Molecular design, characterization, and application of multi-information dyes for multi-dimensional optical chemical sensing. Molecular design concepts of the dyes and their fundamental spectral characteristics

Abstract

The molecular design of multi-functional dyes, called `multi-information dyes' (MIDs), and their application to several methods of optical chemical sensing were proposed. The concepts for the molecular design of the dyes were as follows: (1) the introduction of multiple (both positive and negative) charges on both ends of the large conjugated π-electron system of the dye molecule, so that the dye interacts with many chemical species or environments; (2) the introduction of different substitution (electron-donating or electron-accepting) groups in the conjugated π-electron system of the dye molecule, so that the dye has a different pK a and solvatochromic property; and (3) the introduction of an immobilization site in the dye molecule, so that the dye can be easily prepared as a sensing probe. Based on these concepts, sixteen kinds of dyes were synthesized, all being of the merocyanine type. The basic color-change characteristics of the MIDs were evaluated with a homogeneous system and a solvent extraction two-phase system. Some of these dyes (e.g., KD-M5) offered two-dimensional sensing information for sensing the water content in organic solvents, in which the absorbance maximum wavelength ( λ max) shift and absorbance change were both utilized as the detecting signals. From these results, the MIDs developed in this study have several possibilities for analytical applications in optical chemical sensing such as pH sensing, ion sensing, neutral molecule sensing, and water content-sensing in organic solvents.