Neo-N-confused Phlorins and Phlorinone: Rational Synthesis and Tunable Properties.

By the acid-catalyzed [2 + 2] condensation, an unprecedented neo-N-confused phlorin (neo-NCphlorin 1) was successfully synthesized. By treating 1 with N-chlorosuccinimide, the corresponding chloro-substituted neo-NCphlorin (1-Cl) was obtained. The oxidization of 1 with FeCl3 afforded the neo-N-confused phlorinone (neo-NCphlorinone 2), which bears a relatively coplanar conformation, different from the highly distorted ones observed for 1 and 1-Cl. Notably, 2 shows striking long-wavelength absorption beyond 1300 nm upon addition of TBAF.