Two-photon fluorescence microscopy has been used to interrogate the interior functionality of polymer resin beads. By employing this technique, the spatial distribution of the initial functionality contained within the polymer matrix has been determined. Spatially resolved, concentric shells were then produced synthetically in these polymer spheres via a series of protection/deprotection reactions in which two-photon fluorescence microscopy was employed to monitor each successive step. To demonstrate the potential utility of these techniques in combinatorial screening, a set of beads was prepared containing a unique tripeptide sequence in each of the three concentric shells within each individual bead. The set was then screened for the binding affinity of each tripeptide toward a fluorescent ligand.
The self-association of the tranquilizer chlorpromazine hydrochloride in aqueous solution was studied. Using isothermal titration calorimetry, the critical micelle concentration and solvent-micelle interactions were evaluated as a function of temperature, ionic strength, and pH. The enthalpy of demicellization, ∆Hdemic, was directly measured from the experimental enthalpy values, which showed that the spontaneous demicellization of chlorpromazine hydrochloride is a highly endothermic process under all experimental conditions studied. The thermodynamic parameters were subsequently calculated from the temperature dependent thermograms. At 25 °C, the critical micelle concentration was determined to be 3.2 mM at pH 6.5 with a ∆Hdemic of 12.5 kJ/mol, a ∆Gdemic of 24.3 kJ/mol, and a T∆Sdemic of -10.1 kJ/mol. Our results suggest that the enthalpy-entropy compensation theory may be applied to these micelles. In addition, using differential scanning calorimetry, a broad endothermic demicellization peak was observed in postmicelle solutions during heating scans at approximately 45 °C. Cooling scans revealed a very broad peak centered around 40 °C that corresponds to the heat of micellization.
Environmental issues and recent developments in chemistry and biology have introduced a number of compelling requirements that must be met in the development of practical catalysts. Recyclability is one important attribute. Retrievable catalysts that are recovered inexpensively and without significant waste generation efficiently deliver products of higher purity and lower toxicity. The emerging significance of combinatorial chemistry demands that a catalyst promote reactions efficiently and selectively while being easily adaptable to 96-well and higher density formats; repeated weighing of catalysts or substrates for a library synthesis and subsequent purification of each mixture is costly and time-consuming.Herein we disclose the synthesis and activity of Ru complexes supported by monolithic (smallest dimension 1 mm) samples of porous sol ± gel glass that effectively promote various olefin metathesis reactions. [1] These catalysts can be easily employed in a library synthesis format without multiple weighings, in air and with undistilled commercial reagent-grade solvents. Catalyst recovery is simply carried out with a pair of tweezers; it does not require filtration and generates minimal solvent waste. The catalyst retains its activity after multiple cycles (b 15), affording products that are of high (often analytical) purity without recourse to any purification steps.Recent reports from our laboratories relate to the chemistry of recyclable monomeric metathesis catalysts (1 and 2). [2] A key feature of these systems is the isopropyl styrenyl ether; this bidentate ligand favors efficient metal recovery for entropic reasons, allowing the promotion of olefin metathesis by a release/return mechanism. [2] These Ru complexes can also offer reactivity and chemo-and stereoselectivity profiles [3] which differ from the alternative catalysts 3, [4] 4, [5] and 5. [6] Although 1 and 2 are robust and recyclable, catalyst retrieval generates substantial amounts of silica gel and solvent waste. Based on the release/return mechanism, Ru ± carbenes 1, [7] 3, [8] and 5 [9] were subsequently attached to insoluble cross-linked and monoporous polystyrene polymers as well as to a soluble polyethylene glycol (PEG) resin. However, these supported catalysts typically suffer from one or more of the following shortcomings: 1) There are no reports of catalyst utility in the synthesis of trisubstituted olefins; efficient processes involve only ring-closing metathesis (RCM) reactions with terminal olefin substrates or those that benefit from entropic factors. [7±9a] 2) Diminished [5] E. A. Permyakov, L.
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