Stability and reaction dynamics of trifluorinated indolylfulgides

The ultrafast reactions in the photochromic cycle of water-soluble fulgimide photoswitches

High polarity and protic nature of the solvent strongly influence the reaction dynamics of a photochromic water-soluble indolylfulgimide.

Ultrafast coherent oscillations reveal a reactive mode in the ring-opening reaction of fulgides

Ultrafast coherent dynamics reveals a low frequency vibrational mode governing the photochromic ring-opening reaction in indolylfulgide molecular switches.

Photochromic properties of a water-soluble methyl carboxylic acid indolylfulgimide

Photochromic fulgides and fulgimides have been identified as promising materials for applications in optical memory media, optical switches, and sensors. For applications in humid environments or biological systems, hydrolytic stability is crucial. A new photochromic methyl carboxylic acid indolylfulgimide was synthesized to improve hydrolytic stability in aqueous solution. The UV-vis spectra, extinction coefficient, thermal stability, and photochemical stability of the fulgimide were characterized in 50 mM sodium phosphate buffer (pH 7.4). The open and closed forms were both stable in buffer. At 37 °C after 500 h, the open forms of the fulgimide showed no degradation within experimental error (1-2%) by (1)H NMR and 2.3% decomposition by UV-vis spectroscopy. The closed form degraded 22% and 11% after 500 h at 37 °C in buffer by UV-vis and (1)H NMR data, respectively. In addition, the fulgimide cycled back and forth between the open and closed forms 80 times before degrading by 20% in buffer. The methyl group at the bridging position of the fulgimide significantly increased the thermal stability by overcoming the rapid hydrolysis of the trifluoromethyl group.

Increasing the efficiency of the ring-opening reaction of photochromic indolylfulgides by optical pre-excitation

For three indolylfulgides the quantum efficiency of the ring-opening reaction upon pre-excitation is investigated in a multipulse experiment. The quantum efficiency grows by factor of up to 3.4, when the pre-excitation pulse immediately precedes the excitation process. The change in quantum efficiency after pre-excitation is discussed as a function of reaction time, steady-state quantum efficiency and energetic barriers in the excited electronic state. The observed differences can be explained by the molecular properties of the investigated indolylfulgides.