A new general method for selective β-polynitration of porphyrins; preparation and redox properties of Zn-porphyrins bearing one through to eight β-nitro substituents and X-ray structure of the first Zn β-pernitro porphyrin

Abstract

Selective β-polynitration of Zn–5,10,15,20-tetrakis(2,6-dichlorophenyl)porphyrin, Zn(TDCPP), is achieved by controlled titration with the HNO3–CF3SO3H–(CF3S O2)2O system, and affords a full series of Zn porphyrins bearing one through to eight β-nitro groups in high yield and exhibiting a wide range of reduction potentials (from −920 to +155 mV vs. SCE); an X-ray structure of the first reported β-pernitrated Zn porphyrin Zn(TDCPN8P)(EtOH)2·2EtOH confirms the synthetic methodology.