Highly Stable Perylenediimide‐Based Self‐Assembled Monolayers Studied with Spectroelectrochemistry

Abstract

Perylenediimide (PDI)‐based self‐assembled monolayers (SAMs) have been studied by using quartz crystal microbalance, X‐ray photoelectron spectroscopy, cyclic voltammetry, and spectroelectrochemistry (SEC). The high stability of PDI‐based SAMs has allowed very low signals to be probed by using absorption and emission SEC and by extracting voltabsorptograms. The wavelengths are reported for the absorption maxima of the PDI, anion radical, and dianion species. In contrast, the magnitudes of the molar extinction coefficient of the reduced forms were not preserved in the SAM. The quenching of PDI fluorescence was confirmed on a gold substrate.

Absorption Spectroelectrochemistry on Mixed Perylenediimide‐Based Self‐Assembled Monolayers: Non‐Linear Dependence of Absorbance versus Surface Coverage

“…As expected, SAM of 1 exhibits two successive fully reversible one‐electron processes in negative direction, at −0.60 V and −0.75 V vs . AgNO 3 /Ag (Figure ).…”

“…According to references, the absorption bands close to 540, 640 and 755 nm are assigned to 1 , 1 2 − and 1 .− species, respectively. The position and the shape of optical bands were found independent of the surface coverage, suggesting that the molecular structure of electroactive species does not change over the successive dilutions.…”

“… Absorption spectroelectrochemical experiments on mixed SAMs in 0.1 M Bu 4 NPF 6 /CH 2 Cl 2 at 10 mV s −1 and 293 K. On the y axis (i. e., time in s), 0, 6 and 12 s correspond to the potentials −0.25 (first vertex), −1.05 (potential of reverse scan) and −0.25 V (second vertex) of the CVs in Figure 1 respectively. Note that the absorbance at a given potential was determined by comparison with a reference spectrum recorded at the equilibrium potential . A) Γ=1.45±0.06×10 −10 mol cm −2 , i. e., 96 % of the full steady‐state coverage.…”

“…The synthesis of the dialkyl disulfide perylenediimide (PDI) 1 (Scheme ) was previously described . We should take into account that the introduction of four chlorine atoms at the 1,6,7,12 positions of the bay region enforces a considerable twisting close to 35–37° of the PDI skeleton as a result of electrostatic repulsion and steric effects among the substituents …”

“…Two of our recent works have been dedicated to improve significantly resolution of absorption time‐resolved spectroelectrochemistry (A‐SEC) coupled to cyclic voltammetry on redox thiolate‐on‐gold. Drawing upon the benefits provided by the latest technological breakthroughs (i. e. high signal‐to‐noise ratio and high sampling rate of CCD detectors), we have demonstrated the possibility of monitoring very low absorbance variations of electroactive species (thiophene and perylenediimide) to extract voltabsorptograms of the corresponding SAMs.…”