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Molecular recognition exploiting non-covalent interactions mediates the structure and function of many critical biological and synthetic molecules. There has thus been continuing and intense efforts in the design and synthesis of supramolecular systems with the capability of recognizing specific chemical species. Among various guest species, Prof. Sessler's group has been focused on the study of artificial anion receptors. Calix[4]pyrrole is a tetrapyrrolic macrocycle that is capable of binding anions via concerted and directional hydrogen bonding. Recently, a tetrathiafulvalene (TTF) functionalized calix[4]pyrrole (TTF-C4P) was synthesized and studied as a receptor for various guest species such as anions, electron deficient guest species, and C₆₀. This dissertation focuses on the recent discovery in supramolecular chemistry of TTF-calix[4]pyrrole derivatives. Chapter 1 provides a brief overview of the historical perspective, redox properties, and uses of TTF derivatives as functional building blocks for supramolecular assemblies, as well as previous findings involving the supramolecular chemistry of TTF-C4P. Chapter 2, as the major focus of this dissertation, describes ion mediated supramolecular and reversible electron transfer processes between TTF-C4P and bisimidazolium salts (BIQ²⁺2X⁻). We discovered that the electron transfer processes between these redox couples could be controlled reversibly by ion binding. Specifically, we found that anion binding to the TTF-C4P receptor promotes the forward ET processes. In contrast, cation complexation to the cavity of TTF-C4P causes the reverse ET processes. Such ion mediated ET processes play an essential role in biological ET systems including photosynthesis and respirations. These reversible ET processes were mapped out by spectroscopic (¹H-NMR, UV-Vis NIR titrations, and EPR analysis) and X-ray single crystallographic analyses of both the intermediate and products. Chapter 3 describes the synthesis of aromatic (thiophene and benzene) annulated TTF-calix[4]pyrroles as new and significantly improved receptors for poly-nitroexplosives. The resulting electronic modulations of the parent TTF-pyrrole structure result in significantly enhanced binding affinities for the corresponding TTF-C4Ps toward polynitro-explosives. This is reflected in a high level of positive homotropic allosterism. The degree of the cooperative effect was found to vary depending on the nature of both the receptors and guest species. The origin of the cooperative binding can be explained by conformational locking and an inductive effect of binding the first nitroaromatic guest.

The surface coating industry is facing increasingly stringent environmental regulations that require the control of volatile organic compounds (VOCs) and hazardous air pollutants. Biofiltration is an attractive alternative for paint spray booth applications but these facilities pose several challenges to biofiltration technology . Specifically, offgas streams from painting operations are characterized by complex VOC mixtures, frequent shutdown and restart events, high volumetric flow rates, and relatively low contaminant concentrations. The objectives of this research were to investigate the feasibility of biofiltration for paint spray booth applications and to delineate how key operating parameters and biofilter history affect the degradation of VOC mixtures and the microbial population in biofilters. The results indicate that biofilters are a feasible option for treating the emissions from paint spray booth facilities. Removal efficiencies as high as 95% or greater were achieved even under intermittent feed conditions. Biofilter performance was found to strongly depend on nitrogen supply, particularly during the start up period. Overall VOC removal was limited by the toluene and xylene components of the waste gas stream. When the inoculating culture was developed so as to maintain the degradation capacity of the culture for each VOC component of the paint mixture, a sequential feeding strategy did not provide any initial advantage with respect to VOC removal; however, the system ultimately achieved higher removals of the toluene. Biofilm samples analyzed using the DGGE technique indicate that the fungal population in the bioreactors was relatively uniform across the biofilters and stable over extended periods of operation. The DGGE banding pattern for the bacterial population, on the other hand, indicates that the bacterial community was spatially distinct and became less diverse after 200 days of operation. While this research focused on biofilters treating paint VOC mixtures, it is anticipated that many of the phenomena observed will be applicable to other bioreactor systems and contaminant mixtures.