Scan Rate Dependent Spin Crossover Iron(II) Complex with Two Different Relaxations and Thermal Hysteresis fac-[Fe(II)(HL(n-Pr))3]Cl·PF6 (HL(n-Pr) = 2-Methylimidazol-4-yl-methylideneamino-n-propyl).

Solvent-free spin crossover Fe(II) complex fac-[Fe(II)(HL(n-Pr))3]Cl·PF6 was prepared, where HL(n-Pr) denotes 2-methylimidazol-4-yl-methylideneamino-n-propyl. The magnetic susceptibility measurements at scan rate of 0.5 K min(-1) showed two successive spin transition processes consisting of the first spin transition T1 centered at 122 K (T1↑ = 127.

A DNA hybridization sensor based on catalytic response by platinum deposition.

We report a novel electrochemical sensing system for single-stranded DNA (ssDNA) with a specific sequence based on the catalytic reduction of protons with platinum deposited by the electrochemical reduction of chloro-2,2':6',2''-terpyridine platinum(II) chloride dihydrate (Pt complex) on a glassy carbon (GC) electrode. There was no catalytic property observed for proton reduction at the GC electrode, while the platinum deposited by the reduction of the Pt complex shows the catalytic activity of proton reduction. The intercalation of the Pt complex with double-stranded DNA (dsDNA) decreased the concentration of the free Pt complex with a concomitant diminution in the electrochemical catalytic current due to steric hindrance and a decrease in the diffusion coefficient of the intercalated Pt complex.

Preparation of a cellulose-based enzyme membrane using ionic liquid to lengthen the duration of enzyme stability.

A novel method for preparing enzyme membranes was developed. The enzyme was attached onto the electrode surface by dropping the enzyme solution and allowing it to dry. Glucose oxidase was used for entrapment.

A hydrogen bond motif giving a variety of supramolecular assembly structures and spin-crossover behaviors.

A series of spin-crossover (SCO) iron(II) compounds, fac-[Fe(II)(HL(R))(3)]Cl·PF(6) [R = methyl (Me, 1), ethyl (Et, 2), n-propyl (n-Pr, 3), n-butyl (n-Bu, 4), and n-pentyl (n-Pen, 5)], were synthesized, where HL(R) denotes a series of [(2-methylimidazol-4-yl)methylidene]monoalkylamines. The cations fac-[Fe(II)(HL(R))(3)](2+) and chloride anions associate through 3:3 imidazole···chloride hydrogen bonding. This hydrogen-bonding motif gives rise to a variety of assembly structures consisting of a one-dimensional ladder for 3 and 4, two kinds of two-dimensional networks for 1 and 2, and a cubane-like structure for 5.

1D and 2D assembly structures by imidazole···chloride hydrogen bonds of iron(II) complexes [Fe(II)(HL(n-Pr))3]Cl·Y (HL(n-Pr) = 2-methylimidazol-4-yl-methylideneamino-n-propyl; Y = AsF6, BF4) and their spin states.

Two Fe(II) complexes fac-[Fe(II)(HL(n-Pr))(3)]Cl·Y (Y = AsF(6) (1) and BF(4) (2)) were synthesized, where HL(n-Pr) is 2-methylimidazole-4-yl-methylideneamino-n-propyl. Each complex-cation has the same octahedral N(6) geometry coordinated by three bidentate ligands and assumes facial-isomerism, fac-[Fe(II)(HL(n-Pr))(3)](2+) with Δ- and Λ-enantiomorphs. Three imidazole groups per Δ- or Λ-fac-[Fe(II)(HL(n-Pr))(3)](2+) are hydrogen-bonded to three Cl(-) ions or, from the viewpoint of the Cl(-) ion, one Cl(-) ion is hydrogen-bonded to three neighbouring fac-[Fe(II)(HL(n-Pr))(3)](2+) cations.

Enzymatically amplified electrochemical detection for lipopolysaccharide using ferrocene-attached polymyxin B and its analogue.

Ferrocene-attached polymyxin B (PMB-Fc) was prepared by the reaction of polymyxin B with ferrocenoyl chloride in a toluene/pyridine mixture. An electrochemical detection of lipopolysaccharide (LPS) was carried out using a combination of PMB-Fc and an enzyme-modified electrode constructed from a glassy carbon electrode modified with a bovine serum albumin membrane containing glucose oxidase. The ferrocene units of the PMB-Fc molecules were oxidized on the electrode, and then reduced to the original neutral form by a glucose oxidase-catalyzed reaction in the presence of D-glucose.

One-dimensional spin-crossover Iron(II) complexes bridged by intermolecular imidazole-pyridine NH...N hydrogen bonds, [Fe(HL(Me))(3)]X(2) (HL(Me) = (2-methylimidazol-4-yl-methylideneamino-2-ethylpyridine; X = PF(6), ClO(4), BF(4)).

2-Methylimidazol-4-yl-methylideneamino-2-ethylpyridine (abbreviated as HL(Me)) is the 1:1 condensation product of 2-methyl-4-formylimidazole and 2-aminoethylpyridine and functions as a bidentate ligand to the iron(II) ion to produce the 3:1 complexes together with anions, [Fe(HL(Me))(3)]X(2) (X = PF(6) (1), ClO(4) (2), BF(4) (3)). The magnetic susceptibilities, differential scanning calorimetric measurements, and Mossbauer spectral measurements demonstrated that complexes 1, 2, and 3 showed a steep one-step spin crossover (SCO) between the high-spin (HS, S = 2) and low-spin (LS, S = 0) states with small thermal hysteresis. Three complexes have an isomorphous structure and are crystallized in the same monoclinic space group, C2/c, both in the HS and LS states.

One-step and two-step spin-crossover iron(II) complexes of ((2-methylimidazol-4-yl)methylidene)histamine.

A tridentate ligand ((2-methylimidazol-4-yl)methylidene)histamine (abbreviated as H(2)L(2-Me)), that is, the 1:1 condensation product of 2-methyl-4-formylimidazole and histamine, was used for the syntheses of a new family of iron(II) spin-crossover (SCO) complexes with the general chemical formulas [Fe(H(2)L(2-Me))(2)]X(2) x solvent (X = Cl, ClO(4), and BPh(4); solvent = 2-PrOH and CH(3)CN) and [Fe(H(2)L(2-Me))(2)]X x Y x solvent (X = Cl and Br; Y = ClO(4), BF(4), PF(6), and AsF(6); solvent = EtOH and 2-PrOH). The complex cation [Fe(H(2)L(2-Me))(2)](2+) is a chiral species due to an octahedral coordination of two unsymmetrical tridentate ligands, has a ligand field strength around the spin-crossover point, and is hydrogen-bonded to anions to form a variety of network structures. The dichloride complexes [Fe(H(2)L(2-Me))(2)]Cl(2) x 2-PrOH x 0.

Structures and spin states of bis(tridentate)-type mononuclear and triple helicate dinuclear iron(II) complexes of imidazole-4-carbaldehyde azine.

Mononuclear [Fe(H(2)L(R))(2)](2+) and dinuclear [Fe(2)(H(2)L(R))(3)](4+) (R = H, 2-Me, 5-Me) complexes containing the new imidazole-4-carbaldehyde azine ligand (H(2)L(H)) and its derivatives (H(2)L(2-Me) and H(2)L(5-Me)) prepared from the condensation reaction of 4-formylimidazole or 2-methyl- or 5-methyl-4-formylimidazole with hydrazine (2:1) were prepared, and their magnetostructural relationships were studied. In the mononuclear complexes, H(2)L(R) acts as an unsymmetrical tridentate ligand with two imidazole nitrogen atoms and one azine nitrogen atom, while in the dinuclear complexes, H(2)L(R) acts as a dinucleating ligand employing four nitrogen atoms to form a triple helicate. At room temperature, [Fe(2)(H(2)L(H))(3)](ClO(4))(4) and [Fe(2)(H(2)L(2-Me))(3)](ClO(4))(4) were in the high-spin (HS) and low-spin (LS) states, respectively.

Two-dimensional iron(II) spin crossover complex constructed of bifurcated NH...O- hydrogen bonds and pi-pi interactions: [FeII(HLH,Me)2](ClO4)2.1.5MeCN (HLH,Me = imidazol-4-yl-methylidene-8-amino-2-methylquinoline).

A 2D iron(II) spin crossover complex, [FeII(HLH,Me)2](ClO4)2.1.5MeCN (1), was synthesized, where HLH,Me = imidazol-4-yl-methylidene-8-amino-2-methylquinoline.

Electrochemically amplified detection for lipopolysaccharide using ferrocenylboronic acid.

A novel electrochemical technique for lipopolysaccharide (LPS) detection has been developed using a combination of ferrocenylboronic acid derivatives and an enzyme-modified electrode. The enzyme-modified electrode was constructed from a gold electrode modified with a bovine serum albumin membrane containing diaphorase. Ferrocenylboronic acid derivatives are oxidized on the electrode, and then regenerated by a diaphorase-catalyzed reaction in the presence of NADH.

A variety of spin-crossover behaviors depending on the counter anion: two-dimensional complexes constructed by NH...Cl- hydrogen bonds, [FeIIH3LMe]Cl.X (X = PF6 -, AsF6 -, SbF6 -, CF3SO3 -; H3L(Me) = Tris[2-{[(2-methylimidazol-4-yl)methylidene]amino}ethyl]amine).

A family of spin-crossover (SC) complexes, [Fe(II)H(3)L(Me)]Cl.X (X(-) = PF(6) (-), AsF(6) (-), SbF(6) (-), CF(3)SO(3) (-)), 1-4, has been synthesized, in which H(3)L(Me) denotes the hexadentate N(6) tripod-like ligand tris[2-{[(2-methylimidazol-4-yl)methylidene]amino}ethyl]amine, containing three imidazole groups, with a view to establishing the effect of the counter anion on the SC behavior. These complexes have been found to crystallize in the same monoclinic crystal system with similar cell dimensions.

A 2D layered spin crossover complex constructed by NH...Cl- hydrogen bonds: [FeIIH3LMe]Cl.I3 (H3LMe = tris[2-(((2-methylimidazoyl-4-yl)methylidene)amino)ethyl]amine.

A 2D layered spin crossover complex, [FeIIH3L(Me)]Cl.I3, has been synthesized from the reaction of FeIIICl3, a tripod ligand (H3LMe = tris[2-(((2-methylimidazoyl-4-yl)methylidene)amino)ethyl]amine), and NaI in methanol. The compound showed an abrupt spin transition between the HS (S = 2) and LS (S = 0) states at T(1/2) = 110 K without hysteresis.

Supramolecular spin-crossover iron complexes based on imidazole-imidazolate hydrogen bonds.

The [Fe(II)(H(3)L)](BF(4))(2).3H(2)O (1) complex was synthesized, where H(3)L (tris[[2-[(imidazole-4-yl)methylidene]amino]ethyl]amine) is a tripodal ligand obtained by condensation of tris(2-aminoethyl)amine and 4-formylimidazole (fim) in a 1:3 molar ratio. Starting from 1, a series of complexes, [Fe(II)(H(1.

Amperometric measurement of ds-DNA content using a peroxidase-modified electrode.

An enzyme electrode with a chemically amplified response for methylene blue (MB) was constructed from a glassy carbon electrode and a layer containing immobilized horseradish peroxidase (HRP). MB is reduced on the electrode but regenerated through the HRP-catalyzed reaction in the presence of H(2)O(2). The electroreduction/regeneration cycle for MB resulted in an amplified electrode response.

Interlayer interaction of two-dimensional layered spin crossover complexes [FeIIH3L(Me)][FeIIL(Me)]X (X-=ClO4-, BF4-, PF6-, AsF6-, and SbF6-; H3L(Me)=tris[2-(((2-methylimidazol-4-yl)methylidene)amino)ethyl]amine).

A series of two-dimensional (2D) spin crossover complexes, [FeIIH3L(Me)][FeIIL(Me)]X (X-=ClO4-, BF4-, PF6-, AsF6-, SbF6-) 1-5, have been synthesized, where H3L(Me) denotes an hexadentate N6 tripodlike ligand containing three imidazole groups, tris[2-(((2-methylimidazol-4-yl)methylidene)amino)ethyl]amine. Compounds 1-5 exhibit a two-step (HS-[FeIIH3L(Me)](2+) + HS-[FeIIL(Me)]-) <--> (HS-[FeIIH3L(Me)](2+) + LS-[FeIIL(Me)]-) <--> (LS-[FeIIH3L(Me)](2+) + LS-[FeIIL(Me)]-) spin-transition. The crystal structure of [FeIIH3L(Me)][FeIIL(Me)]PF6 (3) was determined at 295, 200, and 100 K.

A new family of spin crossover complexes with a tripod ligand containing three imidazoles: synthesis, characterization, and magnetic properties of [FeIIH3LMe](NO3)2.1.5H2O, [FeIIILMe].3.5H2O, [FeIIH3LMe][FeIILMe]NO3, and [FeIIH3LMe][FeIIILMe](NO3)2 (H3LMe) = Tris[2-(((2-methylimidazol-4-yl)methylidene)amino)ethyl]amine).

A new family of spin crossover complexes, [Fe(II)H(3)L(Me)](NO(3))(2).1.5H(2)O (1), [Fe(III)L(Me)].

Synthesis, Characterization, and Crystal Structure of a (&mgr;-Oxo)bis(&mgr;-acetato)diiron(III) Complex with a Dinucleating Hexapyridine Ligand, 1,2-Bis[2-(bis(2-pyridyl)methyl)-6-pyridyl]ethane. The First Example of a Discrete (&mgr;-Oxo)bis(&mgr;-acetato)diiron(III) Complex with a Dinucleating Ligand.

A mononucleating tripyridine ligand, 2-(bis(2-pyridyl)methyl)-6-methylpyridine (L(1)), and a dinucleating hexapyridine ligand, 1,2-bis[2-(bis(2-pyridyl)methyl)-6-pyridyl]ethane (L(2)), have been prepared. The reaction of a carbanion of 2,6-lutidine with 2-bromopyridine affords L(1) which is converted to L(2) quantitatively by treating with tert-butyllithium and 1,2-dibromoethane. (&mgr;-Oxo)bis(&mgr;-acetato)diiron(III) complexes [Fe(2)(O)(OAc)(2)(L(1))(2)](ClO(4))(2) (1) and [Fe(2)(O)(OAc)(2)L(2)](ClO(4))(2) (2) have been synthesized and characterized by means of infrared, UV/vis, mass, and Mössbauer spectroscopies and by measuring magnetic susceptibility and cyclic voltammograms.