Synthesis of amphiphilic photochromic benzo-15(18)-crown-5(6) ethers and their study in monolayers

New amphiphilic photochromic benzo-15(18)-crown-5(6) ethers (APC) differing in the position of the octadecyl substituent and the size of the crown cav ity were synthesized. The compounds form stable monolayers in the air/water and air/alkaline metal salt solution interfaces. The results of the pressu re isotherm measurements, atomic force microscopy (AFM), and electronic spe ctroscopy show that the structure of the monolayers formed depends on the s tructure of the parent APC and the nature of the cation in salt solutions. The area per molecule of APC in the monolayer (specific area) is the smalle st on the water surface and increases by 20-40% on the aqueous subphase sur face with an increasing concentration of salts therein to indicate the form ation of APC complexes with the metal cations. When the hydrophobic aliphat ic substituent is displaced from position 3 to position 5 of the benzothiaz ole ring, the specific area on the surface of water and subphases decreases twofold, which indicates the compactization of the monolayer on this modif ication, A reversible E-Z-photoisomerization of APC was found in the monola yers formed in the salt solution/air interface. The features of the reactio n are defined by the specific organization of the amphiphilic molecules in the monolayer and by the nature of the cation.