Motomichi Inoue

New soluble polyaniline: Synthesis, electrical properties and solution electronic spectrum

Abstract The reaction of aniline with copper(II) perchlorate in acetonitrile yields highly-electroconductive polyaniline perchlorate, [(-C6H4NH-)(ClO4)m·nH2O]x, which is soluble in dimethylsulfoxide (DMSO) and has low degrees of branching and/or crosslinking. The conductivity of a material with m = 0.43 is 3.1 S cm−1 at room temperature. The solution electronic spectrum of the perchlorate exhibits a strong band at 285 nm and a weak band at 445 nm; no band is observed in the region of 830 nm. In the solution electronic spectrum of the corresponding polymer base, strong bands are observed at 630 and 325 nm. When the solution of the polymer base is acidified, the 630 nm band disappears and a new band appears at 830 nm: the protonation of the polymer base by the acidification yields a spectrum that is different from that of the original polymer perchlorate. In the polymer chains of the perchlorate prepared by the present method, the majority of positive charges are centred on anilinium ion radicals (polarons) rather than on quinoneiminium ions (bipolarons).

Chemical synthesis of highly conducting polypyrrole by the use of copper(II) perchlorate as an oxidant

Abstract A reaction of pyrrole and copper(II) perchlorate in acetonitrile yielded highly conducting polypyrrole, [(C 4 H 3 N)(C10 4 ) x ·yH 2 O] n : a polymer with x = 0.35 and y = 0.25 exhibited a conductivity of 60 S cm −1 and a very low activation energy of 0.011 eV. The e.s.r. spectrum was asymmetric and the g value was 2.0017 that was slightly smaller than the free electron value. These are suggestive of a Dysonian line due to a metal-like charge transport along polymer chains. Materials treated with NH 4 OH solution showed an infrared spectrum characteristic of polypyrrole.

Potentiometric and 1H NMR studies of complexation of Al3+ with (−)-epigallocatechin gallate, a major active constituent of green tea

The acid dissociation of (-)-epigallocatechin gallate (abbreviated as egcg) and its complexation with Al(3+) were studied by potentiometric titrations, and were compared with those of (-)-epicatechin (ec) and (-)-epigallocatechin (egc). In Al(3+)-ec and Al(3+)-egc reaction systems, [Al(LH(-2))](+), [Al(LH(-2))(OH)](0), and [Al(LH(-2))(2)](-) are formed, as reported for Al(3+)-catechin (c). Reactions between Al(3+) and egcg at pH <4.1 yield AlLH(-2) and AlLH(-3) species. The 1H NMR studies have shown that two hydroxyl groups of the gallate (D) ring are deprotonated and coordinated to an Al(3+) ion in [Al(egcgH(-2))](+). The AlLH(-3) species of egcg is supposed to be formulated as [Al(egcgH(-3))](0) in which one hydroxyl group of the pyrogallol (B) ring and two hydroxyl groups of the D ring are deprotonated; an Al(3+) ion is coordinated to two oxygen atoms of the D ring and one oxygen atom from the B ring of the neighboring chelate molecule, resulting in the formation of a polymeric structure. In the Al(3+) complex of egcg, the gallate group forms major coordinate bonds and results in solution properties that are different from those of ec, egc and c which have no gallate group.

One-step chemical synthesis of doped polythiophene by use of copper(II) perchlorate as an oxidant

Abstract A reaction of 2,2′-bithiophene with copper(II) perchlorate in acetonitrile achieved polymerization and doping in one step, and yielded polythiophenes, [(C4H2S)(ClO4)x·yH2O]n. The polymers with x ∼ 0.17 and y ∼ 0.3 exhibited a high electrical conductivity in the range 3 – 8 S cm−1 at 300 K and a small activation energy of 0.04 eV. The i.r. and e.s.r. spectra showed the characteristics of doped polythiophenes.

Complexation of electroconducting polypyrrole with copper

Abstract A copper complex of polypyrrole is obtained when the polymer perchlorate is treated with a Cu(II)-containing alkaline solution. The X-ray photoelectron spectrum of the resulting polymer material shows that the copper atoms are coordinated to pyrrole nitrogen. The ESR signal of copper ions and that of the pyrrole rings are observed independently of each other; there is no appreciable magnetic interaction between the two paramagnetic species. The room-temperature conductivity is 4 × 10−4 S cm− and the temperature dependence shows semiconductive behavior with an activation energy of 0.11 eV. The degradation of conducting polypyrrole in aqueous solution is suppressed by the presence of copper: the stabilization is attributed to CuN bond formation.

Amorphous and crystalline copper sulfides, CuS

Copper sulfides CuS have been synthesized by a reaction between [Cu(en)2]2+(en = ethylenediamine) and thiourea in alkaline solutions at different temperatures. The product obtained at 10 °C (CuS-10) was amorphous and showed semiconductive properties with an electrical conductivity of 0.1 S cm–1 at 298 K and 3.6 × 10–3 S cm–1 at 108 K, whereas the product at 30°C (CuS-30) was a crystalline CuS (covellite) that exhibited a metal-like temperature dependence with a conductivity of 92 S cm –1 at 304 K and 101 S cm–1 at 101 K. CuS-10 was changed to a crystalline CuS when annealed at 100-150°C. The resulting CuS had a higher crystallinity than that of CuS-30, and the electrical conductivity showed a metal-like temperature dependence: 27 S cm–1 at 299 K and 31 S cm –1 at 98 K. When the reactions were conducted with an immersed polymer film in the solution, CuS films were formed on the substrate surface. The CuS-30 film and the annealed CuS-10 film were electroconductive and transparent in the visible spectral region. The synthesis of amorphous CuS followed by thermal treatment is a new method for the fabrication of metal sulfide films of high quality.

Binuclear structure in the ammonium salt of gadolinium(III) diethylenetriaminepentaacetate, (NH4)4[Gd2(DTPA)2]·6H2O

Abstract A single crystal X-ray analysis of the ammonium salt of Gd 3+ diethylenetriaminepentaacetate has shown that the compound has a binuclear structure in contrast to the corresponding sodium salt that has a mononuclear structure. Five oxygen atoms and three nitrogen atoms from a ligand molecule construct a distorted square antiprism around a Gd 3+ ion. One of the square planes is capped by an oxygen atom from the adjacent metal chelate molecule, resulting in the formation of a binuclear metal chelate. The coordination polyhedron including this oxygen atom is described as a tricapped trigonal prism. The binuclear structure is the result of well-developed hydrogen bonds that involve the ammonium ions.

1H NMR and protonation constants of new metal-chelating macrocycles, oxocyclopolyamines with pendant carboxymethyl groups, and the stabilities of their Mg2+ and Ca2+ complexes

Potentiometry and 1H NMR have been used to study the protonation of a new series of 12−, 13−, 15−, 16− and 17-membered metal-chelating macrocycles with two or three pendant carboxymethyl groups. In the 12− and 13-membered macrocycles, ethylenediaminetetraacetate and ethylenediamine or propanediamine units are linked by two amide groups; in the 15−, 16−, and 17-membered macrocycles, diethylenetriaminepentaacetate and diamine units are linked by two amide groups. The protonation constants Kn (n = 1, 2, 3) of these new macrocyclic ligands are significantly smaller than the corresponding values for tetraaza and triaza macrocycles such as 1,4,7,10-tetraazacyclododecane-N,N′,N″,N″′-tetraacetic acid (DOTA) and 1,4,7-triazacyclononane-N,N′,N″-triacetic acid (NOTA). The protonation sites have been identified by measuring the 1H NMR chemical shifts at different pD values. Protonation corresponding to K1 occurs on the amine nitrogen atoms. In the successive protonations, protons are distributed on the amine nitrogen atoms and the carboxylate oxygen atoms so as to minimize electrostatic repulsion. The low basicities of the amine nitrogen atoms in these new macrocycles are attributable to the introduction of amide groups into the ring system. As a consequence of the low basicities of the macrocycles, the formation constants of their Mg2+ and Ca2+ chelates are much lower than the corresponding values of EDTA. The ratio of the two formation constants, Kf(Ca)Kf(Mg), varies in an unpredictable manner with the size of the macrolytic ligand.

Syntheses of new 15-membered and 16-membered macrocyclic ligands with three pendant acetato groups and the structures of the gadolinium(III) complexes

Abstract A condensation of diethylenetriaminepentaacetic dianhydride with ethylenediamine gave a 15-membered macrocyclic ligand with three pendant acetato groups, (15-dtpa-en)H3C10H18N5O2(CH2CO2H)3; a l6-membered analogue, (l6-dtpa-pn)H3 C11H20N5O2(CH2CO2H)3, was obtained by the use of propanediamine instead of ethylenediamine. The structures of their gadolinium(III) complexes, Gd2(15-dtpa-en)2·16H2O and Gd(16-dtpa-pn)·4H2O, were determined by X-ray analyses. Gd2(15-dtpa-en)2·16H2O crystallized in the orthorhombic space group Pbca with: a=18.205(1), b=18.930(1) and c=15.609(1) A. Two Gd(III) ions are located between two ligand molecules, forming a binuclear metal chelate molecule with a center of inversion. The coordination geometry around a metal ion is described as a distorted tricapped trigonal prism that consists of nine coordinated atoms. Gd(l6- dtpa-pn)·4H2O crystallized in the monoclinic space group P21/c with: a =8.246(2), b = 14.995(3), c= 19.367(4) A and β = 90.258(2)°. In this compound, a water molecule and a single ligand molecule are coordinated to a Gd(III) ion, forming a mononuclear chelate with a tricapped trigonal prism. The structural differences between the two Gd(III) complexes are a result of the differences in the favorable conformations assumed by the two macrocyclic ligands.

X-ray structures and fluorescence spectra of binuclear Zn2+ and Cd2+ complexes of an amide-based naphthalenophane

Abstract The formation of binuclear Zn2+ and Cd2+ complexes with an amide-based chelating naphthalenophane has been confirmed by X-ray crystal analyses: the complexes are formulated as [(H2O)MLM(OH2)]0 (M=Zn or Cd), and the naphthalenophane, LH4, is 2,9,22,29-tetraoxo-4,7,24,27-tetrakis(carboxymethyl)-1,4,7,10,21,24,27,30-octaaza[10.10](1,5)naphthalenophane. The Zn2+ complex has a six-coordination geometry and the Cd2+ complex has a seven-coordination geometry. The naphthyl groups are deformed from the planar structure by metal complexation in both complexes. Fluorescence from the uncoordinated ligand is weakened by protonation. The coordination of Zn2+ enhances the fluorescence whereas the coordination of Cd2+ weakens the emission: the intensity ratio, F(L):F(Zn2L):F(Cd2L)=1:12:0.2 at pH 10. The Zn2+ complex exhibits a large change in the fluorescence intensity with pH, as a result of interconversion between [(H2O)ZnLZn(OH2)]0 and [(HO)ZnLZn(OH)]2−; the emission of the latter formed at higher pH is 20 times stronger than that of the former formed at lower pH. Structural changes that occur in the chelating units upon protonation or metal complexation propagate to the fluorescent units through the amide groups that link the two functional units. This propagation results in the fluorescence properties characteristic of the amide-based naphthalenophane.