Porphyrinoids with 26 π Electrons: Molecules with Exceptional Spectroscopic Properties

Abstract

Record extinctions ε of 1.6×106 and 1.0×106 for the UV/Vis Soret bands, as well as extreme chemical shifts for the inner and outer perimeter protons in the 1H NMR spectra, characterize the two closely related 26π porphyrinoids 1 and 2, respectively. The dichotomy that 1 and 2 differ markedly in the extinctions of the Soret bands (appearing at nearly the same wavelength) yet almost agree—within the limits of comparison—in the 1H NMR spectra is explained convincingly on the basis of the molecular structures of the two compounds.

Synthesechemie expandierter Porphyrine

“…Fasziniert von den außergewöhnlichen spektroskopischen Eigenschaften des von Franck21 beschriebenen N,N ′, N ′′, N ′′′‐Tetramethyl[26]porphyrin(3.3.3.3)‐Dikations ( 21 ) widmeten sich Vogel et al einer genaueren Untersuchung der chemischen Eigenschaften von 21 und einer Reihe eigens synthetisierter verwandter Verbindungen 35. 36 Ziel dieser Arbeiten war es, das D 4 h ‐symmetrische Tetraoxa[18]porphyrin‐Dikation ( 17 ) mit seinen Homologen, dem all‐cis ‐Tetraoxa[22]porphyrin(2.2.2.2)‐Dikation ( 18 ) und dem Tetraoxa[26]porphyrin(3.3.3.3)‐Dikation ( 19 ), spektroskopisch zu vergleichen.…”

“…Des Weiteren wurden die Strukturen und Spektren des N,N ′, N ′′, N ′′′‐Tetramethyl[26]porphyrin(3.3.3.3)‐Dikations ( 20 ) und des Octaethyltetraoxa[26]porphyrin(3.3.3.3)‐Dikations ( 21 ) verglichen 36. Während die Struktur von 20 im Kristall (Abbildung 5) ein fast planares makrocyclisches Gerüst erkennen lässt, das nur geringfügig von der erwarteten D 4 h ‐Symmetrie abweicht, ergab die entsprechende Strukturanalyse für 21 (Abbildung 6) einen Makrocyclus in Form einer flachen Schale.…”

Edge Decoration of Anthracene Switches Global Diatropic Current That Controls the Acene Reactivity

“… 1 , 7 In contrast with this, the edge mode led to the full assimilation of both π-systems and a substantial extension of conjugation, influencing the optical properties, 6 which could be further modulated via the redox activation of furan-based structures. 8 On the contrary, the geometric constraints introduced in specifically constructed motifs gave a field for testing the reactivity that was unavailable without a macrocycle. 9 It could also force a close proximity of units in the cavity, resulting in, for example, strong hydrogen bonding.…”

“… 9 It could also force a close proximity of units in the cavity, resulting in, for example, strong hydrogen bonding. 10 Thus the macrocyclic confinements present the potential for opening global conjugation, 8 which can influence all involved subunits, including acenes, that, depending on the orientation, can serve as donors for a dopant entrapment 2 and also introduce donors/acceptors for an unprecedented interaction.…”

“…The archetypal motif of anthracene, the elongated acene, was explored as a building block incorporated into macrocyclic skeletons with the linear and the edge mode (Figure ). The linear mode, reported in two variants of mutual influence of two π-clouds, gave a specific interaction showing a competition between the local and global effects of delocalization. , In contrast with this, the edge mode led to the full assimilation of both π-systems and a substantial extension of conjugation, influencing the optical properties, which could be further modulated via the redox activation of furan-based structures . On the contrary, the geometric constraints introduced in specifically constructed motifs gave a field for testing the reactivity that was unavailable without a macrocycle .…”