Electrophoretic deposition of phthalocyanine in organic solutions containing trifluoroacetic acid

The absorption spectra of copper phthalocyanine (CuPc) 1,2-dichloroethane (DCE) solutions containing trifluoroacetic acid (TFAA) shows that the number of protons coordinating to the CuPc molecule was 1 and 2 for the first and second proton adducts, respectively, which indicates the formations of CuPcH(+) and CuPcH(2)(2+). This CuPc molecule may act as a catalyst to dissociate TFAA into trifluoroacetate anion (A(-)) and H(+) and form the proton adducts. The electrical conductivity dependence of the solution on CuPc concentration also supports this mechanism. A dense film of CuPc was deposited on an indium tin oxide cathode plate by electrophoresis of the solution. Similar dense films of a wide variety of phthalocyanines (MPc; M = Cu, H(2), Fe, Ni, Zn, Pb, VO) were also deposited using this method. Similar films of CuPc were also formed using dichloromethane (DCM) and 1,1,1-trichloroethane (TCE) in place of DCE. Depositions are ascribed to the migration of positively charged monomers (i.e., protonated MPc). Scanning electron microscopy revealed that these films are composed of fibrous crystallites, size of which was found to increase with the electrophoresis time, the strength of the applied electrical field and the concentration of CuPc in the bath. The influence of the dielectric constant of the organic solvent on the film growth is discussed.     

Structure and intramolecular flexibility of beta-cyclodextrin complex with (-)-epigallocatechin gallate in aqueous solvent

The probable structure of the inclusion complex of beta-cyclodextrin (beta-CD) and (-)-epigallocatechin gallate (EGCg) in D2O was investigated using several NMR techniques. EGCg formed a 1:1 complex with beta-CD, in which the A ring and a portion of the C ring of EGCg were included at the head of the phenolic hydroxyl group attached to C7 of EGCg in the beta-CD cavity from the wide secondary hydroxyl group side. In the 1:1 complex with beta-CD, EGCg maintained the conformation in which the B and B' rings of EGCg took pseudoequatorial and pseudoaxial positions with respect to the C ring, respectively. The structure of the inclusion complexes of beta-CD and EGCg obtained from NMR experiments supported those determined from AM1 semiempirical SCF MO calculations well.     

One-electron reduction of kinetically stabilized dipnictenes: synthesis of dipnictene anion radicals

The redox behavior of kinetically stabilized dipnictenes, BbtE=EBbt [E = P, Sb, Bi; Bbt = 2,6-bis[bis(trimethylsilyl)methyl]-4-[tris(trimethylsilyl)methyl]phenyl], was systematically disclosed using cyclic voltammetry and theoretical calculations. It was found that they showed reversible one-electron redox couples in the reduction region. The anion radical species of the Bbt-substituted diphosphene and distibene were successfully synthesized by the reduction of the corresponding neutral dipnictenes (BbtP=PBbt and BbtSb=SbBbt). Their structures were reasonably characterized by ESR, UV-vis, and Raman spectroscopy, and the distibene anion radical was structurally characterized by X-ray crystallographic analysis.     

Free-radical polymerization of vinyl esters using fluoroalcohols as solvents: Effect of monomer structure on stereochemistry

Free-radical polymerization of vinyl esters including vinyl propionate (VPr), vinyl isobutylate (ViBu), vinyl 2,2-dimethylbutylate (VDMB), vinyl 2,2-dimethylvalerate (VDMV), vinyl 2,2-bis(trifluoromethyl)propionate (VF6Pi), and vinyl benzoate (VBz) was carried out using fluoroalcohols as solvents, and the tacticity of the obtained polymers was determined by NMR analysis of the produced poly(vinyl alcohol) (PVA). The polymerization of VPr, ViBu, VDMB, and VDMV, which are bulkier than VAc, in fluoroalcohols afforded polymers rich in heterotacticity (up to mr = 61%) similar to that of vinyl pivalate (VPi) whereas VAc is known to give a syndiotactic polymer under the reaction conditions used here. The polymerization of VF6Pi, which is the bulkiest among the monomers used in this study, gave a polymer rich in syndiotacticity in bulk and in fluoroalcohols regardless of the structure of the solvents. On the other hand, the polymerization of VBz in fluoroalcohols gave polymers with a higher isotacticity (up to mm = 33%) than bulk polymerization. Thus the monomer structure strongly affected the stereochemistry of the free-radical polymerization of vinyl esters in fluoroalcohols. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2677–2683, 1999     

Free‐radical copolymerization of vinyl esters using fluoroalcohols as solvents: The solvent effect on the monomer reactivity ratio

Free‐radical copolymerizations of vinyl acetate (VAc = M₁) and other vinyl esters (= M₂) including vinyl pivalate (VPi), vinyl 2,2‐bis(trifluoromethyl)propionate (VF6Pi), and vinyl benzoate (VBz) with fluoroalcohols and tetrahydrofuran (THF) as the solvents were investigated. The fluoroalcohols affected not only the stereochemistry but also the polymerization rate. The polymerization rate was higher in the fluoroalcohols than in THF. The accelerating effect of the fluoroalcohols on the polymerization was probably due to the interaction of the solvents with the ester side groups of the monomers and growing radical species. The difference in the monomer reactivity ratios (r₁, r₂) in THF and 2,2,2‐trifluoroethanol was relatively small for all reaction conditions and for the monomers tested in this work, whereas r₁ increased in the VAc‐VF6Pi copolymerization and r₂ decreased in the VAc‐VPi copolymerization when perfluoro‐tert‐butyl alcohol was used as the solvent. These results were ascribed to steric and monomer‐activating effects due to the hydrogen bonding between the monomers and solvents. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 220–228, 2000