Hole‐Transfer Dyads and Triads Based on Perylene Monoimide, Quaterthiophene, and Extended Tetrathiafulvalene

Abstract

Two families of dyad and triad systems based on perylene monoimide (PMI), quaterthiophene (QT), and 9,10-bis(1,3-dithiol-2-ylidene)-9,10-dihydroanthracene (extended tetrathiafulvalene, exTTF) molecular components have been designed and synthesized. The dyads (D1 and D2) are of the PMI-QT type and the triads (T1 and T2) of the PMI-QT-exTTF type. The two families differ in the saturated or unsaturated nature of the linker groups (ethynylene in D1 and T1, ethylene in D2 and T2) that bridge the molecular components. The dyads and triads have been characterized by electrochemical, photophysical, and computational methods. Both the experimental and the computational (DFT) results indicate that in the unsaturated systems strong intercomponent interactions lead to substantial perturbation of the properties of the subunits. In particular, in T1, delocalization is particularly effective between the QT and exTTF units, which would be better viewed combined as a single electronic subsystem. For the dyad systems, the photophysics observed following excitation of the PMI unit is solvent-dependent. In moderately polar solvents (dichloromethane, diethyl ether) fast charge separation is followed by recombination to the ground state. In toluene, slow conversion to the charge-separated state is followed by intersystem crossing and recombination to yield the triplet state of the PMI unit. The behavior of the triads, on the other hand, is remarkably similar to that of the corresponding dyads, which indicates that, after primary charge separation, hole shift from the oxidized QT component to exTTF is quite inefficient. This unexpected result has been rationalized on the basis of the anomalous (simultaneous two-electron oxidation) electrochemistry of exTTF and with the help of DFT calculations. In fact, although exTTF is electrochemically easier to oxidize than QT by around 0.6 V, the one-electron redox orbitals (HOMOs) of the two units in triad T2 are almost degenerate.

Light harvesting vesicular donor–acceptor scaffold limits the rate of charge recombination in the presence of an electron donor

“…5d. The three principal components obtained from SVD could be assigned as the following: (i) the radical anion of perylenimide (PIc À ) 48,68 and/or the radical cation of indole (Ic + ) centered at 597 nm with a lifetime of 2.1 ps; 72,73 (ii) the singlet excited state of perylenimide ( 1 PI*) 67,74 featured at 620 nm with a lifetime of 3.0 ns; and (iii) radical anion of p-p stacked perylenimide (p-p PIc À ) at 640 nm with a lifetime of 1.4 ns. 48 We observed a time-dependent shi in the peak corresponding to the decay of PIc À indicating the evolution of a radical anion of larger p-p stacks of perylenimide (Fig.…”

Effect of temperature on symmetry breaking excited state charge separation: restoration of symmetry at elevated temperature

“…The faster component corresponds to the radical anion of perylenimide (P À ) formed by the photoinduced symmetry breaking charge separation, while the slower component could be attributed to the decay of the singlet excited state. 15,25,26 A broad band was observed at around 730 nm which can be attributed to the local excited state (LES) absorption which decays monoexponentially with a lifetime of 475 ps.…”

Synthesis of Perylene Dyes with Multiple Triphenylamine Substituents

“…During the positive potential sweep, all dyes showed three reversible oxidation peaks, for which the first and second oxidation potentials were assigned to the oxidation of TPA 11d. The third oxidation peak may correspond to perylene core oxidation 13d. In the negative potential regime, only one characteristic reduction wave of the perylene moiety was observed 11a.…”