Study on the spin-crossover transition in [Fe(cis-/trans-stpy)4(X)2] (stpy: styrylpyridine, X: NCS, NCBH3) under high pressure toward ligand-driven light-induced spin change

Toward the realization of a ligand-driven light-induced spin change (LD-LISC) around room temperature, we have investigated the spin-crossover phenomenon in [Fe(stpy)₄(X)₂] (stpy = styrylpyridine, X = NCS, NCBH₃) under high pressure. The spin transition temperature increases from 110 to 220 K with increasing applied pressure up to 0.75 GPa for [Fe(trans-stpy)₄(NCS)₂], while [Fe(cis-stpy)₄(NCS)₂] shows the high-spin state in the temperature region between 2 and 300 K even at 0.75 GPa. In the case of X = NCBH₃, due to the stronger ligand field of NCBH₃, the spin transition temperature increases from 240 to 360 K with increasing applied pressure up to 0.50 GPa for [Fe(trans-stpy)₄(NCBH₃)₂]. In the case of [Fe(cis-stpy)₄(NCBH₃)₂], the spin state is the high-spin state in the temperature region between 2 and 300 K. However, the spin transition appears at 125 K under 0.5 GPa and the transition temperature increases with increasing applied pressure. In this way, we have decided the applied pressure region of 0.65-1.09 GPa where [Fe(stpy)₄(NCBH₃)₂] undergoes LD-LISC at room temperature.     

Me-AnilaPhos: a new chiral phosphine-phosphoramidite ligand for a highly efficient Rh-catalyzed asymmetric olefin hydrogenation

A cationic rhodium(I) complex with a novel chiral phosphine-phosphoramidite ligand based on 2-diphenylphosphino-N-methylaniline and R-BINOL moieties has been synthesized. The complex provided remarkably high activity and enantioselectivity in the asymmetric hydrogenation of methyl (Z)-α-acetamidocinnamate (100% conversion after 10 min, 98% ee) and dimethyl itaconate (100% conversion after 26 min, 96% ee) under ambient conditions (1 bar hydrogen pressure, room temperature) using 1 mol % of the catalyst in dichloromethane as solvent. On the other hand, when hydrogenation was performed in methanol, both conversion and enantioselectivity were significantly diminished, due to the partial decomposition of the rhodium/phosphine-phosphoramidite complex.     

Influence of size and shape effects on the high-pressure solubility of n-alkanes: Experimental data, correlation and prediction

(Solid + liquid) phase equilibria (SLE) of (n-hexadecane, or n-octadecane + 3-methylpentane, or 2,2-dimethylbutane, or benzene) at very high pressures up to about 1.0 GPa have been investigated at the temperature range from T = (293 to 353) K. The thermostated apparatus for the measurements of transition pressures from the liquid to the solid state in two component isothermal solutions was used. The pressure-temperature-composition relation of the high pressure (solid + liquid) phase equilibria, polynomial based on the general solubility equation at atmospheric pressure was satisfactorily used. Additionally, the SLE of binary systems (n-hexadecane, or n-octadecane + 3-methylpentane, or 2,2-dimethylbutane, or benzene, or n-hexane or cyclohexane) at normal pressure was discussed. The results at high pressures were compared for every system to these at normal pressure. The influence of the size and shape effects on the solubility at 0.1 MPa and high pressure up to 600 MPa was discussed.The main aim of this work was to predict the mixture behaviour using only pure components data and cubic equation of state in the wide range of pressures, far above the pressure range which cubic equations of state are normally applied to. The fluid phase behaviour is described by the corrected SRK-EOS and the van der Waals one fluid mixing rules.     

Synthesis,spectroscopic and electrochemical characterization of copper(I) complexes with functionalized pyrazino[2,3-f]-1,10-phenanthroline

The present work reports the synthesis and spectroscopic and electrochemical characterization of homoleptic copper(I) complexes with substituted pirazino [2,3-f]-1,10-phenanthroline, RpplR′, (R = H, Me, COOH or COOMe, and R′ = H, Me) as ligand. The ligand ppl works as an acceptor of electronic density, which is delocalized mainly in the quinoxaline part of its structure. The UV–Vis spectra show that all the complexes display bands in the range 400–650 nm, which are MLCT in character. The λ_max and extinction coefficients of the MLCT band at 450 nm and the LC band do not change significatively when varying the R substituent. Nevertheless, the intensity of the shoulder around 500 nm does change; this absorption has been related to either a static or dynamic flattening distortion of the complex D_2d → D₂ symmetry. The cyclic voltammetry of the complexes shows irreversible redox processes with E_p values that do not follow the tendency expected from the donor/acceptor character of the substituents on the ligand. All the complexes studied showed no emission both in acetonitrile and dichloromethane as solvent at room temperature and under argon atmosphere.     

Partial molar volumes of organic solutes in water. XII. Methanol(aq), ethanol(aq), 1-propanol(aq), and 2-propanol(aq) at T = (298 to 573) K and at pressures up to 30 MPa

Density data for dilute aqueous solutions of methanol, ethanol, 1-propanol, and 2-propanol are presented together with partial molar volumes at infinite dilution calculated from the experimental data. The measurements were performed at from T = (298.15 up to 573.15) K and at pressure close to the saturated vapor pressure of water, at p = 30 MPa and at pressure between these limits. The data were obtained using a high-temperature high-pressure flow vibrating-tube densimeter.     

Synthesis and characterisation of two novel Rh(I) carbene complexes: Crystal structure of [Rh(acac)(CO)(L1)]

The [Rh(acac)(CO)(L)] (acac = acetylacetonato; L₁ = 1,3-bis-(2,6-diisopropylphenyl)imidazolinylidene and L₂ = 1,3-bis-(2,4,6-trimethylphenyl)imidazolinylidene) complexes were prepared by the action of the parent carbene on [Rh(acac)(CO)₂] in THF. The crystal structure characterisation of [Rh(acac)(CO)(L₁)] revealed a slightly distorted square planar geometry with the carbene ligand orientated almost perpendicular to the equatorial plane; an elongated trans Rh-O bond of 2.0806(18) Å reflecting the considerable trans-influence of the carbene ligand. By measuring the CO stretching frequencies in a range of [Rh(acac)(CO)(L)] complexes (L = CO, L₁, L₂, PPh₃, PⁿBu₃, P(O-2,4-^tBu₂-Ph)₃) the following electron donating ability series was established: L₁ ∼ L₂ ∼ PⁿBu₃ > PPh₃ > P(O-2,4-^tBu₂-Ph)₃ > CO; indicating the carbenes investigated in this study to have a similar electronic cis-influence as trialkyl phosphines. Both complexes do not display hydroformylation activity towards 1-hexene in the absence of added phosphine or phosphite ligands under the conditions investigated (P = 60; T = 85 °C). In the presence of a phosphine or phosphite ligand the resulting hydroformylation catalysis was identical to that observed for [Rh(acac)(CO)₂] and the corresponding ligand and subsequent high-pressure ³¹P NMR studies confirmed substitution of the carbene ligand under these conditions.     

Development of an epoxy-based monolith used for the affinity capturing of Eschericha coli bacteria

An epoxy-based monolith has been developed for use as hydrophilic support in bioseparation. This monolith is produced by self-polymerization of polyglycerol-3-glycidyl ether in organic solvents as porogens at room temperature within 1 h. One receives a highly cross-linked structure that provides useful mechanical properties. The porosity and pore diameter can be controlled by varying the composition of the porogen. In this work, an epoxy-based monolith with a high porosity (79%) and large pore size (22 μm) is prepared and used in affinity capturing of bacterial cells. These features allow the passage of bacterial cells through the column. As affinity ligand polymyxin B is used, which allows the binding of gram-negative bacteria. The efficiency of the monolithic affinity column is studied with Escherichia coli spiked in water. Bacterial cells are concentrated on the column at pH 4 and eluted with a recovery of 97 ± 3% in 200 μL by changing the pH value without impairing viability of bacteria. The dynamic capacity for the monolithic column is nearly independent of the flow rate (4 × 10⁹ cells/column). Thereby, it is possible to separate and enrich gram-negative bacterial cells, such as E. coli, with high flow rates (10 mL/min) and low back pressure (<1 bar) in a volume as low as 200 μL compatible for real-time polymerase chain reaction, microarray formats, and biosensors.     

Phase equilibrium measurements for systems containing propanenitrile with tert-butyl ethyl ether and C4-hydrocarbons

A static total pressure apparatus was used to measure isothermal VLE for systems containing propanenitrile +n-butane (322.02 K), +1-butene (312.55 K), +2-methylpropane (307.85 K) and +2-methylpropene (312.59 K). Vapour liquid equilibrium (VLE) for propanenitrile + tert-butyl ethyl ether (ETBE) was measured both with the static total pressure apparatus at 312.85 K and 358.32 K and with a glass circulation still apparatus at 102.6 kPa and 65.2 kPa. The system of propanenitrile + ETBE evidenced azeotropic behaviour.     

Study on the pressure induced charge transfer phase transition in (C5H11)4N(FeFe(C2O2S2)3) by means of μSR spectroscopy

We have investigated the magnetic properties of iron mixed-valence complexes, (n-C_nH_2n+1)₄N[Fe^IIFe^III(dto)₃] (dto = C₂O₂S₂, n = 3, 5), in which not only a ferromagnetic transition but also a novel charge transfer phase transition (CTPT) take place [1]. This CTPT can be observed under ambient pressure for n = 3, while it appears abruptly above 0.5 GPa for n = 5 [2]. Recently, we have measured the muon spin relaxation (μSR) for the CTPT of n = 3, which revealed the dynamical process of electron-transfer between Fe^II and Fe^III and its frequency was estimated at about 0.1 MHz [3]. To investigate the pressure induced CTPT for n = 5, we carried out the μSR measurement for n = 5 at 150 K between 0.30 and 0.64 GPa with the ⁴He gas-operated pressure system. The asymmetry of the muon spin relaxation for n = 5 with Cu-Be pressure cell was almost constant up to 0.55 GPa, while it rapidly decreased with increasing pressure above 0.60 GPa. This result shows that the applied pressure causes the spin fluctuation due to the CTPT, which induces the decrease of the asymmetry of muon spin relaxation. This experiment can correctly decide the phase transition pressure from the absence to the appearance of the CTPT for n = 5.     

Photoactive ruthenium nitrosyls derived from quinoline- and pyridine-based ligands: Accelerated photorelease of NO due to quinoline ligation

The ruthenium nitrosyl [(PaPy₂Q)Ru(NO)](BF₄)₂, derived from the quinoline-based ligand PaPy₂QH (PaPy₂QH = N,N-bis(2-pyridylmethyl)amine-N-ethyl-2-quinaldine-2-carboxamide; H = dissociable proton) has been synthesized and characterized by X-ray crystallography and spectroscopic techniques. This {Ru–NO}⁶ nitrosyl is soluble in aqueous media and stable under physiological conditions at pH 7. [(PaPy₂Q)Ru(NO)]²⁺ releases NO rapidly upon exposure to low-intensity UV light (5 mW/cm²). The NO donor capacity of this nitrosyl (quantum yield = 0.20, λ_irr = 365 nm) is considerably higher than that of analogous nitrosyl derived from a polypyridyl ligand without the quinoline moiety.     

Excess molar enthalpies of methylformate + (1-propanol, 2-propanol, 1-butanol, 2-butanol and 1-pentanol) at T = 298.15 K, p = (5.0, 10.0) MPa, and methylformate + 1-propanol at T = 333.15 K, p = 10.0 MPa

A high pressure flow-mixing isothermal calorimeter is used to determine the excess molar enthalpies of methylformate + (1-propanol, 2-propanol, 1-butanol, 2-butanol and 1-pentanol) at T = 298.15 K and p = (5.0, 10.0) MPa, and methylformate + 1-propanol at T = 333.15 K and p = 10.0 MPa. The Redlich-Kister equation is fit to the experimental results.     

Synthesis and screening of bifunctional radiolabelled carborane-carbohydrate derivatives

A new bifunctional carborane ligand was prepared as a platform for the development of targeted molecular radioimaging and therapy agents. The carborane derivative was synthesized bearing a glucose substituent to increase the water solubility of the ligand and a benzoic acid group as a site for linking to amine containing targeting vectors. A convenient method to conjugate the ligand and the non-glycosylated analogue to amino groups was developed using simple active esters which were combined with a model amine generating two new N,N-diethyl(aminoethyl) benzamide derivatives. These were labelled with ¹²⁵I in good yield and the log P values measured for [¹²⁵I]-15 (log P = 0.82 ± 0.04) and [¹²⁵I]-16 (log P = 1.53 ± 0.01). The benzamides were also evaluated for their capacity to bind to B16F10 melanoma cells where the hydrophilic compound showed low binding while [¹²⁵I]-16 showed modest uptake (30.7 ± 2.2%) after 24 h.     

Ruthenium vinylidene and carbyne complexes containing a multifunctional tridentate ligand with a PNN donor set

The neutral, octahedral ruthenium vinylidene complexes mer,trans-[(PNN)Cl₂Ru(CCHR)] (PNN = N-(2-diphenylphosphinobenzylidene)-2-(2-pyridyl)ethylamine; R = Ph, 1a; R = ^tBu, 1b) are reported. An X-ray crystallographic study of 1a confirms the tridentate, meridional coordination mode of the PNN ligand. Compounds 1a and 1b undergo regioselective electrophilic addition with HBF₄ · Et₂O at C_β of the vinylidene ligand at low temperatures, and are cleanly and quantitatively converted to the ruthenium carbynes mer,trans-[(PNN)Cl₂Ru(CCH₂R)][BF₄] (R = Ph, 2a; R = ^tBu, 2b). Carbynes 2a and 2b are stable only at low temperatures (<−50 °C). Complex 1a undergoes ligand substitution with L to yield mer,trans-[(PNN)Cl₂Ru(L)] (L = MeCN, 3a; L = CO, 3b).     

A method for rapid screening of interactions of pharmacologically active compounds with albumin

We determine the association constants for ligand–protein complex formation using the flow injection method. We carry out the measurements at high flow rates (F = 1 mL min⁻¹) of a carrier phase. Therefore, determination of the association constant takes only a few minutes. Injection of 1 nM of the ligand (10 μL of 1 μM concentration of the ligand solution) is sufficient for a single measurement. This method is tested and verified for a number of complexes of selected drugs (cefaclor, etodolac, sulindac) with albumin (BSA). We obtain K = 4.45 × 10³ M⁻¹ for cefaclor, K = 1.00 × 10⁵ M⁻¹ for etodolac and K = 1.03 × 10⁵ M⁻¹ for sulindac in agreement with the literature data. We also determine the association constants of 20 newly synthesized 3β- and 3α-aminotropane derivatives with potential antipsychotic activity – ligands of 5-HT_1A, 5-HT_2A and D₂ receptors with the albumin. Results of the studies reported here indicate that potential antipsychotic drugs bind weakly to the transporter protein (BSA) with K ≈ 10²–10³ M⁻¹. Our method allows measuring K in a wide range of values (10²–10⁹ M⁻¹). This range depends only on the solubility of the ligand and sensitivity of the detector.     

Pressure dependence of Curie temperature in a selenazyl radical ferromagnet

The hydrostatic pressure response of T_C of the bisdiselenazolyl radical ferromagnet 1 up to 5 GPa was investigated by AC magnetic susceptibility measurements using a SQUID magnetometer and a miniature diamond anvil cell. It was found that the ambient pressure value of T_C = 17 K could be raised to 21 K at a pressure of 0.9 GPa. The experimental technique is described in detail and the pressure response is compared to that observed in related systems.     

Clathrate hydrate formation in (methane + water + methylcyclohexanone) systems: the first phase equilibrium data

The present study experimentally demonstrated clathrate hydrate formation in the systems of (methane + water + each of the three methylcyclohexanone isomers, i.e., 2-methylcyclohexanone, 3-methylcyclohexanone, and 4-methylcyclohexanone) and measured the first data of the quadruple (water rich liquid + hydrate + methylcyclohexanone rich liquid + methane rich vapor) equilibrium pressure and temperature conditions in these systems over the temperatures from T=273 K to T=281 K. In the three systems with methylcyclohexanone, the measured equilibrium pressure at each given temperature is ∼1.3 MPa lower than that in a structure-I hydrate forming (methane + water) system without any methylcyclohexanone, which suggests the formation of structure-H hydrates with methylcyclohexanones as large-molecule guest substances. Among the three systems, 3-methylcyclohexanone provides the highest equilibrium pressure, and 2-methylcyclohexanone, the lowest.     

N, O-ligand accelerated zinc-catalyzed transesterification of alcohols with vinyl esters

N-Phenyldiethanolamine (1f) is an efficient ligand for zinc-catalyzed transesterification of alcohols with vinyl acetate (R³ = Me) at room temperature. In the case of using other vinyl esters (R³ = Et, n-Pr, Ph), the corresponding products were easily obtained in the presence of pyridine-type ligand 2 instead of aminoalcohol 1f.     

Activation of the Si-H bond of Et2SiH2 in photochemical reaction with W(CO)6: Spectroscopic characterization of intermediate W-Si compounds and the revisited crystal structure of the bis{(μ-η-hydridodiethylsilyl)tetracarbonyltungsten(I)} complex [{W(μ-η-H-SiEt2)(CO)4}2]

The photochemical reaction of W(CO)₆ with diethylsilane has been used to generate new tungsten-silicon compounds varying in stability. The initially formed η²-silane intermediate complex [W(CO)₅(η²-H-SiHEt₂)], characterized by two equal-intensity doublets with ²J_H-H = 10 Hz at δ = 5.10 (¹J_Si-H = 217 Hz) and δ = −8.05 (¹J_W-H = 38 Hz, ¹J_Si-H = 93 Hz), was detected by the ¹H NMR spectroscopy (methylcyclohexane-d₁₄, −10 °C). The η²-silane complex was converted in the dark to give more stable species. One of them was characterized by two equal-intensity proton signals observed as doublets with ²J_H-H = 5.2 Hz at δ = −8.25 and −10.39 ppm. The singlet proton resonance at δ = −9.31 flanked by ²⁹Si and ¹⁸³W satellites (¹J_Si-H = 43 Hz, ²J_Si-H = 34 Hz, ¹J_W-H = 40 Hz) was assigned to the agostic proton of the W(η²-H-SiEt₂) group in the most stable compound isolated from the photochemical reaction products in crystalline form. The molecular structure of the bis{(μ-η²-hydridodiethylsilyl)tetracarbonyltungsten(I)} complex [{W(μ-η²-H-SiEt₂)(CO)₄}₂] was established by single-crystal X-ray diffraction studies. The tungsten hydride observed in the ¹H NMR spectrum at δ = −9.31 was located in the structure at a chemically reasonable position between the W and Si atoms of the W-Si bond of the bridging silyl ligand. The reactivity of photochemically generated W-Si compounds towards norbornene, cyclopentene, diphenylacetylene, acetone, and water was studied. As was observed by IR and NMR spectroscopy, the η²-silane ligand in the complex [W(CO)₅(η²-H-SiHEt₂)] is very easily replaced by an η²-olefin or η²-alkyne ligand.     

Synthesis, crystal structure and bioactivity of a novel 18-metallacrown-6 [Mn6(H2O)6 (anshz)6] · 10DMF

A novel macrocyclic hexanuclear manganese(III) 18-metallacrown-6 compound, [Mn₆(H₂O)₆ (anshz)₆] · 10DMF, has been prepared using a trianionic pentadentate ligand N-acetyl-5-nitrosalicylhydrazide (anshz³⁻) and characterized by X-ray diffraction (DMF = N,N-dimethylformamide). The crystal structure contains a neutral 18-membered metallacrown ring consisting of six Mn(III) and six anshz³⁻ ligands. The 18-membered metallacrown ring is formed by the succession of six structural moieties of the type [Mn(III)NN]. Due to the meridional coordination of the ligand to the Mn³⁺ ion, the ligand enforces the stereochemistry of the Mn³⁺ ions as a propeller configuration with alternating Δ/Λ forms. The disc-shaped hexanuclear ring shows at its largest diameter about 7.14 Å at entrance, about 9.76 Å at the center of the cavity, respectively. Antibacterial screening data showed that the manganese metallacrown has strong antimicrobial activity against Bacillus subtilis.