregation manner originates from various molecular-level non-Coulombic interactions such as hydrogen bonds and CH-π interactions; thus, this class of ionic solids is referred to as non-Coulombic ionic solids, abbreviated as NCISs. Herein, we report that the NCISs with a peculiar charge-separated (CS) structure in a cubic lattice show a negative, isotropic electrostriction phenomenon that has never been found in any ionic solids, as well as an anomalously large relaxer-like dielectric jump phenomenon reaching to an application level of ε′/ε₀ ~ 10⁵. The appearance of these phenomena was explained by the cooperative dynamics of inorganic anions and dipolar water molecules in the pliable anionic clusters that are surrounded by a rather robust cationic metallosupramolecular framework with a meso-scopic scale.

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

Heterometallic coordination compounds containing a thiolato dicopper(ii) core increase heterogeneous electrocatalytic activities for water oxidation in proportion to the numbers of vacant dicopper(ii) coordination sites.

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

The heterogeneous catalase-like activity of ionic crystals consisting of Au^I₄Co^III₂ complex cations is studied along with their surface morphologies and oxidation states.

Unique heterogeneous catalase-like activity was observed for metallosupramolecular ionic crystals [Au^I₄Co^III₂(dppe)₂(d-pen)₄]X_n ([1]X_n; dppe = 1,2-bis(diphenylphosphino)ethane; d-pen = d-penicillaminate; X_n = (Cl^–)₂, (ClO₄^–)₂, (NO₃^–)₂ or SO₄^2–) consisting of Au^I₄Co^III₂ complex cations, [1]²⁺, and inorganic anions, X^– or X^2–. Treatment of the ionic crystals with an aqueous H₂O₂ solution led to considerable O₂ evolution with a high turnover frequency of 1.4 × 10⁵ h^–1 for the heterogeneous cobalt complexes, which was dependent on their size and shape as well as the arrangement of cationic and anionic species. These dependencies were rationalized by the presence of cobalt(ii) centers on the crystal surface and their efficient exposure on the (111) plane rather than the (100) plane based on morphological and theoretical studies.

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 and its heterogeneous catalytic activity for electrochemical hydrogen evolution are reported.