Taka-aki Okamura

Self-Assembly of Frameworks with Specific Topologies: Construction and Anion Exchange Properties of M3L2 Architectures by Tripodal Ligands and Silver(I) Salts

Three five-component architectures, compounds 3, 4, and 5 were obtained by self-assembly of tripodal 1,3,5-tris(imidazol-1-ylmethyl )-2,4,6-trimethylbenzene (6) and 1,3,5-tris(benzimidazol-2-ylmethyl)benzene (7) ligands with silver(I) salts. The structures of these novel complexes have been determined by X-ray crystallography. The results of structural analysis indicate that these frameworks have same M3L2 components, but different structures. Compounds 3 and 4 are both M3L2 type cage-like complexes, while the 5 is an open trinuclear complex. The complex 3 is a cylindrical cage with simultaneous inclusion of a perchlorate anion inside of the cage as a guest molecule. Such guests can be exchanged for other anions through the open edge of the cage as evidenced by crystal structure of 4. The results demonstrate that the molecular M3L2 type cage can act as a host for anions and provide a nice example of supramolecular architectures with interesting properties and possible applications.

Reversible Single-Crystal-to-Single-Crystal Transformation and Highly Selective Adsorption Property of Three-Dimensional Cobalt(II) Frameworks

A three-dimensional (3D) coordination polymer, [Co(3)(L)(2)(BTEC)(H(2)O)(2)]·2H(2)O [1, HL = 3,5-di(imidazol-1-yl)benzoic acid, H(4)BTEC = 1,2,4,5-benzenetetracarboxylic acid], with tfz-d topology has been hydrothermally synthesized. The framework of 1 has high thermal stability and exhibits single-crystal-to-single-crystal (SCSC) transformations upon removing and rebinding the noncoordinated and coordinated water molecules. X-ray crystallographic analyses revealed that the coordination geometry of Co(II) changes from octahedral to square pyramid upon dehydration, accompanying the appearance of one-dimensional (1D) open channels with dimensions of 2.0 × 2.8 Å. The dehydrated form [Co(3)(L)(2)(BTEC)] (2) exhibits highly selective adsorption of water molecules over N(2), CH(3)OH, and CH(3)CH(2)OH, which could be used as sensors for water molecules. Furthermore, the magnetic properties of 1 and 2 were investigated, showing the existence of ferromagnetic interaction between the Co(II) atoms within the trinuclear subunit.

Synthesis and crystal structure of a luminescent infinite 2D brick-wall network with two- and three-coordinate silver(I) atoms and ligand-unsupported silver–silver interactions

Assembly of a novel flexible tetradentate ligand 1,7-bis(4′-pyridyl)-2,6-diazaheptane (py-hep) with silver perchlorate hydrate provides an interesting two-dimensional (2D) brick-wall network: [Ag3(py-hep)2](ClO4)3·0.5CH3CN. The X-ray crystal structural analysis indicates that the framework consists of trigonal and linearly coordinated silver(I) atoms and ligand-unsupported metal–metal interactions. The complex shows photoluminescence in both the solid state and in acetonitrile solution.

Highly oriented aragonite nanocrystal–biopolymer composites in an aragonite brick of the nacreous layer of Pinctada fucata

13C CP/MAS NMR and FE/TEM measurements of the aragonite brick of the nacreous layer of Pinctada fucata indicate that it assembles with highly oriented aragonite nanocrystals, which are regulated by biopolymers.

Construction of coordination frameworks based on 4-imidazolyl tecton 1,4-di(1H-imidazol-4-yl)benzene and varied carboxylic acids

Nine new coordination polymers [Mn(L)(OX)] (1), [Zn(L)(MBDC)] (2), [Zn(L)(BPDA)] (3), [Co3(L)2(BTA)2]·2H2O (4), [Co2(L)2(BTCA)]·2H2O (5), [Ni(L)(e,a-cis-1,2-CHDC)]·2H2O (6), [Co(L)(e,a-cis-1,4-CHDC)] (7), [Co(L)(e,e-trans-1,4-CHDC)]·2H2O (8) and [Co(L)(e,e,e-cis-1,3,5-HCHTC)]·0.45H2O (9) were obtained by reactions of varied metal salts with 1,4-di(1H-imidazol-4-yl)benzene (L) in the presence of corresponding auxiliary ligands of oxalic acid (H2OX), 5-methyl-1,3-benzenedicarboxylic acid (H2MBDC), 4,4′-biphenyldicarboxylic acid (H2BPDA), benzene-1,3,5-triacetic acid (H3BTA), 1,2,4,5-benzenetetracarboxylic acid (H4BTCA), cis-1,2-cyclohexanedicarboxylic acid (cis-1,2-H2CHDC), cis-/trans-1,4-cyclohexanedicarboxylic acid (cis-/trans-1,4-H2CHDC) and cis-1,3,5-cyclohexane tricarboxylic acid (cis-1,3,5-H3CHTC), respectively. Complex 1 has a one-dimensional (1D) chain structure and 2 has a two-dimensional (2D) network with 63-hcb topology. Complex 3 is a complicated uninodal 4-connected three-dimensional (3D) net with Point (Schlafli) symbol (4·6·83·10)(4·63·82)(63·103)(64·82) while 4 is a (3,8)-connected tfz-d 3D net with Point (Schlafli) symbol (43)2(46·618·84) based on the trinuclear Co(II) secondary building units (SBUs). Complex 5 is a 3-fold interpenetrating mog net with Point (Schlafli) symbol of (4·64·8)2(42·62·82), while 6 is a 2D net with (4,4) topology based on binuclear SBUs. In contrast to the 2D network of 7 with e,a-cis-1,4-CHDC2−, 8 with e,e-trans-1,4-CHDC2− is a 5-fold interpenetrating 66-dia 3D net. Complex 9 has a 1D ladder-like chain structure with a stable conformation from the e,e,e-cis-1,3,5-HCHTC2− ligand. Complexes 2 and 3 exhibit intense light blue emission in the solid state at room temperature and the results of magnetic measurements showed that there are antiferromagnetic interactions in 1.

Cadmium(II) coordination polymers with flexible tetradentate ligand 1,2,4,5-tetrakis(imidazol-1-ylmethyl)benzene: anion effect and reversible anion exchange property

Six new three-dimensional (3D) Cd(II) coordination polymers, {[Cd2(L)3](NO3)4·6H2O}n (1), {[Cd2(L)3](ClO4)4·2H2O}n (2), {[Cd2(L)3](BF4)4·2H2O}n (3), {[Cd(L)Cl2]·2H2O}n (4), {[Cd2(L)2(SO4)2(H2O)]·2H2O}n (5) and {[Cd2(L)(SO4)2(H2O)3]·4H2O}n (6), have been solvothermally synthesized by reactions of the corresponding Cd(II) salts with flexible tetradentate ligand 1,2,4,5-tetrakis(imidazol-1-ylmethyl)benzene (L), respectively. The X-ray diffraction analysis revealed that the isostructural 1, 2 and 3 have 3D framework structures with (46·66·83)2(42·63·8)3 topology. Complex 4 has a different 3D framework structure with (65·8) topology, while 5 and 6 possess pillared-layer and plywood-like 3D framework structures, respectively. The distinct structures of 1 (2, 3), 4 and 5 indicate that the counter anions with different coordination abilities play an important role in the formation of coordination polymers. Complexes 5 and 6, synthesized by the same reactants in the same solvent, have different structures due to the different metal/ligand ratio. In addition, the results also demonstrated that the flexible tetradentate ligand L can adopt varied conformations and coordination modes to form complexes with different structures. L adopts up,up,down,down-conformation in 1–3, while in 4, it has a up,down-conformation. It is interesting that two different conformations of up,down,down,up- and H-type of L coexist in 5. In the case of 6, L has H-type conformation. Furthermore, the reversible anion exchange property of 1 was studied.

Novel Pb(ii) coordination frameworks: synthesis, crystal structures and unusual third-order nonlinear optical propertiesElectronic supplementary information (ESI) available: crystal packing diagram of complex 2. See http://www.rsc.org/suppdata/jm/b3/b315682f/

Three novel Pb(II) coordination complexes, [Pb(dimb)(DMF)(NO3)2]n1, [Pb(dimb)(SCN)2]n2 [dimb = 1,3-bis(imidazol-1-ylmethyl)-benzene], {[Pb(bimb)1.5(NO3)2](DMF)}n3 [bimb = 4,4′-bis(imidazol-1-methyl)-biphenyl], were synthesized and characterized by X-ray crystallography. Complex 1 exhibits a one-dimensional (1D) zigzag chain structure, which has two crystallographically independent Pb(II) atom centers. Complex 2 possesses a two-dimensional (2D) corrugated network, which contains 24-membered M2L2 metallocyclic rings. Complex 3 has a 1D infinite non-interpenetrated molecular ladder, which has very large cavities with dimensions of 17.89 × 20.34 A, and DMF molecules fill the channel formed by adjacent two ladders. The third-order nonlinear optical (NLO) properties of the three complexes were measured by a Z-scan technique in DMF solution. All three complexes possess weak absorption and strong refraction. Their third-order NLO refractive coefficients, n2, are −5.96 × 10−19 m2 W−1 for 1, −8.34 × 10−19 m2 W−1 for 2, and −7.15 × 10−19 m2 W−1 for 3. It is notable that two Pb(II) complexes 1 and 3 with 1D structure show strong self-defocusing behavior, which are different from the reported 1D coordination complexes containing d10 metal ions; also, complex 2 is the first 2D coordination compound that possesses strong self-defocusing behavior. The χ(3) values of complexes 1, 2 and 3 were calculated to be 4.46 × 10−13, 6.25 × 10−13 and 5.42 × 10−13 esu, respectively.

Syntheses and crystal structures of 1D tubular chains and 2D polycatenanes built from the asymmetric 1-(1-imidazolyl)-4-(imidazol-1-ylmethyl)benzene ligand with metal salts

Reactions of a new asymmetric ligand, 1-(1-imidazolyl)-4-(imidazol-1-ylmethyl)benzene (IIMB), with various metal [Cd(II), Mn(II), Zn(II)] salts led to the formation of molecular, one- (1D) and two-dimensional (2D) architectures [Cd(IIMB)2(H2O)(SO4)]·7.5H2O 1, [Cd(IIMB)2Cl2]·H2O 2, [Cd(IIMB)4(H2O)2](NO3)2·5H2O 3, [Cd(IIMB)(OAc)2]·H2O 4, [Mn(IIMB)2(SO4)(H2O)]·8.2H2O 5, [Mn(IIMB)4(H2O)2]Cl2·5H2O 6 and [Zn(IIMB)2]4(NO3)8·13.5H2O 7. All the structures were established by single-crystal X-ray diffraction analysis. Both compounds 1 and 5 with sulfate anion are 2D polycatenanes formed by the interlocking of 1D double-stranded chains, while 2 and 4 with chloride and acetate anions are 1D chains. The results provide nice examples of topologies of metal-organic frameworks controlled by the counter anions. Interestingly, 3 and 6 are discrete molecular complexes with monometallic cores and form 2D networks through strong intermolecular hydrogen bonds. Complex 7, obtained under the same conditions as 3, is a 1D tubular chain. The structural difference between 3 and 7 suggests the metal ions also have a significant effect on the construction of supramolecular architectures. Furthermore, the photoluminescence properties of these compounds were investigated in the solid state at room temperature.

Three-dimensional photoluminescent pillared metal-organic framework with 4.82 topological channels obtained from the assembly of cadmium(II) acetate and trimellitic salt

Reaction of the piperidinium salt of trimellitic acid (BTC3−) with cadmium(II) acetate dihydrate yields an unprecedented 3D pillared metal-organic framework, [Cd3(BTC)2(H2O)6]·3H2O, showing strong blue luminescence. The framework contains 4.82 topological channels, in which the ‘floors’ are directly connected by the pillars of the BTC3− benzene rings.

First example of a dumbbell-like architecture containing M3L2 cages and terephthalate anions

A novel complex [Ag3(titmb)2]2[1,4-C6H4(COO)2]3·23 H2O [titmb = 1,3,5-tris(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene] contains two M3L2 cages and three terephthalate anions, one of which is embedded in the two cages to form a dumbbell-like architecture and shows photoluminescence in the solid state when the titmb reacts with [Ag(NH3)2]NO3, an individual M3L2 cage [Ag3(titmb)2][NO3]3·5 H2O without luminescent properties was obtained.