Both-faces hindered porphyrins. Part 2. Synthesis and characterization of internally five-co-ordinated iron(II) basket-handle porphyrins derived from 5,10,15,20-tetrakis(o-hydroxyphenyl)porphyrin

Abstract

Compounds (9), so-called ether ‘hanging base’ porphyrins, derived from 5,10,15,20-tetrakis(o-hydroxyphenyl) porphyrin in which one of the faces is hindered by a pyridine-3,5-diylbisalkylene bridge and the other face is protected by an alkylene or an p-arylenebisalkylene chain have been synthesized following the concept of the ‘basket handle’ porphyrins (BHP). From an analysis of the ¹H n.m.r. spectra of their iron(II) derivatives (20) at 34 °C, it has been determined that ca. 85% were high-spin five-co-ordinated complexes (s= 2). Despite the steric hindrance of the distal face, bimolecular associations typical for this class of compounds have been detected except for the most hindered (20c). An additional bispyridine ‘basket handle’ porphyrin (21) has been synthesized in order to study the dynamics of the pyridine chain.