Solvent-dependent formation of di- and trinuclear rhodiurn and iridium complexes bridged by N,N '-donor ligands

Reactions of Rh and Ir hydrido complexes. [Rh(H)(2)(PPh3)(2)(solv)(EtOH)]ClO4 (solv = Me2CO, 1a; EtOH, 1b) and [Ir(H)(2)(PPh3)(2)(Me2CO)(2)]BF4 (2), with various N,N'-donor bridging ligands, such as pyrazine (pyz), 4,4'-trimethylenedipyridine (tmdp) and di(4-pyridyl) disulfide (dpds), in some solvents were examined, and their reaction products were characterized by X-ray crystal structure analysis. IR, H-1 NMR and UV-vis spectra. Rh hydrido complexes, la or 1b, formed a dinuclear Rh complex, [Rh-2(PPh3)(2) {(eta(6)-C6H5PPh2}(2)] (ClO4)(2).6CH(2)Cl(2) (3.6CH(2)Cl(2)), in dichloromethane with a reductive elimination of hydrogen. The reactions of 1a or 1b with the pyz ligand in dichloromethane and tetrahydrofuran gave triangular Rh-3 complexes, [Rh-3(PPh3)(6)(pyz)(3)](ClO4)(3).CH2Cl2 (5.CH2Cl2) and [Rh-3(PPh3)(6)(pyz)(3)](ClO4)(3).EtOH (5.EtOH), respectively, in contrast to the formation of a dinuclear Rh hydrido complex, [Rh-2(H)(4)(PPh3)(4)(Me2CO)(2)(pyz)](ClO4)(2).EtOH A-EtOH). in acetone. The reactions of la or 1b with the tmdp ligand in dichloromethane and 3-methyl-2-butanone also afforded dinuclear Rh complexes, [Rh-2(PPh3)(4)(tmdp)(2)](ClO4)(2) (6) and [Rh-2(PPh3)(4)(tmdp)(2)](ClO4)(2).4MeCOCHMe(2) (6.4MeCOCHMe(2)), respectively. On the other hand, Ir hydrido complex 2 reacted with pyz and dpds ligands in dichloromethane to afford dinuclear Ir complexes, [Ir-2(H)(4)(PPh3)(4)(Me2CO)(2)(pyz)]- (BF4)(2).3CH(2)Cl(2) (7.3CH(2)Cl(2)) and [Ir-2(H)(4)(PPh3)(4)(dpds)(2)](BF4)(2).3CH(2)Cl(2).H2O (8.3CH(2)Cl(2).H2O), respectively, without any reductive elimination of hydrogen. Based on structural studies in solution and in the solid state. it was demonstrated that various Rh and Ir complexes were selectively produced depending on the choice of solvents and N,N'-donor bridging ligands.

Design, synthesis and characterization of novel nitrogen-and sulfur-containing polymers with well-defined conjugated length

A series of novel nitrogen- and sulfur-containing conjugated polymers with well-defined conjugation length have been synthesized via an acid-induced self-polycondensation of functional monomers with methylsulfinyl groups. Synthesized polymers exhibit good solubility in common solvents, such as CHCl3, THF, DMF, DMSO, and NMP. With increased numbers of aminophenyl groups, these polymers have shown similar electrical properties to polyaniline (PAn), and these are demonstrated by UV-vis spectroscopy and cyclic voltammetry (CV) measurements on the polymers. The conductivity of preliminarily protonic-doped poly[phenylene sulfide-alt-tetrakis(aniline)] (PPSTEA) is up to 10(-1) S cm(-1).

Nitrogen- and sulfur-containing conjugated polymers as the hole-transporting materials

A series of novel nitrogen- and sulfur-containing conjugated polymers have been synthesized via an acid-induced self polycondensation of functional monomers with methyl sulfinyl group. They exhibit good solubility in common solvents, such as CHCl3, THF, DMF, DMSO, et al; and thus show excellent film-forming properties. They are used as hole-transport layer (HTL) in two-layer light-emitting diodes (ITO/polymer/Alq3/Mg:Ag). The typical turn-on voltage of these diodes is about 4 similar to 5V. The maximum brightness is about 3440cd/m(2) at 20 V. The maximum efficiency is estimated to be 0.15 Im/W at 10V.

Synthesis and characterization of side chain liquid crystal M5MPP/MMEANB copolymers containing NLO active group

A new series of side chain liquid crystal polymers based on the backbone of polymethacrylate containing 4-nitroazobenzene and 4-methoxybiphenyl group as side chain mesogen were prepared and characterized, FTIR, H-1 NMR, POM and WAXD were used to study the structure, phase behavior and mesophase texture of this series of SCLC copolymers. The researches show that polymer PM5MPP and copolymer M5MPP/MMEANB are enantiotropic liquid crystalline polymers, but polymer PMMEANB has no liquid crystalline properties. DSC results showed that the thermal stability of the mesophase of this series of copolymers was enhanced by the existence of intermolecular electron donor-acceptor interaction. It was found that the temperature range of the mesophase of the copolymers was broadened with increasing 4-nitroazobenzene units. The focal-conic texture observed by POM indicated that this series of the copolymers possessed the characteristics of smectic liquid crystal.

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.

Luminescence properties of rare earth (Eu3+ and Tb3+) complexes with conjugated carboxylic acids and 1,10-phenanthroline incorporated in silica matrix

Binary and ternary complexes of europium and terbium with conjugated carboxylic acid (nicotinic acid and 3,4-furandicarboxylic acid) and 1,10-phenanthroline were introduced into silica gel by the sol-gel method. The luminescence behavior of the complexes in silica gels was studied compared with the corresponding solid state complexes by means of emission, excitation spectra and lifetimes. The result indicated that the rare earth ions (EU3+ and Tb3+) showed fewer emission lines and slightly lower emission intensities in the silica gel than those in pure rare earth complexes. The lifetimes of rare earth ions (EU3+ and Tb3+) in silica gel doped with rare earth complexes became longer than those in pure rare earth complexes. (C) 1998 Elsevier Science S.A.

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.

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.