Solution and single crystal raman spectra of potassium hexacyanochromate(III)

Some inconsistency has existed in the assignment of the vibrational spectra of the Cr(CN)₆^3? ion, and the crystal structure of K₃Cr(CN)₆ has been described both as monoclinic C_2h⁵ and as orthorhombic D_2h¹⁴. The solution and single crystal Raman spectra were recorded at room temperature. On the basis of these data a new assignment was made and the crystal structure was determined to be orthorhombic.     

Two novel cyanide-bridged bimetallic magnetic chains derived from manganese(III) Schiff bases and hexacyanochromate(III) building blocks

Two novel complexes, [{Mn(salen)}(2){Mn(salen)(CH(3)OH)}{Cr(CN)(6)}](n)·2nCH(3)CN·nCH(3)OH (1) and [Mn(5-Clsalmen)(CH(3)OH)(H(2)O)](2n)[{Mn(5-Clsalmen)(μ-CN)}Cr(CN)(5)](n)·5.5nH(2)O (2) (salen(2-) = N,N'-ethylene-bis(salicylideneiminato) dianion; 5-Clsalmen(2-) = N,N'-(1-methylethylene)-bis(5-chlorosalicylideneiminato) dianion), were synthesized and structurally characterized by X-ray single-crystal diffraction. The structural analyses show that complex 1 consists of one-dimensional (1D) alternating chains formed by the [{Cr(CN)(6)}{Mn(salen)}(4){Mn(salen)(CH(3)OH)}(2)](3+) heptanuclear cations and [Cr(CN)(6)](3-) anions. While in complex 2, the hexacyanochromate(III) anion acts as a bis-monodentate ligand through two trans-cyano groups to bridge two [Mn(5-Clsalmen)](+) cations to form a straight chain. The magnetic analysis indicates that complex 1 shows three-dimensional (3D) antiferromagnetic ordering with the Ne?el temperature of 5.0 K, and it is a metamagnet displaying antiferromagnetic to ferromagnetic transition at a critical field of about 2.6 kOe at 2 K. Complex 2 behaves as a molecular magnet with Tc = 3.0 K.     

Electrical and magnetic properties of thin films containing metal clusters

A large variety of granular polymer thin films can be synthetized in a capacitively coupled coplanar diode radiofrequency (r.f.) discharge system in which an argon-monomer mixture is injected at low pressure (20 mTorr). This approach offers several advantages over the other techniques, e.g. easy control of the metal content in the film from a few % up to 100%. The d.c. electrical properties of gold containing plasma polymerized tetrafluoroethylene (PPTFE) and the magnetic behavior of cobalt containing plasma polymerized propane (PPP) are reported in this paper.     

Hydrazinium metal(II) and metal(III) ethylenediamine tetraacetate hydrates

Hydrazinium metal ethylenediaminetetraacetate complexes of molecular formula (N₂H₅)₂[Mg(edta)·H₂O], (N₂H₅)₃[Mn(edta)··H₂O](NO₃)·H₂O, N₂H₅[Fe(edta)·H₂O], N₂H₅[Cu(Hedta)·H₂O] and N₂H₅[Cd(Hedta)·H₂O]·H₂O have been synthesized and characterized by elemental and chemical analysis, conductivity and magnetic measurements and spectroscopic techniques. The thermal behaviour of these complexes has been studied by thermogravimetry and differential thermal analysis. The data set provided by the simultaneous TG-DTA curves of the complexes shows the occurrence of three or four consecutive steps such as dehydration, ligand pyrolysis and formation of metal oxides. X-ray powder diffraction patterns of copper and cadmium complexes show that they are not isomorphous. These studies suggest seven coordination for Mg,Mn, Fe complexes and six coordination for Cu and Cd derivatives.     

Photoresponse of p-type zinc-doped iron(III) oxide thin films

Stable zinc-doped iron(III) oxide thin films that exhibit p-type behavior were synthesized by spray pyrolytic deposition (SPD) on conducting indium-doped tin oxide-coated glass substrate. The highest photocurrent density of 1.1 mA/cm2 was observed at an illumination intensity of 40 mW/cm2 at -0.8 V vs Pt for zinc-doped p-Fe2O3 samples prepared at an optimum substrate temperature of 663 K using an optimum spray time of 70 s. A quantum efficiency of 21.1% at 325 nm was found for SPD samples prepared using a dopant concentration of 0.0088 M zinc nitrate hexahydrate. X-ray diffraction results showed structures of alpha-Fe2O3 and ZnFe2O4. A direct band gap energy of 2.2 eV was found from monochromatic photocurrent density data and agrees closely with the band gap obtained from UV-vis absorption. The X-ray photoelectron spectroscopy results also confirm the presence of zinc dopant (4.0 atomic %) in thin films of zinc-doped p-Fe2O3.     

Pressure-tuning of magnetism and linkage isomerism in iron(II) hexacyanochromate

A pressure-induced linkage isomerization of the cyanide anion has been observed in single crystals of a chromium(III)-iron(II) Prussian blue analogue of formula K0.4Fe4[Cr(CN)6]2.8 square1.2.16H2O (1). Upon application of pressure in the 0-1200 MPa range, the cyanide ligand rotates and becomes C-bonded to the iron(II) cations, leading to a stabilization of their diamagnetic low-spin states. The result is a decrease of magnetization and magnetic ordering temperatures from TC = 19 K at ambient pressure to 13 K at 1200 MPa. The initial magnetic properties can be restored on pressure release. The reversible movement of cyanide in the solid state can be exploited as a switch of the magnetic interaction at the molecular level.     

Electrochemical decomposition of layer-by-layer thin films composed of TEMPO-modified poly(acrylic acid) and poly(ethyleneimine)

The decomposition of layer-by-layer (LbL) thin films composed of 2,2,6,6-tetramethylpiperidine-1-oxyl free radical-appended poly(acrylic acid) (TEMPO-PAA) and poly(ethylenimine) (PEI) was studied by using a quartz crystal microbalance (QCM) and cyclic voltammetry. The electrode potential of the (PEI/TEMPO-PAA)₄/PEI film-coated Au resonator was scanned from +0.2 to +0.8 V vs Ag/AgCl. The CV showed that the oxidation peak current decreased as the number of scans increased. The change in the resonance frequency of the QCM increased after electrolysis, indicating that the film was decomposed by electrolysis. The positive charges originating from the oxoammonium ions probably destabilized the (PEI/TEMPO-PAA)₄/PEI film. Furthermore, the release of 5,10,15,20-tetraphenyl-21H,23H-porphine tetrasulfonic acid (TPPS) from TPPS-loaded (PEI/TEMPO-PAA)₄/PEI-coated ITO electrodes was investigated. TPPS was released at electrode potentials greater than +0.6 V by the decomposition of the film. The results suggest that TEMPO-PAA/PEI LbL films are suitable for electrochemically controlled drug delivery systems.     

Kinetics of precipitation and growth of thin indium(III) sulfide films

Thin films of indium(III) sulfide have been prepared by chemical precipitation from aqueous solutions containing indium(III) nitrate, thioacetamide, tartaric acid, and hydroxylamine hydrochloride at 333–368 K. Kinetics of In₂S₃ precipitation and the films growth under conditions of spontaneous formation of the solid phase in the solution has been studied. Formal rate law of indium(III) sulfide formation accounting for the partial orders of In₂S₃ precipitation with respect to the system components and the process activation energy has been derived. The effects of the reaction mixture composition, temperature, and the synthesis duration of In2S3 films growth have been studied.     

Intervalence electron transfer spectra of several iron(III) and copper(II) pentacyanoferrate(II) complexes

The intervalence spectra of several iron(III) and copper(II) pentacyanoferrate(II) complexes have been studied in comparison to those of the hexacyanoferrate(II) analogs. The energies of the intervalence transitions have shown to be strongly dependent on the properties of the Fe(CN)₅Lⁿ⁻ anion. The observed trend on the energies of the intervalence bands in the sequence NH₃ < py < pyrazinecarboxylate < dimethyl sulfoxide ∼ tetramethylene sulfoxide < CO, for the ligand L, were interpreted in terms of backbonding stabilization of the low spin, iron(II) donor ion.     

Studies of Langmuir-Blodgett films of an ion pair metal complex containing Eu(III)-Ru(II) dual chromophores

A surfactant ion-pair complex, [Ru(bpy)(2)L][Eu(NTA)(4)](2) (in which L = 1-docosyl-2-(2- pyridyl)benzimidazole, bpy = 2,2'-bipyridine, and NTA = 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedionato) has been synthesized. The surface pressure-area isotherm measurements show that the complex forms a stable Langmuir film at the air-water interface without adding any electrolytes into the subphase. The monolayers formed at the surface pressures of 5 mN m(-1) and 20 mN m(-1), have been successfully transferred onto glass and quartz substrates with the transfer ratios close to unity. The Langmuir-Blodgett films were studied by UV-visible, infrared, and emission spectroscopies, atomic force microscopy, and cyclic voltammetry. The optical, redox, and morphology properties of the LB films were found to be significantly affected by the target surface pressures used for the film depositions.     

Photochromism of metal complexes composed of diarylethene ligands and Zn(II), Mn(II), and Cu(II) hexafluoroacetylacetonates

Metal complexes composed of bidentate 1,2-bis(2-methyl-5-(4-pyridyl)-3-thienyl)perfluorocyclopentene (1a) and monodentate 1-(2-methyl-5-phenyl-3-thienyl)-2-(2-methyl-5-(4-pyridyl)-3-thienyl)perfluorocyclopentene (2a) photochromic ligands and M(hfac)(2) (M = Zn(II), Mn(II), and Cu(II)) were prepared, and their photoinduced coordination structural changes were studied. X-ray crystallographic analyses showed the formation of coordination polymers and discrete 1:2 complexes for bidentate and monodentate ligands, respectively. The complexes underwent reversible photochromic reactions by alternate irradiation with UV and visible lights in solution as well as in the single-crystalline phase. Upon photoirradiation with UV and visible light, the ESR spectra of the copper complexes of 1a reversibly changed. While the open-ring isomer gave an axial-type spectrum, the photogenerated closed-ring isomer showed a rhombic-type spectrum. This indicates that the photoisomerization induced the change in the coordination structure.     

UV photoelectron spectra of some transition metal(II) acetylacetonates

The He(I) photoelectron spectra of acetylacetone (HAA) and its metallo complexes, M(II)(AA)₂ (M(II) = Mn, Co, Ni, Cu and Zn), have been measured. These spectra show characteristic metal-dependence, from which the assignment is made. The order of the orbital energy level, d > π₃ > n_? > n₊, holds for all the complexes reported here. The splitting of these orbitals is found to depend on the central metal ion specifically.     

Cyclic tetramers composed of rhodium(III), iridium(III), or ruthenium(II) half-sandwich and 6-purinethiones

Six new cyclic tetranuclear complexes [[M(Cp*)(L)](4)](4+) and [[Ru(II)(L)(cymene)](4)](4+) [Cp* = eta(5)-C(5)Me(5), cymene = eta(6)-p-MeC(6)H(4)Pr(i); M = Rh(III) and Ir(III); HL = 6-purinethione (H(2)put) and 2-amino-6-purinethione (H(2)aput)] were prepared in a self-assembly manner and characterized by NMR spectroscopy, electrospray ionization mass spectrometry, and X-ray crystal structure analysis. The two crystal structures of [[Rh(Cp*)(H(0.5)put)](4)](CF(3)SO(3))(2) and [[Ir(Cp*)(Haput)](4)](CF(3)SO(3))(4) revealed that they have similar S(4) structures with an alternate chirality array of CACA, and all ligands adopt a mu-1kappaN(9):2kappa(2)S(6),N(7) coordination mode. The orientations of the four bridging ligands are alternately up and down, and they form a central square cavity. Interestingly, the cationic tetramers of the former are stacked up along the c axis, resulting in an infinite channel-like cavity. The driving force of this stacking is due to intermolecular double hydrogen bonds [N(1)-H...N(21) = 2.752(4) A] at both sides of the cavity. In the two Rh(III)- and Ru(II)-H(2)aput systems, it turned out that the dimeric species are dominantly formed in the reaction solutions but finally convert into the tetrameric species.     

CoFe2-xMnxO4纳米晶薄膜的结构、磁性及磁光效应研究

为了改善磁光材料CoFe2O4的磁学特性,本研究利用改进的溶胶-凝胶法在单晶硅衬底上制备了不同掺杂量的CoFe2-xMnxO4(x=0～2,0)纳米晶薄膜系列样品。并对其结构、磁性及磁光效应进行了研究。结果表明,Mn^3+的掺入可以有效地控制和降低CoFe2O4的居里温度,并可显著地增强薄膜的磁光效应。     

Layer-by-layer assembled thin films composed of carboxyl-terminated poly(amidoamine) dendrimer as a pH-sensitive nano-device

Dendrimer-containing multilayer thin films have successfully been prepared by a layer-by-layer deposition of carboxyl-terminated poly(amidoamine) dendrimer (PAMAM–COOH) and poly(methacrylic acid) (PMA) on a solid surface at pH 4.0, while the multilayer film did not form at pH 7.0. The PMA/PAMAM–COOH multilayer films prepared at pH 4.0 are decomposed at neutral pH due to electrostatic repulsion between negatively-charged carboxylate residues. The results suggest that the primary force for the successful deposition of PAMAM–COOH and PMA at pH 4.0 is hydrogen bonding between COOH residues on the surface of the dendrimer and PMA. The multilayer films are decomposed also at strongly acidic pH, suggesting an electrostatic force of attraction between the protonated tertiary amino groups in PAMAM–COOH and a small fraction of COO⁻ residues in PMA contributes in part to the multilayer formation at pH 4.0. The PMA/PAMAM–COOH thin films can accommodate model dyes, Rose Bengal and 5,10,15,20-tetraphenyl-21H,23H-porphinetetrasulfonate, and the release can be controlled by changing pH.     

Sugar-sensitive thin films composed of concanavalin A and glycogen.

Sugar-sensitive thin films were prepared by a layer-by-layer deposition of concanavalin A (Con A) and glycogen on the surface of a quartz slide and their sugar-induced decomposition was studied. The Con A/glycogen multilayer films can be decomposed by exposing them to sugar solutions (D-glucose, D-mannose, methyl-alpha-D-glucose and methyl-alpha-D-mannose), as a result of displacement of sugar residues of glycogen from the binding sites of Con A by the free sugar added in the solution. The rate of decomposition significantly depended on the type of sugar and its concentration.     

13C nuclear magnetic resonance spectra of arylthallium(III) bis(trifluoroacetates)

¹³C chemical shifts and ¹³C? ²⁰⁵Tl spin–spin coupling constants are reported for phenylthallium(III) bis(trifluoroacetate) and some of its mono- and dimethyl derivatives. The signs of ⁿJ(¹³C, ²⁰⁵Tl) relative to ⁿ⁺¹J(¹H, ²⁰⁵Tl) are determined by offresonance decoupling of protons.     

Effects of central metal ions on vibrational circular dichroism spectra of tris-(beta-diketonato)metal(III) complexes

Vibrational circular dichroism (VCD) spectra of a series of [M(III)(acac)3] (acac = acetylacetonato; M = Cr, Co, Ru, Rh, Ir, and Al) and [M(III)(acac)2(dbm)] (dbm = dibenzoylmethanato; M = Cr, Co, and Ru) have been investigated experimentally and/or theoretically in order to see the effect of the central metal ion on the vibrational dynamics of ligands. The optical antipodes give the mirror-imaged spectra in the region of 1700-1000 cm(-1). The remarkable effect of the central metal ion is observed experimentally on the VCD peaks due to C-O stretches (1500-1300 cm(-1)) for both [M(III)(acac)3] and [M(III)(acac)2(dbm)]. In the case of Delta-[M(III)(acac)3], for example, the order of frequency of two C-O stretches (E and A2 symmetries) is dependent on the kind of a central metal ion as follows: E (-) > A2 (+) for M = Co, Rh, and Ir, while A2 (+) > E (-) for M = Cr and Ru. In the case of Delta-[M(III)(acac)2(dbm)], the order of frequency of three C-O stretches (A, B, and B symmetries) is as follows: A (-) > B (+) > B (+) for Co(III), B (+) > A (-) > B (-) for Cr(III), and A (-) > B (+) > B (-) for Ru(III). These results imply that the energy levels of C-O stretches are delicately affected by the kind of central metal ion. Since such detailed information is not obtained from the IR spectra alone, the VCD spectrum can probe the effect of the central metal ion on interligand cooperative vibration modes.