Bromine‐Terminated β‐Alkyl‐Substituted Tripyrrin: Reactivity, Coordination Ability, and Role as Extendable Acyclic Oligo‐Pyrrole Ligand

Abstract

AbstractBromine‐terminated tripyrrin, a partial porphyrin structure, is synthesized by saponification of tripyrrane dimethyl ester and subsequent treatment with an aqueous bromine solution. In this reaction, bromine serves as a decarboxylating, oxidizing, and brominating agent. The resulting ligand can be coordinated with a metal ion such as Re+, which is not easily encapsulated in porphyrin cores. Nucleophilic substitution reactions at the brominated positions were also investigated, particularly the substitution with diethylamino and/or ethoxy groups. Structural elucidation was carried out by X‐ray crystallography, which revealed the flatter frameworks of the free bases and distorted geometries of the metal complexes. Such chemical modifications dramatically influence the photophysical properties, such as UV‐visible absorption, and are promising for bio‐related applications such as SPECT imaging probes.