Structural characterization and luminescence studies of new lanthanide(III) complexes with nicotinic and isonicotinic acid N-oxides

Four new polymeric lanthanide(III) complexes of nicotinic acid N-oxide and isonicotinic acid N-oxide have been synthesized and structurally determined. In the isomorphous compounds [(Ln(L-1)(3) (H2O)(2))(n)]. 4nH(2)O(HL1 = nicotinic acid N-oxide; Ln = Eu, 1; Ln = Er, 2) the lanthanide(III) ions form infinite double chains along the b direction through the coordination of bridging carboxylate and N-oxide groups. The chains are cross-linked through hydrogen bonds between aqua ligands and uncoordinated N-oxide groups and between aqua ligands and lattice water molecules, to form a three-dimensional network. [(Eu(L-2)(2)-(H2O)(4))(n)](NO3)(n). nH(2)O (HL2 = isonicotinic acid N-oxide, 3) has a polymeric structure in which the europium (III) ions are connected into infinite chains by pairs of syn-syn carboxylate groups. Adjacent chains are interlinked by hydrogen bonds between aqua ligands and N-oxide groups to form a layer parallel to the (100) plane, and such layers are connected by hydrogen bonds between nitrate anions and aqua ligands, and between oxide groups and lattice water molecules, into a three-dimensional network. In [(Er-2(L-2)(4)(H2O)(10))](NO3)(2). H2O, 4, dinuclear units are inter-linked into a three-dimensional network through hydrogen bonding between aqua ligands and N-oxide groups of both bidentate bridging and unidentate L-2 ligands. Factors affecting the formation of coordination chains and dinuclear units are discussed. Luminescence properties of 1 and 3 have also been studied. (C) 1998 Elsevier Science Ltd. All rights reserved.

Miscibility and specific interactions in poly(beta-hydroxybutyrate-co-beta-hydroxyvalerate) and poly(P-vinylphenol) blends

The blends of poly(beta-hydroxybutyrate-co-beta-hydroxyvalerate) (P(HB-co-HV)/poly(p-vinylphenol)(PVPh) were investigated by differential scanning calorimetry (DSC), Fourier transform IR (FT-IR) spectroscopy and high-resolution solid-state C-13 NMR techniques. Single glass transition temperatures existing in the whole composition range indicates that these blends are miscible. The presence of hydrogen bonding between the hydroxyl of PVPh and carbonyl of P(HB-co-HV), shown by FT-IR spectra, is the origin of the miscibility. Furthermore, results obtained by high-resolution solid-state C-13 NMR give more information about the structure of the blends. (C) 1998 Elsevier Science Ltd. All rights reserved.

Synthesis and characterization of the side chain liquid crystalline poly(monoester {6-[4-(p-nitrophenyl)azo]phenoxy-1-hexyloxy} of maleic anhydride)

The poly(monoester (6-[4-(p-nitrophenyl) azo]phenoxy-1-hexyloxy) of maleic anhydride) shows a smectic phase with a focal conic fan texture. With the decrease of the monoestering degree the phase transition temperature decreases and the mesomorphic temperature range becomes narrow. The hydrogen bonding between two carboxylic acid groups was found to play a very important role in forming the smectic phase structure. The smectic bilayer structure has been built through self-assembly via. intermolecular hydrogen bonding.

Fragmentations of some bifunctional phenylether compounds by intermediate ion/neutral complexes

The fragmentations of three bifunctional phenylether compounds including 2-(2, 6-dichloro)phenoxyl propionitrile, N-hydroxyl-4-butoxyl phenylacetyl amine(bufexamc) and 2-(1-methylethoxyl) phenol methylcarbamate (Propoxur) under electron impact ionization were reported, Metastable ion(MI) and collision-induced dissociation(CID) at a low energy have been used to study the fragmentation pathways from molecular ions. Apart from the simple bond cleavages, and the unimolecular dissociations via ion/neutral complex intermediate as a competitive mechanism were demonstrated, Moreover, the intramolecular hydrogen transfer and double hydrogen transfers in the fragmentations of these compounds were discussed in detail.

Catalytic mechanisms of triphenyl bismuth, dibutyltin dilaurate, and their combination in polyurethane-forming reaction

The catalytic mechanisms of triphenyl bismuth (TPB), dibutyltin dilaurate (DBTDL) and their combination have been studied in a model polyurethane reaction system consisting of copolyether (tetrahydrofuran-ethyleneoxide) and N-100; NMR spectroscopy was used to detect the associations between reactants and catalysts. A relatively stable complex was shown to be formed between hydroxyl and isocyanate; the catalysts showed different effects on the isocyanate-hydroxyl complex, therefore resulting in different curing characteristics. The formation of hydrogen bonding between the complexed hydroxyl and other hydroxyl or the resulting urethane provided an ''auto-catalysis'' to urethane formation. DBTDL destroyed the isocyanate-hydroxyl complex before catalyzing the reaction through the formation of a ternary complex, whereas TPB was able to activate the isocyanate-hydroxyl complex directly to form urethane. The reaction catalyzed by the combination of TPB and DBTDL gained advantages from the multiple catalytic entities, i.e., TPB, DBTDL, and a TPB-DBTDL complex. (C) 1997 John Wiley & Sons, Inc.

New progress in conducting polyaniline

New synthesis system was established to prepare polyaniline (PAn) with controlled molecular weight. The synthesized PAn was completely soluble in many organic solvents such as dimethylsulfoxide (DMSO), dimethylformamide and N-methylpyrrolidone (NMP). The molecular aggregation due to the interaction between PAn and NMP molecules was found in dilute PAn/NMP solution. The gelatin of concentrated PAn/NMP solution was a physical crosslinking between PAn molecules with the help of NMP through hydrogen bonding. A gelatin mechanism was proposed.

Compatibility and specific interactions in poly(beta-hydroxybutyrate) and poly(p-vinylphenol) blends

The miscibility and specific interactions in poly (beta-hydroxybutyrate) (PHB)/poly(p-vinylphenol) (PVPh) blends were studied by differential scanning calorimetry(DSC) , fourier transform infrared(FTIR) spectrometer and high resolution solid state C-13 NMR, A single composition-dependent glass transition temperatures were obtained by DSC which indicate the blends of PHB/PVPh were miscible in the melt state, The experimental glass transition temperatures were fitted quite well with those obtained from Couchman-Karasz equation. The FTIR study shows that the strong intermolecular hydrogen bonding exists in blends of PHB with strong proton acceptor and PVPh with strong proton donor and is the origin of its compatibility. The CPMAS C-13 NMR spectra also show that the strong hydrogen bonding exists in PHB/PVPh blends. From the T-1 rho(H) relaxation time it follows that the blends of PHB/PVPh(40/60, 20/80) studied are completely homogeneous on the scale of about 3.2 nm.

Mass spectrometric evidence for the generation of benzyne from benzoyl peroxide in thermolysis

Benzoyl peroxide gave rise to benzoic acid (at m/z 122) in its electron impact mass spectrum, and its perdeuterated counterpart produced perdeuterobenzoic acid, C6D5CO2D, at m/z 128 under the same conditions, An intramolecular hydrogen abstraction is proposed for the formation of benzoic acid from the peroxide in thermolysis. As a result of this reaction, benzyne would be generated simultaneously. Anthracene was employed to trap any of the reactive intermediate benzyne. Collision-induced dissociation of the ion of m/z 254 from the mixture of benzoyl peroxide and anthracene indicated that triptycene was obtained by the trapping reaction, therefore confirming that benzyne is generated from benzoyl peroxide in thermolysis.

Miscibility and phase behavior in blends containing random copolymers of poly(ether ether ketone) and phenolphthalein poly(ether ether ketone)

The miscibility and phase behavior of polysulfone (PSF) and poly(hydroxyether of bisphenol A) (phenoxy) with a series of copoly(ether ether ketone) (COPEEK), a random copolymer of poly(ether ether ketone) (PEEK), and phenolphthalein poly(ether ether ketone) (PEK-C) was studied using differential scanning calorimetry. A COPEEK copolymer containing 6 mol % ether ether ketone (EEK) repeat units is miscible with PSF, whereas copolymers containing 12 mol % EEK and more are not. COPEEK copolymers containing 6 and 12 mol % EEK are completely miscible with phenoxy, but those containing 24 mol % EEK and more are immiscible with phenoxy. Moreover, a copolymer containing 17 mol % EEK is partially miscible with phenoxy; the blends show two transitions in the midcomposition region and single transitions at either extreme. Two T(g)s were observed for the 50/50 blend of phenoxy with the copolymer containing 17 mol % EEK, whereas a single composition-dependent T-g appeared for all the other compositions. An FTIR study revealed that there exist hydrogen-bonding interactions between phenoxy and the copolymers. The strengths of the hydrogen-bonding interactions in the blends of the COPEEK copolymers containing 6 and 12 mol % EEK are the same as that in the phenoxy/PEK-C blend. However, for the blends of copolymers containing 17, 24, and 28 mol % EEK, the hydrogen-bonding interactions become increasingly unfavorable and the self-association of the hydroxyl groups of phenoxy is preferable as the content of EEK units in the copolymer increases. The observed miscibility was interpreted qualitatively in terms of the mean-field approach. (C) 1996 John Wiley & Sons, Inc.

Synthesis and structure of 1:1 complex of ethylphenyltin dichloride with N-4-methoxyphenyl-2-hydroxynaphthylideneimine

A novel organotin complex, EtPhSnCl(2) . 2HOC(10)H(6)CH = NC6H1OCH3 was synthesized, and its crystal structure was determined by X-ray diffraction method. The crystal is triclinic, belonging to space group, with unit cell parameters a = 1.150 8(5) nm, b = 1. 153 1(5) gm, c = 1. 004 6 (3) nm, alpha = 94. 15 (3)degrees, beta = 115.47 (3)degrees, r = 85. 94 (4)degrees, V = 1199 7(1) nm(3), Z=2, D-c=1.68 g/cm(3), mu=13. 20 cm(-1), F(000)=618 for 4 131 reflections tions. R=0. 047, R(w)=0. 047. The ligand coordinates to tin atom via phenolic oxygen atom. The complex has a distored trigonal bipyramidal structure, the phenolic oxygen atom of the ligand and one of two chlorine atoms occupy the axial position. The distance between noncoodinated nitrogen atom with phenolic oxygen atom is 0. 257 4 nm, which indicates that the intramolecular hydrogen bond of Schiff base ligand is retained in the complex.

A STUDY ON POLYMER-POLYMER INTERACTIONS THROUGH MIXING CALORIMETRY

The aim of this work is to describe the most recent achievements in the field of the physical chemistry of mixing. The systems studied have been classified according to the amount of thermic effect due to the blending and its interpretation. When polystyrene (PS) and poly(alpha-methylstyrene) (P alpha MS) are blended, the interaction is weak and Delta(mix)H is close to zero. The presence of polar atoms and/or groups increases the stability of the blend and, therefore, Delta(mix)H becomes more negative. Poly(ethylene oxide) (PEO), poly(methyl acrylate) (PMA), poly(methyl methacrylate) (PMMA) and poly(vinylacetate) (PVAc), when mixed to form binary systems, show large differences from their properties when pure. If hydrogen bonding takes place, the interactions are readily detected and a large effect is calorimetrically determined. Cellulose diacetate (CDA) and poly(vinylpyrrolidone) (PVP) have been studied as an example of a strongly interacting system.

A HIGH-RESOLUTION SOLID-STATE NMR AND DSC STUDY OF MISCIBILITY AND CRYSTALLIZATION BEHAVIOR OF POLY(VINYL ALCOHOL)/POLY(N-VINYL-2-PYRROLIDONE) BLENDS

Blends of crystallizable poly(vinyl alcohol) (PVA) with poly(N-vinyl-2-pyrrolidone) (PVPy) were studied by C-13 cross-polarization/magic angle spinning (CP/MAS) n.m.r. and d.s.c. The C-13 CP/MAS spectra show that the blends were miscible on a molecular level over the whole composition range studied, and that the intramolecular hydrogen bonds of PVA were broken and intermolecular hydrogen bonds between PVA and PVPy formed when the two polymers were mixed. The results of a spin-lattice relaxation study indicate that blending of the two polymers reduced the average intermolecular distance and molecular motion of each component, even in the miscible amorphous phase, and that addition of PVPy into PVA has a definite effect on the crystallinity of PVA in the blends over the whole composition range, yet there is still detectable crystallinity even when the PVPy content is as high as 80 wt%. These results are consistent with those obtained from d.s.c. studies.

MISCIBILITY OF POLY(HYDROXYETHER OF PHENOLPHTHALEIN) WITH POLY(ETHER SULFONE)

Blends of poly(hydroxyether of phenolphthalein) (PHP) with poly(ether sulphone) (PES) were prepared by casting from a common solvent; they were found to be miscible and show a single, composition-dependent glass transition temperature. All the PHP/PES blends exhibited lower critical solution temperature behaviour, i.e. phase separation occurred at elevated temperatures. A F.T.-i.r. study revealed that a hydrogen-bonding interaction occurs between these polymers but it is weaker than in pure PHP. The observed miscibility is hence proposed to be the result of specific interactions between the polymers.

THERMAL-OXIDATION OF POLYPROPYLENE CONTAINING HINDERED PIPERIDINE COMPOUNDS

The thermal oxidation behaviour of polypropylene containing tetramethylpiperidine compounds and corresponding pentamethylpiperidine compounds are compared using air oven aging, oxygen uptake and thermogravimetry. Carbonyl formation, the induction period of oxygen absorption and weight loss have been selected to characterize the degree of oxidation. The results show that the stabilizing effectiveness of pentamethylpiperidines is always higher than that of tetramethyl types. Radical-trapping mechanisms cannot explain this, because large amounts of nitroxyl radicals are formed by the tetramethylpiperidine compounds. The quenching of singlet oxygen appears to be involved in thermal oxidation of polypropylene containing pentamethylpiperidine compounds. Specific hydrogen bonding between pentamethylpiperidines and hydroperoxide may account for their better thermal stabilizing action than tetramethylpiperidines.

4-(2-fluorobenzylideneamino)-3-(1,2,4-triazol-4-ylmethyl)-1H-1,2,4-triazole-5(4H)-thione

In the title compound, C12H10FN7S, the dihedral angles made by the plane of the thione-substituted triazole ring with the planes of the other triazole ring and the benzene ring are 74.55 (2) and 11.50 (3)degrees, respectively. The structure shows a number of N - H center dot center dot center dot N intermolecular hydrogen-bonding interactions, and weak C - H center dot center dot center dot S intra- and intermolecular interactions.