|Ph.D Student||Slman Husein|
|Subject||Design, Preparation and Characterization of New Receptors|
and Detectors for Anions and Cations
|Department||Department of Chemistry||Supervisors||Professor Emeritus Shammai Speiser|
|Professor Yoav Eichen|
|Full Thesis text - in Hebrew|
The mimicry of natural recognition processes is one of the challenging research topics of supramolecular chemistry. The development of new receptors capable of recognizing neutral and charged species has attracted considerable interest in the recent past. Water-soluble anions such as fluoride, chloride, iodide, phosphate, and carboxylate are essential to life as many biological processes depend on the presence or transport of this anions, or use anions to carry out chemical transformations. They are also important for many industrial processes and are often found as harmful pollutants.
A very elegant way that was developed for reporting the presence of cations is the Photo-induced Energy Transfer (PET) signaling approach. PET chemosensors consist of a luminescent species attached to a receptor. Upon binding, the efficiency of the photo-induced energy transfer is changed and therefore there is an observable change in the photophysical properties of the luminescent species. This method was successfully applied to the detection of many cationic species in solutions and already appears in interesting commercial applications. One possible approach to the preparation of a PET like chemosensor for anions is to couple an efficient anion receptor to a luminescent moiety in such a way that binding of an anion forces the receptor out of the plane of the luminescent group and by that decreases its electronic coupling with the luminescent moiety. In such a system the fluorescence is expected to increase upon binding of the target anion.
This thesis deals with the design and synthesis of new receptors and reporter-host molecules for ions and characterization of their binding as well as their report properties.
1,3-di(2-pyrrolyl)azulene. A new azulene-based selective PET-like chemosensor that turns fluorescent upon binding the fluoride anion is presented. We explore the preparation, crystal structure characterization and anion binding properties of this azulene-based selective chemosensor that turns fluorescent upon binding the fluoride ion.
Tripyrrolemethane. We studied the anion-binding properties of tripyrrolemethane. The interaction between tripyrrolemethane and different anionic species was studied in solution, in the gas phase and in the crystalline state. Computations were applied to selected systems to improve our understanding of the experimental results.
3-(3-Ethoxymethyl-1H-imidazol-2-yl)-3-(1-ethoxymethyl-1H-imidazol-2-yl)-3H-benzo[de]isochromen-1-one. This system is a novel photo-induced electron transfer (PET) chemosensor that becomes fluorescent upon binding metal ions. The new material shows a strong preference toward ZnII ions.
Bis-(1H-imidazol-2-yl)-naphthalen-1-yl-methanol. A new anion receptor based imidazole as binding group. The interactions between Bis-(1H-imidazol-2-yl)-naphthalen-1-yl-methanol and different anionic species were studied in solution and in the crystalline state.