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Yasuaki Einaga

Publications and source records attributed to Yasuaki Einaga.

17 recordsLinked to original sources
PubMed2006

Extremely long axial Cu-N bonds in chiral one-dimensional zigzag cyanide-bridged Cu(II)(-)Ni(II) and Cu(II)(-)Pt(II) bimetallic assemblies.

Preparations, crystal structures, and spectral and magnetic properties of two new chiral one-dimensional cyano-bridged coordination polymers, [Cu(II)L2]M(II)(CN)].2H2O (M(II) = Ni(II) (1) and Pt(II) (2), L = trans-cyclohexane-(1R,2R)-diamine) have been presented. Complex 1 crystallizes in the monoclinic P2(1) space group with a = 9.864(4) A, b = 15.393(8) A, c = 7.995(4) A, beta = 110.32(3) degrees , V = 1138.4(10) A3, and Z = 2, while 2 crystallizes in the monoclinic P2(1) space group with a = 9.899(3) A, b = 15.541(4) A, c = 8.102(2) A, beta = 111.02(2) degrees , V = 1163.6(5) A3, and Z = 2. The unique zigzag cyano-bridged chains along the crystallographic b axis consist of alternate chiral [CuL(2)]2+ cations and square-planar [M(CN)4]2- anions. One side of the axial Cu-N(triple bond C) bond distances are 2.324(6) and 2.34(1) A with Cu-N[triple bond]C angles of 137.8(6) degrees and 138.2(9) degrees for 1 and 2, respectively. On the other hand, the opposite side of the axial Cu-N(triple bond C) bond distances are 3.120(8) and 3.09(1) A with significantly large bent Cu-N[triple bond]C angles of 97.9(5) degrees and 96.8(7) degrees for 1 and 2, respectively. The novel axial bonding features of extremely long semi-coordination Cu-N bonds are attributed to coexistence of pseudo-Jahn-Teller elongation and electrostatic interaction in the unique zigzag cyano-bridged chains. The characteristic bonding features with overlap between small 3d (Ni(II)) or large 5d (Pt(II)) and 3d (Cu(II)) orbitals results in larger shifts in XPS peaks of not only Cu2p(1/2) and Cu2p(3/2) but also Ni2p(1/2) and Ni2p(3/2) for 1 than those of 2, which is also consistent with weak antiferromagnetic interactions with Weiss constants of -5.31 and -5.94 K for 1 and 2, respectively. The d-d, pi-pi*, and CT bands in the electronic, CD, and MCD spectra for 1 and 2 in the solid state at room temperature are discussed from the viewpoint of magneto-optical properties.

Journal Article↗
PubMed2006

Selective detection method derived from a controlled diffusion process at metal-modified diamond electrodes.

A novel, selective methodology is derived based on the difference between the diffusion processes at microelectrodes (i.e., hemispherical diffusion) and the macroelectrode (i.e., linear diffusion) in a metal-implanted boron-doped diamond electrode (metal-BDDs). As an example, the selective detection of glucose in a solution containing interference species such as ascorbic acid and uric acid is demonstrated. The electrochemical properties of BDD, which are low background current, extremely high stability, and (especially) inactivity toward glucose, play an important role in realizing these differences in the diffusion characteristics. The present methodology can be applied not only to selective glucose detection by the metal-BDD system but also to other selective detection systems.

Ascorbic Acid↗
PubMed2006

Electrochemical detection of arsenic(III) using iridium-implanted boron-doped diamond electrodes.

Iridium-modified, boron-doped diamond electrodes fabricated by an ion implantation method have been developed for electrochemical detection of arsenite (As(III)). Ir+ ions were implanted with an energy of 800 keV and a dose of 10(15) ion cm(-2). An annealing treatment at 850 degrees C for 45 min in H2 plasma (80 Torr) was required to rearrange metastable diamond produced by an implantation process. Characterization was investigated by SEM, AFM, Raman, and X-ray photoelectron spectroscopy. Cyclic voltammetry and flow injection analysis with amperometric detection were used to study the electrochemical reaction. The electrodes exhibited high catalytic activity toward As(III) oxidation with the detection limit (S/N = 3), sensitivity, and linearity of 20 nM (1.5 ppb), 93 nA microM(-1) cm(-2), and 0.999, respectively. The precision for 10 replicate determinations of 50 microM As(III) was 4.56% relative standard deviation. The advantageous properties of the electrodes were its inherent stability with a very low background current. The electrode was applicable for analysis of spiked arsenic in tap water containing a significant amount of various ion elements. The results indicate that the metal-implanted method could be promising for controlling the electrochemical properties of diamond electrodes.

Arsenites↗
PubMed2006

Photocontrolled magnetization of CdS-modified Prussian blue nanoparticles.

The first photocontrollable magnetic nanoparticles containing CdS and Prussian blue (PB) have been created using reverse micelles as nanoreactors. Photoinduced electron transfer from CdS to PB in the reverse micelle changed the magnetic properties of the composite nanoparticles from ferromagnetic to paramagnetic. The magnetization in the ferromagnetic region below 4 K was substantially decreased after UV light illumination and could be restored almost to its original level by thermal treatment at room temperature. This novel strategy of designing composite nanoparticles containing photoconductive semiconductors and magnetic materials to create photoswitchable magnetic materials may open many possibilities in the development of magneto-optical devices.

Journal Article↗
PubMed2006

Electrical conductivity modulation coupled to a high-spin-low-spin conversion in the molecular system [FeIII(qsal)2][Ni(dmit)2]3.CH3CN.H2O.

The synergy between the electrical conductivity within the stacks of Ni(dmit)2 in the newly electrocrystallized [Fe(qsal)2][Ni(dmit)2]3.CH3CN.H2O and the spin conversion of Fe(qsal)2 is evidenced. In addition, the presence of a light-induced excited spin state trapping effect suggests that this complex is a prototypal photoswitchable spin-crossover molecular conductor.

Journal Article↗
PubMed2006

Electrochemical oxidation of oxalic acid at highly boron-doped diamond electrodes.

Electrochemical oxidation of oxalic acid has been investigated at bare, highly boron-doped diamond electrodes. Cyclic voltammetry and flow injection analysis with amperometric detection were used to study the electrochemical reaction. Hydrogen-terminated diamonds exhibited well-defined peaks of oxalic acid oxidation in a wide pH range. A good linear response was observed for a concentration range from 50 nM to 10 microM, with an estimated detection limit of approximately 0.5 nM (S/N = 3). In contrast, oxygen-terminated diamonds showed no response for oxalic acid oxidation inside the potential window, indicating that surface termination contributed highly to the control of the oxidation reaction. An investigation with glassy carbon electrodes was conducted to confirm the surface termination effect on oxalic acid oxidation. Although a hydrogen-terminated glassy carbon electrode showed an enhancement of signal-to-background ratio in comparison with untreated glassy carbon, less stability of the current responses was observed than that at hydrogen-terminated diamond.

Boron↗
PubMed2005

Observation of the anisotropic photoinduced magnetization effect in Co-Fe Prussian blue thin films fabricated by using clay Langmuir-Blodgett films as a template.

Thin films of cobalt-iron cyanide (Co-Fe Prussian blue) have been fabricated by means of the modified Langmuir-Blodgett (LB) method using a smectite clay mineral (montmorillonite). In this combined method, clay LB films play a template role in the formation of the Co-Fe Prussian blue thin layer. The films were revealed to possess a well-organized structure not only in perpendicular directions to the film surface but also in parallel directions to the film surface. The photoinduced electron transfer from the iron ion to the cobalt through the bridging cyanide in the films occurred at low temperature (8 K), similar to that in the bulk Co-Fe Prussian blue. The films clearly exhibited magnetic anisotropy with regards to the direction of the applied magnetic field. Moreover, the photoinduced magnetization effect in the films was also found to be anisotropic.

Journal Article↗
PubMed2005

Diaqua[N,N'-bis(5-methoxysalicylidene)ethylenediaminato-kappa(4)O,N,N',O']manganese(III) perchlorate, aqua[N,N'-bis(3,5-dichlorosalicylidene)ethylenediaminato-kappa4O,N,N',O'](methanol-kappaO)manganese(III) perchlorate and bis[mu-N,N'-bis(3-methoxysalicylidene)ethylenediaminato-kappa5O,N,N',O':O]bis[(methanol-kappaO)manganese(III)] diperchlorate.

The title compounds, a hydrogen-bonded linear chain, [Mn(C18H18N2O4)(H2O)2]ClO4, (I), a hydrogen-bonded pseudo-dimer, [Mn(C16H10Cl4N2O2)(CH4O)(H2O)]ClO4, (II), and a dimer, [Mn2(C18H18N2O4)2(CH4O)2](ClO4)2, (III), respectively, have been structurally characterized. The three complexes are completely different in their structural features, despite identical counter-anions and only slight modification of the substituents in the ligands. Complex (I) affords an elongated octahedral coordination environment, with axial Mn-O(water) distances of 2.259 (3) and 2.313 (3) A, which forms hydrogen-bonded linear chains along the crystallographic c axis. Hydrogen-bonded pseudo-dimeric compound (II) also affords an elongated octahedral coordination environment, with axial Mn-O(CH3OH) = 2.222 (3) A and Mn-O(water) = 2.266 (3) A. Dimeric complex (III) is centrosymmetric and consists of distorted octahedral Mn atoms, with axial Mn-O(CH3OH) = 2.242 (2) A and Mn-O(phenolate) = 2.348 (1) A, connected via bridging O atoms from one of the ligands. The magnetic properties of the three complexes are described.

Journal Article↗
PubMed2005

trans-Bis(2,2-diphenylethylamine-kappaN)bis(5,5-diphenylhydantoinato-kappaN3)copper(II) and its chloroform disolvate.

The crystal structures of the title compounds, [Cu(C15H11N2O2)2(C14H15N)2] and [Cu(C15H11N2O2)2(C14H15N)2].2CHCl3, respectively, have been determined. The red disolvate complex affords a square-planar CuN4 coordination environment in which the CuII atom lies on a centre of symmetry. The blue solvent-free complex affords a distorted square-pyramidal CuN4O coordination environment and adjacent molecules form centrosymmetric dimers. A comparison of the different crystal structures focuses on the role of the solvent molecules in supramolecular assemblies of the copper(II) complexes.

Journal Article↗
PubMed2005

Electroanalysis of tetracycline using nickel-implanted boron-doped diamond thin film electrode applied to flow injection system.

The electrochemical analysis of tetracycline was investigated using nickel-implanted boron-doped diamond thin film electrode by cyclic voltammetry and amperometry with a flow injection system. Cyclic voltammetry was used to study the electrochemical oxidation of tetracycline. Comparison experiments were carried out using as-deposited boron-doped diamond thin film electrode (BDD). Nickel-implanted boron-doped diamond thin film electrode (Ni-DIA) provided well-resolved oxidation irreversible cyclic voltammograms. The current signals were higher than those obtained using the as-deposited BDD electrode. Results using nickel-implanted boron-doped diamond thin film electrode in flow injection system coupled with amperometric detection are presented. The optimum potential for tetracycline was 1.55 V versus Ag/AgCl. The linear range of 1.0 to 100 microM and the detection limit of 10 nM were obtained. In addition, the application for drug formulation was also investigated.

Anti-Bacterial Agents↗
PubMed2004

Bis[(R)-3,5-dichloro-N-(1-phenylethyl)salicylideneaminato-kappa2N,O]copper(II) and bis[(R)-3-ethoxy-N-(1-phenylethyl)salicylideneaminato-kappa2N,O]copper(II).

The title compounds, [Cu(C(15)H(12)Cl(2)NO)(2)], (I), and [Cu(C(17)H(18)NO(2))(2)], (II), both adopt a compressed tetrahedral trans-[CuN(2)O(2)] coordination geometry, the molecules having an umbrella conformation overall. These complexes differ from one another with respect to the 1-phenylethylamine moieties, the direction of the benzene rings being either inside [in (I)] or inside and outside [in (II)] of the molecules. The crystals of (I) and (II) have Delta(R,R) and Lambda(R,R) absolute configurations, respectively.

Journal Article↗
PubMed2004

Racemic 3,5-dichloro-2-[[(1-phenylethyl)imino]methyl]phenol.

The title compound, (RS)-3,5-dichloro-2-[[(1-phenylethyl)imino]methyl]phenol, C(15)H(13)Cl(2)NO, was synthesized from racemic 1-phenylethylamine and 3,5-dichlorosalicylaldehyde. The pi-conjugate system around the imine group is essentially planar in the phenol-imine tautomer. Intramolecular O...N hydrogen-bond and intermolecular C-H...pi interactions are present in the crystal structure.

Journal Article↗
PubMed2004

Electric-field-induced conductance switching in FeCo Prussian blue analogues.

FeCo Prussian blue analogues, which are known as typical molecule-based magnets, exhibited abrupt conductance switching by applying a high electric field as well as by varying the temperature. The current density versus electric field (J-E) curves of FeCo Prussian blue with Rb cations in interstitial sites shows so-called negative resistance effects at electric fields higher than the threshold voltage. This means that the FeCo Prussian blue analogues are multiproperty materials in the sense that their conducting, magnetic, and optical properties can be reversibly controlled by certain external stimuli.

Journal Article↗
PubMed2004

Bis(acetone-kappaO)bis(N,N'-dimethylethylenediamine-kappa(2)N,N')copper(II) diperchlorate.

The title compound, [Cu(C(4)H(12)N(2))(2)(C(3)H(6)O)(2)](ClO(4))(2), is the first structurally characterized Cu(II) complex having acetone as axial ligands. The complex adopts an elongated octahedral trans-[CuN(4)O(2)] coordination geometry, with the Cu atom having 222 site symmetry. The axial Cu-O(acetone) and in-plane Cu-N bond lengths are 2.507 (5) and 2.041 (3) A, respectively.

Journal Article↗
PubMed2003

Photoinduced magnetization of the cyano-bridged 3d-4f heterobimetallic assembly Nd(DMF)(4)(H(2)O)(3)(micro-CN)Fe(CN)(5).H(2)O (DMF = N,N-dimethylformamide).

Photoinduced magnetization of the cyano-bridged 3d-4f heterobimetallic assembly Nd(DMF)4(H2O)3(mu-CN)Fe(CN)5.H2O (1) (DMF = N,N-dimethylformamide) is described in this paper. The chiMT values are enhanced by about 45% after UV light illumination in the temperature range of 5-50 K. We propose that UV light illumination induces a structural distortion in 1. This small structural change is propagated by molecular interactions in the inorganic network. Furthermore, the cooperativity resulting from the molecular interaction functions to increase the activation energy of the relaxation processes, which makes observation of the photoexcited state possible. The flexible network structure through the hydrogen bonds in 1 plays an essential role for the photoinduced phenomenon. This finding may open up a new domain for developing the molecule-based magnetic materials.

Journal Article↗