The synthesis and characterization of one or two BODIPY fragments appended to four new chiral and one new achiral diamines is described. All of the examined BODIPY-appended diamines exhibit a quasireversible-irreversible reduction, with two reductions (separated by about 100 mV) observed in the case of diamines containing two BODIPY molecules. Only the BODIPY-appended ortho-phenylenediamines did not fluoresce under UV light. Computational analysis showed that the absence of fluorescence of the BODIPY-appended ortho-phenylenediamines is likely due to intramolecular quenching of the excited state electron within the phenylenediamine ligand. Computational analysis also showed that the incorporation of a BODIPY molecule greatly reduces the basicity of the amine center, by about 10–14 pKa units. The BODIPY moiety was found to be more electron withdrawing than a tosyl and a pentafluorophenyl group, suggesting why excess metals are needed in heavy metal sensor applications (heteroatom-appended BODIPYs = poor ligands). An improved procedure for the scalable synthesis (greater than three grams) of 8-methanethio-BODIPY, a common starting material for the generation of heteroatom-appended BODIPY molecules, is also described.
