PHOTOINDUCED ELECTRON-TRANSFER IN DONOR-ACCEPTOR ARYL DYADS BASED ON N,N,N'N'-TETRAMETHYL-P-PHENYLENEDIAMINE AS THE DONOR

The solution-phase photophysics of several electron transfer donor-don or-acceptor assemblies (2 and 3) incorporating N,N,N',N'-tetramethyl-p -phenylenediamine (TMPD) derivatized with piperazyl, piperidyl, morpho linyl, and prolinyl groups in the 1- and 4-positions as donors and N,N -dimethyl-4-nitroaniline, anthraquinone, 3,5-dinitrobenzene, and 2,4-d initrobenzene as accepters are described. In measurements of the model compounds 1 incorporating only the donor moieties, flash photolysis g enerated the radical cation and triplet species of TMPD as evidenced b y the superposition of their transient absorption spectra. Lifetime me asurements reveal, as well, a delayed fluorescence derived from triple t-triplet annihilation. In 2 and 3, electron transfer from the lowest excited singlet state of TMPD to the various accepters was established by the following: (1) steady-state emission measurements where the fl uorescence of TMPD was drastically quenched by the acceptor, (2) the t ransient absorption spectra of the radical cation and radical anion of the donor and acceptor, and (3) a single-exponential decay profile in 2 and 3, superseding the biexponential decay observed in the model do nor.