Fluorescence and aggregation behavior of a polyimide in solutions

The UV-visible absorption and fluorescence spectra of a soluble polyimide, YS-30, in several organic solvents were measured over a wide range of concentration. The experimental results show that there exist both intramolecular and intermolecular electron donor acceptor interactions for YS-30 molecules. The fluorescence behavior of YS-30 in N,N-dimethylacetamide and in chloroform solutions is similar in general, except that its ground-state intermolecular charge transfer emission is more obvious in N,N-dimethylacetamide solution. This difference is attributed to the greater extent of disruption of the chain packing by solvent or/and the more efficient radiationless energy dissipation process from the excited state complexes to chloroform. The intensity ratio of intermolecular charge transfer emission to intramolecular charge transfer emission is used to characterize the state of aggregation of YS-30 molecules in solutions. The plot of this ratio versus concentration indicates the existence of two critical concentrations. It is also found from the same plot that the decrease of coil size is very pronounced during the initial stage of shrinkage.

Study of photochemical fluorescence enhancement of the terbium-lomefloxacin complex

Lomefloxacin (LMFX) and terbium ion can form a complex and the sensitized fluorescence of the terbium ion can be observed. It was found that the sensitized fluorescence intensity can be notably enhanced when the terbium complex is exposed to 365 nm ultraviolet light. By the fluorescence spectra, phosphorescence spectra, fluorescence quantum yield and fluorescence lifetime of the system, it was proved that irradiation of the complex made it undergo a photochemical reaction and a new terbium complex which is more favorable to intramolecular energy transfer was formed. This is why the sensitized fluorescence enhancement can be observed. (C) 1999 Elsevier Science S.A. All rights reserved.

Synthesis, crystal structure and properties of (Z)-3-triphenylstannyl-1,1-diphenyl propenol

Five new organotin compounds were synthesized and characterized, X-ray crystal structure analysis of (Z)-3-triphenylstannyl-1,1-diphenyl propenol was performed, The crystal belongs to space group P2(1)/n. The cell parameters are: a = 1.235 7(2) nm, b = 0.987 4(2) nm, c = 2.208 1(4) nm, beta = 95.23(3)degrees, V = 2.683 0(9) nm(3), Z = 4, R = 0.027 9, R-w = 0.064 5. The tin atom of the molecule exists in a distorted tetrahedron, Z isomer of double bond is obtained.

The synthesis, characterization and photophysical properties of binary and ternary rare earth complexes with N-phenylanthranilic acid and l,l0-phenanthroline

Some novel binary and ternary complexes of rare earth(Gd, Eu,Tb) with N-Phenylanthranilic acid and 1,10-Phenanthroline were synthesized by homogenous precipitation and their compositions were characterized by,elemental analysis, IR spectra and UV-Vis spectra, The triplet state energies of N-Phenylanthranilic acid was determined to be 24 330 cm(-1) with the phosphorescence spectra of its gadolinium complexes and the energy match between the ligand and the central rare earth ions was studied. The photophysical properties such as luminescence properties and intramolecular energy transfer match between rare earth ions and ligands and between ligands were discussed. The result indicates that terbium complexes with N-Phenylanthranilic acid and 1,10-Phenanthroline have excellent luminescence properties.

Synthesis, characterization, and photophysical properties of rare earth complexes of N-phenyl-2-aminobenzoic acid and 1,10-phenanthroline

Some novel binary and ternary complexes of rare earth ions (Gd, Eu, Tb) with N-phenyl-2-aminobenzoic acid and 1,10-phenanthroline were synthesized by homogenous precipitation and characterized by elemental analysis, IR spectra, UV/Vis spectra, and thermal analysis. The phosphorescence spectra and lifetimes of gadolinium complexes were measured, and the triplet state energies of N-phenyl-2-aminobenzoic acid and 1,10-phenanthroline as well as the energy transfer efficiencies between N-phenyl-2-aminobenzoic acid and 1,10-phenanthroline were determined. The photophysical properties such as luminescence and intramolecular energy transfer between the rare earth center ions and the ligands and between ligands are discussed.

Spectroscopic study of luminescence and energy transfer of binary and ternary complexes of rare earth with aromatic carboxylic acids and 1,10-phenanthroline

A series of rare earth (Gd, Eu, Tb) complexes with different substituent group carboxylic acids (ortho-hydroxylbenzioc acid, ortho-aminobenzoic acid and ortho-methoxy benzoic acid) and 1,10-phenanthroline were synthesized. The spectroscopic studies of the photophysical properties such as luminescence properties, energy match and intramolecular energy transfer were carried out. The lowest triplet state energies of ligands and the intramolecular energy transfer efficiencies were determined with the measurement of low phosphorescence spectra and lifetimes of Gd complexes.

Photophysical properties of some binary and ternary complexes of rare earth ions with aminobenzoic acids and 1,10-phenanthroline

Photophysical properties (e.g. luminescence and energy transfer) of binary and ternary complexes of Gd3+, Eu3+, and Tb3+ with aminobenzoic acids and 1,10-phenanthroline were studied in connection with their spectroscopic characterization. Intramolecular energy transfer between center ions and ligands as well as between ligands is discussed in detail.

Synthesis, structure characterization and transesterification of the complexes of beta-alkoxycarbonylethyltin trichlorides

Thirteen title complexes ROCOCH2CH2SnCl3 . L(R = C(1 similar to 5)alkyl;L = DBSO,HMPA) were synthesized and characterized by elemental analysis, IR,H-1 NMR. The crystal structure of n -PrOCOCH2CH2SnCl3 . DBSO was determined by the X-ray diffraction analysis. The crystal belongs to orthorhombic system,space group P2(1)2(1)2(1) with a = 1.062, b = 1.427, c = 1.635nm; Z = 4. The complex exists as a discrete molecule, and the tin atom attains a distorted octahedral geometry via the coordination of intramolecular carbonyl oxygen and the Lewis base donor atom. The transesterification of CH3OCOCH2CH2SnCl3 . L with alcohol was studied, and the intramolecular Lewis acid catalytic mechanism was suggested.

Synthesis, luminescence properties and energy transfer of binary and ternary rare earth complexes with aromatic acids and 1,10-phenanthroline

A series of binary and ternary rare earth (Gd, Eu, Tb) complexes with ortho hydroxyl benzoic acid, pam aminobenzoic acid, nicotinic acid and 1,10-phenanthroline were synthesized. Phosphorescence spectra and lifetimes of Gd complexes were measured and the lowest triplet state energies of gadolinium binary complexes end the intramolecular energy transfer efficiencies were determined. The luminescence properties and energy transfer process of Eu3+ and Tb3+ complexes were discussed.

The photophysical properties of binary and ternary complexes of rare earths with conjugated carboxylic acids and 1,10-phenanthroline

Results of photophysical properties of the complexes of Gd3+, Eu3+ and Tb3+ with conjugated carboxylic acids (3,4-funandicarboxylic acid and nicotinic acid) and 1,10-phenanthroline are reported. Whether between central ions and ligands or between the two ligands, it is found that the intramolecular energy efficiency is a sensitive function of the relative positions of the resonance energy levels of the central ions and the lowest triplet states of the ligands. Couplings of rare earth ions to the ligands are discussed in detail. (C) 1997 Elsevier Science S.A.

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.

The synthesis, luminescence and energy transfer of the binary and ternary complexes of rare earth with aminobenzoic acids and 1,10-phenanthroline

Thirteen kinds of binary and ternary complexes of rare earth (Gd, Eu,Tb) with ortho (para) aminobenzoic acid and 1.10--phenanthroline were synthesized and characterized. The phosphorescence spectra and lifetimes of gadolinium complexes were measured and the lowest triplet state energies of ligands and the energy transfer efficiencies between ligands were determined. The luminescence properties and intramolecular energy transfer of these complexes were studied in details.

The miscibility of homopolymer random copolymer blends .1. Poly(styrene-co-acrylonitrile) poly(ethyl methacrylate) and poly(styrene-co-acrylonitrile) poly(methyl methacrylate) blends

The miscibility of blends of poly(styrene-co-acrylonitrile) (SAN) with poly(methyl methacrylate) (PMMA) or poly(ethyl methacrylate) (PEMA) has been investigated by means of NMR and DSC techniques. It is found that there are intermolecular interactions between the phenyl groups in SAN and carbonyl groups in PMMA or PEMA, and the strength of this intermolecular interaction strongly depends on the properties of ester side groups in PEMA or PMMA, composition of the blends and a certain composition of the copolymer. It is this specific interaction instead of the intramolecular repulsion force within the copolymer that plays a key role for the miscibility of SAN/PMMA and SAN/PEMA blends.

Synthesis and characterization of aromatic liquid crystalline poly(ester-imide)s derived from an imidodicarboxylic acid

A new class of liquid crystalline poly(ester-imide)s was synthesized by melt polycondensation. The basic physical properties of the resulting polymers were investigated by differential scanning calorimetry (d.s.c.), wide-angle X-ray diffraction (WAXD), polarized light microscopy, scanning electron microscopy (SEM), thermogravimetric analysis (t.g.a.), and rheological and mechanical testing. All of these poly(ester-imide)s were amorphous, as reflected by the results obtained from the WAXD and d.s.c. studies. Characterization and comparison of these poly(ester-imide)s with the corresponding polyesters suggested that the introduction of imide groups into the polyester chain is favourable for the formation of liquid crystalline phases. These results, together with the rheological studies, suggested that there existed a form of strong inter- or intramolecular electron donor-acceptor interaction which played a significant role in the liquid crystalline properties of the poly(ester-imide)s. The polymer products thus obtained exhibited good mechanical properties, with flexural strengths and moduli as high as 174 MPa and 6.9 GPa, respectively. The morphology of the fracture surfaces of extruded rod samples showed a sheet-like structure which consisted of ribbons and fibres oriented along the flow direction. The glass transition temperatures and thermal stabilities of the polymers were improved by the incorporation of imide groups. Copyright (C) 1996 Elsevier Science Ltd.

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.