Complexation of photochromic crown ether styryl dyes with Mg²⁺ as probed by surface-enhanced raman scattering spectroscopy

Complexation with magnesium cations of 2,3,5,6,8,9,11,12-octahydro-1,4,7,10,13-benzopentaoxacyclopentadecin (1), as well as derivatives of crown ether styryl dyes perchlorate 2-[2-(2,3,5,6,8,9,11,12-octahydro-1,4,7,10,13-benzopentaoxacyclopentadecin-16-yl)ethenyl]-3-ethylbenzothiazolium (2), betaine 2-[2-(2,3,5,6,8,9,11,12-octahydro-1,4,7,10,13-benzopentaoxacyclopentadecin-16-yl)ethenyl]-3-(3-sulfopropyl)benzothiazolium (3), betaine 2-[2-(2,3,5,6,8,9,11,12-octahydro-1,4,7,10,13-benzopentaoxacyclopentadecin-16-yl)ethenyl]-3-(3-sulfoethyl)benzothiazolium (4) was studied by surface-enhanced Raman scattering (SERS) spectroscopy. Comparative studies of isomerization and complexation of photochromic ionophores 2−4 with Mg2+ in solution and when adsorbed on the silver surface were performed. The aim was to characterize parameters of these processes depending on the nature (alkyl versus sulfo-alkyl) as well as the length (sulfoethyl versus sulfopropyl) of the N substituent in the benzothiazolium residue. The data...