Von Porphyrin‐Isomeren zu octapyrrolischen Makrocyclen mit 8er‐Konformation

Vogel, Emanuel; Bröring, Martin; Fink, Jürgen; Rosen, D.; Schmickler, Hans; Lex, Johann; Chan, Kyle W. K.; Wu, Yun‐Dong; Nendel, Maja; Plattner, Dietmar A.; Houk, K. N.

doi:10.1002/ange.19951072211

Cited by 73 publications

(50 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Electronic spectra of very large porphyrinoids are often remarkably red-shifted while retaining high absorption coefficients. [39,47,100] Two-photon absorption crosssections have been recently found to correlate with NICS values of some porphyrinoids, and have therefore been advocated as a useful aromaticity criterion. [101][102][103] Magnetic Criteria.…”

Section: Aromaticity Criteriamentioning

confidence: 99%

Figure Eights, Möbius Bands, and More: Conformation and Aromaticity of Porphyrinoids

2011

View full text Add to dashboard Cite

The aromatic character of porphyrins, which has significant chemical and biological consequences, can be substantially altered by judicious modifications of the parent ring system. Expansion of the macrocycle, which is achieved by introducing additional subunits, usually increases the so-called free curvature of the ring, leading to larger angular strain. This strain is reduced by a variety of conformational changes, most notably by subunit inversion and p surface twisting. The latter effect creates a particularly convenient access to Möbius aromatic molecules, whose properties, predicted over 40 years ago, are of considerable theoretical importance. The conformational processes occurring in porphyrin analogues are often coupled to other chemical phenomena, and can thus be exploited as a means of constructing functional molecular devices. In this Review, the structural chemistry of porphyrinoids is discussed in the context of their conformational dynamics and p-electron conjugation.

show abstract

Section: Aromaticity Criteriamentioning

confidence: 99%

Figure Eights, Möbius Bands, and More: Conformation and Aromaticity of Porphyrinoids

2011

View full text Add to dashboard Cite

show abstract

“…[126,257] Untereinheiten. Bei Octaphyrin(2.1.0.1.2.1.0.1) 79a-H 4 ist der Schnittbereich durch C = C-Mesobrücken besetzt, [47] wobei eine Metallkoordination die Konfiguration dieser Brücken relativ zu den benachbarten Pyrrolringen verändern kann [93] (79a-Pd 2 , Abbildung 14 [47,100,126] Zweitens lässt sich durch Metallkoordination für manche Octaphyrine eine bestimmte Reaktivität erzeugen, [267] die ganz klar aus der verstärkten sterischen Kompression am Kreuzungspunkt der FigureEight herrührt. So lagert sich der zweikernige Komplex 77a-Pd 2 in einer elektrocyclischen Reaktion zum bicyclischen Derivat 92a um.…”

Section: T1-und T2-systemeunclassified

Figure‐Eight‐Strukturen, Möbius‐Bänder und mehr: Konformation und Aromatizität von Porphyrinoiden

2011

View full text Add to dashboard Cite

Der aromatische Charakter von Porphyrinen, der signifikante chemische und biologische Auswirkungen hat, kann durch gezielte Modifikationen des Stammringsystems beträchtlich verändert werden. Zusätzliche Untereinheiten expandieren den Makrocyclus und erhöhen seine Ringkrümmung, was zu einer höheren Winkelspannung führt. Diese Winkelspannung kann der Ring durch eine Reihe von Konformationsänderungen wieder abbauen, insbesondere durch Invertieren von Untereinheiten und Verdrillen (twisting) der π‐Oberfläche. Letzterer Effekt bietet einen Zugang zu Möbius‐aromatischen Molekülen, deren Eigenschaften, gleichwohl vor über 40 Jahren vorausgesagt, unter theoretischen Aspekten von großer Bedeutung sind. Häufig gehen Konformationsprozesse in den Porphyrinanaloga mit anderen chemischen Phänomenen einher, sodass sie für den Aufbau von molekularen Funktionseinheiten verwendet werden können. In diesem Aufsatz wird die Strukturchemie der Porphyrinoide im Zusammenhang mit ihrer Konformationsdynamik und elektronischen π‐Konjugation diskutiert.

show abstract

“…[1,6] Typically all these different classes of cyclic polypyrrole compounds are accessible through specific and dedicated synthetic routes, and one cannot easily be transformed into another (Scheme 1). A notable exception was the finding that metal complexes of some octaphyrins [4] can undergo a thermal transformation into spirodicorroles 4. [7] Some of these compounds can be split into two porphyrins in which the expanded porphyrins are linked with "regular" tetrapyrroles.…”

mentioning

confidence: 98%

“…There has been an immense surge in the preparation of structural homologues and isomers with different arrangements of the macrocycle atoms of these systems, and significant advances have been made to construct so-called isomeric (for example, N-confused porphyrins or porphycenes), [3] expanded (texaphyrins or octaphyrin 3), [4] or contracted porphyrins (corrole 2). [5] This surge was accompanied by significant progress in the synthetic methodology for their preparation as well as for the development of novel hydroporphyrins, nonaromatic tetrapyrroles, and conformationally designed systems.…”

mentioning

confidence: 99%