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

Abstract

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 FeCl 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.

Loading Phlorins with Fullerenes by a [4 + 2]-Cycloaddition Reaction: Regulation of the Regioselectivity by Pyrrole Linkage Modes

“…The syntheses of sulfolenophlorins were based on the acid-catalyzed [2 + 2]-condensation reaction. , However, the dicarbinol intermediates were collected as a white powder by filtration after quenching the reaction with H 2 O rather than the early reported yellowish residue by extraction with dichloromethane (DCM) and condensation (see the Experimental Section). The slight optimization improves the TFA-catalyzed [2 + 2]-condensation reactions of sulfolenodipyrromethane and common dicarbinol or the N-confused one.…”

“… − These new species feature excellent long-wavelength absorption, enriched redox activities, and outstanding affinity toward anion (e.g., F – , AcO – ). , Although the synthesis of phlorin can date back to 1960 when Woodward employed it as an intermediate in the total synthesis of chlorophyll, the breakthrough for efficiently preparing such macrocycles took place until early 2000. Thereafter, many novel phlorin derivatives such as N-confused phlorins, − core-modified phlorins, − and expanded phlorins − have been prepared with the aim to investigate the chemical transformations, unique photophysical properties, as well as chelating/sensing behaviors in-depth. However, the restriction of the meso-substituents (C 6 F 5, etc.)…”

“…As a result, phlorin 1 contains two sufolenopyrrole units with identical reactivity upon tautomerization and undergoes stepwise [4 + 2]-cycloaddition with fullerenes, giving the mono and bis-fullerene adducts at 140 °C. By contrast, compound 2 containing one confused pyrrole shows a low tendency to tautomerize, resulting in the presence of two different sufolenopyrroles, i.e., the normal (Figure filled with green color) and imino-type (Figure filled with pink color) pyrrole units. Notably, 2 can react with fullerene at milder thermo-conditions (at 120 °C) to afford the monoadduct ( 2-C60 ) as the dominant product accompanied by a trace amount of bisadduct ( 2-2C60 ).…”

Expanded N-Confused Phlorin: A Platform for a Multiply Fused Polycyclic Ring System via Oxidation within the Macrocycle

“…The corresponding N-confused phlorin analog is more stable compared with the regular phlorin in terms of thermal energy (Figure c) . We have thus developed the phlorin chemistry; the peripheral π-extended N-confused phlorin–prodigiosin chimera demonstrated metalation-induced tuning of optical properties occurring at the inner NNNC and outer NNN donor sites . The silver and boron complexation resulted in the emergence of NIR absorption beyond 1000 nm based on the distinct acyclic π-circuit structures.…”

Synthesis, characterization, and spectroscopic properties of 2‐(3,5,6‐trichloro‐1,4‐benzoquinon‐2‐yl)‐neo‐fused hexaphyrin

“…Among them, expanded porphyrins are a class of porphyrin analogs developed by increasing the number of heterocyclic rings or meso carbon atoms in the porphyrin framework. On the other hand, N‐confused porphyrins have also been developed as an important class of porphyrinoids by changing the linking modes between the pyrrolic units from α–α' to α–β' 4 . These porphyrinoids exhibit unique properties and potential applications in materials science, supramolecular chemistry, and bioscience 5 .…”