Interaction of semicarbazide and thiosemicarbazide pyrene derivatives with anionic and cationic micelles: changed character of pyrene due to alteration in charge density induced by the side chains

Abstract

A semicarbazide and a thiosemicarbazide derivative of pyrene have been synthesized keeping in mind the pharmaceutical potentiality of the molecules. The molecules differ in structure only at the CO and the CS groups. The presence of the amine group in the vicinity of the O and the S atoms distributes the π-electrons in the pyrene differently making the pyrene moiety in the semicarbazide more hydrophobic than that in the thiosemicarbazide. Because of this different electron distribution in the ground state of the molecules, they interact variably with either cationic or anionic micelles. The compounds are found to attach to the cationic micelles at the surface through electrostatic interactions between the pyrene electrons and the surfactant head groups, varying in the strength of the binding. The exaggerated electron density towards the S counterpart in the thiosemicarbazide drives the molecule to move to the Stern layer, whereas, due to a greater electron cloud over the pyrene moiety of the semicarbazide it stays inside the palisade layer of the anionic micelle. We have used fluorescence spectroscopy to investigate the interactions. The different extents of the distribution of these medically potent compounds in biomimicking cationic and anionic micelles could further open up their biological applications.