SYNTHESES AND PROPERTIES OF POLYMERIZABLE METALLOPHTHALOCYANINE DERIVATIVES

Metallophthalocyanine derivatives with polymerizable vinyl groups were synthesized, characterized and polymerized. Preliminary results on their Langmuir-Blodgett (LB) film formation and the electronic properties of (Indium-Tin Oxide/LB-film/Al) Schottky devices were reported.     

Effect of drying on the mesoporous structure of sol-gel derived silica with PPO-PEO-PPO template block copolymer

The effects of drying method on the pore structure of mesoporous silica were studied from the viewpoint of enhancing closed porosity in mesoporous silica. The mesoporous silica was prepared via a sol-gel process using polyethyleneoxide-polypropyleneoxide-polyethyleneoxide (PEO-PPO-PEO) triblock copolymer (Pluronic P123) as the structure-directing template. The closed porosity was evaluated from the apparent mass density of the sample measured by a helium pycnometer. These mesoporous silicas were also characterized by transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and nitrogen adsorption. The drying method was shown to be responsible for the finally templated mesoporous structure of the silica. More rapid drying is more preferable for enhancing the closed porosity of the mesoporous silica. The closed pores were formed by immediate immobilization of copolymer molecular assemblies in the silica matrix due to the instant removal of the solvent and solidification at higher temperatures. The drying method, mainly affecting the drying rate, is highly influential on the finally replicated mesoporous structure in silica.     

A tin-complexation strategy for use with diverse acylation methods in the preparation of 1,9-diacyldipyrromethanes

The acylation of dipyrromethanes to form 1,9-diacyldipyrromethanes is an essential step in the rational synthesis of porphyrins. Although several methods for acylation are available, purification is difficult because 1,9-diacyldipyrromethanes typically streak extensively upon chromatography and give amorphous powders upon attempted crystallization. A solution to this problem has been achieved by reacting the 1,9-diacyldipyrromethane with Bu(2)SnCl(2) to give the corresponding dibutyl(5,10-dihydrodipyrrinato)tin(IV) complex. The reaction is selective for dipyrromethanes that bear acyl groups at both the 1- and 9-positions but otherwise is quite tolerant of diverse substituents. The diacyldipyrromethane-tin complexes are stable to air and water, are highly soluble in common organic solvents, crystallize readily, and chromatograph without streaking. Four methods (Friedel-Crafts, Grignard, Vilsmeier, benzoxathiolium salt) were examined for the direct 1,9-diacylation of a dipyrromethane or the 9-acylation of a 1-acyldipyrromethane. In each case, treatment of the crude reaction mixture with Bu(2)SnCl(2) and TEA at room temperature enabled facile isolation of multigram quantities of the 1,9-diacyldipyrromethane-tin complex. The diacyldipyrromethane-tin complexes could be decomplexed with TFA in nearly quantitative yield. Alternatively, use of a diacyldipyrromethane-tin complex in a porphyrin-forming reaction (reduction with NaBH(4), acid-catalyzed condensation with a dipyrromethane, DDQ oxidation) afforded the desired free base porphyrin in yield comparable to that obtained from the uncomplexed diacyldipyrromethane. The acylation/tin-complexation strategy has been applied to a bis(dipyrromethane) and a porphyrin-dipyrromethane. In summary, the tin-complexation strategy has broad scope, is compatible with diverse acylation methods, and greatly facilitates access to 1,9-diacyldipyrromethanes.     

Synthesis of fusible and soluble conducting polyfluorene derivatives and their characteristics

Conducting polyfluorene derivatives with alkyl chains—poly(9-alkylfluorene)s and poly-(9,9-dialkylfluorene)s—have been synthesized by chemical polymerization utilizing FeCl₃ as an oxidizing agent. The polymers obtained are found to be soluble in conventional organic solvents such as chloroform and have been characterized by ¹H- and ¹³C-NMR. The results indicate that the fluorene moeities are mainly linked in the 2,7′-fashion to yield the straight chain polymer. The degree of polymerization is estimated (by gel permeation chromatography) to be of the order of 10. The polymers are found to be fusible and the thermal properties of the polymers have been characterized by differential scanning calorimetry. The glass transition temperature is found to decrease with an increase of the alkyl chain length. © 1993 John Wiley & Sons, Inc.     

Regulation of saccharide binding with basic poly(ethynylpyridine)s by H+-induced helix formation

A basic host polymer exhibiting pH-regulatable saccharide recognition has been investigated. Poly(m-ethynylpyridine) bearing dialkylamino groups forms helical complexes with saccharides to show induced circular dichroism (ICD). When trifluoroacetic acid was titrated on these complexes, the ICD was gradually enhanced until the amount of the acid reached ca. 0.5 molar equivalence versus the pyridine rings in the polymer, and further addition of the acid suppressed the ICD. The proper addition of the acid also increased the binding constants between the polymer and saccharides. These findings would be due to stabilization of the helical structure consisting of cisoid conformations for each of the adjacent pyridine pairs, which were caused by half-protonation of the pyridine rings. Computational analyses indicated that the pyridinium-pyridine dimeric structure prefers its cisoid conformation to its transoid one.     

Brewster angle microscopic observations of the Langmuir films of amphiphilic spiropyran during compression and under UV illumination

The structure of the Langmuir film of an amphiphilic spiropyran, 1',3'-dihydro-3',3'-dimethyl-6-nitro-l'-octadecyl-8-(docosanoyloxyme thyl)spiro[2H-1-benzopyran-2,2'-(2H)-indole] (SP), is investigated using Brewster angle microscopy (BAM). The BAM observations show that the Langmuir film of SP can be roughly categorized into three regimes: a low-temperature regime at 7-13 degrees C; a medium-temperature regime at 23-30 degrees C; a high-temperature regime at 40 degrees C. The low-temperature regime is characterized both by the domains that are formed just after the spreading and by the onset of the surface pressure when the domains are merged together to form continuous trilayers. In the medium-temperature regime, a continuous monolayer film is formed after the solvent evaporation, followed by the growth of "embryos" with compression. Around the phase transition point, the "embryos" serve as the "nucleation sites" of the circular trilayer domains. The characteristic features of the high-temperature regime are similar to the ones of the medium-temperature regime except for the absence of a steep rise in surface pressure after the plateau region and the absence of the circular trilayer domains. UV illumination of the Langmuir films leads to the isomerization of SP into merocyanine (MC). However, J-aggregates of MC are formed only when the circular trilayer domains are present. On the basis of the above results, we present a phase diagram of the Langmuir film of SP. The structure and photoreaction depend strongly on the phase of the Langmuir film, indicating that the area/molecule is not the only decisive parameter.     

Energy Sequence of the Lowest Antibonding Orbitals in Symmetrical Didehydro[n]annulenes with n = 4N+2

A model of a perturbed n-membered perimeter (n = 4N + 2) is used to interpret the ESR.-data for the radical anions of symmetrical tetra-t-butyl-didehydro[n]annulenes with n = 14, 18, 22 and 26 (N = 3, 4, 5 and 6). The singly occupied orbital of such radical anions correlates with one of the doubly degenerate, lowest antibonding perimeter MO's which have been classified as symmetric (Ψ_S) or antisymmetric (Ψ_A) with respect to the mirror plane passing through two opposite centres and perpendicular to the plane of the perimeter. The relevant MO is Ψ_S for n = 14 (N = 3) and 22 (N = 5), but Ψ_A for N = 18 (N = 4) and 26 (N = 6), in accordance with the prediction of the model. It has been shown that the introduction of two symmetrically placed triple bonds into a (4N + 2)-membered perimeter should stabilize Ψ_S and destabilize Ψ_A when N is odd, whereas the reverse should hold when N is even.     

Automatic microdistillation flow-injection system for the spectrophotometric determination of fluoride

An automatic flow-injection (FI) system including on-line separation by microdistillation and spectrophotometric detection has been developed for the determination of trace amounts of fluoride. This ion was separated from sample matrix by distillation in the presence of sulfuric and phosphoric acids, and was subsequently determined with spectrophotometry based on the mixed-ligand complex of lanthanum(III)-fluoride-alizarin complexone. The proposed FI system has high sampling frequency (20 samples h⁻¹), small sample size (600 μl) and the dynamic range of 0.05-15 mg l⁻¹ with relative standard deviations of below 1.2%. Interfering ions such as aluminum(III) and iron(III) was effectively eliminated. The method was successfully applied to the determination of fluoride in industrial drainage after water treatment.     

Squid chitin as a potential alternative chitin source: Deacetylation behavior and characteristic properties

β-Chitin was isolated from squid pens, and the characteristic chemical and physical properties were elucidated in comparison with those of shrimp chitin, α-chitin. Deacetylation behavior of the squid chitin was first studied to look into the reactivity of β-chitin and also to establish an efficient procedure for preparing squid chitosan. The squid chitin proved to show much higher reactivity in alkaline deacetylation than shrimp chitin. Although it was deacetylated quite easily, the product assumed a dark brown color under the ordinary reaction conditions for shrimp chitosan. Squid chitosan was successfully prepared by repeated alkaline treatments under mild conditions, particularly with high concentration alkali at low temperatures, without appreciable discoloration. The structural characteristics of the squid chitin were discussed on the basis of the IR and x-ray analysis data. The crystalline structure of squid chitin was destroyed easily on deacetylation compared to that of shrimp chitin, and moreover, the resulting squid chitosan was amorphous unlike crystalline shrimp chitosan. The squid chitin was characterized by the remarkable affinity for organic solvents and water. Squid chitin and chitosan also showed much higher hygroscopicity and retention of the absorbed water than shrimp chitin and chitosan and are considered to be useful as highly hydrophilic materials. © 1993 John Wiley & Sons, Inc.     

High-Temperature Synchrotron X-Ray Powder Diffraction Study of the Orthorhombic-Tetragonal Phase Transition in La0.63(Ti0.92,Nb0.08)O3

The crystal structure of La_0.63(Ti_0.92,Nb_0.08)O₃ has been refined by the Rietveld analysis of CuKα X-ray powder diffraction data collected at 23°C. This material was confirmed to have an A-site deficient orthorhombic perovskite-type structure with double ideal perovskite ABO₃ units along the c-axis (space group Pmmm, Z=2, a=3.86036(5) Å, b=3.87222(5) Å, c=7.82609(9) Å). Lattice parameters of the same sample have been investigated in situ in the temperature range from 25°C to 496°C by 1.37873(3) Å synchrotron X-ray powder diffraction. The synchrotron X-ray powder diffraction technique was found to be very powerful to determine precise lattice parameters around a phase transition temperature. This compound exhibited a reversible phase transition between the orthorhombic and tetragonal phases at around 370°C. (1) The lattice parameters increased continuously with temperature, while the b/a ratio decreased continuously with temperature and became unity at the orthorhombic-tetragonal transition point. (2) No hysteresis was observed in the lattice parameter values between heating and cooling. These results of (1) and (2) suggest that the orthorhombic-tetragonal phase transition is continuous.