Abeje Abebayehu

A new hexapyrrolic macrocycle composed of three naphthobipyrrole units has been synthesized which exhibited different emission changes with hydrogen pyrophosphate and benzoate ions. Phosphate ions caused red shifting of the fluorescence band of calixnaphthobipyrrole while benzoate ions resulted in quenching of the same. The fluorescence quenching was further utilized for investigating binding preferences of the probe with neutral aromatic guest molecules substituted with groups having varied electron withdrawing abilities. The extent of quenching with the neutral guests increased with the increasing electron deficiency on the aromatic ring of the guest. The fluorescence quenching has been ascribed to electron transfer from the host to the guest species.

Oligopyrrolic macrocycles based on the naphthobipyrrole scaffold have been synthesized and characterized. The compounds showed high affinities toward multi‐oxo anions such as dihydrogen phosphate and sulfate anions in acetonitrile. Theoretical calculations for the formation of host–anion complexation revealed that the receptors adopt bowl‐shaped, cone conformations with association constants of ca. 10⁶ m^–1 with dihydrogen phosphate anions.

We present the synthesis and characterization of a new family of expanded meso‐alkylidenyl (2,6‐pyri)porphyrinoids bearing multiple exocyclic double bonds at the meso‐positions. The synthesis was accomplished by using mixed pyrrole condensation. Similar to meso‐alkylidenyl porphyrinoids, this study revealed that pyriporphyrinoids do not possess a porphyrin‐like, global‐aromatic character. The synthesized 2,6‐pyripentaphyrin 1 displays selective ratiometric sensing of pyrophosphate anion in organic solvent.

Treatment of meso-malonylidene-(m-benzi)porphyrin and meso-malonylidene-(m-benzi)pentaphyrin with Pd(II), Au(III), Ni(II) and Ag(I) afforded the corresponding metal complexes. The synthesized metal complexes were characterized by spectroscopy including single crystal X-ray, NMR and mass spectrometry. Most metal complexes were stable in solution. The metal complexes showed strong absorption in the near IR region.