JaimeLee Iolani Cohen

Preparation and investigation of antibacterial carbohydrate-based surfaces.

Surfaces bearing carbohydrate units have been modified in a two-step process to incorporate functionalities (lipophilic with polycationic units) that bear antibacterial activity. The effectiveness of these modified surfaces for antibacterial action against a series of seven Gram-positive and Gram-negative bacteria are reported.

Polycations. IX. Polyammonium derivatives of cyclodextrins: syntheses and binding to organic oxyanions

A series of polycationic derivatives of α- and β-cyclodextrin have been synthesized. Their interactions for inclusive binding of series of organic phosphorus oxyanions and anions of biological α-amino acids have been investigated using NMR techniques. Determinations of association constants and orientation of guest anion binding to the host polycationic cyclodextrin derivatives have been performed.

Polycations. 4. Synthesis and antihydrophobic effect of polycationic strings

Two categories of polycationic “strings” have been synthesized and investigated for their effect on the aqueous solubility of hydrophobic organic compounds (benzene and 4-bromotoluene, the latter discussed here). Polycationic “strings” are compounds in which cationic sites (quaternary ammonium sites) are incorporated into the covalent structure along a linear chain with free-floating associated anions. The categories are: 1) defined length chains consisting of quaternized dabco units connected by intervening lengths of methylene groups, terminating with ω-alkanol units, and 2) α,ω-dimethylaminoalkane units quaternized with chain extending ω-alkanol units. The observed antihydrophobic effect depends on the total charge, the length of the charge-intervening linkages, and the terminating groups.

A New Category of Liquid Salt--Liquid Ionic Phosphates (LIPs)

Starting with polycationic ammonium and phosphonium salts bearing halide anions previously synthesized in our laboratory, we have prepared a new category of nonaqueous ionic liquids. These new nonaqueous ionic liquids bear either free phosphate anions or partially esterified phosphate anions as the counterions to the ammonium or phosphonium cations. We generally refer to these new species as LIPs (liquid ionic phosphates). We have developed three approaches toward the syntheses of these materials from the halide salts: one using hexafluorophosphoric acid;; a classical ion exchange method; and treatment with the free phosphorus-containing acid under vacuum. The new LIPs, although highly viscous, exhibit significantly high specific conductivities. Unlike ionic liquids bearing tetrafluoroborate of tetrachloroaluminate anions, the LIPs are unreactive toward water. Further, the LIPs bearing simple phosphate anions are soluble in water, unlike their corresponding hexafluorophosphate salts. We have also examined the UV/Vis, fluorescence, and mobility characteristics of the new LIPs.

Polycations. 7. Polycationic Cyclic Alkynes

Abstract A facile synthesis of polycationic heterocyclic alkynes of intermediate ring size is reported. With judicious choice of the solvent system, α,ω-di(tertiary)amines react readily with 1,4–dichloro-2-butyne to generate these intriguing species in good yield.

Lips-syntheses of phosphonium and ammonium liquid ionic phosphates

Using parent polycationic halide salts previously prepared by our laboratory, replacement of the anion to one that would allow the salt to be liquid at room temperature in the absence of water or other solvent medium was performed. Treatment of the polyammonium halides with aqueous hexafluorophosphoric acid resulted in the immediate formation of a solid material insoluble in water for which the 1H and 13C NMR spectra corresponded to those of the original halide salts. However, the 31P NMR spectra indicated these to be mixtures of the (anticipated) hexafluorophosphate salt and simple phosphate salt. Evaporation of the remaining aqueous solution resulted in isolation of the pure phosphate salts as room temperature liquids–liquid ionic phosphates (LIPs) which exhibited water solubility and NMR spectra (1H, 13C, and 31P) in total accord with the proposed structures. These represent a new category of nonaqueous ionic liquid which are water soluble and water unreactive. (The polycationic hexafluorophosphate salts could be purified by repeated washing with water and drying under high vacuum. These materials have not been investigated further in the present work.) As this approach for the preparation of LIPs results in the formation of a significant amount of the water insoluble hexafluorophosphate species, as well as uses a highly corrosive and toxic reagent system, an alternative method for the preparation of LIPs was sought. Two alternative approaches toward the preparation of these polycationic phosphates have been developed. Treatment of the parent halide salts