Tetraazuliporphyrin Tetracation

Abstract

At the crossroads: A unique carbon-bridged annulene motif--dehydroquatyrin--is imprinted into the molecular structure of the tetraazuliporphyrin tetracation (see picture). The macrocycle, which lies at the intersection of annulene, carbocation, and porphyrin chemistry, is obtained by the standard condensation of azulene and arylaldehyde followed by oxidation. The meso positions of the tetracation are susceptible to anionic or weak nucleophilic attack.

Incorporation of a p‐Phenylene Unit into the Azuliporphyrinogens Frame—Oxidation and Ruthenium Cluster Coordination

“…Evidently, 6 a completes the group of previously investigated azuliporphyrinogen stereoisomers of higher symmetry . These macrocycles conserve the specific structural facet.…”

“…Although, one could not generate the stable tetracationic form 8 from porphyrinogen 6 in a standard procedure, it is arguably formed as an intermediate product while converting dication 7 into 9 (Scheme ). The increased electrophilicity of 8 seems to be corroborated by the incorporation of the p ‐phenylene motif, as both tetraazuli‐ and thiatriazuliporphyrinogens could stabilize four positive charges in their tetracationic macrocyclic frameworks …”

“…Carbaporphyrinoids incorporating three or four carbocyclic rings in their skeleton include tetracation of tetraazuliporphyrin 3 4+ [4] and tetracation of thiatriazuliporphyrin 2 4+ (Figure ) . Azuliporphyrinogens, once oxidized, have yet another special feature—they are macrocyclic polycarbocyclic systems that can serve as molecular reservoirs of positive charge significantly concentrated on meso bridges . Such a characteristics triggers unusual spectroscopic properties and peculiar reactivity.…”

“…[2] Still, most of the known carbaporphyrinoid systemsc ontain no more than two carbocyclic units in their structure. [3] Carbaporphyrinoidsi ncorporating three or four carbocyclic rings in their skeleton include tetracation of tetraazuliporphyrin 3 4 + + [4] and tetracation of thiatriazuliporphyrin 2 4 + + (Figure 1). [5] Azuliporphyrinogens, once oxidized, have yet another special feature-they are macrocyclic polycarbocyclic systemst hat can serve as molecular reservoirs of positive charges ignificantly concentrated on meso bridges.…”

“…[5] Azuliporphyrinogens, once oxidized, have yet another special feature-they are macrocyclic polycarbocyclic systemst hat can serve as molecular reservoirs of positive charges ignificantly concentrated on meso bridges. [4,5] Such ac haracteristics triggers unusuals pectroscopic properties and peculiar reactivity.I nc ontrast, dications of dithiadiazuliporphyrin 1 2 + + [6] and dioxadiazuliporphyrin [7] localize the positive charged ifferently than 2 4 + + and 3 4 + + carbocations.T hese speciesr eveal the tropyliumn ature of the 7membered ring of azulene eventually inducing macrocyclic aromaticity.…”