Showing papers by "Susumu Kitagawa published in 2003"
942 citations
TL;DR: Measurement of the critical temperature where PB nanoparticles exhibit a ferromagnetic property showed a gradual decrease of Tc for the nanoparticles as the particle sizes become smaller, which could be ascribed to the reduction of the averaged numbers of magnetic interacted neighbors.
Abstract: Prussian blue (PB) nanoparticles protected by poly(vinylpyrrolidone) (PVP) were prepared by mixing aqueous Fe2+, Fe(CN)63-, and PVP solutions together and were characterized by UV−vis, IR, XRPD, and TEM. Averaged dimensions of the nanoparticles were controlled between 12 and 27 nm depending on initial Fe ion concentrations and feed ratios of Fe ion to PVP. Solubility of PB bulk in organic solvents is considerably low; nevertheless, formations of the PB nanoparticles dramatically increase the solubility in a variety of organic solvents. It is noteworthy that the PVP-protected PB nanoparticles stably maintain the cluster formations without further aggregations and dissociation in CHCl3 over 1 month. Measurement of the critical temperature (Tc) where PB nanoparticles exhibit a ferromagnetic property showed a gradual decrease of Tc for the nanoparticles as the particle sizes become smaller. This result could be ascribed to the reduction of the averaged numbers of magnetic interacted neighbors.
391 citations
TL;DR: In this paper, a three-dimensional coordination polymer with a mixed-valence localized copper(I,II) dimeric unit, [Cu2(4pya)3]n (4-pya = 4-pyridinecarboxylate), was synthesized via a simultaneous in-situa redox and hydrolysis reaction of Cu(II) and 4-cyanopyridine and crystallographically characterized to be a twofold interpenetrated threedimensional coordination network with a cubic [Cu16(4 pya)12] building unit.
143 citations
TL;DR: In this article, metal complexes of haxaazatriphenylene (hat) and its derivatives are reviewed, focusing on assembled structures based on their X-ray crystallographic structures.
99 citations
TL;DR: In this paper, a new family of cubic-like [M(dca)3]− networks (dca = dicyanamide) was constructed and structurally characterized by X-ray crystallography.
Abstract: A new family of three-dimensional cubic-like [M(dca)3]− networks (dca = dicyanamide) templated by appropriate cations has been constructed and structurally characterized by X-ray crystallography.
62 citations
TL;DR: In this article, the synthesis and crystal structures of three new compounds, which have trans-, cis-, and dimer geometries bearing a common motif [Cu(Hsal)2(4,4-bipy)n] leading to ladder, zig-zag, and linear one-dimensional networks, were reported.
47 citations
TL;DR: Mössbauer spectroscopy suggests that the anionic layer of iron-chloranilate has a valence-trapped mixed-valence state and the EPR spectrum of 4 shows two types of signals with g = 2.008 indicating the radical form of TTF.
Abstract: Novel intercalation compounds constructed from the common two-dimensional hydrogen-bond-supported layers and functional guests [(H(0.5)phz)(2)[Fe(CA)(2)(H(2)O)(2)].2H(2)O](n)(1), ([Fe(Cp)(2)][Fe(CA)(2)(H(2)O)(2)])(n)(2), ([Fe(Cp*)(2)][Fe(CA)(2)(H(2)O)(2)])(n)(3), and [(TTF)(2)[Fe(CA)(2)(H(2)O)(2)]](n)(4) (H(2)CA = chloranilic acid, phz = phenazine, [Fe(Cp)(2)] = ferrocene, [Fe(Cp*)(2)] = decamethylferrocene, TTF = tetrathiafulvalene) are described. The guest cations are introduced between the ([Fe(CA)(2)(H(2)O)(2)](m-))(l) layers by electrostatic (1-4) and pi-pi stacking (3, 4) interactions. [Fe(Cp*)(2)](+) cations in 3 are stacked on each other making tilted columns which are included in the channel created by the chlorine atoms of CA(2-) dianions. TTF cations in 4 are stacked face to face with two types of S...S distances (type A; 3.579(3) A, and type B; 3.618(3) A) making a columnar structure. The TTF cations in the stacked column have a head-to-tail arrangement with respect to the iron-chloranilate layer. Mossbauer spectroscopy suggests that [Fe(CA)(2)(H(2)O)(2)](m-) anion in 3 is consistent with high-spin (S = 5/2) iron(III) ions and [Fe(Cp*)(2)](+) in the low-spin (S = 1/2) iron(III) ions. In 4, Mossbauer spectroscopy shows high-spin iron(II) ions (IS = 1.10 mm.s(-1) and QS = 1.66 mm.s(-1) at 297 K) and high-spin iron(III) ions (IS = 0.42 mm.s(-1) and QS = 1.27 mm.s(-1) at 297 K), suggesting that the anionic layer of iron-chloranilate has a valence-trapped mixed-valence state. At the temperature range of 77-300 K, the compounds 1, 2, and 3 are EPR silent, whereas the EPR spectrum of 4 shows two types of signals with g = 2.008 indicating the radical form of TTF.
45 citations
TL;DR: An interesting ferromagnetic linear trinuclear copper(II) compound containing an in-situ synthesised functional ligand has been rationally obtained and crystallographically characterised, confirming a new route to magnetic polynuclear clusters as discussed by the authors.
Abstract: An interesting ferromagnetic linear trinuclear copper(II) compound containing an in-situ synthesised functional ligand has been rationally obtained and crystallographically characterised, confirming a new route to magnetic polynuclear clusters. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
41 citations
TL;DR: The metalloporphyrin receptor having 8-quinolyl groups and o-carbomethoxymethoxyphenyl groups, where these Lewis basic parts serve as the cooperative hydrogen bonding sites for the hydroxyl groups of glucoside, demonstrates importance of formation of a highly ordered hydrogen bonding network between the receptor and the guest.
Abstract: Oxophilic synthetic receptors were designed and synthesized using a porphyrin scaffold, with the aim of constructing a preorganized complementary binding site for phenols and carbohydrates. We pursued three strategies for phenol recognition: (1) Lewis acid/Lewis base combinations serving as a hydrogen bond donor and acceptor for the OH group, (2) Lewis base/π-π stacking, targeting both the OH group and the aromatic moiety of phenols, and (3) exchange of the axial hydroxyl ligand on a trivalent and oxophilic metal center of aluminum porphyrin. For the recognition of acidic phenols, the most promising recognition motif was Lewis base/π-π stacking, which can bind to phenols with a hydrogen bond and π-π stacking interactions. [5-(8-Quinolyl)-10,15,20-triphenylporphyrinato]zinc binds to p-nitrophenol with a binding constant of 540 M-1 in CHCl3 at 25 °C. For carbohydrate recognition, we designed the metalloporphyrin receptor having 8-quinolyl groups and o-carbomethoxymethoxyphenyl groups, where these Lewis bas...
38 citations
TL;DR: These features of water-soluble receptors consisting of a rigid framework and flexible side chains with a large solvent-accessible area are in contrast to highly preorganized rigid receptors, and they can provide useful guidelines for rational design of induced-fit artificial receptors in water.
Abstract: Water-soluble zinc bisporphyrin receptors 1 and 2 having two Lewis acidic sites (zinc) in the hydrophobic environment consisting of alkyl chains and a bisporphyrin framework, and covered with hydrophilic exterior (twelve or eighteen carboxyl groups) were prepared. The receptors show high affinity for diamines and DNA intercalators in water where the binding constants Ka are of the order of 107 and 108 M−1, respectively. Diamines and DNA intercalators are bound to the receptor through different mechanisms. Diamines are bound through hydrophobic interactions and zinc–nitrogen interactions, while DNA intercalators are bound through hydrophobic interactions and charge-transfer interactions. Flexible alkyl chains can make van der Waals contact with guests and create a hydrophobic environment around the bound guest by an induced-fit-type mechanism. For the binding of DNA intercalators, the following features are noteworthy: 1) Binding constants are similar between the zinc porphyrins and zinc-free porphyrins; 2) the binding constant is larger for the guest having the lower LUMO; this indicates the important contribution of charge-transfer interactions to binding; 3) the hydrophobic and cationic nature of DNA intercalators is substantially important, and 4) higher ionic strength reduced the binding affinities; this shows a moderate contribution of electrostatic interactions. The conformational instability of the receptors also contributes to the tight binding: hydrophobic and electrostatic interactions cannot both be favorable at the same time in the guest-free receptor. Enthalpy–entropy compensation observed for the binding of diamines and DNA intercalators is characterized by a relatively small slope (α=0.74) and a large intercept (β=7.75 kcal mol−1) in the ΔH ° versus TΔS ° plot; this shows that a conformational change of receptors and a significant desolvation occur upon binding. The receptor can competitively bind to propidium iodide to deprive DNA of the intercalated propidium iodide. These features of water-soluble receptors consisting of a rigid framework and flexible side chains with a large solvent-accessible area are in contrast to highly preorganized rigid receptors, and they can provide useful guidelines for rational design of induced-fit artificial receptors in water.
30 citations
TL;DR: In this paper, the reaction of di-2-pyridylketone oxime (dpko) in the presence of VCl3(THF)3 results in di-pi-dimitri-methyl ethyl ether (adpe) with ethanol and amino-di-2pyrinidyl-methyl methyl ether with methanol, all of which are monomers with a VOCl2 common unit.
TL;DR: In this article, two novel complexes, [Cu2(Hsal)4(4,4′-bipyridine)(H2O)2(DMF)2] (1) (H2sal=salicylic acid) and {[Cu[Hsal]2.4, 4, 4′]-bipryridine)](H 2O)(H 2sal)}n (2), were synthesized by layered-solution method and structurally characterized.
TL;DR: In this article, a novel Cu(I) complexes containing a μ2-η2, η2-type benzoquinone ligand were synthesized and crystallography-cally characterized.
Abstract: Novel Cu(I) complexes containing a μ2-η2,η2-type benzoquinone ligand have been synthesized and crystallographycally characterized These complexes are synthesized by the redox reaction of a copper−quinonoid pair and may indicate a significant intermediate in the Cu−BQ catalytic system Moreover, this study is regarded as one of the good examples in the Cu(I)−olefin family of enhanced π-back-donation
TL;DR: The artificial receptor bearing decamethylene groups bridging the porphyrin framework and the hydrophilic poly(ethylene oxide) auxiliary groups showed incremental binding free energy of 3.5 kJ mol(-1) per CH2 for 4-alkylpyridines, demonstrating that an ideal hydrophobic environment for the recognition of an alkyl group is constructed in water.
TL;DR: The combination of salicylic acid and 4-aminopyridine leads to a 3D hydrogen bonding network and the replacement of 4-amino acid with 4,4′-bipyridine yields the same topological net with big channels via coordination.
Abstract: The combination of salicylic acid and 4-aminopyridine leads to a 3D hydrogen bonding network while the replacement of 4-aminopyridine with 4,4′-bipyridine yields the same topological net with big channels via coordination.
TL;DR: In this paper, the binding constants of water-soluble zinc bisporphyrin receptors with two Lewis acidic sites (zinc) in the hydrophobic environment were investigated.
Abstract: Water-soluble zinc bisporphyrin receptors 1 and 2 having two Lewis acidic sites (zinc) in the hydrophobic environment consisting of alkyl chains and a bisporphyrin framework, and covered with hydrophilic exterior (twelve or eighteen carboxyl groups) were prepared. The receptors show high affinity for diamines and DNA intercalators in water where the binding constants Ka are of the order of 107 and 108 M−1, respectively. Diamines and DNA intercalators are bound to the receptor through different mechanisms. Diamines are bound through hydrophobic interactions and zinc–nitrogen interactions, while DNA intercalators are bound through hydrophobic interactions and charge-transfer interactions. Flexible alkyl chains can make van der Waals contact with guests and create a hydrophobic environment around the bound guest by an induced-fit-type mechanism. For the binding of DNA intercalators, the following features are noteworthy: 1) Binding constants are similar between the zinc porphyrins and zinc-free porphyrins; 2) the binding constant is larger for the guest having the lower LUMO; this indicates the important contribution of charge-transfer interactions to binding; 3) the hydrophobic and cationic nature of DNA intercalators is substantially important, and 4) higher ionic strength reduced the binding affinities; this shows a moderate contribution of electrostatic interactions. The conformational instability of the receptors also contributes to the tight binding: hydrophobic and electrostatic interactions cannot both be favorable at the same time in the guest-free receptor. Enthalpy–entropy compensation observed for the binding of diamines and DNA intercalators is characterized by a relatively small slope (α=0.74) and a large intercept (β=7.75 kcal mol−1) in the ΔH ° versus TΔS ° plot; this shows that a conformational change of receptors and a significant desolvation occur upon binding. The receptor can competitively bind to propidium iodide to deprive DNA of the intercalated propidium iodide. These features of water-soluble receptors consisting of a rigid framework and flexible side chains with a large solvent-accessible area are in contrast to highly preorganized rigid receptors, and they can provide useful guidelines for rational design of induced-fit artificial receptors in water.