Electrochemical and Spectroscopic Studies of Co(CREATININE)2Cl2

The electrochemical behavior of Co(creatinine)₂Cl₂ was investigated by cyclic voltammetry in organic solvents (DMSO and DMF) and in aqueous solution. Analysis of the results indicates that the electroactive species depend on the nature of the solvent. In DMF a single reduction process Co(II)/Co(I) is observed. In DMSO the redox behavior of the complex changes with the scan rate and a two-electron transfer process can be eventually observed. In aqueous solution the complex immediately decomposes giving rise to the aquo-cation. The characteristic peak of the redox couple Cl₂/Cl^? is observed as a consequence of the chloride released from the coordination sphere. Analysis of the electronic spectra gave additional support to the proposed mechanisms. The Co-Cl and Co-N stretching bands were clearly identified in the low frequency region of the IR spectrum.     

Kinetic control of the transmetalation of labile metalloporphyrins in individual and mixed solvents

Transmetalation reactions of cadmium complexes of tetraphenylporphine (CdTPP, I) and tetrabenzoporphine (CdTBP, II) in individual and mixed solvents have been investigated. For individual solvents, provided that the reaction proceeds via the same mechanism, its rate generally increases as the donor number increases in the order DMSO < DMF < PrOH-1 < MeCN (CdTPP-Zn(OAc)₂-Solv system). On passing to the CdTPP-Cu(OAc)₂-Solv system, the reaction rate order changes to DMSO < PrOH-1 < MeCN < DMF because the transmetalation mechanism changes from mixed to associative, as follows from the reaction order with respect to the salt being zero. The effect of the DMSO-DMF mixed solvent on the transmetalation reaction is limited to changing the reaction rate through alteration of the stability of the [CuX₂(Solv¹) _{n ? m ? 2}(Solv²) _m ] solvated salts. The trans effect of the ligands in the solvated salts does not increase the transmetalation rate.     

An investigation into the initial degradation steps of four major dye chromophores: study of their one-electron oxidation and reduction by EPR, ENDOR, cyclic voltammetry, and theoretical calculations

The degradation of dyes is frequently initiated by one-electron oxidation or reduction; however, relatively little is known about the initially formed radicals. Acid Green 25 (AG25), Crystal Violet (CVI), Methylene Blue (MB), and Acid Orange 7 (AO7), representing paradigms of four types of commercial organic dyes, were therefore investigated in terms of their redox behavior. Their redox potentials in MeCN and buffered aqueous solutions were determined by cyclic voltammetry. The structures of the one-electron reduced and oxidized dyes were established by EPR spectroscopy and by theoretical calculations on the density functional level of theory.     

Acylation of Cellulose with N,N′‐Carbonyldiimidazole‐Activated Acids in the Novel Solvent Dimethyl Sulfoxide/Tetrabutylammonium Fluoride

Summary: Carboxylic acids were efficiently activated with N,N′‐carbonyldiimidazole (CDI) and applied for the acylation of cellulose under homogeneous conditions using dimethyl sulfoxide (DMSO)/tetrabutylammonium fluoride trihydrate (TBAF) as solvent. The simple and elegant method is a very mild and easily applicable tool for the synthesis of pure aliphatic, alicyclic, bulky, and unsaturated cellulose esters with degrees of substitution of up to 1.9. Products are soluble in organic solvents, e.g., DMSO or N,N‐dimethylformamide (DMF). The cellulose esters were characterized by elemental analysis, FT‐IR, ¹H and ¹³C NMR spectroscopy and show no impurities or substructures resulting from side reactions.

The esterification of cellulose using carboxylic acids activated in situ with N,N′‐carbonyldiimidazole.     

Formation of DMSO and DMF radicals with minute amounts of base

So far overlooked DMSO and DMF form long-lived radicals in the presence of small amounts of bases, DMF radicals being less stable than DMSO radicals. In solvent mixtures, the presence of DMSO prolonged the lifetime of DMF radicals. The occurrence of radicals may explain previously reported unexpected outcomes of reactions performed in these solvents. The commonly accepted inertness of these solvents towards minor quantities of alkali seems not to be warranted.     

Kinetics and reactivity of substituted anilines with 2‐chloro‐5‐nitropyridine in dimethyl sulfoxide and dimethyl formamide

The kinetics of the reaction of substituted anilines with 2‐chloro‐5‐nitropyridine were studied in dimethyl sulfonide (DMSO) and dimethyl formamide (DMF) at different amine concentrations and temperatures in the range 45–60°C. In both solvents the reaction was not a base‐catalyzed one. A plot of ΔH^# versus ΔS^# for the reaction in DMSO and DMF gave good straight lines with isokinetic temperatures 128°C and 105°C, respectively. Good linear relationships were obtained from the plots of log k₁ against σ° values at all temperatures with negative ρ values (?1.63 to ?1.28 in DMSO) and (?1.26 to ?0.90 in DMF). © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 645–650, 2002     

Effects of mercaptides on anionic polymerization. III. Polymerization of methyl methacrylate by thiophenoxides in polar aprotic solvents

Sodium thiophenoxide initiated the polymerization of methyl methacrylate in polar aprotic solvents (DMF, DMSO, HMPA). The active species that initiated the polymerization of the monomer was found by spectrophotometric measurements and by the sodium fusion method to be sodium thiophenoxide itself. The activation energy for the polymerization of the monomer in DMF solvent obtained was E = 3.4 kcal/mole below 30°C, and E = ?3.3 kcal/mole above the temperature. The phenomena were reasoned as the result of the formation of two active species: a solvent-separated ion pair and a contact ion pair. The effects of counterions on the reactivity of thiophenoxide increased with increasing electropositivity of the metals: Li < Na < K. Sodium phenoxide, the oxygen analog of thiophenoxide, was also found to initiate the polymerization of the monomer in the solvents. The relative reactivity of thiophenoxide to phenoxide for the monomer in HMPA at 30°C was thus determined: phenyl-SNa > phenyl-ONa. The relative effect of the polar aprotic solvents on the reactivity of thiophenoxide was also as follows: HMPA > DMF > DMSO. The kinetic studies were made by the graphical evaluation of rate constants. The following results were obtained for the monomer at 20°C in DMF solvent: K_p = 3.5 × 10² 1./mole-hr and K_t = 9.8 × 10^?2/hr.     

Activation of alkyl halides at the Cu0 surface in SARA ATRP: An assessment of reaction order and surface mechanisms

The external order in reagents for the activation of alkyl halides by Cu⁰ was investigated in supplemental activator and reducing agents (SARA) ATRP. Using methyl 2-bromopropionate (MBrP) or ethyl α-bromophenylacetate (EBPA) and tris(2-(dimethylamino)ethyl)amine (Me₆TREN) in DMSO and MeCN, it was determined that the rate of activation scaled with (S/V)^0.9 in both solvents. For MBrP, the rate was first order with respect to [MBrP]₀ until a saturation in the rate was observed around 33 and 110 mM in DMSO and MeCN, respectively. For EBPA, the reaction was also first order until a maximum rate was observed at 33 mM in DMSO, whereas an inverse order was observed for concentrations above 66 mM in MeCN. At saturated concentrations of MBrP, it was found that the rate increased linearly with respect to [Me₆TREN]₀ for all systems but became asymptotic with a maximum rate of 2 × 10⁻⁶ and 4 × 10⁻⁵ M s⁻¹ in DMSO and MeCN, respectively. Model polymerizations in the absence of ligand showed slow reaction rates, indicating the necessity for ligand. The results allow more accurate modeling and understanding of SARA ATRP under a large range of initiator concentrations. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3048–3057     

Synthesis and optoelectronic properties of conjugated phosphorescent copolyfluorenes containing iridium complexes in main chains and light-emitting diodes formed on their basis

New copolyfluorenes containing covalently bound iridium β-diketonate complexes (featuring high values of phosphorescence efficiency) in the backbone are synthesized through the targeted selection of molar ratios of monomers containing functional groups responsible for various irradiation regions under conditions of the Yamamoto reaction. All copolymers show solubility in organic solvents, such as DMF, DMAA, DMSO, toluene, THF, and chloroform, and feature reversible redox electrochemical properties. The electroluminescence spectra of the copolymers show broad intense bands in the visible region with maxima at 482–538 nm and a maximum brightness of 320 cd/m² at a current density of 2900 A/m². The iridium-containing copolyfluorenes are of interest as effective electroluminescent materials for light-emitting diodes.     

CO2在铜电极上的电还原行为

对常温常压下的MeCN, DMF和DMSO等3种有机溶剂中的CO2的电还原反应行为进行了研究, 求得了传递系数和扩散系数, 并证明了在MeCN, DMF和DMSO中, CO2的还原反应是受扩散控制的不可逆过程.     

Keggin型多金属氧酸盐[XW11MoO40]n-(X=P, Si, Ge ；n=3, 4)在水和二甲基酰胺溶液中的电化学行为

The electrochemical behavior of monomolybdenum-substituted Keggin-type polyoxometalates [XW11MoO40]^n- （X=P, Si, Ge with n=3, 4） was studied in aqueous and N,N-dimethylformamide （DMF） solution. These anionic clusters showed different electrochemical behaviors in two kinds of media. The initial potentials of [XW11MoO40]^n- in DMF were more negative than those in aqueous solution, showing a lower oxidation ability of [XW11MoO40]^n- in DMF. The investigation results suggested that the redox properties of polyoxometalates be tuned by the substitutions of Mo for W and by replacing aqueous solution with organic solvent, which provided valuable information to rationally choose polyoxometalates （POM） in preparation of POM-based organic/inorganic hybrid materials.     

Preparation of no-carrier added 16-131I-hexadecanoic acid via halogen exchange: Comparison between two methods

A simple method for labelling of 16-Br-hexadecanoic acid (16-BrHDA) with radioactive iodine has been reported via nucleophilic¹³¹I-for-Br exchange in the dry state and in organic solvents. While preparation in some organic solvents such as acetic acid, dimethyl formamide (DMF) and dimethyl sulfoxide (DMSO) required reaction times of more than 2 hours to give yields of 20–50%, halogen exchange in dry state at temperature of about 100 °C gave rise to yields of about 94% of radiochemically pure 16-¹³¹IHDA within 5 min. The labelling product could be purified by high performance liquid chromatography (HPLC) and was shown to be free of significant radiochemical impurities.     

Thiophene–nitroxide radical as a novel combination of sensitizer–redox mediator for dye-sensitized solar cells

We report a novel combination of organic sensitizer and redox mediator in the electrolyte for dye-sensitized solar cells (DSSCs): a thiophene dye and nitroxide radicals. Nitroxide radicals and their oxidized counterparts of oxoammonium cations show robust reversible redox reactions, thus supporting robust DSSC operations. Moreover, their redox potentials (E _1/2) and thus open-circuit voltages (V _OC) can be tuned further by attached functional groups. Optical and electrochemical characterization reveal that these new combinations exhibit enhanced V _OC and power conversion efficiencies compared to the existing iodine mediator (I⁻/I₃⁻) due to the increased V _OC. Also, the selection of the sensitizer–redox mediator turns out to be critical in the overall cell performance. Indeed, the typical ruthenium dye loses its light absorption capability when it is operated in conjunction with the nitroxide radicals.     

Solvation of Aniline in Mixtures of Water with N,N-Dimethylformamide and Acetonitrile

Thermal effects of aniline solution in water-N,N-dimethylformamide (DMF) and water-acetonitrile mixtures were measured at 25°C. In almost the whole range of compositions of the mixed solvents, the thermal effects are more positive in aqueous acetonitrile than in aqueous DMF. Particular attention was given to binary solvents with a very low content of the organic cosolvent. In the mixture with the mole fraction of DMF of 10^{- 3}, the enthalpy of aniline solution is higher than in water by 5%, and in the mixture with the mole fraction of acetonitrile of 4 × 10^{- 4}, even by 15%. Features of specific solvation of aniline and an aliphatic amine (n-BuNH₂) in the water-DMF mixture were discussed taking into account the acid-base properties of the mixtures. The coefficients of pair interactions aniline-organic solvent in water and aniline-water in the organic solvent were calculated using the McMillan-Mayer theory. These coefficients correlate with the enthalpies of hydration of aprotic solvent molecules.     

Isomeric Effects on Structures and Properties of Polyaminophenols Synthesized in Basic Medium

The oxidative chemical polymerizations of three isomers of aminophenol, ortho, meta, and para (PoAP, PmAP, PpAP) were performed in aqueous NaOH using ammonium persulfate (APS) as oxidant. Solubility tests for the synthesized polymers were performed in various solvents and it was found that all three polymers are soluble in DMSO and DMF. PpAP is soluble in aqueous strong acid, as well as in base, but PoAP is soluble in acid, whereas PmAP is soluble in base. The difference in their solubility is due to their structural difference, which can be supported by the proposed mechanisms of polymerizations. The film casting from the DMF or DMSO solution of PoAP and PpAP is difficult due to the presence of quinone impurity while casting of PmAP film from DMSO solution is possible. The intrinsic viscosities of the polymers were determined from the DMSO solution. The polymers were characterized by UV-VIS, FTIR and¹H-NMR spectroscopy and elemental analyses. From structural analysis, it is found that PoAP and PpAP do not contain π -electron conjugation due to ether linkage in the backbone chain. So, PoAP and PpAP do not show any conductivity like sulfuric acid doped PmAP.     

Electrochemical polymerization of thianaphthene

Thianaphthene has been electrochemically polymerized in pure boron trifluoride diethyl etherate (BFEE) solution or in a mixed electrolyte of BFEE and concentrated sulfuric acid (SA). The addition of a certain amount of sulfuric acid into BFEE accelerated the polymerization and also increased the current efficiency of the electrosynthesis. Poly(thianaphthene) (PTN) in the dedoped state is soluble in usual strong polar organic solvents such as dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF) and N-methyl pyrrolidinone (NMP). Its structure has been examined by infrared, H¹-NMR and UV spectra. Fluorescent spectral studies indicate that the polymer is a strong blue light emitter.     

Calculation of the equilibrium constants and cooperative parameters of formation of Cu(II) chloride complexes in nonaqueous solvents

Copper(II) distributions over chloride complexes in various organic solvents were analyzed in terms of a modified matrix model. The equilibrium coordination constants of a first ligand and the corrections for the mutual influence between the ligands during the complexation were calculated. It was demonstrated that displacement of the solvent molecule by a chloride ion from the inner coordination sphere of the Cu(II) ion is always of anticooperative character. In MeCN, addition of a chloride ion to a copper ion follows the simplest additive scheme of coordination of the ligand with equivalent coordination vacancies. Possible reasons for nonadditive complexation in DMF, DMSO, trimethyl phosphate, and propylene carbonate are discussed.     

Mechanism of charge-transfer polymerization. V. Photopolymerization and photocyclodimerization of N-vinylcarbazole in the N-vinylcarbazole–oxygen–solvent system

Photochemical reactions of N-vinylcarbazole (VCZ), studied in various solvents, were profoundly influenced by the atmosphere. In the deaerated system radical polymerization of VCZ occurred in various solvents, e.g., tetrahydrofuran, acetone, ethyl methyl ketone, acetonitrile, methanol, sulfolane, N,N-dimethylformamide (DMF), or dimethyl sulfoxide (DMSO). By contrast, when dissolved oxygen was present, cyclodimerization of VCZ occurred exclusively to give trans-1,2-dicarbazole-9-yl-cyclobutane in such polar, basic solvents as acetone, ethyl methyl ketone, acetonitrile or methanol. In stronger basic solvents, i.e., sulfolane, DMF, or DMSO, simultaneous radical polymerization and cyclodimerization of VCZ proceeded, the ratio of the cyclodimerization to the radical polymerization decreasing in the order, sulfolane > DMF > DMSO. In dichloromethane, on the other hand, cationic polymerization of VCZ occurred irrespective of the atmosphere. It is suggested that oxygen acts as an electron acceptor to the excited VCZ, electron transfer occurring in polar solvents from the excited VCZ to oxygen to give transient VCZ cation radical. The effect of solvent basicity on the photocyclodimerization of VCZ is discussed.     

Dendritic Iron Porphyrins with Tethered Axial Ligands: New Model Compounds for Cytochromes

The novel dendritic iron porphyrins of generation zero ([ 1 ⋅Fe^III]Cl), one ([ 2 ⋅Fe^III]Cl), and two ([ 3 ⋅Fe^III]Cl) (Fig. 1) were prepared as models of cytochromes (Schemes 1 and 2). They feature controlled axial ligation at the iron center by two imidazoles tethered to the porphyrin core. Similar to the core compound [ 4 ⋅Fe^III]Cl, they are six‐coordinate low‐spin complexes as demonstrated by UV/VIS (Figs. 3 and 4) and EPR spectroscopy, as well as measurements of the magnetic moments by the Evans‐Scheffold method. The coordination environment does not change upon reduction to the corresponding iron(II) complexes. The dendritic iron porphyrins were purified by size‐exclusion chromatography and shown by matrix‐assisted laser‐desorption‐ionization mass spectrometry (MALDI‐TOF‐MS; Figs. 5 and 6) to be free of structural defects. With their triethyleneglycol monomethyl ether surface groups, the three dendritic mimics are soluble in solvents of widely differing polarity. Electrochemical studies (Figs. 7 and 8) and optical redox titrations (Fig. 9) revealed that the potential of the Fe^III/Fe^II couple in CH₂Cl₂, MeCN, and H₂O shifts strongly to more positive values (by as much as 380 mV) with increasing dendritic generation (Fig. 10). The redox potential of the second‐generation complex [ 3 ⋅Fe^III]Cl is, within experimental error, identical in all three solvents, which clearly demonstrates that the dendritic branching creates a unique local microenvironment around the isolated electroactive core. Whereas, in the organic solvents, the largest anodic potential shift is measured upon changing from generation zero to one, the largest shift in H₂O occurs only at the level of the second generation, when the dendritic superstructure is sufficiently dense to prevent access of bulk solvent to the electroactive core.     

Electron spin resonance studies and theoretical quantum calculations of free radicals generated from anthracenetrione by electrochemical and microsomal reduction

The ESR spectra of radicals obtained by electrolytic reduction of 4,4-dimethylanthracene-1,9,10 (4H)-trione (1) and the regioisomeric quinones 8-acetyloxymethyl-4,4,5-trimethyl- (2), and 5-acetyloxy-methyl-4,4,8-trimethyl-(4H)-1,9,10-anthracenetrione (3) were measured in DMSO and analyzed by quantum chemical calculations. The electrochemistry of these compounds was characterized using cyclic voltammetry, in DMSO and DMF solvents and compared with nifurtimox. The quinones were also reduced by microsomal NADPH-cytochrome P-450 reductase and the corresponding radicals species were also detected by ESR spectroscopy. AMI, INDO, and ADF calculations were performed to obtain the optimized geometries, theoretical hyperfine constants, and spin distributions, respectively. Density functional theory was used to rationalize the reduction potential of these compounds.