Negative Photochromism and Luminescent Properties of Amphiphilic Spiropyran in Solutions and at the Interface

The work presents the results of a study of the negative photochromism and luminescent properties of 1',3'-dihydro-3',3'-dimethyl-6-nitro-1'-octadecyl-[1-benzopyran-2,2'-indole]-8-methyl pyridinium chloride (SP2) in solutions, Langmuir monolayers, and cast films. It has been demonstrated that the introduction of the pyridine substituent into the chromene part of the amphiphilic spiropyran leads to stabilization of the open form of the compound under dark conditions, both in the dissolved and in the ordered planar state. The kinetic characteristics of photoreactions occurring in organic solvents upon irradiation by visible light and during relaxation in darkness are determined. Negative solvatochromism of SP2, which consists in the hypsochromic shift of the maximum absorption of the merocyanine form of the compound upon increase of the solvent polarity, is revealed. The luminescent properties of solutions of negative spiropyran and its cast films are investigated. For the first time, SP2 monolayers are formed at the air/water interface and their properties are studied. It is established that SP2 retains its photochromic properties upon transition from solutions to a two-dimensional condensed state. The results obtained open up broad prospects for the development of switchable optoelectronic and information systems based on negative spiropyrans.