Palladiumkomplexe der neuen Porphyrinisomere (Z)‐ und (E)‐Isoporphycen – Pd^II‐induzierte Cyclisierungen von Tetrapyrrolaldehyden

Abstract

Templat‐gesteuerte Synthesen öffnen das Tor zu stabilen Metallkomplexen des bislang hypothetischen, energiereichen Porphyrinstrukturisomers Isoporphycen. Die auf Rechnungen gegründete Voraussage, daß (Z)‐ und (E)‐Isoporphycen ähnliche Energien aufweisen, wird durch die Existenz der in raschem photochemischem Gleichgewicht befindlichen (Z)‐ und (E)‐Octaethylisoporphycen‐Pd‐Komplexe 1 bzw. 2 qualitativ bestätigt. Ein kleiner Pd‐H‐Abstand in 2, C‐C‐C‐Bindungswinkel von fast 150° in 1 sowie 1H‐NMR‐spektroskopische Parallelen zum all‐cis‐ bzw. mono‐trans‐Cyclononatetraenyl‐Anion machen 1 und 2 zu interessanten Studienobjekten.

Bridging the Gap between Porphyrins and Porphycenes: Substituent‐Position‐Sensitive Tautomerism and Photophysics in meso‐Diphenyloctaethylporphyrins

“…[5][6][7][8] The first constitutional isomer, porphycene (Pc, Scheme 1) was synthesized in 1986. [9] Four more isomers have since been obtained: hemiporphycene, [10,11] corrphycene, [12,13] isoporphycene, [14,15] and "inverted" ("confused") porphyrin. [16,17] Thus far, research has been dominated by studies on porphycenes.…”

Neo‐Confused Porphyrins, a New Class of Porphyrin Isomers

“…Porphycene retains highly aromatic characteristics and while the macrocyclic core is elongated compared to the symmetrical cavity in true porphyrins, the system retains the ability to form numerous coordination complexes. [2] Constitutional isomers with other arrangements of the linking carbon atoms were subsequently reported, [3][4][5][6] specifically hemiporphycene, [4] corrphycene, [5] and isoporphycene. [6] In all of these analogues, the pyrrolic nitrogens are orientated into the central macrocyclic cavity.…”

A theoretical study of porphyrin isomers and their core-modified analogues:cis-trans isomerism, tautomerism and relative stabilities

“…8 The porphyrin isomers reported to date include, corrphycene, hemiporphycene, and isoporphycene obtained by shuffling the four pyrrolic subunits and the meso-carbon bridge. 5,[8][9][10][11][12] Many research groups have recently exploited some of the unique properties exhibited by the N-confused porphyrins because their remarkable ability to act as tetra-coordinate ligands to form transition metal complexes. 4 This led to a flurry of synthetic attempts toward novel porphyrin-like molecules, with structural variants such as ring or bridge extended, reshuffled, inverted, N-and C-fused, contracted and core-modified porphyrins.…”

“…4 This led to a flurry of synthetic attempts toward novel porphyrin-like molecules, with structural variants such as ring or bridge extended, reshuffled, inverted, N-and C-fused, contracted and core-modified porphyrins. 5,[11][12][13] Wu et al carried out density functional calculations using both the BLYP/3-21G and BLYP/6-31G** methods on free-base porphyrins and their possible isomers with an N 4 -metal coordination core. 9 Ghosh and Jynge reported BLYP/6-31G** calculations on cis and trans porphyrin isomers having [3⋅0⋅1⋅0], [3⋅1⋅0⋅0] and [4⋅0⋅0⋅0] connectivity.…”