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Abstract: New chiral salen-type Cu(II) complexes (1-9) were prepared, and the effects of different substituent groups on their absorption spectra were evaluated using time-dependent density functional theory (TD-DFT). Electron withdrawing groups resulted in a red-shift and an increase in the peak intensity. According to cyclic voltammetry analyses, the introduction of electron withdrawing groups brought the redox potentials (E0) in agreement with the orbital level energies determined via TD-DFT. The reduction potentials for 1-9 are less than −0.500 V, and therefore, it is electrochemically possible to dope electrons in TiO2. In addition, the oxidation potentials are greater than +0.200 V, indicating that it is electrochemically possible to regenerate the dyes. Preproduction dye-sensitized solar cells (DSSCs) fabricated using compounds 1-9 generated electricity. In particular, the DSSC prepared using 2 (which has electron withdrawing groups and the largest maximum absorption) exceeded the power conversion efficiency of DSSC fabricated using N3, which is a commonly used Ru(II) complex. Keywords: DSSC, Copper(II), Schiff base, Chirality, Crystal structure.Download Full Article |
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Abstract: Acrylic, methacrylic and itaconic acids have Brønsted acidity given by carboxylic groups, and they are extensively used in polymerization for modification of several soft-mater materials. By this reason it is important to propose better characterization studies and alternatives to obtain more of their physicochemical properties. In this work the pKa values of these acids are obtained by adjusting NMR chemical shifts for hydrogen and carbon nuclei as a function of pH with program HYPNMR, and compared with those obtained by potentiometric and conductometric titrations. Keywords: pKa values, acrylic acid derivatives, HYPNMR, 1H NMR, 13C NMR.Download Full Article |
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Abstract: Over the past decade, catalysis by ionic liquids (ILs) has experienced a tremendous growth in the context of “Green Chemistry”, and there are numerous examples of a variety of catalytic reactions that have been successfully carried out in such neoteric media. The great enthusiasm for catalysis in ILs is not only driven by the curiosity of chemists, but also due to the growing awareness of developing greener reactions or process media in catalytic science and greener catalytic technologies due their advantages of unique physical and chemical properties as compared to traditional volatile organic solvents. Recently, development of chiral ionic liquids and their applications in asymmetric synthesis have attracted much attention as these reactions have widespread applications in the synthesis of chiral drugs and pharmaceutical industries. Asymmetric induction is mainly achieved by the use of chiral substrates or reagents, chiral catalysts or enzymes. Owing to the vast number of structurally different room temperature ILS that have been synthesized, this review focuses on imidazolium ionic liquids that possess chirality either in the imidazolium moiety or in the anion moiety. The aim of this review is to highlight the recent breakthrough of Chiral ILs in chirality transfer or chiral recognition when used as solvent or co-solvent: the case of task specific ionic liquids is beyond the scope of this review. In the first part, the synthesis of of CILs has been presented and the second part of the review has been devoted on the applications of such CILs in green asymmetric synthesis as well as various pharmaceutical industries. Keywords: Chiral Imidazolium Ionic Liquids, Chiral Catalyst and Reaction Medium, Green Asymmetric Synthesis, Recyclable Homogeneous Catalyst, Solvent-free Clean Synthesis.Download Full Article |
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Abstract: The preferential solvation parameters by ethanol (EtOH) or propylene glycol (PG) of daidzein were derived from their solution thermodynamic properties by means of the inverse Kirkwood-Buff integrals and the quasi-lattice-quasi-chemical (QLQC) methods. According to IKBI method, the preferential solvation parameter by the co-solvent, δx1,3, is negative in water-rich mixtures but positive in co-solvent-rich mixtures in both kinds of systems. This could demonstrate the relevant role of hydrophobic hydration around the aromatic rings in the drug solvation in water-rich mixtures. Furthermore, the more solvation by co-solvent in co-solvent-rich mixtures could be due mainly to polarity effects and acidic behavior of the hydroxyl groups of the compound in front to the more basic solvents present in the mixtures, i.e. EtOH or PG. Otherwise, according to QLQC method, this drug is preferentially solvated by the co-solvents in all the mixtures in both kind of systems. Keywords: Daidzein, ethanol, propylene glycol, preferential solvation, inverse Kirkwood-Buff integrals, quasi-lattice-quasi-chemical. Download Full Article |
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Abstract: Imidazolium-based chloride ionic liquids (ILs) have exhibited remarkable performance in several important applications such as biomass dissolution and extraction, but their large viscosity is a non-negligible problem. Adding molecular co-solvents into chloride ILs is effective in reducing viscosity; nevertheless, understanding of the accompanied change of thermodynamic polarity is quite few. Therefore, in this work we reported three Kamlet-Taft solvatochromic parameters, including dipolarity/polarizability (ð*), hydrogen-bond acidity (α) and hydrogen-bond basicity (β), for the binary mixtures of several imidazolium-based chloride ILs plus either dipolar protic solvents (water and methanol) or dipolar aprotic solvents (dimethyl sulfoxide, N,N-dimethylformamide and acetonitrile). The results demonstrated that those parameters could be altered by the structure of IL and type of co-solvent owing to the solute-solvent and solvent-solvent interactions. The structure of alkyl chain of cation had considerable impact on the ð* variation of IL aqueous solution against IL concentration but hardly affected other mixtures. Moreover, remarkable preferential solvation of probes was observed for β and α in the mixtures of IL and dipolar aprotic co-solvents, whereas the hydrogen-bond interactions between IL and dipolar protic co-solvent enabled the preferential solvation to be alleviated and resulted in more linear variation of β and α against the molar fraction of IL. The results not only contribute to a better understanding of the effect of co-solvent on imidazolium-based chloride ILs, but also are instructive for improving the thermodynamic performance of IL-based applications via providing IL+co-solvent mixtures with desirable physicochemical properties. Keywords: Polarity, hydrogen bond, basicity, acidity, preferential salvation.Download Full Article |