123417-65-2Relevant academic research and scientific papers
Facile Aerial Oxidation of a Porphyrin. Part 4. Unsymmetrical meso-Tetra Aryl Porphyrins with 3,5-Di-t-Butyl-4-Hydroxyphenyl and 4-Hydroxyphenyl Substituents
Milgrom, Lionel R.,Mofidi, Nasrin,Jones, Christopher C.,Harriman, Anthony
, p. 301 - 310 (2007/10/02)
A series of porphyrins (2a)-(5a), unsymmetrically substituted in their meso-positions with 3,5-di-t-butyl-4-hydroxyphenyl (DtB4HP) and 4-hydroxyphenyl (4HP) groups, has been synthesised and characterised.The two di-DtB4HP di-4HP isomeric porphyrins, (3a) and (4a) (called 'cis' and 'trans', respectively), in particular are distinguishable by 1H n.m.r. spectroscopy.In basified dichloromethane (DCM) solutions, the porphyrins undergo drastic colour and u.v.-visible changes which, in 1 mol dm-3 methanolic potassium hydroxide, is indicative of irreversible aerial oxidation that is slower and less extensive than for the symmetrically tetrakis-DtB4HP substituted porphyrin (1).Cyclic voltammetry supports this, indicating that in basified DCM solutions, one-electron oxidation of porphyrins (2a)-(5a) becomes increasingly more difficult than for (1), as the DtB4HP groups are replaced by 4HP.An explanation of the relative redox activity of these porphyrins compared with (1), is offered in terms of the different electron-releasing properties of the two types of phenolic substituent.
