Professor Christian Bruckner of the University of Connecticut

"The Breaking and Mending of Porphyrins: Synthesis of Pyrrole-modified Porphyrins"

Porphyrins and related 'pigments of life' are composed of four pyrrolic building blocks. Their extended π-structures impart on them strong light absorption and bright fluorescence emission in the visible range and pronounced photosensitization abilities. To fully utilize these properties, several technical and medical applications would benefit from absorbance/emission in the red or NIR regions of the electromagnetic spectrum. To this end, our group developed synthetic strategies toward the step-by-step conversion of one or two – and most recently, three – pyrrole moieties in porphyrins into non-pyrrolic 4-, 5-, 6- to 8-membered heterocycles. While some of those substitutions result in dramatically altered and red-shifted optical spectra compared to the parent porphyrin, others had little effect. We will report on the syntheses of these so-called 'pyrrole-modified porphyrins' and demonstrate to which extend the modifications affected their chemical reactivity, conformation, conformational flexibility, metal coordination, and photochemical properties. Their utilization in chemosensing, photo-acoustic imaging, catalysis, and photochemotherapeutic applications is highlighted. The work touches upon synthetic heterocycle, coordination, and physical organic chemistry.

Recent review: Acc. Chem. Res. 2016, 49, 1080. See also, e.g.: J. Am. Chem. Soc. 2011, 133, 8740; J. Org. Chem. 2013, 78, 2840; J. Org. Chem. 2012, 77, 6199; Inorg. Chem. 2017, 56, 11490. J. Am. Chem. Soc. 2017, 139, 548. J. Org. Chem. 2020, 85, 15273. Inorg. Chem. 2020, 59, 2870. Chem.—Eur. J. 2021, 27, 16189. Chem. Sci. 2021, 12, 12292. J. Org. Chem. 2022, 87, 7179. J. Org. Chem. 2022, 87, 12096. J. Org. Chem. 2024, 89, 6584.