Mechanistic Insights into the Photochromism of trans-10b,10c-Dimethyl-10b,10c-dihydropyrene Derivatives

Abstract

A series of dimethyldihydropyrene derivatives was studied to elucidate the photochemical mechanism associated with the switching between the dimethyldihydropyrene (DHP, closed) and metacyclophanediene (CPD, open) forms of the molecule. Quantum yields of ring opening and closure, fluorescence quantum yields and lifetimes, as well as laser flash photolysis studies were performed to establish the effect of substituents on the switching efficiency. Ring opening of the DHPs occurs from the first singlet excited state. The low quantum yields for the ring opening reaction observed (< or =0.042) are a consequence of the low rate constant (< or =1.7 x 10(7) s(-1)) for this process. The quantum yields for ring closure of the CPD were determined for select compounds and were of the order of 0.1-0.4. These results show that the efficiency for ring opening of this class of compounds is intrinsically low, but can be modulated to some extent by the introduction of substituents. These properties should be taken into account when considering what type of photoswitching devices DHPs might be useful for.

Switching properties of Li–benzene complexes in a uniform electric field: a case where a “small” change makes a big difference

“…Its main concern unlike the papers mentioned above, was for systems of technological importance and for biological structures. 12,13,21 These, and other molecular electronic devices, however, will probably be replaced by robust crystalline extended devices. Such switches have been found among those that react to the chemical environment or light.…”

Electric field control of proton-transfer molecular switching: molecular dynamics study on salicylidene aniline

“…[31][32][33][34][35][36][37][38] Combining results of the static and dynamic studies on the switching properties of the SA molecule exposed to an external electric field, we formulate the following conclusions: Having a direct look on the trajectories calculated in dynamic simulations, we found that for low electric field values (E = 0.01 a.u.…”

Fluorescent Switches Based on Photochromic Compounds

“…[12] In this instance, however, the photogenerated isomer is thermally stable and reverts to the original and colorless state only after visible irradiation with a quantum yield of 0.015. Other common photochromic compounds based on ring opening and closing steps are the dihydroazulenes (e.g., 3a in Figure 1), [13] the spiroindolizines (e.g., 4a), [14,15] the dihydropyrans (e.g., 5a) [16] and the fulgides (e.g., 6a). [17] In alternative to ring opening and closing reactions, photoinduced cis/trans isomerizations can also be exploited to implement photochromic transformations.…”

“…Similarly, the spiroindolizine 4a and the dihydropyran 5a are fluorescent, while their photogenerated isomers 4b and 5b are not. [14][15][16] Thus, the photoinduced and reversible interconversion of these four pairs of isomers results in the modulation of their fluorescence intensity.…”