Functionalized oligopyrroles : from supramolecular fluorescent sensors to molecular self-assembly
Perhaps the simplest yet most elegant oligopyrrolic macrocycles are nature’s so-called pigments of life, namely chlorophyll and Vitamin B₁₂. From the perspective of chemists, the versatility of pyrrole moieties encourages us to assemble these along with other targets and produce numerous oligopyrrole derivatives with diverse functions so as to address unmet challenges. Of particular interest are the anion binding capabilities associated with certain oligopyrroles in both cyclic and acyclic forms. In this regard, the marriage of oligopyrroles with fluorophores allows us to create supramolecular fluorescent anion sensors capable of translating the host–guest binding events into optical (e.g., fluorescent) readouts. The dissertation details the author’s efforts to develop new supramolecular fluorescent anion sensors based on the above two forms of functionalized oligopyrroles, i.e., formylated dipyrromethanes and calixpyrroles. Particular efforts were made to tune their substrate specificities and fluorescence sensing features. In addition, this dissertation details the author’s rudimentary investigations involving the molecular self-assembly features of calixpyrrole-based host–guest complexes. Chapter 1 provides an introduction to the fundamentals and historical overview of anion receptors and fluorescent anion sensors as well as a brief review of recent advances in supramolecular fluorescent sensors for anions. Chapter 2 describes the rational design of a pyrene-linked formylated bis(dipyrromethane) that acts as a fluorescent probe for dihydrogen phosphate. Chapter 3 is focused on a molecular caliper that serves as a fluorescent sensor for dicarboxylate dianions and which is based on the marriage of the calixpyrrole-based anion recognition and vibration-induced emission (VIE). Chapter 4 describes the use of a pair of meso-dipyrenyl calixpyrroles to create an ion pair binding-based fluorescence-tunable supramolecular system that allows for the white light emission. Chapter 5 details the molecular recognition of pyrazine N,N’-dioxide using aryl extended calixpyrroles, as well as the associated guest-directed self-assembly in the solid state. Chapter 6 consists of supplementary data and includes synthetic experimental details and characterization data for all new compounds.