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Susumu Kitagawa

Publications and source records attributed to Susumu Kitagawa.

At least 37 records · Page 2Linked to original sources
PubMed2006

Polytypic phase transition in alkyl chain-functionalized valence tautomeric complexes.

A novel series of valence tautomeric (VT) complexes, [Co(Cnbpy)(3,5-DTBQ)2] (Cnbpy = 4,4'-dialkyl-2,2'-bipyridine (alkyl = (C(n)H(2n+1)) where n = 0 (CoC0bpy), 1 (CoC1bpy), 5 (CoC5bpy), 9 (CoC9bpy) and 13 (CoC13bpy); 3,5-DTBQ = 3,5-di-tert-butylsemiquinonate or catecholate), including two previously reported complexes (CoC0bpy and CoC1bpy), were systematically prepared and their properties examined. Introduction of alkyl groups into VT chromophores leads to unexpected variations in the VT process, depending on the lengths of the alkyl chains. An even more interesting observation is that significant polytypic phase transitions with crystallographic symmetry changes accompanying the abrupt VT conversion are induced for the first time in CoC9bpy and CoC13bpy.

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PubMed2005

Synthesis, structures, and magnetic properties of the copper(II), cobalt(II), and manganese(II) complexes with 9-acridinecarboxylate and 4-quinolinecarboxylate ligands.

To explore the relationships between the structures of ligands and their complexes, we have synthesized and characterized a series of metal complexes with two structurally related ligands, 9-acridinecarboxylic acid (HL(1)) and 4-quinolinecarboxylate acid (HL(2)), [Cu(2)(mu(2)-OMe)(2)(L(1))(2)(H(2)O)(0.69)](n) 1, [Cu(2)(L(1))(4)(CH(3)OH)(2)] 2, [Cu(3)(L(1))(6)(CH(3)OH)(6)].3H(2)O 3, [Mn(3)(L(1))(6)(CH(3)OH)(6)].3H(2)O 4, [Co(3)(L(1))(6)(CH(3)OH)(6)].3H(2)O 5, [Cu(L(2))(2)](n) 6, [Mn(L(2))(2)(H(2)O)](n) 7, and [Co(L(2))(2)(H(2)O)](n) 8. 1 is a three-dimensional (3D) polymer with an interpenetrating NbO type network showing one-dimensional (1D) channels, whereas 2 and 3 take bi- and trinuclear structures, respectively, because of the differences in basicity of the reaction systems in preparing the three complexes. 4 and 5 have trinuclear structures similar to that of 3. In 1-5, ligand L(1) performs different coordination modes with N,O-bridging in 1 and O,O'-bridging in 2-5, and the metal ions also show different coordination geometries: square planar in 1, square pyramidal in 2, and octahedral in 3-5. 6 has a two-dimensional structure containing (4,4) grids in which L(2) adopts the N,O-bridging mode and the Cu(II) center takes square planar geometry. 7 and 8 are isostructural complexes showing 1D chain structures, with L(2) adopting the O,O-bridging mode. In addition, the intermolecular O-H...N hydrogen bonds and pi-pi stacking interactions further extend the complexes (except 1 and 6), forming 3D structures. The magnetic properties of 2-7 have been investigated and discussed in detail.

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PubMed2005

Formation and characterization of crystalline molecular arrays of gas molecules in a 1-dimensional ultramicropore of a porous copper coordination polymer.

Molecules and atoms confined in a nanospace may have properties distinctly different from those of the bulk fluid, owing to the formation of a specific molecular array characteristic of nanospace. In situ synchrotron powder X-ray diffraction measurements have been used to observe confined guest molecules such as N2, O2, Ar, and CH4 in the well-regulated ultramicropore of a copper coordination polymer, 1 ([Cu2(pzdc)2pyz]: pzdc = 2,3-pyrazinedicarboxylate and pyz = pyrazine). The obtained crystal structures indicate that guest molecules are confined in a linear fashion to form crystalline-like regular ordered arrays, in contrast to the situation in the gas and liquid state, even at temperatures above the boiling point, and the ordered arrays are characteristic of the kind of gas molecule and the geometrical and potential properties of the ultramicropore of 1.

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PubMed2005

Guest-induced asymmetry in a metal-organic porous solid with reversible single-crystal-to-single-crystal structural transformation.

A metal-organic honeycomb-like 2D pillared-bilayer open framework has been constructed which shows dynamic sponge-like single-crystal-to-single-crystal transformation upon dehydration and rehydration. The dehydrated acentric nonporous phase transformed to the porous centric phase with the selective adsorbate concomitant with the structural transformation correlated with the single-crystal structure determination.

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PubMed2005

Transformation from a 2D stacked layer to 3D interpenetrated framework by changing the spacer functionality: synthesis, structure, adsorption, and magnetic properties.

Two novel coordination polymers of Cu(II), viz. [Cu(bipy)(1,4-napdc)(H2O)2]n and {[Cu(bpe)1.5(1,4-napdc)](H2O)}n (bipy=4,4'-bipyridine; bpe=1,2-bis(4-pyridyl)ethane; 1,4-napdc2-=1,4-naphthalenedicarboxylate), have been synthesized and structurally characterized by changing only the pillar motifs. Both the compounds crystallize by slow evaporation from the ammoniacal solution of the as-synthesized solid. Framework 1 crystallizes in monoclinic crystal system, space group P2/n (No. 13), with a=11.028(19) A, b=11.16(3) A, c=7.678(13) A, beta=103.30(5) degrees, and Z=2. Framework 2 crystallizes in triclinic system, space group, P (No. 2), a=10.613(4) A, b=10.828(10) A, c=13.333(9) A, alpha=85.25(9) degrees, beta=82.59(6) degrees, gamma=60.37(5) degrees, and Z=2. The structure determination reveals that has a 2D network based on rectangular grids, where each Cu(II) is in 4+2 coordination mode. The 2D networks stacked in a staggered manner through the pi-pi interaction to form a 3D supramolecular network. In the case of, a {Cu(bpe)1.5}n ladder connected by 1,4-napdc2- results a 2D cuboidal bilayer network and each bilayer network is interlocked by two adjacent identical network (upper and lower) forming 3-fold interpenetrated 3D framework with small channel along the c-axis, which accommodates two water molecules. The TGA and XRPD measurements reveal that both the frameworks are stable after dehydration. Adsorption measurements (N2, CO2, and different solvents, like H2O, MeOH, etc.) were carried out for both frameworks. Framework shows type-II sorption profile with N2 in contrast to H2O and MeOH, which are chemisorbed in the framework. In case of, only H2O molecules can diffuse into the micropore, whereas N2, CO2, and MeOH cannot be adsorbed, as corroborated by the smaller channel aperture. The low-temperature (300-2 K) magnetic measurement of and reveals that both are weakly antiferromagnetically coupled (J=-1.85 cm-1, g=2.02; J=-0.153 cm-1, g=2.07), which is correlated by the magnetic pathway to the corresponding structure.

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PubMed2005

Pore surface engineering of microporous coordination polymers.

Pore surface control of microporous coordination polymers is of great interest due to the potentially exciting functionalities it presents, such as highly selective separation, chemisorption, and novel catalysts and sensors. A discussion of our unique strategy aimed at surface engineering using metalloligands, i.e., introduction of coordinatively unsaturated metal centers, is presented.

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PubMed2005

Diversity in magnetic properties of 3D isomorphous networks of Co(II) and Mn(II) constructed by napthalene-1,4-dicarboxylate.

Two novel 3D isomorphous organic-inorganic hybrid frameworks, [M(1,4-napdc)]n ( M = Co(II), and Mn(II), ; 1,4-napdcH2 = napthalene-1,4-dicarboxylic acid) have been hydrothermally synthesized and structurally characterized, and the magnetic results exhibit metamagnetic behaviour (TC = 5.5 K), and a weak antiferromagnetic interaction, which are structurally correlated.

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PubMed2005

Highly controlled acetylene accommodation in a metal-organic microporous material.

Metal-organic microporous materials (MOMs) have attracted wide scientific attention owing to their unusual structure and properties, as well as commercial interest due to their potential applications in storage, separation and heterogeneous catalysis. One of the advantages of MOMs compared to other microporous materials, such as activated carbons, is their ability to exhibit a variety of pore surface properties such as hydrophilicity and chirality, as a result of the controlled incorporation of organic functional groups into the pore walls. This capability means that the pore surfaces of MOMs could be designed to adsorb specific molecules; but few design strategies for the adsorption of small molecules have been established so far. Here we report high levels of selective sorption of acetylene molecules as compared to a very similar molecule, carbon dioxide, onto the functionalized surface of a MOM. The acetylene molecules are held at a periodic distance from one another by hydrogen bonding between two non-coordinated oxygen atoms in the nanoscale pore wall of the MOM and the two hydrogen atoms of the acetylene molecule. This permits the stable storage of acetylene at a density 200 times the safe compression limit of free acetylene at room temperature.

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PubMed2005

Effects of countercations on the structures and redox and spectroscopic properties of diruthenium catecholate complexes with ligand-unsupported Ru-Ru bonds.

The molecular structures and physicochemical properties of diruthenium complexes with ligand-unsupported Ru-Ru bonds, generally formulated as [A2{Ru2(DTBCat)4}] (DTB = 3,5- or 3,6-di-tert-butyl; Cat(2-) = catecholate), were studied in detail by changing the countercations. First, the binding structures of the cations in a family of [{A(DME)n}2{Ru2(3,5-DTBCat)4}] (n = 2 for A+ = Li+ and Na+ and n = 1 for A+ = K+ and Rb+) were systematically examined to reveal the effects of the cations on the molecular structures and electrochemical properties. Second, the complex (n-Bu4N)2[Ru2(3,6-DTBCat)4] with a cation-free structure was synthesized using tetra-n-butylammonium cations. The complex clearly demonstrates first that the ligand-unsupported Ru-Ru bonds are essentially stabilized by the dianionic nature of the catecholate derivatives without any other bridging or supporting species. In contrast, the redox potentials and absorption spectra of the complexes can sensitively respond to the countercations depending upon the polarity of the solvents.

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PubMed2005

Substituent-directed structural and physicochemical controls of diruthenium catecholate complexes with ligand-unsupported Ru-Ru bonds.

A family of diruthenium complexes with ligand-unsupported Ru-Ru bonds has been systematically synthesized, and their crystal structures and physical properties have been examined. A simple, useful reaction between Ru2(OAc)4Cl (OAc- = acetate) and catechol derivatives in the presence of bases afforded a variety of diruthenium complexes, generally formulated as [Na(n){Ru2(R4Cat)4}] (n = 2 or 3; R4 = -F4, -Cl4, -Br4, -H4, -3,5-di-t-Bu, and -3,6-di-t-Bu; Cat(2-) = catecholate). The most characteristic feature of the complexes is the formation of short ligand-unsupported Ru-Ru bonds (2.140-2.273 A). These comprehensive studies were carried out to evaluate the effects of the oxidation states and the substituents governing the molecular structures and physicochemical properties. The Ru-Ru bond distances, rotational conformations, and bending structures of the complexes were successfully varied. The results presented in this manuscript clearly demonstrate that the complexes with ligand-unsupported Ru-Ru bonds can sensitively respond to redox reactions and ligand substituents on the basis of the greater degree of freedom in their molecular structures.

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PubMed2005

Synthesis and crystallographic characterization of low-dimensional and porous coordination compounds capable of supramolecular aromatic interaction using the 4,4'-azobis(pyridine) ligand.

Coordination compounds with a 4,4'-azobis(pyridine) (azpy) ligand, {[M2(azpy)6(H2O)5] x 4PF6 x azpy x H2O}n (M = Ni(II) (1) or Co(II) (2)) (0-dimensional (0-D) dimer), {[Zn(azpy)3(H2O)2] x 2PF6 x 2azpy x 4H2O}n (3) (1-dimensional (1-D) fishbone-type chain), {[Ag(azpy)] x PF6}n (4) (1-D linear chain), {[Mn(NCS)2(azpy)2] x azpy}n (5) (2-dimensional (2-D) grid sheet), and {[Ni(NCS)2(azpy)2] x 3toluene}n (6) (2-D grid sheet), were synthesized and structurally characterized. Compounds 1 and 2 have a 0-D dimer motif, in which one M(II) (M(II) = Ni(II) or Co(II)) coordination site is shared by unidentate azpy and H2O ligands, each with half-occupancy, i.e., exhibiting static disorder. Compounds 3 and 4 afford 1-D fishbone-type and 1-D linear chain motifs, respectively. Azpy mediates pi-pi and pi-p interactions between these low-dimensional structures. Compounds 5 and 6 possess a 2-D grid sheet motif. These sheets assemble to form microporous frameworks that incorporate aromatic guests, such as coordination-free azpy (5) and toluene (6). There exist not only pi-pi and pi-p interactions but also CH-pi interactions between the framework azpy ligands and guests. It should be noted that the azpy ligand is a good candidate for the construction of new assembling systems of coordination compounds through its aromatic interactions.

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PubMed2005

Efficient axial chirality induction in biphenyldiol triggered by proton-transferred hydrogen bonding with chiral amine.

Axial chirality was induced in biphenyldiol upon binding chiral amines with the efficiency of chiral induction much improved at low temperature. At low temperatures, two molecules of amine were bound to biphenyldiol. The value of the dissymmetric g-factor increased as proton-transferred hydrogen bonds formed between biphenyldiol and amine. These results indicate that proton-transferred hydrogen bonding plays an important role in constructing a highly ordered chiral assembly.

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PubMed2005

Porous lanthanide-organic framework with zeolite-like topology.

Two novel isomorphous porous frameworks of Ln(III), {[Ln2(imidc)2(H2O)3](H2O)}n, [Ln = Gd(III) (1) and Er(III) (2)] have been synthesized hydrothermally using multifunctional 4,5-imidazoledicarboxylic acid (imidc) as a connector; they have a zeolite-like network topology which can provide another form upon dehydration, and exhibit selective adsorption properties for H2O over N2, CO2 and MeOH.

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