Light-Induced Reversible Ionization of N, N, N′, N′-Tetramethyl-p-phenylenediamine in an Inorganic Polymer of Butyl Titanate

Abstract

As reported previously, a polymerized butyl titanate (BT) in an organic solvent such as tetrahydrofuran yields a material which can be excited by visible light to give a characteristic ESR absorption. In the present work, addition of p-phenylenediamine (PD), N, N-dimethylpphenylenediamine (DMPD), or N, N, N′, N′-tetramethyl-p-phenylenediamine (TMPD) has been tried to get composite BT polymers. The TMPD-added BT polymer gives an ESR absorption under the illumination with visible light. The peak positions of this ESR absorption spectrum coincide well with those of the simulated ESR spectrum of TMPD^.+ under the assumption of a free motion of the cation, but a difference is seen with regard to the line width and relative peak intensity. Probably this is because the TMPD^.+ trapped in the polymer does not have such freedom of motion. The formation/decay of this TMPD radical cation is reversible. These results show that the positive charge in BT polymer generated by visible light is trapped by TMPD molecule which is coordinated to one of the Ti atoms to form TMPD^.+. Therefore, the counter charge, e^-, will be more stabilized in this polymer than in a neat BT polymer. The present material could be used as a light-to-electric energy conversion device.