Complex formation stabilization luminescent

In this work, we have chosen several systems stabilized through hydrogen bonds. The homopolymer is a polybase, i.e. PEO, PVME or PVP, and the copolymer is polyacrylic acid with various degrees of neutralization a, in which the acrylates are the non active groups. Complex formation is studied by potentiometry (because complexation induces a variation of the solution pH) and by viscometry and polarized luminescence which respectively give information about the macroscopic and local structure of the complex in solution. The influence of parameters such as the degree of neutralization of PAA a, the concentration ratio r - [polybase]/[PAA], the concentration and the molecular weight of polymers is examined. 

Our motivation for offering a further consideration of excimer fluorescence is that it is a significant feature of the luminescence behavior of virtually all aryl vinyl polymers. Although early research was almost entirely devoted to understanding the intrinsic properties of the excimer complex, more recent efforts have been directed at application of the phenomenon to solution of problems in polymer physics and chemistry. Thus, it seems an appropriate time to evaluate existing information about the photophysical processes and structural considerations which may influence excimer formation and stability. This should help clarify both the power and limitations of the excimer as a molecular probe of polymer structure and dynamics. 

Interaction of the nitrate ion with lanthanide(III) in acetonitrile solution was studied by conductivity, vibrational spectroscopy and luminescence spectroscopy. Bidentate nitrate with approximate C2V local symmetry was detected. FT-IR spectral evidence for the formation of [La(N03)5]2, where La = Nd, Eu, Tb and Er with coordination number 9.9 has been obtained [128]. Two inequivalent nitrate ions bound to lanthanides were detected by vibrational spectroscopy. The inequivalent nature varied with different lanthanides. For example three equivalent nitrate groups for La and Yb, one nitrate different from the other two for Eu ion were detected. Vibrational spectral data point towards strong La-NC>3 interaction in acetonitrile [129]. Stability constants for lanthanide nitrate complexes are given in Table 4.10. 

Components of fluidized cracking catalysts (FCC), such as an aluminosilicate gel and a rare-earth (RE) exchanged zeolite Y, have been contaminated with vanadyl naphthenate and the V thus deposited passivated with organotin complexes. Luminescence, electron paramagnetic resonance (EPR) and Mossbauer spectroscopy have been used to monitor V-support interactions. Luminescence results have indicated that the naphthenate decomposes during calcination in air with generation of (V 0)+i ions. After steam-aging, V Og and REVO- formation occurred. In the presence of Sn, Tormation Of vanadium-tin oxide species enhance the zeolite stability in the presence of V-contaminants. 

The successful application of Ir(ppy)3 as a phosphorescent dopant has led to a number of synthetic modifications of the parent complex. Most of the new derivatives were prepared in order to alter the luminescent properties (color, efficiency, stability, etc.) or to further characterize the excited-state properties of these materials. Tris-cyclometal-lated Ir complexes can be prepared using two general methods, either by direct formation in a one-step reaction or with a two-step synthesis that uses a /t-dichloro-bridged dimeric complex as an isolated intermediate. The first efficient direct synthesis to be reported involved the reaction of Ir(acac)3 (acac = acetylacetonate) with an excess of... 

When the reduction process is performed in aqueous (1.5%) acetonitrile, reduction of the quinone units is followed by protonation with formation of the corresponding hydroquinone. Protonation of the reduced species amounts to its stabilization. The oxidation peak of the hydroquinone moiety is in fact at --+0.96 V under the above conditions. Therefore, electron-transfer quenching from the hydroquinone to the excited complex is endergonic (AG-0.2 V) and its rate cannot compete with the luminescence decay of the excited state (Fig. 13). 

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