Photoinduced Electron Transfer in Donor−Acceptor Aryl Dyads Based on N,N,N‘,N‘-Tetramethyl-p-phenylenediamine as the Donor

Abstract

The solution-phase photophysics of several electron transfer donor−donor−acceptor assemblies (2 and 3) incorporating N,N,N‘,N‘-tetramethyl-p-phenylenediamine (TMPD) derivatized with piperazyl, piperidyl, morpholinyl, and prolinyl groups in the 1- and 4-positions as donors and N,N-dimethyl-4-nitroaniline, anthraquinone, 3,5-dinitrobenzene, and 2,4-dinitrobenzene as acceptors are described. In measurements of the model compounds 1 incorporating only the donor moieties, flash photolysis generated the radical cation and triplet species of TMPD as evidenced by the superposition of their transient absorption spectra. Lifetime measurements reveal, as well, a delayed fluorescence derived from triplet−triplet annihilation. In 2 and 3, electron transfer from the lowest excited singlet state of TMPD to the various acceptors was established by the following: (1) steady-state emission measurements where the fluorescence of TMPD was drastically quenched by the acceptor, (2) the transient 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 donor.

A Molecular Tetrad That Generates a High-Energy Charge-Separated State by Mimicking the Photosynthetic Z-Scheme

“…For this purpose, we designed the tetrad molecule Bodipy–NDI–TAPD–Ru (Figure ), composed of two different dyesthe organic dye 4,4-difluoro-1,3,5,7-tetramethyl-2,6-diethyl-4-bora-3a,4a-diaza- s -indacene (Bodipy) and a Ru II (bipyridine) 3 derivative which harvest light in a complementary manner between 400 and 600 nm. The naphthalene diimide (NDI) unit is a good electron acceptor, while the tetraalkylphenyldiamine (TAPD) unit is a good electron donor . The ultimate charge-separated state produced by two-photon excitation is where Bodipy is oxidized and Ru is reduced.…”

“…The naphthalene diimide (NDI) 16 unit is a good electron acceptor, while the tetraalkylphenyldiamine (TAPD) unit is a good electron donor. 17 The ultimate charge-separated state produced by two-photon excitation is where Bodipy is oxidized and Ru is reduced. We report herein the unique property of a molecular tetrad in which two coupled photoinduced electron transfer events derived from two consecutive photon absorptions produce a long-lived chargeseparated state composed of both a strong oxidant and reductant (Figure 7).…”

Pattern recognition based identification of nitrated explosives

“…Studies have shown that TNT forms complexes with strong electron donors. 31 In our study, we noticed that TNT (obtained as MeCN solution) formed an interaction with TMPD, a strong donor, 13 and we observed this by appearance of a new band in the absorption spectrum. The appearance of the new band indicates the formation of CT complexes.…”

“…In particular TMPD and TDAE, among various amine compounds, have received considerable attention because of their CT photoionization process. [9][10][11][12][13][14] The absorption properties of intermolecular CT transitions, and the association behavior of the complexes, depend on the ionization potential of the donor. TMPD and TDAE have low ionization potential, thereby acting as powerful electron donors.…”

Preparation of Donor-σ-Acceptor Molecules Using Arene−Ruthenium Chemistry

“…Recently, we have described methodology 6 for the preparation of TAPD derivatives by using arene−iron chemistry, and several D-σ-A molecules have been synthesized that show photoinduced electron-transfer character . We are interested in preparing and studying such D-σ-A molecules in self-assembled monolayers (SAMs) on Au electrode to investigate their electrochemical properties, an area that has so far received little attention …”