A fast-switching optical filter using the photochromic properties of spirobenzopyranoindoline solutions

Ultrafast Dynamics of a Spiropyran in Water

“…The cleaved molecule either re-establishes the bond or undergoes an isomerization process toward a stable merocyanine isomer, which is characterized by a strong absorbance in the visible spectral range. The shift of the absorbance from the UV into the visible spectral range is explained by the planarity of the merocyanine molecule that allows the previously uncoupled π-systems of chromene and indoline to become extended across the entire structure. , In principle the merocyanine can exist in eight different isomers depending on the orientation of the three central C–C bonds, but only isomers with a trans configuration (MC-trans) around the central bond and a cis–cis–trans isomer (MC-CCT) have been found to be stable. − The large change in dipole moment, the strong change in geometry (from perpendicular to flat), and the excellent switching ratios make photochromic spiropyrans versatile tools for a wide variety of applications such as data storage, temperature measurement, and as a trigger for biological reactions. − …”

Control of optical properties through photochromism: a promising approach to photonics

“…This approach is appealing since it is self-adaptive according to the illumination degree and it does not require any energy consumption [56]. Spirobenzopyranoindoline has also been used in solution to produce fast filters with a very short reaction time [57] that can be used as active welding filters, where photochromic molecules convert to the colored form by absorbing the UV light emitted by the welding-arc radiation. The reaction time is less than 1 ms, fast enough for practical use.…”

Direct Photoreduction and Ketone-Sensitized Reduction of Nitrospirobenzopyranindolines by Aliphatic Amines

“…The photochromism of spiro[2 H -1-benzopyran-2,2′-indolines] and several 6-nitro-substituted derivatives (nitroS) has been intensively investigated. − For nitroS in polar solvents at ambient temperature an equilibrium is established between the ring-closed colorless (Sp) form and the most stable isomer of the strongly colored open merocyanine forms ( trans -M). The coloration of nitroS is strongly enhanced upon UV irradiation, − and this ring-opening photoprocess takes place in the picoseond range .…”

“…NitroS have a wide application potential. − The use of nitroS as a photochromic system is, however, limited by the reductive or oxidative photodamage involving free radicals. − For N2 in air-saturated toluene an oxidative photosplitting has been reported with 5-nitrovanillin as the major product of the nitrobenzene part and with 3,3-dimethyloxindol and 1,3,3-trimethyloxindol as the corresponding fragments. An increase of fatigue resistance has been found for a nitroS in aerated toluene in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO), and therefore, involvement of singlet molecular oxygen and a quenching reaction by DABCO have been considered .…”