Expanded porphyrins have been used extensively to study aromaticity and antiaromaticity effects. Most expanded systems, like the naturally occurring porphyrin congeners, rely on 2,5-disubstituted pyrroles as a key subunit (Figure 1). These pyrroles allow for through conjugation in both their reduced and oxidized states, enabling access to different electronic states for the system as a whole. In this presentation, the chemistry of macrocycles designed with the ability to incorporate other subunits into the (anti)aromatic core will be discussed. Particular emphasis will be devoted to a hybrid system, cyclo[1]furan[1]-pyridine[4]pyrrole (F1P1P4).[1] It is one of the first expanded porphyrins to rely on the combination of furan, pyrrole, and pyridine. Upon complexation of the uranyl cation, the dianionic form [F1P1P4 – 4H]2- can be stabilized, yielding a 22 π-electron aromatic macrocycle (Figure 2). The underlying change in electronic structure is readily apparent in the UV-vis-NIR, NMR, excited state lifetimes, as well as an easy-to-visualize change in color from yellow to green. Separate studies have served to show that the F1P1P4 uranium complex may be detected at concentrations down to 6.2 ppb (5.7 nM) in vitro and 0.57 ppm (0.52 μM) in vivo.[2] Current work is focused on extending the complexation chemistry to other actinide cations, modification of the ester substituents to allow for improved solubility, and incorporation of F1P1P4 into polymeric matrices. A summary of this recent work along with an overview of published and ongoing synthetic efforts will be reviewed in this presentation. References [1] Ho, I-Ting; Zhang, Zhan; Ishida, M.; Lynch, V. M.; Cha, WY; Sung, YM; Kim; D.; Sessler, J. L. J Am Chem Soc. 2014, 136, 4281-4286 [2] Ho, I-Ting; Sessler, J. L.; Gambhir, S. S.; Jokerst, J. V. Analyst, 2015, 140, 3731-3737

Expanded porphyrin cyclo[1]furan[1]pyridine[4]pyrrole: A hybrid macrocycle displaying aromatic character upon cation complexation

251st National Meeting (2016)

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