Anion binding has emerged as an important field of study due to the role that anionic species play in nature. As a consequence, considerable effort has been focused on the generation of anion receptors. These receptors have been designed to recognize anions through interactions, such as hydrogen bonding, donor-acceptor, and hydrophofic effects, in order to achieve higher sensitivity and selectivity. Another approach involves ion pair recognition, wherein the anions and cations are bound to the same system. Specifically, receptors bearing both hydrogen bonding donor and cation coordination sites have been of great interest as systems that lead to anion recognition and enhanced anion selectivities. Chapter 1 of this dissertation describes efforts to develop systems on the basis of modified Schiff-base calixpyrroles. This modification was achieved by incorporating a “strap” across the macrocycle to produce the so-called strapped Schiff-base calixpyrroles. The strap bearing amides are known to act as hydrogen bonding donors that can isolate the binding site from the medium. On the other hand, Schiff-base calixpyrroles have been widely studied as multidentate ligands for metal cation coordination. Therefore, the synthetic combination of these two moieties might provide a system wherein an ion pair complex is formed. Strapped Schiff-base calixpyrrole palladium complex were found to bind selectively cyanide anions. The effects of direct substitution on one meso position on the optical and photophysical properties of porphycenes was recently found to be dependent of the electronic properties of the substituten (e.g., electron donor or electron withdrawing group). However, the effects on the electronic and optical properties properties as a result of substitution through a conjugated spacer are as yet unknown. This led to the synthesis of four meso substituted etioporphycenes, which are described in Chapter 2. Here, the substitution through an ethenyl group was stablished by analytical and structural means. This chapter provides of a description of the spectroscopic, structural and voltamperometric features of these compounds. Experimental procedures and characterization data are reported in Chapter 3. / text

This thesis covers the combination of two seperate work accomplished during the throughout the study. In the first part of the study, xanthene based artificial enzymes were synthesized, and kinetic hydrolysis studies done. Artificial enzyme design is an active field of supramolecular chemistry and metalloenzymes are attractive targets in such studies. Enzymatic catalysis is essentially a &lsquo / multifuctional&rsquo / catalysis. As part of our work, we designed and synthesized three novel xanthene derivatives. All three model contain Zn(II) in their active sites. Using the model substrate p-nitrophenyl acetate, we showed that the bifunctional model is at least an order of magnitude more active in catalyzing the hydrolysis of the substrate. Compared to the uncatalyzed hydrolysis reaction of the p-nitrophenyl ester at pH 7.0, the bifunctional model complex showed a 5714-fold rate acceleration. The second part of the thesis involves the design of a dimeric calixpyrrole as a chromogenic chemosensor. Anions are involved in a large number of biological processes and there is an interest in developing molecular sensors for these charged species. The calixpyrroles are a class of old but new heterocalixarene analogues that show considerable promise in the area of anion sensing. In this work, we have designed, synthesized and characterized a calixpyrrole-dimer anion sensor for its anion binding strength. The dimer forms stable complexes with p-nitrophenolate ion. This formed complex is used as a colorimetric sensor by displacing the chromogenic anion with the addition of various anions. like fluoride and acetate. The receptor shows strong affinity and high selectivity for fluoride anion, and also show reasonable affinity toward acetate. Thus, effective optical sensing of biochemically relevant these anions is accomplished using the calixpyrrole dimer.