Octaethyltetraoxaporphyrin-Dikation – Pendant des Octaethylporphyrins in der Tetraoxaporphyrin-Reihe

Furan-Based Porphyrins: Tetraoxa[4n+2]porphyrin Dications with 18π-, 22π-, or 26π-Electron Systems

“…[2] As with its NCH 3 analogue, 13 is characterized by an unusually strong diamagnetic ring current which is manifested in the position of the signals of the outer-and inner-perimeter protons at extremely low and high field: C NMR spectra (six signals) and the finding that the structure of 13 exhibits a planar ring framework (see the following communication [19] ). A comparison of the UV/Vis spectrum of 13 with those of the octaethyl derivatives 1 a [15] and 8 a [13] of 1 and 8 is particularly informative. Characteristic of the spectra of 13 and 1 a is that each displays an extraordinarily sharp Soret band which exhibits almost no vibrational structure (half peak width ca.…”

Porphyrinoids with 26 π Electrons: Molecules with Exceptional Spectroscopic Properties

“…As can be seen from Table 1, a conspicuously good agreement exists between the chemical shifts of the outer-and inner-perimeter protons H o and H i of 1 and 2Ðand thus also for the Dd value (d(H o ) À d(H i )), which may be regarded as an indicator of the ring current effect. The lowand high-field shifts of H o and H i in 1 and 2, which at a first glance appear abnormal (for comparison: the signal for H o in 2 is shifted to lower field by about 2.8 ppm relative to that for the meso protons in the octaethyltetraoxa [18]porphyrin dication [8] ), may be rationalized in part if it is considered that the strength of the diamagnetic ring current effect increases with the number of p electrons and with the area of the molecule. [9] In light of the structural findings the 1 H NMR spectrum of 1 at room temperature, which suggests the presence of a D 4h -symmetric and thus planar molecule, can only be explained by the assumption that the NCH 3 groups oscillate through the ring framework very quickly on the NMR time scale.…”

Porphyrine auf Furan-Basis: Tetraoxa[4n+2]porphyrin-Dikationen mit 18π-, 22π- bzw. 26π-Elektronensystem

“…Die besondere Aufmerksamkeit gilt hier dem UV/Vis-Spektrum von 13 im Vergleich mit denen der Octaethylderivate 1 a [15] und 8 a [13] von 1 bzw. 8 (Abbildung 2).…”