On the design of a versatile ionic liquid, AOBH-DEHP, which can be used as a new molecular probe to investigate supramolecular assemblies

Abstract

The motivation of our work is to find an exciting new molecular probe, which has the advantages that contains the acridine orange moiety but also has an ample range of solubility in different media. The probe is obtained through the acid-base reaction between acridine orange base (AOB) and bis-(2-ethylhexyl) phosphoric acid (HDEHP) giving AOBH-DEHP. This synthesized dye results to be a protic ionic liquid, since it is a viscous liquid at room temperature and, it is only constituted by ions. The spectroscopic behavior of AOBH-DEHP in homogeneous medium, using water, benzene and n-heptane as solvents and, in benzene or n-heptane/sodium 1,4-bis-2-ethylhexylsulfosuccinate (AOT)/water reverse micelles (RMs) has been investigated. Absorption, emission and single photon counting techniques, were used to fully characterize the new molecule in different environments. It is shown that AOBH-DEHP has all the advantages of its chromophore, AOBH+ but, the presence of the hydrophobic anion, DEHP−, gives to the dye, unique solubility in solvents of very different polarities. As such and, in contrast to AOBH+ chloride salts, AOBH-DEHP can be used to determine different properties, such as micropolarity, restricted motion environment, critical micellar concentration in different RMs media.