Spatially Close Azo Dyes with Sub‐Nanosecond Switching Speeds and Exceptional Temporal Resolution

Abstract

Photoswitchable bis-azo dyes with an outstanding temporal resolution of 10(15) times between the thermal relaxation rates of their two constituting photochromes are reported. Remarkably, the close spatial proximity of both azo photochromes in these molecular assemblies translates in an unprecedented 10(3) -fold acceleration of the thermal isomerization rate of their faster azo unit compared to the one displayed by the isolated counterpart. Indeed, the relaxation time of the fast-isomerizing platform of the herein reported bis-azobenzenes is as low as 200 ps under ambient conditions. In the wake of these results, the bis-azo dyes described herein are invaluable chromophores for the design of multifunctional light-addressable materials in which simultaneous switching in two very different timescales might be essential.

Picosecond Switchable Azo Dyes

“…[21] Indeed, we have reported recently aw hole family of hydroxy-and amino-azopyridinium saltst hat show thermalr elaxation timesw ithin the milli-, micro-a nd nanosecond temporal domain under ambient conditions( Figure 1, structure 5 as ar epresentative structure). [22][23][24][25][26][27][28][29][30][31] Very recently,aphenylazoindole derivative hasb een introducedw ith aw ater-assisted thermali somerization rate in the nanosecondr ange. [32] However,i ncreasing the isomerization rate of azobenzenes sufficiently to occur within the picosecond timescale still remains ac hallenge.…”

“…[32] However,i ncreasing the isomerization rate of azobenzenes sufficiently to occur within the picosecond timescale still remains ac hallenge. The design scheme presented here involves the replacement of the pyridinium electronwithdrawing moiety of our azo chromophores [22][23][24][25][26][27][28][29][30][31] by its more powerful benzothiazoliuma nd thiazolium counterparts, in the shape of azo dyes 3 and 4 ( Figure 1). In this article, we report on the synthesis and the photoinduced and thermali somerization of these novel azo derivatives, which are characterized with subpicosecond time-resolved spectroscopya nd ab initio calculations.…”

“…Azo dyes that combine a strong push–pull configuration with the capability to establish an azo/hydrazone tautomeric equilibrium are promising chromophores for this purpose because they are endowed with fast thermal cis ‐to‐ trans isomerization kinetics at room temperature . Indeed, we have reported recently a whole family of hydroxy‐ and amino‐azopyridinium salts that show thermal relaxation times within the milli‐, micro‐ and nanosecond temporal domain under ambient conditions (Figure , structure 5 as a representative structure) . Very recently, a phenylazoindole derivative has been introduced with a water‐assisted thermal isomerization rate in the nanosecond range .…”

Synthesis and Photophysical Characterization of Azoheteroarenes

“…Potential future applications of this class of photoswitches include also optically controlled (bio-) materials and information/data processing to mention a few . Of particular interest for the latter are compounds displaying very fast thermal Z → E isomerization, allowing for ultrafast data transmission …”

“…16 Of particular interest for the latter are compounds displaying very fast thermal Z → E isomerization, allowing for ultrafast data transmission. 17 Nitrogen heterocycles are among the most significant structural components of pharmaceuticals. 18 Therefore, in order to integrate the azobenzene-based molecular photoswitches into the pharmacophore of small drug-like molecules, e.g., kinase inhibitors, the development of heterocyclic azobenzene derivatives are fundamental.…”