Porphycenes and Related Isomers: Synthetic Aspects

Abstract

Porphyrins, called the pigments of life, have been studied for decades. However, the first constitutional isomer of porphyrin, porphycene, was not synthesized until 1986. This milestone marked the beginning of a new era in the field of porphyrinoids and presented opportunities for the creation of an abundance of new pigments. The unique structural and electronic features of these compounds give rise to interesting physical and optical properties with applications in biomedicine and materials science. This review focuses on the synthetic methodologies available for the preparation of porphycenes (functionalized porphycenes, extended porphycenes, benzoporphycenes, naphthoporphycenes, and heteroanalogues) and the other known isomers, namely, corrphycene, hemiporphycene, and isoporphycene. Although the classical synthetic approaches are discussed, particular emphasis is placed on improvements to the known methodologies and recent advances in the field.

Exploring the Effect of Gold Support on the Oxygen Reduction Reaction Activity of Metal Porphycenes

“…Herein, we use density functional theory to systematically study the effect of the gold support on the ORR activity of the first row 3d transition metal‐porphycenes (MPc). Porphycene (Pc) is a constitutional isomer of porphyrin exhibiting interesting magnetic, optical, electrical and mechanical properties similar to porphyrin . Metal‐porphycenes supported on metal surfaces have attracted much attention in recent years owing to their potential application in designing molecular switches, sensors or photovoltaic devices .…”

“…[38,39] similar to porphyrin. [40][41][42] Metal-porphycenes supported on metal surfaces have attracted much attention in recent years owing to their potential application in designing molecular switches, sensors or photovoltaic devices. [43][44][45] Here, we focus on the ORR activity of unsupported molecular and gold supported 3d MPc (Figure 1).…”

Stable Expanded Porphycene‐Based Diradicaloid and Tetraradicaloid

“…[2] Our particular interest here is an isomeric porphyrin known as porphycene ( Figure 1), which was first reported in 1986 [3] and has been extensively studied for material applications. [4] Our design is to construct bithiophene and cyclopenta[2,1-b:3,4-b']bithiophene-bridged expanded porphycenes such as 1 and 2 ( Figure 1). In 1,o ne quinoidal bithiophene unit must be drawn in its closed-shell resonance form, implying that the molecule has intrinsic tendency to become open-shell diradical by recovery of two aromatic thiophene rings (pentagons shaded in blue, Figure 1).…”

An Expanded Porphycene with High NIR Absorptivity That Stabilizes Two Different Kinds of Metal Complexes

“…[1] They consist of two 2,2'-bipyrrole subunits linked by two ethylene bridges. [2,3] Ther esult is ap lanar, aromatic macrocycle formally known as [18]porphyrin (2.0.2.0). As true for porphyrins,p orphycenes contain an 18 p-electron periphery.However,compared with porphyrins, porphycenes generally display stronger absorbance features in the far-red portion of the visible spectrum owing to their lower symmetry.…”

“…[8][9][10] Whereas expanded versions of porphyrins have been widely studied, [11][12][13] expanded porphycenes are all but unknown. Examples include bronzaphyrin (2) [14] and an acetylenecumulene porphycene derivative (3). [15,16] Both 2 and 3 display red-shifted absorption features compared to 1,r eflecting an increase in the electronic pathway from 18 to 26 p-electrons.…”