Electrochemical investigation of the new dyad of the Zn2+ derivative of meso-5-(4-hydroxyphenyl)-10, 15, 20- tris (4-methoxyphenyl) porphyrin and meso-5-(4-hydroxyphenyl)-10,15,20- trisphenyl porphyrin points to photoinduced electron transfer

The synthesis of a porphyrin dyad with the combination of free-base and Zn porphyrin units was attempted. The criterion for the selection of individual units was their monomer redox potentials. In this respect, several porphyrin derivatives, namely meso-5-(4-hydroxyphenyl)-10,15,20- trisphenyl porphyrin (HPTrPP), meso-5-(4-hydroxyphenyl)-10, 15, 20- tris(4-methoxy phenyl) porphyrin (HPTrMPP), meso-5-(4-hydroxyphenyl ) -10,15,20- t r is(4-sul fonatophenyl ) ammoniumporphyrin [NH4]3[HPTrSPP] and their Zn2+ derivatives were synthesized and characterized by UV-visible spectroscopy, 1H NMR spectroscopy and cyclic voltammetry. Out of the six compounds, Zn2+derivative of HPTrMPP was found to show the lowest excited state oxidation potential (-1.41 V) while [NH4]3[HPTrSPP] exhibited the lowest reduction potential of its ground state (-0.91 V) and that of the excited state at 0.94 V. Similarly, HPTrPP also showed favourable one electron reduction potentials of -1.11 V and 0.77 V for ground and excited states, respectively. The coupling of Zn2+ derivative of HPTrMPP (donor) and HPTrPP (acceptor) was accomplished by means of a butyl spacer to yield the dyad. The excitation of ZnHPTrMPP by visible light resulted in photoinduced electron transfer from ZnHPTrMPP to HPTrPP.

Keywords: Acceptor, donor, photoinduced electron transfer, porphyrin dyad.

DOI: http://dx.doi.org/10.4038/jnsfsr.v40i2.4442

J.Natn.Sci.Foundation Sri Lanka 2012 40(2):149-156