Applications of Spiropyran Derivatives in Analytical Chemistry

Spiropyrans, an important class of photochromic compounds that undergo reversible structural isomerization between a colorless spiropyran form and a colored merocyanine, are an attractive starting point in constructions of molecular-level devices with molecular recognition function and signal transduction ability due to their unique molecule binding ability and signal transduction function. The merocyanine may interact with their environment (solvent or matrix) leading to different photochromic responses. By exploiting such characteristics, spiropyrans have been employed not only in materials chemistry for molecular switches, but also in analytical chemistry as molecular sensors. During the past decades, a number of receptors possessing diverse spiropyran skeletons have been designed and utilized for optical sensing of metal ions, some for neutral molecules, such as nucleobases, amino acids, peptide and DNA, and a few for anions. Some work has also been done in eletrochemical sensing using spiropyran-modified electrode. This review summarizes the progress in the study of spiropyran derivatives in analytical chemistry, including their application as spectroscopic sensors for metal ions, anions and organic molecules, and also the application of spiropyran in electrochemical immuno-sensor. Traditional spiropyran derivatives containing crown ether moieties or -NO2 group, and special kinds of spiropyrans like bis-spiropyran which is more super in binding selectivity, are discussed in detail.