Trimers solvent effects

Trace B shows the emission spectrum obtained from a sample of crystals of AuVMeN = COMe)3 after pulsed irradiation, while Trace C shows the spectrum of the light emitted immediately after the addition of chloroform to a previously photo-irradiated sample of Au lMeN = COMe)3 crystals. The spectrum shown in Trace C is that from solvoluminescence. Notice that the emitted light corresponds to the lower energy emission seen for the solid and does not correspond to that seen in solutions of the trimer. Similar emission spectra have been obtained with a number of different solvents including dichloromethane, toluene, methanol, hexane, and even water. In all cases the spectra of the emissions show a maximum at 550 nm. Thus, there is no solvent effect on the emission. However, the intensity of the emission is greatest with those liquids (chloroform, dichloromethane) that are good solvents for the complex and rather feeble in those that are not (hexane, water). 

A cap molecule of suitable size and symmetry could effectively close off the interior of trimer 7 to create a very large molecular container. Such a feat has recently been accomplished in our laboratories, where trimer carceplex 9 -3 DMF was synthesized in 37% yield, by reaction of trimer 7 with 2,4,6-tris(bromomethyl)mesitylene under basic conditions (Scheme 4-4) [21]. No empty trimer carcerand has yet been isolated, which implies that a template (or templates) is required for formation. Can a large single template molecule form trimer carceplex 9-guest We are currently investigating this possibility. Such an investigation begs the question when does a template effect become a solvent effect ... 

The influence of the central metal ion on the TPA properties—as well as on the second-order NLO response—of push-pull porphyrins has been investigated by Ray et alP by employing the ZINDO/Correction Vector (ZINDO/CV) method combined with the Onsager Self-Consistent Reaction Field (SCRF) method to account for solvent effects. Metalloporphyrins with strong CT bands are shown to exhibit an increase of both NLO responses by one order of magnitude with respect to the porphyrin without metal. These NLO responses further increase by at least one or two orders of magnitude when going from the monomer to the dimer and trimer. 

Commercial polystyrenes are normally rather pure polymers. The amount of styrene, ethylbenzene, styrene dimers and trimers, and other hydrocarbons is minimized by effective devolatilization or by the use of chemical initiators (33). Polystyrenes with low overall volatiles content have relatively high heat-deformation temperatures. The very low content of monomer and other solvents, eg, ethylbenzene, in PS is desirable in the packaging of food. The negligible level of extraction of organic materials from PS is of cmcial importance in this appHcation. 

Freitag and John [96] studied rapid separation of stabilisers from plastics. Fairly quantitative extraction (>90% of the expected content) of stabilisers from a powdered polymer was achieved by MAE within 3 to 6 min, as compared to 16 h of Soxhlet extraction for the same recovery. MAE and Soxhlet extraction have also been compared in the analysis of cyclic trimer in PET [113]. On the other hand, Ganzler et al. [128] compared the extraction yields for various types of compounds from nonpolymeric matrices for microwave irradiation with those obtained by the traditional Soxhlet or shake-flask extraction methods. Microwave extraction was more effective than the conventional methods, in particular in the case of polar compounds. As expected, the efficiency of the former is high especially when the extraction solvents contain water. With the high dipole moment of water, microwave heating is more... 

The free a-amino groups of the ornithine units were also found in an acetylated form 90, 243). Since triacetylfusigen is resistant to hydrolysis, formation of the acetylated mono-, di-, and trimeric linear acetylfusarinines is assumed to be effected by enzymatic cleavage 103a, 243). X-ray and CD data of the Fe " complex of triacetylfusigen have been obtained 152). Depending on the solvent used for crystallization the crystals show A-cis or A-cis configuration, while in solution A-cis prevails. 

The principal tumor-localizing component of Hematoporphyrin Derivative (HPD) has been demonstrated to be dimeric and trimeric hematoporphyrins (HP) interconnected with ester groups. Synthetic analogs as well as model compounds are used in our study to conclude that the reaction conditions employed in the traditional HPD preparation promote a nucleophilic substitution of the acetate group of one HP-acetate molecule by an propionate anion of another HP molecule. The effect of solvent on the stability and structural conformation of the diporphyrin esters have also been examined by spectroscopic methods. 

The effect of relative permitivity D on the cyclo-trimerization of phenyl isocyanate was studied in the solvent system acetonitrile (AN) - ethylacetate (EA) using cyclic sulfonium zwitterion VI as catalyst. It was found that the rate constant increased with the increase of relative permitivity D of the solvent system, the experimental data correlate well with the Kirkwood equation ... 

Very few studies on uncompleted, lithium amides have been carried out in solution, e.g., in hydrocarbon solvents. Only five oligomeric, ligand-free compounds of this type have been characterized structurally f (54)—(58) Table VI Section III,B,1]. Studies carried out on solutions in polar solvents would, in effect, involve complexes. For example, the unsolvated crystalline trimers (55) and (56) both form dimeric etherate complexes (19, 20, 76, 81). Solution studies of com-plexed lithium amides will be described in Section III,C,3. 

Water and methanol can form strong hydrogen bonds in solutions. These kinds of solvent-solvent interactions have a pronounced effect in the NIR spectral region. For example, in pure methanol solutions it is possible to have dimers, trimers, and other intermolecular hydrogen-bonded species in equilibrium. Equilibrium concentrations of these species are very sensitive to impurity concentrations and temperature changes. 

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