UV/VIS-Spectroscopic investigation of new porphyrin-isomers

We investigated the UV/VIS absorption and fluorescence spectra of the octae thyl derivatives of hemiporphycene and isoporphycene, two novel porphyrin i somers. In the case of octaethylhemiporphycene the temperature dependence o f the absorption spectrum was used to determine the enthalpy of the tautome rization reaction using van't Hoff's equation. For octaethylisoporphycene f luorescence bands of both the (E)- and (Z)-isomer could be observed and exc itation spectra of both compounds were recorded and analysed. (C) 1999 Else vier Science B.V. All rights reserved.