STRUCTURE OF EXPANDED PORPHYRINS - ELECTRON-NUCLEAR MULTIPLE RESONANCE AND MOLECULAR-ORBITAL STUDIES OF TEXAPHYRIN ANION-RADICALS IN SOLUTION

Liquid solution ENDOR and TRIPLE resonance experiments have been perfo rmed on texaphyrin radical anions generated by sodium reduction in tet rahydrofuran. Six proton and two nitrogen hyperfine couplings could be determined, including their signs. The results were compared with the oretical isotropic hyperfine couplings. They were calculated for energ y-minimized texaphyrin structures, including the sodium metallo-deriva tive, by state-of-the-art SCF-MO methods (RHF-INDO/SP). This compariso n suggests that in the course of the alkali metal reduction of texaphy rin the acidic hydrogen in the macrocycle is replaced by sodium.