Impaired erythrocyte transmembrane potential in diabetes mellitus and its possible improvement by resorcylidene aminoguanidine

Erythrocytes of diabetic patients have abnormal membrane properties. We examined in vitro transmembrane potential and the possible effect of resorcylidene aminoguanidine (RAG) on its modulation in erythrocytes of diabetic subjects. The transmembrane potential was assessed in RAG-treated and untreated erythrocytes, respectively, using a fluorescent dye (3,3'-dipropylthiadicarbocyanine iodide [DiSC3(5)]). We confirmed earlier findings that the transmembrane potential of diabetic erythrocytes is significantly increased compared with control (P < 0.01). The membrane hyperpolarization found in diabetic cells seems to be a result of oxidative stress present in diabetes mellitus. On one hand, the RAG treatment induced decrease in abnormal transmembrane potential values in diabetic erythrocytes (P < 0.01), presumably via its antioxidant and antiglycation activity. On the other hand, RAG moderately hyperpolarized the control erythrocytes (P < 0.05). We suggest that the drug-induced transient membrane expansion leads to an intracellular potassium loss and a subsequent change of the transmembrane potential. However, if controlled by an appropriate dosage, RAG can eliminate certain types of erythrocyte membrane damage induced by diabetes mellitus.     

Synthesis of thieno[2,3-c:5,4-c]dipyridine and the one electron transfer properties of its dimethyl diquaternary salt

Thieno[2,3-c:5,4-c]dipyridine is synthesised by reaction of 3,3′-thiobispyridine with sodium and liquid ammonia in dimethylformamide. It forms a diquaternary salt with excess methyl iodide. The salt is reversibly reduced to a stable blue-green radical cation in aqueous solution at a potential (E_σ) of -0.38V.     

New saccharinate complexes with 3,3′-azobispyridine ligand: synthesis,characterization, and spectroscopic properties

The new metal complexes with saccharinate (sac) and 3,3′-azobispyridine (3,3′-abpy), [Ni(H₂O)₄(3,3′-abpy)₂](sac)₂ (1), [Cu(sac)₂(H₂O)(μ-3,3′-abpy)]_n (2), [Zn(H₂O)₄(3,3′-abpy)₂](sac)₂ (3), [Cd(sac)₂(H₂O)₂(μ-3,3′-abpy)]_n (4), and [Hg₂(μ-sac)₂(sac)₂(μ-3,3′-abpy)(3,3′-abpy)₂]_n (5), were synthesized and characterized by IR spectra, elemental analysis, and single-crystal X-ray diffraction. Spectroscopic (UV–vis and photoluminescence) and thermal properties were also investigated. Single-crystal X-ray analysis reveals that Ni(II) and Zn(II) are coordinated by four aqua ligands and two nitrogens of 3,3′-abpy, while sac is a counter-ion in 1 and 3. In 2, Cu(II) and all ligands are linked by coordination bonds and 3,3′-abpy ligands connect the Cu(II) centers forming a 1-D coordination polymer. In 4, sac N-coordinated to Cd(II) and distorted octahedral geometry of Cd(II) ion is completed by two aqua and bridging 3,3′-abpy ligands. In 5, sac bridges two Hg(II) ions to generate dinuclear [Hg₂(μ-sac)₂] units. These dinuclear units are connected by 3,3′-abpy to form a 1-D coordination polymer. The photoluminescence spectra of 3 and 5 show blue fluorescent emission bands, and these emissions can probably be assigned to intraligand fluorescent emissions. Thermal decompositions of the compounds are also discussed. For all complexes, magnetic susceptibility measurements show expected magnetic behavior.     

3,3′-Oxybispyridine and the polarographic reduction of 1,1′-dimethyl-3,3′-oxybispyridinediium diiodide

3,3′-Oxybispyridine is prepared by reaction of 3-hydroxypyridine with 3-bromopyridine and converted to the 1,1′-dimethyl diquaternary salt with methyl iodide. The salt is reduced polarographically by a one electron transfer not involving hydrogen to an unstable radical cation at a potential (E_o) of ?0.81 V in the pH range 6.3-12.0.     

Synthesis and Properties of Brominated 6,6'-Dimethyl-[2,2'-bi-1H-indene]-3,3'-diethyl-3,3'-dihydroxy-1,1 '-diones

Photochromic 6‐bromomethyl‐6′‐methyl‐[2,2′‐bi‐1H‐indene]‐3,3′‐diethyl‐3,3′‐dihydroxy‐1,1′‐dione ( 2 ), 6,6′‐ bis(bromomethyl)‐[2,2′‐bi‐1H‐indene]‐3,3′‐diethyl‐3,3′‐dihydroxy‐1,1′‐dione ( 3 ) and 6,6′‐bis(dibromomethyl)‐[2,2′‐ bi‐1H‐indene]‐3,3′‐diethyl‐3,3′‐dihydroxy‐1,1′‐dione ( 4 ) have been synthesized from 6,6′‐dimethyl‐[2,2′‐bi‐1H‐ indene]‐3,3′‐diethyl‐3,3′‐dihydroxy‐1,1′‐dione ( 1 ). The single crystal of 4 was obtained and its crystal structure was analyzed. The results indicate that in crystal 4 , molecular arrangement is defective tightness compared with its precursor 1 . Besides, UV‐Vis absorption spectra in CH₂Cl₂ solution, photochromic and photomagnetic properties in solid state of 2 , 3 and 4 were also investigated. The results demonstrate that when the hydrogen atoms in the methyl group on the benzene rings of biindenylidenedione were substituted by bromines, its properties could be affected considerably.     

Preparation and molecular structures of N,N-2,2′-dipicolyl- and N,N-3,3′-dipicolyldithiocarbamato metal complexes

New iron(III) and cobalt(III) complexes, [Fe(2,2′-dpdtc)₃], [Fe(3,3′-dpdtc)₃], [Co(2,2′-dpdtc)₃], and [Co(3,3′-dpdtc)₃] (dpdtc?=?dipicolyldithiocarbamate) have been synthesized and their molecular structures and spectroscopic properties determined. The 2,2′- and 3,3′-dpdtc ligands have four donors, S, S′, N, and N′. These complexes are insoluble in water, but soluble in acidic solution. Crystal structures of these metal complexes reveal that the central metal ions have MS₆ (M?=?Fe and Co) octahedral structures and all dipicolyl groups do not coordinate.     

Two‐Dimensional Monovalent Copper Halide Coordination Polymers Incorporating Anti‐Conformation 3,3′‐Bipyridine

Hydrothermal treatment of aqueous mixtures of copper(II) halides and 3,3′‐bipyridine (3,3′‐bpy) has afforded the coordination polymers [CuCl(3,3′‐bpy)]_n ( 1 ) and [Cu₂Br₂(3,3′‐bpy)]_n ( 2 ), which were analyzed via single crystal X‐ray diffraction, infrared spectroscopy, and elemental analysis. The structure of 1 consists of two‐dimensional (2‐D) layers constructed from the linkage of castellated one‐dimensional (1‐D) [CuCl]_n stepped chains through anti‐conformation 3,3′‐bpy tethers. Compound 2 presents a related 2‐D sheet motif, albeit built from infinite 1‐D [Cu₂Br₂]_n ladders strutted by 3,3′‐bpy ligands in anti conformation. In both cases neighboring 2‐D sheets stack into 3‐D via weak C–H···halogen interactions.     

Phenylmethoxybis(tetrazolium) ion-association complexes with an anionic indium(III) — 4-(2-pyridylazo)resorcinol chelate

Complex formation and liquid-liquid extraction were studied in systems containing indium(III), 4-(2-pyridylazo)resorcinol (PAR), phenylmethoxybis(tetrazolium) salt (MBT), water and chloroform. The following MBTs, which differ only by the number of -NO₂ groups in their cationic parts, were used: 3,3′-(3,3′-dimetoxy-4,4′-biphenylene)bis(2,5-diphenyl-2H-tetrazolium chloride) (Blue Tetrazolium chloride, BT), 3,3′-(3,3′-dimetoxy-4,4′-biphenylene)bis[2-(4-nitrophenyl)-5-phenyl-2H-tetrazolium chloride] (Nitro Blue Tetrazolium chloride, NBT) and 3,3′-(3,3′-dimetoxy-4,4′-biphenylene)bis[2,5-di(4-nitrophenyl)-2H-tetrazolium chloride] (Tetranitro Blue Tetrazolium chloride, TNBT). The composition of the formed ternary complexes was determined, In:PAR:MBT=1:2:2, and the optimum conditions for their extraction found: pH, shaking time, concentration of the reagents and the sequence of their addition. Some key constants were estimated: constants of extraction (K_ex), constants of association (β) and constants of distribution (K_D). BT appears to be the best MBT for extraction of the In(III)-PAR species, [In³⁺(OH)₃(PAR)₂]^4?, (Log K_ex=10.9, Log β=9.8, Log K_D=1.12, R%=92.7%). Several additional characteristics concerning its application as extraction-spectrophotometric reagent were calculated: limit of detection (LOD = 0.12 μg cm^?3), limit of quantification (LOD = 0.40 μg cm^?3) and Sandell’s sensitivity (SS =1.58 ng cm^?2); Beer’s law is obeyed for In(III) concentrations up to 3.2 μg mL^?1 with a molar absorptivity coefficient of 7.3×10⁴ L mol^?1 cm^?1 at λ_max=515 nm.      

Kinetic study of the oxidative addition of methyl iodide to Vaska’s complex in ionic liquids

Oxidative addition of methyl iodide to Vaska’s complex in the ionic liquids 1-butyl-3-methylimidazolium triflate [C₄mim][OTf], [C₄mim] bis(trifluormethylsulfonyl)imide [Tf₂N], and N-hexylpyridinium [C₆pyr][Tf₂N] occurred cleanly to give the expected Ir(III) oxidative addition product. Pseudo-first order rate constants were determined for the oxidative addition reaction in each solvent ([Vaska’s] = 0.25 mM, [CH₃I] = 37.5 mM). The observed rate constants under these conditions were 5-10 times slower than the rate seen in DMF. At high methyl iodide concentrations (>23 mM), the expected first order dependence on methyl iodide was not observed. In each ionic liquid, there was no change in the reaction rates within experimental error over the methyl iodide concentration range of 23-75 mM. At lower methyl iodide concentration, a decrease in rate was observed in [C₄mim][Tf₂N] with decreasing concentration of methyl iodide.     

Regio‐ and stereospecific assembly of dispiro[indoline‐3,3′‐pyrrolizine‐1′,5′′‐thiazolidines] from simple precursors using a one‐pot procedure: synthesis,spectroscopic and structural characterization,and a proposed mechanism of formation

The synthesis and characterization of three new dispiro[indoline‐3,3′‐pyrrolizine‐1′,5′′‐thiazolidine] compounds are reported, together with the crystal structures of two of them. (3RS,1′SR,2′SR,7a′SR)‐2′‐(4‐Chlorophenyl)‐1‐hexyl‐2′′‐sulfanylidene‐5′,6′,7′,7a′‐tetrahydro‐2′H‐dispiro[indoline‐3,3′‐pyrrolizine‐1′,5′′‐thiazolidine]‐2,4′′‐dione, C₂₈H₃₀ClN₃O₂S₂, (I), (3RS,1′SR,2′SR,7a′SR)‐2′‐(4‐chlorophenyl)‐1‐benzyl‐5‐methyl‐2′′‐sulfanylidene‐5′,6′,7′,7a′‐tetrahydro‐2′H‐dispiro[indoline‐3,3′‐pyrrolizine‐1′,5′′‐thiazolidine]‐2,4′′‐dione, C₃₀H₂₆ClN₃O₂S₂, (II), and (3RS,1′SR,2′SR,7a′SR)‐2′‐(4‐chlorophenyl)‐5‐fluoro‐2′′‐sulfanylidene‐5′,6′,7′,7a′‐tetrahydro‐2′H‐dispiro[indoline‐3,3′‐pyrrolizine‐1′,5′′‐thiazolidine]‐2,4′′‐dione, C₂₂H₁₇ClFN₃O₂S₂, (III), were each isolated as a single regioisomer using a one‐pot reaction involving l ‐proline, a substituted isatin and (Z)‐5‐(4‐chlorobenzylidene)‐2‐sulfanylidenethiazolidin‐4‐one [5‐(4‐chlorobenzylidene)rhodanine]. The compositions of (I)–(III) were established by elemental analysis, complemented by high‐resolution mass spectrometry in the case of (I); their constitutions, including the definition of the regiochemistry, were established using NMR spectroscopy, and the relative configurations at the four stereogenic centres were established using single‐crystal X‐ray structure analysis. A possible reaction mechanism for the formation of (I)–(III) is proposed, based on the detailed stereochemistry. The molecules of (I) are linked into simple chains by a single N—H…N hydrogen bond, those of (II) are linked into a chain of rings by a combination of N—H…O and C—H…S=C hydrogen bonds, and those of (III) are linked into sheets by a combination of N—H…N and N—H…S=C hydrogen bonds.     

Bipyridyl Derivatives as Photomemory Devices: A Comparative Electronic‐Structure Study

The two isoelectronic bipyridyl derivatives [2,2′‐bipyridyl]‐3,3′‐diamine (BP(NH₂)₂) and [2,2′‐bipyridyl]‐3,3′‐diol (BP(OH)₂) are experimentally known to undergo very different excited‐state double proton transfer processes that result in fluorescence quantum yields that differ by four orders of magnitude. Such differences have been theoretically explained in terms of topographical features in the potential energy surface and the likely presence of conical intersections. The hypothetical hybrid compound [2,2′‐bipyridyl]‐3‐amin‐3′‐ol (BP(OH)(NH₂)) presents intermediate photochemical features of its “ancestors”. In this report we analyze the photochemical properties of a whole family of “dark” (not fluorescent) states that can be accessed from each bipyridyl derivative upon irradiation of light of a given wavelength and their potential application as photomemory devices. In the light of our density functional theory (DFT), time‐dependent DFT (TDDFT), and complete active space self‐consistent field (CASSCF) calculations, BP(NH₂)₂ is the more likely candidate to become a photomemory device.     

Kinetics and mechanism of indigo carmine-acidic iodate reaction. An indicator reaction for catalytic determination of Ru(III) ion

A kinetic study of uncatalyzed and Ru(III) catalyzed oxidation of indigo carmine(IC) (disodium 3,3′-dioxobi-indolin-2,2′-ylidene-5,5′-disulphonate) by iodate ion in aqueous sulphuric acid solution is reported. The uncatalyzed reaction order was found to be four; one each with respect to IC and iodate ion and second order with H⁺ ion. The Ru(III) catalyzed reaction was of fifth order, second order with respect to H⁺ and first order with respect to reductant, oxidant, and catalyst. Stoichiometric ratios of both reactions were the same with a 3:2 reductant-oxidant ratio. In both uncatalyzed and catalyzed reactions isatin-5-monosulphonic acid (2,3-dioxoindoline-5-sulphonic acid) was observed as the oxidation product. Rate constants for both the reactions are reported. Reaction mechanisms consistent with the experimental data are suggested. Further, a fixed time method is described for the determination of Ru(III), based on its ability to catalyze the oxidation of IC by acidic iodate. Using [H⁺] 2.25M, [iodate] 1.00 × 10^?3M and [IC] 5.0 × 10^?5M, in presence of Ru(III), the reaction followed first order kinetics with respect to IC. The interference of various cations, neutral salts, and potassium iodide on the determination of Ru(III) was studied using synthetic mixtures. The selectivity of the method and the recommended procedure are described.     

An Imidazoline–Aminophenol (IAP) Nickel Catalyst: Structure and Catalytic Activity in the Enantioselective 1,4‐Addition of 3′‐Indolyl‐3‐Oxindoles to Nitroethylene

The structure of a nickel complex of imidazoline–aminophenol (IAP) prepared from IAP with Ni(OAc)₂ was elucidated as cis‐bis(imidazolineaminophenoxide) [Ni(IAP)₂]. The [Ni(IAP)₂] complex smoothly promoted catalytic asymmetric 1,4‐addition of 3′‐indolyl‐3‐oxindole to nitroethylene to provide chiral mixed 3,3′‐bisindoles with high enantioselectivities. Mechanistic studies using ESI‐MS analyses suggest that one IAP ligand dissociated from [Ni(IAP)₂] to generate the Ni–enolate of 3′‐indolyl‐3‐oxindole. From the optically active 3,3′‐mixed indole adduct, biologically important 3′‐indolyl‐3‐pyrrolidinoindoline was successfully synthesized in a three‐step reaction sequence.     

Spectrophotometric Study on Kinetics of Solvatochromism of Methyl Violet in Aqueous Methanol

The kinetics of the reaction of methyl violet with iodide in aqueous methanol system was studied by spectrophotometric method. The rate of reaction of methyl violet in different alcoholic composition in presence of potassium iodide was observed at pH 4 and 6 at various temperatures (298–318 K). Solvatochromic effect was studied in different percentages of methanol (0–50%). Bathochromic shift was observed with the decrease in polarity of solvent. The color change was attributed to molecule's structure, the delocalization of unit electrical charge causes deepening of color and decrease of delocalization causes fading of color due to reduction of dye. Increase in the rate of reaction was observed with increase in alcoholic content and also affected by potassium iodide salt and increased with increase in concentration of potassium iodide. Energy of activation (E_a) and transition energy (E_T) were calculated with the help of kinetic data. Thermodynamic parameters such as enthalpy change of activation (ΔH*), Gibbs free energy change of activation (ΔG*) and entropy change of activation (ΔS*) were evaluated as a function of concentration of solvent and salt.     

Synthesis of spiro[indoline‐3,3′‐pyrrolizines] by 1,3‐dipolar reactions between isatins,l‐proline and electron‐deficient alkenes

Two spiro[indoline‐3,3′‐pyrrolizine] derivatives have been synthesized in good yield with high regio‐ and stereospecificity using one‐pot reactions between readily available starting materials, namely l ‐proline, substituted 1H‐indole‐2,3‐diones and electron‐deficient alkenes. The products have been fully characterized by elemental analysis, IR and NMR spectroscopy, mass spectrometry and crystal structure analysis. In (1′RS ,2′RS ,3SR ,7a′SR )‐2′‐benzoyl‐1‐hexyl‐2‐oxo‐1′,2′,5′,6′,7′,7a′‐hexahydrospiro[indoline‐3,3′‐pyrrolizine]‐1′‐carboxylic acid, C₂₈H₃₂N₂O₄, (I), the unsubstituted pyrrole ring and the reduced spiro‐fused pyrrole ring adopt half‐chair and envelope conformations, respectively, while in (1′RS ,2′RS ,3SR ,7a′SR )‐1′,2′‐bis(4‐chlorobenzoyl)‐5,7‐dichloro‐2‐oxo‐1′,2′,5′,6′,7′,7a′‐hexahydrospiro[indoline‐3,3′‐pyrrolizine], which crystallizes as a partial dichloromethane solvate, C₂₈H₂₀Cl₄N₂O₃·0.981CH₂Cl₂, (II), where the solvent component is disordered over three sets of atomic sites, these two rings adopt envelope and half‐chair conformations, respectively. Molecules of (I) are linked by an O—H…·O hydrogen bond to form cyclic R ₆⁶(48) hexamers of (S ₆) symmetry, which are further linked by two C—H…O hydrogen bonds to form a three‐dimensional framework structure. In compound (II), inversion‐related pairs of N—H…O hydrogen bonds link the spiro[indoline‐3,3′‐pyrrolizine] molecules into simple R ₂²(8) dimers.     

Synthesis and mass spectrum of 3,3′-thiobispyridine and polarographic reduction of 1,1′-dimethyl-3,3′-thiobispyridinediium diiodide

3,3′-Thiobispyridine is prepared by reaction of pyridine-3-thiol with 3-bromopyridine. The base peak in the mass spectrum of 3,3′-thiobispyridine is due to the molecular ion which fragments by loss of H, HCN and CS as well as by central bond rupture. The 1,1′-dimethyl diquaternary salt of 3,3′-thiobispyridine is reduced polarographically by a one electron transfer not involving hydrogen to an unstable radical cation at a potential (E_o) of −0.72 V in the pH range 7.4–11.2.     

Synthesis,structure, and conformation of terphenylene-derived azacalix[4]aromatics

Several novel azacalix[4]aromatics constituting terphenylene units have been synthesized via sequential nucleophilic aromatic substitution reactions of 5′-t-butyl-(1,1′:3′,1″-terphenyl)-3,3″-diamine 9 and 5′-t-butyl-(1,1′:3′,1″-terphenyl)– 4,4″-diamine 11 with 1,5-difluoro-2,4-dinitrobenzene and cyanuric chloride, respectively. The bridging –NH– functions of the tetra-nitro substituted azacalix[2]arene[2]terphenylenes 1 and 2 have been transformed to the corresponding –N(CH₃)– bridged azacalix[2]arene[2]terphenylenes 3 and 4 via N-alkylation. Single crystal X-ray analysis revealed that the terphenyl-3,3″-diamine derived azacalix[2]terphenylene[2]triazine 5 adopts a distorted chair conformation in the solid state, and the terphenyl-4,4″-diamine derived azacalix[2]terphenylene[2]triazine 6 was found to adopt a 1,3-alternate conformation.     

Preparation and application of a new glucose sensor based on iodide ion selective electrode

An electrode for glucose has been prepared by using an iodide selective electrode with the glucose oxidase enzyme. The iodide selective electrode used was prepared from 10% TDMAI and PVC according our previous study. The enzyme was immobilized on the iodide electrode by holding it at pH 7 phosphate buffer for 10 min at room temperature. The H₂O₂ formed from the reaction of glucose was determined from the decrease of iodide concentration that was present in the reaction cell. The iodide concentration was followed from the change of potential of iodide selective electrode. The potential change was linear in the 4×10⁻⁴ to 4×10⁻³ M glucose concentration (75-650 mg glucose/100ml blood) range. The slope of the linear portion was about 79 mV per decade change in glucose concentration. Glucose contents of some blood samples were determined with the new electrode and consistency was obtained with a colorimetric method. The effects of pH, iodide concentration, the amount of enzyme immobilized and the operating temperature were studied. No interference of ascorbic acid, uric acid, iron(III) and Cu(II) was observed. Since the iodide electrode used was not an AgI-Ag₂S electrode, there was no interference of common ions such as chloride present in biological fluids. The slope of the electrode did not change for about 65 days when used 3 times a day.     

Synthesis of 3,3′,5,5′-Tetra-<Emphasis Type="Italic">tert</Emphasis>-butyl-4,4′-stilbenequinone and Its Catalytic Activity in the Liquid-Phase Oxidation of Inorganic Sulfides

The oxidation of 2,6-di-tert-butyl-4-methylphenol with hydrogen peroxide in the presence of potassium iodide gave 3,3′,5,5′-tetra-tert-butyl-4,4′-stilbenequinone which catalyzed liquid-phase oxidation of sodium sulfide with oxygen more efficiently than did 3,3′,5,5′-tetra-tert-butyl-4,4′-diphenoquinone.     

Komplexe mit sterisch anspruchsvollen Liganden: IV. Gehinderte Rotation der Ringliganden in Tetrakis(trimethylsilyl)metallocenen des Eisens und des Titans

Variable-temperature ¹H NMR studies have revealed that in 1,1′,3,3′-tetrakis(trimethylsilyl)ferrocene, Fe[η⁵-C₅H₃(SiMe₃)₂-1,3]₂, as well as in 1,1′,3,3′-tetrakis(trimethylsilyl)titanocene dichloride, Ti[η⁵-C₅H₃(SiMe₃)₂-1,3]₂Cl₂, the rotation of the five-membered ring about the metal-ring vector is hindered at lower temperatures. The titanocene complex was prepared from TiCl₃ and bis(trimethylsilyl)cyclopentadienyllithium via Ti[η⁵-C₅H₃(SiMe₃)₂-1,3]₂Cl.