Solid state aggregates

In atomic spectrometry, the sample is introduced, by means of a sampling device, into a high-temperature source or atom cell (plasma, flame, etc.). Here, the sample is vaporized, e.g., by thermal evaporation or sputtering. It is important to supply as much energy as possible, so that the volatilization processes, which involve a physical or chemical equilibrium, result in complete atomization, irrespective of the state of aggregation, solid state structure, or chemical composition of the sample. This is very important, both to ensure maximum sensitivity and to minimize matrix interference in the analysis. The effectiveness of the volatilization processes involved, the plasma temperature, and the number densities of the various plasma components will all influence sample atomization. 

The delicate balance between ionic and covalent forms is influenced not only by the state of aggregation (solid, liquid, gas) or the nature of the solvent, but also by the effect of substituents. Thus PhPCl4 is molecular with Ph equatorial whereas the corresponding methyl derivative is ionic, [MePClsl+Cl". Despite this the [PhPCl3]+... 

In the following section, step by step a qualitative picture is formed describing the impact of intcrmolecular interactions oil the absorption and luminescence of organic conjugated chains. The present calculations do not distinguish between dimers and aggregates (for which the wavefunctions of adjacent chains interact in the ground state, due to, for instance, solid-state effects) and excimers (where overlap occurs only upon photoexcitation) [29]. 

The solid-state structures of several benzylic carbanion salts have been elucidated by X-ray analysis9 depending on the nature of the benzylic part, the cation, and the additives, the structures range from er-bonded organometallic compounds to delocalized ion pairs, from monomeric to dimeric and polymeric aggregates. Some compounds are listed together with leading references ... 

A main problem concerning the solid state electronic properties of PPPs is its tendency to form aggregates. One synthetic strategy for overcoming this problem is the transition from linear, one-dimensional systems to branched or dendritic, two-dimensional ones. 

Molecular solids are aggregates of molecules bound together by intermolecular forces. Substances that are gases under normal conditions form molecular solids when they condense at low temperature. Many larger molecules have sufficient dispersion forces to exist as solids at room temperature. One example is naphthalene (Cio Hg), a white solid that melts at 80 °C. Naphthalene has a planar structure like that of benzene (see Section 10-), with a cloud of ten delocalized n electrons that lie above and below the molecular plane. Naphthalene molecules are held in the solid state by strong dispersion forces among these highly polarizable n electrons. The molecules in... 

Humphrey, S.M., Mack, H.-G., Redshaw, C., Elsegood, M.R.J., Yormg, K.J.H., Mayerand, H.A. and Kaskad, W.C. (2005) Variable solid state aggregations in a series of (isocyanide)gold(I) halides with the novel trimethylamine-isocyanoborane adduct. Dalton Transactions, (3),... 

The recent interest in substituted silane polymers has resulted in a number of theoretical (15-19) and spectroscopic (19-21) studies. Most of the theoretical studies have assumed an all-trans planar zig-zag backbone conformation for computational simplicity. However, early PES studies of a number of short chain silicon catenates strongly suggested that the electronic properties may also depend on the conformation of the silicon backbone (22). This was recently confirmed by spectroscopic studies of poly(di-n-hexylsilane) in the solid state (23-26). Complementary studies in solution have suggested that conformational changes in the polysilane backbone may also be responsible for the unusual thermochromic behavior of many derivatives (27,28). In order to avoid the additional complexities associated with this thermochromism and possible aggregation effects at low temperatures, we have limited this report to polymer solutions at room temperature. 

Selective derivatization of parent TACN427 and particularly syntheses of a large number of linked-TACN428,429 resulted in the isolation of interesting complexes (527) (the solid-state structure of this complex also contains an aggregate of [Na(BF4)2] units which form a polymeric... 

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