Single Molecule Multiphotochromism with Diarylethenes

Abstract

In single photochromes, the two isomers that are interconverted in photoinduced reactions can serve as on and off states in a molecular switching device. The addition of several photochromic moieties onto a single molecule can allow the processing of more complex logical patterns. For example, an asymmetric triad could, in principle, store a byte, rather than a bit, of data. Because of the potential impact of multiphotochromic molecules in many research areas, over the past decade several groups have synthesized these coupled structures. The targets are easily addressable molecules that display increased contrast between the on and off states and in which all isomers have significantly distinguishable optical signatures. In this Account, we provide an overview of the multiswitchable molecular systems that incorporate at least one diarylethene group, which is the most successful thermally stable (P-type) organic photochrome. Up to this point, most systems have presented significant limitations. First of all, the reversibility of the processes is hindered by several side reactions more frequently than for single photochromes. Second, switching one part of the compound impedes the photoreactivity of other fragments in approximately 50% of the cases, and maximizing the electronic communication increases the probability of partial activity. In addition, most of the few synthesized operative systems only demonstrate cumulative absorption spectra rather than new features. Finally, it is impossible to selectively induce a chosen conversion because one wavelength might trigger several processes. We also emphasize the promising successes of asymmetric diarylethene dimers and trimers and molecules that combine two families of photochromes, such as diarylethene added to fulgimide or phenoxy-naphthacenequinone. In that framework, theoretical simulations offer complementary tools to investigate these structures, both to obtain structure/property relationships and to propose paths for the design of more efficient molecules. However, due to the size of the systems, researchers can only apply semiquantitative models. The investigation of the absorption spectra of the photochromes with time-dependent density functional theory (TD-DFT), the analysis of the topology of the LUMO + n (typically n = 1) of the closed-open hybrid, and an estimate of the steric stress in the hypothetical (ground-state) closed-closed structure serve as a useful combination of parameters to obtain initial insights regarding the photocyclization of the different open diarylethene groups. Nevertheless, because a first-order qualitative approach does not explore the potential energy surface of the photoexcited states, it remains inadequate for the investigation of some molecules.

A new multi-addressable molecular switch based on a photochromic diarylethene with a 6-aryl[1,2-c]quinazoline unit

“…In our previous work, we reported a multiple responsive diarylethene with a salicylaldehyde Schiff base unit and found that its fluorescence could be simultaneously modulated by light, proton, and metal ions [14]. These achievements have contributed to a broad understanding of the multi-addressable fluorescence switching based on diarylethenes with various functional groups [15]. More potential applications in sensing, labeling, and high density information process has urged chemists to develop simple and efficient multi-addressable switching systems.…”

Reversible Photomodulation of Electronic Communication in a π‐Conjugated Photoswitch‐Fluorophore Molecular Dyad

“…[7] Herein, we report the novel BODIPY-DAE dyad 1,i ncluding its synthesis and photophysicala nd photochemical properties, including both stationarya nd transients pectroscopic characterization.O ur results are relevant for the design of molecular systemst hat enable photocontrol of fluorescence without involvinge nergy transfer whilea tt he same time providing ad eeper understanding of electronic coupling in photochromic molecular dyads. [20,27] Results and Discussion…”

Photochromic Diarylethenes with Heterocyclic Aromatic Rings: Correlation between Thermal Bistability and Geometrical Characters of Transition States

“…[34][35][36][37][38][39] Time-dependent (TD) DFT calculations have also been employed to investigate multiphotochromism in a single photochromic molecule. [40][41][42][43][44] Noteworthy, Patel and Masunov have reported that DFT calculations are able to reproduce the reaction barriers of the ground-state ring-opening processes of several photochromic diarylethene compounds within a mean absolute error of around 3 kcal mol -1 , provided that the diradical character of the transition state is properly described by an open-shell singlet state. 45 Chu and coworkers also reported DFT and TD-DFT study on the ground-state and excited-state potential energy surfaces.…”